c82ee6d3beaa4 (Thomas Gleixner 2019-05-19 15:51:48 +0200 1) // SPDX-License-Identifier: GPL-2.0-or-later
90586523eb4b3 (Eric Paris 2009-05-21 17:01:20 -0400 2) /*
90586523eb4b3 (Eric Paris 2009-05-21 17:01:20 -0400 3) * Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
90586523eb4b3 (Eric Paris 2009-05-21 17:01:20 -0400 4) */
90586523eb4b3 (Eric Paris 2009-05-21 17:01:20 -0400 5)
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 6) /*
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 7) * Basic idea behind the notification queue: An fsnotify group (like inotify)
b3834be5c42a5 (Adam Buchbinder 2012-09-19 21:48:02 -0400 8) * sends the userspace notification about events asynchronously some time after
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 9) * the event happened. When inotify gets an event it will need to add that
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 10) * event to the group notify queue. Since a single event might need to be on
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 11) * multiple group's notification queues we can't add the event directly to each
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 12) * queue and instead add a small "event_holder" to each queue. This event_holder
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 13) * has a pointer back to the original event. Since the majority of events are
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 14) * going to end up on one, and only one, notification queue we embed one
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 15) * event_holder into each event. This means we have a single allocation instead
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 16) * of always needing two. If the embedded event_holder is already in use by
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 17) * another group a new event_holder (from fsnotify_event_holder_cachep) will be
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 18) * allocated and used.
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 19) */
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 20)
90586523eb4b3 (Eric Paris 2009-05-21 17:01:20 -0400 21) #include <linux/fs.h>
90586523eb4b3 (Eric Paris 2009-05-21 17:01:20 -0400 22) #include <linux/init.h>
90586523eb4b3 (Eric Paris 2009-05-21 17:01:20 -0400 23) #include <linux/kernel.h>
90586523eb4b3 (Eric Paris 2009-05-21 17:01:20 -0400 24) #include <linux/list.h>
47882c6f51e8e (Eric Paris 2009-05-21 17:01:47 -0400 25) #include <linux/module.h>
90586523eb4b3 (Eric Paris 2009-05-21 17:01:20 -0400 26) #include <linux/mount.h>
90586523eb4b3 (Eric Paris 2009-05-21 17:01:20 -0400 27) #include <linux/mutex.h>
90586523eb4b3 (Eric Paris 2009-05-21 17:01:20 -0400 28) #include <linux/namei.h>
90586523eb4b3 (Eric Paris 2009-05-21 17:01:20 -0400 29) #include <linux/path.h>
90586523eb4b3 (Eric Paris 2009-05-21 17:01:20 -0400 30) #include <linux/slab.h>
90586523eb4b3 (Eric Paris 2009-05-21 17:01:20 -0400 31) #include <linux/spinlock.h>
90586523eb4b3 (Eric Paris 2009-05-21 17:01:20 -0400 32)
60063497a95e7 (Arun Sharma 2011-07-26 16:09:06 -0700 33) #include <linux/atomic.h>
90586523eb4b3 (Eric Paris 2009-05-21 17:01:20 -0400 34)
90586523eb4b3 (Eric Paris 2009-05-21 17:01:20 -0400 35) #include <linux/fsnotify_backend.h>
90586523eb4b3 (Eric Paris 2009-05-21 17:01:20 -0400 36) #include "fsnotify.h"
90586523eb4b3 (Eric Paris 2009-05-21 17:01:20 -0400 37)
47882c6f51e8e (Eric Paris 2009-05-21 17:01:47 -0400 38) static atomic_t fsnotify_sync_cookie = ATOMIC_INIT(0);
47882c6f51e8e (Eric Paris 2009-05-21 17:01:47 -0400 39)
47882c6f51e8e (Eric Paris 2009-05-21 17:01:47 -0400 40) /**
47882c6f51e8e (Eric Paris 2009-05-21 17:01:47 -0400 41) * fsnotify_get_cookie - return a unique cookie for use in synchronizing events.
