mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-23 17:30:02 +00:00
![Linus Torvalds](/assets/img/avatar_default.png)
This reverts commit3bcf3860a4
(and the accompanying commitc1e5c95402
"vfs/fsnotify: fsnotify_close can delay the final work in fput" that was a horribly ugly hack to make it work at all). The 'struct file' approach not only causes that disgusting hack, it somehow breaks pulseaudio, probably due to some other subtlety with f_count handling. Fix up various conflicts due to later fsnotify work. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
464 lines
13 KiB
C
464 lines
13 KiB
C
/*
|
|
* Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License as published by
|
|
* the Free Software Foundation; either version 2, or (at your option)
|
|
* any later version.
|
|
*
|
|
* This program is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
* GNU General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU General Public License
|
|
* along with this program; see the file COPYING. If not, write to
|
|
* the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
|
|
*/
|
|
|
|
/*
|
|
* Basic idea behind the notification queue: An fsnotify group (like inotify)
|
|
* sends the userspace notification about events asyncronously 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 <asm/atomic.h>
|
|
|
|
#include <linux/fsnotify_backend.h>
|
|
#include "fsnotify.h"
|
|
|
|
static struct kmem_cache *fsnotify_event_cachep;
|
|
static struct kmem_cache *fsnotify_event_holder_cachep;
|
|
/*
|
|
* This is a magic event we send when the q is too full. Since it doesn't
|
|
* hold real event information we just keep one system wide and use it any time
|
|
* it is needed. It's refcnt is set 1 at kernel init time and will never
|
|
* get set to 0 so it will never get 'freed'
|
|
*/
|
|
static struct fsnotify_event *q_overflow_event;
|
|
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);
|
|
|
|
/* return true if the notify queue is empty, false otherwise */
|
|
bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group)
|
|
{
|
|
BUG_ON(!mutex_is_locked(&group->notification_mutex));
|
|
return list_empty(&group->notification_list) ? true : false;
|
|
}
|
|
|
|
void fsnotify_get_event(struct fsnotify_event *event)
|
|
{
|
|
atomic_inc(&event->refcnt);
|
|
}
|
|
|
|
void fsnotify_put_event(struct fsnotify_event *event)
|
|
{
|
|
if (!event)
|
|
return;
|
|
|
|
if (atomic_dec_and_test(&event->refcnt)) {
|
|
pr_debug("%s: event=%p\n", __func__, event);
|
|
|
|
if (event->data_type == FSNOTIFY_EVENT_PATH)
|
|
path_put(&event->path);
|
|
|
|
BUG_ON(!list_empty(&event->private_data_list));
|
|
|
|
kfree(event->file_name);
|
|
put_pid(event->tgid);
|
|
kmem_cache_free(fsnotify_event_cachep, event);
|
|
}
|
|
}
|
|
|
|
struct fsnotify_event_holder *fsnotify_alloc_event_holder(void)
|
|
{
|
|
return kmem_cache_alloc(fsnotify_event_holder_cachep, GFP_KERNEL);
|
|
}
|
|
|
|
void fsnotify_destroy_event_holder(struct fsnotify_event_holder *holder)
|
|
{
|
|
if (holder)
|
|
kmem_cache_free(fsnotify_event_holder_cachep, holder);
|
|
}
|
|
|
|
/*
|
|
* Find the private data that the group previously attached to this event when
|
|
* the group added the event to the notification queue (fsnotify_add_notify_event)
|
|
*/
|
|
struct fsnotify_event_private_data *fsnotify_remove_priv_from_event(struct fsnotify_group *group, struct fsnotify_event *event)
|
|
{
|
|
struct fsnotify_event_private_data *lpriv;
|
|
struct fsnotify_event_private_data *priv = NULL;
|
|
|
|
assert_spin_locked(&event->lock);
|
|
|
|
list_for_each_entry(lpriv, &event->private_data_list, event_list) {
|
|
if (lpriv->group == group) {
|
|
priv = lpriv;
|
|
list_del(&priv->event_list);
|
|
break;
|
|
}
|
|
}
|
|
return priv;
|
|
}
|
|
|
|
/*
|
|
* Add an event to the group notification queue. The group can later pull this
|
|
* event off the queue to deal with. If the event is successfully added to the
|
|
* group's notification queue, a reference is taken on event.
