TOMOYO Linux Cross Reference
Linux/fs/gfs2/glock.c

   // SPDX-License-Identifier: GPL-2.0-only
   /*
    * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
    * Copyright (C) 2004-2008 Red Hat, Inc.  All rights reserved.
    */
   
   #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   
   #include <linux/sched.h>
  #include <linux/slab.h>
  #include <linux/spinlock.h>
  #include <linux/buffer_head.h>
  #include <linux/delay.h>
  #include <linux/sort.h>
  #include <linux/hash.h>
  #include <linux/jhash.h>
  #include <linux/kallsyms.h>
  #include <linux/gfs2_ondisk.h>
  #include <linux/list.h>
  #include <linux/wait.h>
  #include <linux/module.h>
  #include <linux/uaccess.h>
  #include <linux/seq_file.h>
  #include <linux/debugfs.h>
  #include <linux/kthread.h>
  #include <linux/freezer.h>
  #include <linux/workqueue.h>
  #include <linux/jiffies.h>
  #include <linux/rcupdate.h>
  #include <linux/rculist_bl.h>
  #include <linux/bit_spinlock.h>
  #include <linux/percpu.h>
  #include <linux/list_sort.h>
  #include <linux/lockref.h>
  #include <linux/rhashtable.h>
  #include <linux/pid_namespace.h>
  #include <linux/fdtable.h>
  #include <linux/file.h>
  
  #include "gfs2.h"
  #include "incore.h"
  #include "glock.h"
  #include "glops.h"
  #include "inode.h"
  #include "lops.h"
  #include "meta_io.h"
  #include "quota.h"
  #include "super.h"
  #include "util.h"
  #include "bmap.h"
  #define CREATE_TRACE_POINTS
  #include "trace_gfs2.h"
  
  struct gfs2_glock_iter {
          struct gfs2_sbd *sdp;           /* incore superblock           */
          struct rhashtable_iter hti;     /* rhashtable iterator         */
          struct gfs2_glock *gl;          /* current glock struct        */
          loff_t last_pos;                /* last position               */
  };
  
  typedef void (*glock_examiner) (struct gfs2_glock * gl);
  
  static void do_xmote(struct gfs2_glock *gl, struct gfs2_holder *gh, unsigned int target);
  static void request_demote(struct gfs2_glock *gl, unsigned int state,
                             unsigned long delay, bool remote);
  
  static struct dentry *gfs2_root;
  static LIST_HEAD(lru_list);
  static atomic_t lru_count = ATOMIC_INIT(0);
  static DEFINE_SPINLOCK(lru_lock);
  
  #define GFS2_GL_HASH_SHIFT      15
  #define GFS2_GL_HASH_SIZE       BIT(GFS2_GL_HASH_SHIFT)
  
  static const struct rhashtable_params ht_parms = {
          .nelem_hint = GFS2_GL_HASH_SIZE * 3 / 4,
          .key_len = offsetofend(struct lm_lockname, ln_type),
          .key_offset = offsetof(struct gfs2_glock, gl_name),
          .head_offset = offsetof(struct gfs2_glock, gl_node),
  };
  
  static struct rhashtable gl_hash_table;
  
  #define GLOCK_WAIT_TABLE_BITS 12
  #define GLOCK_WAIT_TABLE_SIZE (1 << GLOCK_WAIT_TABLE_BITS)
  static wait_queue_head_t glock_wait_table[GLOCK_WAIT_TABLE_SIZE] __cacheline_aligned;
  
  struct wait_glock_queue {
          struct lm_lockname *name;
          wait_queue_entry_t wait;
  };
  
  static int glock_wake_function(wait_queue_entry_t *wait, unsigned int mode,
                                 int sync, void *key)
  {
          struct wait_glock_queue *wait_glock =
                  container_of(wait, struct wait_glock_queue, wait);
          struct lm_lockname *wait_name = wait_glock->name;
          struct lm_lockname *wake_name = key;
 
         if (wake_name->ln_sbd != wait_name->ln_sbd ||
             wake_name->ln_number != wait_name->ln_number ||
             wake_name->ln_type != wait_name->ln_type)
                 return 0;
         return autoremove_wake_function(wait, mode, sync, key);
 }
 
 static wait_queue_head_t *glock_waitqueue(struct lm_lockname *name)
 {
         u32 hash = jhash2((u32 *)name, ht_parms.key_len / 4, 0);
 
         return glock_wait_table + hash_32(hash, GLOCK_WAIT_TABLE_BITS);
 }
 
 /**
  * wake_up_glock  -  Wake up waiters on a glock
  * @gl: the glock
  */
 static void wake_up_glock(struct gfs2_glock *gl)
 {
         wait_queue_head_t *wq = glock_waitqueue(&gl->gl_name);
 
         if (waitqueue_active(wq))
                 __wake_up(wq, TASK_NORMAL, 1, &gl->gl_name);
 }
 
 static void gfs2_glock_dealloc(struct rcu_head *rcu)
 {
         struct gfs2_glock *gl = container_of(rcu, struct gfs2_glock, gl_rcu);
 
         kfree(gl->gl_lksb.sb_lvbptr);
         if (gl->gl_ops->go_flags & GLOF_ASPACE) {
                 struct gfs2_glock_aspace *gla =
                         container_of(gl, struct gfs2_glock_aspace, glock);
                 kmem_cache_free(gfs2_glock_aspace_cachep, gla);
         } else
                 kmem_cache_free(gfs2_glock_cachep, gl);
 }
 
 /**
  * glock_blocked_by_withdraw - determine if we can still use a glock
  * @gl: the glock
  *
  * We need to allow some glocks to be enqueued, dequeued, promoted, and demoted
  * when we're withdrawn. For example, to maintain metadata integrity, we should
  * disallow the use of inode and rgrp glocks when withdrawn. Other glocks like
  * the iopen or freeze glock may be safely used because none of their
  * metadata goes through the journal. So in general, we should disallow all
  * glocks that are journaled, and allow all the others. One exception is:
  * we need to allow our active journal to be promoted and demoted so others
  * may recover it and we can reacquire it when they're done.
  */
 static bool glock_blocked_by_withdraw(struct gfs2_glock *gl)
 {
         struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
 
         if (!gfs2_withdrawing_or_withdrawn(sdp))
                 return false;
         if (gl->gl_ops->go_flags & GLOF_NONDISK)
                 return false;
         if (!sdp->sd_jdesc ||
             gl->gl_name.ln_number == sdp->sd_jdesc->jd_no_addr)
                 return false;
         return true;
 }
 
 static void __gfs2_glock_free(struct gfs2_glock *gl)
 {
         rhashtable_remove_fast(&gl_hash_table, &gl->gl_node, ht_parms);
         smp_mb();
         wake_up_glock(gl);
         call_rcu(&gl->gl_rcu, gfs2_glock_dealloc);
 }
 
 void gfs2_glock_free(struct gfs2_glock *gl) {
         struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
 
         __gfs2_glock_free(gl);
         if (atomic_dec_and_test(&sdp->sd_glock_disposal))
                 wake_up(&sdp->sd_kill_wait);
 }
 
 void gfs2_glock_free_later(struct gfs2_glock *gl) {
         struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
 
         spin_lock(&lru_lock);
         list_add(&gl->gl_lru, &sdp->sd_dead_glocks);
         spin_unlock(&lru_lock);
         if (atomic_dec_and_test(&sdp->sd_glock_disposal))
                 wake_up(&sdp->sd_kill_wait);
 }
 
 static void gfs2_free_dead_glocks(struct gfs2_sbd *sdp)
 {
         struct list_head *list = &sdp->sd_dead_glocks;
 
         while(!list_empty(list)) {
                 struct gfs2_glock *gl;
 
                 gl = list_first_entry(list, struct gfs2_glock, gl_lru);
                 list_del_init(&gl->gl_lru);
                 __gfs2_glock_free(gl);
         }
 }
 
 /**
  * gfs2_glock_hold() - increment reference count on glock
  * @gl: The glock to hold
  *
  */
 
 struct gfs2_glock *gfs2_glock_hold(struct gfs2_glock *gl)
 {
         GLOCK_BUG_ON(gl, __lockref_is_dead(&gl->gl_lockref));
         lockref_get(&gl->gl_lockref);
         return gl;
 }
 
 static void gfs2_glock_add_to_lru(struct gfs2_glock *gl)
 {
         spin_lock(&lru_lock);
         list_move_tail(&gl->gl_lru, &lru_list);
 
         if (!test_bit(GLF_LRU, &gl->gl_flags)) {
                 set_bit(GLF_LRU, &gl->gl_flags);
                 atomic_inc(&lru_count);
         }
 
         spin_unlock(&lru_lock);
 }
 
 static void gfs2_glock_remove_from_lru(struct gfs2_glock *gl)
 {
         spin_lock(&lru_lock);
         if (test_bit(GLF_LRU, &gl->gl_flags)) {
                 list_del_init(&gl->gl_lru);
                 atomic_dec(&lru_count);
                 clear_bit(GLF_LRU, &gl->gl_flags);
         }
         spin_unlock(&lru_lock);
 }
 
 /*
  * Enqueue the glock on the work queue.  Passes one glock reference on to the
  * work queue.
  */
 static void gfs2_glock_queue_work(struct gfs2_glock *gl, unsigned long delay) {
         struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
 
         if (!queue_delayed_work(sdp->sd_glock_wq, &gl->gl_work, delay)) {
                 /*
                  * We are holding the lockref spinlock, and the work was still
                  * queued above.  The queued work (glock_work_func) takes that
                  * spinlock before dropping its glock reference(s), so it
                  * cannot have dropped them in the meantime.
                  */
                 GLOCK_BUG_ON(gl, gl->gl_lockref.count < 2);
                 gl->gl_lockref.count--;
         }
 }
 
 static void __gfs2_glock_put(struct gfs2_glock *gl)
 {
         struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
         struct address_space *mapping = gfs2_glock2aspace(gl);
 
         lockref_mark_dead(&gl->gl_lockref);
         spin_unlock(&gl->gl_lockref.lock);
         gfs2_glock_remove_from_lru(gl);
         GLOCK_BUG_ON(gl, !list_empty(&gl->gl_holders));
         if (mapping) {
                 truncate_inode_pages_final(mapping);
                 if (!gfs2_withdrawing_or_withdrawn(sdp))
                         GLOCK_BUG_ON(gl, !mapping_empty(mapping));
         }
         trace_gfs2_glock_put(gl);
         sdp->sd_lockstruct.ls_ops->lm_put_lock(gl);
 }
 
 static bool __gfs2_glock_put_or_lock(struct gfs2_glock *gl)
 {
         if (lockref_put_or_lock(&gl->gl_lockref))
                 return true;
         GLOCK_BUG_ON(gl, gl->gl_lockref.count != 1);
         if (gl->gl_state != LM_ST_UNLOCKED) {
                 gl->gl_lockref.count--;
                 gfs2_glock_add_to_lru(gl);
                 spin_unlock(&gl->gl_lockref.lock);
                 return true;
         }
         return false;
 }
 
 /**
  * gfs2_glock_put() - Decrement reference count on glock
  * @gl: The glock to put
  *
  */
 
 void gfs2_glock_put(struct gfs2_glock *gl)
 {
         if (__gfs2_glock_put_or_lock(gl))
                 return;
 
