Re: [Devel] [PATCH hci-8.1 v9 05/10] dm-qcow2: flush lower metadata before clearing its dirty bit on merge failure

[Konstantin Khorenko <khorenko@virtuozzo.com>]

I won't apply this version, please send v10 with the changes below.

On 10/28/26 16:06, Alexander Ivanov wrote:
> leaves the lower image marked clean on disk with L2 tables and refblocks
> that lag behind the merged data.
>
> A failed md writeback of the lower image is also missed:
> md_writeback_error is set only by qcow2_flush_deferred_activity(), so
> the next resume is not refused.

- Drop the second paragraph.
- Say refblocks only, not "L2 tables and refblocks".
- Shorten the subject, it is 77 columns.

The next postsuspend flushes the lower image as well:
qcow2_flush_deferred_activity_all() walks tgt->top and every ->lower
and sets md_writeback_error on a failed write. So that resume is
refused already. What the patch adds is the order: the flush now comes
before the header write that clears the dirty bit.

Merge writes wait for their L2 writeback before they complete, so L2
does not lag. Only the refblocks are in the delayed writeback.

-- 
Konstantin Khorenko,
Virtuozzo Linux Kernel Team

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