|
|
*/
|
|
struct fsnotify_event *fsnotify_add_notify_event(struct fsnotify_group *group, struct fsnotify_event *event,
|
|
struct fsnotify_event_private_data *priv,
|
|
struct fsnotify_event *(*merge)(struct list_head *,
|
|
struct fsnotify_event *))
|
|
{
|
|
struct fsnotify_event *return_event = NULL;
|
|
struct fsnotify_event_holder *holder = NULL;
|
|
struct list_head *list = &group->notification_list;
|
|
|
|
pr_debug("%s: group=%p event=%p priv=%p\n", __func__, group, event, priv);
|
|
|
|
/*
|
|
* There is one fsnotify_event_holder embedded inside each fsnotify_event.
|
|
* Check if we expect to be able to use that holder. If not alloc a new
|
|
* holder.
|
|
* For the overflow event it's possible that something will use the in
|
|
* event holder before we get the lock so we may need to jump back and
|
|
* alloc a new holder, this can't happen for most events...
|
|
*/
|
|
if (!list_empty(&event->holder.event_list)) {
|
|
alloc_holder:
|
|
holder = fsnotify_alloc_event_holder();
|
|
if (!holder)
|
|
return ERR_PTR(-ENOMEM);
|
|
}
|
|
|
|
mutex_lock(&group->notification_mutex);
|
|
|
|
if (group->q_len >= group->max_events) {
|
|
event = q_overflow_event;
|
|
|
|
/*
|
|
* we need to return the overflow event
|
|
* which means we need a ref
|
|
*/
|
|
fsnotify_get_event(event);
|
|
return_event = event;
|
|
|
|
/* sorry, no private data on the overflow event */
|
|
priv = NULL;
|
|
}
|
|
|
|
if (!list_empty(list) && merge) {
|
|
struct fsnotify_event *tmp;
|
|
|
|
tmp = merge(list, event);
|
|
if (tmp) {
|
|
mutex_unlock(&group->notification_mutex);
|
|
|
|
if (return_event)
|
|
fsnotify_put_event(return_event);
|
|
if (holder != &event->holder)
|
|
fsnotify_destroy_event_holder(holder);
|
|
return tmp;
|
|
}
|
|
}
|
|
|
|
spin_lock(&event->lock);
|
|
|
|
if (list_empty(&event->holder.event_list)) {
|
|
if (unlikely(holder))
|
|
fsnotify_destroy_event_holder(holder);
|
|
holder = &event->holder;
|
|
} else if (unlikely(!holder)) {
|
|
/* between the time we checked above and got the lock the in
|
|
* event holder was used, go back and get a new one */
|
|
spin_unlock(&event->lock);
|
|
mutex_unlock(&group->notification_mutex);
|
|
|
|
if (return_event) {
|
|
fsnotify_put_event(return_event);
|
|
return_event = NULL;
|
|
}
|
|
|
|
goto alloc_holder;
|
|
}
|
|
|
|
group->q_len++;
|
|
holder->event = event;
|
|
|
|
fsnotify_get_event(event);
|
|
list_add_tail(&holder->event_list, list);
|
|
if (priv)
|
|
list_add_tail(&priv->event_list, &event->private_data_list);
|
|
spin_unlock(&event->lock);
|
|
mutex_unlock(&group->notification_mutex);
|
|
|
|
wake_up(&group->notification_waitq);
|
|
return return_event;
|
|
}
|
|
|
|
/*
|
|
* Remove and return the first event from the notification list. There is a
|
|
* reference held on this event since it was on the list. It is the responsibility
|
|
* of the caller to drop this reference.