         __gfs2_glock_put(gl);
 }
 
 /*
  * gfs2_glock_put_async - Decrement reference count without sleeping
  * @gl: The glock to put
  *
  * Decrement the reference count on glock immediately unless it is the last
  * reference.  Defer putting the last reference to work queue context.
  */
 void gfs2_glock_put_async(struct gfs2_glock *gl)
 {
         if (__gfs2_glock_put_or_lock(gl))
                 return;
 
         gfs2_glock_queue_work(gl, 0);
         spin_unlock(&gl->gl_lockref.lock);
 }
 
 /**
  * may_grant - check if it's ok to grant a new lock
  * @gl: The glock
  * @current_gh: One of the current holders of @gl
  * @gh: The lock request which we wish to grant
  *
  * With our current compatibility rules, if a glock has one or more active
  * holders (HIF_HOLDER flag set), any of those holders can be passed in as
  * @current_gh; they are all the same as far as compatibility with the new @gh
  * goes.
  *
  * Returns true if it's ok to grant the lock.
  */
 
 static inline bool may_grant(struct gfs2_glock *gl,
                              struct gfs2_holder *current_gh,
                              struct gfs2_holder *gh)
 {
         if (current_gh) {
                 GLOCK_BUG_ON(gl, !test_bit(HIF_HOLDER, &current_gh->gh_iflags));
 
                 switch(current_gh->gh_state) {
                 case LM_ST_EXCLUSIVE:
                         /*
                          * Here we make a special exception to grant holders
                          * who agree to share the EX lock with other holders
                          * who also have the bit set. If the original holder
                          * has the LM_FLAG_NODE_SCOPE bit set, we grant more
                          * holders with the bit set.
                          */
                         return gh->gh_state == LM_ST_EXCLUSIVE &&
                                (current_gh->gh_flags & LM_FLAG_NODE_SCOPE) &&
                                (gh->gh_flags & LM_FLAG_NODE_SCOPE);
 
                 case LM_ST_SHARED:
                 case LM_ST_DEFERRED:
                         return gh->gh_state == current_gh->gh_state;
 
                 default:
                         return false;
                 }
         }
 
         if (gl->gl_state == gh->gh_state)
                 return true;
         if (gh->gh_flags & GL_EXACT)
                 return false;
         if (gl->gl_state == LM_ST_EXCLUSIVE) {
                 return gh->gh_state == LM_ST_SHARED ||
                        gh->gh_state == LM_ST_DEFERRED;
         }
         if (gh->gh_flags & LM_FLAG_ANY)
                 return gl->gl_state != LM_ST_UNLOCKED;
         return false;
 }
 
 static void gfs2_holder_wake(struct gfs2_holder *gh)
 {
         clear_bit(HIF_WAIT, &gh->gh_iflags);
         smp_mb__after_atomic();
         wake_up_bit(&gh->gh_iflags, HIF_WAIT);
         if (gh->gh_flags & GL_ASYNC) {
                 struct gfs2_sbd *sdp = gh->gh_gl->gl_name.ln_sbd;
 
                 wake_up(&sdp->sd_async_glock_wait);
         }
 }
 
 /**
  * do_error - Something unexpected has happened during a lock request
  * @gl: The glock
  * @ret: The status from the DLM
  */
 
 static void do_error(struct gfs2_glock *gl, const int ret)
 {
         struct gfs2_holder *gh, *tmp;
 
         list_for_each_entry_safe(gh, tmp, &gl->gl_holders, gh_list) {
                 if (test_bit(HIF_HOLDER, &gh->gh_iflags))
                         continue;
                 if (ret & LM_OUT_ERROR)
                         gh->gh_error = -EIO;
                 else if (gh->gh_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB))
                         gh->gh_error = GLR_TRYFAILED;
                 else
                         continue;
                 list_del_init(&gh->gh_list);
                 trace_gfs2_glock_queue(gh, 0);
                 gfs2_holder_wake(gh);
         }
 }
 
 /**
  * find_first_holder - find the first "holder" gh
  * @gl: the glock
  */
 
 static inline struct gfs2_holder *find_first_holder(const struct gfs2_glock *gl)
 {
         struct gfs2_holder *gh;
 
         if (!list_empty(&gl->gl_holders)) {
                 gh = list_first_entry(&gl->gl_holders, struct gfs2_holder,
                                       gh_list);
                 if (test_bit(HIF_HOLDER, &gh->gh_iflags))
                         return gh;
         }
         return NULL;
 }
 
 /*
  * gfs2_instantiate - Call the glops instantiate function
  * @gh: The glock holder
  *
  * Returns: 0 if instantiate was successful, or error.
  */
 int gfs2_instantiate(struct gfs2_holder *gh)
 {
         struct gfs2_glock *gl = gh->gh_gl;
         const struct gfs2_glock_operations *glops = gl->gl_ops;
         int ret;
 
 again:
         if (!test_bit(GLF_INSTANTIATE_NEEDED, &gl->gl_flags))
                 goto done;
 
         /*
          * Since we unlock the lockref lock, we set a flag to indicate
          * instantiate is in progress.
          */
         if (test_and_set_bit(GLF_INSTANTIATE_IN_PROG, &gl->gl_flags)) {
                 wait_on_bit(&gl->gl_flags, GLF_INSTANTIATE_IN_PROG,
                             TASK_UNINTERRUPTIBLE);
                 /*
                  * Here we just waited for a different instantiate to finish.
                  * But that may not have been successful, as when a process
                  * locks an inode glock _before_ it has an actual inode to
                  * instantiate into. So we check again. This process might
                  * have an inode to instantiate, so might be successful.
                  */
                 goto again;
         }
 
         ret = glops->go_instantiate(gl);
         if (!ret)
                 clear_bit(GLF_INSTANTIATE_NEEDED, &gl->gl_flags);
         clear_and_wake_up_bit(GLF_INSTANTIATE_IN_PROG, &gl->gl_flags);
         if (ret)
                 return ret;
 
 done:
         if (glops->go_held)
                 return glops->go_held(gh);
         return 0;
 }
 
 /**
  * do_promote - promote as many requests as possible on the current queue
  * @gl: The glock
  * 
  * Returns true on success (i.e., progress was made or there are no waiters).
  */
 
 static bool do_promote(struct gfs2_glock *gl)
 {
         struct gfs2_holder *gh, *current_gh;
 
         current_gh = find_first_holder(gl);
         list_for_each_entry(gh, &gl->gl_holders, gh_list) {
                 if (test_bit(HIF_HOLDER, &gh->gh_iflags))
                         continue;
                 if (!may_grant(gl, current_gh, gh)) {
                         /*
                          * If we get here, it means we may not grant this
                          * holder for some reason. If this holder is at the
                          * head of the list, it means we have a blocked holder
                          * at the head, so return false.
                          */
                         if (list_is_first(&gh->gh_list, &gl->gl_holders))
                                 return false;
                         do_error(gl, 0);
                         break;
                 }
                 set_bit(HIF_HOLDER, &gh->gh_iflags);
                 trace_gfs2_promote(gh);
                 gfs2_holder_wake(gh);
                 if (!current_gh)
                         current_gh = gh;
         }
         return true;
 }
 
 /**
  * find_first_waiter - find the first gh that's waiting for the glock
  * @gl: the glock
  */
 
 static inline struct gfs2_holder *find_first_waiter(const struct gfs2_glock *gl)
 {
         struct gfs2_holder *gh;
 
         list_for_each_entry(gh, &gl->gl_holders, gh_list) {
                 if (!test_bit(HIF_HOLDER, &gh->gh_iflags))
                         return gh;
         }
         return NULL;
 }
 
 /**
  * find_last_waiter - find the last gh that's waiting for the glock
  * @gl: the glock
  *
  * This also is a fast way of finding out if there are any waiters.
  */
 
 static inline struct gfs2_holder *find_last_waiter(const struct gfs2_glock *gl)
 {
         struct gfs2_holder *gh;
 
         if (list_empty(&gl->gl_holders))
                 return NULL;
         gh = list_last_entry(&gl->gl_holders, struct gfs2_holder, gh_list);
         return test_bit(HIF_HOLDER, &gh->gh_iflags) ? NULL : gh;
 }
 
 /**
  * state_change - record that the glock is now in a different state
  * @gl: the glock
  * @new_state: the new state
  */
 
 static void state_change(struct gfs2_glock *gl, unsigned int new_state)
 {
         if (new_state != gl->gl_target)
                 /* shorten our minimum hold time */
                 gl->gl_hold_time = max(gl->gl_hold_time - GL_GLOCK_HOLD_DECR,
                                        GL_GLOCK_MIN_HOLD);
         gl->gl_state = new_state;
         gl->gl_tchange = jiffies;
 }
 
 static void gfs2_set_demote(struct gfs2_glock *gl)
 {
         struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
 
         set_bit(GLF_DEMOTE, &gl->gl_flags);
         smp_mb();
         wake_up(&sdp->sd_async_glock_wait);
 }
 
 static void gfs2_demote_wake(struct gfs2_glock *gl)
 {
         gl->gl_demote_state = LM_ST_EXCLUSIVE;
         clear_bit(GLF_DEMOTE, &gl->gl_flags);
         smp_mb__after_atomic();
         wake_up_bit(&gl->gl_flags, GLF_DEMOTE);
 }
 
 /**
  * finish_xmote - The DLM has replied to one of our lock requests
  * @gl: The glock
  * @ret: The status from the DLM
  *
  */
 
 static void finish_xmote(struct gfs2_glock *gl, unsigned int ret)
 {
         const struct gfs2_glock_operations *glops = gl->gl_ops;
         struct gfs2_holder *gh;
         unsigned state = ret & LM_OUT_ST_MASK;
 
         trace_gfs2_glock_state_change(gl, state);
         state_change(gl, state);
         gh = find_first_waiter(gl);
 
         /* Demote to UN request arrived during demote to SH or DF */
         if (test_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags) &&
             state != LM_ST_UNLOCKED && gl->gl_demote_state == LM_ST_UNLOCKED)
                 gl->gl_target = LM_ST_UNLOCKED;
 
         /* Check for state != intended state */
         if (unlikely(state != gl->gl_target)) {
                 if (gh && (ret & LM_OUT_CANCELED))
                         gfs2_holder_wake(gh);
                 if (gh && !test_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags)) {
                         /* move to back of queue and try next entry */
                         if (ret & LM_OUT_CANCELED) {
                                 list_move_tail(&gh->gh_list, &gl->gl_holders);
                                 gh = find_first_waiter(gl);
                                 gl->gl_target = gh->gh_state;
                                 if (do_promote(gl))
                                         goto out;
                                 goto retry;
                         }
                         /* Some error or failed "try lock" - report it */
                         if ((ret & LM_OUT_ERROR) ||
                             (gh->gh_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB))) {
                                 gl->gl_target = gl->gl_state;
                                 do_error(gl, ret);
                                 goto out;
                         }
                 }
                 switch(state) {
                 /* Unlocked due to conversion deadlock, try again */
                 case LM_ST_UNLOCKED:
 retry:
                         do_xmote(gl, gh, gl->gl_target);
                         break;
                 /* Conversion fails, unlock and try again */
                 case LM_ST_SHARED:
                 case LM_ST_DEFERRED:
                         do_xmote(gl, gh, LM_ST_UNLOCKED);
                         break;
                 default: /* Everything else */
                         fs_err(gl->gl_name.ln_sbd, "wanted %u got %u\n",
                                gl->gl_target, state);
                         GLOCK_BUG_ON(gl, 1);
                 }
                 return;
         }
 
         /* Fast path - we got what we asked for */
         if (test_and_clear_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags))
                 gfs2_demote_wake(gl);
         if (state != LM_ST_UNLOCKED) {
                 if (glops->go_xmote_bh) {
                         int rv;
 
                         spin_unlock(&gl->gl_lockref.lock);
                         rv = glops->go_xmote_bh(gl);
                         spin_lock(&gl->gl_lockref.lock);
                         if (rv) {
                                 do_error(gl, rv);
                                 goto out;
                         }
                 }
                 do_promote(gl);
         }
 out:
         clear_bit(GLF_LOCK, &gl->gl_flags);
 }
 
 static bool is_system_glock(struct gfs2_glock *gl)
 {
         struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
         struct gfs2_inode *m_ip = GFS2_I(sdp->sd_statfs_inode);
 
         if (gl == m_ip->i_gl)
                 return true;
         return false;
 }
 
 /**
  * do_xmote - Calls the DLM to change the state of a lock
  * @gl: The lock state
  * @gh: The holder (only for promotes)
  * @target: The target lock state
  *
  */
 
 static void do_xmote(struct gfs2_glock *gl, struct gfs2_holder *gh,
                                          unsigned int target)
 __releases(&gl->gl_lockref.lock)
 __acquires(&gl->gl_lockref.lock)
 {
         const struct gfs2_glock_operations *glops = gl->gl_ops;
         struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
         struct lm_lockstruct *ls = &sdp->sd_lockstruct;
         unsigned int lck_flags = (unsigned int)(gh ? gh->gh_flags : 0);
         int ret;
 
         if (target != LM_ST_UNLOCKED && glock_blocked_by_withdraw(gl) &&
             gh && !(gh->gh_flags & LM_FLAG_NOEXP))
                 goto skip_inval;
 
         lck_flags &= (LM_FLAG_TRY | LM_FLAG_TRY_1CB | LM_FLAG_NOEXP);
         GLOCK_BUG_ON(gl, gl->gl_state == target);
         GLOCK_BUG_ON(gl, gl->gl_state == gl->gl_target);
         if ((target == LM_ST_UNLOCKED || target == LM_ST_DEFERRED) &&
             glops->go_inval) {
                 /*
                  * If another process is already doing the invalidate, let that
                  * finish first.  The glock state machine will get back to this
                  * holder again later.
                  */
                 if (test_and_set_bit(GLF_INVALIDATE_IN_PROGRESS,
                                      &gl->gl_flags))
                         return;
                 do_error(gl, 0); /* Fail queued try locks */
         }
         gl->gl_req = target;
         set_bit(GLF_BLOCKING, &gl->gl_flags);
         if ((gl->gl_req == LM_ST_UNLOCKED) ||
             (gl->gl_state == LM_ST_EXCLUSIVE) ||
             (lck_flags & (LM_FLAG_TRY|LM_FLAG_TRY_1CB)))
                 clear_bit(GLF_BLOCKING, &gl->gl_flags);
         if (!glops->go_inval && !glops->go_sync)
                 goto skip_inval;
 
