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(I'm so sorry!) Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel os linux
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194// SPDX-License-Identifier: GPL-2.0-or-later/* * Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com> */
/* * Basic idea behind the notification queue: An fsnotify group (like inotify) * sends the userspace notification about events asynchronously some time after * the event happened. When inotify gets an event it will need to add that * event to the group notify queue. Since a single event might need to be on * multiple group's notification queues we can't add the event directly to each * queue and instead add a small "event_holder" to each queue. This event_holder * has a pointer back to the original event. Since the majority of events are * going to end up on one, and only one, notification queue we embed one * event_holder into each event. This means we have a single allocation instead * of always needing two. If the embedded event_holder is already in use by * another group a new event_holder (from fsnotify_event_holder_cachep) will be * allocated and used. */
#include <linux/fs.h>#include <linux/init.h>#include <linux/kernel.h>#include <linux/list.h>#include <linux/module.h>#include <linux/mount.h>#include <linux/mutex.h>#include <linux/namei.h>#include <linux/path.h>#include <linux/slab.h>#include <linux/spinlock.h>
#include <linux/atomic.h>
#include <linux/fsnotify_backend.h>#include "fsnotify.h"
static atomic_t fsnotify_sync_cookie = ATOMIC_INIT(0);
/** * fsnotify_get_cookie - return a unique cookie for use in synchronizing events. * Called from fsnotify_move, which is inlined into filesystem modules. */u32 fsnotify_get_cookie(void){ return atomic_inc_return(&fsnotify_sync_cookie);}EXPORT_SYMBOL_GPL(fsnotify_get_cookie);
void fsnotify_destroy_event(struct fsnotify_group *group, struct fsnotify_event *event){ /* Overflow events are per-group and we don't want to free them */ if (!event || event == group->overflow_event) return; /* * If the event is still queued, we have a problem... Do an unreliable * lockless check first to avoid locking in the common case. The * locking may be necessary for permission events which got removed * from the list by a different CPU than the one freeing the event. */ if (!list_empty(&event->list)) { spin_lock(&group->notification_lock); WARN_ON(!list_empty(&event->list)); spin_unlock(&group->notification_lock); } group->ops->free_event(group, event);}
/* * Try to add an event to the notification queue. * The group can later pull this event off the queue to deal with. * The group can use the @merge hook to merge the event with a queued event. * The group can use the @insert hook to insert the event into hash table. * The function returns: * 0 if the event was added to a queue * 1 if the event was merged with some other queued event * 2 if the event was not queued - either the queue of events has overflown * or the group is shutting down. */int fsnotify_insert_event(struct fsnotify_group *group, struct fsnotify_event *event, int (*merge)(struct fsnotify_group *, struct fsnotify_event *), void (*insert)(struct fsnotify_group *, struct fsnotify_event *)){ int ret = 0; struct list_head *list = &group->notification_list;
pr_debug("%s: group=%p event=%p\n", __func__, group, event);
spin_lock(&group->notification_lock);
if (group->shutdown) { spin_unlock(&group->notification_lock); return 2; }
if (event == group->overflow_event || group->q_len >= group->max_events) { ret = 2; /* Queue overflow event only if it isn't already queued */ if (!list_empty(&group->overflow_event->list)) { spin_unlock(&group->notification_lock); return ret; } event = group->overflow_event; goto queue; }
if (!list_empty(list) && merge) { ret = merge(group, event); if (ret) { spin_unlock(&group->notification_lock); return ret; } }
queue: group->q_len++; list_add_tail(&event->list, list); if (insert) insert(group, event); spin_unlock(&group->notification_lock);
wake_up(&group->notification_waitq); kill_fasync(&group->fsn_fa, SIGIO, POLL_IN); return ret;}
void fsnotify_remove_queued_event(struct fsnotify_group *group, struct fsnotify_event *event){ assert_spin_locked(&group->notification_lock); /* * We need to init list head for the case of overflow event so that * check in fsnotify_add_event() works */ list_del_init(&event->list); group->q_len--;}
/* * Return the first event on the notification list without removing it. * Returns NULL if the list is empty. */struct fsnotify_event *fsnotify_peek_first_event(struct fsnotify_group *group){ assert_spin_locked(&group->notification_lock);
if (fsnotify_notify_queue_is_empty(group)) return NULL;
return list_first_entry(&group->notification_list, struct fsnotify_event, list);}
/* * Remove and return the first event from the notification list. It is the * responsibility of the caller to destroy the obtained event */struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group){ struct fsnotify_event *event = fsnotify_peek_first_event(group);
if (!event) return NULL;
pr_debug("%s: group=%p event=%p\n", __func__, group, event);
fsnotify_remove_queued_event(group, event);
return event;}
/* * Called when a group is being torn down to clean up any outstanding * event notifications. */void fsnotify_flush_notify(struct fsnotify_group *group){ struct fsnotify_event *event;
spin_lock(&group->notification_lock); while (!fsnotify_notify_queue_is_empty(group)) { event = fsnotify_remove_first_event(group); spin_unlock(&group->notification_lock); fsnotify_destroy_event(group, event); spin_lock(&group->notification_lock); } spin_unlock(&group->notification_lock);}