[Devel] [PATCH hci-8.1 v2 4/4] dm-ploop: fix lost BAT updates when alloc and discard share a writeback

[no-reply at sashiko.virtuozzo.com]

> From: Denis V. Lunev <den at openvz.org>
> 
> Since "dm-ploop: fix and rework md updates" any update of a BAT page
> joins the pending index writeback of that page, whatever type it was
> prepared with. On completion ploop_advance_local_after_bat_wb() still
> applied the written page by type: a DISCARD writeback copied back only
> entries that became zero, an ALLOC one only non-zero entries.
> 
> A first write to a cluster that joined a pending DISCARD writeback was
> acknowledged with its new mapping on disk but not in the local BAT. It
> read back as zeroes, the next write to the cluster allocated another
> one, and the next writeback of the page stored that, leaking the
> cluster with the acknowledged data. A discard that joined an ALLOC
> writeback left the local BAT mapped while disk had zero, so data
> written to that cluster afterwards was lost on the next open.
> [ ... ]
> 
> Fixes: ddf38fa44df4 ("dm-ploop: fix and rework md updates")
> https://virtuozzo.atlassian.net/browse/VSTOR-151979
> 
> Signed-off-by: Denis V. Lunev <den at openvz.org>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.vzint.dev/#/patchset/20261028143647.2972030-1-den@openvz.org?part=4