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Thu, 8 Mar 2018 00:56:22 -0500 Received: from mail-sn1nam01on0117.outbound.protection.outlook.com ([104.47.32.117]:16747 "EHLO NAM01-SN1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S966031AbeCHFDc (ORCPT ); Thu, 8 Mar 2018 00:03:32 -0500 From: Sasha Levin To: "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" CC: Trond Myklebust , Sasha Levin Subject: [PATCH AUTOSEL for 4.9 140/190] pNFS: Fix a deadlock when coalescing writes and returning the layout Thread-Topic: [PATCH AUTOSEL for 4.9 140/190] pNFS: Fix a deadlock when coalescing writes and returning the layout Thread-Index: AQHTtppL1tp0wOts4UmRJk77IvA1eg== Date: Thu, 8 Mar 2018 04:59:53 +0000 Message-ID: <20180308045810.8041-140-alexander.levin@microsoft.com> References: <20180308045810.8041-1-alexander.levin@microsoft.com> In-Reply-To: <20180308045810.8041-1-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;DM5PR2101MB1013;7:7wkmLQeGBN3XeRdhzj2ZlxGyyqsgWJhB5lLgMvU9zCcVyzm4V1Ya7OsLvnfmu2YvV5olEgtKCZbhAk9Okhoe7TZd+zWxnsX2Mtn+iIACacRXZvxoYjDxgBuPrVrBZducuo0ShJ03LEW1C0VwnWNBAJEJgtTgXlZiH7BLar/jGq8sifyxpkn6A7gH0/ZTcyyYKlOBzR5DKkFyecToCLOVtJT/U238CjLTXSLAyredQz4zb1br2+goqgj11MuxpLuW;20:TbwZ7BCRsZJsVcS7GRLnn9wyB/6ZUBNwuGojZx/K9aN3l6nYPY3hF1/6ZijAKhhfZInd/nba5++XtDpzDjf4DCULNxXMzavsd9VFV3PZiuOpOzhEGQyCVvHqGqkp4PAHVJu21ncYDz2+h5oFMm5jndhBOA4nIKBgQ7loBpjSOnk= x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: 8f10ab73-01b1-42eb-abbe-08d584b1e86f x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(48565401081)(5600026)(4604075)(3008032)(4534165)(4627221)(201703031133081)(201702281549075)(2017052603328)(7193020);SRVR:DM5PR2101MB1013; 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x-microsoft-antispam-message-info: dajPvQfMMg7lW+nUvErht120Rt4VLsOcr98Aufw8qGaSMLwysmFc6KhMlFL46T0BTSG8xHaLyzTadZGPLnO7wg8ACllR4sqyFDv+BWDM1lSErLthaLrcF8TVfs4ty4llOszMFCZWa4FlgCxMZKt+8KKaCmU74pIycQFPblA0QdaGH7wmw9O3ilkXITQmb4IbiLv8XEoVM4ZHm1CCqG86fkdgFl+kP1vwyc6mL7+3L2ZdZtmp1ZsgRfsj7lyOdnATeWNOydEbbDK82SYicB0Vozd099gV2LrtRrvL0dILFEub/4v4YTRinifz9HdVTkMfh9Gisf0sJ8lBu8w+UXibtQ== 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: 8f10ab73-01b1-42eb-abbe-08d584b1e86f X-MS-Exchange-CrossTenant-originalarrivaltime: 08 Mar 2018 04:59:53.5988 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR2101MB1013 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: Trond Myklebust [ Upstream commit 61f454e30c18a28924e96be12592c0d5e24bcc81 ] Consider the following deadlock: Process P1 Process P2 Process P3 =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D lock_page(page) lseg =3D pnfs_update_layout(inode) lo =3D NFS_I(inode)->layout pnfs_error_mark_layout_for_return(lo) lock_page(page) lseg =3D pnfs_update_layout(inode) In this scenario, - P1 has declared the layout to be in error, but P2 holds a reference to a layout segment on that inode, so the layoutreturn is deferred. - P2 is waiting for a page lock held by P3. - P3 is asking for a new layout segment, but is blocked waiting for the layoutreturn. The fix is to ensure that pnfs_error_mark_layout_for_return() does not set the NFS_LAYOUT_RETURN flag, which blocks P3. Instead, we allow the latter to call LAYOUTGET so that it can make progress and unblock P2. Signed-off-by: Trond Myklebust Signed-off-by: Sasha Levin --- fs/nfs/pnfs.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c index e9a697e9d292..0e008db16b16 100644 --- a/fs/nfs/pnfs.c +++ b/fs/nfs/pnfs.c @@ -1953,8 +1953,6 @@ void pnfs_error_mark_layout_for_return(struct inode *= inode, =20 spin_lock(&inode->i_lock); pnfs_set_plh_return_info(lo, range.iomode, 0); - /* Block LAYOUTGET */ - set_bit(NFS_LAYOUT_RETURN, &lo->plh_flags); /* * mark all matching lsegs so that we are sure to have no live * segments at hand when sending layoutreturn. See pnfs_put_lseg() --=20 2.14.1