TOMOYO Linux Cross Reference
Linux/kernel/cgroup/cpuset.c

   /*
    *  kernel/cpuset.c
    *
    *  Processor and Memory placement constraints for sets of tasks.
    *
    *  Copyright (C) 2003 BULL SA.
    *  Copyright (C) 2004-2007 Silicon Graphics, Inc.
    *  Copyright (C) 2006 Google, Inc
    *
   *  Portions derived from Patrick Mochel's sysfs code.
   *  sysfs is Copyright (c) 2001-3 Patrick Mochel
   *
   *  2003-10-10 Written by Simon Derr.
   *  2003-10-22 Updates by Stephen Hemminger.
   *  2004 May-July Rework by Paul Jackson.
   *  2006 Rework by Paul Menage to use generic cgroups
   *  2008 Rework of the scheduler domains and CPU hotplug handling
   *       by Max Krasnyansky
   *
   *  This file is subject to the terms and conditions of the GNU General Public
   *  License.  See the file COPYING in the main directory of the Linux
   *  distribution for more details.
   */
  #include "cgroup-internal.h"
  
  #include <linux/cpu.h>
  #include <linux/cpumask.h>
  #include <linux/cpuset.h>
  #include <linux/delay.h>
  #include <linux/init.h>
  #include <linux/interrupt.h>
  #include <linux/kernel.h>
  #include <linux/mempolicy.h>
  #include <linux/mm.h>
  #include <linux/memory.h>
  #include <linux/export.h>
  #include <linux/rcupdate.h>
  #include <linux/sched.h>
  #include <linux/sched/deadline.h>
  #include <linux/sched/mm.h>
  #include <linux/sched/task.h>
  #include <linux/security.h>
  #include <linux/spinlock.h>
  #include <linux/oom.h>
  #include <linux/sched/isolation.h>
  #include <linux/cgroup.h>
  #include <linux/wait.h>
  #include <linux/workqueue.h>
  
  DEFINE_STATIC_KEY_FALSE(cpusets_pre_enable_key);
  DEFINE_STATIC_KEY_FALSE(cpusets_enabled_key);
  
  /*
   * There could be abnormal cpuset configurations for cpu or memory
   * node binding, add this key to provide a quick low-cost judgment
   * of the situation.
   */
  DEFINE_STATIC_KEY_FALSE(cpusets_insane_config_key);
  
  /* See "Frequency meter" comments, below. */
  
  struct fmeter {
          int cnt;                /* unprocessed events count */
          int val;                /* most recent output value */
          time64_t time;          /* clock (secs) when val computed */
          spinlock_t lock;        /* guards read or write of above */
  };
  
  /*
   * Invalid partition error code
   */
  enum prs_errcode {
          PERR_NONE = 0,
          PERR_INVCPUS,
          PERR_INVPARENT,
          PERR_NOTPART,
          PERR_NOTEXCL,
          PERR_NOCPUS,
          PERR_HOTPLUG,
          PERR_CPUSEMPTY,
          PERR_HKEEPING,
  };
  
  static const char * const perr_strings[] = {
          [PERR_INVCPUS]   = "Invalid cpu list in cpuset.cpus.exclusive",
          [PERR_INVPARENT] = "Parent is an invalid partition root",
          [PERR_NOTPART]   = "Parent is not a partition root",
          [PERR_NOTEXCL]   = "Cpu list in cpuset.cpus not exclusive",
          [PERR_NOCPUS]    = "Parent unable to distribute cpu downstream",
          [PERR_HOTPLUG]   = "No cpu available due to hotplug",
          [PERR_CPUSEMPTY] = "cpuset.cpus and cpuset.cpus.exclusive are empty",
          [PERR_HKEEPING]  = "partition config conflicts with housekeeping setup",
  };
  
  struct cpuset {
          struct cgroup_subsys_state css;
  
          unsigned long flags;            /* "unsigned long" so bitops work */
  
         /*
          * On default hierarchy:
          *
          * The user-configured masks can only be changed by writing to
          * cpuset.cpus and cpuset.mems, and won't be limited by the
          * parent masks.
          *
          * The effective masks is the real masks that apply to the tasks
          * in the cpuset. They may be changed if the configured masks are
          * changed or hotplug happens.
          *
          * effective_mask == configured_mask & parent's effective_mask,
          * and if it ends up empty, it will inherit the parent's mask.
          *
          *
          * On legacy hierarchy:
          *
          * The user-configured masks are always the same with effective masks.
          */
 
         /* user-configured CPUs and Memory Nodes allow to tasks */
         cpumask_var_t cpus_allowed;
         nodemask_t mems_allowed;
 
         /* effective CPUs and Memory Nodes allow to tasks */
         cpumask_var_t effective_cpus;
         nodemask_t effective_mems;
 
         /*
          * Exclusive CPUs dedicated to current cgroup (default hierarchy only)
          *
          * The effective_cpus of a valid partition root comes solely from its
          * effective_xcpus and some of the effective_xcpus may be distributed
          * to sub-partitions below & hence excluded from its effective_cpus.
          * For a valid partition root, its effective_cpus have no relationship
          * with cpus_allowed unless its exclusive_cpus isn't set.
          *
          * This value will only be set if either exclusive_cpus is set or
          * when this cpuset becomes a local partition root.
          */
         cpumask_var_t effective_xcpus;
 
         /*
          * Exclusive CPUs as requested by the user (default hierarchy only)
          *
          * Its value is independent of cpus_allowed and designates the set of
          * CPUs that can be granted to the current cpuset or its children when
          * it becomes a valid partition root. The effective set of exclusive
          * CPUs granted (effective_xcpus) depends on whether those exclusive
          * CPUs are passed down by its ancestors and not yet taken up by
          * another sibling partition root along the way.
          *
          * If its value isn't set, it defaults to cpus_allowed.
          */
         cpumask_var_t exclusive_cpus;
 
         /*
          * This is old Memory Nodes tasks took on.
          *
          * - top_cpuset.old_mems_allowed is initialized to mems_allowed.
          * - A new cpuset's old_mems_allowed is initialized when some
          *   task is moved into it.
          * - old_mems_allowed is used in cpuset_migrate_mm() when we change
          *   cpuset.mems_allowed and have tasks' nodemask updated, and
          *   then old_mems_allowed is updated to mems_allowed.
          */
         nodemask_t old_mems_allowed;
 
         struct fmeter fmeter;           /* memory_pressure filter */
 
         /*
          * Tasks are being attached to this cpuset.  Used to prevent
          * zeroing cpus/mems_allowed between ->can_attach() and ->attach().
          */
         int attach_in_progress;
 
         /* partition number for rebuild_sched_domains() */
         int pn;
 
         /* for custom sched domain */
         int relax_domain_level;
 
         /* number of valid local child partitions */
         int nr_subparts;
 
         /* partition root state */
         int partition_root_state;
 
         /*
          * Default hierarchy only:
          * use_parent_ecpus - set if using parent's effective_cpus
          * child_ecpus_count - # of children with use_parent_ecpus set
          */
         int use_parent_ecpus;
         int child_ecpus_count;
 
         /*
          * number of SCHED_DEADLINE tasks attached to this cpuset, so that we
          * know when to rebuild associated root domain bandwidth information.
          */
         int nr_deadline_tasks;
         int nr_migrate_dl_tasks;
         u64 sum_migrate_dl_bw;
 
         /* Invalid partition error code, not lock protected */
         enum prs_errcode prs_err;
 
         /* Handle for cpuset.cpus.partition */
         struct cgroup_file partition_file;
 
         /* Remote partition silbling list anchored at remote_children */
         struct list_head remote_sibling;
 };
 
 /*
  * Legacy hierarchy call to cgroup_transfer_tasks() is handled asynchrously
  */
 struct cpuset_remove_tasks_struct {
         struct work_struct work;
         struct cpuset *cs;
 };
 
 /*
  * Exclusive CPUs distributed out to sub-partitions of top_cpuset
  */
 static cpumask_var_t    subpartitions_cpus;
 
 /*
  * Exclusive CPUs in isolated partitions
  */
 static cpumask_var_t    isolated_cpus;
 
 /* List of remote partition root children */
 static struct list_head remote_children;
 
 /*
  * Partition root states:
  *
  *   0 - member (not a partition root)
  *   1 - partition root
  *   2 - partition root without load balancing (isolated)
  *  -1 - invalid partition root
  *  -2 - invalid isolated partition root
  *
  *  There are 2 types of partitions - local or remote. Local partitions are
  *  those whose parents are partition root themselves. Setting of
  *  cpuset.cpus.exclusive are optional in setting up local partitions.
  *  Remote partitions are those whose parents are not partition roots. Passing
  *  down exclusive CPUs by setting cpuset.cpus.exclusive along its ancestor
  *  nodes are mandatory in creating a remote partition.
  *
  *  For simplicity, a local partition can be created under a local or remote
  *  partition but a remote partition cannot have any partition root in its
  *  ancestor chain except the cgroup root.
  */
 #define PRS_MEMBER              0
 #define PRS_ROOT                1
 #define PRS_ISOLATED            2
 #define PRS_INVALID_ROOT        -1
 #define PRS_INVALID_ISOLATED    -2
 
 static inline bool is_prs_invalid(int prs_state)
 {
         return prs_state < 0;
 }
 
 /*
  * Temporary cpumasks for working with partitions that are passed among
  * functions to avoid memory allocation in inner functions.
  */
 struct tmpmasks {
         cpumask_var_t addmask, delmask; /* For partition root */
         cpumask_var_t new_cpus;         /* For update_cpumasks_hier() */
 };
 
 static inline struct cpuset *css_cs(struct cgroup_subsys_state *css)
 {
         return css ? container_of(css, struct cpuset, css) : NULL;
 }
 
 /* Retrieve the cpuset for a task */
 static inline struct cpuset *task_cs(struct task_struct *task)
 {
         return css_cs(task_css(task, cpuset_cgrp_id));
 }
 
 static inline struct cpuset *parent_cs(struct cpuset *cs)
 {
         return css_cs(cs->css.parent);
 }
 
 void inc_dl_tasks_cs(struct task_struct *p)
 {
         struct cpuset *cs = task_cs(p);
 
         cs->nr_deadline_tasks++;
 }
 
 void dec_dl_tasks_cs(struct task_struct *p)
 {
         struct cpuset *cs = task_cs(p);
 
         cs->nr_deadline_tasks--;
 }
 
 /* bits in struct cpuset flags field */
 typedef enum {
         CS_ONLINE,
         CS_CPU_EXCLUSIVE,
         CS_MEM_EXCLUSIVE,
         CS_MEM_HARDWALL,
         CS_MEMORY_MIGRATE,
         CS_SCHED_LOAD_BALANCE,
         CS_SPREAD_PAGE,
         CS_SPREAD_SLAB,
 } cpuset_flagbits_t;
 
 /* convenient tests for these bits */
 static inline bool is_cpuset_online(struct cpuset *cs)
 {
         return test_bit(CS_ONLINE, &cs->flags) && !css_is_dying(&cs->css);
 }
 
 static inline int is_cpu_exclusive(const struct cpuset *cs)
 {
         return test_bit(CS_CPU_EXCLUSIVE, &cs->flags);
 }
 
 static inline int is_mem_exclusive(const struct cpuset *cs)
 {
         return test_bit(CS_MEM_EXCLUSIVE, &cs->flags);
 }
 
 static inline int is_mem_hardwall(const struct cpuset *cs)
 {
         return test_bit(CS_MEM_HARDWALL, &cs->flags);
 }
 
 static inline int is_sched_load_balance(const struct cpuset *cs)
 {
         return test_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
 }
 
 static inline int is_memory_migrate(const struct cpuset *cs)
 {
         return test_bit(CS_MEMORY_MIGRATE, &cs->flags);
 }
 
 static inline int is_spread_page(const struct cpuset *cs)
 {
         return test_bit(CS_SPREAD_PAGE, &cs->flags);
 }
 
 static inline int is_spread_slab(const struct cpuset *cs)
 {
         return test_bit(CS_SPREAD_SLAB, &cs->flags);
 }
 
 static inline int is_partition_valid(const struct cpuset *cs)
 {
         return cs->partition_root_state > 0;
 }
 
 static inline int is_partition_invalid(const struct cpuset *cs)
 {
         return cs->partition_root_state < 0;
 }
 
 /*
  * Callers should hold callback_lock to modify partition_root_state.
  */
 static inline void make_partition_invalid(struct cpuset *cs)
 {
         if (cs->partition_root_state > 0)
                 cs->partition_root_state = -cs->partition_root_state;
 }
 
 /*
  * Send notification event of whenever partition_root_state changes.
  */
 static inline void notify_partition_change(struct cpuset *cs, int old_prs)
 {
         if (old_prs == cs->partition_root_state)
                 return;
         cgroup_file_notify(&cs->partition_file);
 
         /* Reset prs_err if not invalid */
         if (is_partition_valid(cs))
                 WRITE_ONCE(cs->prs_err, PERR_NONE);
 }
 
 static struct cpuset top_cpuset = {
         .flags = BIT(CS_ONLINE) | BIT(CS_CPU_EXCLUSIVE) |
                  BIT(CS_MEM_EXCLUSIVE) | BIT(CS_SCHED_LOAD_BALANCE),
         .partition_root_state = PRS_ROOT,
         .relax_domain_level = -1,
         .remote_sibling = LIST_HEAD_INIT(top_cpuset.remote_sibling),
 };
 
 /**
  * cpuset_for_each_child - traverse online children of a cpuset
  * @child_cs: loop cursor pointing to the current child
  * @pos_css: used for iteration
  * @parent_cs: target cpuset to walk children of
  *
  * Walk @child_cs through the online children of @parent_cs.  Must be used
  * with RCU read locked.
  */
 #define cpuset_for_each_child(child_cs, pos_css, parent_cs)             \
         css_for_each_child((pos_css), &(parent_cs)->css)                \
                 if (is_cpuset_online(((child_cs) = css_cs((pos_css)))))
 
 /**
  * cpuset_for_each_descendant_pre - pre-order walk of a cpuset's descendants
  * @des_cs: loop cursor pointing to the current descendant
  * @pos_css: used for iteration
  * @root_cs: target cpuset to walk ancestor of
  *
  * Walk @des_cs through the online descendants of @root_cs.  Must be used
  * with RCU read locked.  The caller may modify @pos_css by calling
  * css_rightmost_descendant() to skip subtree.  @root_cs is included in the
  * iteration and the first node to be visited.
  */
 #define cpuset_for_each_descendant_pre(des_cs, pos_css, root_cs)        \
         css_for_each_descendant_pre((pos_css), &(root_cs)->css)         \
                 if (is_cpuset_online(((des_cs) = css_cs((pos_css)))))
 
 /*
  * There are two global locks guarding cpuset structures - cpuset_mutex and
  * callback_lock. We also require taking task_lock() when dereferencing a
  * task's cpuset pointer. See "The task_lock() exception", at the end of this
  * comment.  The cpuset code uses only cpuset_mutex. Other kernel subsystems
  * can use cpuset_lock()/cpuset_unlock() to prevent change to cpuset
  * structures. Note that cpuset_mutex needs to be a mutex as it is used in
  * paths that rely on priority inheritance (e.g. scheduler - on RT) for
  * correctness.
  *
  * A task must hold both locks to modify cpusets.  If a task holds
  * cpuset_mutex, it blocks others, ensuring that it is the only task able to
  * also acquire callback_lock and be able to modify cpusets.  It can perform
  * various checks on the cpuset structure first, knowing nothing will change.
  * It can also allocate memory while just holding cpuset_mutex.  While it is
  * performing these checks, various callback routines can briefly acquire
  * callback_lock to query cpusets.  Once it is ready to make the changes, it
  * takes callback_lock, blocking everyone else.
  *
  * Calls to the kernel memory allocator can not be made while holding
  * callback_lock, as that would risk double tripping on callback_lock
  * from one of the callbacks into the cpuset code from within
  * __alloc_pages().
  *
  * If a task is only holding callback_lock, then it has read-only
  * access to cpusets.
  *
  * Now, the task_struct fields mems_allowed and mempolicy may be changed
  * by other task, we use alloc_lock in the task_struct fields to protect
  * them.
  *
  * The cpuset_common_seq_show() handlers only hold callback_lock across
  * small pieces of code, such as when reading out possibly multi-word
  * cpumasks and nodemasks.
  *
  * Accessing a task's cpuset should be done in accordance with the
  * guidelines for accessing subsystem state in kernel/cgroup.c
  */
 
 static DEFINE_MUTEX(cpuset_mutex);
 
 void cpuset_lock(void)
 {
         mutex_lock(&cpuset_mutex);
 }
 
 void cpuset_unlock(void)
 {
         mutex_unlock(&cpuset_mutex);
 }
 
 static DEFINE_SPINLOCK(callback_lock);
 
 static struct workqueue_struct *cpuset_migrate_mm_wq;
 
 static DECLARE_WAIT_QUEUE_HEAD(cpuset_attach_wq);
 
 static inline void check_insane_mems_config(nodemask_t *nodes)
 {
         if (!cpusets_insane_config() &&
                 movable_only_nodes(nodes)) {
                 static_branch_enable(&cpusets_insane_config_key);
                 pr_info("Unsupported (movable nodes only) cpuset configuration detected (nmask=%*pbl)!\n"
                         "Cpuset allocations might fail even with a lot of memory available.\n",
                         nodemask_pr_args(nodes));
         }
 }
 
 /*
  * Cgroup v2 behavior is used on the "cpus" and "mems" control files when
  * on default hierarchy or when the cpuset_v2_mode flag is set by mounting
  * the v1 cpuset cgroup filesystem with the "cpuset_v2_mode" mount option.
  * With v2 behavior, "cpus" and "mems" are always what the users have
  * requested and won't be changed by hotplug events. Only the effective
  * cpus or mems will be affected.
  */
 static inline bool is_in_v2_mode(void)
 {
         return cgroup_subsys_on_dfl(cpuset_cgrp_subsys) ||
               (cpuset_cgrp_subsys.root->flags & CGRP_ROOT_CPUSET_V2_MODE);
 }
 
 /**
  * partition_is_populated - check if partition has tasks
  * @cs: partition root to be checked
  * @excluded_child: a child cpuset to be excluded in task checking
  * Return: true if there are tasks, false otherwise
  *
  * It is assumed that @cs is a valid partition root. @excluded_child should
  * be non-NULL when this cpuset is going to become a partition itself.
  */
 static inline bool partition_is_populated(struct cpuset *cs,
                                           struct cpuset *excluded_child)
 {
         struct cgroup_subsys_state *css;
         struct cpuset *child;
 
         if (cs->css.cgroup->nr_populated_csets)
                 return true;
         if (!excluded_child && !cs->nr_subparts)
                 return cgroup_is_populated(cs->css.cgroup);
 
         rcu_read_lock();
         cpuset_for_each_child(child, css, cs) {
                 if (child == excluded_child)
                         continue;
                 if (is_partition_valid(child))
                         continue;
                 if (cgroup_is_populated(child->css.cgroup)) {
                         rcu_read_unlock();
                         return true;
                 }
         }
         rcu_read_unlock();
         return false;
 }
 
 /*
  * Return in pmask the portion of a task's cpusets's cpus_allowed that
  * are online and are capable of running the task.  If none are found,
  * walk up the cpuset hierarchy until we find one that does have some
  * appropriate cpus.
  *
  * One way or another, we guarantee to return some non-empty subset
  * of cpu_online_mask.
  *
  * Call with callback_lock or cpuset_mutex held.
  */
 static void guarantee_online_cpus(struct task_struct *tsk,
                                   struct cpumask *pmask)
 {
         const struct cpumask *possible_mask = task_cpu_possible_mask(tsk);
         struct cpuset *cs;
 
         if (WARN_ON(!cpumask_and(pmask, possible_mask, cpu_online_mask)))
                 cpumask_copy(pmask, cpu_online_mask);
 
         rcu_read_lock();
         cs = task_cs(tsk);
 
         while (!cpumask_intersects(cs->effective_cpus, pmask))
                 cs = parent_cs(cs);
 
         cpumask_and(pmask, pmask, cs->effective_cpus);
         rcu_read_unlock();
 }
 
 /*
  * Return in *pmask the portion of a cpusets's mems_allowed that
  * are online, with memory.  If none are online with memory, walk
  * up the cpuset hierarchy until we find one that does have some
  * online mems.  The top cpuset always has some mems online.
  *
  * One way or another, we guarantee to return some non-empty subset
  * of node_states[N_MEMORY].
  *
  * Call with callback_lock or cpuset_mutex held.
  */
 static void guarantee_online_mems(struct cpuset *cs, nodemask_t *pmask)
 {
         while (!nodes_intersects(cs->effective_mems, node_states[N_MEMORY]))
                 cs = parent_cs(cs);
         nodes_and(*pmask, cs->effective_mems, node_states[N_MEMORY]);
 }
 
 /*
  * update task's spread flag if cpuset's page/slab spread flag is set
  *
  * Call with callback_lock or cpuset_mutex held. The check can be skipped
  * if on default hierarchy.
  */
 static void cpuset_update_task_spread_flags(struct cpuset *cs,
                                         struct task_struct *tsk)
 {
         if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys))
                 return;
 
         if (is_spread_page(cs))
                 task_set_spread_page(tsk);
         else
                 task_clear_spread_page(tsk);
 
         if (is_spread_slab(cs))
                 task_set_spread_slab(tsk);
         else
                 task_clear_spread_slab(tsk);
 }
 
 /*
  * is_cpuset_subset(p, q) - Is cpuset p a subset of cpuset q?
  *
  * One cpuset is a subset of another if all its allowed CPUs and
  * Memory Nodes are a subset of the other, and its exclusive flags
  * are only set if the other's are set.  Call holding cpuset_mutex.
  */
 
 static int is_cpuset_subset(const struct cpuset *p, const struct cpuset *q)
 {
         return  cpumask_subset(p->cpus_allowed, q->cpus_allowed) &&
                 nodes_subset(p->mems_allowed, q->mems_allowed) &&
                 is_cpu_exclusive(p) <= is_cpu_exclusive(q) &&
                 is_mem_exclusive(p) <= is_mem_exclusive(q);
 }
 
