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]>
next prev parent 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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