         spin_unlock(&gl->gl_lockref.lock);
         if (glops->go_sync) {
                 ret = glops->go_sync(gl);
                 /* If we had a problem syncing (due to io errors or whatever,
                  * we should not invalidate the metadata or tell dlm to
                  * release the glock to other nodes.
                  */
                 if (ret) {
                         if (cmpxchg(&sdp->sd_log_error, 0, ret)) {
                                 fs_err(sdp, "Error %d syncing glock \n", ret);
                                 gfs2_dump_glock(NULL, gl, true);
                         }
                         spin_lock(&gl->gl_lockref.lock);
                         goto skip_inval;
                 }
         }
         if (test_bit(GLF_INVALIDATE_IN_PROGRESS, &gl->gl_flags)) {
                 /*
                  * The call to go_sync should have cleared out the ail list.
                  * If there are still items, we have a problem. We ought to
                  * withdraw, but we can't because the withdraw code also uses
                  * glocks. Warn about the error, dump the glock, then fall
                  * through and wait for logd to do the withdraw for us.
                  */
                 if ((atomic_read(&gl->gl_ail_count) != 0) &&
                     (!cmpxchg(&sdp->sd_log_error, 0, -EIO))) {
                         gfs2_glock_assert_warn(gl,
                                                !atomic_read(&gl->gl_ail_count));
                         gfs2_dump_glock(NULL, gl, true);
                 }
                 glops->go_inval(gl, target == LM_ST_DEFERRED ? 0 : DIO_METADATA);
                 clear_bit(GLF_INVALIDATE_IN_PROGRESS, &gl->gl_flags);
         }
         spin_lock(&gl->gl_lockref.lock);
 
 skip_inval:
         gl->gl_lockref.count++;
         /*
          * Check for an error encountered since we called go_sync and go_inval.
          * If so, we can't withdraw from the glock code because the withdraw
          * code itself uses glocks (see function signal_our_withdraw) to
          * change the mount to read-only. Most importantly, we must not call
          * dlm to unlock the glock until the journal is in a known good state
          * (after journal replay) otherwise other nodes may use the object
          * (rgrp or dinode) and then later, journal replay will corrupt the
          * file system. The best we can do here is wait for the logd daemon
          * to see sd_log_error and withdraw, and in the meantime, requeue the
          * work for later.
          *
          * We make a special exception for some system glocks, such as the
          * system statfs inode glock, which needs to be granted before the
          * gfs2_quotad daemon can exit, and that exit needs to finish before
          * we can unmount the withdrawn file system.
          *
          * However, if we're just unlocking the lock (say, for unmount, when
          * gfs2_gl_hash_clear calls clear_glock) and recovery is complete
          * then it's okay to tell dlm to unlock it.
          */
         if (unlikely(sdp->sd_log_error) && !gfs2_withdrawing_or_withdrawn(sdp))
                 gfs2_withdraw_delayed(sdp);
         if (glock_blocked_by_withdraw(gl) &&
             (target != LM_ST_UNLOCKED ||
              test_bit(SDF_WITHDRAW_RECOVERY, &sdp->sd_flags))) {
                 if (!is_system_glock(gl)) {
                         request_demote(gl, LM_ST_UNLOCKED, 0, false);
                         /*
                          * Ordinarily, we would call dlm and its callback would call
                          * finish_xmote, which would call state_change() to the new state.
                          * Since we withdrew, we won't call dlm, so call state_change
                          * manually, but to the UNLOCKED state we desire.
                          */
                         state_change(gl, LM_ST_UNLOCKED);
                         /*
                          * We skip telling dlm to do the locking, so we won't get a
                          * reply that would otherwise clear GLF_LOCK. So we clear it here.
                          */
                         clear_bit(GLF_LOCK, &gl->gl_flags);
                         clear_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags);
                         gfs2_glock_queue_work(gl, GL_GLOCK_DFT_HOLD);
                         return;
                 } else {
                         clear_bit(GLF_INVALIDATE_IN_PROGRESS, &gl->gl_flags);
                 }
         }
 
         if (ls->ls_ops->lm_lock) {
                 spin_unlock(&gl->gl_lockref.lock);
                 ret = ls->ls_ops->lm_lock(gl, target, lck_flags);
                 spin_lock(&gl->gl_lockref.lock);
 
                 if (ret == -EINVAL && gl->gl_target == LM_ST_UNLOCKED &&
                     target == LM_ST_UNLOCKED &&
                     test_bit(DFL_UNMOUNT, &ls->ls_recover_flags)) {
                         /*
                          * The lockspace has been released and the lock has
                          * been unlocked implicitly.
                          */
                 } else if (ret) {
                         fs_err(sdp, "lm_lock ret %d\n", ret);
                         target = gl->gl_state | LM_OUT_ERROR;
                 } else {
                         /* The operation will be completed asynchronously. */
                         return;
                 }
         }
 
         /* Complete the operation now. */
         finish_xmote(gl, target);
         gfs2_glock_queue_work(gl, 0);
 }
 
 /**
  * run_queue - do all outstanding tasks related to a glock
  * @gl: The glock in question
  * @nonblock: True if we must not block in run_queue
  *
  */
 
 static void run_queue(struct gfs2_glock *gl, const int nonblock)
 __releases(&gl->gl_lockref.lock)
 __acquires(&gl->gl_lockref.lock)
 {
         struct gfs2_holder *gh = NULL;
 
         if (test_bit(GLF_LOCK, &gl->gl_flags))
                 return;
         set_bit(GLF_LOCK, &gl->gl_flags);
 
         GLOCK_BUG_ON(gl, test_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags));
 
         if (test_bit(GLF_DEMOTE, &gl->gl_flags) &&
             gl->gl_demote_state != gl->gl_state) {
                 if (find_first_holder(gl))
                         goto out_unlock;
                 if (nonblock)
                         goto out_sched;
                 set_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags);
                 GLOCK_BUG_ON(gl, gl->gl_demote_state == LM_ST_EXCLUSIVE);
                 gl->gl_target = gl->gl_demote_state;
         } else {
                 if (test_bit(GLF_DEMOTE, &gl->gl_flags))
                         gfs2_demote_wake(gl);
                 if (do_promote(gl))
                         goto out_unlock;
                 gh = find_first_waiter(gl);
                 gl->gl_target = gh->gh_state;
                 if (!(gh->gh_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB)))
                         do_error(gl, 0); /* Fail queued try locks */
         }
         do_xmote(gl, gh, gl->gl_target);
         return;
 
 out_sched:
         clear_bit(GLF_LOCK, &gl->gl_flags);
         smp_mb__after_atomic();
         gl->gl_lockref.count++;
         gfs2_glock_queue_work(gl, 0);
         return;
 
 out_unlock:
         clear_bit(GLF_LOCK, &gl->gl_flags);
         smp_mb__after_atomic();
 }
 
 /**
  * glock_set_object - set the gl_object field of a glock
  * @gl: the glock
  * @object: the object
  */
 void glock_set_object(struct gfs2_glock *gl, void *object)
 {
         void *prev_object;
 
         spin_lock(&gl->gl_lockref.lock);
         prev_object = gl->gl_object;
         gl->gl_object = object;
         spin_unlock(&gl->gl_lockref.lock);
         if (gfs2_assert_warn(gl->gl_name.ln_sbd, prev_object == NULL)) {
                 pr_warn("glock=%u/%llx\n",
                         gl->gl_name.ln_type,
                         (unsigned long long)gl->gl_name.ln_number);
                 gfs2_dump_glock(NULL, gl, true);
         }
 }
 
 /**
  * glock_clear_object - clear the gl_object field of a glock
  * @gl: the glock
  * @object: object the glock currently points at
  */
 void glock_clear_object(struct gfs2_glock *gl, void *object)
 {
         void *prev_object;
 
         spin_lock(&gl->gl_lockref.lock);
         prev_object = gl->gl_object;
         gl->gl_object = NULL;
         spin_unlock(&gl->gl_lockref.lock);
         if (gfs2_assert_warn(gl->gl_name.ln_sbd, prev_object == object)) {
                 pr_warn("glock=%u/%llx\n",
                         gl->gl_name.ln_type,
                         (unsigned long long)gl->gl_name.ln_number);
                 gfs2_dump_glock(NULL, gl, true);
         }
 }
 
 void gfs2_inode_remember_delete(struct gfs2_glock *gl, u64 generation)
 {
         struct gfs2_inode_lvb *ri = (void *)gl->gl_lksb.sb_lvbptr;
 
         if (ri->ri_magic == 0)
                 ri->ri_magic = cpu_to_be32(GFS2_MAGIC);
         if (ri->ri_magic == cpu_to_be32(GFS2_MAGIC))
                 ri->ri_generation_deleted = cpu_to_be64(generation);
 }
 
 bool gfs2_inode_already_deleted(struct gfs2_glock *gl, u64 generation)
 {
         struct gfs2_inode_lvb *ri = (void *)gl->gl_lksb.sb_lvbptr;
 
         if (ri->ri_magic != cpu_to_be32(GFS2_MAGIC))
                 return false;
         return generation <= be64_to_cpu(ri->ri_generation_deleted);
 }
 
 static void gfs2_glock_poke(struct gfs2_glock *gl)
 {
         int flags = LM_FLAG_TRY_1CB | LM_FLAG_ANY | GL_SKIP;
         struct gfs2_holder gh;
         int error;
 
         __gfs2_holder_init(gl, LM_ST_SHARED, flags, &gh, _RET_IP_);
         error = gfs2_glock_nq(&gh);
         if (!error)
                 gfs2_glock_dq(&gh);
         gfs2_holder_uninit(&gh);
 }
 
 static bool gfs2_try_evict(struct gfs2_glock *gl)
 {
         struct gfs2_inode *ip;
         bool evicted = false;
 
         /*
          * If there is contention on the iopen glock and we have an inode, try
          * to grab and release the inode so that it can be evicted.  This will
          * allow the remote node to go ahead and delete the inode without us
          * having to do it, which will avoid rgrp glock thrashing.
          *
          * The remote node is likely still holding the corresponding inode
          * glock, so it will run before we get to verify that the delete has
          * happened below.
          */
         spin_lock(&gl->gl_lockref.lock);
         ip = gl->gl_object;
         if (ip && !igrab(&ip->i_inode))
                 ip = NULL;
         spin_unlock(&gl->gl_lockref.lock);
         if (ip) {
                 gl->gl_no_formal_ino = ip->i_no_formal_ino;
                 set_bit(GIF_DEFERRED_DELETE, &ip->i_flags);
                 d_prune_aliases(&ip->i_inode);
                 iput(&ip->i_inode);
 
                 /* If the inode was evicted, gl->gl_object will now be NULL. */
                 spin_lock(&gl->gl_lockref.lock);
                 ip = gl->gl_object;
                 if (ip) {
                         clear_bit(GIF_DEFERRED_DELETE, &ip->i_flags);
                         if (!igrab(&ip->i_inode))
                                 ip = NULL;
                 }
                 spin_unlock(&gl->gl_lockref.lock);
                 if (ip) {
                         gfs2_glock_poke(ip->i_gl);
                         iput(&ip->i_inode);
                 }
                 evicted = !ip;
         }
         return evicted;
 }
 
 bool gfs2_queue_try_to_evict(struct gfs2_glock *gl)
 {
         struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
 
         if (test_and_set_bit(GLF_TRY_TO_EVICT, &gl->gl_flags))
                 return false;
         return queue_delayed_work(sdp->sd_delete_wq,
                                   &gl->gl_delete, 0);
 }
 
 static bool gfs2_queue_verify_evict(struct gfs2_glock *gl)
 {
         struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
 
         if (test_and_set_bit(GLF_VERIFY_EVICT, &gl->gl_flags))
                 return false;
         return queue_delayed_work(sdp->sd_delete_wq,
                                   &gl->gl_delete, 5 * HZ);
 }
 
 static void delete_work_func(struct work_struct *work)
 {
         struct delayed_work *dwork = to_delayed_work(work);
         struct gfs2_glock *gl = container_of(dwork, struct gfs2_glock, gl_delete);
         struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
         struct inode *inode;
         u64 no_addr = gl->gl_name.ln_number;
 
         if (test_and_clear_bit(GLF_TRY_TO_EVICT, &gl->gl_flags)) {
                 /*
                  * If we can evict the inode, give the remote node trying to
                  * delete the inode some time before verifying that the delete
                  * has happened.  Otherwise, if we cause contention on the inode glock
                  * immediately, the remote node will think that we still have
                  * the inode in use, and so it will give up waiting.
                  *
                  * If we can't evict the inode, signal to the remote node that
                  * the inode is still in use.  We'll later try to delete the
                  * inode locally in gfs2_evict_inode.
                  *
                  * FIXME: We only need to verify that the remote node has
                  * deleted the inode because nodes before this remote delete
                  * rework won't cooperate.  At a later time, when we no longer
                  * care about compatibility with such nodes, we can skip this
                  * step entirely.
                  */
                 if (gfs2_try_evict(gl)) {
                         if (test_bit(SDF_KILL, &sdp->sd_flags))
                                 goto out;
                         if (gfs2_queue_verify_evict(gl))
                                 return;
                 }
                 goto out;
         }
 
         if (test_and_clear_bit(GLF_VERIFY_EVICT, &gl->gl_flags)) {
                 inode = gfs2_lookup_by_inum(sdp, no_addr, gl->gl_no_formal_ino,
                                             GFS2_BLKST_UNLINKED);
                 if (IS_ERR(inode)) {
                         if (PTR_ERR(inode) == -EAGAIN &&
                             !test_bit(SDF_KILL, &sdp->sd_flags) &&
                             gfs2_queue_verify_evict(gl))
                                 return;
                 } else {
                         d_prune_aliases(inode);
                         iput(inode);
                 }
         }
 
 out:
         gfs2_glock_put(gl);
 }
 
 static void glock_work_func(struct work_struct *work)
 {
         unsigned long delay = 0;
         struct gfs2_glock *gl = container_of(work, struct gfs2_glock, gl_work.work);
         unsigned int drop_refs = 1;
 
         spin_lock(&gl->gl_lockref.lock);
         if (test_bit(GLF_HAVE_REPLY, &gl->gl_flags)) {
                 clear_bit(GLF_HAVE_REPLY, &gl->gl_flags);
                 finish_xmote(gl, gl->gl_reply);
                 drop_refs++;
         }
         if (test_bit(GLF_PENDING_DEMOTE, &gl->gl_flags) &&
             gl->gl_state != LM_ST_UNLOCKED &&
             gl->gl_demote_state != LM_ST_EXCLUSIVE) {
                 if (gl->gl_name.ln_type == LM_TYPE_INODE) {
                         unsigned long holdtime, now = jiffies;
 
