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Mon, 18 May 2020 01:12:48 +0000 From: Damien Le Moal To: Bart Van Assche , Jens Axboe CC: "linux-block@vger.kernel.org" , Christoph Hellwig , Ming Lei , Chaitanya Kulkarni , Alexander Potapenko Subject: Re: [PATCH 5/5] null_blk: Zero-initialize read buffers in non-memory-backed mode Thread-Topic: [PATCH 5/5] null_blk: Zero-initialize read buffers in non-memory-backed mode Thread-Index: AQHWKxeutW6PgxRL9Ea9BZV4XxYt6g== Date: Mon, 18 May 2020 01:12:48 +0000 Message-ID: References: <20200516001914.17138-1-bvanassche@acm.org> <20200516001914.17138-6-bvanassche@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: 7d24a8ab-f53d-43fb-2b44-08d7fac8947e x-ms-traffictypediagnostic: BY5PR04MB6293: x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: wdcipoutbound: EOP-TRUE x-ms-oob-tlc-oobclassifiers: OLM:5797; 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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: 7d24a8ab-f53d-43fb-2b44-08d7fac8947e X-MS-Exchange-CrossTenant-originalarrivaltime: 18 May 2020 01:12:48.6161 (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: qieD2e/fYNF2B6SASHPjfN6UXrGYgbaEg+NLG+8l6F8UE/j/z/LQZ5UD+bW3l9l4OOFcN1c+oB2wjLu0Fr8gXg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY5PR04MB6293 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 2020/05/16 9:19, Bart Van Assche wrote:=0A= > This patch suppresses an uninteresting KMSAN complaint without affecting= =0A= > performance of the null_blk driver if CONFIG_KMSAN is disabled.=0A= > =0A= > Cc: Christoph Hellwig =0A= > Cc: Ming Lei =0A= > Cc: Damien Le Moal =0A= > Cc: Chaitanya Kulkarni =0A= > Cc: Alexander Potapenko =0A= > Reported-by: Alexander Potapenko =0A= > Signed-off-by: Bart Van Assche =0A= > ---=0A= > drivers/block/null_blk_main.c | 30 ++++++++++++++++++++++++++++++=0A= > 1 file changed, 30 insertions(+)=0A= > =0A= > diff --git a/drivers/block/null_blk_main.c b/drivers/block/null_blk_main.= c=0A= > index 06f5761fccb6..df1e144eeaa4 100644=0A= > --- a/drivers/block/null_blk_main.c=0A= > +++ b/drivers/block/null_blk_main.c=0A= > @@ -1250,8 +1250,38 @@ static inline blk_status_t null_handle_memory_back= ed(struct nullb_cmd *cmd,=0A= > return errno_to_blk_status(err);=0A= > }=0A= > =0A= > +static void nullb_zero_rq_data_buffer(const struct request *rq)=0A= > +{=0A= > + struct req_iterator iter;=0A= > + struct bio_vec bvec;=0A= > +=0A= > + rq_for_each_bvec(bvec, rq, iter)=0A= > + zero_fill_bvec(&bvec);=0A= > +}=0A= > +=0A= > +static void nullb_zero_read_cmd_buffer(struct nullb_cmd *cmd)=0A= > +{=0A= > + struct nullb_device *dev =3D cmd->nq->dev;=0A= > +=0A= > + if (dev->queue_mode =3D=3D NULL_Q_BIO && bio_op(cmd->bio) =3D=3D REQ_OP= _READ)=0A= > + zero_fill_bio(cmd->bio);=0A= > + else if (req_op(cmd->rq) =3D=3D REQ_OP_READ)=0A= > + nullb_zero_rq_data_buffer(cmd->rq);=0A= > +}=0A= =0A= Shouldn't the definition of these two functions be under a "#ifdef CONFIG_K= MSAN" ?=0A= =0A= > +=0A= > +/* Complete a request. Only called if dev->memory_backed =3D=3D 0. */=0A= > static inline void nullb_complete_cmd(struct nullb_cmd *cmd)=0A= > {=0A= > + /*=0A= > + * Since root privileges are required to configure the null_blk=0A= > + * driver, it is fine that this driver does not initialize the=0A= > + * data buffers of read commands. Zero-initialize these buffers=0A= > + * anyway if KMSAN is enabled to prevent that KMSAN complains=0A= > + * about null_blk not initializing read data buffers.=0A= > + */=0A= > + if (IS_ENABLED(CONFIG_KMSAN))=0A= > + nullb_zero_read_cmd_buffer(cmd);=0A= > +=0A= > /* Complete IO by inline, softirq or timer */=0A= > switch (cmd->nq->dev->irqmode) {=0A= > case NULL_IRQ_SOFTIRQ:=0A= > =0A= =0A= =0A= -- =0A= Damien Le Moal=0A= Western Digital Research=0A=