 /**
  * alloc_cpumasks - allocate three cpumasks for cpuset
  * @cs:  the cpuset that have cpumasks to be allocated.
  * @tmp: the tmpmasks structure pointer
  * Return: 0 if successful, -ENOMEM otherwise.
  *
  * Only one of the two input arguments should be non-NULL.
  */
 static inline int alloc_cpumasks(struct cpuset *cs, struct tmpmasks *tmp)
 {
         cpumask_var_t *pmask1, *pmask2, *pmask3, *pmask4;
 
         if (cs) {
                 pmask1 = &cs->cpus_allowed;
                 pmask2 = &cs->effective_cpus;
                 pmask3 = &cs->effective_xcpus;
                 pmask4 = &cs->exclusive_cpus;
         } else {
                 pmask1 = &tmp->new_cpus;
                 pmask2 = &tmp->addmask;
                 pmask3 = &tmp->delmask;
                 pmask4 = NULL;
         }
 
         if (!zalloc_cpumask_var(pmask1, GFP_KERNEL))
                 return -ENOMEM;
 
         if (!zalloc_cpumask_var(pmask2, GFP_KERNEL))
                 goto free_one;
 
         if (!zalloc_cpumask_var(pmask3, GFP_KERNEL))
                 goto free_two;
 
         if (pmask4 && !zalloc_cpumask_var(pmask4, GFP_KERNEL))
                 goto free_three;
 
 
         return 0;
 
 free_three:
         free_cpumask_var(*pmask3);
 free_two:
         free_cpumask_var(*pmask2);
 free_one:
         free_cpumask_var(*pmask1);
         return -ENOMEM;
 }
 
 /**
  * free_cpumasks - free cpumasks in a tmpmasks structure
  * @cs:  the cpuset that have cpumasks to be free.
  * @tmp: the tmpmasks structure pointer
  */
 static inline void free_cpumasks(struct cpuset *cs, struct tmpmasks *tmp)
 {
         if (cs) {
                 free_cpumask_var(cs->cpus_allowed);
                 free_cpumask_var(cs->effective_cpus);
                 free_cpumask_var(cs->effective_xcpus);
                 free_cpumask_var(cs->exclusive_cpus);
         }
         if (tmp) {
                 free_cpumask_var(tmp->new_cpus);
                 free_cpumask_var(tmp->addmask);
                 free_cpumask_var(tmp->delmask);
         }
 }
 
 /**
  * alloc_trial_cpuset - allocate a trial cpuset
  * @cs: the cpuset that the trial cpuset duplicates
  */
 static struct cpuset *alloc_trial_cpuset(struct cpuset *cs)
 {
         struct cpuset *trial;
 
         trial = kmemdup(cs, sizeof(*cs), GFP_KERNEL);
         if (!trial)
                 return NULL;
 
         if (alloc_cpumasks(trial, NULL)) {
                 kfree(trial);
                 return NULL;
         }
 
         cpumask_copy(trial->cpus_allowed, cs->cpus_allowed);
         cpumask_copy(trial->effective_cpus, cs->effective_cpus);
         cpumask_copy(trial->effective_xcpus, cs->effective_xcpus);
         cpumask_copy(trial->exclusive_cpus, cs->exclusive_cpus);
         return trial;
 }
 
 /**
  * free_cpuset - free the cpuset
  * @cs: the cpuset to be freed
  */
 static inline void free_cpuset(struct cpuset *cs)
 {
         free_cpumasks(cs, NULL);
         kfree(cs);
 }
 
 /* Return user specified exclusive CPUs */
 static inline struct cpumask *user_xcpus(struct cpuset *cs)
 {
         return cpumask_empty(cs->exclusive_cpus) ? cs->cpus_allowed
                                                  : cs->exclusive_cpus;
 }
 
 static inline bool xcpus_empty(struct cpuset *cs)
 {
         return cpumask_empty(cs->cpus_allowed) &&
                cpumask_empty(cs->exclusive_cpus);
 }
 
 static inline struct cpumask *fetch_xcpus(struct cpuset *cs)
 {
         return !cpumask_empty(cs->exclusive_cpus) ? cs->exclusive_cpus :
                cpumask_empty(cs->effective_xcpus) ? cs->cpus_allowed
                                                   : cs->effective_xcpus;
 }
 
 /*
  * cpusets_are_exclusive() - check if two cpusets are exclusive
  *
  * Return true if exclusive, false if not
  */
 static inline bool cpusets_are_exclusive(struct cpuset *cs1, struct cpuset *cs2)
 {
         struct cpumask *xcpus1 = fetch_xcpus(cs1);
         struct cpumask *xcpus2 = fetch_xcpus(cs2);
 
         if (cpumask_intersects(xcpus1, xcpus2))
                 return false;
         return true;
 }
 
 /*
  * validate_change_legacy() - Validate conditions specific to legacy (v1)
  *                            behavior.
  */
 static int validate_change_legacy(struct cpuset *cur, struct cpuset *trial)
 {
         struct cgroup_subsys_state *css;
         struct cpuset *c, *par;
         int ret;
 
         WARN_ON_ONCE(!rcu_read_lock_held());
 
         /* Each of our child cpusets must be a subset of us */
         ret = -EBUSY;
         cpuset_for_each_child(c, css, cur)
                 if (!is_cpuset_subset(c, trial))
                         goto out;
 
         /* On legacy hierarchy, we must be a subset of our parent cpuset. */
         ret = -EACCES;
         par = parent_cs(cur);
         if (par && !is_cpuset_subset(trial, par))
                 goto out;
 
         ret = 0;
 out:
         return ret;
 }
 
 /*
  * validate_change() - Used to validate that any proposed cpuset change
  *                     follows the structural rules for cpusets.
  *
  * If we replaced the flag and mask values of the current cpuset
  * (cur) with those values in the trial cpuset (trial), would
  * our various subset and exclusive rules still be valid?  Presumes
  * cpuset_mutex held.
  *
  * 'cur' is the address of an actual, in-use cpuset.  Operations
  * such as list traversal that depend on the actual address of the
  * cpuset in the list must use cur below, not trial.
  *
  * 'trial' is the address of bulk structure copy of cur, with
  * perhaps one or more of the fields cpus_allowed, mems_allowed,
  * or flags changed to new, trial values.
  *
  * Return 0 if valid, -errno if not.
  */
 
 static int validate_change(struct cpuset *cur, struct cpuset *trial)
 {
         struct cgroup_subsys_state *css;
         struct cpuset *c, *par;
         int ret = 0;
 
         rcu_read_lock();
 
         if (!is_in_v2_mode())
                 ret = validate_change_legacy(cur, trial);
         if (ret)
                 goto out;
 
         /* Remaining checks don't apply to root cpuset */
         if (cur == &top_cpuset)
                 goto out;
 
         par = parent_cs(cur);
 
         /*
          * Cpusets with tasks - existing or newly being attached - can't
          * be changed to have empty cpus_allowed or mems_allowed.
          */
         ret = -ENOSPC;
         if ((cgroup_is_populated(cur->css.cgroup) || cur->attach_in_progress)) {
                 if (!cpumask_empty(cur->cpus_allowed) &&
                     cpumask_empty(trial->cpus_allowed))
                         goto out;
                 if (!nodes_empty(cur->mems_allowed) &&
                     nodes_empty(trial->mems_allowed))
                         goto out;
         }
 
         /*
          * We can't shrink if we won't have enough room for SCHED_DEADLINE
          * tasks.
          */
         ret = -EBUSY;
         if (is_cpu_exclusive(cur) &&
             !cpuset_cpumask_can_shrink(cur->cpus_allowed,
                                        trial->cpus_allowed))
                 goto out;
 
         /*
          * If either I or some sibling (!= me) is exclusive, we can't
          * overlap. exclusive_cpus cannot overlap with each other if set.
          */
         ret = -EINVAL;
         cpuset_for_each_child(c, css, par) {
                 bool txset, cxset;      /* Are exclusive_cpus set? */
 
                 if (c == cur)
                         continue;
 
                 txset = !cpumask_empty(trial->exclusive_cpus);
                 cxset = !cpumask_empty(c->exclusive_cpus);
                 if (is_cpu_exclusive(trial) || is_cpu_exclusive(c) ||
                     (txset && cxset)) {
                         if (!cpusets_are_exclusive(trial, c))
                                 goto out;
                 } else if (txset || cxset) {
                         struct cpumask *xcpus, *acpus;
 
                         /*
                          * When just one of the exclusive_cpus's is set,
                          * cpus_allowed of the other cpuset, if set, cannot be
                          * a subset of it or none of those CPUs will be
                          * available if these exclusive CPUs are activated.
                          */
                         if (txset) {
                                 xcpus = trial->exclusive_cpus;
                                 acpus = c->cpus_allowed;
                         } else {
                                 xcpus = c->exclusive_cpus;
                                 acpus = trial->cpus_allowed;
                         }
                         if (!cpumask_empty(acpus) && cpumask_subset(acpus, xcpus))
                                 goto out;
                 }
                 if ((is_mem_exclusive(trial) || is_mem_exclusive(c)) &&
                     nodes_intersects(trial->mems_allowed, c->mems_allowed))
                         goto out;
         }
 
         ret = 0;
 out:
         rcu_read_unlock();
         return ret;
 }
 
 #ifdef CONFIG_SMP
 /*
  * Helper routine for generate_sched_domains().
  * Do cpusets a, b have overlapping effective cpus_allowed masks?
  */
 static int cpusets_overlap(struct cpuset *a, struct cpuset *b)
 {
         return cpumask_intersects(a->effective_cpus, b->effective_cpus);
 }
 
 static void
 update_domain_attr(struct sched_domain_attr *dattr, struct cpuset *c)
 {
         if (dattr->relax_domain_level < c->relax_domain_level)
                 dattr->relax_domain_level = c->relax_domain_level;
         return;
 }
 
 static void update_domain_attr_tree(struct sched_domain_attr *dattr,
                                     struct cpuset *root_cs)
 {
         struct cpuset *cp;
         struct cgroup_subsys_state *pos_css;
 
         rcu_read_lock();
         cpuset_for_each_descendant_pre(cp, pos_css, root_cs) {
                 /* skip the whole subtree if @cp doesn't have any CPU */
                 if (cpumask_empty(cp->cpus_allowed)) {
                         pos_css = css_rightmost_descendant(pos_css);
                         continue;
                 }
 
                 if (is_sched_load_balance(cp))
                         update_domain_attr(dattr, cp);
         }
         rcu_read_unlock();
 }
 
 /* Must be called with cpuset_mutex held.  */
 static inline int nr_cpusets(void)
 {
         /* jump label reference count + the top-level cpuset */
         return static_key_count(&cpusets_enabled_key.key) + 1;
 }
 
 /*
  * generate_sched_domains()
  *
  * This function builds a partial partition of the systems CPUs
  * A 'partial partition' is a set of non-overlapping subsets whose
  * union is a subset of that set.
  * The output of this function needs to be passed to kernel/sched/core.c
  * partition_sched_domains() routine, which will rebuild the scheduler's
  * load balancing domains (sched domains) as specified by that partial
  * partition.
  *
  * See "What is sched_load_balance" in Documentation/admin-guide/cgroup-v1/cpusets.rst
  * for a background explanation of this.
  *
  * Does not return errors, on the theory that the callers of this
  * routine would rather not worry about failures to rebuild sched
  * domains when operating in the severe memory shortage situations
  * that could cause allocation failures below.
  *
  * Must be called with cpuset_mutex held.
  *
  * The three key local variables below are:
  *    cp - cpuset pointer, used (together with pos_css) to perform a
  *         top-down scan of all cpusets. For our purposes, rebuilding
  *         the schedulers sched domains, we can ignore !is_sched_load_
  *         balance cpusets.
  *  csa  - (for CpuSet Array) Array of pointers to all the cpusets
  *         that need to be load balanced, for convenient iterative
  *         access by the subsequent code that finds the best partition,
  *         i.e the set of domains (subsets) of CPUs such that the
  *         cpus_allowed of every cpuset marked is_sched_load_balance
  *         is a subset of one of these domains, while there are as
  *         many such domains as possible, each as small as possible.
  * doms  - Conversion of 'csa' to an array of cpumasks, for passing to
  *         the kernel/sched/core.c routine partition_sched_domains() in a
  *         convenient format, that can be easily compared to the prior
  *         value to determine what partition elements (sched domains)
  *         were changed (added or removed.)
  *
  * Finding the best partition (set of domains):
  *      The triple nested loops below over i, j, k scan over the
  *      load balanced cpusets (using the array of cpuset pointers in
  *      csa[]) looking for pairs of cpusets that have overlapping
  *      cpus_allowed, but which don't have the same 'pn' partition
  *      number and gives them in the same partition number.  It keeps
  *      looping on the 'restart' label until it can no longer find
  *      any such pairs.
  *
  *      The union of the cpus_allowed masks from the set of
  *      all cpusets having the same 'pn' value then form the one
  *      element of the partition (one sched domain) to be passed to
  *      partition_sched_domains().
  */
 static int generate_sched_domains(cpumask_var_t **domains,
                         struct sched_domain_attr **attributes)
 {
         struct cpuset *cp;      /* top-down scan of cpusets */
         struct cpuset **csa;    /* array of all cpuset ptrs */
         int csn;                /* how many cpuset ptrs in csa so far */
         int i, j, k;            /* indices for partition finding loops */
         cpumask_var_t *doms;    /* resulting partition; i.e. sched domains */
         struct sched_domain_attr *dattr;  /* attributes for custom domains */
         int ndoms = 0;          /* number of sched domains in result */
         int nslot;              /* next empty doms[] struct cpumask slot */
         struct cgroup_subsys_state *pos_css;
         bool root_load_balance = is_sched_load_balance(&top_cpuset);
         bool cgrpv2 = cgroup_subsys_on_dfl(cpuset_cgrp_subsys);
 
         doms = NULL;
         dattr = NULL;
         csa = NULL;
 
         /* Special case for the 99% of systems with one, full, sched domain */
         if (root_load_balance && cpumask_empty(subpartitions_cpus)) {
 single_root_domain:
                 ndoms = 1;
                 doms = alloc_sched_domains(ndoms);
                 if (!doms)
                         goto done;
 
                 dattr = kmalloc(sizeof(struct sched_domain_attr), GFP_KERNEL);
                 if (dattr) {
                         *dattr = SD_ATTR_INIT;
                         update_domain_attr_tree(dattr, &top_cpuset);
                 }
                 cpumask_and(doms[0], top_cpuset.effective_cpus,
                             housekeeping_cpumask(HK_TYPE_DOMAIN));
 
                 goto done;
         }
 
         csa = kmalloc_array(nr_cpusets(), sizeof(cp), GFP_KERNEL);
         if (!csa)
                 goto done;
         csn = 0;
 
         rcu_read_lock();
         if (root_load_balance)
                 csa[csn++] = &top_cpuset;
         cpuset_for_each_descendant_pre(cp, pos_css, &top_cpuset) {
                 if (cp == &top_cpuset)
                         continue;
 
                 if (cgrpv2)
                         goto v2;
 
                 /*
                  * v1:
                  * Continue traversing beyond @cp iff @cp has some CPUs and
                  * isn't load balancing.  The former is obvious.  The
                  * latter: All child cpusets contain a subset of the
                  * parent's cpus, so just skip them, and then we call
                  * update_domain_attr_tree() to calc relax_domain_level of
                  * the corresponding sched domain.
                  */
                 if (!cpumask_empty(cp->cpus_allowed) &&
                     !(is_sched_load_balance(cp) &&
                       cpumask_intersects(cp->cpus_allowed,
                                          housekeeping_cpumask(HK_TYPE_DOMAIN))))
                         continue;
 
                 if (is_sched_load_balance(cp) &&
                     !cpumask_empty(cp->effective_cpus))
                         csa[csn++] = cp;
 
                 /* skip @cp's subtree */
                 pos_css = css_rightmost_descendant(pos_css);
                 continue;
 
 v2:
                 /*
                  * Only valid partition roots that are not isolated and with
                  * non-empty effective_cpus will be saved into csn[].
                  */
                 if ((cp->partition_root_state == PRS_ROOT) &&
                     !cpumask_empty(cp->effective_cpus))
                         csa[csn++] = cp;
 
                 /*
                  * Skip @cp's subtree if not a partition root and has no
                  * exclusive CPUs to be granted to child cpusets.
                  */
                 if (!is_partition_valid(cp) && cpumask_empty(cp->exclusive_cpus))
                         pos_css = css_rightmost_descendant(pos_css);
         }
         rcu_read_unlock();
 
         /*
          * If there are only isolated partitions underneath the cgroup root,
          * we can optimize out unneeded sched domains scanning.
          */
         if (root_load_balance && (csn == 1))
                 goto single_root_domain;
 
         for (i = 0; i < csn; i++)
                 csa[i]->pn = i;
         ndoms = csn;
 
 restart:
         /* Find the best partition (set of sched domains) */
         for (i = 0; i < csn; i++) {
                 struct cpuset *a = csa[i];
                 int apn = a->pn;
 
                 for (j = 0; j < csn; j++) {
                         struct cpuset *b = csa[j];
                         int bpn = b->pn;
 
                         if (apn != bpn && cpusets_overlap(a, b)) {
                                 for (k = 0; k < csn; k++) {
                                         struct cpuset *c = csa[k];
 
                                         if (c->pn == bpn)
                                                 c->pn = apn;
                                 }
                                 ndoms--;        /* one less element */
                                 goto restart;
                         }
                 }
         }
 
         /*
          * Now we know how many domains to create.
          * Convert <csn, csa> to <ndoms, doms> and populate cpu masks.
          */
         doms = alloc_sched_domains(ndoms);
         if (!doms)
                 goto done;
 
         /*
          * The rest of the code, including the scheduler, can deal with
          * dattr==NULL case. No need to abort if alloc fails.
          */
         dattr = kmalloc_array(ndoms, sizeof(struct sched_domain_attr),
                               GFP_KERNEL);
 
         /*
          * Cgroup v2 doesn't support domain attributes, just set all of them
          * to SD_ATTR_INIT. Also non-isolating partition root CPUs are a
          * subset of HK_TYPE_DOMAIN housekeeping CPUs.
          */
         if (cgrpv2) {
                 for (i = 0; i < ndoms; i++) {
                         cpumask_copy(doms[i], csa[i]->effective_cpus);
                         if (dattr)
                                 dattr[i] = SD_ATTR_INIT;
                 }
                 goto done;
         }
 
         for (nslot = 0, i = 0; i < csn; i++) {
                 struct cpuset *a = csa[i];
                 struct cpumask *dp;
                 int apn = a->pn;
 
                 if (apn < 0) {
                         /* Skip completed partitions */
                         continue;
                 }
 
                 dp = doms[nslot];
 
                 if (nslot == ndoms) {
                         static int warnings = 10;
                         if (warnings) {
                                 pr_warn("rebuild_sched_domains confused: nslot %d, ndoms %d, csn %d, i %d, apn %d\n",
                                         nslot, ndoms, csn, i, apn);
                                 warnings--;
                         }
                         continue;
                 }
 
                 cpumask_clear(dp);
                 if (dattr)
                         *(dattr + nslot) = SD_ATTR_INIT;
                 for (j = i; j < csn; j++) {
                         struct cpuset *b = csa[j];
 
                         if (apn == b->pn) {
                                 cpumask_or(dp, dp, b->effective_cpus);
                                 cpumask_and(dp, dp, housekeeping_cpumask(HK_TYPE_DOMAIN));
                                 if (dattr)
                                         update_domain_attr_tree(dattr + nslot, b);
 
                                 /* Done with this partition */
                                 b->pn = -1;
                         }
                 }
                 nslot++;
         }
         BUG_ON(nslot != ndoms);
 
 done:
         kfree(csa);
 
         /*
          * Fallback to the default domain if kmalloc() failed.
          * See comments in partition_sched_domains().
          */
         if (doms == NULL)
                 ndoms = 1;
 
         *domains    = doms;
         *attributes = dattr;
         return ndoms;
 }
 
 static void dl_update_tasks_root_domain(struct cpuset *cs)
 {
         struct css_task_iter it;
         struct task_struct *task;
 
         if (cs->nr_deadline_tasks == 0)
                 return;
 
         css_task_iter_start(&cs->css, 0, &it);
 
         while ((task = css_task_iter_next(&it)))
                 dl_add_task_root_domain(task);
 
         css_task_iter_end(&it);
 }
 
 static void dl_rebuild_rd_accounting(void)
 {
         struct cpuset *cs = NULL;
         struct cgroup_subsys_state *pos_css;
 
         lockdep_assert_held(&cpuset_mutex);
         lockdep_assert_cpus_held();
         lockdep_assert_held(&sched_domains_mutex);
 
         rcu_read_lock();
 
         /*
          * Clear default root domain DL accounting, it will be computed again
          * if a task belongs to it.
          */
         dl_clear_root_domain(&def_root_domain);
 
         cpuset_for_each_descendant_pre(cs, pos_css, &top_cpuset) {
 
                 if (cpumask_empty(cs->effective_cpus)) {
                         pos_css = css_rightmost_descendant(pos_css);
                         continue;
                 }
 
                 css_get(&cs->css);
 
                 rcu_read_unlock();
 
                 dl_update_tasks_root_domain(cs);
 
                 rcu_read_lock();
                 css_put(&cs->css);
         }
         rcu_read_unlock();
 }
 
 static void
 partition_and_rebuild_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
                                     struct sched_domain_attr *dattr_new)
 {
         mutex_lock(&sched_domains_mutex);
         partition_sched_domains_locked(ndoms_new, doms_new, dattr_new);
         dl_rebuild_rd_accounting();
         mutex_unlock(&sched_domains_mutex);
 }
 
 /*
  * Rebuild scheduler domains.
  *
  * If the flag 'sched_load_balance' of any cpuset with non-empty
  * 'cpus' changes, or if the 'cpus' allowed changes in any cpuset
  * which has that flag enabled, or if any cpuset with a non-empty
  * 'cpus' is removed, then call this routine to rebuild the
  * scheduler's dynamic sched domains.
  *
  * Call with cpuset_mutex held.  Takes cpus_read_lock().
  */
 static void rebuild_sched_domains_locked(void)
 {
         struct cgroup_subsys_state *pos_css;
         struct sched_domain_attr *attr;
         cpumask_var_t *doms;
         struct cpuset *cs;
         int ndoms;
 
         lockdep_assert_cpus_held();
         lockdep_assert_held(&cpuset_mutex);
 
         /*
          * If we have raced with CPU hotplug, return early to avoid
          * passing doms with offlined cpu to partition_sched_domains().
          * Anyways, cpuset_handle_hotplug() will rebuild sched domains.
          *
          * With no CPUs in any subpartitions, top_cpuset's effective CPUs
          * should be the same as the active CPUs, so checking only top_cpuset
          * is enough to detect racing CPU offlines.
          */
         if (cpumask_empty(subpartitions_cpus) &&
             !cpumask_equal(top_cpuset.effective_cpus, cpu_active_mask))
                 return;
 
