Commit c1fd0abe authored by Mike Snitzer's avatar Mike Snitzer
Browse files

dm mpath: fix bio-based multipath queue_if_no_path handling 



Commit ca5beb76 ("dm mpath: micro-optimize the hot path relative to
MPATHF_QUEUE_IF_NO_PATH") caused bio-based DM-multipath to fail mptest's
"test_02_sdev_delete".

Restoring the logic that existed prior to commit ca5beb76 fixes this
bio-based DM-multipath regression.  Also verified all mptest tests pass
with request-based DM-multipath.

This commit effectively reverts commit ca5beb76 -- but it does so
without reintroducing the need to take the m->lock spinlock in
must_push_back_{rq,bio}.

Fixes: ca5beb76 ("dm mpath: micro-optimize the hot path relative to MPATHF_QUEUE_IF_NO_PATH")
Cc: stable@vger.kernel.org # 4.12+
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent 7e6358d2

drivers/md/dm-mpath.c

+42 −7
Original line number Diff line number Diff line
@@ -457,6 +457,38 @@ do { \ 
		 dm_noflush_suspending((m)->ti));			\

} while (0)



/*

 * Check whether bios must be queued in the device-mapper core rather

 * than here in the target.

 *

 * If MPATHF_QUEUE_IF_NO_PATH and MPATHF_SAVED_QUEUE_IF_NO_PATH hold

 * the same value then we are not between multipath_presuspend()

 * and multipath_resume() calls and we have no need to check

 * for the DMF_NOFLUSH_SUSPENDING flag.

 */

static bool __must_push_back(struct multipath *m, unsigned long flags)

{

	return ((test_bit(MPATHF_QUEUE_IF_NO_PATH, &flags) !=

		 test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &flags)) &&

		dm_noflush_suspending(m->ti));

}



/*

 * Following functions use READ_ONCE to get atomic access to

 * all m->flags to avoid taking spinlock

 */

static bool must_push_back_rq(struct multipath *m)

{

	unsigned long flags = READ_ONCE(m->flags);

	return test_bit(MPATHF_QUEUE_IF_NO_PATH, &flags) || __must_push_back(m, flags);

}



static bool must_push_back_bio(struct multipath *m)

{

	unsigned long flags = READ_ONCE(m->flags);

	return __must_push_back(m, flags);

}



/*

 * Map cloned requests (request-based multipath)

 */
@@ -478,7 +510,7 @@ static int multipath_clone_and_map(struct dm_target *ti, struct request *rq, 
		pgpath = choose_pgpath(m, nr_bytes);



	if (!pgpath) {

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

		if (must_push_back_rq(m))

			return DM_MAPIO_DELAY_REQUEUE;

		dm_report_EIO(m);	/* Failed */

		return DM_MAPIO_KILL;
@@ -553,7 +585,7 @@ static int __multipath_map_bio(struct multipath *m, struct bio *bio, struct dm_m 
	}



	if (!pgpath) {

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

		if (must_push_back_bio(m))

			return DM_MAPIO_REQUEUE;

		dm_report_EIO(m);

		return DM_MAPIO_KILL;
@@ -651,8 +683,7 @@ static int queue_if_no_path(struct multipath *m, bool queue_if_no_path, 
	assign_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags,

		   (save_old_value && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) ||

		   (!save_old_value && queue_if_no_path));

	assign_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags,

		   queue_if_no_path || dm_noflush_suspending(m->ti));

	assign_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags, queue_if_no_path);

	spin_unlock_irqrestore(&m->lock, flags);



	if (!queue_if_no_path) {
@@ -1486,7 +1517,7 @@ static int multipath_end_io(struct dm_target *ti, struct request *clone, 
			fail_path(pgpath);



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

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

		    !must_push_back_rq(m)) {

			if (error == BLK_STS_IOERR)

				dm_report_EIO(m);

			/* complete with the original error */
@@ -1521,8 +1552,12 @@ static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone, 


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

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

		if (must_push_back_bio(m)) {

			r = DM_ENDIO_REQUEUE;

		} else {

			dm_report_EIO(m);

			*error = BLK_STS_IOERR;

		}

		goto done;

	}

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