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Commit 6cbd8148 authored by NeilBrown's avatar NeilBrown
Browse files

md/raid5: handle possible race as reshape completes. 



It is possible (though unlikely) for a reshape to be
interrupted between the time that end_reshape is called
and the time when raid5_finish_reshape is called.

This can leave conf->reshape_progress set to MaxSector,
but mddev->reshape_position not.

This combination confused reshape_request() when ->reshape_backwards.
As conf->reshape_progress is so high, it seems the reshape hasn't
really begun.  But assuming MaxSector is a valid address only
leads to sorrow.

So ensure reshape_position and reshape_progress both agree,
and add an extra check in reshape_request() just in case they don't.

Signed-off-by: default avatarNeilBrown <neilb@suse.com>
parent 5ed1df2e

drivers/md/raid5.c

+5 −0
Original line number Diff line number Diff line
@@ -5355,6 +5355,10 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr, int *sk 
		    conf->reshape_progress < raid5_size(mddev, 0, 0)) {

			sector_nr = raid5_size(mddev, 0, 0)

				- conf->reshape_progress;

		} else if (mddev->reshape_backwards &&

			   conf->reshape_progress == MaxSector) {

			/* shouldn't happen, but just in case, finish up.*/

			sector_nr = MaxSector;

		} else if (!mddev->reshape_backwards &&

			   conf->reshape_progress > 0)

			sector_nr = conf->reshape_progress;
@@ -7446,6 +7450,7 @@ static void end_reshape(struct r5conf *conf) 
			rdev->data_offset = rdev->new_data_offset;

		smp_wmb();

		conf->reshape_progress = MaxSector;

		conf->mddev->reshape_position = MaxSector;

		spin_unlock_irq(&conf->device_lock);

		wake_up(&conf->wait_for_overlap);