[Devel] [PATCH hci-8.1 v2 2/3] dm-qcow2: fix backward merge of an inner image racing its reads

[Konstantin Khorenko]

I won't apply this version, please send v2 with the changes below.

On 11/3/26 10:08, Denis V. Lunev wrote:
> Pause submission and switch the inflight refs for every image. The
> pause flag is only tested on the top image, where all qios enter, so
> pause that one; clearing the flag of an inner image paused the inner
> image itself, which held nothing back.

Item 3 of the cover letter reply: say here that guest I/O to the top
image is now paused for the inflight ref switch when a merge of an
inner image starts or stops. That is fine, a merge of the top image
always cost the same, but the message should say it.

> +	 * A lower image has no writes, but it is read by
> +	 * qios of the top one, so stop the top image even then.

Item 2 of the cover letter reply: write "no guest writes". A writable
inner image is still written by qcow2_break_l1cow() and by the merge
itself.

With that fixed:

Reviewed-by: Konstantin Khorenko <khorenko at virtuozzo.com>

-- 
Konstantin Khorenko,
Virtuozzo Linux Kernel Team