fsnotify: take groups mark_lock before mark lock
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>
diff --git a/fs/notify/mark.c b/fs/notify/mark.c
index 3c7a169..32447dc 100644
--- a/fs/notify/mark.c
+++ b/fs/notify/mark.c
@@ -127,20 +127,27 @@
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 @@
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 @@
/*
* 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 @@
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 @@
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);
