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Thread-Topic: [PATCH AUTOSEL for 4.9 143/219] md/raid6: Fix anomily when recovering a single device in RAID6. Thread-Index: AQHTsz8SNZreys5gjUSpYeKEkq9yJA== Date: Sat, 3 Mar 2018 22:29:19 +0000 Message-ID: <20180303222716.26640-143-alexander.levin@microsoft.com> References: <20180303222716.26640-1-alexander.levin@microsoft.com> In-Reply-To: <20180303222716.26640-1-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;MW2PR2101MB0924;6:L4hwUMzFt17f/7kARqDoNWEVxFtCllWuIUJF3Bjj6uw5xSh7uG2WACA/YX0S9yECwWK9tstBwDiWRjePQRKd1EZ0wR9ECfYHgQprh6VTXtJmmVGPLJknjKG1/6HLSEZyWnW2dpdGGvfcq8U//sJ8gl1DL1SSZCuOz8a/ak0NhE1M2k3OaxgrHI7swhipnNJ5Sb5i/4yHGpgCjlxG0ps8FAR2jZLBBkMuQXmgQtfAOa0aSjWrSj55uJAQZla0vOpEe9mOqOkrGOTrypO6+01273nTcwxpoBJ1ce28EzRydk7+5LJvCN9tkLTnF5NUTmDDjs0jfVDbWLbT9Rj2JvWLTyioIR2eC1uOGcVGJ9Ax2Dk=;5:WWNGmcUAhl0MeULtVcPa1kawinERVuLeu5T1vuoI5yb1shb5zDIYRZRzlxtZEv5AQZFzB9PiJNxMw9j0jo2U50Wyg/cnO7o0sMYeh8PUeEG+Owp+LPrq52KIjeH+asqy7qiqrgzxLdtcxzIxkiY3dl/3gdpiDuDfMFOGQnuanUo=;24:K5aTJBira/CEGlqh8XnQA1GAs+ak3MvCfWNTodIxuJoUkgNBkeJTu+pod+9vMf5V0HYxoNmGN6OCNU8mRL9XUkNOp7uGQhlHZFo3SWsJ2K8=;7:g8lqkC7Nx+KY7sn+gm7aWhk6C18LryzL0cKz5bmEtY1DPn6NFMtNYcs0ZiuG4EndyMILBkv9MZ1oCiYUyueW9/1HaSWrFP24nj8dMgNlk2K82PtknAnOTR7QgXyD3Ediw/weLR314UPVAhEIO0zkfipNNyPsSJmFtX7TEa3mV2lBiHhigp+EtWWHlV5Fbp5n7Mrd4yi95oLmFV1GCSgGwvoXahcJwpEFQP56EEi/ppIJY6GP/5wdAjBpa3I7xveQ x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: ab4f8fd5-e6ef-4c37-1645-08d58156fe7a x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(48565401081)(5600026)(4604075)(3008032)(4534165)(4627221)(201703031133081)(201702281549075)(2017052603307)(7193020);SRVR:MW2PR2101MB0924; x-ms-traffictypediagnostic: MW2PR2101MB0924: 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)(8121501046)(5005006)(93006095)(93001095)(10201501046)(3231220)(944501244)(52105095)(3002001)(6055026)(61426038)(61427038)(6041288)(20161123562045)(20161123558120)(20161123564045)(20161123560045)(201703131423095)(201702281528075)(20161123555045)(201703061421075)(201703061406153)(6072148)(201708071742011);SRVR:MW2PR2101MB0924;BCL:0;PCL:0;RULEID:;SRVR:MW2PR2101MB0924; x-forefront-prvs: 0600F93FE1 x-forefront-antispam-report: SFV:NSPM;SFS:(10019020)(346002)(376002)(39860400002)(396003)(366004)(39380400002)(189003)(199004)(102836004)(2950100002)(10090500001)(6666003)(316002)(26005)(186003)(25786009)(2900100001)(2906002)(54906003)(22452003)(110136005)(97736004)(6506007)(59450400001)(7736002)(4326008)(305945005)(5250100002)(86362001)(2501003)(99286004)(68736007)(72206003)(53936002)(6436002)(6116002)(3846002)(5660300001)(66066001)(1076002)(76176011)(14454004)(36756003)(3660700001)(6486002)(86612001)(81156014)(8676002)(81166006)(10290500003)(6512007)(8936002)(3280700002)(478600001)(107886003)(106356001)(105586002)(22906009)(217873001);DIR:OUT;SFP:1102;SCL:1;SRVR:MW2PR2101MB0924;H:MW2PR2101MB1034.namprd21.prod.outlook.com;FPR:;SPF:None;PTR:InfoNoRecords;MX:1;A:1;LANG:en; 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: ab4f8fd5-e6ef-4c37-1645-08d58156fe7a X-MS-Exchange-CrossTenant-originalarrivaltime: 03 Mar 2018 22:29:19.5413 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW2PR2101MB0924 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 475a7a1bcfe0..4493be50fc6a 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -3391,9 +3391,20 @@ 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