Re: /sys/block/md126 still exists even after stopping the array

[Sebastian Parschauer <sebastian.riemer@profitbricks.com>]

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On 25.06.2014 03:03, NeilBrown wrote:
> On Tue, 24 Jun 2014 17:38:30 +0200 Francis Moreau
> <francis.moro@gmail.com> wrote:
> 
>> 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?

Cheers,
Sebastian
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