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** Changed in: linux (Ubuntu)
Status: New => Incomplete
** Tags added: eoan
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https://bugs.launchpad.net/bugs/1882312
Title:
RAID5 reshape stuck due to same badblock on multiple devices
Status in linux package in Ubuntu:
Incomplete
Bug description:
Linux [hostname removed] 5.3.0-55-generic #49-Ubuntu SMP Thu May 21
12:47:19 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
Ubuntu release: 19.10 (although the same issue is present in 18.04 and
20.04 as well).
A RAID5 reshape from 3 to 4 devices got stuck:
md127 : active raid5 sde1[5] sdd1[4] sdc1[0] sdf1[3]
7813769216 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/4]
[UUUU]
[>....................] reshape = 1.8% (72261116/3906884608)
finish=1663133.7min speed=38K/sec
bitmap: 0/30 pages [0KB], 65536KB chunk
with the following stack trace:
[54979.996871] INFO: task md127_reshape:7090 blocked for more than 1208
seconds.
[54979.996922] Tainted: P OE 5.3.0-55-generic #49-Ubuntu
[54979.996967] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables
this message.
[54979.997018] md127_reshape D 0 7090 2 0x80004080
[54979.997019] Call Trace:
[54979.997022] __schedule+0x2b9/0x6c0
[54979.997023] schedule+0x42/0xb0
[54979.997027] reshape_request+0x878/0x950 [raid456]
[54979.997028] ? wait_woken+0x80/0x80
[54979.997030] raid5_sync_request+0x302/0x3b0 [raid456]
[54979.997032] md_do_sync.cold+0x3ef/0x999
[54979.997034] ? ecryptfs_write_begin+0x70/0x280
[54979.997034] ? __switch_to_asm+0x40/0x70
[54979.997035] ? __switch_to_asm+0x34/0x70
[54979.997035] ? __switch_to_asm+0x40/0x70
[54979.997036] ? __switch_to_asm+0x34/0x70
[54979.997036] ? __switch_to_asm+0x40/0x70
[54979.997037] ? __switch_to_asm+0x34/0x70
[54979.997038] md_thread+0x97/0x160
[54979.997040] kthread+0x104/0x140
[54979.997040] ? md_start_sync+0x60/0x60
[54979.997041] ? kthread_park+0x80/0x80
[54979.997042] ret_from_fork+0x35/0x40
No other hardware errors were reported and the reshape got stuck at
somewhat different blocks every time it was restarted (all within the
same vicinity of each others). It turns out that md had injected the
same exact sector into the badblock log of multiple devices at some
point before the reshape was started. This could be seen with "mdadm
--examine-badblocks /dev/sdXY". The original cause for the badblocks
entries was probably a loose cable as the reported sectors were fully
readable with the "dd" and "badblocks" command.
The problem was eventually resolved by removing the badblock log on
the RAID5 device using "mdadm --assemble /dev/md0 --update=force-no-
bbl". Having removed the badblock log, reshape progressed beyond the
previously troublesome area of blocks.
I would have expected at least an error message in the kernel log
rather than just a "hung task" message, probably before the reshape
was allowed to be initiated (aka early termination). Furthermore, it
would be beneficial if mdadm could allow the badblock log to be
cleared for a device rather than removed on the array with "update
=force-no-bbl".
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