On 07/24/2014 03:40 PM, Sebastian Parschauer wrote:

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On 25.06.2014 03:03, NeilBrown wrote:

quoted

On Tue, 24 Jun 2014 17:38:30 +0200 Francis Moreau
[off-list ref] wrote:

quoted

Hello,

I'm having the folloing behaviour with kernel 3.14.5 and mdadm
v3.3.1.

After stopping all arrays, I still can see one of them in
/sys/block/:

# cat /proc/mdstat Personalities : [raid1] md125 : active raid1
sdb3[1] sda3[0] 483688448 blocks super 1.2 [2/2] [UU] 
[======>..............]  resync = 34.9% (169161280/483688448) 
finish=44.0min speed=118852K/sec bitmap: 3/4 pages [12KB],
65536KB chunk

md126 : active raid1 sdb2[1] sda2[0] 4038656 blocks super 1.2
[2/2] [UU]

md127 : active raid1 sdb1[1] sda1[0] 524224 blocks super 1.0
[2/2] [UU]

unused devices: <none>

# mdadm --stop /dev/md12[567] mdadm: stopped /dev/md125 mdadm:
stopped /dev/md126 mdadm: stopped /dev/md127

# cat /proc/mdstat Personalities : [raid1] unused devices:
<none>

# ls /sys/block/ md126  sda  sdb  sdc  sr0

# ls /sys/block/md126/md/ array_size  array_state  bitmap
chunk_size  component_size  layout level  max_read_errors
metadata_version  new_dev  raid_disks reshape_direction
reshape_position  resync_start  safe_mode_delay

# dmesg .... [ 1573.715476] md125: detected capacity change from
495296970752 to 0 [ 1573.715626] md: md125 stopped. [
1573.715633] md: unbind<sdb3> [ 1573.740681] md:
export_rdev(sdb3) [ 1573.740694] md: unbind<sda3> [ 1573.754008]
md: export_rdev(sda3) [ 1573.773398] md126: detected capacity
change from 4135583744 to 0 [ 1573.773403] md: md126 stopped. [
1573.773410] md: unbind<sdb2> [ 1573.820652] md:
export_rdev(sdb2) [ 1573.820664] md: unbind<sda2> [ 1573.873974]
md: export_rdev(sda2) [ 1573.889904] md127: detected capacity
change from 536805376 to 0 [ 1573.889910] md: md127 stopped. [
1573.889917] md: unbind<sdb1> [ 1573.913978] md:
export_rdev(sdb1) [ 1573.914033] md: unbind<sda1> [ 1573.940627]
md: export_rdev(sda1)

After waiting a couple of min, stopping again md126 worked:

[ 1835.755661] md: md126 stopped.

Is this expected ?

No overly surprising.

This is probably caused by udev, or something udev runs, opening
/dev/md126 after it has been stopped.  This has the effect of
creating an empty inactive array. e.g.

mknod /dev/test b 9 57 < /dev/test

will make /sys/block/md57 appear.

It is a bit untidy, but shouldn't cause problems.

NeilBrown

Hi Neil,

we are also noticing this issue with udev-215 on Gentoo. They've
switched over to systemd. Deactivating all udev rules doesn't help. So
it must be an issue in the code. udev-204 works fine.
When stopping udev, then it is possible to stop the MD array and it
remains stopped (/sys/block/mdX disappears). Looks like they do
something really strange there.

Do you have any advice how to fix this in another way but to change
the kernel or to downgrade udev?

File a systemd bug?

Hi,

I have also noticed this issue. It is caused by this change in udev:

commit 3ebdb81ef088afd3b4c72b516beb5610f8c93a0d
Author: Kay Sievers <kay at vrfy.org>
Date:   Sun Apr 13 19:54:27 2014 -0700

     udev: serialize/synchronize block device event handling with file locks

http://cgit.freedesktop.org/systemd/systemd/commit/?id=3ebdb81ef088afd3b4c72b516beb5610f8c93a0d

It seems that they have already disabled this for dm for some reason,
but not for md:

commit e918a1b5a94f270186dca59156354acd2a596494
Author: Kay Sievers [off-list ref]
Date:   Tue Jun 3 16:49:38 2014 +0200

    udev: exclude device-mapper from block device ownership event locking

http://cgit.freedesktop.org/systemd/systemd/commit/?id=e918a1b5a94f270186dca59156354acd2a596494


Artur