Commit 27bf6305 authored Jun 23, 2014 by Tariq Saeed Committed by Linus Torvalds Jun 23, 2014

ocfs2: fix deadlock when two nodes are converting same lock from PR to EX and...


ocfs2: fix deadlock when two nodes are converting same lock from PR to EX and idletimeout closes conn

Orabug: 18639535

Two node cluster and both nodes hold a lock at PR level and both want to
convert to EX at the same time.  Master node 1 has sent BAST and then
closes the connection due to idletime out.  Node 0 receives BAST, sends
unlock req with cancel flag but gets error -ENOTCONN.  The problem is
this error is ignored in dlm_send_remote_unlock_request() on the
**incorrect** assumption that the master is dead.  See NOTE in comment
why it returns DLM_NORMAL.  Upon getting DLM_NORMAL, node 0 proceeds to
sends convert (without cancel flg) which fails with -ENOTCONN.  waits 5
sec and resends.

This time gets DLM_IVLOCKID from the master since lock not found in
grant, it had been moved to converting queue in response to conv PR->EX
req.  No way out.

Node 1 (master)				Node 0
==============				======

  lock mode PR				PR

  convert PR -> EX
  mv grant -> convert and que BAST
  ...
                     <-------- convert PR -> EX
  convert que looks like this: ((node 1, PR -> EX) (node 0, PR -> EX))
  ...
                        BAST (want PR -> NL)
                     ------------------>
  ...
  idle timout, conn closed
                                ...
                                In response to BAST,
                                sends unlock with cancel convert flag
                                gets -ENOTCONN. Ignores and
                                sends remote convert request
                                gets -ENOTCONN, waits 5 Sec, retries
  ...
  reconnects
                   <----------------- convert req goes through on next try
  does not find lock on grant que
                   status DLM_IVLOCKID
                   ------------------>
  ...

No way out.  Fix is to keep retrying unlock with cancel flag until it
succeeds or the master dies.

Signed-off-by: Tariq Saeed <tariq.x.saeed@oracle.com>
Reviewed-by: Mark Fasheh <mfasheh@suse.de>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 5fb1beb0

fs/ocfs2/dlm/dlmunlock.c

+13 −5

Original line number	Diff line number	Diff line
		@@ -191,7 +191,9 @@ static enum dlm_status dlmunlock_common(struct dlm_ctxt *dlm,
		DLM_UNLOCK_CLEAR_CONVERT_TYPE);
		} else if (status == DLM_RECOVERING \|\|
		status == DLM_MIGRATING \|\|
		status == DLM_FORWARD) {
		status == DLM_FORWARD \|\|
		status == DLM_NOLOCKMGR
		) {
		/* must clear the actions because this unlock
		* is about to be retried. cannot free or do
		* any list manipulation. */
		@@ -200,7 +202,8 @@ static enum dlm_status dlmunlock_common(struct dlm_ctxt *dlm,
		res->lockname.name,
		status==DLM_RECOVERING?"recovering":
		(status==DLM_MIGRATING?"migrating":
		"forward"));
		(status == DLM_FORWARD ? "forward" :
		"nolockmanager")));
		actions = 0;
		}
		if (flags & LKM_CANCEL)
		@@ -364,7 +367,10 @@ static enum dlm_status dlm_send_remote_unlock_request(struct dlm_ctxt *dlm,
		* updated state to the recovery master. this thread
		* just needs to finish out the operation and call
		* the unlockast. */
		if (dlm_is_node_dead(dlm, owner))
		ret = DLM_NORMAL;
		else
		ret = DLM_NOLOCKMGR;
		} else {
		/* something bad. this will BUG in ocfs2 */
		ret = dlm_err_to_dlm_status(tmpret);
		@@ -638,7 +644,9 @@ retry:

		if (status == DLM_RECOVERING \|\|
		status == DLM_MIGRATING \|\|
		status == DLM_FORWARD) {
		status == DLM_FORWARD \|\|
		status == DLM_NOLOCKMGR) {

		/* We want to go away for a tiny bit to allow recovery
		* / migration to complete on this resource. I don't
		* know of any wait queue we could sleep on as this
		@@ -650,7 +658,7 @@ retry:
		msleep(50);

		mlog(0, "retrying unlock due to pending recovery/"
		"migration/in-progress\n");
		"migration/in-progress/reconnect\n");
		goto retry;
		}

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