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From: Christoph Hellwig <hch@lst.de>
To: John Garry <john.g.garry@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>,
	"Darrick J. Wong" <djwong@kernel.org>,
	axboe@kernel.dk, kbusch@kernel.org, sagi@grimberg.me,
	jejb@linux.ibm.com, martin.petersen@oracle.com,
	viro@zeniv.linux.org.uk, brauner@kernel.org, dchinner@redhat.com,
	jack@suse.cz, linux-block@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
	linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	tytso@mit.edu, jbongio@google.com, linux-scsi@vger.kernel.org,
	ming.lei@redhat.com, jaswin@linux.ibm.com, bvanassche@acm.org
Subject: Re: [PATCH v2 00/16] block atomic writes
Date: Wed, 17 Jan 2024 16:02:00 +0100	[thread overview]
Message-ID: <20240117150200.GA30112@lst.de> (raw)
In-Reply-To: <6135eab3-50ce-4669-a692-b4221773bb20@oracle.com>

On Tue, Jan 16, 2024 at 11:35:47AM +0000, John Garry wrote:
> As such, we then need to set atomic write unit max = min(queue max 
> segments, BIO_MAX_VECS) * LBS. That would mean atomic write unit max 256 * 
> 512 = 128K (for 512B LBS). For a DMA controller of max segments 64, for 
> example, then we would have 32K. These seem too low.

I don't see how this would work if support multiple sectors.

>
> Alternative I'm thinking that we should just limit to 1x iovec always, and 
> then atomic write unit max = (min(queue max segments, BIO_MAX_VECS) - 1) * 
> PAGE_SIZE [ignoring first/last iovec contents]. It also makes support for 
> non-enterprise NVMe drives more straightforward. If someone wants, they can 
> introduce support for multi-iovec later, but it would prob require some 
> more iovec length/alignment rules.

Supporting just a single iovec initially is fine with me, as extending
that is pretty easy.  Just talk to your potential users that they can
live with it.

I'd probably still advertise the limits even if it currently always is 1.



  reply	other threads:[~2024-01-17 15:02 UTC|newest]

Thread overview: 73+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-12-12 11:08 [PATCH v2 00/16] block atomic writes John Garry
2023-12-12 11:08 ` [PATCH v2 01/16] block: Add atomic write operations to request_queue limits John Garry
2023-12-13  1:25   ` Ming Lei
2023-12-13  9:13     ` John Garry
2023-12-13 12:28       ` Ming Lei
2023-12-13 19:01         ` John Garry
2023-12-14  4:38         ` Martin K. Petersen
2023-12-14 13:46           ` Ming Lei
2023-12-14  4:34     ` Martin K. Petersen
2023-12-14 16:12     ` Christoph Hellwig
2023-12-12 11:08 ` [PATCH v2 02/16] block: Limit atomic writes according to bio and queue limits John Garry
2023-12-12 11:08 ` [PATCH v2 03/16] fs/bdev: Add atomic write support info to statx John Garry
2023-12-13 10:24   ` Jan Kara
2023-12-13 11:02     ` John Garry
2023-12-12 11:08 ` [PATCH v2 04/16] fs: Increase fmode_t size John Garry
2023-12-13 11:20   ` Jan Kara
2023-12-13 13:03     ` John Garry
2023-12-13 13:02   ` Christian Brauner
2023-12-13 13:15     ` John Garry
2023-12-13 16:03     ` Christoph Hellwig
2023-12-14  8:56       ` John Garry
2023-12-12 11:08 ` [PATCH v2 05/16] fs: Add RWF_ATOMIC and IOCB_ATOMIC flags for atomic write support John Garry
2023-12-13 13:31   ` Al Viro
2023-12-13 16:02     ` John Garry
2024-01-22  8:29   ` John Garry
2023-12-12 11:08 ` [PATCH v2 06/16] block: Add REQ_ATOMIC flag John Garry
2023-12-12 11:08 ` [PATCH v2 07/16] block: Pass blk_queue_get_max_sectors() a request pointer John Garry
2023-12-12 11:08 ` [PATCH v2 08/16] block: Limit atomic write IO size according to atomic_write_max_sectors John Garry
2023-12-15  2:27   ` Ming Lei
2023-12-15 13:55     ` John Garry
2023-12-12 11:08 ` [PATCH v2 09/16] block: Error an attempt to split an atomic write bio John Garry
2023-12-12 11:08 ` [PATCH v2 10/16] block: Add checks to merging of atomic writes John Garry
2023-12-12 11:08 ` [PATCH v2 11/16] block: Add fops atomic write support John Garry
2023-12-12 11:08 ` [PATCH v2 12/16] scsi: sd: Support reading atomic write properties from block limits VPD John Garry
2023-12-12 11:08 ` [PATCH v2 13/16] scsi: sd: Add WRITE_ATOMIC_16 support John Garry
2023-12-12 11:08 ` [PATCH v2 14/16] scsi: scsi_debug: Atomic write support John Garry
2023-12-12 11:08 ` [PATCH v2 15/16] nvme: Support atomic writes John Garry
2023-12-12 11:08 ` [PATCH v2 16/16] nvme: Ensure atomic writes will be executed atomically John Garry
2023-12-12 16:32 ` [PATCH v2 00/16] block atomic writes Christoph Hellwig
2023-12-13  9:32   ` John Garry
2023-12-13 15:44     ` Christoph Hellwig
2023-12-13 16:27       ` John Garry
2023-12-14 14:37         ` Christoph Hellwig
2023-12-14 15:46           ` John Garry
2023-12-18 22:50           ` Keith Busch
2023-12-19  5:14         ` Darrick J. Wong
2023-12-19  5:21           ` Christoph Hellwig
2023-12-19 12:41             ` John Garry
2023-12-19 15:17               ` Christoph Hellwig
2023-12-19 16:53                 ` John Garry
2023-12-21  6:50                   ` Christoph Hellwig
2023-12-21  9:49                     ` John Garry
2023-12-21 12:19                       ` Christoph Hellwig
2023-12-21 12:48                         ` John Garry
2023-12-21 12:57                           ` Christoph Hellwig
2023-12-21 13:18                             ` John Garry
2023-12-21 13:22                               ` Christoph Hellwig
2023-12-21 13:56                                 ` John Garry
2024-01-16 11:35                                 ` John Garry
2024-01-17 15:02                                   ` Christoph Hellwig [this message]
2024-01-17 16:16                                     ` John Garry
2024-01-09  9:55                     ` John Garry
2024-01-09 16:02                       ` Christoph Hellwig
2024-01-09 16:52                         ` John Garry
2024-01-09 23:04                       ` Dave Chinner
2024-01-10  8:55                         ` John Garry
2024-01-10  9:19                         ` Christoph Hellwig
2024-01-11  1:40                           ` Darrick J. Wong
2024-01-11  5:02                             ` Christoph Hellwig
2024-01-11  9:55                               ` John Garry
2024-01-11 14:45                                 ` Christoph Hellwig
2024-01-11 16:11                                   ` John Garry
2024-01-11 16:15                                     ` Christoph Hellwig

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