From: Marc Lehmann <schmorp@schmorp.de>
To: linux-btrfs@vger.kernel.org
Subject: btrfs dev del not transaction protected?
Date: Fri, 20 Dec 2019 05:05:37 +0100 [thread overview]
Message-ID: <20191220040536.GA1682@schmorp.de> (raw)
Hi!
I used btrfs del /somedevice /mountpoint to remove a device, and then typed
sync. A short time later the system had a hard reset.
Now the file system doesn't mount read-write anymore because it complains
about a missing device (linux 5.4.5):
[ 247.385346] BTRFS error (device dm-32): devid 1 uuid f5c3dc63-1fac-45b3-b9ba-ed1ec5f92403 is missing
[ 247.386942] BTRFS error (device dm-32): failed to read chunk tree: -2
[ 247.462693] BTRFS error (device dm-32): open_ctree failed
The thing is, the device is still there and accessible, but btrfs no longer
recognises it, as it already deleted it before the crash.
I can mount the filesystem in degraded mode, and I have a backup in case
somehting isn't readable, so this is merely a costly inconvinience for me
(it's a 40TB volume), but this seems very unexpected, both that device
dels apparently have a race condition and that sync doesn't actually
synchronise the filesystem - I naively expected that btrfs dev del doesn't
cause the loss of the filesystem due to a system crash.
Probably nbot related, but maybe worth mentioning: I found that system
crashes (resets, not power failures) cause btrfs to not mount the first
time a mount is attempted, but it always succeeds the second time, e.g.:
# mount /device /mnt
... no errors or warnings in kernel log, except:
BTRFS error (device dm-34): open_ctree failed
# mount /device /mnt
magically succeeds
The typical symptom here is that systemd goes into emergency mode on mount
failure, but simpyl rebooting, or executing the mount manually then succeeds.
Greetings,
Marc
--
The choice of a Deliantra, the free code+content MORPG
-----==- _GNU_ http://www.deliantra.net
----==-- _ generation
---==---(_)__ __ ____ __ Marc Lehmann
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next reply other threads:[~2019-12-20 4:44 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-20 4:05 Marc Lehmann [this message]
2019-12-20 5:24 ` btrfs dev del not transaction protected? Qu Wenruo
2019-12-20 6:37 ` Marc Lehmann
2019-12-20 7:10 ` Qu Wenruo
2019-12-20 13:27 ` Marc Lehmann
2019-12-20 13:41 ` Qu Wenruo
2019-12-20 16:53 ` Marc Lehmann
2019-12-20 17:24 ` Remi Gauvin
2019-12-20 17:50 ` Marc Lehmann
2019-12-20 18:00 ` Marc Lehmann
2019-12-20 18:28 ` Eli V
2019-12-20 20:24 ` Chris Murphy
2019-12-20 23:30 ` Marc Lehmann
2019-12-21 20:06 ` Zygo Blaxell
2019-12-21 1:32 ` Qu Wenruo
2019-12-20 17:07 ` Marc Lehmann
2019-12-21 1:23 ` Qu Wenruo
2019-12-20 17:20 ` Marc Lehmann
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