From: no-reply@sashiko.virtuozzo.com
To: den@virtuozzo.com, Alexander Ivanov <alexander.ivanov@virtuozzo.com>
Cc: devel@openvz.org
Subject: Re: [Devel] [PATCH hci-8.1] drivers/md/dm-qcow2: truncate unused tail of image on suspend
Date: Tue, 6 Oct 2026 14:49:22 +0000 [thread overview]
Message-ID: <010701a111b0d0e0-e008fda5-6044-42d8-beed-91c91c536dcb-000000@eu-central-1.amazonses.com> (raw)
In-Reply-To: <20261006144428.341824-1-alexander.ivanov@virtuozzo.com>
> On postsuspend we truncate the image file only down to
> file_preallocated_area_start, i.e. we drop preallocations only.
> Clusters at the end of the file freed by discard (refcount dropped
> to zero) are never given back, so the file size never shrinks.
>
> Add qcow2_calc_used_end(), which scans refcount blocks backward from
> the end of the file and returns the end of the last cluster with
> non-zero refcount. Refcount ranges with no allocated refblock are
> skipped at once. Metadata pages are taken from md cache or read
> synchronously. This is called on suspended device after md
> writeback, so R1 and R2 can't change under us.
>
> Truncate the file to min(file_preallocated_area_start, used end).
> Skip the scan if md writeback failed, as refcounts on disk are stale
> then, and fall back to the old behaviour on scan error.
>
> https://virtuozzo.atlassian.net/browse/VSTOR-148171
> Feature: dm-qcow2: block device over QCOW2 files driver
>
> Signed-off-by: Alexander Ivanov <alexander.ivanov@virtuozzo.com>
Sashiko has reviewed this patch and found no issues. It looks great!
--
Sashiko AI review · https://sashiko.vzint.dev/#/patchset/20261006144428.341824-1-alexander.ivanov@virtuozzo.com?part=1
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next prev parent reply other threads:[~2026-10-06 14:50 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-06 14:44 Alexander Ivanov
2026-10-06 14:45 ` Denis V. Lunev
2026-10-06 14:49 ` no-reply [this message]
2026-10-06 15:52 ` Konstantin Khorenko
2026-10-06 15:56 ` Denis V. Lunev
2026-10-06 17:39 ` Konstantin Khorenko
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