1 // SPDX-License-Identifier: GPL-2.0
2 /* User-mappable watch queue
3 *
4 * Copyright (C) 2020 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 *
7 * See Documentation/core-api/watch_queue.rst
8 */
9
10 #ifndef _LINUX_WATCH_QUEUE_H
11 #define _LINUX_WATCH_QUEUE_H
12
13 #include <uapi/linux/watch_queue.h>
14 #include <linux/kref.h>
15 #include <linux/rcupdate.h>
16
17 #ifdef CONFIG_WATCH_QUEUE
18
19 struct cred;
20
21 struct watch_type_filter {
22 enum watch_notification_type type;
23 __u32 subtype_filter[1]; /* Bitmask of subtypes to filter on */
24 __u32 info_filter; /* Filter on watch_notification::info */
25 __u32 info_mask; /* Mask of relevant bits in info_filter */
26 };
27
28 struct watch_filter {
29 union {
30 struct rcu_head rcu;
31 /* Bitmask of accepted types */
32 DECLARE_BITMAP(type_filter, WATCH_TYPE__NR);
33 };
34 u32 nr_filters; /* Number of filters */
35 struct watch_type_filter filters[] __counted_by(nr_filters);
36 };
37
38 struct watch_queue {
39 struct rcu_head rcu;
40 struct watch_filter __rcu *filter;
41 struct pipe_inode_info *pipe; /* Pipe we use as a buffer, NULL if queue closed */
42 struct hlist_head watches; /* Contributory watches */
43 struct page **notes; /* Preallocated notifications */
44 unsigned long *notes_bitmap; /* Allocation bitmap for notes */
45 struct kref usage; /* Object usage count */
46 spinlock_t lock;
47 unsigned int nr_notes; /* Number of notes */
48 unsigned int nr_pages; /* Number of pages in notes[] */
49 };
50
51 /*
52 * Representation of a watch on an object.
53 */
54 struct watch {
55 union {
56 struct rcu_head rcu;
57 u32 info_id; /* ID to be OR'd in to info field */
58 };
59 struct watch_queue __rcu *queue; /* Queue to post events to */
60 struct hlist_node queue_node; /* Link in queue->watches */
61 struct watch_list __rcu *watch_list;
62 struct hlist_node list_node; /* Link in watch_list->watchers */
63 const struct cred *cred; /* Creds of the owner of the watch */
64 void *private; /* Private data for the watched object */
65 u64 id; /* Internal identifier */
66 struct kref usage; /* Object usage count */
67 };
68
69 /*
70 * List of watches on an object.
71 */
72 struct watch_list {
73 struct rcu_head rcu;
74 struct hlist_head watchers;
75 void (*release_watch)(struct watch *);
76 spinlock_t lock;
77 };
78
79 extern void __post_watch_notification(struct watch_list *,
80 struct watch_notification *,
81 const struct cred *,
82 u64);
83 extern struct watch_queue *get_watch_queue(int);
84 extern void put_watch_queue(struct watch_queue *);
85 extern void init_watch(struct watch *, struct watch_queue *);
86 extern int add_watch_to_object(struct watch *, struct watch_list *);
87 extern int remove_watch_from_object(struct watch_list *, struct watch_queue *, u64, bool);
88 extern long watch_queue_set_size(struct pipe_inode_info *, unsigned int);
89 extern long watch_queue_set_filter(struct pipe_inode_info *,
90 struct watch_notification_filter __user *);
91 extern int watch_queue_init(struct pipe_inode_info *);
92 extern void watch_queue_clear(struct watch_queue *);
93
94 static inline void init_watch_list(struct watch_list *wlist,
95 void (*release_watch)(struct watch *))
96 {
97 INIT_HLIST_HEAD(&wlist->watchers);
98 spin_lock_init(&wlist->lock);
99 wlist->release_watch = release_watch;
100 }
101
102 static inline void post_watch_notification(struct watch_list *wlist,
103 struct watch_notification *n,
104 const struct cred *cred,
105 u64 id)
106 {
107 if (unlikely(wlist))
108 __post_watch_notification(wlist, n, cred, id);
109 }
110
111 static inline void remove_watch_list(struct watch_list *wlist, u64 id)
112 {
113 if (wlist) {
114 remove_watch_from_object(wlist, NULL, id, true);
115 kfree_rcu(wlist, rcu);
116 }
117 }
118
119 /**
120 * watch_sizeof - Calculate the information part of the size of a watch record,
121 * given the structure size.
122 */
123 #define watch_sizeof(STRUCT) (sizeof(STRUCT) << WATCH_INFO_LENGTH__SHIFT)
124
125 #else
126 static inline int watch_queue_init(struct pipe_inode_info *pipe)
127 {
128 return -ENOPKG;
129 }
130
131 #endif
132
133 #endif /* _LINUX_WATCH_QUEUE_H */
134
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