         /*
          * With subpartition CPUs, however, the effective CPUs of a partition
          * root should be only a subset of the active CPUs.  Since a CPU in any
          * partition root could be offlined, all must be checked.
          */
         if (!cpumask_empty(subpartitions_cpus)) {
                 rcu_read_lock();
                 cpuset_for_each_descendant_pre(cs, pos_css, &top_cpuset) {
                         if (!is_partition_valid(cs)) {
                                 pos_css = css_rightmost_descendant(pos_css);
                                 continue;
                         }
                         if (!cpumask_subset(cs->effective_cpus,
                                             cpu_active_mask)) {
                                 rcu_read_unlock();
                                 return;
                         }
                 }
                 rcu_read_unlock();
         }
 
         /* Generate domain masks and attrs */
         ndoms = generate_sched_domains(&doms, &attr);
 
         /* Have scheduler rebuild the domains */
         partition_and_rebuild_sched_domains(ndoms, doms, attr);
 }
 #else /* !CONFIG_SMP */
 static void rebuild_sched_domains_locked(void)
 {
 }
 #endif /* CONFIG_SMP */
 
 static void rebuild_sched_domains_cpuslocked(void)
 {
         mutex_lock(&cpuset_mutex);
         rebuild_sched_domains_locked();
         mutex_unlock(&cpuset_mutex);
 }
 
 void rebuild_sched_domains(void)
 {
         cpus_read_lock();
         rebuild_sched_domains_cpuslocked();
         cpus_read_unlock();
 }
 
 /**
  * update_tasks_cpumask - Update the cpumasks of tasks in the cpuset.
  * @cs: the cpuset in which each task's cpus_allowed mask needs to be changed
  * @new_cpus: the temp variable for the new effective_cpus mask
  *
  * Iterate through each task of @cs updating its cpus_allowed to the
  * effective cpuset's.  As this function is called with cpuset_mutex held,
  * cpuset membership stays stable. For top_cpuset, task_cpu_possible_mask()
  * is used instead of effective_cpus to make sure all offline CPUs are also
  * included as hotplug code won't update cpumasks for tasks in top_cpuset.
  */
 static void update_tasks_cpumask(struct cpuset *cs, struct cpumask *new_cpus)
 {
         struct css_task_iter it;
         struct task_struct *task;
         bool top_cs = cs == &top_cpuset;
 
         css_task_iter_start(&cs->css, 0, &it);
         while ((task = css_task_iter_next(&it))) {
                 const struct cpumask *possible_mask = task_cpu_possible_mask(task);
 
                 if (top_cs) {
                         /*
                          * Percpu kthreads in top_cpuset are ignored
                          */
                         if (kthread_is_per_cpu(task))
                                 continue;
                         cpumask_andnot(new_cpus, possible_mask, subpartitions_cpus);
                 } else {
                         cpumask_and(new_cpus, possible_mask, cs->effective_cpus);
                 }
                 set_cpus_allowed_ptr(task, new_cpus);
         }
         css_task_iter_end(&it);
 }
 
 /**
  * compute_effective_cpumask - Compute the effective cpumask of the cpuset
  * @new_cpus: the temp variable for the new effective_cpus mask
  * @cs: the cpuset the need to recompute the new effective_cpus mask
  * @parent: the parent cpuset
  *
  * The result is valid only if the given cpuset isn't a partition root.
  */
 static void compute_effective_cpumask(struct cpumask *new_cpus,
                                       struct cpuset *cs, struct cpuset *parent)
 {
         cpumask_and(new_cpus, cs->cpus_allowed, parent->effective_cpus);
 }
 
 /*
  * Commands for update_parent_effective_cpumask
  */
 enum partition_cmd {
         partcmd_enable,         /* Enable partition root          */
         partcmd_enablei,        /* Enable isolated partition root */
         partcmd_disable,        /* Disable partition root         */
         partcmd_update,         /* Update parent's effective_cpus */
         partcmd_invalidate,     /* Make partition invalid         */
 };
 
 static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
                        int turning_on);
 static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs,
                                     struct tmpmasks *tmp);
 
 /*
  * Update partition exclusive flag
  *
  * Return: 0 if successful, an error code otherwise
  */
 static int update_partition_exclusive(struct cpuset *cs, int new_prs)
 {
         bool exclusive = (new_prs > PRS_MEMBER);
 
         if (exclusive && !is_cpu_exclusive(cs)) {
                 if (update_flag(CS_CPU_EXCLUSIVE, cs, 1))
                         return PERR_NOTEXCL;
         } else if (!exclusive && is_cpu_exclusive(cs)) {
                 /* Turning off CS_CPU_EXCLUSIVE will not return error */
                 update_flag(CS_CPU_EXCLUSIVE, cs, 0);
         }
         return 0;
 }
 
 /*
  * Update partition load balance flag and/or rebuild sched domain
  *
  * Changing load balance flag will automatically call
  * rebuild_sched_domains_locked().
  * This function is for cgroup v2 only.
  */
 static void update_partition_sd_lb(struct cpuset *cs, int old_prs)
 {
         int new_prs = cs->partition_root_state;
         bool rebuild_domains = (new_prs > 0) || (old_prs > 0);
         bool new_lb;
 
         /*
          * If cs is not a valid partition root, the load balance state
          * will follow its parent.
          */
         if (new_prs > 0) {
                 new_lb = (new_prs != PRS_ISOLATED);
         } else {
                 new_lb = is_sched_load_balance(parent_cs(cs));
         }
         if (new_lb != !!is_sched_load_balance(cs)) {
                 rebuild_domains = true;
                 if (new_lb)
                         set_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
                 else
                         clear_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
         }
 
         if (rebuild_domains)
                 rebuild_sched_domains_locked();
 }
 
 /*
  * tasks_nocpu_error - Return true if tasks will have no effective_cpus
  */
 static bool tasks_nocpu_error(struct cpuset *parent, struct cpuset *cs,
                               struct cpumask *xcpus)
 {
         /*
          * A populated partition (cs or parent) can't have empty effective_cpus
          */
         return (cpumask_subset(parent->effective_cpus, xcpus) &&
                 partition_is_populated(parent, cs)) ||
                (!cpumask_intersects(xcpus, cpu_active_mask) &&
                 partition_is_populated(cs, NULL));
 }
 
 static void reset_partition_data(struct cpuset *cs)
 {
         struct cpuset *parent = parent_cs(cs);
 
         if (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys))
                 return;
 
         lockdep_assert_held(&callback_lock);
 
         cs->nr_subparts = 0;
         if (cpumask_empty(cs->exclusive_cpus)) {
                 cpumask_clear(cs->effective_xcpus);
                 if (is_cpu_exclusive(cs))
                         clear_bit(CS_CPU_EXCLUSIVE, &cs->flags);
         }
         if (!cpumask_and(cs->effective_cpus,
                          parent->effective_cpus, cs->cpus_allowed)) {
                 cs->use_parent_ecpus = true;
                 parent->child_ecpus_count++;
                 cpumask_copy(cs->effective_cpus, parent->effective_cpus);
         }
 }
 
 /*
  * partition_xcpus_newstate - Exclusive CPUs state change
  * @old_prs: old partition_root_state
  * @new_prs: new partition_root_state
  * @xcpus: exclusive CPUs with state change
  */
 static void partition_xcpus_newstate(int old_prs, int new_prs, struct cpumask *xcpus)
 {
         WARN_ON_ONCE(old_prs == new_prs);
         if (new_prs == PRS_ISOLATED)
                 cpumask_or(isolated_cpus, isolated_cpus, xcpus);
         else
                 cpumask_andnot(isolated_cpus, isolated_cpus, xcpus);
 }
 
 /*
  * partition_xcpus_add - Add new exclusive CPUs to partition
  * @new_prs: new partition_root_state
  * @parent: parent cpuset
  * @xcpus: exclusive CPUs to be added
  * Return: true if isolated_cpus modified, false otherwise
  *
  * Remote partition if parent == NULL
  */
 static bool partition_xcpus_add(int new_prs, struct cpuset *parent,
                                 struct cpumask *xcpus)
 {
         bool isolcpus_updated;
 
         WARN_ON_ONCE(new_prs < 0);
         lockdep_assert_held(&callback_lock);
         if (!parent)
                 parent = &top_cpuset;
 
 
         if (parent == &top_cpuset)
                 cpumask_or(subpartitions_cpus, subpartitions_cpus, xcpus);
 
         isolcpus_updated = (new_prs != parent->partition_root_state);
         if (isolcpus_updated)
                 partition_xcpus_newstate(parent->partition_root_state, new_prs,
                                          xcpus);
 
         cpumask_andnot(parent->effective_cpus, parent->effective_cpus, xcpus);
         return isolcpus_updated;
 }
 
 /*
  * partition_xcpus_del - Remove exclusive CPUs from partition
  * @old_prs: old partition_root_state
  * @parent: parent cpuset
  * @xcpus: exclusive CPUs to be removed
  * Return: true if isolated_cpus modified, false otherwise
  *
  * Remote partition if parent == NULL
  */
 static bool partition_xcpus_del(int old_prs, struct cpuset *parent,
                                 struct cpumask *xcpus)
 {
         bool isolcpus_updated;
 
         WARN_ON_ONCE(old_prs < 0);
         lockdep_assert_held(&callback_lock);
         if (!parent)
                 parent = &top_cpuset;
 
         if (parent == &top_cpuset)
                 cpumask_andnot(subpartitions_cpus, subpartitions_cpus, xcpus);
 
         isolcpus_updated = (old_prs != parent->partition_root_state);
         if (isolcpus_updated)
                 partition_xcpus_newstate(old_prs, parent->partition_root_state,
                                          xcpus);
 
         cpumask_and(xcpus, xcpus, cpu_active_mask);
         cpumask_or(parent->effective_cpus, parent->effective_cpus, xcpus);
         return isolcpus_updated;
 }
 
 static void update_unbound_workqueue_cpumask(bool isolcpus_updated)
 {
         int ret;
 
         lockdep_assert_cpus_held();
 
         if (!isolcpus_updated)
                 return;
 
         ret = workqueue_unbound_exclude_cpumask(isolated_cpus);
         WARN_ON_ONCE(ret < 0);
 }
 
 /**
  * cpuset_cpu_is_isolated - Check if the given CPU is isolated
  * @cpu: the CPU number to be checked
  * Return: true if CPU is used in an isolated partition, false otherwise
  */
 bool cpuset_cpu_is_isolated(int cpu)
 {
         return cpumask_test_cpu(cpu, isolated_cpus);
 }
 EXPORT_SYMBOL_GPL(cpuset_cpu_is_isolated);
 
 /*
  * compute_effective_exclusive_cpumask - compute effective exclusive CPUs
  * @cs: cpuset
  * @xcpus: effective exclusive CPUs value to be set
  * Return: true if xcpus is not empty, false otherwise.
  *
  * Starting with exclusive_cpus (cpus_allowed if exclusive_cpus is not set),
  * it must be a subset of parent's effective_xcpus.
  */
 static bool compute_effective_exclusive_cpumask(struct cpuset *cs,
                                                 struct cpumask *xcpus)
 {
         struct cpuset *parent = parent_cs(cs);
 
         if (!xcpus)
                 xcpus = cs->effective_xcpus;
 
         return cpumask_and(xcpus, user_xcpus(cs), parent->effective_xcpus);
 }
 
 static inline bool is_remote_partition(struct cpuset *cs)
 {
         return !list_empty(&cs->remote_sibling);
 }
 
 static inline bool is_local_partition(struct cpuset *cs)
 {
         return is_partition_valid(cs) && !is_remote_partition(cs);
 }
 
 /*
  * remote_partition_enable - Enable current cpuset as a remote partition root
  * @cs: the cpuset to update
  * @new_prs: new partition_root_state
  * @tmp: temparary masks
  * Return: 1 if successful, 0 if error
  *
  * Enable the current cpuset to become a remote partition root taking CPUs
  * directly from the top cpuset. cpuset_mutex must be held by the caller.
  */
 static int remote_partition_enable(struct cpuset *cs, int new_prs,
                                    struct tmpmasks *tmp)
 {
         bool isolcpus_updated;
 
         /*
          * The user must have sysadmin privilege.
          */
         if (!capable(CAP_SYS_ADMIN))
                 return 0;
 
         /*
          * The requested exclusive_cpus must not be allocated to other
          * partitions and it can't use up all the root's effective_cpus.
          *
          * Note that if there is any local partition root above it or
          * remote partition root underneath it, its exclusive_cpus must
          * have overlapped with subpartitions_cpus.
          */
         compute_effective_exclusive_cpumask(cs, tmp->new_cpus);
         if (cpumask_empty(tmp->new_cpus) ||
             cpumask_intersects(tmp->new_cpus, subpartitions_cpus) ||
             cpumask_subset(top_cpuset.effective_cpus, tmp->new_cpus))
                 return 0;
 
         spin_lock_irq(&callback_lock);
         isolcpus_updated = partition_xcpus_add(new_prs, NULL, tmp->new_cpus);
         list_add(&cs->remote_sibling, &remote_children);
         if (cs->use_parent_ecpus) {
                 struct cpuset *parent = parent_cs(cs);
 
                 cs->use_parent_ecpus = false;
                 parent->child_ecpus_count--;
         }
         spin_unlock_irq(&callback_lock);
         update_unbound_workqueue_cpumask(isolcpus_updated);
 
         /*
          * Proprogate changes in top_cpuset's effective_cpus down the hierarchy.
          */
         update_tasks_cpumask(&top_cpuset, tmp->new_cpus);
         update_sibling_cpumasks(&top_cpuset, NULL, tmp);
         return 1;
 }
 
 /*
  * remote_partition_disable - Remove current cpuset from remote partition list
  * @cs: the cpuset to update
  * @tmp: temparary masks
  *
  * The effective_cpus is also updated.
  *
  * cpuset_mutex must be held by the caller.
  */
 static void remote_partition_disable(struct cpuset *cs, struct tmpmasks *tmp)
 {
         bool isolcpus_updated;
 
         compute_effective_exclusive_cpumask(cs, tmp->new_cpus);
         WARN_ON_ONCE(!is_remote_partition(cs));
         WARN_ON_ONCE(!cpumask_subset(tmp->new_cpus, subpartitions_cpus));
 
         spin_lock_irq(&callback_lock);
         list_del_init(&cs->remote_sibling);
         isolcpus_updated = partition_xcpus_del(cs->partition_root_state,
                                                NULL, tmp->new_cpus);
         cs->partition_root_state = -cs->partition_root_state;
         if (!cs->prs_err)
                 cs->prs_err = PERR_INVCPUS;
         reset_partition_data(cs);
         spin_unlock_irq(&callback_lock);
         update_unbound_workqueue_cpumask(isolcpus_updated);
 
         /*
          * Proprogate changes in top_cpuset's effective_cpus down the hierarchy.
          */
         update_tasks_cpumask(&top_cpuset, tmp->new_cpus);
         update_sibling_cpumasks(&top_cpuset, NULL, tmp);
 }
 
 /*
  * remote_cpus_update - cpus_exclusive change of remote partition
  * @cs: the cpuset to be updated
  * @newmask: the new effective_xcpus mask
  * @tmp: temparary masks
  *
  * top_cpuset and subpartitions_cpus will be updated or partition can be
  * invalidated.
  */
 static void remote_cpus_update(struct cpuset *cs, struct cpumask *newmask,
                                struct tmpmasks *tmp)
 {
         bool adding, deleting;
         int prs = cs->partition_root_state;
         int isolcpus_updated = 0;
 
         if (WARN_ON_ONCE(!is_remote_partition(cs)))
                 return;
 
         WARN_ON_ONCE(!cpumask_subset(cs->effective_xcpus, subpartitions_cpus));
 
         if (cpumask_empty(newmask))
                 goto invalidate;
 
         adding   = cpumask_andnot(tmp->addmask, newmask, cs->effective_xcpus);
         deleting = cpumask_andnot(tmp->delmask, cs->effective_xcpus, newmask);
 
         /*
          * Additions of remote CPUs is only allowed if those CPUs are
          * not allocated to other partitions and there are effective_cpus
          * left in the top cpuset.
          */
         if (adding && (!capable(CAP_SYS_ADMIN) ||
                        cpumask_intersects(tmp->addmask, subpartitions_cpus) ||
                        cpumask_subset(top_cpuset.effective_cpus, tmp->addmask)))
                 goto invalidate;
 
         spin_lock_irq(&callback_lock);
         if (adding)
                 isolcpus_updated += partition_xcpus_add(prs, NULL, tmp->addmask);
         if (deleting)
                 isolcpus_updated += partition_xcpus_del(prs, NULL, tmp->delmask);
         spin_unlock_irq(&callback_lock);
         update_unbound_workqueue_cpumask(isolcpus_updated);
 
         /*
          * Proprogate changes in top_cpuset's effective_cpus down the hierarchy.
          */
         update_tasks_cpumask(&top_cpuset, tmp->new_cpus);
         update_sibling_cpumasks(&top_cpuset, NULL, tmp);
         return;
 
 invalidate:
         remote_partition_disable(cs, tmp);
 }
 
 /*
  * remote_partition_check - check if a child remote partition needs update
  * @cs: the cpuset to be updated
  * @newmask: the new effective_xcpus mask
  * @delmask: temporary mask for deletion (not in tmp)
  * @tmp: temparary masks
  *
  * This should be called before the given cs has updated its cpus_allowed
  * and/or effective_xcpus.
  */
 static void remote_partition_check(struct cpuset *cs, struct cpumask *newmask,
                                    struct cpumask *delmask, struct tmpmasks *tmp)
 {
         struct cpuset *child, *next;
         int disable_cnt = 0;
 
         /*
          * Compute the effective exclusive CPUs that will be deleted.
          */
         if (!cpumask_andnot(delmask, cs->effective_xcpus, newmask) ||
             !cpumask_intersects(delmask, subpartitions_cpus))
                 return; /* No deletion of exclusive CPUs in partitions */
 
         /*
          * Searching the remote children list to look for those that will
          * be impacted by the deletion of exclusive CPUs.
          *
          * Since a cpuset must be removed from the remote children list
          * before it can go offline and holding cpuset_mutex will prevent
          * any change in cpuset status. RCU read lock isn't needed.
          */
         lockdep_assert_held(&cpuset_mutex);
         list_for_each_entry_safe(child, next, &remote_children, remote_sibling)
                 if (cpumask_intersects(child->effective_cpus, delmask)) {
                         remote_partition_disable(child, tmp);
                         disable_cnt++;
                 }
         if (disable_cnt)
                 rebuild_sched_domains_locked();
 }
 
 /*
  * prstate_housekeeping_conflict - check for partition & housekeeping conflicts
  * @prstate: partition root state to be checked
  * @new_cpus: cpu mask
  * Return: true if there is conflict, false otherwise
  *
  * CPUs outside of housekeeping_cpumask(HK_TYPE_DOMAIN) can only be used in
  * an isolated partition.
  */
 static bool prstate_housekeeping_conflict(int prstate, struct cpumask *new_cpus)
 {
         const struct cpumask *hk_domain = housekeeping_cpumask(HK_TYPE_DOMAIN);
         bool all_in_hk = cpumask_subset(new_cpus, hk_domain);
 
         if (!all_in_hk && (prstate != PRS_ISOLATED))
                 return true;
 
         return false;
 }
 
 /**
  * update_parent_effective_cpumask - update effective_cpus mask of parent cpuset
  * @cs:      The cpuset that requests change in partition root state
  * @cmd:     Partition root state change command
  * @newmask: Optional new cpumask for partcmd_update
  * @tmp:     Temporary addmask and delmask
  * Return:   0 or a partition root state error code
  *
  * For partcmd_enable*, the cpuset is being transformed from a non-partition
  * root to a partition root. The effective_xcpus (cpus_allowed if
  * effective_xcpus not set) mask of the given cpuset will be taken away from
  * parent's effective_cpus. The function will return 0 if all the CPUs listed
  * in effective_xcpus can be granted or an error code will be returned.
  *
  * For partcmd_disable, the cpuset is being transformed from a partition
  * root back to a non-partition root. Any CPUs in effective_xcpus will be
  * given back to parent's effective_cpus. 0 will always be returned.
  *
  * For partcmd_update, if the optional newmask is specified, the cpu list is
  * to be changed from effective_xcpus to newmask. Otherwise, effective_xcpus is
  * assumed to remain the same. The cpuset should either be a valid or invalid
  * partition root. The partition root state may change from valid to invalid
  * or vice versa. An error code will be returned if transitioning from
  * invalid to valid violates the exclusivity rule.
  *
  * For partcmd_invalidate, the current partition will be made invalid.
  *
  * The partcmd_enable* and partcmd_disable commands are used by
  * update_prstate(). An error code may be returned and the caller will check
  * for error.
  *
  * The partcmd_update command is used by update_cpumasks_hier() with newmask
  * NULL and update_cpumask() with newmask set. The partcmd_invalidate is used
  * by update_cpumask() with NULL newmask. In both cases, the callers won't
  * check for error and so partition_root_state and prs_error will be updated
  * directly.
  */
 static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
                                            struct cpumask *newmask,
                                            struct tmpmasks *tmp)
 {
         struct cpuset *parent = parent_cs(cs);
         int adding;     /* Adding cpus to parent's effective_cpus       */
         int deleting;   /* Deleting cpus from parent's effective_cpus   */
         int old_prs, new_prs;
         int part_error = PERR_NONE;     /* Partition error? */
         int subparts_delta = 0;
         struct cpumask *xcpus;          /* cs effective_xcpus */
         int isolcpus_updated = 0;
         bool nocpu;
 
         lockdep_assert_held(&cpuset_mutex);
 
         /*
          * new_prs will only be changed for the partcmd_update and
          * partcmd_invalidate commands.
          */
         adding = deleting = false;
         old_prs = new_prs = cs->partition_root_state;
         xcpus = user_xcpus(cs);
 
         if (cmd == partcmd_invalidate) {
                 if (is_prs_invalid(old_prs))
                         return 0;
 
                 /*
                  * Make the current partition invalid.
                  */
                 if (is_partition_valid(parent))
                         adding = cpumask_and(tmp->addmask,
                                              xcpus, parent->effective_xcpus);
                 if (old_prs > 0) {
                         new_prs = -old_prs;
                         subparts_delta--;
                 }
                 goto write_error;
         }
 
