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 /* 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[]; 36 }; 37 38 struct watch_queue { 39 struct rcu_head rcu; 40 struct watch_filter __rcu *filter; 41 struct pipe_inode_info *pipe; /* The pipe we're using as a buffer */ 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 bool defunct; /* T when queues closed */ 50 }; 51 52 /* 53 * Representation of a watch on an object. 54 */ 55 struct watch { 56 union { 57 struct rcu_head rcu; 58 u32 info_id; /* ID to be OR'd in to info field */ 59 }; 60 struct watch_queue __rcu *queue; /* Queue to post events to */ 61 struct hlist_node queue_node; /* Link in queue->watches */ 62 struct watch_list __rcu *watch_list; 63 struct hlist_node list_node; /* Link in watch_list->watchers */ 64 const struct cred *cred; /* Creds of the owner of the watch */ 65 void *private; /* Private data for the watched object */ 66 u64 id; /* Internal identifier */ 67 struct kref usage; /* Object usage count */ 68 }; 69 70 /* 71 * List of watches on an object. 72 */ 73 struct watch_list { 74 struct rcu_head rcu; 75 struct hlist_head watchers; 76 void (*release_watch)(struct watch *); 77 spinlock_t lock; 78 }; 79 80 extern void __post_watch_notification(struct watch_list *, 81 struct watch_notification *, 82 const struct cred *, 83 u64); 84 extern struct watch_queue *get_watch_queue(int); 85 extern void put_watch_queue(struct watch_queue *); 86 extern void init_watch(struct watch *, struct watch_queue *); 87 extern int add_watch_to_object(struct watch *, struct watch_list *); 88 extern int remove_watch_from_object(struct watch_list *, struct watch_queue *, u64, bool); 89 extern long watch_queue_set_size(struct pipe_inode_info *, unsigned int); 90 extern long watch_queue_set_filter(struct pipe_inode_info *, 91 struct watch_notification_filter __user *); 92 extern int watch_queue_init(struct pipe_inode_info *); 93 extern void watch_queue_clear(struct watch_queue *); 94 95 static inline void init_watch_list(struct watch_list *wlist, 96 void (*release_watch)(struct watch *)) 97 { 98 INIT_HLIST_HEAD(&wlist->watchers); 99 spin_lock_init(&wlist->lock); 100 wlist->release_watch = release_watch; 101 } 102 103 static inline void post_watch_notification(struct watch_list *wlist, 104 struct watch_notification *n, 105 const struct cred *cred, 106 u64 id) 107 { 108 if (unlikely(wlist)) 109 __post_watch_notification(wlist, n, cred, id); 110 } 111 112 static inline void remove_watch_list(struct watch_list *wlist, u64 id) 113 { 114 if (wlist) { 115 remove_watch_from_object(wlist, NULL, id, true); 116 kfree_rcu(wlist, rcu); 117 } 118 } 119 120 /** 121 * watch_sizeof - Calculate the information part of the size of a watch record, 122 * given the structure size. 123 */ 124 #define watch_sizeof(STRUCT) (sizeof(STRUCT) << WATCH_INFO_LENGTH__SHIFT) 125 126 #else 127 static inline int watch_queue_init(struct pipe_inode_info *pipe) 128 { 129 return -ENOPKG; 130 } 131 132 #endif 133 134 #endif /* _LINUX_WATCH_QUEUE_H */ 135