mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-12-09 12:04:15 +08:00
8778abb9a8
Instead of moving list elements from destroy_list to &private_destroy_list, exchange the list heads. Signed-off-by: Andreas Gruenbacher <agruen@suse.de> Signed-off-by: Eric Paris <eparis@redhat.com>
381 lines
11 KiB
C
381 lines
11 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.
|
|
*/
|
|
|
|
/*
|
|
* fsnotify inode mark locking/lifetime/and refcnting
|
|
*
|
|
* REFCNT:
|
|
* The mark->refcnt tells how many "things" in the kernel currently are
|
|
* referencing this object. The object typically will live inside the kernel
|
|
* with a refcnt of 2, one for each list it is on (i_list, g_list). Any task
|
|
* which can find this object holding the appropriete locks, can take a reference
|
|
* and the object itself is guarenteed to survive until the reference is dropped.
|
|
*
|
|
* LOCKING:
|
|
* There are 3 spinlocks involved with fsnotify inode marks and they MUST
|
|
* be taken in order as follows:
|
|
*
|
|
* mark->lock
|
|
* group->mark_lock
|
|
* inode->i_lock
|
|
*
|
|
* mark->lock protects 2 things, mark->group and mark->inode. You must hold
|
|
* that lock to dereference either of these things (they could be NULL even with
|
|
* the lock)
|
|
*
|
|
* group->mark_lock protects the marks_list anchored inside a given group
|
|
* and each mark is hooked via the g_list. It also sorta protects the
|
|
* free_g_list, which when used is anchored by a private list on the stack of the
|
|
* task which held the group->mark_lock.
|
|
*
|
|
* inode->i_lock protects the i_fsnotify_marks list anchored inside a
|
|
* given inode and each mark is hooked via the i_list. (and sorta the
|
|
* free_i_list)
|
|
*
|
|
*
|
|
* LIFETIME:
|
|
* Inode marks survive between when they are added to an inode and when their
|
|
* refcnt==0.
|
|
*
|
|
* The inode mark can be cleared for a number of different reasons including:
|
|
* - The inode is unlinked for the last time. (fsnotify_inode_remove)
|
|
* - The inode is being evicted from cache. (fsnotify_inode_delete)
|
|
* - The fs the inode is on is unmounted. (fsnotify_inode_delete/fsnotify_unmount_inodes)
|
|
* - Something explicitly requests that it be removed. (fsnotify_destroy_mark)
|
|
* - The fsnotify_group associated with the mark is going away and all such marks
|
|
* need to be cleaned up. (fsnotify_clear_marks_by_group)
|
|
*
|
|
* Worst case we are given an inode and need to clean up all the marks on that
|
|
* inode. We take i_lock and walk the i_fsnotify_marks safely. For each
|
|
* mark on the list we take a reference (so the mark can't disappear under us).
|
|
* We remove that mark form the inode's list of marks and we add this mark to a
|
|
* private list anchored on the stack using i_free_list; At this point we no
|
|
* longer fear anything finding the mark using the inode's list of marks.
|
|
*
|
|
* We can safely and locklessly run the private list on the stack of everything
|
|
* we just unattached from the original inode. For each mark on the private list
|
|
* we grab the mark-> and can thus dereference mark->group and mark->inode. If
|
|
* we see the group and inode are not NULL we take those locks. Now holding all
|
|
* 3 locks we can completely remove the mark from other tasks finding it in the
|
|
* future. Remember, 10 things might already be referencing this mark, but they
|
|
* better be holding a ref. We drop our reference we took before we unhooked it
|
|
* from the inode. When the ref hits 0 we can free the mark.
|
|
*
|
|
* Very similarly for freeing by group, except we use free_g_list.
|
|
*
|
|
* This has the very interesting property of being able to run concurrently with
|
|
* any (or all) other directions.
|
|
*/
|
|
|
|
#include <linux/fs.h>
|
|
#include <linux/init.h>
|
|
#include <linux/kernel.h>
|
|
#include <linux/kthread.h>
|
|
#include <linux/module.h>
|
|
#include <linux/mutex.h>
|
|
#include <linux/slab.h>
|
|
#include <linux/spinlock.h>
|
|
#include <linux/srcu.h>
|
|
#include <linux/writeback.h> /* for inode_lock */
|
|
|
|
#include <asm/atomic.h>
|
|
|
|
#include <linux/fsnotify_backend.h>
|
|
#include "fsnotify.h"
|
|
|
|
struct srcu_struct fsnotify_mark_srcu;
|
|
static DEFINE_SPINLOCK(destroy_lock);
|
|
static LIST_HEAD(destroy_list);
|
|
static DECLARE_WAIT_QUEUE_HEAD(destroy_waitq);
|
|
|
|
void fsnotify_get_mark(struct fsnotify_mark *mark)
|
|
{
|
|
atomic_inc(&mark->refcnt);
|
|
}
|
|
|
|
void fsnotify_put_mark(struct fsnotify_mark *mark)
|
|
{
|
|
if (atomic_dec_and_test(&mark->refcnt))
|
|
mark->free_mark(mark);
|
|
}
|
|
|
|
/*
|
|
* Any time a mark is getting freed we end up here.
