[Devel] [PATCH hci-8.1 0/3] dm-qcow2: keep images of a read-only table unmodified

[Andrey Zhadchenko]

We probably don't need an extra respin to delete the single comment. 
@khorenko could you please remove it from patch 2/3 before applying?

Reviewed-by: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>

On 10/23/26 15:20, Alexander Ivanov wrote:
> A read-only dm-qcow2 table does not protect its images. Writes to the
> device pass through bio_check_ro() with a warning and allocate clusters
> in the top image, an O_RDWR top image is truncated on .ctr and
> .preresume, and merge_backward modifies the lower image. Since the
> header is not updated for a read-only table, persistent bitmaps stay
> marked consistent while the data under them changes.
> 
> Patch 1 makes an image writable only if both its file and the table
> are writable. Patch 2 fails writes to a read-only table. Patch 3 keeps
> the bitmaps autoclear bit clear if it is already clear in the image,
> so that a later writable open does not revalidate stale bitmaps.
> 
> https://virtuozzo.atlassian.net/browse/VSTOR-138887
> 
> Alexander Ivanov (3):
>    drivers/md/dm-qcow2: treat images of a read-only table as read-only
>    drivers/md/dm-qcow2: fail writes to a read-only table
>    drivers/md/dm-qcow2: do not revalidate inconsistent persistent bitmaps
> 
>   drivers/md/dm-qcow2-map.c    |  9 ++++++---
>   drivers/md/dm-qcow2-target.c | 11 +++++++----
>   drivers/md/dm-qcow2.h        |  3 ++-
>   3 files changed, 15 insertions(+), 8 deletions(-)
>