         /*
          * The parent must be a partition root.
          * The new cpumask, if present, or the current cpus_allowed must
          * not be empty.
          */
         if (!is_partition_valid(parent)) {
                 return is_partition_invalid(parent)
                        ? PERR_INVPARENT : PERR_NOTPART;
         }
         if (!newmask && xcpus_empty(cs))
                 return PERR_CPUSEMPTY;
 
         nocpu = tasks_nocpu_error(parent, cs, xcpus);
 
         if ((cmd == partcmd_enable) || (cmd == partcmd_enablei)) {
                 /*
                  * Enabling partition root is not allowed if its
                  * effective_xcpus is empty or doesn't overlap with
                  * parent's effective_xcpus.
                  */
                 if (cpumask_empty(xcpus) ||
                     !cpumask_intersects(xcpus, parent->effective_xcpus))
                         return PERR_INVCPUS;
 
                 if (prstate_housekeeping_conflict(new_prs, xcpus))
                         return PERR_HKEEPING;
 
                 /*
                  * A parent can be left with no CPU as long as there is no
                  * task directly associated with the parent partition.
                  */
                 if (nocpu)
                         return PERR_NOCPUS;
 
                 cpumask_copy(tmp->delmask, xcpus);
                 deleting = true;
                 subparts_delta++;
                 new_prs = (cmd == partcmd_enable) ? PRS_ROOT : PRS_ISOLATED;
         } else if (cmd == partcmd_disable) {
                 /*
                  * May need to add cpus to parent's effective_cpus for
                  * valid partition root.
                  */
                 adding = !is_prs_invalid(old_prs) &&
                           cpumask_and(tmp->addmask, xcpus, parent->effective_xcpus);
                 if (adding)
                         subparts_delta--;
                 new_prs = PRS_MEMBER;
         } else if (newmask) {
                 /*
                  * Empty cpumask is not allowed
                  */
                 if (cpumask_empty(newmask)) {
                         part_error = PERR_CPUSEMPTY;
                         goto write_error;
                 }
 
                 /*
                  * partcmd_update with newmask:
                  *
                  * Compute add/delete mask to/from effective_cpus
                  *
                  * For valid partition:
                  *   addmask = exclusive_cpus & ~newmask
                  *                            & parent->effective_xcpus
                  *   delmask = newmask & ~exclusive_cpus
                  *                     & parent->effective_xcpus
                  *
                  * For invalid partition:
                  *   delmask = newmask & parent->effective_xcpus
                  */
                 if (is_prs_invalid(old_prs)) {
                         adding = false;
                         deleting = cpumask_and(tmp->delmask,
                                         newmask, parent->effective_xcpus);
                 } else {
                         cpumask_andnot(tmp->addmask, xcpus, newmask);
                         adding = cpumask_and(tmp->addmask, tmp->addmask,
                                              parent->effective_xcpus);
 
                         cpumask_andnot(tmp->delmask, newmask, xcpus);
                         deleting = cpumask_and(tmp->delmask, tmp->delmask,
                                                parent->effective_xcpus);
                 }
                 /*
                  * Make partition invalid if parent's effective_cpus could
                  * become empty and there are tasks in the parent.
                  */
                 if (nocpu && (!adding ||
                     !cpumask_intersects(tmp->addmask, cpu_active_mask))) {
                         part_error = PERR_NOCPUS;
                         deleting = false;
                         adding = cpumask_and(tmp->addmask,
                                              xcpus, parent->effective_xcpus);
                 }
         } else {
                 /*
                  * partcmd_update w/o newmask
                  *
                  * delmask = effective_xcpus & parent->effective_cpus
                  *
                  * This can be called from:
                  * 1) update_cpumasks_hier()
                  * 2) cpuset_hotplug_update_tasks()
                  *
                  * Check to see if it can be transitioned from valid to
                  * invalid partition or vice versa.
                  *
                  * A partition error happens when parent has tasks and all
                  * its effective CPUs will have to be distributed out.
                  */
                 WARN_ON_ONCE(!is_partition_valid(parent));
                 if (nocpu) {
                         part_error = PERR_NOCPUS;
                         if (is_partition_valid(cs))
                                 adding = cpumask_and(tmp->addmask,
                                                 xcpus, parent->effective_xcpus);
                 } else if (is_partition_invalid(cs) &&
                            cpumask_subset(xcpus, parent->effective_xcpus)) {
                         struct cgroup_subsys_state *css;
                         struct cpuset *child;
                         bool exclusive = true;
 
                         /*
                          * Convert invalid partition to valid has to
                          * pass the cpu exclusivity test.
                          */
                         rcu_read_lock();
                         cpuset_for_each_child(child, css, parent) {
                                 if (child == cs)
                                         continue;
                                 if (!cpusets_are_exclusive(cs, child)) {
                                         exclusive = false;
                                         break;
                                 }
                         }
                         rcu_read_unlock();
                         if (exclusive)
                                 deleting = cpumask_and(tmp->delmask,
                                                 xcpus, parent->effective_cpus);
                         else
                                 part_error = PERR_NOTEXCL;
                 }
         }
 
 write_error:
         if (part_error)
                 WRITE_ONCE(cs->prs_err, part_error);
 
         if (cmd == partcmd_update) {
                 /*
                  * Check for possible transition between valid and invalid
                  * partition root.
                  */
                 switch (cs->partition_root_state) {
                 case PRS_ROOT:
                 case PRS_ISOLATED:
                         if (part_error) {
                                 new_prs = -old_prs;
                                 subparts_delta--;
                         }
                         break;
                 case PRS_INVALID_ROOT:
                 case PRS_INVALID_ISOLATED:
                         if (!part_error) {
                                 new_prs = -old_prs;
                                 subparts_delta++;
                         }
                         break;
                 }
         }
 
         if (!adding && !deleting && (new_prs == old_prs))
                 return 0;
 
         /*
          * Transitioning between invalid to valid or vice versa may require
          * changing CS_CPU_EXCLUSIVE. In the case of partcmd_update,
          * validate_change() has already been successfully called and
          * CPU lists in cs haven't been updated yet. So defer it to later.
          */
         if ((old_prs != new_prs) && (cmd != partcmd_update))  {
                 int err = update_partition_exclusive(cs, new_prs);
 
                 if (err)
                         return err;
         }
 
         /*
          * Change the parent's effective_cpus & effective_xcpus (top cpuset
          * only).
          *
          * Newly added CPUs will be removed from effective_cpus and
          * newly deleted ones will be added back to effective_cpus.
          */
         spin_lock_irq(&callback_lock);
         if (old_prs != new_prs) {
                 cs->partition_root_state = new_prs;
                 if (new_prs <= 0)
                         cs->nr_subparts = 0;
         }
         /*
          * Adding to parent's effective_cpus means deletion CPUs from cs
          * and vice versa.
          */
         if (adding)
                 isolcpus_updated += partition_xcpus_del(old_prs, parent,
                                                         tmp->addmask);
         if (deleting)
                 isolcpus_updated += partition_xcpus_add(new_prs, parent,
                                                         tmp->delmask);
 
         if (is_partition_valid(parent)) {
                 parent->nr_subparts += subparts_delta;
                 WARN_ON_ONCE(parent->nr_subparts < 0);
         }
         spin_unlock_irq(&callback_lock);
         update_unbound_workqueue_cpumask(isolcpus_updated);
 
         if ((old_prs != new_prs) && (cmd == partcmd_update))
                 update_partition_exclusive(cs, new_prs);
 
         if (adding || deleting) {
                 update_tasks_cpumask(parent, tmp->addmask);
                 update_sibling_cpumasks(parent, cs, tmp);
         }
 
         /*
          * For partcmd_update without newmask, it is being called from
          * cpuset_handle_hotplug(). Update the load balance flag and
          * scheduling domain accordingly.
          */
         if ((cmd == partcmd_update) && !newmask)
                 update_partition_sd_lb(cs, old_prs);
 
         notify_partition_change(cs, old_prs);
         return 0;
 }
 
 /**
  * compute_partition_effective_cpumask - compute effective_cpus for partition
  * @cs: partition root cpuset
  * @new_ecpus: previously computed effective_cpus to be updated
  *
  * Compute the effective_cpus of a partition root by scanning effective_xcpus
  * of child partition roots and excluding their effective_xcpus.
  *
  * This has the side effect of invalidating valid child partition roots,
  * if necessary. Since it is called from either cpuset_hotplug_update_tasks()
  * or update_cpumasks_hier() where parent and children are modified
  * successively, we don't need to call update_parent_effective_cpumask()
  * and the child's effective_cpus will be updated in later iterations.
  *
  * Note that rcu_read_lock() is assumed to be held.
  */
 static void compute_partition_effective_cpumask(struct cpuset *cs,
                                                 struct cpumask *new_ecpus)
 {
         struct cgroup_subsys_state *css;
         struct cpuset *child;
         bool populated = partition_is_populated(cs, NULL);
 
         /*
          * Check child partition roots to see if they should be
          * invalidated when
          *  1) child effective_xcpus not a subset of new
          *     excluisve_cpus
          *  2) All the effective_cpus will be used up and cp
          *     has tasks
          */
         compute_effective_exclusive_cpumask(cs, new_ecpus);
         cpumask_and(new_ecpus, new_ecpus, cpu_active_mask);
 
         rcu_read_lock();
         cpuset_for_each_child(child, css, cs) {
                 if (!is_partition_valid(child))
                         continue;
 
                 child->prs_err = 0;
                 if (!cpumask_subset(child->effective_xcpus,
                                     cs->effective_xcpus))
                         child->prs_err = PERR_INVCPUS;
                 else if (populated &&
                          cpumask_subset(new_ecpus, child->effective_xcpus))
                         child->prs_err = PERR_NOCPUS;
 
                 if (child->prs_err) {
                         int old_prs = child->partition_root_state;
 
                         /*
                          * Invalidate child partition
                          */
                         spin_lock_irq(&callback_lock);
                         make_partition_invalid(child);
                         cs->nr_subparts--;
                         child->nr_subparts = 0;
                         spin_unlock_irq(&callback_lock);
                         notify_partition_change(child, old_prs);
                         continue;
                 }
                 cpumask_andnot(new_ecpus, new_ecpus,
                                child->effective_xcpus);
         }
         rcu_read_unlock();
 }
 
 /*
  * update_cpumasks_hier() flags
  */
 #define HIER_CHECKALL           0x01    /* Check all cpusets with no skipping */
 #define HIER_NO_SD_REBUILD      0x02    /* Don't rebuild sched domains */
 
 /*
  * update_cpumasks_hier - Update effective cpumasks and tasks in the subtree
  * @cs:  the cpuset to consider
  * @tmp: temp variables for calculating effective_cpus & partition setup
  * @force: don't skip any descendant cpusets if set
  *
  * When configured cpumask is changed, the effective cpumasks of this cpuset
  * and all its descendants need to be updated.
  *
  * On legacy hierarchy, effective_cpus will be the same with cpu_allowed.
  *
  * Called with cpuset_mutex held
  */
 static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp,
                                  int flags)
 {
         struct cpuset *cp;
         struct cgroup_subsys_state *pos_css;
         bool need_rebuild_sched_domains = false;
         int old_prs, new_prs;
 
         rcu_read_lock();
         cpuset_for_each_descendant_pre(cp, pos_css, cs) {
                 struct cpuset *parent = parent_cs(cp);
                 bool remote = is_remote_partition(cp);
                 bool update_parent = false;
 
                 /*
                  * Skip descendent remote partition that acquires CPUs
                  * directly from top cpuset unless it is cs.
                  */
                 if (remote && (cp != cs)) {
                         pos_css = css_rightmost_descendant(pos_css);
                         continue;
                 }
 
                 /*
                  * Update effective_xcpus if exclusive_cpus set.
                  * The case when exclusive_cpus isn't set is handled later.
                  */
                 if (!cpumask_empty(cp->exclusive_cpus) && (cp != cs)) {
                         spin_lock_irq(&callback_lock);
                         compute_effective_exclusive_cpumask(cp, NULL);
                         spin_unlock_irq(&callback_lock);
                 }
 
                 old_prs = new_prs = cp->partition_root_state;
                 if (remote || (is_partition_valid(parent) &&
                                is_partition_valid(cp)))
                         compute_partition_effective_cpumask(cp, tmp->new_cpus);
                 else
                         compute_effective_cpumask(tmp->new_cpus, cp, parent);
 
                 /*
                  * A partition with no effective_cpus is allowed as long as
                  * there is no task associated with it. Call
                  * update_parent_effective_cpumask() to check it.
                  */
                 if (is_partition_valid(cp) && cpumask_empty(tmp->new_cpus)) {
                         update_parent = true;
                         goto update_parent_effective;
                 }
 
                 /*
                  * If it becomes empty, inherit the effective mask of the
                  * parent, which is guaranteed to have some CPUs unless
                  * it is a partition root that has explicitly distributed
                  * out all its CPUs.
                  */
                 if (is_in_v2_mode() && !remote && cpumask_empty(tmp->new_cpus)) {
                         cpumask_copy(tmp->new_cpus, parent->effective_cpus);
                         if (!cp->use_parent_ecpus) {
                                 cp->use_parent_ecpus = true;
                                 parent->child_ecpus_count++;
                         }
                 } else if (cp->use_parent_ecpus) {
                         cp->use_parent_ecpus = false;
                         WARN_ON_ONCE(!parent->child_ecpus_count);
                         parent->child_ecpus_count--;
                 }
 
                 if (remote)
                         goto get_css;
 
                 /*
                  * Skip the whole subtree if
                  * 1) the cpumask remains the same,
                  * 2) has no partition root state,
                  * 3) HIER_CHECKALL flag not set, and
                  * 4) for v2 load balance state same as its parent.
                  */
                 if (!cp->partition_root_state && !(flags & HIER_CHECKALL) &&
                     cpumask_equal(tmp->new_cpus, cp->effective_cpus) &&
                     (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) ||
                     (is_sched_load_balance(parent) == is_sched_load_balance(cp)))) {
                         pos_css = css_rightmost_descendant(pos_css);
                         continue;
                 }
 
 update_parent_effective:
                 /*
                  * update_parent_effective_cpumask() should have been called
                  * for cs already in update_cpumask(). We should also call
                  * update_tasks_cpumask() again for tasks in the parent
                  * cpuset if the parent's effective_cpus changes.
                  */
                 if ((cp != cs) && old_prs) {
                         switch (parent->partition_root_state) {
                         case PRS_ROOT:
                         case PRS_ISOLATED:
                                 update_parent = true;
                                 break;
 
                         default:
                                 /*
                                  * When parent is not a partition root or is
                                  * invalid, child partition roots become
                                  * invalid too.
                                  */
                                 if (is_partition_valid(cp))
                                         new_prs = -cp->partition_root_state;
                                 WRITE_ONCE(cp->prs_err,
                                            is_partition_invalid(parent)
                                            ? PERR_INVPARENT : PERR_NOTPART);
                                 break;
                         }
                 }
 get_css:
                 if (!css_tryget_online(&cp->css))
                         continue;
                 rcu_read_unlock();
 
                 if (update_parent) {
                         update_parent_effective_cpumask(cp, partcmd_update, NULL, tmp);
                         /*
                          * The cpuset partition_root_state may become
                          * invalid. Capture it.
                          */
                         new_prs = cp->partition_root_state;
                 }
 
                 spin_lock_irq(&callback_lock);
                 cpumask_copy(cp->effective_cpus, tmp->new_cpus);
                 cp->partition_root_state = new_prs;
                 /*
                  * Make sure effective_xcpus is properly set for a valid
                  * partition root.
                  */
                 if ((new_prs > 0) && cpumask_empty(cp->exclusive_cpus))
                         cpumask_and(cp->effective_xcpus,
                                     cp->cpus_allowed, parent->effective_xcpus);
                 else if (new_prs < 0)
                         reset_partition_data(cp);
                 spin_unlock_irq(&callback_lock);
 
                 notify_partition_change(cp, old_prs);
 
                 WARN_ON(!is_in_v2_mode() &&
                         !cpumask_equal(cp->cpus_allowed, cp->effective_cpus));
 
                 update_tasks_cpumask(cp, cp->effective_cpus);
 
                 /*
                  * On default hierarchy, inherit the CS_SCHED_LOAD_BALANCE
                  * from parent if current cpuset isn't a valid partition root
                  * and their load balance states differ.
                  */
                 if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
                     !is_partition_valid(cp) &&
                     (is_sched_load_balance(parent) != is_sched_load_balance(cp))) {
                         if (is_sched_load_balance(parent))
                                 set_bit(CS_SCHED_LOAD_BALANCE, &cp->flags);
                         else
                                 clear_bit(CS_SCHED_LOAD_BALANCE, &cp->flags);
                 }
 
                 /*
                  * On legacy hierarchy, if the effective cpumask of any non-
                  * empty cpuset is changed, we need to rebuild sched domains.
                  * On default hierarchy, the cpuset needs to be a partition
                  * root as well.
                  */
                 if (!cpumask_empty(cp->cpus_allowed) &&
                     is_sched_load_balance(cp) &&
                    (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) ||
                     is_partition_valid(cp)))
                         need_rebuild_sched_domains = true;
 
                 rcu_read_lock();
                 css_put(&cp->css);
         }
         rcu_read_unlock();
 
         if (need_rebuild_sched_domains && !(flags & HIER_NO_SD_REBUILD))
                 rebuild_sched_domains_locked();
 }
 
 /**
  * update_sibling_cpumasks - Update siblings cpumasks
  * @parent:  Parent cpuset
  * @cs:      Current cpuset
  * @tmp:     Temp variables
  */
 static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs,
                                     struct tmpmasks *tmp)
 {
         struct cpuset *sibling;
         struct cgroup_subsys_state *pos_css;
 
         lockdep_assert_held(&cpuset_mutex);
 
         /*
          * Check all its siblings and call update_cpumasks_hier()
          * if their effective_cpus will need to be changed.
          *
          * With the addition of effective_xcpus which is a subset of
          * cpus_allowed. It is possible a change in parent's effective_cpus
          * due to a change in a child partition's effective_xcpus will impact
          * its siblings even if they do not inherit parent's effective_cpus
          * directly.
          *
          * The update_cpumasks_hier() function may sleep. So we have to
          * release the RCU read lock before calling it. HIER_NO_SD_REBUILD
          * flag is used to suppress rebuild of sched domains as the callers
          * will take care of that.
          */
         rcu_read_lock();
         cpuset_for_each_child(sibling, pos_css, parent) {
                 if (sibling == cs)
                         continue;
                 if (!sibling->use_parent_ecpus &&
                     !is_partition_valid(sibling)) {
                         compute_effective_cpumask(tmp->new_cpus, sibling,
                                                   parent);
                         if (cpumask_equal(tmp->new_cpus, sibling->effective_cpus))
                                 continue;
                 }
                 if (!css_tryget_online(&sibling->css))
                         continue;
 
                 rcu_read_unlock();
                 update_cpumasks_hier(sibling, tmp, HIER_NO_SD_REBUILD);
                 rcu_read_lock();
                 css_put(&sibling->css);
         }
         rcu_read_unlock();
 }
 
 /**
  * update_cpumask - update the cpus_allowed mask of a cpuset and all tasks in it
  * @cs: the cpuset to consider
  * @trialcs: trial cpuset
  * @buf: buffer of cpu numbers written to this cpuset
  */
 static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
                           const char *buf)
 {
         int retval;
         struct tmpmasks tmp;
         struct cpuset *parent = parent_cs(cs);
         bool invalidate = false;
         int hier_flags = 0;
         int old_prs = cs->partition_root_state;
 
         /* top_cpuset.cpus_allowed tracks cpu_online_mask; it's read-only */
         if (cs == &top_cpuset)
                 return -EACCES;
 
         /*
          * An empty cpus_allowed is ok only if the cpuset has no tasks.
          * Since cpulist_parse() fails on an empty mask, we special case
          * that parsing.  The validate_change() call ensures that cpusets
          * with tasks have cpus.
          */
         if (!*buf) {
                 cpumask_clear(trialcs->cpus_allowed);
                 cpumask_clear(trialcs->effective_xcpus);
         } else {
                 retval = cpulist_parse(buf, trialcs->cpus_allowed);
                 if (retval < 0)
                         return retval;
 
                 if (!cpumask_subset(trialcs->cpus_allowed,
                                     top_cpuset.cpus_allowed))
                         return -EINVAL;
 
                 /*
                  * When exclusive_cpus isn't explicitly set, it is constrainted
                  * by cpus_allowed and parent's effective_xcpus. Otherwise,
                  * trialcs->effective_xcpus is used as a temporary cpumask
                  * for checking validity of the partition root.
                  */
                 if (!cpumask_empty(trialcs->exclusive_cpus) || is_partition_valid(cs))
                         compute_effective_exclusive_cpumask(trialcs, NULL);
         }
 
         /* Nothing to do if the cpus didn't change */
         if (cpumask_equal(cs->cpus_allowed, trialcs->cpus_allowed))
                 return 0;
 
         if (alloc_cpumasks(NULL, &tmp))
                 return -ENOMEM;
 
         if (old_prs) {
                 if (is_partition_valid(cs) &&
                     cpumask_empty(trialcs->effective_xcpus)) {
                         invalidate = true;
                         cs->prs_err = PERR_INVCPUS;
                 } else if (prstate_housekeeping_conflict(old_prs, trialcs->effective_xcpus)) {
                         invalidate = true;
                         cs->prs_err = PERR_HKEEPING;
                 } else if (tasks_nocpu_error(parent, cs, trialcs->effective_xcpus)) {
                         invalidate = true;
                         cs->prs_err = PERR_NOCPUS;
                 }
         }
 
         /*
          * Check all the descendants in update_cpumasks_hier() if
          * effective_xcpus is to be changed.
          */
         if (!cpumask_equal(cs->effective_xcpus, trialcs->effective_xcpus))
                 hier_flags = HIER_CHECKALL;
 
         retval = validate_change(cs, trialcs);
 
         if ((retval == -EINVAL) && cgroup_subsys_on_dfl(cpuset_cgrp_subsys)) {
                 struct cgroup_subsys_state *css;
                 struct cpuset *cp;
 
                 /*
                  * The -EINVAL error code indicates that partition sibling
                  * CPU exclusivity rule has been violated. We still allow
                  * the cpumask change to proceed while invalidating the
                  * partition. However, any conflicting sibling partitions
                  * have to be marked as invalid too.
                  */
                 invalidate = true;
                 rcu_read_lock();
                 cpuset_for_each_child(cp, css, parent) {
                         struct cpumask *xcpus = fetch_xcpus(trialcs);
 
