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ocfs2/dlm: fix a dead lock

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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>
This commit is contained in:
Wengang Wang 2010-07-16 23:13:33 +08:00 committed by Joel Becker
parent 6eda3dd33f
commit 6d98c3ccb5
1 changed files with 2 additions and 3 deletions
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5
fs/ocfs2/dlm/dlmmaster.c
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@ -3050,8 +3050,6 @@ int dlm_migrate_request_handler(struct o2net_msg *msg, u32 len, void *data,
/* 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 @@ int dlm_migrate_request_handler(struct o2net_msg *msg, u32 len, void *data,
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) {