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Commit 6d98c3cc authored by Wengang Wang's avatar Wengang Wang Committed by Joel Becker
Browse files

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: default avatarWengang Wang <wen.gang.wang@oracle.com>
Cc: stable@kernel.org
Signed-off-by: default avatarJoel Becker <joel.becker@oracle.com>
parent 6eda3dd3

fs/ocfs2/dlm/dlmmaster.c

+2 −3
Original line number Diff line number Diff line
@@ -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) {