linux-kernel - Re: [PATCH v6 0/6] block/md/dm: set chunk

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Message-ID: <f80713ec-fef1-4a33-b7bf-820ca69cb6ce@kernel.org>
Date: Fri, 11 Jul 2025 17:44:26 +0900
From: Damien Le Moal <dlemoal@...nel.org>
To: John Garry <john.g.garry@...cle.com>, 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
Subject: Re: [PATCH v6 0/6] block/md/dm: set chunk_sectors from stacked dev
 stripe size

On 7/11/25 5:09 PM, John Garry wrote:
> 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.

Hmm... chunk_sectors for a zoned device is the zone size. So is this all safe
if we are dealing with a zoned block device that also supports atomic writes ?
Not that I know of any such device, but better be safe, so maybe for now do not
enable atomic write support on zoned devices ?



-- 
Damien Le Moal
Western Digital Research