From: no-reply@sashiko.virtuozzo.com
To: "Denis V. Lunev" <den@openvz.org>, andrey.zhadchenko@virtuozzo.com
Cc: devel@openvz.org
Subject: Re: [Devel] [PATCH hci-8.1 1/2] dm-ploop: fix flip_upper_deltas returning with two md_locks held
Date: Wed, 4 Nov 2026 21:50:55 +0000 [thread overview]
Message-ID: <010701a1a88b2c87-4ec6796e-3c75-40ee-9c89-b53f691c1c58-000000@eu-central-1.amazonses.com> (raw)
In-Reply-To: <20261104214635.2063009-2-den@openvz.org>
> From: Denis V. Lunev <den@openvz.org>
>
> ploop_check_delta_before_flip() takes the md_lock of a live BAT page
> and of the matching page of the lower delta before it compares them.
> When it finds a cluster both deltas map, it jumps to unmap past both
> unlocks: the cmd returns -EEXIST with the locks held and interrupts
> disabled, after freeing the page of the lower delta with its lock still
> taken. dmsetup comes back to userspace in atomic context, and the next
> pio touching that BAT page spins on its md_lock for good, a hard
> lockup.
>
> A flip_upper_deltas message, with both deltas opened read-write, on a
> chain where the top delta overwrote a cluster of the lower one gets
> there. The ploop library does not: its reverse merge clears those
> entries in the lower delta before it flips, and a device it mounted has
> the lower delta read-only, which the flip refuses before the check.
>
> Leave the scan only after both locks are dropped.
>
> Fixes: 0d4b4d0a20a9 ("dm-ploop: introduce per-md page locking")
> https://virtuozzo.atlassian.net/browse/VSTOR-153445
> Feature: dm-ploop: ploop target driver
> Signed-off-by: Denis V. Lunev <den@openvz.org>
Sashiko has reviewed this patch and found no issues. It looks great!
--
Sashiko AI review · https://sashiko.vzint.dev/#/patchset/20261104214635.2063009-1-den@openvz.org?part=1
_______________________________________________
Devel mailing list
Devel@openvz.org
https://lists.openvz.org/mailman/listinfo/devel
next prev parent reply other threads:[~2026-11-04 21:52 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-04 21:46 [Devel] [PATCH hci-8.1 0/2] dm-ploop: fix flip_upper_deltas panicking the host in its pre-flip check Denis V. Lunev
2026-11-04 21:46 ` [Devel] [PATCH hci-8.1 1/2] dm-ploop: fix flip_upper_deltas returning with two md_locks held Denis V. Lunev
2026-11-04 21:50 ` no-reply [this message]
2026-11-04 21:46 ` [Devel] [PATCH hci-8.1 2/2] dm-ploop: fix flip_upper_deltas walking past the BAT of the lower delta Denis V. Lunev
2026-11-04 21:50 ` no-reply
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=010701a1a88b2c87-4ec6796e-3c75-40ee-9c89-b53f691c1c58-000000@eu-central-1.amazonses.com \
--to=no-reply@sashiko.virtuozzo.com \
--cc=andrey.zhadchenko@virtuozzo.com \
--cc=den@openvz.org \
--cc=devel@openvz.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox