linux-kernel - Re: [PATCH v7 0/6] block/md/dm: set chunk

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Message-ID: <b14be10b-cf50-4190-a03b-ad302a241e74@oracle.com>
Date: Thu, 17 Jul 2025 09:00:00 +0100
From: John Garry <john.g.garry@...cle.com>
To: axboe@...nel.dk
Cc: dm-devel@...ts.linux.dev, linux-kernel@...r.kernel.org,
        linux-raid@...r.kernel.org, linux-block@...r.kernel.org,
        ojaswin@...ux.ibm.com, martin.petersen@...cle.com,
        akpm@...ux-foundation.org, linux-xfs@...r.kernel.org,
        djwong@...nel.org, dlemoal@...nel.org, cem@...nel.org,
        nilay@...ux.ibm.com, agk@...hat.com, snitzer@...nel.org,
        song@...nel.org, yukuai3@...wei.com, hch@....de, mpatocka@...hat.com
Subject: Re: [PATCH v7 0/6] block/md/dm: set chunk_sectors from stacked dev
 stripe size

On 11/07/2025 11:52, John Garry wrote:

Hi Jens,

Can you please consider picking up these changes on the block tree? They 
fix real issues which we encountered.

Thanks,
John

> This value in io_min is used to configure any atomic write limit for the
> stacked device. The idea is that the atomic write unit max is a
> power-of-2 factor of the stripe size, and the stripe size is available
> in io_min.
> 
> Using io_min causes issues, as:
> a. it may be mutated
> b. the check for io_min being set for determining if we are dealing with
> a striped device is hard to get right, as reported in [0].
> 
> This series now sets chunk_sectors limit to share stripe size.
> 
> [0] https://lore.kernel.org/linux-block/888f3b1d-7817-4007-b3b3-1a2ea04df771@linux.ibm.com/T/#mecca17129f72811137d3c2f1e477634e77f06781
> 
> Based on 8b428f42f3edf nbd: fix lockdep deadlock warning
> 
> This series fixes issues for v6.16, but it's prob better to have this in
> v6.17 .
> 
> Difference to v6:
> - do comparison in sectors in 2/6
> 
> Differences to v5:
> - Neaten code in blk_validate_atomic_write_limits() (Jens)
> 
> Differences to v4:
> - Use check_shl_overflow() (Nilay)
> - Use long long in for chunk bytes in 2/6
> - Add tags from Nilay (thanks!)
> 
> John Garry (6):
>    ilog2: add max_pow_of_two_factor()
>    block: sanitize chunk_sectors for atomic write limits
>    md/raid0: set chunk_sectors limit
>    md/raid10: set chunk_sectors limit
>    dm-stripe: limit chunk_sectors to the stripe size
>    block: use chunk_sectors when evaluating stacked atomic write limits
> 
>   block/blk-settings.c   | 62 ++++++++++++++++++++++++++----------------
>   drivers/md/dm-stripe.c |  1 +
>   drivers/md/raid0.c     |  1 +
>   drivers/md/raid10.c    |  1 +
>   fs/xfs/xfs_mount.c     |  5 ----
>   include/linux/log2.h   | 14 ++++++++++
>   6 files changed, 56 insertions(+), 28 deletions(-)
>