IMSM: finish recovery when drive with rebuild fails

[Mariusz Tkaczyk]

Current version of mdadm doesn't have second fix for raid10.
Mdmon is not able do handle end recovery if drive was disconnected while rebuild.

Steps to reproduce:

1. Create RAID10 and wait for resync.
#mdadm --create /dev/md/imsm0 --metadata=imsm --raid-devices=4 /dev/sda /dev/sdb /dev/sde /dev/sdf –run
#mdadm --create /dev/md/r10d4s64_A --level=10 --chunk 64 --raid-devices=4 /dev/sda /dev/sdb /dev/sde /dev/sdf –run

2. Degrade RAID 10 volume by disconnecting 2 drives.
#mdadm -If sdb
#mdadm -If sdf

3. Add spare drive.
#mdadm --add /dev/md/imsm0 /dev/sdg

4. Wait for recovery start.

5. While rebuild, disconnect recovered member drive (spare added in step 4).

6. Add another spare drive.
#mdadm --add /dev/md/imsm0 /dev/sdh

7. Wait for recovery start.

Expected result:
Recovery starts automatically.

Actual result:
Recovery does not start.

Following fix resolves the issue:
https://git.kernel.org/pub/scm/utils/mdadm/mdadm.git/commit/?id=a4e96fd8f3f0b5416783237c1cb6ee87e7eff23d

[Launchpad Janitor (janitor)]

[Expired for mdadm (Ubuntu Impish) because there has been no activity for 60 days.]

[Launchpad Janitor (janitor)]

[Expired for mdadm (Ubuntu) because there has been no activity for 60 days.]