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Wed, 24 Jun 2020 00:33:56 +0000 From: Damien Le Moal To: Luis Chamberlain , "axboe@kernel.dk" , "bvanassche@acm.org" , "ming.lei@redhat.com" , "martin.petersen@oracle.com" , "satyat@google.com" CC: "linux-block@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 1/2] block: add initial kdoc over the request_queue Thread-Topic: [PATCH 1/2] block: add initial kdoc over the request_queue Thread-Index: AQHWSaobgkrHkRgd/kyqGjQRHGO3LA== Date: Wed, 24 Jun 2020 00:33:56 +0000 Message-ID: References: <20200623220311.8033-1-mcgrof@kernel.org> <20200623220311.8033-2-mcgrof@kernel.org> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: kernel.org; dkim=none (message not signed) header.d=none;kernel.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: 8ea5e32b-81f0-4806-410e-08d817d6478b x-ms-traffictypediagnostic: CY4PR04MB0343: x-microsoft-antispam-prvs: wdcipoutbound: EOP-TRUE x-ms-oob-tlc-oobclassifiers: OLM:2201; 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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: wdc.com X-MS-Exchange-CrossTenant-Network-Message-Id: 8ea5e32b-81f0-4806-410e-08d817d6478b X-MS-Exchange-CrossTenant-originalarrivaltime: 24 Jun 2020 00:33:56.2204 (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: 0GtN7x9tHBfdIGfsHpNYdUyyBVFb6zm1hM9WdbhbTBc6EdN+XUuK0BJFNgP3PejH63q+00XYl0YMTXrlayBI6g== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY4PR04MB0343 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 2020/06/24 7:03, Luis Chamberlain wrote:=0A= > We start off with an initial description of the request_queue data=0A= > structure, followed by describing the purpose of the debugfs_mutex=0A= > debugfs_dir, and blk_trace.=0A= > =0A= > Suggested-by: Bart Van Assche =0A= > Signed-off-by: Luis Chamberlain =0A= > ---=0A= > include/linux/blkdev.h | 20 ++++++++++++++++++++=0A= > 1 file changed, 20 insertions(+)=0A= > =0A= > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h=0A= > index 70461b347169..ea319c2b0593 100644=0A= > --- a/include/linux/blkdev.h=0A= > +++ b/include/linux/blkdev.h=0A= > @@ -394,6 +394,26 @@ static inline int blkdev_zone_mgmt_ioctl(struct bloc= k_device *bdev,=0A= > =0A= > #endif /* CONFIG_BLK_DEV_ZONED */=0A= > =0A= > +/**=0A= > + * struct request_queue - block device driver request queue=0A= > + * @debugfs_mutex: used to protect access to the @debugfs_dir=0A= > + * @blk_trace: used by blktrace to keep track of setup / tracing=0A= > + * @debugfs_dir: directory created to place debugfs information. This is= always=0A= > + * created for make_request and request-based block drivers upon=0A= > + * initialization. blktrace requires for this directory to be created,= =0A= =0A= s/requires for/requires/ (may be, not sure of my English grammar on this on= e :))=0A= =0A= > + * and so it will be created on demand if its block driver type does not= =0A= > + * create it opon initialization.=0A= =0A= s/opon/upon/=0A= =0A= > + *=0A= > + * The request_queue is used to manage incoming block layer device drive= r=0A= > + * requests. We have three main type of block driver types which end up = making=0A= =0A= We have three main types of block drivers which...=0A= =0A= > + * use of the request_queue:=0A= > + *=0A= > + * o make_request block drivers (multiqueue)=0A= > + * o request-based block drivers=0A= =0A= Isn't this second one BIO based drivers, like device-mapper BIO targets ?= =0A= =0A= > + * o custom solutions such as scsi-generic=0A= =0A= The SG driver does not create a request queue, it uses the one of the scsi= =0A= device created by the scsi stack. Is this what you mean here ? Saying=0A= scsi-generic kind of implies sg driver.=0A= =0A= > + *=0A= > + * All partitions share the same request_queue data structure.=0A= > + */=0A= > struct request_queue {=0A= > struct request *last_merge;=0A= > struct elevator_queue *elevator;=0A= > =0A= =0A= =0A= -- =0A= Damien Le Moal=0A= Western Digital Research=0A=