ocfs2/dlm: fix a dead lock
When we have to take both dlm->master_lock and lockres->spinlock,
take them in order
lockres->spinlock and then dlm->master_lock.
The patch fixes a violation of the rule.
We can simply move taking dlm->master_lock to where we have dropped res->spinlock
since when we access res->state and free mle memory we don't need master_lock's
protection.
Signed-off-by: Wengang Wang <wen.gang.wang@oracle.com>
Cc: stable@kernel.org
Signed-off-by: Joel Becker <joel.becker@oracle.com>
diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
index 94b97fc..6d098b8 100644
--- a/fs/ocfs2/dlm/dlmmaster.c
+++ b/fs/ocfs2/dlm/dlmmaster.c
@@ -3050,8 +3050,6 @@
/* check for pre-existing lock */
spin_lock(&dlm->spinlock);
res = __dlm_lookup_lockres(dlm, name, namelen, hash);
- spin_lock(&dlm->master_lock);
-
if (res) {
spin_lock(&res->spinlock);
if (res->state & DLM_LOCK_RES_RECOVERING) {
@@ -3069,14 +3067,15 @@
spin_unlock(&res->spinlock);
}
+ spin_lock(&dlm->master_lock);
/* ignore status. only nonzero status would BUG. */
ret = dlm_add_migration_mle(dlm, res, mle, &oldmle,
name, namelen,
migrate->new_master,
migrate->master);
-unlock:
spin_unlock(&dlm->master_lock);
+unlock:
spin_unlock(&dlm->spinlock);
if (oldmle) {