                         if (is_partition_valid(cp) &&
                             cpumask_intersects(xcpus, cp->effective_xcpus)) {
                                 rcu_read_unlock();
                                 update_parent_effective_cpumask(cp, partcmd_invalidate, NULL, &tmp);
                                 rcu_read_lock();
                         }
                 }
                 rcu_read_unlock();
                 retval = 0;
         }
 
         if (retval < 0)
                 goto out_free;
 
         if (is_partition_valid(cs) ||
            (is_partition_invalid(cs) && !invalidate)) {
                 struct cpumask *xcpus = trialcs->effective_xcpus;
 
                 if (cpumask_empty(xcpus) && is_partition_invalid(cs))
                         xcpus = trialcs->cpus_allowed;
 
                 /*
                  * Call remote_cpus_update() to handle valid remote partition
                  */
                 if (is_remote_partition(cs))
                         remote_cpus_update(cs, xcpus, &tmp);
                 else if (invalidate)
                         update_parent_effective_cpumask(cs, partcmd_invalidate,
                                                         NULL, &tmp);
                 else
                         update_parent_effective_cpumask(cs, partcmd_update,
                                                         xcpus, &tmp);
         } else if (!cpumask_empty(cs->exclusive_cpus)) {
                 /*
                  * Use trialcs->effective_cpus as a temp cpumask
                  */
                 remote_partition_check(cs, trialcs->effective_xcpus,
                                        trialcs->effective_cpus, &tmp);
         }
 
         spin_lock_irq(&callback_lock);
         cpumask_copy(cs->cpus_allowed, trialcs->cpus_allowed);
         cpumask_copy(cs->effective_xcpus, trialcs->effective_xcpus);
         if ((old_prs > 0) && !is_partition_valid(cs))
                 reset_partition_data(cs);
         spin_unlock_irq(&callback_lock);
 
         /* effective_cpus/effective_xcpus will be updated here */
         update_cpumasks_hier(cs, &tmp, hier_flags);
 
         /* Update CS_SCHED_LOAD_BALANCE and/or sched_domains, if necessary */
         if (cs->partition_root_state)
                 update_partition_sd_lb(cs, old_prs);
 out_free:
         free_cpumasks(NULL, &tmp);
         return retval;
 }
 
 /**
  * update_exclusive_cpumask - update the exclusive_cpus mask of a cpuset
  * @cs: the cpuset to consider
  * @trialcs: trial cpuset
  * @buf: buffer of cpu numbers written to this cpuset
  *
  * The tasks' cpumask will be updated if cs is a valid partition root.
  */
 static int update_exclusive_cpumask(struct cpuset *cs, struct cpuset *trialcs,
                                     const char *buf)
 {
         int retval;
         struct tmpmasks tmp;
         struct cpuset *parent = parent_cs(cs);
         bool invalidate = false;
         int hier_flags = 0;
         int old_prs = cs->partition_root_state;
 
         if (!*buf) {
                 cpumask_clear(trialcs->exclusive_cpus);
                 cpumask_clear(trialcs->effective_xcpus);
         } else {
                 retval = cpulist_parse(buf, trialcs->exclusive_cpus);
                 if (retval < 0)
                         return retval;
         }
 
         /* Nothing to do if the CPUs didn't change */
         if (cpumask_equal(cs->exclusive_cpus, trialcs->exclusive_cpus))
                 return 0;
 
         if (*buf)
                 compute_effective_exclusive_cpumask(trialcs, NULL);
 
         /*
          * Check all the descendants in update_cpumasks_hier() if
          * effective_xcpus is to be changed.
          */
         if (!cpumask_equal(cs->effective_xcpus, trialcs->effective_xcpus))
                 hier_flags = HIER_CHECKALL;
 
         retval = validate_change(cs, trialcs);
         if (retval)
                 return retval;
 
         if (alloc_cpumasks(NULL, &tmp))
                 return -ENOMEM;
 
         if (old_prs) {
                 if (cpumask_empty(trialcs->effective_xcpus)) {
                         invalidate = true;
                         cs->prs_err = PERR_INVCPUS;
                 } else if (prstate_housekeeping_conflict(old_prs, trialcs->effective_xcpus)) {
                         invalidate = true;
                         cs->prs_err = PERR_HKEEPING;
                 } else if (tasks_nocpu_error(parent, cs, trialcs->effective_xcpus)) {
                         invalidate = true;
                         cs->prs_err = PERR_NOCPUS;
                 }
 
                 if (is_remote_partition(cs)) {
                         if (invalidate)
                                 remote_partition_disable(cs, &tmp);
                         else
                                 remote_cpus_update(cs, trialcs->effective_xcpus,
                                                    &tmp);
                 } else if (invalidate) {
                         update_parent_effective_cpumask(cs, partcmd_invalidate,
                                                         NULL, &tmp);
                 } else {
                         update_parent_effective_cpumask(cs, partcmd_update,
                                                 trialcs->effective_xcpus, &tmp);
                 }
         } else if (!cpumask_empty(trialcs->exclusive_cpus)) {
                 /*
                  * Use trialcs->effective_cpus as a temp cpumask
                  */
                 remote_partition_check(cs, trialcs->effective_xcpus,
                                        trialcs->effective_cpus, &tmp);
         }
         spin_lock_irq(&callback_lock);
         cpumask_copy(cs->exclusive_cpus, trialcs->exclusive_cpus);
         cpumask_copy(cs->effective_xcpus, trialcs->effective_xcpus);
         if ((old_prs > 0) && !is_partition_valid(cs))
                 reset_partition_data(cs);
         spin_unlock_irq(&callback_lock);
 
         /*
          * Call update_cpumasks_hier() to update effective_cpus/effective_xcpus
          * of the subtree when it is a valid partition root or effective_xcpus
          * is updated.
          */
         if (is_partition_valid(cs) || hier_flags)
                 update_cpumasks_hier(cs, &tmp, hier_flags);
 
         /* Update CS_SCHED_LOAD_BALANCE and/or sched_domains, if necessary */
         if (cs->partition_root_state)
                 update_partition_sd_lb(cs, old_prs);
 
         free_cpumasks(NULL, &tmp);
         return 0;
 }
 
 /*
  * Migrate memory region from one set of nodes to another.  This is
  * performed asynchronously as it can be called from process migration path
  * holding locks involved in process management.  All mm migrations are
  * performed in the queued order and can be waited for by flushing
  * cpuset_migrate_mm_wq.
  */
 
 struct cpuset_migrate_mm_work {
         struct work_struct      work;
         struct mm_struct        *mm;
         nodemask_t              from;
         nodemask_t              to;
 };
 
 static void cpuset_migrate_mm_workfn(struct work_struct *work)
 {
         struct cpuset_migrate_mm_work *mwork =
                 container_of(work, struct cpuset_migrate_mm_work, work);
 
         /* on a wq worker, no need to worry about %current's mems_allowed */
         do_migrate_pages(mwork->mm, &mwork->from, &mwork->to, MPOL_MF_MOVE_ALL);
         mmput(mwork->mm);
         kfree(mwork);
 }
 
 static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from,
                                                         const nodemask_t *to)
 {
         struct cpuset_migrate_mm_work *mwork;
 
         if (nodes_equal(*from, *to)) {
                 mmput(mm);
                 return;
         }
 
         mwork = kzalloc(sizeof(*mwork), GFP_KERNEL);
         if (mwork) {
                 mwork->mm = mm;
                 mwork->from = *from;
                 mwork->to = *to;
                 INIT_WORK(&mwork->work, cpuset_migrate_mm_workfn);
                 queue_work(cpuset_migrate_mm_wq, &mwork->work);
         } else {
                 mmput(mm);
         }
 }
 
 static void cpuset_post_attach(void)
 {
         flush_workqueue(cpuset_migrate_mm_wq);
 }
 
 /*
  * cpuset_change_task_nodemask - change task's mems_allowed and mempolicy
  * @tsk: the task to change
  * @newmems: new nodes that the task will be set
  *
  * We use the mems_allowed_seq seqlock to safely update both tsk->mems_allowed
  * and rebind an eventual tasks' mempolicy. If the task is allocating in
  * parallel, it might temporarily see an empty intersection, which results in
  * a seqlock check and retry before OOM or allocation failure.
  */
 static void cpuset_change_task_nodemask(struct task_struct *tsk,
                                         nodemask_t *newmems)
 {
         task_lock(tsk);
 
         local_irq_disable();
         write_seqcount_begin(&tsk->mems_allowed_seq);
 
         nodes_or(tsk->mems_allowed, tsk->mems_allowed, *newmems);
         mpol_rebind_task(tsk, newmems);
         tsk->mems_allowed = *newmems;
 
         write_seqcount_end(&tsk->mems_allowed_seq);
         local_irq_enable();
 
         task_unlock(tsk);
 }
 
 static void *cpuset_being_rebound;
 
 /**
  * update_tasks_nodemask - Update the nodemasks of tasks in the cpuset.
  * @cs: the cpuset in which each task's mems_allowed mask needs to be changed
  *
  * Iterate through each task of @cs updating its mems_allowed to the
  * effective cpuset's.  As this function is called with cpuset_mutex held,
  * cpuset membership stays stable.
  */
 static void update_tasks_nodemask(struct cpuset *cs)
 {
         static nodemask_t newmems;      /* protected by cpuset_mutex */
         struct css_task_iter it;
         struct task_struct *task;
 
         cpuset_being_rebound = cs;              /* causes mpol_dup() rebind */
 
         guarantee_online_mems(cs, &newmems);
 
         /*
          * The mpol_rebind_mm() call takes mmap_lock, which we couldn't
          * take while holding tasklist_lock.  Forks can happen - the
          * mpol_dup() cpuset_being_rebound check will catch such forks,
          * and rebind their vma mempolicies too.  Because we still hold
          * the global cpuset_mutex, we know that no other rebind effort
          * will be contending for the global variable cpuset_being_rebound.
          * It's ok if we rebind the same mm twice; mpol_rebind_mm()
          * is idempotent.  Also migrate pages in each mm to new nodes.
          */
         css_task_iter_start(&cs->css, 0, &it);
         while ((task = css_task_iter_next(&it))) {
                 struct mm_struct *mm;
                 bool migrate;
 
                 cpuset_change_task_nodemask(task, &newmems);
 
                 mm = get_task_mm(task);
                 if (!mm)
                         continue;
 
                 migrate = is_memory_migrate(cs);
 
                 mpol_rebind_mm(mm, &cs->mems_allowed);
                 if (migrate)
                         cpuset_migrate_mm(mm, &cs->old_mems_allowed, &newmems);
                 else
                         mmput(mm);
         }
         css_task_iter_end(&it);
 
         /*
          * All the tasks' nodemasks have been updated, update
          * cs->old_mems_allowed.
          */
         cs->old_mems_allowed = newmems;
 
         /* We're done rebinding vmas to this cpuset's new mems_allowed. */
         cpuset_being_rebound = NULL;
 }
 
 /*
  * update_nodemasks_hier - Update effective nodemasks and tasks in the subtree
  * @cs: the cpuset to consider
  * @new_mems: a temp variable for calculating new effective_mems
  *
  * When configured nodemask is changed, the effective nodemasks of this cpuset
  * and all its descendants need to be updated.
  *
  * On legacy hierarchy, effective_mems will be the same with mems_allowed.
  *
  * Called with cpuset_mutex held
  */
 static void update_nodemasks_hier(struct cpuset *cs, nodemask_t *new_mems)
 {
         struct cpuset *cp;
         struct cgroup_subsys_state *pos_css;
 
         rcu_read_lock();
         cpuset_for_each_descendant_pre(cp, pos_css, cs) {
                 struct cpuset *parent = parent_cs(cp);
 
                 nodes_and(*new_mems, cp->mems_allowed, parent->effective_mems);
 
                 /*
                  * If it becomes empty, inherit the effective mask of the
                  * parent, which is guaranteed to have some MEMs.
                  */
                 if (is_in_v2_mode() && nodes_empty(*new_mems))
                         *new_mems = parent->effective_mems;
 
                 /* Skip the whole subtree if the nodemask remains the same. */
                 if (nodes_equal(*new_mems, cp->effective_mems)) {
                         pos_css = css_rightmost_descendant(pos_css);
                         continue;
                 }
 
                 if (!css_tryget_online(&cp->css))
                         continue;
                 rcu_read_unlock();
 
                 spin_lock_irq(&callback_lock);
                 cp->effective_mems = *new_mems;
                 spin_unlock_irq(&callback_lock);
 
                 WARN_ON(!is_in_v2_mode() &&
                         !nodes_equal(cp->mems_allowed, cp->effective_mems));
 
                 update_tasks_nodemask(cp);
 
                 rcu_read_lock();
                 css_put(&cp->css);
         }
         rcu_read_unlock();
 }
 
 /*
  * Handle user request to change the 'mems' memory placement
  * of a cpuset.  Needs to validate the request, update the
  * cpusets mems_allowed, and for each task in the cpuset,
  * update mems_allowed and rebind task's mempolicy and any vma
  * mempolicies and if the cpuset is marked 'memory_migrate',
  * migrate the tasks pages to the new memory.
  *
  * Call with cpuset_mutex held. May take callback_lock during call.
  * Will take tasklist_lock, scan tasklist for tasks in cpuset cs,
  * lock each such tasks mm->mmap_lock, scan its vma's and rebind
  * their mempolicies to the cpusets new mems_allowed.
  */
 static int update_nodemask(struct cpuset *cs, struct cpuset *trialcs,
                            const char *buf)
 {
         int retval;
 
         /*
          * top_cpuset.mems_allowed tracks node_stats[N_MEMORY];
          * it's read-only
          */
         if (cs == &top_cpuset) {
                 retval = -EACCES;
                 goto done;
         }
 
         /*
          * An empty mems_allowed is ok iff there are no tasks in the cpuset.
          * Since nodelist_parse() fails on an empty mask, we special case
          * that parsing.  The validate_change() call ensures that cpusets
          * with tasks have memory.
          */
         if (!*buf) {
                 nodes_clear(trialcs->mems_allowed);
         } else {
                 retval = nodelist_parse(buf, trialcs->mems_allowed);
                 if (retval < 0)
                         goto done;
 
                 if (!nodes_subset(trialcs->mems_allowed,
                                   top_cpuset.mems_allowed)) {
                         retval = -EINVAL;
                         goto done;
                 }
         }
 
         if (nodes_equal(cs->mems_allowed, trialcs->mems_allowed)) {
                 retval = 0;             /* Too easy - nothing to do */
                 goto done;
         }
         retval = validate_change(cs, trialcs);
         if (retval < 0)
                 goto done;
 
         check_insane_mems_config(&trialcs->mems_allowed);
 
         spin_lock_irq(&callback_lock);
         cs->mems_allowed = trialcs->mems_allowed;
         spin_unlock_irq(&callback_lock);
 
         /* use trialcs->mems_allowed as a temp variable */
         update_nodemasks_hier(cs, &trialcs->mems_allowed);
 done:
         return retval;
 }
 
 bool current_cpuset_is_being_rebound(void)
 {
         bool ret;
 
         rcu_read_lock();
         ret = task_cs(current) == cpuset_being_rebound;
         rcu_read_unlock();
 
         return ret;
 }
 
 static int update_relax_domain_level(struct cpuset *cs, s64 val)
 {
 #ifdef CONFIG_SMP
         if (val < -1 || val > sched_domain_level_max + 1)
                 return -EINVAL;
 #endif
 
         if (val != cs->relax_domain_level) {
                 cs->relax_domain_level = val;
                 if (!cpumask_empty(cs->cpus_allowed) &&
                     is_sched_load_balance(cs))
                         rebuild_sched_domains_locked();
         }
 
         return 0;
 }
 
 /**
  * update_tasks_flags - update the spread flags of tasks in the cpuset.
  * @cs: the cpuset in which each task's spread flags needs to be changed
  *
  * Iterate through each task of @cs updating its spread flags.  As this
  * function is called with cpuset_mutex held, cpuset membership stays
  * stable.
  */
 static void update_tasks_flags(struct cpuset *cs)
 {
         struct css_task_iter it;
         struct task_struct *task;
 
         css_task_iter_start(&cs->css, 0, &it);
         while ((task = css_task_iter_next(&it)))
                 cpuset_update_task_spread_flags(cs, task);
         css_task_iter_end(&it);
 }
 
 /*
  * update_flag - read a 0 or a 1 in a file and update associated flag
  * bit:         the bit to update (see cpuset_flagbits_t)
  * cs:          the cpuset to update
  * turning_on:  whether the flag is being set or cleared
  *
  * Call with cpuset_mutex held.
  */
 
 static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
                        int turning_on)
 {
         struct cpuset *trialcs;
         int balance_flag_changed;
         int spread_flag_changed;
         int err;
 
         trialcs = alloc_trial_cpuset(cs);
         if (!trialcs)
                 return -ENOMEM;
 
         if (turning_on)
                 set_bit(bit, &trialcs->flags);
         else
                 clear_bit(bit, &trialcs->flags);
 
         err = validate_change(cs, trialcs);
         if (err < 0)
                 goto out;
 
         balance_flag_changed = (is_sched_load_balance(cs) !=
                                 is_sched_load_balance(trialcs));
 
         spread_flag_changed = ((is_spread_slab(cs) != is_spread_slab(trialcs))
                         || (is_spread_page(cs) != is_spread_page(trialcs)));
 
         spin_lock_irq(&callback_lock);
         cs->flags = trialcs->flags;
         spin_unlock_irq(&callback_lock);
 
         if (!cpumask_empty(trialcs->cpus_allowed) && balance_flag_changed)
                 rebuild_sched_domains_locked();
 
         if (spread_flag_changed)
                 update_tasks_flags(cs);
 out:
         free_cpuset(trialcs);
         return err;
 }
 
 /**
  * update_prstate - update partition_root_state
  * @cs: the cpuset to update
  * @new_prs: new partition root state
  * Return: 0 if successful, != 0 if error
  *
  * Call with cpuset_mutex held.
  */
 static int update_prstate(struct cpuset *cs, int new_prs)
 {
         int err = PERR_NONE, old_prs = cs->partition_root_state;
         struct cpuset *parent = parent_cs(cs);
         struct tmpmasks tmpmask;
         bool new_xcpus_state = false;
 
         if (old_prs == new_prs)
                 return 0;
 
         /*
          * Treat a previously invalid partition root as if it is a "member".
          */
         if (new_prs && is_prs_invalid(old_prs))
                 old_prs = PRS_MEMBER;
 
         if (alloc_cpumasks(NULL, &tmpmask))
                 return -ENOMEM;
 
         /*
          * Setup effective_xcpus if not properly set yet, it will be cleared
          * later if partition becomes invalid.
          */
         if ((new_prs > 0) && cpumask_empty(cs->exclusive_cpus)) {
                 spin_lock_irq(&callback_lock);
                 cpumask_and(cs->effective_xcpus,
                             cs->cpus_allowed, parent->effective_xcpus);
                 spin_unlock_irq(&callback_lock);
         }
 
         err = update_partition_exclusive(cs, new_prs);
         if (err)
                 goto out;
 
         if (!old_prs) {
                 enum partition_cmd cmd = (new_prs == PRS_ROOT)
                                        ? partcmd_enable : partcmd_enablei;
 
                 /*
                  * cpus_allowed and exclusive_cpus cannot be both empty.
                  */
                 if (xcpus_empty(cs)) {
                         err = PERR_CPUSEMPTY;
                         goto out;
                 }
 
                 err = update_parent_effective_cpumask(cs, cmd, NULL, &tmpmask);
                 /*
                  * If an attempt to become local partition root fails,
                  * try to become a remote partition root instead.
                  */
                 if (err && remote_partition_enable(cs, new_prs, &tmpmask))
                         err = 0;
         } else if (old_prs && new_prs) {
                 /*
                  * A change in load balance state only, no change in cpumasks.
                  */
                 new_xcpus_state = true;
         } else {
                 /*
                  * Switching back to member is always allowed even if it
                  * disables child partitions.
                  */
                 if (is_remote_partition(cs))
                         remote_partition_disable(cs, &tmpmask);
                 else
                         update_parent_effective_cpumask(cs, partcmd_disable,
                                                         NULL, &tmpmask);
 
                 /*
                  * Invalidation of child partitions will be done in
                  * update_cpumasks_hier().
                  */
         }
 out:
         /*
          * Make partition invalid & disable CS_CPU_EXCLUSIVE if an error
          * happens.
          */
         if (err) {
                 new_prs = -new_prs;
                 update_partition_exclusive(cs, new_prs);
         }
 
         spin_lock_irq(&callback_lock);
         cs->partition_root_state = new_prs;
         WRITE_ONCE(cs->prs_err, err);
         if (!is_partition_valid(cs))
                 reset_partition_data(cs);
         else if (new_xcpus_state)
                 partition_xcpus_newstate(old_prs, new_prs, cs->effective_xcpus);
         spin_unlock_irq(&callback_lock);
         update_unbound_workqueue_cpumask(new_xcpus_state);
 
         /* Force update if switching back to member */
         update_cpumasks_hier(cs, &tmpmask, !new_prs ? HIER_CHECKALL : 0);
 
         /* Update sched domains and load balance flag */
         update_partition_sd_lb(cs, old_prs);
 
         notify_partition_change(cs, old_prs);
         free_cpumasks(NULL, &tmpmask);
         return 0;
 }
 
 /*
  * Frequency meter - How fast is some event occurring?
  *
  * These routines manage a digitally filtered, constant time based,
  * event frequency meter.  There are four routines:
  *   fmeter_init() - initialize a frequency meter.
  *   fmeter_markevent() - called each time the event happens.
  *   fmeter_getrate() - returns the recent rate of such events.
  *   fmeter_update() - internal routine used to update fmeter.
  *
  * A common data structure is passed to each of these routines,
  * which is used to keep track of the state required to manage the
  * frequency meter and its digital filter.
  *
  * The filter works on the number of events marked per unit time.
  * The filter is single-pole low-pass recursive (IIR).  The time unit
  * is 1 second.  Arithmetic is done using 32-bit integers scaled to
  * simulate 3 decimal digits of precision (multiplied by 1000).
  *
  * With an FM_COEF of 933, and a time base of 1 second, the filter
  * has a half-life of 10 seconds, meaning that if the events quit
  * happening, then the rate returned from the fmeter_getrate()
  * will be cut in half each 10 seconds, until it converges to zero.
  *
  * It is not worth doing a real infinitely recursive filter.  If more
  * than FM_MAXTICKS ticks have elapsed since the last filter event,
  * just compute FM_MAXTICKS ticks worth, by which point the level
  * will be stable.
  *
  * Limit the count of unprocessed events to FM_MAXCNT, so as to avoid
  * arithmetic overflow in the fmeter_update() routine.
  *
  * Given the simple 32 bit integer arithmetic used, this meter works
  * best for reporting rates between one per millisecond (msec) and
  * one per 32 (approx) seconds.  At constant rates faster than one
  * per msec it maxes out at values just under 1,000,000.  At constant
  * rates between one per msec, and one per second it will stabilize
  * to a value N*1000, where N is the rate of events per second.
  * At constant rates between one per second and one per 32 seconds,
  * it will be choppy, moving up on the seconds that have an event,
  * and then decaying until the next event.  At rates slower than
  * about one in 32 seconds, it decays all the way back to zero between
  * each event.
  */
 
