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fsnotify: take groups mark_lock before mark lock

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Race-free addition and removal of a mark to a groups mark list would be easier
if we could lock the mark list of group before we lock the specific mark.
This patch changes the order used to add/remove marks to/from mark lists from

1. mark->lock
2. group->mark_lock
3. inode->i_lock

to

1. group->mark_lock
2. mark->lock
3. inode->i_lock

Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Signed-off-by: Eric Paris <eparis@redhat.com>
This commit is contained in:
Lino Sanfilippo 2011-06-14 17:29:48 +02:00 committed by Eric Paris
parent 23e964c284
commit 104d06f08e
1 changed files with 16 additions and 10 deletions
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26
fs/notify/mark.c
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@ -127,20 +127,27 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark)
struct inode *inode = NULL;
spin_lock(&mark->lock);
/* dont get the group from a mark that is not alive yet */
if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) {
spin_unlock(&mark->lock);
return;
}
fsnotify_get_group(mark->group);
group = mark->group;
spin_unlock(&mark->lock);
spin_lock(&group->mark_lock);
spin_lock(&mark->lock);
/* something else already called this function on this mark */
if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) {
spin_unlock(&mark->lock);
spin_unlock(&group->mark_lock);
goto put_group;
}
mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
spin_lock(&group->mark_lock);
if (mark->flags & FSNOTIFY_MARK_FLAG_INODE) {
inode = mark->i.inode;
fsnotify_destroy_inode_mark(mark);
@ -151,8 +158,8 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark)
list_del_init(&mark->g_list);
spin_unlock(&group->mark_lock);
spin_unlock(&mark->lock);
spin_unlock(&group->mark_lock);
spin_lock(&destroy_lock);
list_add(&mark->destroy_list, &destroy_list);
@ -225,13 +232,13 @@ int fsnotify_add_mark(struct fsnotify_mark *mark,
/*
* LOCKING ORDER!!!!
* mark->lock
* group->mark_lock
* mark->lock
* inode->i_lock
*/
spin_lock(&mark->lock);
spin_lock(&group->mark_lock);
spin_lock(&mark->lock);
mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE;
fsnotify_get_group(group);
@ -252,13 +259,12 @@ int fsnotify_add_mark(struct fsnotify_mark *mark,
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);
spin_unlock(&group->mark_lock);
if (inode)
__fsnotify_update_child_dentry_flags(inode);
@ -270,8 +276,8 @@ err:
mark->group = NULL;
atomic_dec(&group->num_marks);
spin_unlock(&group->mark_lock);
spin_unlock(&mark->lock);
spin_unlock(&group->mark_lock);
spin_lock(&destroy_lock);
list_add(&mark->destroy_list, &destroy_list);