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Commit e0a33270 authored by NeilBrown's avatar NeilBrown Committed by Linus Torvalds
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[PATCH] md: Fixed refcounting/locking when attempting read error correction in raid10 



We need to hold a reference to rdevs while reading and writing to attempt to
correct read errors.  This reference must be taken under an rcu lock.

Signed-off-by: default avatarNeil Brown <neilb@suse.de>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent df30d0f4

drivers/md/raid10.c

+30 −14
Original line number Diff line number Diff line
@@ -1407,36 +1407,45 @@ static void raid10d(mddev_t *mddev) 
				if (s > (PAGE_SIZE>>9))

					s = PAGE_SIZE >> 9;



				rcu_read_lock();

				do {

					int d = r10_bio->devs[sl].devnum;

					rdev = conf->mirrors[d].rdev;

					rdev = rcu_dereference(conf->mirrors[d].rdev);

					if (rdev &&

					    test_bit(In_sync, &rdev->flags) &&

					    sync_page_io(rdev->bdev,

					    test_bit(In_sync, &rdev->flags)) {

						atomic_inc(&rdev->nr_pending);

						rcu_read_unlock();

						success = sync_page_io(rdev->bdev,

								       r10_bio->devs[sl].addr +

								       sect + rdev->data_offset,

								       s<<9,

							 conf->tmppage, READ))

						success = 1;

					else {

								       conf->tmppage, READ);

						rdev_dec_pending(rdev, mddev);

						rcu_read_lock();

						if (success)

							break;

					}

					sl++;

					if (sl == conf->copies)

						sl = 0;

					}

				} while (!success && sl != r10_bio->read_slot);

				rcu_read_unlock();



				if (success) {

					int start = sl;

					/* write it back and re-read */

					rcu_read_lock();

					while (sl != r10_bio->read_slot) {

						int d;

						if (sl==0)

							sl = conf->copies;

						sl--;

						d = r10_bio->devs[sl].devnum;

						rdev = conf->mirrors[d].rdev;

						rdev = rcu_dereference(conf->mirrors[d].rdev);

						if (rdev &&

						    test_bit(In_sync, &rdev->flags)) {

							atomic_inc(&rdev->nr_pending);

							rcu_read_unlock();

							atomic_add(s, &rdev->corrected_errors);

							if (sync_page_io(rdev->bdev,

									 r10_bio->devs[sl].addr +
@@ -1444,6 +1453,8 @@ static void raid10d(mddev_t *mddev) 
									 s<<9, conf->tmppage, WRITE) == 0)

								/* Well, this device is dead */

								md_error(mddev, rdev);

							rdev_dec_pending(rdev, mddev);

							rcu_read_lock();

						}

					}

					sl = start;
@@ -1453,17 +1464,22 @@ static void raid10d(mddev_t *mddev) 
							sl = conf->copies;

						sl--;

						d = r10_bio->devs[sl].devnum;

						rdev = conf->mirrors[d].rdev;

						rdev = rcu_dereference(conf->mirrors[d].rdev);

						if (rdev &&

						    test_bit(In_sync, &rdev->flags)) {

							atomic_inc(&rdev->nr_pending);

							rcu_read_unlock();

							if (sync_page_io(rdev->bdev,

									 r10_bio->devs[sl].addr +

									 sect + rdev->data_offset,

									 s<<9, conf->tmppage, READ) == 0)

								/* Well, this device is dead */

								md_error(mddev, rdev);

							rdev_dec_pending(rdev, mddev);

							rcu_read_lock();

						}

					}

					rcu_read_unlock();

				} else {

					/* Cannot read from anywhere -- bye bye array */

					md_error(mddev, conf->mirrors[r10_bio->devs[r10_bio->read_slot].devnum].rdev);