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788e413946
reshape stripe lifetime:
- start reshape ==> reshape_request():
* get destination stripe,
- if need to copy source data chunks, set STRIPE_EXPANDING;
- or, if new regions past the old end of the array, zero-filled,
no need source data, set STRIPE_EXPANDING | STRIPE_READY
* get source stripe,
- set STRIPE_EXPAND_SOURCE
- handle expand stripe ==> handle_stripe():
reshape use reconstruct-write to construct stripe,
four stages:
1. prepare source data chunks for old geometry stripe
- fill source stripe data by read or compute
2. move data from old geometry source stripe to new geometry
destination stripe
- source stripe clear STRIPE_EXPAND_SOURCE
- drain data from source to destination stripe
- mark stripe chunk as R5_Expanded|R5_UPTODATE when the
drain from source chunk to destination chunk is completed
- all stripe chunks drain are completed, then mark
STRIPE_EXPAND_READY
3. calculate p/q chunks for destination stripe
- if destination stripe doesn't depends on source dstripe,
then we can clear STRIPE_EXPANDING
4. write-out to disks and release
- set R5_Wantwrite|R5_Locked, writeout to disk
- if write-out succeeded, clear STRIPE_EXPAND_READY, and
decrement reshape_stripe, call md_done_sync() to report
reshape progress.
1. cleanup the following kinds of **destination stripe**
when failed device more than max degraded:
- new regions past the old end of the array, zero-filled in place,
requires no source data.
(STRIPE_EXPANDING | STRIPE_EXPAND_READY)
- prepare source data chunks already done, and writeout failed
(STRIPE_EXPAND_READY)
2. destination stripes that need source data
(STRIPE_EXPANDING, no STRIPE_HANDLE)
- these kind of stripes sit idle in the stripe cache and are never seen
by handle_stripe(). So clean up indirectly when their source stripe
(type 3) is processed.
3. source stripes (STRIPE_EXPAND_SOURCE)
- hit handle_stripe() after their member disks are marked Faulty.
- clear STRIPE_EXPAND_SOURCE, finds and cleanup all dependent destination
stripes that were waiting for data.
- walks the source's data disks, compute the corresponding destination
sector, looks up the destination stripe, and do cleanup(clear flags,
dec counters, call md_done_sync())
Reproducer:
- Create a 4-disk RAID5 with mdadm on top of 5 disposable test disks
wrapped by dm targets.
- Add the 5th device as a spare and start a 4 -> 5 reshape.
- Wait until /sys/block/mdX/md/sync_action reports "reshape".
- Inject failures on two members so reshape exceeds max_degraded.
- After a few seconds, write "frozen" to /sys/block/mdX/md/sync_action.
Before this fix, the write blocks indefinitely.
Read-error variant:
- Use dm-dust on /dev/sd[b-f].
- Preload bad blocks on two source members, e.g. dust0 and dust1:
dmsetup message dust0 0 addbadblock <range>
dmsetup message dust1 0 addbadblock <range>
- Start reshape:
mdadm -C /dev/mdX -e 1.2 -l 5 -n 4 -c 64 \
--assume-clean /dev/mapper/dust{0..3}
mdadm --manage /dev/mdX --add /dev/mapper/dust4
mdadm --grow /dev/mdX -n 5 --backup-file=/tmp/grow.backup &
- Once reshape starts, enable the injected read failures:
dmsetup message dust0 0 enable
dmsetup message dust1 0 enable
- Then:
echo frozen > /sys/block/mdX/md/sync_action
hangs forever before the fix.
Write-error variant:
- Use dm-flakey on /dev/sd[b-f].
- Start the same 4 -> 5 reshape on flakey0..flakey4.
- Once reshape starts, switch two members, e.g. flakey3 and flakey4,
to error_writes.
- Then:
echo frozen > /sys/block/mdX/md/sync_action
hangs forever before the fix.
md_do_sync() exits its main loop on MD_RECOVERY_INTR but then blocks
forever at:
wait_event(mddev->recovery_wait,
!atomic_read(&mddev->recovery_active));
After the fix recovery_active drains to zero, md_do_sync() prints
md/raid:md0: Cannot continue operation (2/5 failed).
md: md0: reshape interrupted.
Signed-off-by: Chen Cheng <chencheng@fnnas.com>
Reviewed-by: Yu Kuai <yukuai@fygo.io>
Link: https://patch.msgid.link/20260624075824.2601110-1-chencheng@fnnas.com
Signed-off-by: Yu Kuai <yukuai@fygo.io>
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