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 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 } 101 102 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 } 110 111 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 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