[Devel] [PATCH hci-8.1 0/2] dm-qcow2, dm-ploop: do not merge discards with gaps

[Alexander Ivanov]

LGTM

On 11/9/26 16:36, Andrey Zhadchenko wrote:
> The block layer may merge non-contiguous discard bios into a single
> request when the queue allows more than one discard segment, and the
> stacking default for dm is max_discard_segments = USHRT_MAX.
>
> Both dm-qcow2 and dm-ploop handle a discard request as one contiguous
> range taken from blk_rq_pos() and blk_rq_bytes(). For a request built
> from bios [0, 512) and [1024, 1536) they discard [0, 1024), which hits
> sectors that were never asked to be discarded and misses part of the
> range that was.
>
> Set max_discard_segments to 1 in both targets so each discard request
> always describes a single contiguous range.
>
> https://virtuozzo.atlassian.net/browse/VSTOR-154159
>
> Andrey Zhadchenko (2):
>    dm-qcow2: set max discard segments to one
>    dm-ploop: set max discard segments to one
>
>   drivers/md/dm-ploop-target.c | 1 +
>   drivers/md/dm-qcow2-target.c | 1 +
>   2 files changed, 2 insertions(+)
>