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/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 		unsigned long	type_filter[2];	/* Bitmask of accepted types */
32 	};
33 	u32			nr_filters;	/* Number of filters */
34 	struct watch_type_filter filters[];
35 };
36 
37 struct watch_queue {
38 	struct rcu_head		rcu;
39 	struct watch_filter __rcu *filter;
40 	struct pipe_inode_info	*pipe;		/* The pipe we're using as a buffer */
41 	struct hlist_head	watches;	/* Contributory watches */
42 	struct page		**notes;	/* Preallocated notifications */
43 	unsigned long		*notes_bitmap;	/* Allocation bitmap for notes */
44 	struct kref		usage;		/* Object usage count */
45 	spinlock_t		lock;
46 	unsigned int		nr_notes;	/* Number of notes */
47 	unsigned int		nr_pages;	/* Number of pages in notes[] */
48 	bool			defunct;	/* T when queues closed */
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 
init_watch_list(struct watch_list * wlist,void (* release_watch)(struct watch *))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 
post_watch_notification(struct watch_list * wlist,struct watch_notification * n,const struct cred * cred,u64 id)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 
remove_watch_list(struct watch_list * wlist,u64 id)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
watch_queue_init(struct pipe_inode_info * pipe)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