Commit cf86bb53 authored by Yu Kuai's avatar Yu Kuai
Browse files

md: wake raid456 reshape waiters before suspend 

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: 714d2015 ("md: add new helpers to suspend/resume array")
Link: https://lore.kernel.org/linux-raid/20260327140729.2030564-1-yukuai@fnnas.com/


Signed-off-by: default avatarYu Kuai <yukuai@fnnas.com>
parent 808cec74

drivers/md/md.c

+11 −0
Original line number Diff line number Diff line
@@ -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));