                         holdtime = gl->gl_tchange + gl->gl_hold_time;
                         if (time_before(now, holdtime))
                                 delay = holdtime - now;
                 }
 
                 if (!delay) {
                         clear_bit(GLF_PENDING_DEMOTE, &gl->gl_flags);
                         gfs2_set_demote(gl);
                 }
         }
         run_queue(gl, 0);
         if (delay) {
                 /* Keep one glock reference for the work we requeue. */
                 drop_refs--;
                 gfs2_glock_queue_work(gl, delay);
         }
 
         /* Drop the remaining glock references manually. */
         GLOCK_BUG_ON(gl, gl->gl_lockref.count < drop_refs);
         gl->gl_lockref.count -= drop_refs;
         if (!gl->gl_lockref.count) {
                 if (gl->gl_state == LM_ST_UNLOCKED) {
                         __gfs2_glock_put(gl);
                         return;
                 }
                 gfs2_glock_add_to_lru(gl);
         }
         spin_unlock(&gl->gl_lockref.lock);
 }
 
 static struct gfs2_glock *find_insert_glock(struct lm_lockname *name,
                                             struct gfs2_glock *new)
 {
         struct wait_glock_queue wait;
         wait_queue_head_t *wq = glock_waitqueue(name);
         struct gfs2_glock *gl;
 
         wait.name = name;
         init_wait(&wait.wait);
         wait.wait.func = glock_wake_function;
 
 again:
         prepare_to_wait(wq, &wait.wait, TASK_UNINTERRUPTIBLE);
         rcu_read_lock();
         if (new) {
                 gl = rhashtable_lookup_get_insert_fast(&gl_hash_table,
                         &new->gl_node, ht_parms);
                 if (IS_ERR(gl))
                         goto out;
         } else {
                 gl = rhashtable_lookup_fast(&gl_hash_table,
                         name, ht_parms);
         }
         if (gl && !lockref_get_not_dead(&gl->gl_lockref)) {
                 rcu_read_unlock();
                 schedule();
                 goto again;
         }
 out:
         rcu_read_unlock();
         finish_wait(wq, &wait.wait);
         if (gl)
                 gfs2_glock_remove_from_lru(gl);
         return gl;
 }
 
 /**
  * gfs2_glock_get() - Get a glock, or create one if one doesn't exist
  * @sdp: The GFS2 superblock
  * @number: the lock number
  * @glops: The glock_operations to use
  * @create: If 0, don't create the glock if it doesn't exist
  * @glp: the glock is returned here
  *
  * This does not lock a glock, just finds/creates structures for one.
  *
  * Returns: errno
  */
 
 int gfs2_glock_get(struct gfs2_sbd *sdp, u64 number,
                    const struct gfs2_glock_operations *glops, int create,
                    struct gfs2_glock **glp)
 {
         struct super_block *s = sdp->sd_vfs;
         struct lm_lockname name = { .ln_number = number,
                                     .ln_type = glops->go_type,
                                     .ln_sbd = sdp };
         struct gfs2_glock *gl, *tmp;
         struct address_space *mapping;
 
         gl = find_insert_glock(&name, NULL);
         if (gl)
                 goto found;
         if (!create)
                 return -ENOENT;
 
         if (glops->go_flags & GLOF_ASPACE) {
                 struct gfs2_glock_aspace *gla =
                         kmem_cache_alloc(gfs2_glock_aspace_cachep, GFP_NOFS);
                 if (!gla)
                         return -ENOMEM;
                 gl = &gla->glock;
         } else {
                 gl = kmem_cache_alloc(gfs2_glock_cachep, GFP_NOFS);
                 if (!gl)
                         return -ENOMEM;
         }
         memset(&gl->gl_lksb, 0, sizeof(struct dlm_lksb));
         gl->gl_ops = glops;
 
         if (glops->go_flags & GLOF_LVB) {
                 gl->gl_lksb.sb_lvbptr = kzalloc(GDLM_LVB_SIZE, GFP_NOFS);
                 if (!gl->gl_lksb.sb_lvbptr) {
                         gfs2_glock_dealloc(&gl->gl_rcu);
                         return -ENOMEM;
                 }
         }
 
         atomic_inc(&sdp->sd_glock_disposal);
         gl->gl_node.next = NULL;
         gl->gl_flags = BIT(GLF_INITIAL);
         if (glops->go_instantiate)
                 gl->gl_flags |= BIT(GLF_INSTANTIATE_NEEDED);
         gl->gl_name = name;
         lockdep_set_subclass(&gl->gl_lockref.lock, glops->go_subclass);
         gl->gl_lockref.count = 1;
         gl->gl_state = LM_ST_UNLOCKED;
         gl->gl_target = LM_ST_UNLOCKED;
         gl->gl_demote_state = LM_ST_EXCLUSIVE;
         gl->gl_dstamp = 0;
         preempt_disable();
         /* We use the global stats to estimate the initial per-glock stats */
         gl->gl_stats = this_cpu_ptr(sdp->sd_lkstats)->lkstats[glops->go_type];
         preempt_enable();
         gl->gl_stats.stats[GFS2_LKS_DCOUNT] = 0;
         gl->gl_stats.stats[GFS2_LKS_QCOUNT] = 0;
         gl->gl_tchange = jiffies;
         gl->gl_object = NULL;
         gl->gl_hold_time = GL_GLOCK_DFT_HOLD;
         INIT_DELAYED_WORK(&gl->gl_work, glock_work_func);
         if (gl->gl_name.ln_type == LM_TYPE_IOPEN)
                 INIT_DELAYED_WORK(&gl->gl_delete, delete_work_func);
 
         mapping = gfs2_glock2aspace(gl);
         if (mapping) {
                 mapping->a_ops = &gfs2_meta_aops;
                 mapping->host = s->s_bdev->bd_mapping->host;
                 mapping->flags = 0;
                 mapping_set_gfp_mask(mapping, GFP_NOFS);
                 mapping->i_private_data = NULL;
                 mapping->writeback_index = 0;
         }
 
         tmp = find_insert_glock(&name, gl);
         if (tmp) {
                 gfs2_glock_dealloc(&gl->gl_rcu);
                 if (atomic_dec_and_test(&sdp->sd_glock_disposal))
                         wake_up(&sdp->sd_kill_wait);
 
                 if (IS_ERR(tmp))
                         return PTR_ERR(tmp);
                 gl = tmp;
         }
 
 found:
         *glp = gl;
         return 0;
 }
 
 /**
  * __gfs2_holder_init - initialize a struct gfs2_holder in the default way
  * @gl: the glock
  * @state: the state we're requesting
  * @flags: the modifier flags
  * @gh: the holder structure
  *
  */
 
 void __gfs2_holder_init(struct gfs2_glock *gl, unsigned int state, u16 flags,
                         struct gfs2_holder *gh, unsigned long ip)
 {
         INIT_LIST_HEAD(&gh->gh_list);
         gh->gh_gl = gfs2_glock_hold(gl);
         gh->gh_ip = ip;
         gh->gh_owner_pid = get_pid(task_pid(current));
         gh->gh_state = state;
         gh->gh_flags = flags;
         gh->gh_iflags = 0;
 }
 
 /**
  * gfs2_holder_reinit - reinitialize a struct gfs2_holder so we can requeue it
  * @state: the state we're requesting
  * @flags: the modifier flags
  * @gh: the holder structure
  *
  * Don't mess with the glock.
  *
  */
 
 void gfs2_holder_reinit(unsigned int state, u16 flags, struct gfs2_holder *gh)
 {
         gh->gh_state = state;
         gh->gh_flags = flags;
         gh->gh_iflags = 0;
         gh->gh_ip = _RET_IP_;
         put_pid(gh->gh_owner_pid);
         gh->gh_owner_pid = get_pid(task_pid(current));
 }
 
 /**
  * gfs2_holder_uninit - uninitialize a holder structure (drop glock reference)
  * @gh: the holder structure
  *
  */
 
 void gfs2_holder_uninit(struct gfs2_holder *gh)
 {
         put_pid(gh->gh_owner_pid);
         gfs2_glock_put(gh->gh_gl);
         gfs2_holder_mark_uninitialized(gh);
         gh->gh_ip = 0;
 }
 
 static void gfs2_glock_update_hold_time(struct gfs2_glock *gl,
                                         unsigned long start_time)
 {
         /* Have we waited longer that a second? */
         if (time_after(jiffies, start_time + HZ)) {
                 /* Lengthen the minimum hold time. */
                 gl->gl_hold_time = min(gl->gl_hold_time + GL_GLOCK_HOLD_INCR,
                                        GL_GLOCK_MAX_HOLD);
         }
 }
 
 /**
  * gfs2_glock_holder_ready - holder is ready and its error code can be collected
  * @gh: the glock holder
  *
  * Called when a glock holder no longer needs to be waited for because it is
  * now either held (HIF_HOLDER set; gh_error == 0), or acquiring the lock has
  * failed (gh_error != 0).
  */
 
 int gfs2_glock_holder_ready(struct gfs2_holder *gh)
 {
         if (gh->gh_error || (gh->gh_flags & GL_SKIP))
                 return gh->gh_error;
         gh->gh_error = gfs2_instantiate(gh);
         if (gh->gh_error)
                 gfs2_glock_dq(gh);
         return gh->gh_error;
 }
 
 /**
  * gfs2_glock_wait - wait on a glock acquisition
  * @gh: the glock holder
  *
  * Returns: 0 on success
  */
 
 int gfs2_glock_wait(struct gfs2_holder *gh)
 {
         unsigned long start_time = jiffies;
 
         might_sleep();
         wait_on_bit(&gh->gh_iflags, HIF_WAIT, TASK_UNINTERRUPTIBLE);
         gfs2_glock_update_hold_time(gh->gh_gl, start_time);
         return gfs2_glock_holder_ready(gh);
 }
 
 static int glocks_pending(unsigned int num_gh, struct gfs2_holder *ghs)
 {
         int i;
 
         for (i = 0; i < num_gh; i++)
                 if (test_bit(HIF_WAIT, &ghs[i].gh_iflags))
                         return 1;
         return 0;
 }
 
 /**
  * gfs2_glock_async_wait - wait on multiple asynchronous glock acquisitions
  * @num_gh: the number of holders in the array
  * @ghs: the glock holder array
  *
  * Returns: 0 on success, meaning all glocks have been granted and are held.
  *          -ESTALE if the request timed out, meaning all glocks were released,
  *          and the caller should retry the operation.
  */
 
 int gfs2_glock_async_wait(unsigned int num_gh, struct gfs2_holder *ghs)
 {
         struct gfs2_sbd *sdp = ghs[0].gh_gl->gl_name.ln_sbd;
         int i, ret = 0, timeout = 0;
         unsigned long start_time = jiffies;
 
         might_sleep();
         /*
          * Total up the (minimum hold time * 2) of all glocks and use that to
          * determine the max amount of time we should wait.
          */
         for (i = 0; i < num_gh; i++)
                 timeout += ghs[i].gh_gl->gl_hold_time << 1;
 
         if (!wait_event_timeout(sdp->sd_async_glock_wait,
                                 !glocks_pending(num_gh, ghs), timeout)) {
                 ret = -ESTALE; /* request timed out. */
                 goto out;
         }
 
         for (i = 0; i < num_gh; i++) {
                 struct gfs2_holder *gh = &ghs[i];
                 int ret2;
 
                 if (test_bit(HIF_HOLDER, &gh->gh_iflags)) {
                         gfs2_glock_update_hold_time(gh->gh_gl,
                                                     start_time);
                 }
                 ret2 = gfs2_glock_holder_ready(gh);
                 if (!ret)
                         ret = ret2;
         }
 
 out:
         if (ret) {
                 for (i = 0; i < num_gh; i++) {
                         struct gfs2_holder *gh = &ghs[i];
 
