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Commit df8e7f76 authored by NeilBrown's avatar NeilBrown Committed by Linus Torvalds
Browse files

[PATCH] md: Improve comments about locking situation in raid5 make_request 



Signed-off-by: default avatarNeil Brown <neilb@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent e464eafd

drivers/md/raid5.c

+14 −1
Original line number Diff line number Diff line
@@ -1768,6 +1768,14 @@ static int make_request(request_queue_t *q, struct bio * bi) 
		if (likely(conf->expand_progress == MaxSector))

			disks = conf->raid_disks;

		else {

			/* spinlock is needed as expand_progress may be

			 * 64bit on a 32bit platform, and so it might be

			 * possible to see a half-updated value

			 * Ofcourse expand_progress could change after

			 * the lock is dropped, so once we get a reference

			 * to the stripe that we think it is, we will have

			 * to check again.

			 */

			spin_lock_irq(&conf->device_lock);

			disks = conf->raid_disks;

			if (logical_sector >= conf->expand_progress)
@@ -1791,7 +1799,12 @@ static int make_request(request_queue_t *q, struct bio * bi) 
		if (sh) {

			if (unlikely(conf->expand_progress != MaxSector)) {

				/* expansion might have moved on while waiting for a

				 * stripe, so we much do the range check again.

				 * stripe, so we must do the range check again.

				 * Expansion could still move past after this

				 * test, but as we are holding a reference to

				 * 'sh', we know that if that happens,

				 *  STRIPE_EXPANDING will get set and the expansion

				 * won't proceed until we finish with the stripe.

				 */

				int must_retry = 0;

				spin_lock_irq(&conf->device_lock);