Re: MD: drive removal hangs with freshly created partition

[Mariusz Tkaczyk <mariusz.tkaczyk@linux.intel.com>]

On Tue, 2 Jul 2024 16:57:38 +0200
Mateusz Kusiak <mateusz.kusiak@linux.intel.com> wrote:

> Hello,
> I'm back with another regression found in SLES15SP6.
> 
> The scenario is as follows:
> 1.Create RAID 1 volume with native metadata.
> # mdadm -CR /dev/md126 -l1 -n2 /dev/nvme[0-1]n1 --assume-clean --size=5G
> 
> 2. Create partition and filesystem on raid volume.
> # parted -a optimal /dev/md126 mktable gpt mkpart primary ext4 0% 100% -s
> # mkfs.ext4 -F /dev/md126p1
> 
> 3. Remove device via "--incremental --fail".
> # mdadm -If nvme0n1
> 
> Result:
> Mdadm hangs and hung task info from mutliple components starts appearing on
> serial.
> 
> Few notes:
> * Issue does not reproduce without creating partition and filesystem.
> * If array is stopped and reassembled before step 3, the issue does not
> reproduce.
> * If partition is "reused" (metadata was cleared, new raid volume created,
> partition left in tact, no recreating partition) the issue does not reproduce.
> * If "--set-faulty" and then "--remove" used (instead of "--incremental
> --fail") "--set-faulty" succeeds, "--remove" hangs.
> * I verified this is not mdadm issue by installing mdadm-4.2 (SLES15SP6 has
> mdadm-4.3 inbox) and rerunning the test. Outcome is the same.
> * Writing "remove" to sysfs directly has same result.
> 
> Thanks,
> Mateusz
> 

More info:
As Mateusz said echo "remove" >/sys/block/md126/md/rd0/state hangs. Same hang
is observed with HOT_REMOVE_DISK ioctl. We can simulate the scenario by:

echo "faulty" >/sys/block/md126/md/rd0/state
echo "remove" >/sys/block/md126/md/rd0/state

This is really interesting that it is only happening with partitions and only
after their creation.

Mariusz