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@xxxxxx>
---
fs/notify/mark.c | 21 +++++++++------------
1 files changed, 9 insertions(+), 12 deletions(-)
diff --git a/fs/notify/mark.c b/fs/notify/mark.c
index 28b64eb..1ac0447 100644
--- a/fs/notify/mark.c
+++ b/fs/notify/mark.c
@@ -114,22 +114,21 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark)
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;
+ group = mark->group;
+ spin_unlock(&mark->lock);
+
+ spin_lock(&group->mark_lock);
+ spin_lock(&mark->lock);
/* 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);
@@ -137,11 +136,11 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark)
fsnotify_destroy_vfsmount_mark(mark);
else
BUG();
+ spin_unlock(&mark->lock);
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);
@@ -217,8 +216,8 @@ int fsnotify_add_mark(struct fsnotify_mark *mark,
* group->mark_lock
* inode->i_lock
*/
- spin_lock(&mark->lock);
spin_lock(&group->mark_lock);
+ spin_lock(&mark->lock);
mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE;
mark->group = group;
@@ -235,13 +234,11 @@ int fsnotify_add_mark(struct fsnotify_mark *mark,
BUG();
if (ret)
goto err;
-
- 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);
@@ -253,8 +250,8 @@ 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);
--
1.5.6.5
--
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