 #define FM_COEF 933             /* coefficient for half-life of 10 secs */
 #define FM_MAXTICKS ((u32)99)   /* useless computing more ticks than this */
 #define FM_MAXCNT 1000000       /* limit cnt to avoid overflow */
 #define FM_SCALE 1000           /* faux fixed point scale */
 
 /* Initialize a frequency meter */
 static void fmeter_init(struct fmeter *fmp)
 {
         fmp->cnt = 0;
         fmp->val = 0;
         fmp->time = 0;
         spin_lock_init(&fmp->lock);
 }
 
 /* Internal meter update - process cnt events and update value */
 static void fmeter_update(struct fmeter *fmp)
 {
         time64_t now;
         u32 ticks;
 
         now = ktime_get_seconds();
         ticks = now - fmp->time;
 
         if (ticks == 0)
                 return;
 
         ticks = min(FM_MAXTICKS, ticks);
         while (ticks-- > 0)
                 fmp->val = (FM_COEF * fmp->val) / FM_SCALE;
         fmp->time = now;
 
         fmp->val += ((FM_SCALE - FM_COEF) * fmp->cnt) / FM_SCALE;
         fmp->cnt = 0;
 }
 
 /* Process any previous ticks, then bump cnt by one (times scale). */
 static void fmeter_markevent(struct fmeter *fmp)
 {
         spin_lock(&fmp->lock);
         fmeter_update(fmp);
         fmp->cnt = min(FM_MAXCNT, fmp->cnt + FM_SCALE);
         spin_unlock(&fmp->lock);
 }
 
 /* Process any previous ticks, then return current value. */
 static int fmeter_getrate(struct fmeter *fmp)
 {
         int val;
 
         spin_lock(&fmp->lock);
         fmeter_update(fmp);
         val = fmp->val;
         spin_unlock(&fmp->lock);
         return val;
 }
 
 static struct cpuset *cpuset_attach_old_cs;
 
 /*
  * Check to see if a cpuset can accept a new task
  * For v1, cpus_allowed and mems_allowed can't be empty.
  * For v2, effective_cpus can't be empty.
  * Note that in v1, effective_cpus = cpus_allowed.
  */
 static int cpuset_can_attach_check(struct cpuset *cs)
 {
         if (cpumask_empty(cs->effective_cpus) ||
            (!is_in_v2_mode() && nodes_empty(cs->mems_allowed)))
                 return -ENOSPC;
         return 0;
 }
 
 static void reset_migrate_dl_data(struct cpuset *cs)
 {
         cs->nr_migrate_dl_tasks = 0;
         cs->sum_migrate_dl_bw = 0;
 }
 
 /* Called by cgroups to determine if a cpuset is usable; cpuset_mutex held */
 static int cpuset_can_attach(struct cgroup_taskset *tset)
 {
         struct cgroup_subsys_state *css;
         struct cpuset *cs, *oldcs;
         struct task_struct *task;
         bool cpus_updated, mems_updated;
         int ret;
 
         /* used later by cpuset_attach() */
         cpuset_attach_old_cs = task_cs(cgroup_taskset_first(tset, &css));
         oldcs = cpuset_attach_old_cs;
         cs = css_cs(css);
 
         mutex_lock(&cpuset_mutex);
 
         /* Check to see if task is allowed in the cpuset */
         ret = cpuset_can_attach_check(cs);
         if (ret)
                 goto out_unlock;
 
         cpus_updated = !cpumask_equal(cs->effective_cpus, oldcs->effective_cpus);
         mems_updated = !nodes_equal(cs->effective_mems, oldcs->effective_mems);
 
         cgroup_taskset_for_each(task, css, tset) {
                 ret = task_can_attach(task);
                 if (ret)
                         goto out_unlock;
 
                 /*
                  * Skip rights over task check in v2 when nothing changes,
                  * migration permission derives from hierarchy ownership in
                  * cgroup_procs_write_permission()).
                  */
                 if (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) ||
                     (cpus_updated || mems_updated)) {
                         ret = security_task_setscheduler(task);
                         if (ret)
                                 goto out_unlock;
                 }
 
                 if (dl_task(task)) {
                         cs->nr_migrate_dl_tasks++;
                         cs->sum_migrate_dl_bw += task->dl.dl_bw;
                 }
         }
 
         if (!cs->nr_migrate_dl_tasks)
                 goto out_success;
 
         if (!cpumask_intersects(oldcs->effective_cpus, cs->effective_cpus)) {
                 int cpu = cpumask_any_and(cpu_active_mask, cs->effective_cpus);
 
                 if (unlikely(cpu >= nr_cpu_ids)) {
                         reset_migrate_dl_data(cs);
                         ret = -EINVAL;
                         goto out_unlock;
                 }
 
                 ret = dl_bw_alloc(cpu, cs->sum_migrate_dl_bw);
                 if (ret) {
                         reset_migrate_dl_data(cs);
                         goto out_unlock;
                 }
         }
 
 out_success:
         /*
          * Mark attach is in progress.  This makes validate_change() fail
          * changes which zero cpus/mems_allowed.
          */
         cs->attach_in_progress++;
 out_unlock:
         mutex_unlock(&cpuset_mutex);
         return ret;
 }
 
 static void cpuset_cancel_attach(struct cgroup_taskset *tset)
 {
         struct cgroup_subsys_state *css;
         struct cpuset *cs;
 
         cgroup_taskset_first(tset, &css);
         cs = css_cs(css);
 
         mutex_lock(&cpuset_mutex);
         cs->attach_in_progress--;
         if (!cs->attach_in_progress)
                 wake_up(&cpuset_attach_wq);
 
         if (cs->nr_migrate_dl_tasks) {
                 int cpu = cpumask_any(cs->effective_cpus);
 
                 dl_bw_free(cpu, cs->sum_migrate_dl_bw);
                 reset_migrate_dl_data(cs);
         }
 
         mutex_unlock(&cpuset_mutex);
 }
 
 /*
  * Protected by cpuset_mutex. cpus_attach is used only by cpuset_attach_task()
  * but we can't allocate it dynamically there.  Define it global and
  * allocate from cpuset_init().
  */
 static cpumask_var_t cpus_attach;
 static nodemask_t cpuset_attach_nodemask_to;
 
 static void cpuset_attach_task(struct cpuset *cs, struct task_struct *task)
 {
         lockdep_assert_held(&cpuset_mutex);
 
         if (cs != &top_cpuset)
                 guarantee_online_cpus(task, cpus_attach);
         else
                 cpumask_andnot(cpus_attach, task_cpu_possible_mask(task),
                                subpartitions_cpus);
         /*
          * can_attach beforehand should guarantee that this doesn't
          * fail.  TODO: have a better way to handle failure here
          */
         WARN_ON_ONCE(set_cpus_allowed_ptr(task, cpus_attach));
 
         cpuset_change_task_nodemask(task, &cpuset_attach_nodemask_to);
         cpuset_update_task_spread_flags(cs, task);
 }
 
 static void cpuset_attach(struct cgroup_taskset *tset)
 {
         struct task_struct *task;
         struct task_struct *leader;
         struct cgroup_subsys_state *css;
         struct cpuset *cs;
         struct cpuset *oldcs = cpuset_attach_old_cs;
         bool cpus_updated, mems_updated;
 
         cgroup_taskset_first(tset, &css);
         cs = css_cs(css);
 
         lockdep_assert_cpus_held();     /* see cgroup_attach_lock() */
         mutex_lock(&cpuset_mutex);
         cpus_updated = !cpumask_equal(cs->effective_cpus,
                                       oldcs->effective_cpus);
         mems_updated = !nodes_equal(cs->effective_mems, oldcs->effective_mems);
 
         /*
          * In the default hierarchy, enabling cpuset in the child cgroups
          * will trigger a number of cpuset_attach() calls with no change
          * in effective cpus and mems. In that case, we can optimize out
          * by skipping the task iteration and update.
          */
         if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
             !cpus_updated && !mems_updated) {
                 cpuset_attach_nodemask_to = cs->effective_mems;
                 goto out;
         }
 
         guarantee_online_mems(cs, &cpuset_attach_nodemask_to);
 
         cgroup_taskset_for_each(task, css, tset)
                 cpuset_attach_task(cs, task);
 
         /*
          * Change mm for all threadgroup leaders. This is expensive and may
          * sleep and should be moved outside migration path proper. Skip it
          * if there is no change in effective_mems and CS_MEMORY_MIGRATE is
          * not set.
          */
         cpuset_attach_nodemask_to = cs->effective_mems;
         if (!is_memory_migrate(cs) && !mems_updated)
                 goto out;
 
         cgroup_taskset_for_each_leader(leader, css, tset) {
                 struct mm_struct *mm = get_task_mm(leader);
 
                 if (mm) {
                         mpol_rebind_mm(mm, &cpuset_attach_nodemask_to);
 
                         /*
                          * old_mems_allowed is the same with mems_allowed
                          * here, except if this task is being moved
                          * automatically due to hotplug.  In that case
                          * @mems_allowed has been updated and is empty, so
                          * @old_mems_allowed is the right nodesets that we
                          * migrate mm from.
                          */
                         if (is_memory_migrate(cs))
                                 cpuset_migrate_mm(mm, &oldcs->old_mems_allowed,
                                                   &cpuset_attach_nodemask_to);
                         else
                                 mmput(mm);
                 }
         }
 
 out:
         cs->old_mems_allowed = cpuset_attach_nodemask_to;
 
         if (cs->nr_migrate_dl_tasks) {
                 cs->nr_deadline_tasks += cs->nr_migrate_dl_tasks;
                 oldcs->nr_deadline_tasks -= cs->nr_migrate_dl_tasks;
                 reset_migrate_dl_data(cs);
         }
 
         cs->attach_in_progress--;
         if (!cs->attach_in_progress)
                 wake_up(&cpuset_attach_wq);
 
         mutex_unlock(&cpuset_mutex);
 }
 
 /* The various types of files and directories in a cpuset file system */
 
 typedef enum {
         FILE_MEMORY_MIGRATE,
         FILE_CPULIST,
         FILE_MEMLIST,
         FILE_EFFECTIVE_CPULIST,
         FILE_EFFECTIVE_MEMLIST,
         FILE_SUBPARTS_CPULIST,
         FILE_EXCLUSIVE_CPULIST,
         FILE_EFFECTIVE_XCPULIST,
         FILE_ISOLATED_CPULIST,
         FILE_CPU_EXCLUSIVE,
         FILE_MEM_EXCLUSIVE,
         FILE_MEM_HARDWALL,
         FILE_SCHED_LOAD_BALANCE,
         FILE_PARTITION_ROOT,
         FILE_SCHED_RELAX_DOMAIN_LEVEL,
         FILE_MEMORY_PRESSURE_ENABLED,
         FILE_MEMORY_PRESSURE,
         FILE_SPREAD_PAGE,
         FILE_SPREAD_SLAB,
 } cpuset_filetype_t;
 
 static int cpuset_write_u64(struct cgroup_subsys_state *css, struct cftype *cft,
                             u64 val)
 {
         struct cpuset *cs = css_cs(css);
         cpuset_filetype_t type = cft->private;
         int retval = 0;
 
         cpus_read_lock();
         mutex_lock(&cpuset_mutex);
         if (!is_cpuset_online(cs)) {
                 retval = -ENODEV;
                 goto out_unlock;
         }
 
         switch (type) {
         case FILE_CPU_EXCLUSIVE:
                 retval = update_flag(CS_CPU_EXCLUSIVE, cs, val);
                 break;
         case FILE_MEM_EXCLUSIVE:
                 retval = update_flag(CS_MEM_EXCLUSIVE, cs, val);
                 break;
         case FILE_MEM_HARDWALL:
                 retval = update_flag(CS_MEM_HARDWALL, cs, val);
                 break;
         case FILE_SCHED_LOAD_BALANCE:
                 retval = update_flag(CS_SCHED_LOAD_BALANCE, cs, val);
                 break;
         case FILE_MEMORY_MIGRATE:
                 retval = update_flag(CS_MEMORY_MIGRATE, cs, val);
                 break;
         case FILE_MEMORY_PRESSURE_ENABLED:
                 cpuset_memory_pressure_enabled = !!val;
                 break;
         case FILE_SPREAD_PAGE:
                 retval = update_flag(CS_SPREAD_PAGE, cs, val);
                 break;
         case FILE_SPREAD_SLAB:
                 retval = update_flag(CS_SPREAD_SLAB, cs, val);
                 break;
         default:
                 retval = -EINVAL;
                 break;
         }
 out_unlock:
         mutex_unlock(&cpuset_mutex);
         cpus_read_unlock();
         return retval;
 }
 
 static int cpuset_write_s64(struct cgroup_subsys_state *css, struct cftype *cft,
                             s64 val)
 {
         struct cpuset *cs = css_cs(css);
         cpuset_filetype_t type = cft->private;
         int retval = -ENODEV;
 
         cpus_read_lock();
         mutex_lock(&cpuset_mutex);
         if (!is_cpuset_online(cs))
                 goto out_unlock;
 
         switch (type) {
         case FILE_SCHED_RELAX_DOMAIN_LEVEL:
                 retval = update_relax_domain_level(cs, val);
                 break;
         default:
                 retval = -EINVAL;
                 break;
         }
 out_unlock:
         mutex_unlock(&cpuset_mutex);
         cpus_read_unlock();
         return retval;
 }
 
 /*
  * Common handling for a write to a "cpus" or "mems" file.
  */
 static ssize_t cpuset_write_resmask(struct kernfs_open_file *of,
                                     char *buf, size_t nbytes, loff_t off)
 {
         struct cpuset *cs = css_cs(of_css(of));
         struct cpuset *trialcs;
         int retval = -ENODEV;
 
         buf = strstrip(buf);
 
         /*
          * CPU or memory hotunplug may leave @cs w/o any execution
          * resources, in which case the hotplug code asynchronously updates
          * configuration and transfers all tasks to the nearest ancestor
          * which can execute.
          *
          * As writes to "cpus" or "mems" may restore @cs's execution
          * resources, wait for the previously scheduled operations before
          * proceeding, so that we don't end up keep removing tasks added
          * after execution capability is restored.
          *
          * cpuset_handle_hotplug may call back into cgroup core asynchronously
          * via cgroup_transfer_tasks() and waiting for it from a cgroupfs
          * operation like this one can lead to a deadlock through kernfs
          * active_ref protection.  Let's break the protection.  Losing the
          * protection is okay as we check whether @cs is online after
          * grabbing cpuset_mutex anyway.  This only happens on the legacy
          * hierarchies.
          */
         css_get(&cs->css);
         kernfs_break_active_protection(of->kn);
 
         cpus_read_lock();
         mutex_lock(&cpuset_mutex);
         if (!is_cpuset_online(cs))
                 goto out_unlock;
 
         trialcs = alloc_trial_cpuset(cs);
         if (!trialcs) {
                 retval = -ENOMEM;
                 goto out_unlock;
         }
 
         switch (of_cft(of)->private) {
         case FILE_CPULIST:
                 retval = update_cpumask(cs, trialcs, buf);
                 break;
         case FILE_EXCLUSIVE_CPULIST:
                 retval = update_exclusive_cpumask(cs, trialcs, buf);
                 break;
         case FILE_MEMLIST:
                 retval = update_nodemask(cs, trialcs, buf);
                 break;
         default:
                 retval = -EINVAL;
                 break;
         }
 
         free_cpuset(trialcs);
 out_unlock:
         mutex_unlock(&cpuset_mutex);
         cpus_read_unlock();
         kernfs_unbreak_active_protection(of->kn);
         css_put(&cs->css);
         flush_workqueue(cpuset_migrate_mm_wq);
         return retval ?: nbytes;
 }
 
 /*
  * These ascii lists should be read in a single call, by using a user
  * buffer large enough to hold the entire map.  If read in smaller
  * chunks, there is no guarantee of atomicity.  Since the display format
  * used, list of ranges of sequential numbers, is variable length,
  * and since these maps can change value dynamically, one could read
  * gibberish by doing partial reads while a list was changing.
  */
 static int cpuset_common_seq_show(struct seq_file *sf, void *v)
 {
         struct cpuset *cs = css_cs(seq_css(sf));
         cpuset_filetype_t type = seq_cft(sf)->private;
         int ret = 0;
 
         spin_lock_irq(&callback_lock);
 
         switch (type) {
         case FILE_CPULIST:
                 seq_printf(sf, "%*pbl\n", cpumask_pr_args(cs->cpus_allowed));
                 break;
         case FILE_MEMLIST:
                 seq_printf(sf, "%*pbl\n", nodemask_pr_args(&cs->mems_allowed));
                 break;
         case FILE_EFFECTIVE_CPULIST:
                 seq_printf(sf, "%*pbl\n", cpumask_pr_args(cs->effective_cpus));
                 break;
         case FILE_EFFECTIVE_MEMLIST:
                 seq_printf(sf, "%*pbl\n", nodemask_pr_args(&cs->effective_mems));
                 break;
         case FILE_EXCLUSIVE_CPULIST:
                 seq_printf(sf, "%*pbl\n", cpumask_pr_args(cs->exclusive_cpus));
                 break;
         case FILE_EFFECTIVE_XCPULIST:
                 seq_printf(sf, "%*pbl\n", cpumask_pr_args(cs->effective_xcpus));
                 break;
         case FILE_SUBPARTS_CPULIST:
                 seq_printf(sf, "%*pbl\n", cpumask_pr_args(subpartitions_cpus));
                 break;
         case FILE_ISOLATED_CPULIST:
                 seq_printf(sf, "%*pbl\n", cpumask_pr_args(isolated_cpus));
                 break;
         default:
                 ret = -EINVAL;
         }
 
         spin_unlock_irq(&callback_lock);
         return ret;
 }
 
 static u64 cpuset_read_u64(struct cgroup_subsys_state *css, struct cftype *cft)
 {
         struct cpuset *cs = css_cs(css);
         cpuset_filetype_t type = cft->private;
         switch (type) {
         case FILE_CPU_EXCLUSIVE:
                 return is_cpu_exclusive(cs);
         case FILE_MEM_EXCLUSIVE:
                 return is_mem_exclusive(cs);
         case FILE_MEM_HARDWALL:
                 return is_mem_hardwall(cs);
         case FILE_SCHED_LOAD_BALANCE:
                 return is_sched_load_balance(cs);
         case FILE_MEMORY_MIGRATE:
                 return is_memory_migrate(cs);
         case FILE_MEMORY_PRESSURE_ENABLED:
                 return cpuset_memory_pressure_enabled;
         case FILE_MEMORY_PRESSURE:
                 return fmeter_getrate(&cs->fmeter);
         case FILE_SPREAD_PAGE:
                 return is_spread_page(cs);
         case FILE_SPREAD_SLAB:
                 return is_spread_slab(cs);
         default:
                 BUG();
         }
 
         /* Unreachable but makes gcc happy */
         return 0;
 }
 
 static s64 cpuset_read_s64(struct cgroup_subsys_state *css, struct cftype *cft)
 {
         struct cpuset *cs = css_cs(css);
         cpuset_filetype_t type = cft->private;
         switch (type) {
         case FILE_SCHED_RELAX_DOMAIN_LEVEL:
                 return cs->relax_domain_level;
         default:
                 BUG();
         }
 
         /* Unreachable but makes gcc happy */
         return 0;
 }
 
 static int sched_partition_show(struct seq_file *seq, void *v)
 {
         struct cpuset *cs = css_cs(seq_css(seq));
         const char *err, *type = NULL;
 
         switch (cs->partition_root_state) {
         case PRS_ROOT:
                 seq_puts(seq, "root\n");
                 break;
         case PRS_ISOLATED:
                 seq_puts(seq, "isolated\n");
                 break;
         case PRS_MEMBER:
                 seq_puts(seq, "member\n");
                 break;
         case PRS_INVALID_ROOT:
                 type = "root";
                 fallthrough;
         case PRS_INVALID_ISOLATED:
                 if (!type)
                         type = "isolated";
                 err = perr_strings[READ_ONCE(cs->prs_err)];
                 if (err)
                         seq_printf(seq, "%s invalid (%s)\n", type, err);
                 else
                         seq_printf(seq, "%s invalid\n", type);
                 break;
         }
         return 0;
 }
 
 static ssize_t sched_partition_write(struct kernfs_open_file *of, char *buf,
                                      size_t nbytes, loff_t off)
 {
         struct cpuset *cs = css_cs(of_css(of));
         int val;
         int retval = -ENODEV;
 
         buf = strstrip(buf);
 
         if (!strcmp(buf, "root"))
                 val = PRS_ROOT;
         else if (!strcmp(buf, "member"))
                 val = PRS_MEMBER;
         else if (!strcmp(buf, "isolated"))
                 val = PRS_ISOLATED;
         else
                 return -EINVAL;
 
         css_get(&cs->css);
         cpus_read_lock();
         mutex_lock(&cpuset_mutex);
         if (!is_cpuset_online(cs))
                 goto out_unlock;
 
         retval = update_prstate(cs, val);
 out_unlock:
         mutex_unlock(&cpuset_mutex);
         cpus_read_unlock();
         css_put(&cs->css);
         return retval ?: nbytes;
 }
 
 /*
  * for the common functions, 'private' gives the type of file
  */
 
 static struct cftype legacy_files[] = {
         {
                 .name = "cpus",
                 .seq_show = cpuset_common_seq_show,
                 .write = cpuset_write_resmask,
                 .max_write_len = (100U + 6 * NR_CPUS),
                 .private = FILE_CPULIST,
         },
 
         {
                 .name = "mems",
                 .seq_show = cpuset_common_seq_show,
                 .write = cpuset_write_resmask,
                 .max_write_len = (100U + 6 * MAX_NUMNODES),
                 .private = FILE_MEMLIST,
         },
 