                         gfs2_glock_dq(gh);
                 }
         }
         return ret;
 }
 
 /**
  * request_demote - process a demote request
  * @gl: the glock
  * @state: the state the caller wants us to change to
  * @delay: zero to demote immediately; otherwise pending demote
  * @remote: true if this came from a different cluster node
  *
  * There are only two requests that we are going to see in actual
  * practise: LM_ST_SHARED and LM_ST_UNLOCKED
  */
 
 static void request_demote(struct gfs2_glock *gl, unsigned int state,
                            unsigned long delay, bool remote)
 {
         if (delay)
                 set_bit(GLF_PENDING_DEMOTE, &gl->gl_flags);
         else
                 gfs2_set_demote(gl);
         if (gl->gl_demote_state == LM_ST_EXCLUSIVE) {
                 gl->gl_demote_state = state;
                 gl->gl_demote_time = jiffies;
         } else if (gl->gl_demote_state != LM_ST_UNLOCKED &&
                         gl->gl_demote_state != state) {
                 gl->gl_demote_state = LM_ST_UNLOCKED;
         }
         if (gl->gl_ops->go_callback)
                 gl->gl_ops->go_callback(gl, remote);
         trace_gfs2_demote_rq(gl, remote);
 }
 
 void gfs2_print_dbg(struct seq_file *seq, const char *fmt, ...)
 {
         struct va_format vaf;
         va_list args;
 
         va_start(args, fmt);
 
         if (seq) {
                 seq_vprintf(seq, fmt, args);
         } else {
                 vaf.fmt = fmt;
                 vaf.va = &args;
 
                 pr_err("%pV", &vaf);
         }
 
         va_end(args);
 }
 
 static inline bool pid_is_meaningful(const struct gfs2_holder *gh)
 {
         if (!(gh->gh_flags & GL_NOPID))
                 return true;
         if (gh->gh_state == LM_ST_UNLOCKED)
                 return true;
         return false;
 }
 
 /**
  * add_to_queue - Add a holder to the wait queue (but look for recursion)
  * @gh: the holder structure to add
  *
  * Eventually we should move the recursive locking trap to a
  * debugging option or something like that. This is the fast
  * path and needs to have the minimum number of distractions.
  * 
  */
 
 static inline void add_to_queue(struct gfs2_holder *gh)
 __releases(&gl->gl_lockref.lock)
 __acquires(&gl->gl_lockref.lock)
 {
         struct gfs2_glock *gl = gh->gh_gl;
         struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
         struct list_head *insert_pt = NULL;
         struct gfs2_holder *gh2;
         int try_futile = 0;
 
         GLOCK_BUG_ON(gl, gh->gh_owner_pid == NULL);
         if (test_and_set_bit(HIF_WAIT, &gh->gh_iflags))
                 GLOCK_BUG_ON(gl, true);
 
         if (gh->gh_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB)) {
                 if (test_bit(GLF_LOCK, &gl->gl_flags)) {
                         struct gfs2_holder *current_gh;
 
                         current_gh = find_first_holder(gl);
                         try_futile = !may_grant(gl, current_gh, gh);
                 }
                 if (test_bit(GLF_INVALIDATE_IN_PROGRESS, &gl->gl_flags))
                         goto fail;
         }
 
         list_for_each_entry(gh2, &gl->gl_holders, gh_list) {
                 if (likely(gh2->gh_owner_pid != gh->gh_owner_pid))
                         continue;
                 if (gh->gh_gl->gl_ops->go_type == LM_TYPE_FLOCK)
                         continue;
                 if (!pid_is_meaningful(gh2))
                         continue;
                 goto trap_recursive;
         }
         list_for_each_entry(gh2, &gl->gl_holders, gh_list) {
                 if (try_futile &&
                     !(gh2->gh_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB))) {
 fail:
                         gh->gh_error = GLR_TRYFAILED;
                         gfs2_holder_wake(gh);
                         return;
                 }
                 if (test_bit(HIF_HOLDER, &gh2->gh_iflags))
                         continue;
         }
         trace_gfs2_glock_queue(gh, 1);
         gfs2_glstats_inc(gl, GFS2_LKS_QCOUNT);
         gfs2_sbstats_inc(gl, GFS2_LKS_QCOUNT);
         if (likely(insert_pt == NULL)) {
                 list_add_tail(&gh->gh_list, &gl->gl_holders);
                 return;
         }
         list_add_tail(&gh->gh_list, insert_pt);
         spin_unlock(&gl->gl_lockref.lock);
         if (sdp->sd_lockstruct.ls_ops->lm_cancel)
                 sdp->sd_lockstruct.ls_ops->lm_cancel(gl);
         spin_lock(&gl->gl_lockref.lock);
         return;
 
 trap_recursive:
         fs_err(sdp, "original: %pSR\n", (void *)gh2->gh_ip);
         fs_err(sdp, "pid: %d\n", pid_nr(gh2->gh_owner_pid));
         fs_err(sdp, "lock type: %d req lock state : %d\n",
                gh2->gh_gl->gl_name.ln_type, gh2->gh_state);
         fs_err(sdp, "new: %pSR\n", (void *)gh->gh_ip);
         fs_err(sdp, "pid: %d\n", pid_nr(gh->gh_owner_pid));
         fs_err(sdp, "lock type: %d req lock state : %d\n",
                gh->gh_gl->gl_name.ln_type, gh->gh_state);
         gfs2_dump_glock(NULL, gl, true);
         BUG();
 }
 
 /**
  * gfs2_glock_nq - enqueue a struct gfs2_holder onto a glock (acquire a glock)
  * @gh: the holder structure
  *
  * if (gh->gh_flags & GL_ASYNC), this never returns an error
  *
  * Returns: 0, GLR_TRYFAILED, or errno on failure
  */
 
 int gfs2_glock_nq(struct gfs2_holder *gh)
 {
         struct gfs2_glock *gl = gh->gh_gl;
         int error;
 
         if (glock_blocked_by_withdraw(gl) && !(gh->gh_flags & LM_FLAG_NOEXP))
                 return -EIO;
 
         if (gh->gh_flags & GL_NOBLOCK) {
                 struct gfs2_holder *current_gh;
 
                 error = -ECHILD;
                 spin_lock(&gl->gl_lockref.lock);
                 if (find_last_waiter(gl))
                         goto unlock;
                 current_gh = find_first_holder(gl);
                 if (!may_grant(gl, current_gh, gh))
                         goto unlock;
                 set_bit(HIF_HOLDER, &gh->gh_iflags);
                 list_add_tail(&gh->gh_list, &gl->gl_holders);
                 trace_gfs2_promote(gh);
                 error = 0;
 unlock:
                 spin_unlock(&gl->gl_lockref.lock);
                 return error;
         }
 
         gh->gh_error = 0;
         spin_lock(&gl->gl_lockref.lock);
         add_to_queue(gh);
         if (unlikely((LM_FLAG_NOEXP & gh->gh_flags) &&
                      test_and_clear_bit(GLF_HAVE_FROZEN_REPLY, &gl->gl_flags))) {
                 set_bit(GLF_HAVE_REPLY, &gl->gl_flags);
                 gl->gl_lockref.count++;
                 gfs2_glock_queue_work(gl, 0);
         }
         run_queue(gl, 1);
         spin_unlock(&gl->gl_lockref.lock);
 
         error = 0;
         if (!(gh->gh_flags & GL_ASYNC))
                 error = gfs2_glock_wait(gh);
 
         return error;
 }
 
 /**
  * gfs2_glock_poll - poll to see if an async request has been completed
  * @gh: the holder
  *
  * Returns: 1 if the request is ready to be gfs2_glock_wait()ed on
  */
 
 int gfs2_glock_poll(struct gfs2_holder *gh)
 {
         return test_bit(HIF_WAIT, &gh->gh_iflags) ? 0 : 1;
 }
 
 static inline bool needs_demote(struct gfs2_glock *gl)
 {
         return (test_bit(GLF_DEMOTE, &gl->gl_flags) ||
                 test_bit(GLF_PENDING_DEMOTE, &gl->gl_flags));
 }
 
 static void __gfs2_glock_dq(struct gfs2_holder *gh)
 {
         struct gfs2_glock *gl = gh->gh_gl;
         unsigned delay = 0;
         int fast_path = 0;
 
         /*
          * This holder should not be cached, so mark it for demote.
          * Note: this should be done before the check for needs_demote
          * below.
          */
         if (gh->gh_flags & GL_NOCACHE)
                 request_demote(gl, LM_ST_UNLOCKED, 0, false);
 
         list_del_init(&gh->gh_list);
         clear_bit(HIF_HOLDER, &gh->gh_iflags);
         trace_gfs2_glock_queue(gh, 0);
 
         /*
          * If there hasn't been a demote request we are done.
          * (Let the remaining holders, if any, keep holding it.)
          */
         if (!needs_demote(gl)) {
                 if (list_empty(&gl->gl_holders))
                         fast_path = 1;
         }
 
         if (unlikely(!fast_path)) {
                 gl->gl_lockref.count++;
                 if (test_bit(GLF_PENDING_DEMOTE, &gl->gl_flags) &&
                     !test_bit(GLF_DEMOTE, &gl->gl_flags) &&
                     gl->gl_name.ln_type == LM_TYPE_INODE)
                         delay = gl->gl_hold_time;
                 gfs2_glock_queue_work(gl, delay);
         }
 }
 
 /**
  * gfs2_glock_dq - dequeue a struct gfs2_holder from a glock (release a glock)
  * @gh: the glock holder
  *
  */
 void gfs2_glock_dq(struct gfs2_holder *gh)
 {
         struct gfs2_glock *gl = gh->gh_gl;
         struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
 
         spin_lock(&gl->gl_lockref.lock);
         if (!gfs2_holder_queued(gh)) {
                 /*
                  * May have already been dequeued because the locking request
                  * was GL_ASYNC and it has failed in the meantime.
                  */
                 goto out;
         }
 
         if (list_is_first(&gh->gh_list, &gl->gl_holders) &&
             !test_bit(HIF_HOLDER, &gh->gh_iflags)) {
                 spin_unlock(&gl->gl_lockref.lock);
                 gl->gl_name.ln_sbd->sd_lockstruct.ls_ops->lm_cancel(gl);
                 wait_on_bit(&gh->gh_iflags, HIF_WAIT, TASK_UNINTERRUPTIBLE);
                 spin_lock(&gl->gl_lockref.lock);
         }
 
         /*
          * If we're in the process of file system withdraw, we cannot just
          * dequeue any glocks until our journal is recovered, lest we introduce
          * file system corruption. We need two exceptions to this rule: We need
          * to allow unlocking of nondisk glocks and the glock for our own
          * journal that needs recovery.
          */
         if (test_bit(SDF_WITHDRAW_RECOVERY, &sdp->sd_flags) &&
             glock_blocked_by_withdraw(gl) &&
             gh->gh_gl != sdp->sd_jinode_gl) {
                 sdp->sd_glock_dqs_held++;
                 spin_unlock(&gl->gl_lockref.lock);
                 might_sleep();
                 wait_on_bit(&sdp->sd_flags, SDF_WITHDRAW_RECOVERY,
                             TASK_UNINTERRUPTIBLE);
                 spin_lock(&gl->gl_lockref.lock);
         }
 
         __gfs2_glock_dq(gh);
 out:
         spin_unlock(&gl->gl_lockref.lock);
 }
 
 void gfs2_glock_dq_wait(struct gfs2_holder *gh)
 {
         struct gfs2_glock *gl = gh->gh_gl;
         gfs2_glock_dq(gh);
         might_sleep();
         wait_on_bit(&gl->gl_flags, GLF_DEMOTE, TASK_UNINTERRUPTIBLE);
 }
 
 /**
  * gfs2_glock_dq_uninit - dequeue a holder from a glock and initialize it
  * @gh: the holder structure
  *
  */
 
 void gfs2_glock_dq_uninit(struct gfs2_holder *gh)
 {
         gfs2_glock_dq(gh);
         gfs2_holder_uninit(gh);
 }
 
 /**
  * gfs2_glock_nq_num - acquire a glock based on lock number
  * @sdp: the filesystem
  * @number: the lock number
  * @glops: the glock operations for the type of glock
  * @state: the state to acquire the glock in
  * @flags: modifier flags for the acquisition
  * @gh: the struct gfs2_holder
  *
  * Returns: errno
  */
 
 int gfs2_glock_nq_num(struct gfs2_sbd *sdp, u64 number,
                       const struct gfs2_glock_operations *glops,
                       unsigned int state, u16 flags, struct gfs2_holder *gh)
 {
         struct gfs2_glock *gl;
         int error;
 
         error = gfs2_glock_get(sdp, number, glops, CREATE, &gl);
         if (!error) {
                 error = gfs2_glock_nq_init(gl, state, flags, gh);
                 gfs2_glock_put(gl);
         }
 
         return error;
 }
 
 /**
  * glock_compare - Compare two struct gfs2_glock structures for sorting
  * @arg_a: the first structure
  * @arg_b: the second structure
  *
  */
 
 static int glock_compare(const void *arg_a, const void *arg_b)
 {
         const struct gfs2_holder *gh_a = *(const struct gfs2_holder **)arg_a;
         const struct gfs2_holder *gh_b = *(const struct gfs2_holder **)arg_b;
         const struct lm_lockname *a = &gh_a->gh_gl->gl_name;
         const struct lm_lockname *b = &gh_b->gh_gl->gl_name;
 
         if (a->ln_number > b->ln_number)
                 return 1;
         if (a->ln_number < b->ln_number)
                 return -1;
         BUG_ON(gh_a->gh_gl->gl_ops->go_type == gh_b->gh_gl->gl_ops->go_type);
         return 0;
 }
 
