From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755479AbcAXWD7 (ORCPT ); Sun, 24 Jan 2016 17:03:59 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:60599 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754820AbcAXWCp (ORCPT ); Sun, 24 Jan 2016 17:02:45 -0500 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Joe Thornber , Mike Snitzer , Luis Henriques Subject: [PATCH 3.16.y-ckt 034/128] dm thin metadata: fix bug when taking a metadata snapshot Date: Sun, 24 Jan 2016 21:59:49 +0000 Message-Id: <1453672883-2708-35-git-send-email-luis.henriques@canonical.com> In-Reply-To: <1453672883-2708-1-git-send-email-luis.henriques@canonical.com> References: <1453672883-2708-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.7-ckt23 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ From: Joe Thornber commit 49e99fc717f624aa75ca755d6e7bc029efd3f0e9 upstream. When you take a metadata snapshot the btree roots for the mapping and details tree need to have their reference counts incremented so they persist for the lifetime of the metadata snap. The roots being incremented were those currently written in the superblock, which could possibly be out of date if concurrent IO is triggering new mappings, breaking of sharing, etc. Fix this by performing a commit with the metadata lock held while taking a metadata snapshot. Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer Signed-off-by: Luis Henriques --- drivers/md/dm-thin-metadata.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/md/dm-thin-metadata.c b/drivers/md/dm-thin-metadata.c index 3412b86e79fd..7768de60f699 100644 --- a/drivers/md/dm-thin-metadata.c +++ b/drivers/md/dm-thin-metadata.c @@ -1205,6 +1205,12 @@ static int __reserve_metadata_snap(struct dm_pool_metadata *pmd) dm_block_t held_root; /* + * We commit to ensure the btree roots which we increment in a + * moment are up to date. + */ + __commit_transaction(pmd); + + /* * Copy the superblock. */ dm_sm_inc_block(pmd->metadata_sm, THIN_SUPERBLOCK_LOCATION);