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