From: Jinshan Xiong <jinshan.xiong@intel.com>
Date: Wed, 4 Jun 2014 00:34:21 +0000 (-0700)
Subject: LU-4861 osc: a deadlock problem in osc completion ast
X-Git-Tag: 2.6.0-RC1~67
X-Git-Url: https://git.whamcloud.com/?p=fs%2Flustre-release.git;a=commitdiff_plain;h=6fdcac2361d75713c5b08fa06069935a78266ac3

LU-4861 osc: a deadlock problem in osc completion ast

In osc_ldlm_completion_ast(), it tries to hold mutex of cl_lock
and update the lock even it's known that the lock is not granted,
this can introduce a deadlock case if the process is matching a
dlm lock with the calling stack:
  osc_lock_enqueue()
    -> osc_enqueue_base()
      -> ldlm_lock_match()
        -> osc_ldlm_completion_ast()
          -> cl_lock_mutex_get()
The enqueuing lock and the lock for completion_ast() are different
lock. This is a deadlock case because we're holding a lock's mutex
and then request the other.

It's not necessary to acquire the lock in completion_ast() if it's
known that the lock has not been granted.

Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
Change-Id: Ia8c0a4cb1e48c9f7fd921052174ce4d8d07713b1
Reviewed-on: http://review.whamcloud.com/10581
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Bobi Jam <bobijam@gmail.com>
Reviewed-by: Patrick Farrell <paf@cray.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
---

diff --git a/lustre/osc/osc_lock.c b/lustre/osc/osc_lock.c
index 3f828e0..fa076cf0 100644
--- a/lustre/osc/osc_lock.c
+++ b/lustre/osc/osc_lock.c
@@ -793,8 +793,11 @@ static int osc_ldlm_completion_ast(struct ldlm_lock *dlmlock,
         int result;
         int dlmrc;
 
-        /* first, do dlm part of the work */
-        dlmrc = ldlm_completion_ast_async(dlmlock, flags, data);
+	/* first, do dlm part of the work */
+	dlmrc = ldlm_completion_ast_async(dlmlock, flags, data);
+	if (flags == LDLM_FL_WAIT_NOREPROC)
+		return dlmrc;
+
         /* then, notify cl_lock */
         env = cl_env_nested_get(&nest);
         if (!IS_ERR(env)) {