From: no-reply@sashiko.virtuozzo.com
To: Alexander Ivanov <alexander.ivanov@virtuozzo.com>, den@openvz.org
Cc: devel@openvz.org
Subject: Re: [Devel] [PATCH hci-8.1 v3 3/3] dm-qcow2: truncate unused tail of image on suspend
Date: Thu, 8 Oct 2026 10:11:13 +0000 [thread overview]
Message-ID: <010701a11afedf20-ee9424da-fbb3-4354-b210-d6d07828bd37-000000@eu-central-1.amazonses.com> (raw)
In-Reply-To: <20261008100449.550882-4-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
> file_preallocated_area_start 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 the 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/20261008100449.550882-1-alexander.ivanov@virtuozzo.com?part=3
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next prev parent reply other threads:[~2026-10-08 10:12 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-08 10:04 [Devel] [PATCH hci-8.1 v3 0/3] " Alexander Ivanov
2026-10-08 10:04 ` [Devel] [PATCH hci-8.1 v3 1/3] dm-qcow2: add qcow2_md_page_read_sync() helper Alexander Ivanov
2026-10-08 10:09 ` no-reply
2026-10-08 10:57 ` Denis V. Lunev
2026-10-08 10:04 ` [Devel] [PATCH hci-8.1 v3 2/3] dm-qcow2: drop duplicate prefix from QC_ERR/QC_INFO messages Alexander Ivanov
2026-10-08 10:07 ` no-reply
2026-10-08 10:04 ` [Devel] [PATCH hci-8.1 v3 3/3] dm-qcow2: truncate unused tail of image on suspend Alexander Ivanov
2026-10-08 10:11 ` no-reply [this message]
2026-10-08 10:58 ` Denis V. Lunev
2026-10-08 10:59 ` [Devel] [PATCH hci-8.1 v3 0/3] " Denis V. Lunev
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