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md: wake raid456 reshape waiters before suspend

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During raid456 reshape, direct IO across the reshape position can sleep
in raid5_make_request() waiting for reshape progress while still
holding an active_io reference. If userspace then freezes reshape and
writes md/suspend_lo or md/suspend_hi, mddev_suspend() kills active_io
and waits for all in-flight IO to drain.

This can deadlock: the IO needs reshape progress to continue, but the
reshape thread is already frozen, so the active_io reference is never
dropped and suspend never completes.

raid5_prepare_suspend() already wakes wait_for_reshape for dm-raid. Do
the same for normal md suspend when reshape is already interrupted, so
waiting raid456 IO can abort, drop its reference, and let suspend
finish.

The mdadm test tests/25raid456-reshape-deadlock reproduces the hang.

Fixes: 714d20150e ("md: add new helpers to suspend/resume array")
Link: https://lore.kernel.org/linux-raid/20260327140729.2030564-1-yukuai@fnnas.com/
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
This commit is contained in:
Yu Kuai
2026-03-27 22:07:29 +08:00
parent 808cec7460
commit cf86bb53b9
1 changed files with 11 additions and 0 deletions
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11
drivers/md/md.c
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@@ -487,6 +487,17 @@ int mddev_suspend(struct mddev *mddev, bool interruptible)
}
percpu_ref_kill(&mddev->active_io);
/*
* RAID456 IO can sleep in wait_for_reshape while still holding an
* active_io reference. If reshape is already interrupted or frozen,
* wake those waiters so they can abort and drop the reference instead
* of deadlocking suspend.
*/
if (mddev->pers && mddev->pers->prepare_suspend &&
reshape_interrupted(mddev))
mddev->pers->prepare_suspend(mddev);
if (interruptible)
err = wait_event_interruptible(mddev->sb_wait,
percpu_ref_is_zero(&mddev->active_io));