|
|
*/
|
|
struct fsnotify_event *fsnotify_remove_notify_event(struct fsnotify_group *group)
|
|
{
|
|
struct fsnotify_event *event;
|
|
struct fsnotify_event_holder *holder;
|
|
|
|
BUG_ON(!mutex_is_locked(&group->notification_mutex));
|
|
|
|
pr_debug("%s: group=%p\n", __func__, group);
|
|
|
|
holder = list_first_entry(&group->notification_list, struct fsnotify_event_holder, event_list);
|
|
|
|
event = holder->event;
|
|
|
|
spin_lock(&event->lock);
|
|
holder->event = NULL;
|
|
list_del_init(&holder->event_list);
|
|
spin_unlock(&event->lock);
|
|
|
|
/* event == holder means we are referenced through the in event holder */
|
|
if (holder != &event->holder)
|
|
fsnotify_destroy_event_holder(holder);
|
|
|
|
group->q_len--;
|
|
|
|
return event;
|
|
}
|
|
|
|
/*
|
|
* This will not remove the event, that must be done with fsnotify_remove_notify_event()
|
|
*/
|
|
struct fsnotify_event *fsnotify_peek_notify_event(struct fsnotify_group *group)
|
|
{
|
|
struct fsnotify_event *event;
|
|
struct fsnotify_event_holder *holder;
|
|
|
|
BUG_ON(!mutex_is_locked(&group->notification_mutex));
|
|
|
|
holder = list_first_entry(&group->notification_list, struct fsnotify_event_holder, event_list);
|
|
event = holder->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;
|
|
struct fsnotify_event_private_data *priv;
|
|
|
|
mutex_lock(&group->notification_mutex);
|
|
while (!fsnotify_notify_queue_is_empty(group)) {
|
|
event = fsnotify_remove_notify_event(group);
|
|
/* if they don't implement free_event_priv they better not have attached any */
|
|
if (group->ops->free_event_priv) {
|
|
spin_lock(&event->lock);
|
|
priv = fsnotify_remove_priv_from_event(group, event);
|
|
spin_unlock(&event->lock);
|
|
if (priv)
|
|
group->ops->free_event_priv(priv);
|
|
}
|
|
fsnotify_put_event(event); /* matches fsnotify_add_notify_event */
|
|
}
|
|
mutex_unlock(&group->notification_mutex);
|
|
}
|
|
|
|
static void initialize_event(struct fsnotify_event *event)
|
|
{
|
|
INIT_LIST_HEAD(&event->holder.event_list);
|
|
atomic_set(&event->refcnt, 1);
|
|
|
|
spin_lock_init(&event->lock);
|
|
|
|
INIT_LIST_HEAD(&event->private_data_list);
|
|
}
|
|
|
|
/*
|
|
* Caller damn well better be holding whatever mutex is protecting the
|
|
* old_holder->event_list and the new_event must be a clean event which
|
|
* cannot be found anywhere else in the kernel.
|
|
*/
|
|
int fsnotify_replace_event(struct fsnotify_event_holder *old_holder,
|
|
struct fsnotify_event *new_event)
|
|
{
|
|
struct fsnotify_event *old_event = old_holder->event;
|
|
struct fsnotify_event_holder *new_holder = &new_event->holder;
|
|
|
|
enum event_spinlock_class {
|
|
SPINLOCK_OLD,
|
|
SPINLOCK_NEW,
|
|
};
|
|
|
|
pr_debug("%s: old_event=%p new_event=%p\n", __func__, old_event, new_event);
|
|
|
|
/*
|
|
* if the new_event's embedded holder is in use someone
|
|
* screwed up and didn't give us a clean new event.