 /**
  * nq_m_sync - synchronously acquire more than one glock in deadlock free order
  * @num_gh: the number of structures
  * @ghs: an array of struct gfs2_holder structures
  * @p: placeholder for the holder structure to pass back
  *
  * Returns: 0 on success (all glocks acquired),
  *          errno on failure (no glocks acquired)
  */
 
 static int nq_m_sync(unsigned int num_gh, struct gfs2_holder *ghs,
                      struct gfs2_holder **p)
 {
         unsigned int x;
         int error = 0;
 
         for (x = 0; x < num_gh; x++)
                 p[x] = &ghs[x];
 
         sort(p, num_gh, sizeof(struct gfs2_holder *), glock_compare, NULL);
 
         for (x = 0; x < num_gh; x++) {
                 error = gfs2_glock_nq(p[x]);
                 if (error) {
                         while (x--)
                                 gfs2_glock_dq(p[x]);
                         break;
                 }
         }
 
         return error;
 }
 
 /**
  * gfs2_glock_nq_m - acquire multiple glocks
  * @num_gh: the number of structures
  * @ghs: an array of struct gfs2_holder structures
  *
  * Returns: 0 on success (all glocks acquired),
  *          errno on failure (no glocks acquired)
  */
 
 int gfs2_glock_nq_m(unsigned int num_gh, struct gfs2_holder *ghs)
 {
         struct gfs2_holder *tmp[4];
         struct gfs2_holder **pph = tmp;
         int error = 0;
 
         switch(num_gh) {
         case 0:
                 return 0;
         case 1:
                 return gfs2_glock_nq(ghs);
         default:
                 if (num_gh <= 4)
                         break;
                 pph = kmalloc_array(num_gh, sizeof(struct gfs2_holder *),
                                     GFP_NOFS);
                 if (!pph)
                         return -ENOMEM;
         }
 
         error = nq_m_sync(num_gh, ghs, pph);
 
         if (pph != tmp)
                 kfree(pph);
 
         return error;
 }
 
 /**
  * gfs2_glock_dq_m - release multiple glocks
  * @num_gh: the number of structures
  * @ghs: an array of struct gfs2_holder structures
  *
  */
 
 void gfs2_glock_dq_m(unsigned int num_gh, struct gfs2_holder *ghs)
 {
         while (num_gh--)
                 gfs2_glock_dq(&ghs[num_gh]);
 }
 
 void gfs2_glock_cb(struct gfs2_glock *gl, unsigned int state)
 {
         unsigned long delay = 0;
         unsigned long holdtime;
         unsigned long now = jiffies;
 
         gfs2_glock_hold(gl);
         spin_lock(&gl->gl_lockref.lock);
         holdtime = gl->gl_tchange + gl->gl_hold_time;
         if (!list_empty(&gl->gl_holders) &&
             gl->gl_name.ln_type == LM_TYPE_INODE) {
                 if (time_before(now, holdtime))
                         delay = holdtime - now;
                 if (test_bit(GLF_HAVE_REPLY, &gl->gl_flags))
                         delay = gl->gl_hold_time;
         }
         request_demote(gl, state, delay, true);
         gfs2_glock_queue_work(gl, delay);
         spin_unlock(&gl->gl_lockref.lock);
 }
 
 /**
  * gfs2_should_freeze - Figure out if glock should be frozen
  * @gl: The glock in question
  *
  * Glocks are not frozen if (a) the result of the dlm operation is
  * an error, (b) the locking operation was an unlock operation or
  * (c) if there is a "noexp" flagged request anywhere in the queue
  *
  * Returns: 1 if freezing should occur, 0 otherwise
  */
 
 static int gfs2_should_freeze(const struct gfs2_glock *gl)
 {
         const struct gfs2_holder *gh;
 
         if (gl->gl_reply & ~LM_OUT_ST_MASK)
                 return 0;
         if (gl->gl_target == LM_ST_UNLOCKED)
                 return 0;
 
         list_for_each_entry(gh, &gl->gl_holders, gh_list) {
                 if (test_bit(HIF_HOLDER, &gh->gh_iflags))
                         continue;
                 if (LM_FLAG_NOEXP & gh->gh_flags)
                         return 0;
         }
 
         return 1;
 }
 
 /**
  * gfs2_glock_complete - Callback used by locking
  * @gl: Pointer to the glock
  * @ret: The return value from the dlm
  *
  * The gl_reply field is under the gl_lockref.lock lock so that it is ok
  * to use a bitfield shared with other glock state fields.
  */
 
 void gfs2_glock_complete(struct gfs2_glock *gl, int ret)
 {
         struct lm_lockstruct *ls = &gl->gl_name.ln_sbd->sd_lockstruct;
 
         spin_lock(&gl->gl_lockref.lock);
         gl->gl_reply = ret;
 
         if (unlikely(test_bit(DFL_BLOCK_LOCKS, &ls->ls_recover_flags))) {
                 if (gfs2_should_freeze(gl)) {
                         set_bit(GLF_HAVE_FROZEN_REPLY, &gl->gl_flags);
                         spin_unlock(&gl->gl_lockref.lock);
                         return;
                 }
         }
 
         gl->gl_lockref.count++;
         set_bit(GLF_HAVE_REPLY, &gl->gl_flags);
         gfs2_glock_queue_work(gl, 0);
         spin_unlock(&gl->gl_lockref.lock);
 }
 
 static int glock_cmp(void *priv, const struct list_head *a,
                      const struct list_head *b)
 {
         struct gfs2_glock *gla, *glb;
 
         gla = list_entry(a, struct gfs2_glock, gl_lru);
         glb = list_entry(b, struct gfs2_glock, gl_lru);
 
         if (gla->gl_name.ln_number > glb->gl_name.ln_number)
                 return 1;
         if (gla->gl_name.ln_number < glb->gl_name.ln_number)
                 return -1;
 
         return 0;
 }
 
 static bool can_free_glock(struct gfs2_glock *gl)
 {
         struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
 
         return !test_bit(GLF_LOCK, &gl->gl_flags) &&
                !gl->gl_lockref.count &&
                (!test_bit(GLF_LFLUSH, &gl->gl_flags) ||
                 test_bit(SDF_KILL, &sdp->sd_flags));
 }
 
 /**
  * gfs2_dispose_glock_lru - Demote a list of glocks
  * @list: The list to dispose of
  *
  * Disposing of glocks may involve disk accesses, so that here we sort
  * the glocks by number (i.e. disk location of the inodes) so that if
  * there are any such accesses, they'll be sent in order (mostly).
  *
  * Must be called under the lru_lock, but may drop and retake this
  * lock. While the lru_lock is dropped, entries may vanish from the
  * list, but no new entries will appear on the list (since it is
  * private)
  */
 
 static unsigned long gfs2_dispose_glock_lru(struct list_head *list)
 __releases(&lru_lock)
 __acquires(&lru_lock)
 {
         struct gfs2_glock *gl;
         unsigned long freed = 0;
 
         list_sort(NULL, list, glock_cmp);
 
         while(!list_empty(list)) {
                 gl = list_first_entry(list, struct gfs2_glock, gl_lru);
                 if (!spin_trylock(&gl->gl_lockref.lock)) {
 add_back_to_lru:
                         list_move(&gl->gl_lru, &lru_list);
                         continue;
                 }
                 if (!can_free_glock(gl)) {
                         spin_unlock(&gl->gl_lockref.lock);
                         goto add_back_to_lru;
                 }
                 list_del_init(&gl->gl_lru);
                 atomic_dec(&lru_count);
                 clear_bit(GLF_LRU, &gl->gl_flags);
                 freed++;
                 gl->gl_lockref.count++;
                 if (gl->gl_state != LM_ST_UNLOCKED)
                         request_demote(gl, LM_ST_UNLOCKED, 0, false);
                 gfs2_glock_queue_work(gl, 0);
                 spin_unlock(&gl->gl_lockref.lock);
                 cond_resched_lock(&lru_lock);
         }
         return freed;
 }
 
 /**
  * gfs2_scan_glock_lru - Scan the LRU looking for locks to demote
  * @nr: The number of entries to scan
  *
  * This function selects the entries on the LRU which are able to
  * be demoted, and then kicks off the process by calling
  * gfs2_dispose_glock_lru() above.
  */
 
 static unsigned long gfs2_scan_glock_lru(unsigned long nr)
 {
         struct gfs2_glock *gl, *next;
         LIST_HEAD(dispose);
         unsigned long freed = 0;
 
         spin_lock(&lru_lock);
         list_for_each_entry_safe(gl, next, &lru_list, gl_lru) {
                 if (!nr--)
                         break;
                 if (can_free_glock(gl))
                         list_move(&gl->gl_lru, &dispose);
         }
         if (!list_empty(&dispose))
                 freed = gfs2_dispose_glock_lru(&dispose);
         spin_unlock(&lru_lock);
 
         return freed;
 }
 
 static unsigned long gfs2_glock_shrink_scan(struct shrinker *shrink,
                                             struct shrink_control *sc)
 {
         if (!(sc->gfp_mask & __GFP_FS))
                 return SHRINK_STOP;
         return gfs2_scan_glock_lru(sc->nr_to_scan);
 }
 
 static unsigned long gfs2_glock_shrink_count(struct shrinker *shrink,
                                              struct shrink_control *sc)
 {
         return vfs_pressure_ratio(atomic_read(&lru_count));
 }
 
 static struct shrinker *glock_shrinker;
 
 /**
  * glock_hash_walk - Call a function for glock in a hash bucket
  * @examiner: the function
  * @sdp: the filesystem
  *
  * Note that the function can be called multiple times on the same
  * object.  So the user must ensure that the function can cope with
  * that.
  */
 
 static void glock_hash_walk(glock_examiner examiner, const struct gfs2_sbd *sdp)
 {
         struct gfs2_glock *gl;
         struct rhashtable_iter iter;
 
         rhashtable_walk_enter(&gl_hash_table, &iter);
 
         do {
                 rhashtable_walk_start(&iter);
 
                 while ((gl = rhashtable_walk_next(&iter)) && !IS_ERR(gl)) {
                         if (gl->gl_name.ln_sbd == sdp)
                                 examiner(gl);
                 }
 
                 rhashtable_walk_stop(&iter);
         } while (cond_resched(), gl == ERR_PTR(-EAGAIN));
 
         rhashtable_walk_exit(&iter);
 }
 
 void gfs2_cancel_delete_work(struct gfs2_glock *gl)
 {
         clear_bit(GLF_TRY_TO_EVICT, &gl->gl_flags);
         clear_bit(GLF_VERIFY_EVICT, &gl->gl_flags);
         if (cancel_delayed_work(&gl->gl_delete))
                 gfs2_glock_put(gl);
 }
 
 static void flush_delete_work(struct gfs2_glock *gl)
 {
         if (gl->gl_name.ln_type == LM_TYPE_IOPEN) {
                 struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
 
                 if (cancel_delayed_work(&gl->gl_delete)) {
                         queue_delayed_work(sdp->sd_delete_wq,
                                            &gl->gl_delete, 0);
                 }
         }
 }
 
 void gfs2_flush_delete_work(struct gfs2_sbd *sdp)
 {
         glock_hash_walk(flush_delete_work, sdp);
         flush_workqueue(sdp->sd_delete_wq);
 }
 
 /**
  * thaw_glock - thaw out a glock which has an unprocessed reply waiting
  * @gl: The glock to thaw
  *
  */
 
 static void thaw_glock(struct gfs2_glock *gl)
 {
         if (!test_and_clear_bit(GLF_HAVE_FROZEN_REPLY, &gl->gl_flags))
                 return;
         if (!lockref_get_not_dead(&gl->gl_lockref))
                 return;
 
         gfs2_glock_remove_from_lru(gl);
         spin_lock(&gl->gl_lockref.lock);
         set_bit(GLF_HAVE_REPLY, &gl->gl_flags);
         gfs2_glock_queue_work(gl, 0);
         spin_unlock(&gl->gl_lockref.lock);
 }
 
 /**
  * clear_glock - look at a glock and see if we can free it from glock cache
  * @gl: the glock to look at
  *
  */
 
 static void clear_glock(struct gfs2_glock *gl)
 {
         gfs2_glock_remove_from_lru(gl);
 
         spin_lock(&gl->gl_lockref.lock);
         if (!__lockref_is_dead(&gl->gl_lockref)) {
                 gl->gl_lockref.count++;
                 if (gl->gl_state != LM_ST_UNLOCKED)
                         request_demote(gl, LM_ST_UNLOCKED, 0, false);
                 gfs2_glock_queue_work(gl, 0);
         }
         spin_unlock(&gl->gl_lockref.lock);
 }
 
