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Ts'o" , Christoph Hellwig , "linux-ext4@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , Christoph Hellwig , Johannes Thumshirn , Naohiro Aota , Masato Suzuki Subject: Re: [PATCH] ext4: Fix deadlock on page reclaim Thread-Topic: [PATCH] ext4: Fix deadlock on page reclaim Thread-Index: AQHVQswib+fLuRINzEOhyZKScmS/IQ== Date: Wed, 31 Jul 2019 04:37:57 +0000 Message-ID: References: <20190725093358.30679-1-damien.lemoal@wdc.com> <20190725115442.GA15733@infradead.org> <20190726224423.GE7777@dread.disaster.area> <20190726225508.GA13729@mit.edu> <3D2360FA-AD48-48AE-B1CE-D1CF58C1B8AB@dilger.ca> <20190730234716.GY7689@dread.disaster.area> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: spf=none (sender IP is ) smtp.mailfrom=Damien.LeMoal@wdc.com; x-originating-ip: [199.255.47.11] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 4aa6f22d-9163-4553-fc90-08d71570dc95 x-ms-office365-filtering-ht: Tenant x-microsoft-antispam: BCL:0;PCL:0;RULEID:(2390118)(7020095)(4652040)(8989299)(5600148)(711020)(4605104)(1401327)(4618075)(4534185)(4627221)(201703031133081)(201702281549075)(8990200)(2017052603328)(7193020);SRVR:BN8PR04MB5761; x-ms-traffictypediagnostic: BN8PR04MB5761: x-microsoft-antispam-prvs: wdcipoutbound: EOP-TRUE x-ms-oob-tlc-oobclassifiers: OLM:8882; x-forefront-prvs: 011579F31F x-forefront-antispam-report: SFV:NSPM;SFS:(10019020)(4636009)(346002)(376002)(396003)(136003)(39860400002)(366004)(199004)(189003)(91956017)(2906002)(478600001)(81166006)(6916009)(66066001)(76176011)(256004)(53936002)(76116006)(33656002)(8676002)(7696005)(52536014)(4326008)(71200400001)(66946007)(55016002)(9686003)(486006)(5660300002)(71190400001)(25786009)(64756008)(66446008)(66476007)(3846002)(186003)(74316002)(446003)(6116002)(66556008)(476003)(68736007)(7736002)(8936002)(6436002)(81156014)(102836004)(86362001)(53546011)(305945005)(6246003)(316002)(6506007)(26005)(54906003)(14454004)(99286004)(229853002);DIR:OUT;SFP:1102;SCL:1;SRVR:BN8PR04MB5761;H:BN8PR04MB5812.namprd04.prod.outlook.com;FPR:;SPF:None;LANG:en;PTR:InfoNoRecords;A:1;MX:1; x-ms-exchange-senderadcheck: 1 x-microsoft-antispam-message-info: mGn7SXuibzkBAYvibYHu+TCpIb54xPt/ns+oimba8sibFuTaRahEqgHlpy9p0QhkqB6scv9n0AW2laj8qABlPThtsAgmELTI5gDD7KStwMWu55zo+WAqMIQ8+hi195Xs9IF6naPsfdE2saPcSiJ9gKlHDuECgjSdV5Cjj3LZMUsCsBE1RNiRcHC11pvUehGa5tIRSq60KFs/Mj8LOhhkH2NCPYhhxgebL7HTMI961I931o3crKJenGZWY7gwq76RwToyWjgFDzvK6ysd9XBfxYoxeMGzNQHnMBdM6UQVG/p4yXr0gp7yK8qEqu8gjLS5kWAL5+StvvpGBM0edUi61ShPnli7EVRepovHTbsgWmiapvFjJvrzGgeQS862QvMaccPr5d0Nr0/n++WaQC4bqksMmSLVGXc7cb9D3f84vQI= Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: wdc.com X-MS-Exchange-CrossTenant-Network-Message-Id: 4aa6f22d-9163-4553-fc90-08d71570dc95 X-MS-Exchange-CrossTenant-originalarrivaltime: 31 Jul 2019 04:37:57.6572 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: b61c8803-16f3-4c35-9b17-6f65f441df86 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: Damien.LeMoal@wdc.com X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN8PR04MB5761 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Dave,=0A= =0A= On 2019/07/31 8:48, Dave Chinner wrote:=0A= > On Tue, Jul 30, 2019 at 02:06:33AM +0000, Damien Le Moal wrote:=0A= >> If we had a pread_nofs()/pwrite_nofs(), that would work. Or we could def= ine a=0A= >> RWF_NORECLAIM flag for pwritev2()/preadv2(). This last one could actuall= y be the=0A= >> cleanest approach.=0A= > =0A= > Clean, yes, but I'm not sure we want to expose kernel memory reclaim=0A= > capabilities to userspace... It would be misleading, too, because we=0A= > still want to allow reclaim to occur, just not have reclaim recurse=0A= > into other filesystems....=0A= =0A= When I wrote RWF_NORECLAIM, I was really thinking of RWF_NOFSRECLAIM. So=0A= suppressing direct reclaim recursing into another FS rather than completely= =0A= disabling reclaim. Sorry for the confusion.=0A= =0A= Would this be better ? This is still application controlled, so debatable i= f=0A= control should be given. Most likely this would need to be limited to CAP_S= YS=0A= capable user processes (e.g. root processes).=0A= =0A= I still need to check on FUSE if anything at all along these lines exists t= here.=0A= I will dig.=0A= =0A= Best regards.=0A= =0A= -- =0A= Damien Le Moal=0A= Western Digital Research=0A=