|
|
*/
|
|
BUG_ON(!list_empty(&new_holder->event_list));
|
|
|
|
spin_lock_nested(&old_event->lock, SPINLOCK_OLD);
|
|
spin_lock_nested(&new_event->lock, SPINLOCK_NEW);
|
|
|
|
new_holder->event = new_event;
|
|
list_replace_init(&old_holder->event_list, &new_holder->event_list);
|
|
|
|
spin_unlock(&new_event->lock);
|
|
spin_unlock(&old_event->lock);
|
|
|
|
/* event == holder means we are referenced through the in event holder */
|
|
if (old_holder != &old_event->holder)
|
|
fsnotify_destroy_event_holder(old_holder);
|
|
|
|
fsnotify_get_event(new_event); /* on the list take reference */
|
|
fsnotify_put_event(old_event); /* off the list, drop reference */
|
|
|
|
return 0;
|
|
}
|
|
|
|
struct fsnotify_event *fsnotify_clone_event(struct fsnotify_event *old_event)
|
|
{
|
|
struct fsnotify_event *event;
|
|
|
|
event = kmem_cache_alloc(fsnotify_event_cachep, GFP_KERNEL);
|
|
if (!event)
|
|
return NULL;
|
|
|
|
pr_debug("%s: old_event=%p new_event=%p\n", __func__, old_event, event);
|
|
|
|
memcpy(event, old_event, sizeof(*event));
|
|
initialize_event(event);
|
|
|
|
if (event->name_len) {
|
|
event->file_name = kstrdup(old_event->file_name, GFP_KERNEL);
|
|
if (!event->file_name) {
|
|
kmem_cache_free(fsnotify_event_cachep, event);
|
|
return NULL;
|
|
}
|
|
}
|
|
event->tgid = get_pid(old_event->tgid);
|
|
if (event->data_type == FSNOTIFY_EVENT_PATH)
|
|
path_get(&event->path);
|
|
|
|
return event;
|
|
}
|
|
|
|
/*
|
|
* fsnotify_create_event - Allocate a new event which will be sent to each
|
|
* group's handle_event function if the group was interested in this
|
|
* particular event.
|
|
*
|
|
* @to_tell the inode which is supposed to receive the event (sometimes a
|
|
* parent of the inode to which the event happened.
|
|
* @mask what actually happened.
|
|
* @data pointer to the object which was actually affected
|
|
* @data_type flag indication if the data is a file, path, inode, nothing...
|
|
* @name the filename, if available
|
|
*/
|
|
struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask, void *data,
|
|
int data_type, const unsigned char *name,
|
|
u32 cookie, gfp_t gfp)
|
|
{
|
|
struct fsnotify_event *event;
|
|
|
|
event = kmem_cache_zalloc(fsnotify_event_cachep, gfp);
|
|
if (!event)
|
|
return NULL;
|
|
|
|
pr_debug("%s: event=%p to_tell=%p mask=%x data=%p data_type=%d\n",
|
|
__func__, event, to_tell, mask, data, data_type);
|
|
|
|
initialize_event(event);
|
|
|
|
if (name) {
|
|
event->file_name = kstrdup(name, gfp);
|
|
if (!event->file_name) {
|
|
kmem_cache_free(fsnotify_event_cachep, event);
|
|
return NULL;
|
|
}
|
|
event->name_len = strlen(event->file_name);
|
|
}
|
|
|
|
event->tgid = get_pid(task_tgid(current));
|
|
event->sync_cookie = cookie;
|
|
event->to_tell = to_tell;
|
|
event->data_type = data_type;
|
|
|
|
switch (data_type) {
|
|
case FSNOTIFY_EVENT_PATH: {
|
|
struct path *path = data;
|
|
event->path.dentry = path->dentry;
|
|
event->path.mnt = path->mnt;
|
|
path_get(&event->path);
|
|
break;
|
|
}
|
|
case FSNOTIFY_EVENT_INODE:
|
|
event->inode = data;
|
|
break;
|
|
case FSNOTIFY_EVENT_NONE:
|
|
event->inode = NULL;
|
|
event->path.dentry = NULL;
|
|
event->path.mnt = NULL;
|
|
break;
|
|
default:
|
|
BUG();
|
|
}
|
|
|
|
event->mask = mask;
|
|
|
|
return event;
|
|
}
|
|
|
|
__init int fsnotify_notification_init(void)
|
|
{
|
|
fsnotify_event_cachep = KMEM_CACHE(fsnotify_event, SLAB_PANIC);
|
|
fsnotify_event_holder_cachep = KMEM_CACHE(fsnotify_event_holder, SLAB_PANIC);
|
|
|
|
q_overflow_event = fsnotify_create_event(NULL, FS_Q_OVERFLOW, NULL,
|
|
FSNOTIFY_EVENT_NONE, NULL, 0,
|
|
GFP_KERNEL);
|
|
if (!q_overflow_event)
|
|
panic("unable to allocate fsnotify q_overflow_event\n");
|
|
|
|
return 0;
|
|
}
|
|
subsys_initcall(fsnotify_notification_init);
|
|
|