From: Xue jiufei <xuejiufei@huawei.com>
Date: Thu, 27 Jun 2013 23:51:06 +0000 (+1000)
Subject: ocfs2: dlmlock_master() should return DLM_NORMAL after adding lock to blocked list
X-Git-Tag: next-20130628~3^2~634
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=ca19662f588d75b7357a78751bcb64373c719707;p=karo-tx-linux.git

ocfs2: dlmlock_master() should return DLM_NORMAL after adding lock to blocked list

dlmlock_master() returns DLM_RECOVERING/DLM_MIGRATING/ DLM_FORWAR after
adding lock to blocked list if lockres has the state
DLM_LOCK_RES_RECOVERING/DLM_LOCK_RES_MIGRATING/ DLM_LOCK_RES_IN_PROGRESS.
so it will retry in dlmlock().  And this may cause dlm_thread fall into an
infinite loop

	Thread1                                  dlm_thread
calls dlm_lock->dlmlock_master,
if lockresA is in state
DLM_LOCK_RES_RECOVERING, calls
__dlm_wait_on_lockres() and waits
until others threads clear this
state;

If cannot grant this lock,
adding lock to blocked list,
and return DLM_RECOVERING;

                                        Grant this lock and move it to
                                        grant list;

After a while, retry and
calls list_add_tail(), adding lock
to blocked list again.

Granted and blocked list of this lockres will become the following
conditions:

    lock_res->granted.next = dlm_lock->list_head;
    lock_res->blocked.next = dlm_lock->list_head;
    dlm_lock->list_head.next = dlm_lock_resource->blocked;

When dlm_thread traverses the granted list, it will fall into an endless
loop, checking dlm_lock.list_head, dlm_lock->list_head.next
(i.e.lock_res->blocked), lock_res->blocked.next(i.e.dlm_lock.list_head
again) .....

Signed-off-by: joyce <xuejiufei@huawei.com>
Reviewed-by: jensen <shencanquan@huawei.com>
Cc: Jeff Liu <jeff.liu@oracle.com>
Cc: Sunil Mushran <sunil.mushran@gmail.com>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/fs/ocfs2/dlm/dlmlock.c b/fs/ocfs2/dlm/dlmlock.c
index 975810b98492..47e67c2d228f 100644
--- a/fs/ocfs2/dlm/dlmlock.c
+++ b/fs/ocfs2/dlm/dlmlock.c
@@ -178,6 +178,7 @@ static enum dlm_status dlmlock_master(struct dlm_ctxt *dlm,
 				     lock->ml.node);
 			}
 		} else {
+			status = DLM_NORMAL;
 			dlm_lock_get(lock);
 			list_add_tail(&lock->list, &res->blocked);
 			kick_thread = 1;