akpm at linux-foundation.org
2014-Jun-09 20:04 UTC
[Ocfs2-devel] [patch 2/8] ocfs2: fix deadlock when two nodes are converting same lock from PR to EX and idletimeout closes conn
From: Tariq Saeed <tariq.x.saeed at oracle.com>
Subject: 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 at oracle.com>
Cc: Mark Fasheh <mfasheh at suse.com>
Cc: Joel Becker <jlbec at evilplan.org>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
---
fs/ocfs2/dlm/dlmunlock.c | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)
diff -puN
fs/ocfs2/dlm/dlmunlock.c~deadlock-when-two-nodes-are-converting-same-lock-from-pr-to-ex-and-idletimeout-closes-conn
fs/ocfs2/dlm/dlmunlock.c
---
a/fs/ocfs2/dlm/dlmunlock.c~deadlock-when-two-nodes-are-converting-same-lock-from-pr-to-ex-and-idletimeout-closes-conn
+++ a/fs/ocfs2/dlm/dlmunlock.c
@@ -191,7 +191,9 @@ static enum dlm_status dlmunlock_common(
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(
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_u
* updated state to the recovery master. this thread
* just needs to finish out the operation and call
* the unlockast. */
- ret = DLM_NORMAL;
+ 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;
}
_
Mark Fasheh
2014-Jun-12 23:05 UTC
[Ocfs2-devel] [patch 2/8] ocfs2: fix deadlock when two nodes are converting same lock from PR to EX and idletimeout closes conn
On Mon, Jun 09, 2014 at 01:04:00PM -0700, Andrew Morton wrote:> From: Tariq Saeed <tariq.x.saeed at oracle.com> > Subject: 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 at oracle.com> > Cc: Mark Fasheh <mfasheh at suse.com> > Cc: Joel Becker <jlbec at evilplan.org> > Signed-off-by: Andrew Morton <akpm at linux-foundation.org>That looks good, thanks Tariq, in particular for the detailed explanation. Reviewed-by: Mark Fasheh <mfasheh at suse.de> --Mark -- Mark Fasheh