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Thread-Topic: [PATCH AUTOSEL for 4.4 072/115] md/raid6: Fix anomily when recovering a single device in RAID6. Thread-Index: AQHTsz9gKSh91ooA6Eufhr23OMq8uA== Date: Sat, 3 Mar 2018 22:31:31 +0000 Message-ID: <20180303223010.27106-72-alexander.levin@microsoft.com> References: <20180303223010.27106-1-alexander.levin@microsoft.com> In-Reply-To: <20180303223010.27106-1-alexander.levin@microsoft.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [52.168.54.252] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1;MW2PR2101MB1033;6:tIjqSwONQ5IpNVK/Vzm2dREmbTQ/v8vhEYLFuotwR8NTHdkIHbjtJzkQWE9rfAtsWe/TvL9g7Vfj6Z8RTrdEAq7MhqvutHm2NxaI5O/BhBn731Y8R1eZAEhiWXfEF0FyBYWAy7uL6jSEjTQjS38cCy2FQIrm/5tXbhTRmbrZKU5/n3z9pqs/1cBYDzYK4PBIH2VBat3zX4qIPhEfedlqqox9x6SL9uCgfn4BYXo/FKlOs4UfOi3JSGJEBhN6K3r7dMvJqLlGeUr8uUe+3lgotLUYawrk51WIMgwvXiQti/B3BGZorChGjw/fouPUU/I51elCyjo1nEtLtdySVflG8287WYFcDbFvUWQRmQr7Jhs3F5NGcHhnIXD75wodPPTm;5:aEv09saWEJoy6Kf61hckL2RCLYofNLaWcZJgQX1806pzasbcbRkU3R1pemt+SJhqJ7U/tIMaghlUIYwUHvrbp+33zuel6xmZVIZ6HdftaEt8KcSvtu3hFaqS50gtWlWM3jPa6vYN+QZnCe6WleAsUNJE0WPop9Zw4ViGLXfj8YA=;24:ENH7zXumcEhv05k2w5dTlK/Hy+zyXcg7TSO568QAOjpKdaJXu6sg6z8X1UqTR1H+tDJSfvtKknnWV45MbHzdq2V7YBVIsZsUWNruh7kfi/I=;7:kTW6k8JktVxlQy4M2kEdfkzybO4Y8qvEQG+F+OGJCJ48upwjS4MT/5CpvxmSmIOBOSoHB4P89q/b68VXre693GByxKaq6V7Jgf83DDMIoPFoKbQEiWeeK1KAr2+TyeGFzpfGgKO2/7pOsmjrEDC/zlYnfdBpOXPN/lEgmdWfmlRiQi7wR0REllSIYHlDCxVO9mk4Z9H+86l/ismp14m60Zi2KLEKu4XBIeNhxNXtRXox1QufeO79oEoxBAM8QC1f x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: b6b25e31-bf2d-4dce-3296-08d58157b16a x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(4534165)(4627221)(201703031133081)(201702281549075)(48565401081)(5600026)(4604075)(3008032)(2017052603307)(7193020);SRVR:MW2PR2101MB1033; x-ms-traffictypediagnostic: MW2PR2101MB1033: authentication-results: spf=none (sender IP is ) smtp.mailfrom=Alexander.Levin@microsoft.com; x-microsoft-antispam-prvs: x-exchange-antispam-report-test: UriScan:(28532068793085)(89211679590171)(67672495146484)(228905959029699); x-exchange-antispam-report-cfa-test: BCL:0;PCL:0;RULEID:(8211001083)(61425038)(6040501)(2401047)(5005006)(8121501046)(3002001)(10201501046)(93006095)(93001095)(3231220)(944501244)(52105095)(6055026)(61426038)(61427038)(6041288)(20161123558120)(20161123564045)(20161123562045)(20161123560045)(201703131423095)(201702281528075)(20161123555045)(201703061421075)(201703061406153)(6072148)(201708071742011);SRVR:MW2PR2101MB1033;BCL:0;PCL:0;RULEID:;SRVR:MW2PR2101MB1033; x-forefront-prvs: 0600F93FE1 x-forefront-antispam-report: