Commit a271a89c authored by Mike Snitzer's avatar Mike Snitzer
Browse files

dm mpath: take m->lock spinlock when testing QUEUE_IF_NO_PATH 



Fix multipath_end_io, multipath_end_io_bio and multipath_busy to take
m->lock while testing if MPATHF_QUEUE_IF_NO_PATH bit is set.  These are
all slow-path cases when no paths are available so extra locking isn't a
performance hit.  Correctness matters most.

Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent 69cea0d4

drivers/md/dm-mpath.c

+34 −18
Original line number Diff line number Diff line
@@ -1621,13 +1621,17 @@ static int multipath_end_io(struct dm_target *ti, struct request *clone, 
		if (pgpath)

			fail_path(pgpath);



		if (atomic_read(&m->nr_valid_paths) == 0 &&

		    !must_push_back_rq(m)) {

		if (!atomic_read(&m->nr_valid_paths)) {

			unsigned long flags;

			spin_lock_irqsave(&m->lock, flags);

			if (!must_push_back_rq(m)) {

				if (error == BLK_STS_IOERR)

					dm_report_EIO(m);

				/* complete with the original error */

				r = DM_ENDIO_DONE;

			}

			spin_unlock_irqrestore(&m->lock, flags);

		}

	}



	if (pgpath) {
@@ -1656,16 +1660,20 @@ static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone, 
	if (pgpath)

		fail_path(pgpath);



	if (atomic_read(&m->nr_valid_paths) == 0 &&

	    !test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {

	if (!atomic_read(&m->nr_valid_paths)) {

		spin_lock_irqsave(&m->lock, flags);

		if (!test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {

			if (__must_push_back(m)) {

				r = DM_ENDIO_REQUEUE;

			} else {

				dm_report_EIO(m);

				*error = BLK_STS_IOERR;

			}

			spin_unlock_irqrestore(&m->lock, flags);

			goto done;

		}

		spin_unlock_irqrestore(&m->lock, flags);

	}



	spin_lock_irqsave(&m->lock, flags);

	bio_list_add(&m->queued_bios, clone);
@@ -1962,10 +1970,11 @@ static int multipath_prepare_ioctl(struct dm_target *ti, 
		}

	} else {

		/* No path is available */

		r = -EIO;

		spin_lock_irqsave(&m->lock, flags);

		if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))

			r = -ENOTCONN;

		else

			r = -EIO;

		spin_unlock_irqrestore(&m->lock, flags);

	}



	if (r == -ENOTCONN) {
@@ -2036,8 +2045,15 @@ static int multipath_busy(struct dm_target *ti) 
		return true;



	/* no paths available, for blk-mq: rely on IO mapping to delay requeue */

	if (!atomic_read(&m->nr_valid_paths) && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))

	if (!atomic_read(&m->nr_valid_paths)) {

		unsigned long flags;

		spin_lock_irqsave(&m->lock, flags);

		if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {

			spin_unlock_irqrestore(&m->lock, flags);

			return (m->queue_mode != DM_TYPE_REQUEST_BASED);

		}

		spin_unlock_irqrestore(&m->lock, flags);

	}



	/* Guess which priority_group will be used at next mapping time */

	pg = READ_ONCE(m->current_pg);

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