47882c6f51e8e (Eric Paris 2009-05-21 17:01:47 -0400 42) * Called from fsnotify_move, which is inlined into filesystem modules.
47882c6f51e8e (Eric Paris 2009-05-21 17:01:47 -0400 43) */
47882c6f51e8e (Eric Paris 2009-05-21 17:01:47 -0400 44) u32 fsnotify_get_cookie(void)
47882c6f51e8e (Eric Paris 2009-05-21 17:01:47 -0400 45) {
47882c6f51e8e (Eric Paris 2009-05-21 17:01:47 -0400 46) return atomic_inc_return(&fsnotify_sync_cookie);
47882c6f51e8e (Eric Paris 2009-05-21 17:01:47 -0400 47) }
47882c6f51e8e (Eric Paris 2009-05-21 17:01:47 -0400 48) EXPORT_SYMBOL_GPL(fsnotify_get_cookie);
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 49)
7053aee26a354 (Jan Kara 2014-01-21 15:48:14 -0800 50) void fsnotify_destroy_event(struct fsnotify_group *group,
7053aee26a354 (Jan Kara 2014-01-21 15:48:14 -0800 51) struct fsnotify_event *event)
90586523eb4b3 (Eric Paris 2009-05-21 17:01:20 -0400 52) {
7053aee26a354 (Jan Kara 2014-01-21 15:48:14 -0800 53) /* Overflow events are per-group and we don't want to free them */
a0a92d261f292 (Amir Goldstein 2019-01-10 19:04:31 +0200 54) if (!event || event == group->overflow_event)
90586523eb4b3 (Eric Paris 2009-05-21 17:01:20 -0400 55) return;
0b1b86527df4b (Jan Kara 2016-10-07 16:56:58 -0700 56) /*
0b1b86527df4b (Jan Kara 2016-10-07 16:56:58 -0700 57) * If the event is still queued, we have a problem... Do an unreliable
0b1b86527df4b (Jan Kara 2016-10-07 16:56:58 -0700 58) * lockless check first to avoid locking in the common case. The
0b1b86527df4b (Jan Kara 2016-10-07 16:56:58 -0700 59) * locking may be necessary for permission events which got removed
0b1b86527df4b (Jan Kara 2016-10-07 16:56:58 -0700 60) * from the list by a different CPU than the one freeing the event.
0b1b86527df4b (Jan Kara 2016-10-07 16:56:58 -0700 61) */
0b1b86527df4b (Jan Kara 2016-10-07 16:56:58 -0700 62) if (!list_empty(&event->list)) {
0b1b86527df4b (Jan Kara 2016-10-07 16:56:58 -0700 63) spin_lock(&group->notification_lock);
0b1b86527df4b (Jan Kara 2016-10-07 16:56:58 -0700 64) WARN_ON(!list_empty(&event->list));
0b1b86527df4b (Jan Kara 2016-10-07 16:56:58 -0700 65) spin_unlock(&group->notification_lock);
0b1b86527df4b (Jan Kara 2016-10-07 16:56:58 -0700 66) }
7053aee26a354 (Jan Kara 2014-01-21 15:48:14 -0800 67) group->ops->free_event(event);
e4aff117368cf (Eric Paris 2009-05-21 17:01:50 -0400 68) }
e4aff117368cf (Eric Paris 2009-05-21 17:01:50 -0400 69)
90586523eb4b3 (Eric Paris 2009-05-21 17:01:20 -0400 70) /*
94e00d28a680d (Amir Goldstein 2021-03-04 12:48:25 +0200 71) * Try to add an event to the notification queue.
94e00d28a680d (Amir Goldstein 2021-03-04 12:48:25 +0200 72) * The group can later pull this event off the queue to deal with.
94e00d28a680d (Amir Goldstein 2021-03-04 12:48:25 +0200 73) * The group can use the @merge hook to merge the event with a queued event.
