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From: Graham Cobb <g.btrfs@cobb.uk.net>
To: linux-btrfs@vger.kernel.org
Subject: "btrfs: harden agaist duplicate fsid" spams syslog
Date: Wed, 10 Jul 2019 19:49:34 +0100	[thread overview]
Message-ID: <5d8baf80-4fb3-221f-5ab4-e98a838f63e1@cobb.uk.net> (raw)

Anand's Nov 2018 patch "btrfs: harden agaist duplicate fsid" has
recently percolated through to my Debian buster server system.

And it is spamming my log files.

Each of my btrfs filesystem devices logs 4 messages every 2 minutes.
Here is an example of the 4 messages related to one device:

Jul 10 19:32:27 black kernel: [33017.407252] BTRFS info (device sdc3):
device fsid 4d1ba5af-8b89-4cb5-96c6-55d1f028a202 devid 4 moved
old:/dev/mapper/cryptdata4tb--vg-backup new:/dev/dm-13
Jul 10 19:32:27 black kernel: [33017.522242] BTRFS info (device sdc3):
device fsid 4d1ba5af-8b89-4cb5-96c6-55d1f028a202 devid 4 moved
old:/dev/dm-13 new:/dev/mapper/cryptdata4tb--vg-backup
Jul 10 19:32:29 black kernel: [33018.797161] BTRFS info (device sdc3):
device fsid 4d1ba5af-8b89-4cb5-96c6-55d1f028a202 devid 4 moved
old:/dev/mapper/cryptdata4tb--vg-backup new:/dev/dm-13
Jul 10 19:32:29 black kernel: [33019.061631] BTRFS info (device sdc3):
device fsid 4d1ba5af-8b89-4cb5-96c6-55d1f028a202 devid 4 moved
old:/dev/dm-13 new:/dev/mapper/cryptdata4tb--vg-backup

What is happening here is that each device is actually an LVM logical
volume, and it is known by a /dev/mapper name and a /dev/dm name. And
every 2 minutes something cause btrfs to notice that there are two names
for the same device and it swaps them around. Logging a message to say
it has done so. And doing it 4 times.

I presume that the swapping doesn't cause any problem. I wonder slightly
whether ordering guarantees and barriers all work correctly but I
haven't noticed any problems.

I also assume it has been doing this for a while -- just silently before
this patch came along.

Is btrfs noticing this itself or is something else (udev or systemd, for
example) triggering it?

Should I worry about it?

Is there any way to not have my log files full of this?

Graham

[This started with a Debian testing kernel a couple of months ago.
Current uname -a gives: Linux black 4.19.0-5-amd64 #1 SMP Debian
4.19.37-5 (2019-06-19) x86_64 GNU/Linux]

             reply	other threads:[~2019-07-10 18:49 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-10 18:49 Graham Cobb [this message]
2019-07-11  2:46 ` "btrfs: harden agaist duplicate fsid" spams syslog Anand Jain
2019-07-11 18:00   ` Graham Cobb
2019-07-12 12:46     ` Anand Jain
2019-07-12 13:32       ` Graham Cobb
2019-07-19 15:38         ` David Sterba
2019-07-12 13:35       ` Patrik Lundquist
2019-07-12 13:41         ` Graham Cobb
2019-07-11 23:06   ` Christoph Anton Mitterer
2019-07-12 12:49     ` Anand Jain
2019-07-16 13:59 ` [PATCH] btrfs: ratelimit device path change info on mounted device Anand Jain
2019-07-16 14:08   ` Anand Jain
2019-07-19 14:58   ` David Sterba

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