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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.