Subject: + ocfs2-dlm-fix-possible-convertion-deadlock.patch added to -mm tree
To: xuejiufei@xxxxxxxxxx,jlbec@xxxxxxxxxxxx,mfasheh@xxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Wed, 21 May 2014 15:25:54 -0700
The patch titled
Subject: ocfs2/dlm: fix possible convert=sion deadlock
has been added to the -mm tree. Its filename is
ocfs2-dlm-fix-possible-convertion-deadlock.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/ocfs2-dlm-fix-possible-convertion-deadlock.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/ocfs2-dlm-fix-possible-convertion-deadlock.patch
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From: Xue jiufei <xuejiufei@xxxxxxxxxx>
Subject: ocfs2/dlm: fix possible convert=sion deadlock
We found there is a conversion deadlock when the owner of lockres happened
to crash before send DLM_PROXY_AST_MSG for a downconverting lock. The
situation is as follows:
Node1 Node2 Node3
the owner of lockresA
lock_1 granted at EX mode
and call ocfs2_cluster_unlock
to decrease ex_holders.
converting lock_3 from
NL to EX
send DLM_PROXY_AST_MSG
to Node1, asking Node 1
to downconvert.
receiving DLM_PROXY_AST_MSG,
thread ocfs2dc send
DLM_CONVERT_LOCK_MSG
to Node2 to downconvert
lock_1(EX->NL).
lock_1 can be granted and
put it into pending_asts
list, return DLM_NORMAL.
then something happened
and Node2 crashed.
received DLM_NORMAL, waiting
for DLM_PROXY_AST_MSG.
selected as the recovery
master, receving migrate
lock from Node1, queue
lock_1 to the tail of
converting list.
After dlm recovery, converting list in the master of lockresA(Node3) will
be: converting list head <-> lock_3(NL->EX) <->lock_1(EX<->NL). Requested
mode of lock_3 is not compatible with the granted mode of lock_1, so it
can not be granted. and lock_1 can not downconvert because covnerting
queue is strictly FIFO. So a deadlock is created. We think function
dlm_process_recovery_data() should queue_ast for lock_1 or alter the order
of lock_1 and lock_3, so dlm_thread can process lock_1 first. And if
there are multiple downconverting locks, they must convert form PR to NL,
so no need to sort them.
Signed-off-by: joyce.xue <xuejiufei@xxxxxxxxxx>
Cc: Mark Fasheh <mfasheh@xxxxxxxx>
Cc: Joel Becker <jlbec@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/ocfs2/dlm/dlmrecovery.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff -puN fs/ocfs2/dlm/dlmrecovery.c~ocfs2-dlm-fix-possible-convertion-deadlock fs/ocfs2/dlm/dlmrecovery.c
--- a/fs/ocfs2/dlm/dlmrecovery.c~ocfs2-dlm-fix-possible-convertion-deadlock
+++ a/fs/ocfs2/dlm/dlmrecovery.c
@@ -1986,7 +1986,15 @@ skip_lvb:
}
if (!bad) {
dlm_lock_get(newlock);
- list_add_tail(&newlock->list, queue);
+ if (mres->flags & DLM_MRES_RECOVERY &&
+ ml->list == DLM_CONVERTING_LIST &&
+ newlock->ml.type >
+ newlock->ml.convert_type) {
+ /* newlock is doing downconvert, add it to the
+ * head of converting list */
+ list_add(&newlock->list, queue);
+ } else
+ list_add_tail(&newlock->list, queue);
mlog(0, "%s:%.*s: added lock for node %u, "
"setting refmap bit\n", dlm->name,
res->lockname.len, res->lockname.name, ml->node);
_
Patches currently in -mm which might be from xuejiufei@xxxxxxxxxx are
ocfs2-dlm-fix-possible-convertion-deadlock.patch
ocfs2-do-not-return-dlm_migrate_response_mastery_ref-to-avoid-endlessloop-during-umount.patch
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