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Tue, 12 May 2020 01:42:06 +0000 From: Damien Le Moal To: Bart Van Assche , Alexander Potapenko CC: Chaitanya Kulkarni , Jens Axboe , "linux-block@vger.kernel.org" , Willem de Bruijn , Dmitriy Vyukov Subject: Re: null_handle_cmd() doesn't initialize data when reading Thread-Topic: null_handle_cmd() doesn't initialize data when reading Thread-Index: AQHVm53GT+JHqNkf70+buklNLC0a/A== Date: Tue, 12 May 2020 01:42:06 +0000 Message-ID: References: <277579c9-9e33-89ea-bfcd-bc14a543726c@acm.org> <55674c05-37dc-0646-af78-db4c3b112683@acm.org> <1e455c9f-4908-f476-f674-c0c920c17f9c@acm.org> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: acm.org; dkim=none (message not signed) header.d=none;acm.org; dmarc=none action=none header.from=wdc.com; x-originating-ip: [129.253.182.57] x-ms-publictraffictype: Email x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: 76028546-3672-4d31-cf55-08d7f615add0 x-ms-traffictypediagnostic: BY5PR04MB6294: x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: wdcipoutbound: EOP-TRUE x-ms-oob-tlc-oobclassifiers: OLM:10000; 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x-ms-exchange-antispam-messagedata: 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 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: 76028546-3672-4d31-cf55-08d7f615add0 X-MS-Exchange-CrossTenant-originalarrivaltime: 12 May 2020 01:42:06.5829 (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: jUSdGmo3pJQ1wj9WRpE4rLsRv2s0nwhHdth2FfwfSwUca0yA5GwiSh+85fxVAR/RPZ/XeKzvaM3MX6lX35CeCg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY5PR04MB6294 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 2020/05/12 10:25, Bart Van Assche wrote:=0A= > On 2020-05-11 16:18, Bart Van Assche wrote:=0A= >> Anyway, can you give the patch below a try?=0A= > =0A= > The patch in my previous email handles MQ mode but not bio mode. The=0A= > attached patch should handle both.=0A= > =0A= > Thanks,=0A= > =0A= > Bart.=0A= > =0A= =0A= Bart,=0A= =0A= The patch looks good to me. However, I have one concern regarding the=0A= performance impact of this. When nullblk is used to benchmark the block IO = stack=0A= overhead, doing this zeroing unconditionally will likely significantly impa= ct=0A= measured performance. So may be this zeroing feature should be driven by a= =0A= modprobe/configfs option ? Doing so, we can keep it off by default, preserv= ing=0A= performance, and turn it on when needed as in Alexander use case.=0A= =0A= Thoughts ?=0A= =0A= -- =0A= Damien Le Moal=0A= Western Digital Research=0A=