         {
                 .name = "effective_cpus",
                 .seq_show = cpuset_common_seq_show,
                 .private = FILE_EFFECTIVE_CPULIST,
         },
 
         {
                 .name = "effective_mems",
                 .seq_show = cpuset_common_seq_show,
                 .private = FILE_EFFECTIVE_MEMLIST,
         },
 
         {
                 .name = "cpu_exclusive",
                 .read_u64 = cpuset_read_u64,
                 .write_u64 = cpuset_write_u64,
                 .private = FILE_CPU_EXCLUSIVE,
         },
 
         {
                 .name = "mem_exclusive",
                 .read_u64 = cpuset_read_u64,
                 .write_u64 = cpuset_write_u64,
                 .private = FILE_MEM_EXCLUSIVE,
         },
 
         {
                 .name = "mem_hardwall",
                 .read_u64 = cpuset_read_u64,
                 .write_u64 = cpuset_write_u64,
                 .private = FILE_MEM_HARDWALL,
         },
 
         {
                 .name = "sched_load_balance",
                 .read_u64 = cpuset_read_u64,
                 .write_u64 = cpuset_write_u64,
                 .private = FILE_SCHED_LOAD_BALANCE,
         },
 
         {
                 .name = "sched_relax_domain_level",
                 .read_s64 = cpuset_read_s64,
                 .write_s64 = cpuset_write_s64,
                 .private = FILE_SCHED_RELAX_DOMAIN_LEVEL,
         },
 
         {
                 .name = "memory_migrate",
                 .read_u64 = cpuset_read_u64,
                 .write_u64 = cpuset_write_u64,
                 .private = FILE_MEMORY_MIGRATE,
         },
 
         {
                 .name = "memory_pressure",
                 .read_u64 = cpuset_read_u64,
                 .private = FILE_MEMORY_PRESSURE,
         },
 
         {
                 .name = "memory_spread_page",
                 .read_u64 = cpuset_read_u64,
                 .write_u64 = cpuset_write_u64,
                 .private = FILE_SPREAD_PAGE,
         },
 
         {
                 /* obsolete, may be removed in the future */
                 .name = "memory_spread_slab",
                 .read_u64 = cpuset_read_u64,
                 .write_u64 = cpuset_write_u64,
                 .private = FILE_SPREAD_SLAB,
         },
 
         {
                 .name = "memory_pressure_enabled",
                 .flags = CFTYPE_ONLY_ON_ROOT,
                 .read_u64 = cpuset_read_u64,
                 .write_u64 = cpuset_write_u64,
                 .private = FILE_MEMORY_PRESSURE_ENABLED,
         },
 
         { }     /* terminate */
 };
 
 /*
  * This is currently a minimal set for the default hierarchy. It can be
  * expanded later on by migrating more features and control files from v1.
  */
 static struct cftype dfl_files[] = {
         {
                 .name = "cpus",
                 .seq_show = cpuset_common_seq_show,
                 .write = cpuset_write_resmask,
                 .max_write_len = (100U + 6 * NR_CPUS),
                 .private = FILE_CPULIST,
                 .flags = CFTYPE_NOT_ON_ROOT,
         },
 
         {
                 .name = "mems",
                 .seq_show = cpuset_common_seq_show,
                 .write = cpuset_write_resmask,
                 .max_write_len = (100U + 6 * MAX_NUMNODES),
                 .private = FILE_MEMLIST,
                 .flags = CFTYPE_NOT_ON_ROOT,
         },
 
         {
                 .name = "cpus.effective",
                 .seq_show = cpuset_common_seq_show,
                 .private = FILE_EFFECTIVE_CPULIST,
         },
 
         {
                 .name = "mems.effective",
                 .seq_show = cpuset_common_seq_show,
                 .private = FILE_EFFECTIVE_MEMLIST,
         },
 
         {
                 .name = "cpus.partition",
                 .seq_show = sched_partition_show,
                 .write = sched_partition_write,
                 .private = FILE_PARTITION_ROOT,
                 .flags = CFTYPE_NOT_ON_ROOT,
                 .file_offset = offsetof(struct cpuset, partition_file),
         },
 
         {
                 .name = "cpus.exclusive",
                 .seq_show = cpuset_common_seq_show,
                 .write = cpuset_write_resmask,
                 .max_write_len = (100U + 6 * NR_CPUS),
                 .private = FILE_EXCLUSIVE_CPULIST,
                 .flags = CFTYPE_NOT_ON_ROOT,
         },
 
         {
                 .name = "cpus.exclusive.effective",
                 .seq_show = cpuset_common_seq_show,
                 .private = FILE_EFFECTIVE_XCPULIST,
                 .flags = CFTYPE_NOT_ON_ROOT,
         },
 
         {
                 .name = "cpus.subpartitions",
                 .seq_show = cpuset_common_seq_show,
                 .private = FILE_SUBPARTS_CPULIST,
                 .flags = CFTYPE_ONLY_ON_ROOT | CFTYPE_DEBUG,
         },
 
         {
                 .name = "cpus.isolated",
                 .seq_show = cpuset_common_seq_show,
                 .private = FILE_ISOLATED_CPULIST,
                 .flags = CFTYPE_ONLY_ON_ROOT,
         },
 
         { }     /* terminate */
 };
 
 
 /**
  * cpuset_css_alloc - Allocate a cpuset css
  * @parent_css: Parent css of the control group that the new cpuset will be
  *              part of
  * Return: cpuset css on success, -ENOMEM on failure.
  *
  * Allocate and initialize a new cpuset css, for non-NULL @parent_css, return
  * top cpuset css otherwise.
  */
 static struct cgroup_subsys_state *
 cpuset_css_alloc(struct cgroup_subsys_state *parent_css)
 {
         struct cpuset *cs;
 
         if (!parent_css)
                 return &top_cpuset.css;
 
         cs = kzalloc(sizeof(*cs), GFP_KERNEL);
         if (!cs)
                 return ERR_PTR(-ENOMEM);
 
         if (alloc_cpumasks(cs, NULL)) {
                 kfree(cs);
                 return ERR_PTR(-ENOMEM);
         }
 
         __set_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
         fmeter_init(&cs->fmeter);
         cs->relax_domain_level = -1;
         INIT_LIST_HEAD(&cs->remote_sibling);
 
         /* Set CS_MEMORY_MIGRATE for default hierarchy */
         if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys))
                 __set_bit(CS_MEMORY_MIGRATE, &cs->flags);
 
         return &cs->css;
 }
 
 static int cpuset_css_online(struct cgroup_subsys_state *css)
 {
         struct cpuset *cs = css_cs(css);
         struct cpuset *parent = parent_cs(cs);
         struct cpuset *tmp_cs;
         struct cgroup_subsys_state *pos_css;
 
         if (!parent)
                 return 0;
 
         cpus_read_lock();
         mutex_lock(&cpuset_mutex);
 
         set_bit(CS_ONLINE, &cs->flags);
         if (is_spread_page(parent))
                 set_bit(CS_SPREAD_PAGE, &cs->flags);
         if (is_spread_slab(parent))
                 set_bit(CS_SPREAD_SLAB, &cs->flags);
         /*
          * For v2, clear CS_SCHED_LOAD_BALANCE if parent is isolated
          */
         if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
             !is_sched_load_balance(parent))
                 clear_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
 
         cpuset_inc();
 
         spin_lock_irq(&callback_lock);
         if (is_in_v2_mode()) {
                 cpumask_copy(cs->effective_cpus, parent->effective_cpus);
                 cs->effective_mems = parent->effective_mems;
                 cs->use_parent_ecpus = true;
                 parent->child_ecpus_count++;
         }
         spin_unlock_irq(&callback_lock);
 
         if (!test_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags))
                 goto out_unlock;
 
         /*
          * Clone @parent's configuration if CGRP_CPUSET_CLONE_CHILDREN is
          * set.  This flag handling is implemented in cgroup core for
          * historical reasons - the flag may be specified during mount.
          *
          * Currently, if any sibling cpusets have exclusive cpus or mem, we
          * refuse to clone the configuration - thereby refusing the task to
          * be entered, and as a result refusing the sys_unshare() or
          * clone() which initiated it.  If this becomes a problem for some
          * users who wish to allow that scenario, then this could be
          * changed to grant parent->cpus_allowed-sibling_cpus_exclusive
          * (and likewise for mems) to the new cgroup.
          */
         rcu_read_lock();
         cpuset_for_each_child(tmp_cs, pos_css, parent) {
                 if (is_mem_exclusive(tmp_cs) || is_cpu_exclusive(tmp_cs)) {
                         rcu_read_unlock();
                         goto out_unlock;
                 }
         }
         rcu_read_unlock();
 
         spin_lock_irq(&callback_lock);
         cs->mems_allowed = parent->mems_allowed;
         cs->effective_mems = parent->mems_allowed;
         cpumask_copy(cs->cpus_allowed, parent->cpus_allowed);
         cpumask_copy(cs->effective_cpus, parent->cpus_allowed);
         spin_unlock_irq(&callback_lock);
 out_unlock:
         mutex_unlock(&cpuset_mutex);
         cpus_read_unlock();
         return 0;
 }
 
 /*
  * If the cpuset being removed has its flag 'sched_load_balance'
  * enabled, then simulate turning sched_load_balance off, which
  * will call rebuild_sched_domains_locked(). That is not needed
  * in the default hierarchy where only changes in partition
  * will cause repartitioning.
  *
  * If the cpuset has the 'sched.partition' flag enabled, simulate
  * turning 'sched.partition" off.
  */
 
 static void cpuset_css_offline(struct cgroup_subsys_state *css)
 {
         struct cpuset *cs = css_cs(css);
 
         cpus_read_lock();
         mutex_lock(&cpuset_mutex);
 
         if (is_partition_valid(cs))
                 update_prstate(cs, 0);
 
         if (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
             is_sched_load_balance(cs))
                 update_flag(CS_SCHED_LOAD_BALANCE, cs, 0);
 
         if (cs->use_parent_ecpus) {
                 struct cpuset *parent = parent_cs(cs);
 
                 cs->use_parent_ecpus = false;
                 parent->child_ecpus_count--;
         }
 
         cpuset_dec();
         clear_bit(CS_ONLINE, &cs->flags);
 
         mutex_unlock(&cpuset_mutex);
         cpus_read_unlock();
 }
 
 static void cpuset_css_free(struct cgroup_subsys_state *css)
 {
         struct cpuset *cs = css_cs(css);
 
         free_cpuset(cs);
 }
 
 static void cpuset_bind(struct cgroup_subsys_state *root_css)
 {
         mutex_lock(&cpuset_mutex);
         spin_lock_irq(&callback_lock);
 
         if (is_in_v2_mode()) {
                 cpumask_copy(top_cpuset.cpus_allowed, cpu_possible_mask);
                 cpumask_copy(top_cpuset.effective_xcpus, cpu_possible_mask);
                 top_cpuset.mems_allowed = node_possible_map;
         } else {
                 cpumask_copy(top_cpuset.cpus_allowed,
                              top_cpuset.effective_cpus);
                 top_cpuset.mems_allowed = top_cpuset.effective_mems;
         }
 
         spin_unlock_irq(&callback_lock);
         mutex_unlock(&cpuset_mutex);
 }
 
 /*
  * In case the child is cloned into a cpuset different from its parent,
  * additional checks are done to see if the move is allowed.
  */
 static int cpuset_can_fork(struct task_struct *task, struct css_set *cset)
 {
         struct cpuset *cs = css_cs(cset->subsys[cpuset_cgrp_id]);
         bool same_cs;
         int ret;
 
         rcu_read_lock();
         same_cs = (cs == task_cs(current));
         rcu_read_unlock();
 
         if (same_cs)
                 return 0;
 
         lockdep_assert_held(&cgroup_mutex);
         mutex_lock(&cpuset_mutex);
 
         /* Check to see if task is allowed in the cpuset */
         ret = cpuset_can_attach_check(cs);
         if (ret)
                 goto out_unlock;
 
         ret = task_can_attach(task);
         if (ret)
                 goto out_unlock;
 
         ret = security_task_setscheduler(task);
         if (ret)
                 goto out_unlock;
 
         /*
          * Mark attach is in progress.  This makes validate_change() fail
          * changes which zero cpus/mems_allowed.
          */
         cs->attach_in_progress++;
 out_unlock:
         mutex_unlock(&cpuset_mutex);
         return ret;
 }
 
 static void cpuset_cancel_fork(struct task_struct *task, struct css_set *cset)
 {
         struct cpuset *cs = css_cs(cset->subsys[cpuset_cgrp_id]);
         bool same_cs;
 
         rcu_read_lock();
         same_cs = (cs == task_cs(current));
         rcu_read_unlock();
 
         if (same_cs)
                 return;
 
         mutex_lock(&cpuset_mutex);
         cs->attach_in_progress--;
         if (!cs->attach_in_progress)
                 wake_up(&cpuset_attach_wq);
         mutex_unlock(&cpuset_mutex);
 }
 
 /*
  * Make sure the new task conform to the current state of its parent,
  * which could have been changed by cpuset just after it inherits the
  * state from the parent and before it sits on the cgroup's task list.
  */
 static void cpuset_fork(struct task_struct *task)
 {
         struct cpuset *cs;
         bool same_cs;
 
         rcu_read_lock();
         cs = task_cs(task);
         same_cs = (cs == task_cs(current));
         rcu_read_unlock();
 
         if (same_cs) {
                 if (cs == &top_cpuset)
                         return;
 
                 set_cpus_allowed_ptr(task, current->cpus_ptr);
                 task->mems_allowed = current->mems_allowed;
                 return;
         }
 
         /* CLONE_INTO_CGROUP */
         mutex_lock(&cpuset_mutex);
         guarantee_online_mems(cs, &cpuset_attach_nodemask_to);
         cpuset_attach_task(cs, task);
 
         cs->attach_in_progress--;
         if (!cs->attach_in_progress)
                 wake_up(&cpuset_attach_wq);
 
         mutex_unlock(&cpuset_mutex);
 }
 
 struct cgroup_subsys cpuset_cgrp_subsys = {
         .css_alloc      = cpuset_css_alloc,
         .css_online     = cpuset_css_online,
         .css_offline    = cpuset_css_offline,
         .css_free       = cpuset_css_free,
         .can_attach     = cpuset_can_attach,
         .cancel_attach  = cpuset_cancel_attach,
         .attach         = cpuset_attach,
         .post_attach    = cpuset_post_attach,
         .bind           = cpuset_bind,
         .can_fork       = cpuset_can_fork,
         .cancel_fork    = cpuset_cancel_fork,
         .fork           = cpuset_fork,
         .legacy_cftypes = legacy_files,
         .dfl_cftypes    = dfl_files,
         .early_init     = true,
         .threaded       = true,
 };
 
 /**
  * cpuset_init - initialize cpusets at system boot
  *
  * Description: Initialize top_cpuset
  **/
 
 int __init cpuset_init(void)
 {
         BUG_ON(!alloc_cpumask_var(&top_cpuset.cpus_allowed, GFP_KERNEL));
         BUG_ON(!alloc_cpumask_var(&top_cpuset.effective_cpus, GFP_KERNEL));
         BUG_ON(!alloc_cpumask_var(&top_cpuset.effective_xcpus, GFP_KERNEL));
         BUG_ON(!alloc_cpumask_var(&top_cpuset.exclusive_cpus, GFP_KERNEL));
         BUG_ON(!zalloc_cpumask_var(&subpartitions_cpus, GFP_KERNEL));
         BUG_ON(!zalloc_cpumask_var(&isolated_cpus, GFP_KERNEL));
 
         cpumask_setall(top_cpuset.cpus_allowed);
         nodes_setall(top_cpuset.mems_allowed);
         cpumask_setall(top_cpuset.effective_cpus);
         cpumask_setall(top_cpuset.effective_xcpus);
         cpumask_setall(top_cpuset.exclusive_cpus);
         nodes_setall(top_cpuset.effective_mems);
 
         fmeter_init(&top_cpuset.fmeter);
         INIT_LIST_HEAD(&remote_children);
 
         BUG_ON(!alloc_cpumask_var(&cpus_attach, GFP_KERNEL));
 
         return 0;
 }
 
 /*
  * If CPU and/or memory hotplug handlers, below, unplug any CPUs
  * or memory nodes, we need to walk over the cpuset hierarchy,
  * removing that CPU or node from all cpusets.  If this removes the
  * last CPU or node from a cpuset, then move the tasks in the empty
  * cpuset to its next-highest non-empty parent.
  */
 static void remove_tasks_in_empty_cpuset(struct cpuset *cs)
 {
         struct cpuset *parent;
 
         /*
          * Find its next-highest non-empty parent, (top cpuset
          * has online cpus, so can't be empty).
          */
         parent = parent_cs(cs);
         while (cpumask_empty(parent->cpus_allowed) ||
                         nodes_empty(parent->mems_allowed))
                 parent = parent_cs(parent);
 
         if (cgroup_transfer_tasks(parent->css.cgroup, cs->css.cgroup)) {
                 pr_err("cpuset: failed to transfer tasks out of empty cpuset ");
                 pr_cont_cgroup_name(cs->css.cgroup);
                 pr_cont("\n");
         }
 }
 
 static void cpuset_migrate_tasks_workfn(struct work_struct *work)
 {
         struct cpuset_remove_tasks_struct *s;
 
         s = container_of(work, struct cpuset_remove_tasks_struct, work);
         remove_tasks_in_empty_cpuset(s->cs);
         css_put(&s->cs->css);
         kfree(s);
 }
 
 static void
 hotplug_update_tasks_legacy(struct cpuset *cs,
                             struct cpumask *new_cpus, nodemask_t *new_mems,
                             bool cpus_updated, bool mems_updated)
 {
         bool is_empty;
 
         spin_lock_irq(&callback_lock);
         cpumask_copy(cs->cpus_allowed, new_cpus);
         cpumask_copy(cs->effective_cpus, new_cpus);
         cs->mems_allowed = *new_mems;
         cs->effective_mems = *new_mems;
         spin_unlock_irq(&callback_lock);
 
         /*
          * Don't call update_tasks_cpumask() if the cpuset becomes empty,
          * as the tasks will be migrated to an ancestor.
          */
         if (cpus_updated && !cpumask_empty(cs->cpus_allowed))
                 update_tasks_cpumask(cs, new_cpus);
         if (mems_updated && !nodes_empty(cs->mems_allowed))
                 update_tasks_nodemask(cs);
 
         is_empty = cpumask_empty(cs->cpus_allowed) ||
                    nodes_empty(cs->mems_allowed);
 
         /*
          * Move tasks to the nearest ancestor with execution resources,
          * This is full cgroup operation which will also call back into
          * cpuset. Execute it asynchronously using workqueue.
          */
         if (is_empty && cs->css.cgroup->nr_populated_csets &&
             css_tryget_online(&cs->css)) {
                 struct cpuset_remove_tasks_struct *s;
 
                 s = kzalloc(sizeof(*s), GFP_KERNEL);
                 if (WARN_ON_ONCE(!s)) {
                         css_put(&cs->css);
                         return;
                 }
 
                 s->cs = cs;
                 INIT_WORK(&s->work, cpuset_migrate_tasks_workfn);
                 schedule_work(&s->work);
         }
 }
 
 static void
 hotplug_update_tasks(struct cpuset *cs,
                      struct cpumask *new_cpus, nodemask_t *new_mems,
                      bool cpus_updated, bool mems_updated)
 {
         /* A partition root is allowed to have empty effective cpus */
         if (cpumask_empty(new_cpus) && !is_partition_valid(cs))
                 cpumask_copy(new_cpus, parent_cs(cs)->effective_cpus);
         if (nodes_empty(*new_mems))
                 *new_mems = parent_cs(cs)->effective_mems;
 
         spin_lock_irq(&callback_lock);
         cpumask_copy(cs->effective_cpus, new_cpus);
         cs->effective_mems = *new_mems;
         spin_unlock_irq(&callback_lock);
 
         if (cpus_updated)
                 update_tasks_cpumask(cs, new_cpus);
         if (mems_updated)
                 update_tasks_nodemask(cs);
 }
 
 static bool force_rebuild;
 
 void cpuset_force_rebuild(void)
 {
         force_rebuild = true;
 }
 
 /**
  * cpuset_hotplug_update_tasks - update tasks in a cpuset for hotunplug
  * @cs: cpuset in interest
  * @tmp: the tmpmasks structure pointer
  *
  * Compare @cs's cpu and mem masks against top_cpuset and if some have gone
  * offline, update @cs accordingly.  If @cs ends up with no CPU or memory,
  * all its tasks are moved to the nearest ancestor with both resources.
  */
 static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp)
 {
         static cpumask_t new_cpus;
         static nodemask_t new_mems;
         bool cpus_updated;
         bool mems_updated;
         bool remote;
         int partcmd = -1;
         struct cpuset *parent;
 retry:
         wait_event(cpuset_attach_wq, cs->attach_in_progress == 0);
 
         mutex_lock(&cpuset_mutex);
 
         /*
          * We have raced with task attaching. We wait until attaching
          * is finished, so we won't attach a task to an empty cpuset.
          */
         if (cs->attach_in_progress) {
                 mutex_unlock(&cpuset_mutex);
                 goto retry;
         }
 
         parent = parent_cs(cs);
         compute_effective_cpumask(&new_cpus, cs, parent);
         nodes_and(new_mems, cs->mems_allowed, parent->effective_mems);
 
         if (!tmp || !cs->partition_root_state)
                 goto update_tasks;
 
         /*
          * Compute effective_cpus for valid partition root, may invalidate
          * child partition roots if necessary.
          */
         remote = is_remote_partition(cs);
         if (remote || (is_partition_valid(cs) && is_partition_valid(parent)))
                 compute_partition_effective_cpumask(cs, &new_cpus);
 
         if (remote && cpumask_empty(&new_cpus) &&
             partition_is_populated(cs, NULL)) {
                 remote_partition_disable(cs, tmp);
                 compute_effective_cpumask(&new_cpus, cs, parent);
                 remote = false;
                 cpuset_force_rebuild();
         }
 