94e00d28a680d (Amir Goldstein 2021-03-04 12:48:25 +0200 74) * The group can use the @insert hook to insert the event into hash table.
94e00d28a680d (Amir Goldstein 2021-03-04 12:48:25 +0200 75) * The function returns:
94e00d28a680d (Amir Goldstein 2021-03-04 12:48:25 +0200 76) * 0 if the event was added to a queue
94e00d28a680d (Amir Goldstein 2021-03-04 12:48:25 +0200 77) * 1 if the event was merged with some other queued event
12703dbfeb154 (Jan Kara 2016-09-19 14:44:27 -0700 78) * 2 if the event was not queued - either the queue of events has overflown
94e00d28a680d (Amir Goldstein 2021-03-04 12:48:25 +0200 79) * or the group is shutting down.
90586523eb4b3 (Eric Paris 2009-05-21 17:01:20 -0400 80) */
8ba8fa9170935 (Jan Kara 2014-08-06 16:03:26 -0700 81) int fsnotify_add_event(struct fsnotify_group *group,
8ba8fa9170935 (Jan Kara 2014-08-06 16:03:26 -0700 82) struct fsnotify_event *event,
94e00d28a680d (Amir Goldstein 2021-03-04 12:48:25 +0200 83) int (*merge)(struct fsnotify_group *,
94e00d28a680d (Amir Goldstein 2021-03-04 12:48:25 +0200 84) struct fsnotify_event *),
94e00d28a680d (Amir Goldstein 2021-03-04 12:48:25 +0200 85) void (*insert)(struct fsnotify_group *,
94e00d28a680d (Amir Goldstein 2021-03-04 12:48:25 +0200 86) struct fsnotify_event *))
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 87) {
83c0e1b442b48 (Jan Kara 2014-01-28 18:53:22 +0100 88) int ret = 0;
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 89) struct list_head *list = &group->notification_list;
e4aff117368cf (Eric Paris 2009-05-21 17:01:50 -0400 90)
7053aee26a354 (Jan Kara 2014-01-21 15:48:14 -0800 91) pr_debug("%s: group=%p event=%p\n", __func__, group, event);
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 92)
c21dbe20f6062 (Jan Kara 2016-10-07 16:56:52 -0700 93) spin_lock(&group->notification_lock);
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 94)
12703dbfeb154 (Jan Kara 2016-09-19 14:44:27 -0700 95) if (group->shutdown) {
c21dbe20f6062 (Jan Kara 2016-10-07 16:56:52 -0700 96) spin_unlock(&group->notification_lock);
12703dbfeb154 (Jan Kara 2016-09-19 14:44:27 -0700 97) return 2;
12703dbfeb154 (Jan Kara 2016-09-19 14:44:27 -0700 98) }
12703dbfeb154 (Jan Kara 2016-09-19 14:44:27 -0700 99)
7b1f641776e0c (Jan Kara 2018-02-21 15:07:52 +0100 100) if (event == group->overflow_event ||
7b1f641776e0c (Jan Kara 2018-02-21 15:07:52 +0100 101) group->q_len >= group->max_events) {
482ef06c5e946 (Jan Kara 2014-02-21 19:07:54 +0100 102) ret = 2;
7053aee26a354 (Jan Kara 2014-01-21 15:48:14 -0800 103) /* Queue overflow event only if it isn't already queued */
ff57cd5863cf3 (Jan Kara 2014-02-21 19:14:11 +0100 104) if (!list_empty(&group->overflow_event->list)) {
c21dbe20f6062 (Jan Kara 2016-10-07 16:56:52 -0700 105) spin_unlock(&group->notification_lock);
482ef06c5e946 (Jan Kara 2014-02-21 19:07:54 +0100 106) return ret;
482ef06c5e946 (Jan Kara 2014-02-21 19:07:54 +0100 107) }
ff57cd5863cf3 (Jan Kara 2014-02-21 19:14:11 +0100 108) event = group->overflow_event;
