From: no-reply@sashiko.virtuozzo.com
To: Alexander Ivanov <alexander.ivanov@virtuozzo.com>,
andrey.zhadchenko@virtuozzo.com
Cc: devel@openvz.org
Subject: Re: [Devel] [PATCH hci-8.1 1/3] drivers/md/dm-qcow2: treat images of a read-only table as read-only
Date: Fri, 23 Oct 2026 13:24:50 +0000 [thread overview]
Message-ID: <010701a168ef8573-eef82593-52b1-4791-be27-a56a648ba41a-000000@eu-central-1.amazonses.com> (raw)
In-Reply-To: <20261023132008.2304901-2-alexander.ivanov@virtuozzo.com>
> Whether an image may be modified is decided by the mode of its file
> only. Userspace may pass an O_RDWR top image to a read-only table, and
> then dm-qcow2 truncates the unaligned image tail on every .ctr and
> .preresume and considers the image writable on the I/O and discard
> paths.
>
> merge_backward is also allowed on a read-only table if the lower image
> is opened for write. qcow2_set_image_file_features() checks the table
> mode and skips the lower image, so the merge writes to it without the
> dirty bit and without clearing the bitmaps autoclear bit. Enabled
> persistent bitmaps of the lower image are left marked consistent
> although the image data changed.
>
> Consider an image writable only if both its file and the table are
> writable, and use this check for the header update, the tail truncate
> and the short read near EOF as well. merge_backward on a read-only
> table now fails with -EACCES.
>
> https://virtuozzo.atlassian.net/browse/VSTOR-138887
> 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/20261023132008.2304901-1-alexander.ivanov@virtuozzo.com?part=1
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next prev parent reply other threads:[~2026-10-23 13:26 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-23 13:20 [Devel] [PATCH hci-8.1 0/3] dm-qcow2: keep images of a read-only table unmodified Alexander Ivanov
2026-10-23 13:20 ` [Devel] [PATCH hci-8.1 1/3] drivers/md/dm-qcow2: treat images of a read-only table as read-only Alexander Ivanov
2026-10-23 13:24 ` no-reply [this message]
2026-10-29 11:36 ` Konstantin Khorenko
2026-10-23 13:20 ` [Devel] [PATCH hci-8.1 2/3] drivers/md/dm-qcow2: fail writes to a read-only table Alexander Ivanov
2026-10-23 13:23 ` no-reply
2026-10-28 10:35 ` Andrey Zhadchenko
2026-10-23 13:20 ` [Devel] [PATCH hci-8.1 3/3] drivers/md/dm-qcow2: do not revalidate inconsistent persistent bitmaps Alexander Ivanov
2026-10-23 13:25 ` no-reply
2026-10-23 13:58 ` Alexander Ivanov
2026-10-29 11:39 ` Konstantin Khorenko
2026-10-28 10:47 ` [Devel] [PATCH hci-8.1 0/3] dm-qcow2: keep images of a read-only table unmodified Andrey Zhadchenko
2026-10-29 11:42 ` Konstantin Khorenko
2026-10-29 14:48 ` Alexander Ivanov
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