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Commit 012572d4 authored by Joseph Qi's avatar Joseph Qi Committed by Linus Torvalds
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ocfs2/dlm: fix deadlock when dispatch assert master 



The order of the following three spinlocks should be:
dlm_domain_lock < dlm_ctxt->spinlock < dlm_lock_resource->spinlock

But dlm_dispatch_assert_master() is called while holding
dlm_ctxt->spinlock and dlm_lock_resource->spinlock, and then it calls
dlm_grab() which will take dlm_domain_lock.

Once another thread (for example, dlm_query_join_handler) has already
taken dlm_domain_lock, and tries to take dlm_ctxt->spinlock deadlock
happens.

Signed-off-by: default avatarJoseph Qi <joseph.qi@huawei.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: "Junxiao Bi" <junxiao.bi@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7a07b503

fs/ocfs2/dlm/dlmmaster.c

+6 −3
Original line number Diff line number Diff line
@@ -1439,6 +1439,7 @@ int dlm_master_request_handler(struct o2net_msg *msg, u32 len, void *data, 
	int found, ret;

	int set_maybe;

	int dispatch_assert = 0;

	int dispatched = 0;



	if (!dlm_grab(dlm))

		return DLM_MASTER_RESP_NO;
@@ -1658,14 +1659,17 @@ int dlm_master_request_handler(struct o2net_msg *msg, u32 len, void *data, 
			mlog(ML_ERROR, "failed to dispatch assert master work\n");

			response = DLM_MASTER_RESP_ERROR;

			dlm_lockres_put(res);

		} else

		} else {

			dispatched = 1;

			__dlm_lockres_grab_inflight_worker(dlm, res);

		}

		spin_unlock(&res->spinlock);

	} else {

		if (res)

			dlm_lockres_put(res);

	}



	if (!dispatched)

		dlm_put(dlm);

	return response;

}
@@ -2090,7 +2094,6 @@ int dlm_dispatch_assert_master(struct dlm_ctxt *dlm, 




	/* queue up work for dlm_assert_master_worker */

	dlm_grab(dlm);  /* get an extra ref for the work item */

	dlm_init_work_item(dlm, item, dlm_assert_master_worker, NULL);

	item->u.am.lockres = res; /* already have a ref */

	/* can optionally ignore node numbers higher than this node */

fs/ocfs2/dlm/dlmrecovery.c

+6 −2
Original line number Diff line number Diff line
@@ -1694,6 +1694,7 @@ int dlm_master_requery_handler(struct o2net_msg *msg, u32 len, void *data, 
	unsigned int hash;

	int master = DLM_LOCK_RES_OWNER_UNKNOWN;

	u32 flags = DLM_ASSERT_MASTER_REQUERY;

	int dispatched = 0;



	if (!dlm_grab(dlm)) {

		/* since the domain has gone away on this
@@ -1719,8 +1720,10 @@ int dlm_master_requery_handler(struct o2net_msg *msg, u32 len, void *data, 
				dlm_put(dlm);

				/* sender will take care of this and retry */

				return ret;

			} else

			} else {

				dispatched = 1;

				__dlm_lockres_grab_inflight_worker(dlm, res);

			}

			spin_unlock(&res->spinlock);

		} else {

			/* put.. incase we are not the master */
@@ -1730,6 +1733,7 @@ int dlm_master_requery_handler(struct o2net_msg *msg, u32 len, void *data, 
	}

	spin_unlock(&dlm->spinlock);



	if (!dispatched)

		dlm_put(dlm);

	return master;

}