SFV:NSPM;SFS:(10019020)(979002)(39860400002)(39380400002)(376002)(366004)(346002)(396003)(189003)(199004)(3280700002)(3846002)(316002)(6666003)(99286004)(110136005)(2900100001)(54906003)(2501003)(10090500001)(53936002)(5250100002)(106356001)(76176011)(36756003)(107886003)(2950100002)(6486002)(22452003)(6512007)(6436002)(86362001)(6116002)(1076002)(6506007)(2906002)(68736007)(102836004)(4326008)(59450400001)(97736004)(186003)(478600001)(72206003)(26005)(3660700001)(8676002)(25786009)(66066001)(14454004)(5660300001)(305945005)(86612001)(81166006)(8936002)(10290500003)(105586002)(7736002)(81156014)(22906009)(217873001)(969003)(989001)(999001)(1009001)(1019001);DIR:OUT;SFP:1102;SCL:1;SRVR:MW2PR2101MB1033;H:MW2PR2101MB1034.namprd21.prod.outlook.com;FPR:;SPF:None;PTR:InfoNoRecords;MX:1;A:1;LANG:en; x-microsoft-antispam-message-info: n3Ez/H9FJgyD/IYgTru6RlSsg/ohapkUYJFBnT/AtHs4M8BpYuv9GJtq3PbdCbu9d99Hm26N5k6dL0oNhmSYA2OsCO/1JF48BWCQJCC9boeAa2VKR2CkBQ6yYWe9Rzw8BWdvJG7ct2CPqZwgAMzIXw7Ov0QIlXoa93d+xAHAuDg= spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-Network-Message-Id: b6b25e31-bf2d-4dce-3296-08d58157b16a X-MS-Exchange-CrossTenant-originalarrivaltime: 03 Mar 2018 22:31:31.2759 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW2PR2101MB1033 Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: From: NeilBrown [ Upstream commit 7471fb77ce4dc4cb81291189947fcdf621a97987 ] When recoverying a single missing/failed device in a RAID6, those stripes where the Q block is on the missing device are handled a bit differently. In these cases it is easy to check that the P block is correct, so we do. This results in the P block be destroy. Consequently the P block needs to be read a second time in order to compute Q. This causes lots of seeks and hurts performance. It shouldn't be necessary to re-read P as it can be computed from the DATA. But we only compute blocks on missing devices, since c337869d9501 ("md: do not compute parity unless it is on a failed drive"). So relax the change made in that commit to allow computing of the P block in a RAID6 which it is the only missing that block. This makes RAID6 recovery run much faster as the disk just "before" the recovering device is no longer seeking back-and-forth. Reported-by-tested-by: Brad Campbell Reviewed-by: Dan Williams Signed-off-by: NeilBrown Signed-off-by: Shaohua Li Signed-off-by: Sasha Levin --- drivers/md/raid5.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index 86ab6d14d782..ca968c3f25c7 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -3372,9 +3372,20 @@ static int fetch_block(struct stripe_head *sh, struc= t stripe_head_state *s, BUG_ON(test_bit(R5_Wantcompute, &dev->flags)); BUG_ON(test_bit(R5_Wantread, &dev->flags)); BUG_ON(sh->batch_head); + + /* + * In the raid6 case if the only non-uptodate disk is P + * then we already trusted P to compute the other failed + * drives. It is safe to compute rather than re-read P. + * In other cases we only compute blocks from failed + * devices, otherwise check/repair might fail to detect + * a real inconsistency. + */ + if ((s->uptodate =3D=3D disks - 1) && + ((sh->qd_idx >=3D 0 && sh->pd_idx =3D=3D disk_idx) || (s->failed && (disk_idx =3D=3D s->failed_num[0] || - disk_idx =3D=3D s->failed_num[1]))) { + disk_idx =3D=3D s->failed_num[1])))) { /* have disk failed, and we're requested to fetch it; * do compute it */ --=20 2.14.1