linux-kernel - [PATCH v6 0/6] block/md/dm: set chunk_sectors from stacked dev stripe size

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Message-ID: <20250711080929.3091196-1-john.g.garry@oracle.com>
Date: Fri, 11 Jul 2025 08:09:23 +0000
From: John Garry <john.g.garry@...cle.com>
To: agk@...hat.com, snitzer@...nel.org, mpatocka@...hat.com, song@...nel.org,
        yukuai3@...wei.com, hch@....de, nilay@...ux.ibm.com, axboe@...nel.dk,
        cem@...nel.org
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, John Garry <john.g.garry@...cle.com>
Subject: [PATCH v6 0/6] block/md/dm: set chunk_sectors from stacked dev stripe size

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 .

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!)

Differences to v3:
- relocate max_pow_of_two_factor() to common header and rework (Mikulas)
- cater for overflow from chunk sectors (Mikulas)

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   | 61 ++++++++++++++++++++++++++----------------
 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, 55 insertions(+), 28 deletions(-)

-- 
2.43.5