watch_queue.h

  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 */