Commit 8b1afc3d authored by NeilBrown's avatar NeilBrown
Browse files

md: Just use RCU when checking for overlap between arrays. 



We don't really need the full mddev_lock here, and having to
drop it is messy.
RCU is enough to protect these lists.

Signed-off-by: default avatarNeilBrown <neilb@suse.de>
parent 50bd3774

drivers/md/md.c

+7 −8
Original line number Diff line number Diff line
@@ -2963,20 +2963,20 @@ rdev_size_store(struct md_rdev *rdev, const char *buf, size_t len) 


	rdev->sectors = sectors;

	if (sectors > oldsectors && my_mddev->external) {

		/* need to check that all other rdevs with the same ->bdev

		 * do not overlap.  We need to unlock the mddev to avoid

		 * a deadlock.  We have already changed rdev->sectors, and if

		 * we have to change it back, we will have the lock again.

		/* Need to check that all other rdevs with the same

		 * ->bdev do not overlap.  'rcu' is sufficient to walk

		 * the rdev lists safely.

		 * This check does not provide a hard guarantee, it

		 * just helps avoid dangerous mistakes.

		 */

		struct mddev *mddev;

		int overlap = 0;

		struct list_head *tmp;



		mddev_unlock(my_mddev);

		rcu_read_lock();

		for_each_mddev(mddev, tmp) {

			struct md_rdev *rdev2;



			mddev_lock_nointr(mddev);

			rdev_for_each(rdev2, mddev)

				if (rdev->bdev == rdev2->bdev &&

				    rdev != rdev2 &&
@@ -2986,13 +2986,12 @@ rdev_size_store(struct md_rdev *rdev, const char *buf, size_t len) 
					overlap = 1;

					break;

				}

			mddev_unlock(mddev);

			if (overlap) {

				mddev_put(mddev);

				break;

			}

		}

		mddev_lock_nointr(my_mddev);

		rcu_read_unlock();

		if (overlap) {

			/* Someone else could have slipped in a size

			 * change here, but doing so is just silly.