|
|
* The caller had better be holding a reference to this mark so we don't actually
|
|
* do the final put under the mark->lock
|
|
*/
|
|
void fsnotify_destroy_mark(struct fsnotify_mark *mark)
|
|
{
|
|
struct fsnotify_group *group;
|
|
struct inode *inode = NULL;
|
|
|
|
spin_lock(&mark->lock);
|
|
|
|
group = mark->group;
|
|
|
|
/* something else already called this function on this mark */
|
|
if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) {
|
|
spin_unlock(&mark->lock);
|
|
return;
|
|
}
|
|
|
|
mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
|
|
|
|
/* 1 from caller and 1 for being on i_list/g_list */
|
|
BUG_ON(atomic_read(&mark->refcnt) < 2);
|
|
|
|
spin_lock(&group->mark_lock);
|
|
|
|
if (mark->flags & FSNOTIFY_MARK_FLAG_INODE) {
|
|
inode = mark->i.inode;
|
|
fsnotify_destroy_inode_mark(mark);
|
|
} else if (mark->flags & FSNOTIFY_MARK_FLAG_VFSMOUNT)
|
|
fsnotify_destroy_vfsmount_mark(mark);
|
|
else
|
|
BUG();
|
|
|
|
list_del_init(&mark->g_list);
|
|
|
|
spin_unlock(&group->mark_lock);
|
|
spin_unlock(&mark->lock);
|
|
|
|
spin_lock(&destroy_lock);
|
|
list_add(&mark->destroy_list, &destroy_list);
|
|
spin_unlock(&destroy_lock);
|
|
wake_up(&destroy_waitq);
|
|
|
|
/*
|
|
* Some groups like to know that marks are being freed. This is a
|
|
* callback to the group function to let it know that this mark
|
|
* is being freed.
|
|
*/
|
|
if (group->ops->freeing_mark)
|
|
group->ops->freeing_mark(mark, group);
|
|
|
|
/*
|
|
* __fsnotify_update_child_dentry_flags(inode);
|
|
*
|
|
* I really want to call that, but we can't, we have no idea if the inode
|
|
* still exists the second we drop the mark->lock.
|
|
*
|
|
* The next time an event arrive to this inode from one of it's children
|
|
* __fsnotify_parent will see that the inode doesn't care about it's
|
|
* children and will update all of these flags then. So really this
|
|
* is just a lazy update (and could be a perf win...)
|
|
*/
|
|
|
|
if (inode && (mark->flags & FSNOTIFY_MARK_FLAG_OBJECT_PINNED))
|
|
iput(inode);
|
|
|
|
/*
|
|
* it's possible that this group tried to destroy itself, but this
|
|
* this mark was simultaneously being freed by inode. If that's the
|
|
* case, we finish freeing the group here.
|
|
*/
|
|
if (unlikely(atomic_dec_and_test(&group->num_marks)))
|
|
fsnotify_final_destroy_group(group);
|
|
}
|
|
|
|
void fsnotify_set_mark_mask_locked(struct fsnotify_mark *mark, __u32 mask)
|
|
{
|
|
assert_spin_locked(&mark->lock);
|
|
|
|
mark->mask = mask;
|
|
|
|
if (mark->flags & FSNOTIFY_MARK_FLAG_INODE)
|
|
fsnotify_set_inode_mark_mask_locked(mark, mask);
|
|
}
|
|
|
|
void fsnotify_set_mark_ignored_mask_locked(struct fsnotify_mark *mark, __u32 mask)
|
|
{
|
|
assert_spin_locked(&mark->lock);
|
|
|
|
mark->ignored_mask = mask;
|
|
}
|
|
|
|
/*
|
|
* Attach an initialized mark to a given group and fs object.
|
|
* These marks may be used for the fsnotify backend to determine which
|
|
* event types should be delivered to which group.
|
|
*/
|
|
int fsnotify_add_mark(struct fsnotify_mark *mark,
|
|
struct fsnotify_group *group, struct inode *inode,
|
|
struct vfsmount *mnt, int allow_dups)
|
|
{
|
|
int ret = 0;
|
|
|
|
BUG_ON(inode && mnt);
|
|
BUG_ON(!inode && !mnt);
|
|
|
|
/*
|
|
* if this group isn't being testing for inode type events we need
|
|
* to start testing
|
|
*/
|
|
if (inode && unlikely(list_empty(&group->inode_group_list)))
|
|
fsnotify_add_inode_group(group);
|
|
else if (mnt && unlikely(list_empty(&group->vfsmount_group_list)))
|
|
fsnotify_add_vfsmount_group(group);
|
|
|
|
/*
|
|
* LOCKING ORDER!!!!