         /*
          * Force the partition to become invalid if either one of
          * the following conditions hold:
          * 1) empty effective cpus but not valid empty partition.
          * 2) parent is invalid or doesn't grant any cpus to child
          *    partitions.
          */
         if (is_local_partition(cs) && (!is_partition_valid(parent) ||
                                 tasks_nocpu_error(parent, cs, &new_cpus)))
                 partcmd = partcmd_invalidate;
         /*
          * On the other hand, an invalid partition root may be transitioned
          * back to a regular one.
          */
         else if (is_partition_valid(parent) && is_partition_invalid(cs))
                 partcmd = partcmd_update;
 
         if (partcmd >= 0) {
                 update_parent_effective_cpumask(cs, partcmd, NULL, tmp);
                 if ((partcmd == partcmd_invalidate) || is_partition_valid(cs)) {
                         compute_partition_effective_cpumask(cs, &new_cpus);
                         cpuset_force_rebuild();
                 }
         }
 
 update_tasks:
         cpus_updated = !cpumask_equal(&new_cpus, cs->effective_cpus);
         mems_updated = !nodes_equal(new_mems, cs->effective_mems);
         if (!cpus_updated && !mems_updated)
                 goto unlock;    /* Hotplug doesn't affect this cpuset */
 
         if (mems_updated)
                 check_insane_mems_config(&new_mems);
 
         if (is_in_v2_mode())
                 hotplug_update_tasks(cs, &new_cpus, &new_mems,
                                      cpus_updated, mems_updated);
         else
                 hotplug_update_tasks_legacy(cs, &new_cpus, &new_mems,
                                             cpus_updated, mems_updated);
 
 unlock:
         mutex_unlock(&cpuset_mutex);
 }
 
 /**
  * cpuset_handle_hotplug - handle CPU/memory hot{,un}plug for a cpuset
  *
  * This function is called after either CPU or memory configuration has
  * changed and updates cpuset accordingly.  The top_cpuset is always
  * synchronized to cpu_active_mask and N_MEMORY, which is necessary in
  * order to make cpusets transparent (of no affect) on systems that are
  * actively using CPU hotplug but making no active use of cpusets.
  *
  * Non-root cpusets are only affected by offlining.  If any CPUs or memory
  * nodes have been taken down, cpuset_hotplug_update_tasks() is invoked on
  * all descendants.
  *
  * Note that CPU offlining during suspend is ignored.  We don't modify
  * cpusets across suspend/resume cycles at all.
  *
  * CPU / memory hotplug is handled synchronously.
  */
 static void cpuset_handle_hotplug(void)
 {
         static cpumask_t new_cpus;
         static nodemask_t new_mems;
         bool cpus_updated, mems_updated;
         bool on_dfl = is_in_v2_mode();
         struct tmpmasks tmp, *ptmp = NULL;
 
         if (on_dfl && !alloc_cpumasks(NULL, &tmp))
                 ptmp = &tmp;
 
         lockdep_assert_cpus_held();
         mutex_lock(&cpuset_mutex);
 
         /* fetch the available cpus/mems and find out which changed how */
         cpumask_copy(&new_cpus, cpu_active_mask);
         new_mems = node_states[N_MEMORY];
 
         /*
          * If subpartitions_cpus is populated, it is likely that the check
          * below will produce a false positive on cpus_updated when the cpu
          * list isn't changed. It is extra work, but it is better to be safe.
          */
         cpus_updated = !cpumask_equal(top_cpuset.effective_cpus, &new_cpus) ||
                        !cpumask_empty(subpartitions_cpus);
         mems_updated = !nodes_equal(top_cpuset.effective_mems, new_mems);
 
         /*
          * In the rare case that hotplug removes all the cpus in
          * subpartitions_cpus, we assumed that cpus are updated.
          */
         if (!cpus_updated && !cpumask_empty(subpartitions_cpus))
                 cpus_updated = true;
 
         /* For v1, synchronize cpus_allowed to cpu_active_mask */
         if (cpus_updated) {
                 spin_lock_irq(&callback_lock);
                 if (!on_dfl)
                         cpumask_copy(top_cpuset.cpus_allowed, &new_cpus);
                 /*
                  * Make sure that CPUs allocated to child partitions
                  * do not show up in effective_cpus. If no CPU is left,
                  * we clear the subpartitions_cpus & let the child partitions
                  * fight for the CPUs again.
                  */
                 if (!cpumask_empty(subpartitions_cpus)) {
                         if (cpumask_subset(&new_cpus, subpartitions_cpus)) {
                                 top_cpuset.nr_subparts = 0;
                                 cpumask_clear(subpartitions_cpus);
                         } else {
                                 cpumask_andnot(&new_cpus, &new_cpus,
                                                subpartitions_cpus);
                         }
                 }
                 cpumask_copy(top_cpuset.effective_cpus, &new_cpus);
                 spin_unlock_irq(&callback_lock);
                 /* we don't mess with cpumasks of tasks in top_cpuset */
         }
 
         /* synchronize mems_allowed to N_MEMORY */
         if (mems_updated) {
                 spin_lock_irq(&callback_lock);
                 if (!on_dfl)
                         top_cpuset.mems_allowed = new_mems;
                 top_cpuset.effective_mems = new_mems;
                 spin_unlock_irq(&callback_lock);
                 update_tasks_nodemask(&top_cpuset);
         }
 
         mutex_unlock(&cpuset_mutex);
 
         /* if cpus or mems changed, we need to propagate to descendants */
         if (cpus_updated || mems_updated) {
                 struct cpuset *cs;
                 struct cgroup_subsys_state *pos_css;
 
                 rcu_read_lock();
                 cpuset_for_each_descendant_pre(cs, pos_css, &top_cpuset) {
                         if (cs == &top_cpuset || !css_tryget_online(&cs->css))
                                 continue;
                         rcu_read_unlock();
 
                         cpuset_hotplug_update_tasks(cs, ptmp);
 
                         rcu_read_lock();
                         css_put(&cs->css);
                 }
                 rcu_read_unlock();
         }
 
         /* rebuild sched domains if cpus_allowed has changed */
         if (cpus_updated || force_rebuild) {
                 force_rebuild = false;
                 rebuild_sched_domains_cpuslocked();
         }
 
         free_cpumasks(NULL, ptmp);
 }
 
 void cpuset_update_active_cpus(void)
 {
         /*
          * We're inside cpu hotplug critical region which usually nests
          * inside cgroup synchronization.  Bounce actual hotplug processing
          * to a work item to avoid reverse locking order.
          */
         cpuset_handle_hotplug();
 }
 
 /*
  * Keep top_cpuset.mems_allowed tracking node_states[N_MEMORY].
  * Call this routine anytime after node_states[N_MEMORY] changes.
  * See cpuset_update_active_cpus() for CPU hotplug handling.
  */
 static int cpuset_track_online_nodes(struct notifier_block *self,
                                 unsigned long action, void *arg)
 {
         cpuset_handle_hotplug();
         return NOTIFY_OK;
 }
 
 /**
  * cpuset_init_smp - initialize cpus_allowed
  *
  * Description: Finish top cpuset after cpu, node maps are initialized
  */
 void __init cpuset_init_smp(void)
 {
         /*
          * cpus_allowd/mems_allowed set to v2 values in the initial
          * cpuset_bind() call will be reset to v1 values in another
          * cpuset_bind() call when v1 cpuset is mounted.
          */
         top_cpuset.old_mems_allowed = top_cpuset.mems_allowed;
 
         cpumask_copy(top_cpuset.effective_cpus, cpu_active_mask);
         top_cpuset.effective_mems = node_states[N_MEMORY];
 
         hotplug_memory_notifier(cpuset_track_online_nodes, CPUSET_CALLBACK_PRI);
 
         cpuset_migrate_mm_wq = alloc_ordered_workqueue("cpuset_migrate_mm", 0);
         BUG_ON(!cpuset_migrate_mm_wq);
 }
 
 /**
  * cpuset_cpus_allowed - return cpus_allowed mask from a tasks cpuset.
  * @tsk: pointer to task_struct from which to obtain cpuset->cpus_allowed.
  * @pmask: pointer to struct cpumask variable to receive cpus_allowed set.
  *
  * Description: Returns the cpumask_var_t cpus_allowed of the cpuset
  * attached to the specified @tsk.  Guaranteed to return some non-empty
  * subset of cpu_online_mask, even if this means going outside the
  * tasks cpuset, except when the task is in the top cpuset.
  **/
 
 void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask)
 {
         unsigned long flags;
         struct cpuset *cs;
 
         spin_lock_irqsave(&callback_lock, flags);
         rcu_read_lock();
 
         cs = task_cs(tsk);
         if (cs != &top_cpuset)
                 guarantee_online_cpus(tsk, pmask);
         /*
          * Tasks in the top cpuset won't get update to their cpumasks
          * when a hotplug online/offline event happens. So we include all
          * offline cpus in the allowed cpu list.
          */
         if ((cs == &top_cpuset) || cpumask_empty(pmask)) {
                 const struct cpumask *possible_mask = task_cpu_possible_mask(tsk);
 
                 /*
                  * We first exclude cpus allocated to partitions. If there is no
                  * allowable online cpu left, we fall back to all possible cpus.
                  */
                 cpumask_andnot(pmask, possible_mask, subpartitions_cpus);
                 if (!cpumask_intersects(pmask, cpu_online_mask))
                         cpumask_copy(pmask, possible_mask);
         }
 
         rcu_read_unlock();
         spin_unlock_irqrestore(&callback_lock, flags);
 }
 
 /**
  * cpuset_cpus_allowed_fallback - final fallback before complete catastrophe.
  * @tsk: pointer to task_struct with which the scheduler is struggling
  *
  * Description: In the case that the scheduler cannot find an allowed cpu in
  * tsk->cpus_allowed, we fall back to task_cs(tsk)->cpus_allowed. In legacy
  * mode however, this value is the same as task_cs(tsk)->effective_cpus,
  * which will not contain a sane cpumask during cases such as cpu hotplugging.
  * This is the absolute last resort for the scheduler and it is only used if
  * _every_ other avenue has been traveled.
  *
  * Returns true if the affinity of @tsk was changed, false otherwise.
  **/
 
 bool cpuset_cpus_allowed_fallback(struct task_struct *tsk)
 {
         const struct cpumask *possible_mask = task_cpu_possible_mask(tsk);
         const struct cpumask *cs_mask;
         bool changed = false;
 
         rcu_read_lock();
         cs_mask = task_cs(tsk)->cpus_allowed;
         if (is_in_v2_mode() && cpumask_subset(cs_mask, possible_mask)) {
                 do_set_cpus_allowed(tsk, cs_mask);
                 changed = true;
         }
         rcu_read_unlock();
 
         /*
          * We own tsk->cpus_allowed, nobody can change it under us.
          *
          * But we used cs && cs->cpus_allowed lockless and thus can
          * race with cgroup_attach_task() or update_cpumask() and get
          * the wrong tsk->cpus_allowed. However, both cases imply the
          * subsequent cpuset_change_cpumask()->set_cpus_allowed_ptr()
          * which takes task_rq_lock().
          *
          * If we are called after it dropped the lock we must see all
          * changes in tsk_cs()->cpus_allowed. Otherwise we can temporary
          * set any mask even if it is not right from task_cs() pov,
          * the pending set_cpus_allowed_ptr() will fix things.
          *
          * select_fallback_rq() will fix things ups and set cpu_possible_mask
          * if required.
          */
         return changed;
 }
 
 void __init cpuset_init_current_mems_allowed(void)
 {
         nodes_setall(current->mems_allowed);
 }
 
 /**
  * cpuset_mems_allowed - return mems_allowed mask from a tasks cpuset.
  * @tsk: pointer to task_struct from which to obtain cpuset->mems_allowed.
  *
  * Description: Returns the nodemask_t mems_allowed of the cpuset
  * attached to the specified @tsk.  Guaranteed to return some non-empty
  * subset of node_states[N_MEMORY], even if this means going outside the
  * tasks cpuset.
  **/
 
 nodemask_t cpuset_mems_allowed(struct task_struct *tsk)
 {
         nodemask_t mask;
         unsigned long flags;
 
         spin_lock_irqsave(&callback_lock, flags);
         rcu_read_lock();
         guarantee_online_mems(task_cs(tsk), &mask);
         rcu_read_unlock();
         spin_unlock_irqrestore(&callback_lock, flags);
 
         return mask;
 }
 
 /**
  * cpuset_nodemask_valid_mems_allowed - check nodemask vs. current mems_allowed
  * @nodemask: the nodemask to be checked
  *
  * Are any of the nodes in the nodemask allowed in current->mems_allowed?
  */
 int cpuset_nodemask_valid_mems_allowed(nodemask_t *nodemask)
 {
         return nodes_intersects(*nodemask, current->mems_allowed);
 }
 
 /*
  * nearest_hardwall_ancestor() - Returns the nearest mem_exclusive or
  * mem_hardwall ancestor to the specified cpuset.  Call holding
  * callback_lock.  If no ancestor is mem_exclusive or mem_hardwall
  * (an unusual configuration), then returns the root cpuset.
  */
 static struct cpuset *nearest_hardwall_ancestor(struct cpuset *cs)
 {
         while (!(is_mem_exclusive(cs) || is_mem_hardwall(cs)) && parent_cs(cs))
                 cs = parent_cs(cs);
         return cs;
 }
 
 /*
  * cpuset_node_allowed - Can we allocate on a memory node?
  * @node: is this an allowed node?
  * @gfp_mask: memory allocation flags
  *
  * If we're in interrupt, yes, we can always allocate.  If @node is set in
  * current's mems_allowed, yes.  If it's not a __GFP_HARDWALL request and this
  * node is set in the nearest hardwalled cpuset ancestor to current's cpuset,
  * yes.  If current has access to memory reserves as an oom victim, yes.
  * Otherwise, no.
  *
  * GFP_USER allocations are marked with the __GFP_HARDWALL bit,
  * and do not allow allocations outside the current tasks cpuset
  * unless the task has been OOM killed.
  * GFP_KERNEL allocations are not so marked, so can escape to the
  * nearest enclosing hardwalled ancestor cpuset.
  *
  * Scanning up parent cpusets requires callback_lock.  The
  * __alloc_pages() routine only calls here with __GFP_HARDWALL bit
  * _not_ set if it's a GFP_KERNEL allocation, and all nodes in the
  * current tasks mems_allowed came up empty on the first pass over
  * the zonelist.  So only GFP_KERNEL allocations, if all nodes in the
  * cpuset are short of memory, might require taking the callback_lock.
  *
  * The first call here from mm/page_alloc:get_page_from_freelist()
  * has __GFP_HARDWALL set in gfp_mask, enforcing hardwall cpusets,
  * so no allocation on a node outside the cpuset is allowed (unless
  * in interrupt, of course).
  *
  * The second pass through get_page_from_freelist() doesn't even call
  * here for GFP_ATOMIC calls.  For those calls, the __alloc_pages()
  * variable 'wait' is not set, and the bit ALLOC_CPUSET is not set
  * in alloc_flags.  That logic and the checks below have the combined
  * affect that:
  *      in_interrupt - any node ok (current task context irrelevant)
  *      GFP_ATOMIC   - any node ok
  *      tsk_is_oom_victim   - any node ok
  *      GFP_KERNEL   - any node in enclosing hardwalled cpuset ok
  *      GFP_USER     - only nodes in current tasks mems allowed ok.
  */
 bool cpuset_node_allowed(int node, gfp_t gfp_mask)
 {
         struct cpuset *cs;              /* current cpuset ancestors */
         bool allowed;                   /* is allocation in zone z allowed? */
         unsigned long flags;
 
         if (in_interrupt())
                 return true;
         if (node_isset(node, current->mems_allowed))
                 return true;
         /*
          * Allow tasks that have access to memory reserves because they have
          * been OOM killed to get memory anywhere.
          */
         if (unlikely(tsk_is_oom_victim(current)))
                 return true;
         if (gfp_mask & __GFP_HARDWALL)  /* If hardwall request, stop here */
                 return false;
 
         if (current->flags & PF_EXITING) /* Let dying task have memory */
                 return true;
 
         /* Not hardwall and node outside mems_allowed: scan up cpusets */
         spin_lock_irqsave(&callback_lock, flags);
 
         rcu_read_lock();
         cs = nearest_hardwall_ancestor(task_cs(current));
         allowed = node_isset(node, cs->mems_allowed);
         rcu_read_unlock();
 
         spin_unlock_irqrestore(&callback_lock, flags);
         return allowed;
 }
 
 /**
  * cpuset_spread_node() - On which node to begin search for a page
  * @rotor: round robin rotor
  *
  * If a task is marked PF_SPREAD_PAGE or PF_SPREAD_SLAB (as for
  * tasks in a cpuset with is_spread_page or is_spread_slab set),
  * and if the memory allocation used cpuset_mem_spread_node()
  * to determine on which node to start looking, as it will for
  * certain page cache or slab cache pages such as used for file
  * system buffers and inode caches, then instead of starting on the
  * local node to look for a free page, rather spread the starting
  * node around the tasks mems_allowed nodes.
  *
  * We don't have to worry about the returned node being offline
  * because "it can't happen", and even if it did, it would be ok.
  *
  * The routines calling guarantee_online_mems() are careful to
  * only set nodes in task->mems_allowed that are online.  So it
  * should not be possible for the following code to return an
  * offline node.  But if it did, that would be ok, as this routine
  * is not returning the node where the allocation must be, only
  * the node where the search should start.  The zonelist passed to
  * __alloc_pages() will include all nodes.  If the slab allocator
  * is passed an offline node, it will fall back to the local node.
  * See kmem_cache_alloc_node().
  */
 static int cpuset_spread_node(int *rotor)
 {
         return *rotor = next_node_in(*rotor, current->mems_allowed);
 }
 
 /**
  * cpuset_mem_spread_node() - On which node to begin search for a file page
  */
 int cpuset_mem_spread_node(void)
 {
         if (current->cpuset_mem_spread_rotor == NUMA_NO_NODE)
                 current->cpuset_mem_spread_rotor =
                         node_random(&current->mems_allowed);
 
         return cpuset_spread_node(&current->cpuset_mem_spread_rotor);
 }
 
 /**
  * cpuset_slab_spread_node() - On which node to begin search for a slab page
  */
 int cpuset_slab_spread_node(void)
 {
         if (current->cpuset_slab_spread_rotor == NUMA_NO_NODE)
                 current->cpuset_slab_spread_rotor =
                         node_random(&current->mems_allowed);
 
         return cpuset_spread_node(&current->cpuset_slab_spread_rotor);
 }
 EXPORT_SYMBOL_GPL(cpuset_mem_spread_node);
 
 /**
  * cpuset_mems_allowed_intersects - Does @tsk1's mems_allowed intersect @tsk2's?
  * @tsk1: pointer to task_struct of some task.
  * @tsk2: pointer to task_struct of some other task.
  *
  * Description: Return true if @tsk1's mems_allowed intersects the
  * mems_allowed of @tsk2.  Used by the OOM killer to determine if
  * one of the task's memory usage might impact the memory available
  * to the other.
  **/
 
 int cpuset_mems_allowed_intersects(const struct task_struct *tsk1,
                                    const struct task_struct *tsk2)
 {
         return nodes_intersects(tsk1->mems_allowed, tsk2->mems_allowed);
 }
 
 /**
  * cpuset_print_current_mems_allowed - prints current's cpuset and mems_allowed
  *
  * Description: Prints current's name, cpuset name, and cached copy of its
  * mems_allowed to the kernel log.
  */
 void cpuset_print_current_mems_allowed(void)
 {
         struct cgroup *cgrp;
 
         rcu_read_lock();
 
         cgrp = task_cs(current)->css.cgroup;
         pr_cont(",cpuset=");
         pr_cont_cgroup_name(cgrp);
         pr_cont(",mems_allowed=%*pbl",
                 nodemask_pr_args(&current->mems_allowed));
 
         rcu_read_unlock();
 }
 
 /*
  * Collection of memory_pressure is suppressed unless
  * this flag is enabled by writing "1" to the special
  * cpuset file 'memory_pressure_enabled' in the root cpuset.
  */
 
 int cpuset_memory_pressure_enabled __read_mostly;
 
 /*
  * __cpuset_memory_pressure_bump - keep stats of per-cpuset reclaims.
  *
  * Keep a running average of the rate of synchronous (direct)
  * page reclaim efforts initiated by tasks in each cpuset.
  *
  * This represents the rate at which some task in the cpuset
  * ran low on memory on all nodes it was allowed to use, and
  * had to enter the kernels page reclaim code in an effort to
  * create more free memory by tossing clean pages or swapping
  * or writing dirty pages.
  *
  * Display to user space in the per-cpuset read-only file
  * "memory_pressure".  Value displayed is an integer
  * representing the recent rate of entry into the synchronous
  * (direct) page reclaim by any task attached to the cpuset.
  */
 
 void __cpuset_memory_pressure_bump(void)
 {
         rcu_read_lock();
         fmeter_markevent(&task_cs(current)->fmeter);
         rcu_read_unlock();
 }
 
 #ifdef CONFIG_PROC_PID_CPUSET
 /*
  * proc_cpuset_show()
  *  - Print tasks cpuset path into seq_file.
  *  - Used for /proc/<pid>/cpuset.
  *  - No need to task_lock(tsk) on this tsk->cpuset reference, as it
  *    doesn't really matter if tsk->cpuset changes after we read it,
  *    and we take cpuset_mutex, keeping cpuset_attach() from changing it
  *    anyway.
  */
 int proc_cpuset_show(struct seq_file *m, struct pid_namespace *ns,
                      struct pid *pid, struct task_struct *tsk)
 {
         char *buf;
         struct cgroup_subsys_state *css;
         int retval;
 
         retval = -ENOMEM;
         buf = kmalloc(PATH_MAX, GFP_KERNEL);
         if (!buf)
                 goto out;
 
         rcu_read_lock();
         spin_lock_irq(&css_set_lock);
         css = task_css(tsk, cpuset_cgrp_id);
         retval = cgroup_path_ns_locked(css->cgroup, buf, PATH_MAX,
                                        current->nsproxy->cgroup_ns);
         spin_unlock_irq(&css_set_lock);
         rcu_read_unlock();
 
         if (retval == -E2BIG)
                 retval = -ENAMETOOLONG;
         if (retval < 0)
                 goto out_free;
         seq_puts(m, buf);
         seq_putc(m, '\n');
         retval = 0;
 out_free:
         kfree(buf);
 out:
         return retval;
 }
 #endif /* CONFIG_PROC_PID_CPUSET */
 
 /* Display task mems_allowed in /proc/<pid>/status file. */
 void cpuset_task_status_allowed(struct seq_file *m, struct task_struct *task)
 {
         seq_printf(m, "Mems_allowed:\t%*pb\n",
                    nodemask_pr_args(&task->mems_allowed));
         seq_printf(m, "Mems_allowed_list:\t%*pbl\n",
                    nodemask_pr_args(&task->mems_allowed));
 }