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Date:   Thu, 2 Jul 2020 23:17:43 +0200
From:   Pavel Machek <pavel@ucw.cz>
To:     Sasha Levin <sashal@kernel.org>
Cc:     linux-kernel@vger.kernel.org, stable@vger.kernel.org,
        Sagi Grimberg <sagi@grimberg.me>,
        Anton Eidelman <anton@lightbitslabs.com>,
        Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 4.19 082/131] nvme: fix possible deadlock when I/O is
 blocked
Message-ID: <20200702211743.GE5787@amd>
References: <20200629153502.2494656-1-sashal@kernel.org>
 <20200629153502.2494656-83-sashal@kernel.org>
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Hi!

> From: Sagi Grimberg <sagi@grimberg.me>
>=20
> [ Upstream commit 3b4b19721ec652ad2c4fe51dfbe5124212b5f581 ]
>=20
> Revert fab7772bfbcf ("nvme-multipath: revalidate nvme_ns_head gendisk
> in nvme_validate_ns")
>=20
> When adding a new namespace to the head disk (via nvme_mpath_set_live)
> we will see partition scan which triggers I/O on the mpath device node.
> This process will usually be triggered from the scan_work which holds
> the scan_lock. If I/O blocks (if we got ana change currently have only
> available paths but none are accessible) this can deadlock on the head
> disk bd_mutex as both partition scan I/O takes it, and head disk revalida=
tion
> takes it to check for resize (also triggered from scan_work on a different
> path). See trace [1].
>=20
> The mpath disk revalidation was originally added to detect online disk
> size change, but this is no longer needed since commit cb224c3af4df
> ("nvme: Convert to use set_capacity_revalidate_and_notify") which already
> updates resize info without unnecessarily revalidating the disk (the

Unfortunately, v4.19-stable does not contain cb224c3af4df. According
to changelog, it seems it should be cherry-picked?

Best regards,
									Pavel
--=20
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo=
g.html

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