From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932909AbZKFWk3 (ORCPT ); Fri, 6 Nov 2009 17:40:29 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932482AbZKFWkZ (ORCPT ); Fri, 6 Nov 2009 17:40:25 -0500 Received: from kroah.org ([198.145.64.141]:56752 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932357AbZKFWWi (ORCPT ); Fri, 6 Nov 2009 17:22:38 -0500 X-Mailbox-Line: From gregkh@mini.kroah.org Fri Nov 6 14:15:41 2009 Message-Id: <20091106221541.821263847@mini.kroah.org> User-Agent: quilt/0.48-1 Date: Fri, 06 Nov 2009 14:14:22 -0800 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Mikulas Patocka , Alasdair G Kergon Subject: [24/99] dm snapshot: lock snapshot while supplying status References: <20091106221358.309857998@mini.kroah.org> Content-Disposition: inline; filename=dm-snapshot-lock-snapshot-while-supplying-status.patch In-Reply-To: <20091106221850.GA15408@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.31-stable review patch. If anyone has any objections, please let us know. ------------------ From: Mikulas Patocka commit 4c6fff445d7aa753957856278d4d93bcad6e2c14 upstream. This patch locks the snapshot when returning status. It fixes a race when it could return an invalid number of free chunks if someone was simultaneously modifying it. Signed-off-by: Mikulas Patocka Signed-off-by: Alasdair G Kergon Signed-off-by: Greg Kroah-Hartman --- drivers/md/dm-snap.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c @@ -1147,6 +1147,8 @@ static int snapshot_status(struct dm_tar unsigned sz = 0; struct dm_snapshot *snap = ti->private; + down_write(&snap->lock); + switch (type) { case STATUSTYPE_INFO: if (!snap->valid) @@ -1178,6 +1180,8 @@ static int snapshot_status(struct dm_tar break; } + up_write(&snap->lock); + return 0; }