From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753077Ab2GZVWc (ORCPT ); Thu, 26 Jul 2012 17:22:32 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:55834 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753228Ab2GZVWG (ORCPT ); Thu, 26 Jul 2012 17:22:06 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg KH , torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Mikulas Patocka , Mike Snitzer , Alasdair G Kergon Subject: [ 19/23] dm thin: do not send discards to shared blocks Date: Thu, 26 Jul 2012 14:19:58 -0700 Message-Id: <20120726211407.616176925@linuxfoundation.org> X-Mailer: git-send-email 1.7.10.1.362.g242cab3 In-Reply-To: <20120726211405.959857593@linuxfoundation.org> References: <20120726211420.GA7678@kroah.com> <20120726211405.959857593@linuxfoundation.org> User-Agent: quilt/0.60-20.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Greg KH 3.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mikulas Patocka commit 650d2a06b4fe1cc1d218c20e256650f68bf0ca31 upstream. When process_discard receives a partial discard that doesn't cover a full block, it sends this discard down to that block. Unfortunately, the block can be shared and the discard would corrupt the other snapshots sharing this block. This patch detects block sharing and ends the discard with success when sending it to the shared block. The above change means that if the device supports discard it can't be guaranteed that a discard request zeroes data. Therefore, we set ti->discard_zeroes_data_unsupported. Thin target discard support with this bug arrived in commit 104655fd4dcebd50068ef30253a001da72e3a081 (dm thin: support discards). Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer Signed-off-by: Alasdair G Kergon Signed-off-by: Greg Kroah-Hartman --- drivers/md/dm-thin.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) --- a/drivers/md/dm-thin.c +++ b/drivers/md/dm-thin.c @@ -1240,7 +1240,10 @@ static void process_discard(struct thin_ cell_release_singleton(cell, bio); cell_release_singleton(cell2, bio); - remap_and_issue(tc, bio, lookup_result.block); + if ((!lookup_result.shared) && pool->pf.discard_passdown) + remap_and_issue(tc, bio, lookup_result.block); + else + bio_endio(bio, 0); } break; @@ -2575,6 +2578,7 @@ static int thin_ctr(struct dm_target *ti if (tc->pool->pf.discard_enabled) { ti->discards_supported = 1; ti->num_discard_requests = 1; + ti->discard_zeroes_data_unsupported = 1; } dm_put(pool_md);