 /**
  * gfs2_glock_thaw - Thaw any frozen glocks
  * @sdp: The super block
  *
  */
 
 void gfs2_glock_thaw(struct gfs2_sbd *sdp)
 {
         glock_hash_walk(thaw_glock, sdp);
 }
 
 static void dump_glock(struct seq_file *seq, struct gfs2_glock *gl, bool fsid)
 {
         spin_lock(&gl->gl_lockref.lock);
         gfs2_dump_glock(seq, gl, fsid);
         spin_unlock(&gl->gl_lockref.lock);
 }
 
 static void dump_glock_func(struct gfs2_glock *gl)
 {
         dump_glock(NULL, gl, true);
 }
 
 static void withdraw_dq(struct gfs2_glock *gl)
 {
         spin_lock(&gl->gl_lockref.lock);
         if (!__lockref_is_dead(&gl->gl_lockref) &&
             glock_blocked_by_withdraw(gl))
                 do_error(gl, LM_OUT_ERROR); /* remove pending waiters */
         spin_unlock(&gl->gl_lockref.lock);
 }
 
 void gfs2_gl_dq_holders(struct gfs2_sbd *sdp)
 {
         glock_hash_walk(withdraw_dq, sdp);
 }
 
 /**
  * gfs2_gl_hash_clear - Empty out the glock hash table
  * @sdp: the filesystem
  *
  * Called when unmounting the filesystem.
  */
 
 void gfs2_gl_hash_clear(struct gfs2_sbd *sdp)
 {
         unsigned long start = jiffies;
         bool timed_out = false;
 
         set_bit(SDF_SKIP_DLM_UNLOCK, &sdp->sd_flags);
         flush_workqueue(sdp->sd_glock_wq);
         glock_hash_walk(clear_glock, sdp);
         flush_workqueue(sdp->sd_glock_wq);
 
         while (!timed_out) {
                 wait_event_timeout(sdp->sd_kill_wait,
                                    !atomic_read(&sdp->sd_glock_disposal),
                                    HZ * 60);
                 if (!atomic_read(&sdp->sd_glock_disposal))
                         break;
                 timed_out = time_after(jiffies, start + (HZ * 600));
                 fs_warn(sdp, "%u glocks left after %u seconds%s\n",
                         atomic_read(&sdp->sd_glock_disposal),
                         jiffies_to_msecs(jiffies - start) / 1000,
                         timed_out ? ":" : "; still waiting");
         }
         gfs2_lm_unmount(sdp);
         gfs2_free_dead_glocks(sdp);
         glock_hash_walk(dump_glock_func, sdp);
         destroy_workqueue(sdp->sd_glock_wq);
         sdp->sd_glock_wq = NULL;
 }
 
 static const char *state2str(unsigned state)
 {
         switch(state) {
         case LM_ST_UNLOCKED:
                 return "UN";
         case LM_ST_SHARED:
                 return "SH";
         case LM_ST_DEFERRED:
                 return "DF";
         case LM_ST_EXCLUSIVE:
                 return "EX";
         }
         return "??";
 }
 
 static const char *hflags2str(char *buf, u16 flags, unsigned long iflags)
 {
         char *p = buf;
         if (flags & LM_FLAG_TRY)
                 *p++ = 't';
         if (flags & LM_FLAG_TRY_1CB)
                 *p++ = 'T';
         if (flags & LM_FLAG_NOEXP)
                 *p++ = 'e';
         if (flags & LM_FLAG_ANY)
                 *p++ = 'A';
         if (flags & LM_FLAG_NODE_SCOPE)
                 *p++ = 'n';
         if (flags & GL_ASYNC)
                 *p++ = 'a';
         if (flags & GL_EXACT)
                 *p++ = 'E';
         if (flags & GL_NOCACHE)
                 *p++ = 'c';
         if (test_bit(HIF_HOLDER, &iflags))
                 *p++ = 'H';
         if (test_bit(HIF_WAIT, &iflags))
                 *p++ = 'W';
         if (flags & GL_SKIP)
                 *p++ = 's';
         *p = 0;
         return buf;
 }
 
 /**
  * dump_holder - print information about a glock holder
  * @seq: the seq_file struct
  * @gh: the glock holder
  * @fs_id_buf: pointer to file system id (if requested)
  *
  */
 
 static void dump_holder(struct seq_file *seq, const struct gfs2_holder *gh,
                         const char *fs_id_buf)
 {
         const char *comm = "(none)";
         pid_t owner_pid = 0;
         char flags_buf[32];
 
         rcu_read_lock();
         if (pid_is_meaningful(gh)) {
                 struct task_struct *gh_owner;
 
                 comm = "(ended)";
                 owner_pid = pid_nr(gh->gh_owner_pid);
                 gh_owner = pid_task(gh->gh_owner_pid, PIDTYPE_PID);
                 if (gh_owner)
                         comm = gh_owner->comm;
         }
         gfs2_print_dbg(seq, "%s H: s:%s f:%s e:%d p:%ld [%s] %pS\n",
                        fs_id_buf, state2str(gh->gh_state),
                        hflags2str(flags_buf, gh->gh_flags, gh->gh_iflags),
                        gh->gh_error, (long)owner_pid, comm, (void *)gh->gh_ip);
         rcu_read_unlock();
 }
 
 static const char *gflags2str(char *buf, const struct gfs2_glock *gl)
 {
         const unsigned long *gflags = &gl->gl_flags;
         char *p = buf;
 
         if (test_bit(GLF_LOCK, gflags))
                 *p++ = 'l';
         if (test_bit(GLF_DEMOTE, gflags))
                 *p++ = 'D';
         if (test_bit(GLF_PENDING_DEMOTE, gflags))
                 *p++ = 'd';
         if (test_bit(GLF_DEMOTE_IN_PROGRESS, gflags))
                 *p++ = 'p';
         if (test_bit(GLF_DIRTY, gflags))
                 *p++ = 'y';
         if (test_bit(GLF_LFLUSH, gflags))
                 *p++ = 'f';
         if (test_bit(GLF_INVALIDATE_IN_PROGRESS, gflags))
                 *p++ = 'i';
         if (test_bit(GLF_HAVE_REPLY, gflags))
                 *p++ = 'r';
         if (test_bit(GLF_INITIAL, gflags))
                 *p++ = 'a';
         if (test_bit(GLF_HAVE_FROZEN_REPLY, gflags))
                 *p++ = 'F';
         if (!list_empty(&gl->gl_holders))
                 *p++ = 'q';
         if (test_bit(GLF_LRU, gflags))
                 *p++ = 'L';
         if (gl->gl_object)
                 *p++ = 'o';
         if (test_bit(GLF_BLOCKING, gflags))
                 *p++ = 'b';
         if (test_bit(GLF_UNLOCKED, gflags))
                 *p++ = 'x';
         if (test_bit(GLF_INSTANTIATE_NEEDED, gflags))
                 *p++ = 'n';
         if (test_bit(GLF_INSTANTIATE_IN_PROG, gflags))
                 *p++ = 'N';
         if (test_bit(GLF_TRY_TO_EVICT, gflags))
                 *p++ = 'e';
         if (test_bit(GLF_VERIFY_EVICT, gflags))
                 *p++ = 'E';
         *p = 0;
         return buf;
 }
 
 /**
  * gfs2_dump_glock - print information about a glock
  * @seq: The seq_file struct
  * @gl: the glock
  * @fsid: If true, also dump the file system id
  *
  * The file format is as follows:
  * One line per object, capital letters are used to indicate objects
  * G = glock, I = Inode, R = rgrp, H = holder. Glocks are not indented,
  * other objects are indented by a single space and follow the glock to
  * which they are related. Fields are indicated by lower case letters
  * followed by a colon and the field value, except for strings which are in
  * [] so that its possible to see if they are composed of spaces for
  * example. The field's are n = number (id of the object), f = flags,
  * t = type, s = state, r = refcount, e = error, p = pid.
  *
  */
 
 void gfs2_dump_glock(struct seq_file *seq, struct gfs2_glock *gl, bool fsid)
 {
         const struct gfs2_glock_operations *glops = gl->gl_ops;
         unsigned long long dtime;
         const struct gfs2_holder *gh;
         char gflags_buf[32];
         struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
         char fs_id_buf[sizeof(sdp->sd_fsname) + 7];
         unsigned long nrpages = 0;
 
         if (gl->gl_ops->go_flags & GLOF_ASPACE) {
                 struct address_space *mapping = gfs2_glock2aspace(gl);
 
                 nrpages = mapping->nrpages;
         }
         memset(fs_id_buf, 0, sizeof(fs_id_buf));
         if (fsid && sdp) /* safety precaution */
                 sprintf(fs_id_buf, "fsid=%s: ", sdp->sd_fsname);
         dtime = jiffies - gl->gl_demote_time;
         dtime *= 1000000/HZ; /* demote time in uSec */
         if (!test_bit(GLF_DEMOTE, &gl->gl_flags))
                 dtime = 0;
         gfs2_print_dbg(seq, "%sG:  s:%s n:%u/%llx f:%s t:%s d:%s/%llu a:%d "
                        "v:%d r:%d m:%ld p:%lu\n",
                        fs_id_buf, state2str(gl->gl_state),
                        gl->gl_name.ln_type,
                        (unsigned long long)gl->gl_name.ln_number,
                        gflags2str(gflags_buf, gl),
                        state2str(gl->gl_target),
                        state2str(gl->gl_demote_state), dtime,
                        atomic_read(&gl->gl_ail_count),
                        atomic_read(&gl->gl_revokes),
                        (int)gl->gl_lockref.count, gl->gl_hold_time, nrpages);
 
         list_for_each_entry(gh, &gl->gl_holders, gh_list)
                 dump_holder(seq, gh, fs_id_buf);
 
         if (gl->gl_state != LM_ST_UNLOCKED && glops->go_dump)
                 glops->go_dump(seq, gl, fs_id_buf);
 }
 
 static int gfs2_glstats_seq_show(struct seq_file *seq, void *iter_ptr)
 {
         struct gfs2_glock *gl = iter_ptr;
 
         seq_printf(seq, "G: n:%u/%llx rtt:%llu/%llu rttb:%llu/%llu irt:%llu/%llu dcnt: %llu qcnt: %llu\n",
                    gl->gl_name.ln_type,
                    (unsigned long long)gl->gl_name.ln_number,
                    (unsigned long long)gl->gl_stats.stats[GFS2_LKS_SRTT],
                    (unsigned long long)gl->gl_stats.stats[GFS2_LKS_SRTTVAR],
                    (unsigned long long)gl->gl_stats.stats[GFS2_LKS_SRTTB],
                    (unsigned long long)gl->gl_stats.stats[GFS2_LKS_SRTTVARB],
                    (unsigned long long)gl->gl_stats.stats[GFS2_LKS_SIRT],
                    (unsigned long long)gl->gl_stats.stats[GFS2_LKS_SIRTVAR],
                    (unsigned long long)gl->gl_stats.stats[GFS2_LKS_DCOUNT],
                    (unsigned long long)gl->gl_stats.stats[GFS2_LKS_QCOUNT]);
         return 0;
 }
 
 static const char *gfs2_gltype[] = {
         "type",
         "reserved",
         "nondisk",
         "inode",
         "rgrp",
         "meta",
         "iopen",
         "flock",
         "plock",
         "quota",
         "journal",
 };
 
 static const char *gfs2_stype[] = {
         [GFS2_LKS_SRTT]         = "srtt",
         [GFS2_LKS_SRTTVAR]      = "srttvar",
         [GFS2_LKS_SRTTB]        = "srttb",
         [GFS2_LKS_SRTTVARB]     = "srttvarb",
         [GFS2_LKS_SIRT]         = "sirt",
         [GFS2_LKS_SIRTVAR]      = "sirtvar",
         [GFS2_LKS_DCOUNT]       = "dlm",
         [GFS2_LKS_QCOUNT]       = "queue",
 };
 
 #define GFS2_NR_SBSTATS (ARRAY_SIZE(gfs2_gltype) * ARRAY_SIZE(gfs2_stype))
 
 static int gfs2_sbstats_seq_show(struct seq_file *seq, void *iter_ptr)
 {
         struct gfs2_sbd *sdp = seq->private;
         loff_t pos = *(loff_t *)iter_ptr;
         unsigned index = pos >> 3;
         unsigned subindex = pos & 0x07;
         int i;
 
         if (index == 0 && subindex != 0)
                 return 0;
 
         seq_printf(seq, "%-10s %8s:", gfs2_gltype[index],
                    (index == 0) ? "cpu": gfs2_stype[subindex]);
 
         for_each_possible_cpu(i) {
                 const struct gfs2_pcpu_lkstats *lkstats = per_cpu_ptr(sdp->sd_lkstats, i);
 
                 if (index == 0)
                         seq_printf(seq, " %15u", i);
                 else
                         seq_printf(seq, " %15llu", (unsigned long long)lkstats->
                                    lkstats[index - 1].stats[subindex]);
         }
         seq_putc(seq, '\n');
         return 0;
 }
 
 int __init gfs2_glock_init(void)
 {
         int i, ret;
 
         ret = rhashtable_init(&gl_hash_table, &ht_parms);
         if (ret < 0)
                 return ret;
 
         glock_shrinker = shrinker_alloc(0, "gfs2-glock");
         if (!glock_shrinker) {
                 rhashtable_destroy(&gl_hash_table);
                 return -ENOMEM;
         }
 
         glock_shrinker->count_objects = gfs2_glock_shrink_count;
         glock_shrinker->scan_objects = gfs2_glock_shrink_scan;
 
         shrinker_register(glock_shrinker);
 
         for (i = 0; i < GLOCK_WAIT_TABLE_SIZE; i++)
                 init_waitqueue_head(glock_wait_table + i);
 
         return 0;
 }
 
 void gfs2_glock_exit(void)
 {
         shrinker_free(glock_shrinker);
         rhashtable_destroy(&gl_hash_table);
 }
 
 static void gfs2_glock_iter_next(struct gfs2_glock_iter *gi, loff_t n)
 {
         struct gfs2_glock *gl = gi->gl;
 
         if (gl) {
                 if (n == 0)
                         return;
                 gfs2_glock_put_async(gl);
         }
         for (;;) {
                 gl = rhashtable_walk_next(&gi->hti);
                 if (IS_ERR_OR_NULL(gl)) {
                         if (gl == ERR_PTR(-EAGAIN)) {
                                 n = 1;
                                 continue;
                         }
                         gl = NULL;
                         break;
                 }
                 if (gl->gl_name.ln_sbd != gi->sdp)
                         continue;
                 if (n <= 1) {
                         if (!lockref_get_not_dead(&gl->gl_lockref))
                                 continue;
                         break;
                 } else {
                         if (__lockref_is_dead(&gl->gl_lockref))
                                 continue;
                         n--;
                 }
         }
         gi->gl = gl;
 }
 
 static void *gfs2_glock_seq_start(struct seq_file *seq, loff_t *pos)
         __acquires(RCU)
 {
         struct gfs2_glock_iter *gi = seq->private;
         loff_t n;
 