|
|
* mark->lock
|
|
* group->mark_lock
|
|
* inode->i_lock
|
|
*/
|
|
spin_lock(&mark->lock);
|
|
spin_lock(&group->mark_lock);
|
|
|
|
mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE;
|
|
|
|
mark->group = group;
|
|
list_add(&mark->g_list, &group->marks_list);
|
|
atomic_inc(&group->num_marks);
|
|
fsnotify_get_mark(mark); /* for i_list and g_list */
|
|
|
|
if (inode) {
|
|
ret = fsnotify_add_inode_mark(mark, group, inode, allow_dups);
|
|
if (ret)
|
|
goto err;
|
|
} else if (mnt) {
|
|
ret = fsnotify_add_vfsmount_mark(mark, group, mnt, allow_dups);
|
|
if (ret)
|
|
goto err;
|
|
} else {
|
|
BUG();
|
|
}
|
|
|
|
spin_unlock(&group->mark_lock);
|
|
|
|
/* this will pin the object if appropriate */
|
|
fsnotify_set_mark_mask_locked(mark, mark->mask);
|
|
|
|
spin_unlock(&mark->lock);
|
|
|
|
if (inode)
|
|
__fsnotify_update_child_dentry_flags(inode);
|
|
|
|
return ret;
|
|
err:
|
|
mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
|
|
list_del_init(&mark->g_list);
|
|
mark->group = NULL;
|
|
atomic_dec(&group->num_marks);
|
|
|
|
spin_unlock(&group->mark_lock);
|
|
spin_unlock(&mark->lock);
|
|
|
|
spin_lock(&destroy_lock);
|
|
list_add(&mark->destroy_list, &destroy_list);
|
|
spin_unlock(&destroy_lock);
|
|
wake_up(&destroy_waitq);
|
|
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* clear any marks in a group in which mark->flags & flags is true
|
|
*/
|
|
void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group,
|
|
unsigned int flags)
|
|
{
|
|
struct fsnotify_mark *lmark, *mark;
|
|
LIST_HEAD(free_list);
|
|
|
|
spin_lock(&group->mark_lock);
|
|
list_for_each_entry_safe(mark, lmark, &group->marks_list, g_list) {
|
|
if (mark->flags & flags) {
|
|
list_add(&mark->free_g_list, &free_list);
|
|
list_del_init(&mark->g_list);
|
|
fsnotify_get_mark(mark);
|
|
}
|
|
}
|
|
spin_unlock(&group->mark_lock);
|
|
|
|
list_for_each_entry_safe(mark, lmark, &free_list, free_g_list) {
|
|
fsnotify_destroy_mark(mark);
|
|
fsnotify_put_mark(mark);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Given a group, destroy all of the marks associated with that group.
|
|
*/
|
|
void fsnotify_clear_marks_by_group(struct fsnotify_group *group)
|
|
{
|
|
fsnotify_clear_marks_by_group_flags(group, (unsigned int)-1);
|
|
}
|
|
|
|
void fsnotify_duplicate_mark(struct fsnotify_mark *new, struct fsnotify_mark *old)
|
|
{
|
|
assert_spin_locked(&old->lock);
|
|
new->i.inode = old->i.inode;
|
|
new->m.mnt = old->m.mnt;
|
|
new->group = old->group;
|
|
new->mask = old->mask;
|
|
new->free_mark = old->free_mark;
|
|
}
|
|
|
|
/*
|
|
* Nothing fancy, just initialize lists and locks and counters.
|
|
*/
|
|
void fsnotify_init_mark(struct fsnotify_mark *mark,
|
|
void (*free_mark)(struct fsnotify_mark *mark))
|
|
{
|
|
memset(mark, 0, sizeof(*mark));
|
|
spin_lock_init(&mark->lock);
|
|
atomic_set(&mark->refcnt, 1);
|
|
mark->free_mark = free_mark;
|
|
}
|
|
|
|
static int fsnotify_mark_destroy(void *ignored)
|
|
{
|
|
struct fsnotify_mark *mark, *next;
|
|
LIST_HEAD(private_destroy_list);
|
|
|
|
for (;;) {
|
|
spin_lock(&destroy_lock);
|
|
/* exchange the list head */
|
|
list_replace_init(&destroy_list, &private_destroy_list);
|
|
spin_unlock(&destroy_lock);
|
|
|
|
synchronize_srcu(&fsnotify_mark_srcu);
|
|
|
|
list_for_each_entry_safe(mark, next, &private_destroy_list, destroy_list) {
|
|
list_del_init(&mark->destroy_list);
|
|
fsnotify_put_mark(mark);
|
|
}
|
|
|
|
wait_event_interruptible(destroy_waitq, !list_empty(&destroy_list));
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int __init fsnotify_mark_init(void)
|
|
{
|
|
struct task_struct *thread;
|
|
|
|
thread = kthread_run(fsnotify_mark_destroy, NULL,
|
|
"fsnotify_mark");
|
|
if (IS_ERR(thread))
|
|
panic("unable to start fsnotify mark destruction thread.");
|
|
|
|
return 0;
|
|
}
|
|
device_initcall(fsnotify_mark_init);
|