482ef06c5e946 (Jan Kara 2014-02-21 19:07:54 +0100 109) goto queue;
e4aff117368cf (Eric Paris 2009-05-21 17:01:50 -0400 110) }
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 111)
74766bbfa99ad (Eric Paris 2009-12-17 21:24:21 -0500 112) if (!list_empty(list) && merge) {
94e00d28a680d (Amir Goldstein 2021-03-04 12:48:25 +0200 113) ret = merge(group, event);
83c0e1b442b48 (Jan Kara 2014-01-28 18:53:22 +0100 114) if (ret) {
c21dbe20f6062 (Jan Kara 2016-10-07 16:56:52 -0700 115) spin_unlock(&group->notification_lock);
83c0e1b442b48 (Jan Kara 2014-01-28 18:53:22 +0100 116) return ret;
f70ab54cc6c39 (Eric Paris 2010-07-28 10:18:37 -0400 117) }
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 118) }
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 119)
482ef06c5e946 (Jan Kara 2014-02-21 19:07:54 +0100 120) queue:
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 121) group->q_len++;
7053aee26a354 (Jan Kara 2014-01-21 15:48:14 -0800 122) list_add_tail(&event->list, list);
94e00d28a680d (Amir Goldstein 2021-03-04 12:48:25 +0200 123) if (insert)
94e00d28a680d (Amir Goldstein 2021-03-04 12:48:25 +0200 124) insert(group, event);
c21dbe20f6062 (Jan Kara 2016-10-07 16:56:52 -0700 125) spin_unlock(&group->notification_lock);
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 126)
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 127) wake_up(&group->notification_waitq);
0a6b6bd5919a6 (Eric Paris 2011-10-14 17:43:39 -0400 128) kill_fasync(&group->fsn_fa, SIGIO, POLL_IN);
83c0e1b442b48 (Jan Kara 2014-01-28 18:53:22 +0100 129) return ret;
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 130) }
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 131)
f7db89accc9c5 (Jan Kara 2019-01-09 13:15:23 +0100 132) void fsnotify_remove_queued_event(struct fsnotify_group *group,
f7db89accc9c5 (Jan Kara 2019-01-09 13:15:23 +0100 133) struct fsnotify_event *event)
f7db89accc9c5 (Jan Kara 2019-01-09 13:15:23 +0100 134) {
f7db89accc9c5 (Jan Kara 2019-01-09 13:15:23 +0100 135) assert_spin_locked(&group->notification_lock);
f7db89accc9c5 (Jan Kara 2019-01-09 13:15:23 +0100 136) /*
f7db89accc9c5 (Jan Kara 2019-01-09 13:15:23 +0100 137) * We need to init list head for the case of overflow event so that
f7db89accc9c5 (Jan Kara 2019-01-09 13:15:23 +0100 138) * check in fsnotify_add_event() works
f7db89accc9c5 (Jan Kara 2019-01-09 13:15:23 +0100 139) */
f7db89accc9c5 (Jan Kara 2019-01-09 13:15:23 +0100 140) list_del_init(&event->list);
f7db89accc9c5 (Jan Kara 2019-01-09 13:15:23 +0100 141) group->q_len--;
f7db89accc9c5 (Jan Kara 2019-01-09 13:15:23 +0100 142) }
f7db89accc9c5 (Jan Kara 2019-01-09 13:15:23 +0100 143)
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 144) /*
6f73171e19236 (Amir Goldstein 2021-03-04 12:48:22 +0200 145) * Return the first event on the notification list without removing it.
6f73171e19236 (Amir Goldstein 2021-03-04 12:48:22 +0200 146) * Returns NULL if the list is empty.
