md/raid5: handle possible race as reshape completes. (6cbd8148) · Commits · 戴 / test

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:

NeilBrown <neilb@suse.com>

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);

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