         /*
          * We can either stay where we are, skip to the next hash table
          * entry, or start from the beginning.
          */
         if (*pos < gi->last_pos) {
                 rhashtable_walk_exit(&gi->hti);
                 rhashtable_walk_enter(&gl_hash_table, &gi->hti);
                 n = *pos + 1;
         } else {
                 n = *pos - gi->last_pos;
         }
 
         rhashtable_walk_start(&gi->hti);
 
         gfs2_glock_iter_next(gi, n);
         gi->last_pos = *pos;
         return gi->gl;
 }
 
 static void *gfs2_glock_seq_next(struct seq_file *seq, void *iter_ptr,
                                  loff_t *pos)
 {
         struct gfs2_glock_iter *gi = seq->private;
 
         (*pos)++;
         gi->last_pos = *pos;
         gfs2_glock_iter_next(gi, 1);
         return gi->gl;
 }
 
 static void gfs2_glock_seq_stop(struct seq_file *seq, void *iter_ptr)
         __releases(RCU)
 {
         struct gfs2_glock_iter *gi = seq->private;
 
         rhashtable_walk_stop(&gi->hti);
 }
 
 static int gfs2_glock_seq_show(struct seq_file *seq, void *iter_ptr)
 {
         dump_glock(seq, iter_ptr, false);
         return 0;
 }
 
 static void *gfs2_sbstats_seq_start(struct seq_file *seq, loff_t *pos)
 {
         preempt_disable();
         if (*pos >= GFS2_NR_SBSTATS)
                 return NULL;
         return pos;
 }
 
 static void *gfs2_sbstats_seq_next(struct seq_file *seq, void *iter_ptr,
                                    loff_t *pos)
 {
         (*pos)++;
         if (*pos >= GFS2_NR_SBSTATS)
                 return NULL;
         return pos;
 }
 
 static void gfs2_sbstats_seq_stop(struct seq_file *seq, void *iter_ptr)
 {
         preempt_enable();
 }
 
 static const struct seq_operations gfs2_glock_seq_ops = {
         .start = gfs2_glock_seq_start,
         .next  = gfs2_glock_seq_next,
         .stop  = gfs2_glock_seq_stop,
         .show  = gfs2_glock_seq_show,
 };
 
 static const struct seq_operations gfs2_glstats_seq_ops = {
         .start = gfs2_glock_seq_start,
         .next  = gfs2_glock_seq_next,
         .stop  = gfs2_glock_seq_stop,
         .show  = gfs2_glstats_seq_show,
 };
 
 static const struct seq_operations gfs2_sbstats_sops = {
         .start = gfs2_sbstats_seq_start,
         .next  = gfs2_sbstats_seq_next,
         .stop  = gfs2_sbstats_seq_stop,
         .show  = gfs2_sbstats_seq_show,
 };
 
 #define GFS2_SEQ_GOODSIZE min(PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER, 65536UL)
 
 static int __gfs2_glocks_open(struct inode *inode, struct file *file,
                               const struct seq_operations *ops)
 {
         int ret = seq_open_private(file, ops, sizeof(struct gfs2_glock_iter));
         if (ret == 0) {
                 struct seq_file *seq = file->private_data;
                 struct gfs2_glock_iter *gi = seq->private;
 
                 gi->sdp = inode->i_private;
                 seq->buf = kmalloc(GFS2_SEQ_GOODSIZE, GFP_KERNEL | __GFP_NOWARN);
                 if (seq->buf)
                         seq->size = GFS2_SEQ_GOODSIZE;
                 /*
                  * Initially, we are "before" the first hash table entry; the
                  * first call to rhashtable_walk_next gets us the first entry.
                  */
                 gi->last_pos = -1;
                 gi->gl = NULL;
                 rhashtable_walk_enter(&gl_hash_table, &gi->hti);
         }
         return ret;
 }
 
 static int gfs2_glocks_open(struct inode *inode, struct file *file)
 {
         return __gfs2_glocks_open(inode, file, &gfs2_glock_seq_ops);
 }
 
 static int gfs2_glocks_release(struct inode *inode, struct file *file)
 {
         struct seq_file *seq = file->private_data;
         struct gfs2_glock_iter *gi = seq->private;
 
         if (gi->gl)
                 gfs2_glock_put(gi->gl);
         rhashtable_walk_exit(&gi->hti);
         return seq_release_private(inode, file);
 }
 
 static int gfs2_glstats_open(struct inode *inode, struct file *file)
 {
         return __gfs2_glocks_open(inode, file, &gfs2_glstats_seq_ops);
 }
 
 static const struct file_operations gfs2_glocks_fops = {
         .owner   = THIS_MODULE,
         .open    = gfs2_glocks_open,
         .read    = seq_read,
         .llseek  = seq_lseek,
         .release = gfs2_glocks_release,
 };
 
 static const struct file_operations gfs2_glstats_fops = {
         .owner   = THIS_MODULE,
         .open    = gfs2_glstats_open,
         .read    = seq_read,
         .llseek  = seq_lseek,
         .release = gfs2_glocks_release,
 };
 
 struct gfs2_glockfd_iter {
         struct super_block *sb;
         unsigned int tgid;
         struct task_struct *task;
         unsigned int fd;
         struct file *file;
 };
 
 static struct task_struct *gfs2_glockfd_next_task(struct gfs2_glockfd_iter *i)
 {
         struct pid_namespace *ns = task_active_pid_ns(current);
         struct pid *pid;
 
         if (i->task)
                 put_task_struct(i->task);
 
         rcu_read_lock();
 retry:
         i->task = NULL;
         pid = find_ge_pid(i->tgid, ns);
         if (pid) {
                 i->tgid = pid_nr_ns(pid, ns);
                 i->task = pid_task(pid, PIDTYPE_TGID);
                 if (!i->task) {
                         i->tgid++;
                         goto retry;
                 }
                 get_task_struct(i->task);
         }
         rcu_read_unlock();
         return i->task;
 }
 
 static struct file *gfs2_glockfd_next_file(struct gfs2_glockfd_iter *i)
 {
         if (i->file) {
                 fput(i->file);
                 i->file = NULL;
         }
 
         rcu_read_lock();
         for(;; i->fd++) {
                 struct inode *inode;
 
                 i->file = task_lookup_next_fdget_rcu(i->task, &i->fd);
                 if (!i->file) {
                         i->fd = 0;
                         break;
                 }
 
                 inode = file_inode(i->file);
                 if (inode->i_sb == i->sb)
                         break;
 
                 rcu_read_unlock();
                 fput(i->file);
                 rcu_read_lock();
         }
         rcu_read_unlock();
         return i->file;
 }
 
 static void *gfs2_glockfd_seq_start(struct seq_file *seq, loff_t *pos)
 {
         struct gfs2_glockfd_iter *i = seq->private;
 
         if (*pos)
                 return NULL;
         while (gfs2_glockfd_next_task(i)) {
                 if (gfs2_glockfd_next_file(i))
                         return i;
                 i->tgid++;
         }
         return NULL;
 }
 
 static void *gfs2_glockfd_seq_next(struct seq_file *seq, void *iter_ptr,
                                    loff_t *pos)
 {
         struct gfs2_glockfd_iter *i = seq->private;
 
         (*pos)++;
         i->fd++;
         do {
                 if (gfs2_glockfd_next_file(i))
                         return i;
                 i->tgid++;
         } while (gfs2_glockfd_next_task(i));
         return NULL;
 }
 
 static void gfs2_glockfd_seq_stop(struct seq_file *seq, void *iter_ptr)
 {
         struct gfs2_glockfd_iter *i = seq->private;
 
         if (i->file)
                 fput(i->file);
         if (i->task)
                 put_task_struct(i->task);
 }
 
 static void gfs2_glockfd_seq_show_flock(struct seq_file *seq,
                                         struct gfs2_glockfd_iter *i)
 {
         struct gfs2_file *fp = i->file->private_data;
         struct gfs2_holder *fl_gh = &fp->f_fl_gh;
         struct lm_lockname gl_name = { .ln_type = LM_TYPE_RESERVED };
 
         if (!READ_ONCE(fl_gh->gh_gl))
                 return;
 
         spin_lock(&i->file->f_lock);
         if (gfs2_holder_initialized(fl_gh))
                 gl_name = fl_gh->gh_gl->gl_name;
         spin_unlock(&i->file->f_lock);
 
         if (gl_name.ln_type != LM_TYPE_RESERVED) {
                 seq_printf(seq, "%d %u %u/%llx\n",
                            i->tgid, i->fd, gl_name.ln_type,
                            (unsigned long long)gl_name.ln_number);
         }
 }
 
 static int gfs2_glockfd_seq_show(struct seq_file *seq, void *iter_ptr)
 {
         struct gfs2_glockfd_iter *i = seq->private;
         struct inode *inode = file_inode(i->file);
         struct gfs2_glock *gl;
 
         inode_lock_shared(inode);
         gl = GFS2_I(inode)->i_iopen_gh.gh_gl;
         if (gl) {
                 seq_printf(seq, "%d %u %u/%llx\n",
                            i->tgid, i->fd, gl->gl_name.ln_type,
                            (unsigned long long)gl->gl_name.ln_number);
         }
         gfs2_glockfd_seq_show_flock(seq, i);
         inode_unlock_shared(inode);
         return 0;
 }
 
 static const struct seq_operations gfs2_glockfd_seq_ops = {
         .start = gfs2_glockfd_seq_start,
         .next  = gfs2_glockfd_seq_next,
         .stop  = gfs2_glockfd_seq_stop,
         .show  = gfs2_glockfd_seq_show,
 };
 
 static int gfs2_glockfd_open(struct inode *inode, struct file *file)
 {
         struct gfs2_glockfd_iter *i;
         struct gfs2_sbd *sdp = inode->i_private;
 
         i = __seq_open_private(file, &gfs2_glockfd_seq_ops,
                                sizeof(struct gfs2_glockfd_iter));
         if (!i)
                 return -ENOMEM;
         i->sb = sdp->sd_vfs;
         return 0;
 }
 
 static const struct file_operations gfs2_glockfd_fops = {
         .owner   = THIS_MODULE,
         .open    = gfs2_glockfd_open,
         .read    = seq_read,
         .llseek  = seq_lseek,
         .release = seq_release_private,
 };
 
 DEFINE_SEQ_ATTRIBUTE(gfs2_sbstats);
 
 void gfs2_create_debugfs_file(struct gfs2_sbd *sdp)
 {
         sdp->debugfs_dir = debugfs_create_dir(sdp->sd_table_name, gfs2_root);
 
         debugfs_create_file("glocks", S_IFREG | S_IRUGO, sdp->debugfs_dir, sdp,
                             &gfs2_glocks_fops);
 
         debugfs_create_file("glockfd", S_IFREG | S_IRUGO, sdp->debugfs_dir, sdp,
                             &gfs2_glockfd_fops);
 
         debugfs_create_file("glstats", S_IFREG | S_IRUGO, sdp->debugfs_dir, sdp,
                             &gfs2_glstats_fops);
 
         debugfs_create_file("sbstats", S_IFREG | S_IRUGO, sdp->debugfs_dir, sdp,
                             &gfs2_sbstats_fops);
 }
 
 void gfs2_delete_debugfs_file(struct gfs2_sbd *sdp)
 {
         debugfs_remove_recursive(sdp->debugfs_dir);
         sdp->debugfs_dir = NULL;
 }
 
 void gfs2_register_debugfs(void)
 {
         gfs2_root = debugfs_create_dir("gfs2", NULL);
 }
 
 void gfs2_unregister_debugfs(void)
 {
         debugfs_remove(gfs2_root);
         gfs2_root = NULL;
 }
 

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