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
19struct cred;
20
21struct 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
28struct 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
38struct 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 */
54struct 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 */
72struct watch_list {
73 struct rcu_head rcu;
74 struct hlist_head watchers;
75 void (*release_watch)(struct watch *);
76 spinlock_t lock;
77};
78
79extern void __post_watch_notification(struct watch_list *,
80 struct watch_notification *,
81 const struct cred *,
82 u64);
83extern struct watch_queue *get_watch_queue(int);
84extern void put_watch_queue(struct watch_queue *);
85extern void init_watch(struct watch *, struct watch_queue *);
86extern int add_watch_to_object(struct watch *, struct watch_list *);
87extern int remove_watch_from_object(struct watch_list *, struct watch_queue *, u64, bool);
88extern long watch_queue_set_size(struct pipe_inode_info *, unsigned int);
89extern long watch_queue_set_filter(struct pipe_inode_info *,
90 struct watch_notification_filter __user *);
91extern int watch_queue_init(struct pipe_inode_info *);
92extern void watch_queue_clear(struct watch_queue *);
93
94static 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
102static 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
111static 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
126static 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