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From: Keith Busch <[email protected]>
To: John Garry <[email protected]>
Cc: [email protected], [email protected], [email protected],
	[email protected], [email protected],
	[email protected], [email protected], [email protected],
	[email protected], [email protected], [email protected],
	[email protected], [email protected],
	[email protected], [email protected], [email protected],
	[email protected], [email protected],
	[email protected], [email protected],
	[email protected], [email protected],
	[email protected], Alan Adamson <[email protected]>
Subject: Re: [PATCH v4 10/11] nvme: Atomic write support
Date: Mon, 19 Feb 2024 12:21:14 -0700	[thread overview]
Message-ID: <ZdOqKr6Js_nlobh5@kbusch-mbp> (raw)
In-Reply-To: <[email protected]>

On Mon, Feb 19, 2024 at 01:01:08PM +0000, John Garry wrote:
> From: Alan Adamson <[email protected]>
> 
> Add support to set block layer request_queue atomic write limits. The
> limits will be derived from either the namespace or controller atomic
> parameters.
> 
> NVMe atomic-related parameters are grouped into "normal" and "power-fail"
> (or PF) class of parameter. For atomic write support, only PF parameters
> are of interest. The "normal" parameters are concerned with racing reads
> and writes (which also applies to PF). See NVM Command Set Specification
> Revision 1.0d section 2.1.4 for reference.
> 
> Whether to use per namespace or controller atomic parameters is decided by
> NSFEAT bit 1 - see Figure 97: Identify - Identify Namespace Data Structure,
> #NVM Command Set.
> 
> NVMe namespaces may define an atomic boundary, whereby no atomic guarantees
> are provided for a write which straddles this per-lba space boundary. The
> block layer merging policy is such that no merges may occur in which the
> resultant request would straddle such a boundary.
> 
> Unlike SCSI, NVMe specifies no granularity or alignment rules. In addition,
> again unlike SCSI, there is no dedicated atomic write command - a write
> which adheres to the atomic size limit and boundary is implicitly atomic.
> 
> If NSFEAT bit 1 is set, the following parameters are of interest:
> - NAWUPF (Namespace Atomic Write Unit Power Fail)
> - NABSPF (Namespace Atomic Boundary Size Power Fail)
> - NABO (Namespace Atomic Boundary Offset)
> 
> and we set request_queue limits as follows:
> - atomic_write_unit_max = rounddown_pow_of_two(NAWUPF)
> - atomic_write_max_bytes = NAWUPF
> - atomic_write_boundary = NABSPF
> 
> If in the unlikely scenario that NABO is non-zero, then atomic writes will
> not be supported at all as dealing with this adds extra complexity. This
> policy may change in future.
> 
> In all cases, atomic_write_unit_min is set to the logical block size.
> 
> If NSFEAT bit 1 is unset, the following parameter is of interest:
> - AWUPF (Atomic Write Unit Power Fail)
> 
> and we set request_queue limits as follows:
> - atomic_write_unit_max = rounddown_pow_of_two(AWUPF)
> - atomic_write_max_bytes = AWUPF
> - atomic_write_boundary = 0
> 
> The block layer requires that the atomic_write_boundary value is a
> power-of-2. However, it is really only required that atomic_write_boundary
> be a multiple of atomic_write_unit_max. As such, if NABSPF were not a
> power-of-2, atomic_write_unit_max could be reduced such that it was
> divisible into NABSPF. However, this complexity will not be yet supported.
> 
> A helper function, nvme_valid_atomic_write(), is also added for the
> submission path to verify that a request has been submitted to the driver
> will actually be executed atomically.

Maybe patch 11 should be folded into this one. No bigged, the series as
a whole looks good.

Reviewed-by: Keith Busch <[email protected]>

  reply	other threads:[~2024-02-19 19:21 UTC|newest]

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-02-19 13:00 [PATCH v4 00/11] block atomic writes John Garry
2024-02-19 13:00 ` [PATCH v4 01/11] block: Pass blk_queue_get_max_sectors() a request pointer John Garry
2024-02-19 18:57   ` Keith Busch
2024-02-19 13:01 ` [PATCH v4 02/11] block: Call blkdev_dio_unaligned() from blkdev_direct_IO() John Garry
2024-02-19 18:57   ` Keith Busch
2024-02-20  8:31     ` John Garry
2024-02-20  6:54   ` Christoph Hellwig
2024-02-19 13:01 ` [PATCH v4 03/11] fs: Initial atomic write support John Garry
2024-02-19 19:16   ` David Sterba
2024-02-20  8:13     ` John Garry
2024-02-19 22:44   ` Dave Chinner
2024-02-20  9:52     ` John Garry
2024-02-24 18:16   ` Ritesh Harjani
2024-02-24 18:20     ` Ritesh Harjani
2024-02-26  8:58       ` John Garry
2024-02-26  9:13         ` Ritesh Harjani
2024-02-26  9:46           ` John Garry
2024-02-26  8:51     ` John Garry
2024-02-19 13:01 ` [PATCH v4 04/11] fs: Add initial atomic write support info to statx John Garry
2024-02-19 22:28   ` Dave Chinner
2024-02-20  9:40     ` John Garry
2024-02-20  8:20   ` Christoph Hellwig
2024-02-20  9:01     ` John Garry
2024-02-24 18:46   ` Ritesh Harjani
2024-02-26  9:07     ` John Garry
2024-02-19 13:01 ` [PATCH v4 05/11] block: Add core atomic write support John Garry
2024-02-19 22:58   ` Dave Chinner
2024-02-20  8:22     ` Christoph Hellwig
2024-02-20 10:01     ` John Garry
2024-02-25 12:09   ` Ritesh Harjani
2024-02-25 12:21     ` Ritesh Harjani
2024-02-26  9:23     ` John Garry
2024-02-19 13:01 ` [PATCH v4 06/11] block: Add atomic write support for statx John Garry
2024-02-20  8:29   ` Christoph Hellwig
2024-02-20  9:35     ` John Garry
2024-02-25 14:20   ` Ritesh Harjani
2024-02-26  9:36     ` John Garry
2024-02-19 13:01 ` [PATCH v4 07/11] block: Add fops atomic write support John Garry
2024-02-25 14:46   ` Ritesh Harjani
2024-02-26  9:46     ` John Garry
2024-02-19 13:01 ` [PATCH v4 08/11] scsi: sd: Atomic " John Garry
2024-02-19 13:01 ` [PATCH v4 09/11] scsi: scsi_debug: " John Garry
2024-02-20  7:12   ` Ojaswin Mujoo
2024-02-20  9:01     ` John Garry
2024-02-19 13:01 ` [PATCH v4 10/11] nvme: " John Garry
2024-02-19 19:21   ` Keith Busch [this message]
2024-02-20  6:55     ` Christoph Hellwig
2024-02-20  8:19       ` John Garry
2024-02-20  8:31   ` Christoph Hellwig
2024-02-20  8:50     ` John Garry
2024-02-19 13:01 ` [PATCH v4 11/11] nvme: Ensure atomic writes will be executed atomically John Garry

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