From: no-reply@sashiko.virtuozzo.com
To: "Denis V. Lunev" <den@openvz.org>, khorenko@virtuozzo.com
Cc: devel@openvz.org
Subject: Re: [Devel] [PATCH hci-8.1 v2 1/3] dm-ploop: fix flip_upper_deltas returning with two md_locks held
Date: Thu, 5 Nov 2026 15:01:32 +0000 [thread overview]
Message-ID: <010701a1ac3ab984-5011505b-ad1f-4126-a0b2-2d271b7c56e0-000000@eu-central-1.amazonses.com> (raw)
In-Reply-To: <20261105145749.2643035-2-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 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 with the device
> suspended before it flips.
>
> 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
> Reviewed-by: Andrey Zhadchenko <andrey.zhadchenko@virtuozzo.com>
> Reviewed-by: Konstantin Khorenko <khorenko@virtuozzo.com>
> 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/20261105145749.2643035-1-den@openvz.org?part=1
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next prev parent reply other threads:[~2026-11-05 15:02 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-05 14:57 [Devel] [PATCH hci-8.1 v2 0/3] dm-ploop: fix flip_upper_deltas panicking the host in its pre-flip check Denis V. Lunev
2026-11-05 14:57 ` [Devel] [PATCH hci-8.1 v2 1/3] dm-ploop: fix flip_upper_deltas returning with two md_locks held Denis V. Lunev
2026-11-05 15:01 ` no-reply [this message]
2026-11-05 14:57 ` [Devel] [PATCH hci-8.1 v2 2/3] dm-ploop: refuse flip_upper_deltas onto a lower delta smaller than the device Denis V. Lunev
2026-11-05 15:02 ` no-reply
2026-11-05 18:19 ` Konstantin Khorenko
2026-11-05 14:57 ` [Devel] [PATCH hci-8.1 v2 3/3] dm-ploop: fix the flip_upper_deltas check skipping the last BAT entry Denis V. Lunev
2026-11-05 15:02 ` no-reply
2026-11-05 18:19 ` Konstantin Khorenko
2026-11-05 18:19 ` [Devel] [PATCH hci-8.1 v2 0/3] dm-ploop: fix flip_upper_deltas panicking the host in its pre-flip check Konstantin Khorenko
2026-11-05 18:19 ` Konstantin Khorenko
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