linux-kernel - [PATCH 3.12 001/182] dlm: Avoid that dlm_release

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Date:	Tue, 13 May 2014 11:25:53 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Bart Van Assche <bvanassche@....org>,
	David Teigland <teigland@...hat.com>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 001/182] dlm: Avoid that dlm_release_lockspace() incorrectly returns -EBUSY

From: Bart Van Assche <bvanassche@....org>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit a97f4a66d8ee4faf0f31cc4ad3f4aa0baef23fc7 upstream.

When dlm_release_lockspace(ls, 1) is invoked on a busy system
immediately after the last dlm_unlock() AST has finished it can occur
that lkb_idr_is_local() is invoked for the unlocked LKB since removal
from ls_lkbidr only occurs after the AST has returned. If that happens
dlm_release_lockspace(ls, 1) will return -EBUSY instead of releasing
the lockspace. Fix this race condition by changing lkb_idr_is_local()
such that it only returns true for LKB's that have not yet been
unlocked.

Signed-off-by: Bart Van Assche <bvanassche@....org>
Signed-off-by: David Teigland <teigland@...hat.com>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 fs/dlm/lockspace.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/fs/dlm/lockspace.c b/fs/dlm/lockspace.c
index 88556dc0458e..d5abafd56a6d 100644
--- a/fs/dlm/lockspace.c
+++ b/fs/dlm/lockspace.c
@@ -706,9 +706,7 @@ static int lkb_idr_is_local(int id, void *p, void *data)
 {
 	struct dlm_lkb *lkb = p;

-	if (!lkb->lkb_nodeid)
-		return 1;
-	return 0;
+	return lkb->lkb_nodeid == 0 && lkb->lkb_grmode != DLM_LOCK_IV;
 }

 static int lkb_idr_is_any(int id, void *p, void *data)
-- 
1.9.3

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