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Sun, 8 Apr 2018 20:17:50 -0400 From: Sasha Levin To: "stable@vger.kernel.org" , "linux-kernel@vger.kernel.org" CC: Ming Lei , Mike Snitzer , Sasha Levin Subject: [PATCH AUTOSEL for 4.15 037/189] dm mpath: return DM_MAPIO_REQUEUE on blk-mq rq allocation failure Thread-Topic: [PATCH AUTOSEL for 4.15 037/189] dm mpath: return DM_MAPIO_REQUEUE on blk-mq rq allocation failure Thread-Index: AQHTz5gdzpIHyS8FGUiNk6hfOHmWDQ== Date: Mon, 9 Apr 2018 00:17:15 +0000 Message-ID: <20180409001637.162453-37-alexander.levin@microsoft.com> References: <20180409001637.162453-1-alexander.levin@microsoft.com> In-Reply-To: <20180409001637.162453-1-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;DM5PR2101MB1048;7:1AuiRWL/iayaC2bxA6N/JqpsbU4pC795ZmOjUd6L/hvAjAegeVw0LKAivFznyJQ5j8hnLmUA8W6tx2RMr/Qj+bBF9n2UFEDE8OZQHAPRH2RnrSWEknj13pEUAS8glQvqPkIeoG/Rj8PuWXXdVgO9m0KG13VWSFGi/X0n3hs4JO9ev7PaLVyq0QbSOWoKs7mkIpFM41ulH5S6Xv0Ur5wszODuHGP/dYq5DOnhjBal4DRUtyR7prbNTD/xjmB9t2vK;20:nTzZeDYBH9s8Zt5NM/odm4JGk2bPlvpnlDtxhrtfeHP3Sa2iS7WPhq93lrfGwiyzZMnUdv5PPZk8gH0JW9CiffnVMlwrKJhDIax1cGx9aEJB9aC2+A3I62X59eFG3YqiOzvu9APeXBKrYaCs5qF4SNKgdHEAFZsylifyPGuKdKk= x-ms-office365-filtering-ht: Tenant X-MS-Office365-Filtering-Correlation-Id: a1a21865-ffd9-4c12-c1d2-08d59daf50da x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(48565401081)(5600026)(4604075)(3008032)(4534165)(4627221)(201703031133081)(201702281549075)(2017052603328)(7193020);SRVR:DM5PR2101MB1048; 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x-microsoft-antispam-message-info: 8mrZZC0+y/5V1exkh/lgkWn9ZqrbvU56OggSNSVK/2p++32xqQB5CIjqJKaEoaN6SPuUzryXJ9O1Ph00ZzgDChFdkqSd4DW5dvBWgr1GlfsNg561bEP5gmWBAFEFzfpCLX2PT78qKcUUfGe6ooKyxqoi3Rlg1rXwUxX4+CltfSYzcR/pYGItuklESDf9KFd+TrVWGXwsR6dpZCn1hAyTLnpGXyo2HfQ5QKIONJMArAvvHL104qYuDKurA83KktroqIcgdU8VGmii+zA+8Yk0kbYP9m5fqgkomjHeU5QPU2NhpmqcrCUxEhFrxaZEMK8Q3am3NbJrnH1SwreiQ21LDoeg2eL36h0LeYdqDSdqdWWSkSBZ74gz2lsBF4bzMAcnb9uS6v5epZxCczoErAeN0c4Ad1DAI9XpYTJnNNaIkP4= 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: a1a21865-ffd9-4c12-c1d2-08d59daf50da X-MS-Exchange-CrossTenant-originalarrivaltime: 09 Apr 2018 00:17:15.4641 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR2101MB1048 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: Ming Lei [ Upstream commit 050af08ffb1b62af69196d61c22a0755f9a3cdbd ] blk-mq will rerun queue via RESTART or dispatch wake after one request is completed, so not necessary to wait random time for requeuing, we should trust blk-mq to do it. More importantly, we need to return BLK_STS_RESOURCE to blk-mq so that dequeuing from the I/O scheduler can be stopped, this results in improved I/O merging. Signed-off-by: Ming Lei Signed-off-by: Mike Snitzer Signed-off-by: Sasha Levin --- drivers/md/dm-mpath.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c index 025e033ecb78..a3223c8fbaac 100644 --- a/drivers/md/dm-mpath.c +++ b/drivers/md/dm-mpath.c @@ -534,8 +534,20 @@ static int multipath_clone_and_map(struct dm_target *t= i, struct request *rq, if (queue_dying) { atomic_inc(&m->pg_init_in_progress); activate_or_offline_path(pgpath); + return DM_MAPIO_DELAY_REQUEUE; } - return DM_MAPIO_DELAY_REQUEUE; + + /* + * blk-mq's SCHED_RESTART can cover this requeue, so we + * needn't deal with it by DELAY_REQUEUE. More importantly, + * we have to return DM_MAPIO_REQUEUE so that blk-mq can + * get the queue busy feedback (via BLK_STS_RESOURCE), + * otherwise I/O merging can suffer. + */ + if (q->mq_ops) + return DM_MAPIO_REQUEUE; + else + return DM_MAPIO_DELAY_REQUEUE; } clone->bio =3D clone->biotail =3D NULL; clone->rq_disk =3D bdev->bd_disk; --=20 2.15.1