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 147) */
6f73171e19236 (Amir Goldstein 2021-03-04 12:48:22 +0200 148) struct fsnotify_event *fsnotify_peek_first_event(struct fsnotify_group *group)
90586523eb4b3 (Eric Paris 2009-05-21 17:01:20 -0400 149) {
ed2726406c6a7 (Jan Kara 2016-10-07 16:57:01 -0700 150) assert_spin_locked(&group->notification_lock);
90586523eb4b3 (Eric Paris 2009-05-21 17:01:20 -0400 151)
6f73171e19236 (Amir Goldstein 2021-03-04 12:48:22 +0200 152) if (fsnotify_notify_queue_is_empty(group))
6f73171e19236 (Amir Goldstein 2021-03-04 12:48:22 +0200 153) return NULL;
5ba08e2eeb063 (Eric Paris 2010-07-28 10:18:37 -0400 154)
6f73171e19236 (Amir Goldstein 2021-03-04 12:48:22 +0200 155) return list_first_entry(&group->notification_list,
6f73171e19236 (Amir Goldstein 2021-03-04 12:48:22 +0200 156) struct fsnotify_event, list);
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 157) }
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 158)
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 159) /*
6f73171e19236 (Amir Goldstein 2021-03-04 12:48:22 +0200 160) * Remove and return the first event from the notification list. It is the
6f73171e19236 (Amir Goldstein 2021-03-04 12:48:22 +0200 161) * responsibility of the caller to destroy the obtained event
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 162) */
6f73171e19236 (Amir Goldstein 2021-03-04 12:48:22 +0200 163) struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group)
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 164) {
6f73171e19236 (Amir Goldstein 2021-03-04 12:48:22 +0200 165) struct fsnotify_event *event = fsnotify_peek_first_event(group);
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 166)
6f73171e19236 (Amir Goldstein 2021-03-04 12:48:22 +0200 167) if (!event)
6f73171e19236 (Amir Goldstein 2021-03-04 12:48:22 +0200 168) return NULL;
6f73171e19236 (Amir Goldstein 2021-03-04 12:48:22 +0200 169)
6f73171e19236 (Amir Goldstein 2021-03-04 12:48:22 +0200 170) pr_debug("%s: group=%p event=%p\n", __func__, group, event);
6f73171e19236 (Amir Goldstein 2021-03-04 12:48:22 +0200 171)
6f73171e19236 (Amir Goldstein 2021-03-04 12:48:22 +0200 172) fsnotify_remove_queued_event(group, event);
6f73171e19236 (Amir Goldstein 2021-03-04 12:48:22 +0200 173)
6f73171e19236 (Amir Goldstein 2021-03-04 12:48:22 +0200 174) return event;
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 175) }
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 176)
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 177) /*
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 178) * Called when a group is being torn down to clean up any outstanding
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 179) * event notifications.
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 180) */
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 181) void fsnotify_flush_notify(struct fsnotify_group *group)
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 182) {
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 183) struct fsnotify_event *event;
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 184)
c21dbe20f6062 (Jan Kara 2016-10-07 16:56:52 -0700 185) spin_lock(&group->notification_lock);
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 186) while (!fsnotify_notify_queue_is_empty(group)) {
8ba8fa9170935 (Jan Kara 2014-08-06 16:03:26 -0700 187) event = fsnotify_remove_first_event(group);
c21dbe20f6062 (Jan Kara 2016-10-07 16:56:52 -0700 188) spin_unlock(&group->notification_lock);
7053aee26a354 (Jan Kara 2014-01-21 15:48:14 -0800 189) fsnotify_destroy_event(group, event);
c21dbe20f6062 (Jan Kara 2016-10-07 16:56:52 -0700 190) spin_lock(&group->notification_lock);
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 191) }
c21dbe20f6062 (Jan Kara 2016-10-07 16:56:52 -0700 192) spin_unlock(&group->notification_lock);
a2d8bc6cb4a30 (Eric Paris 2009-05-21 17:01:37 -0400 193) }
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