The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From c1fd0abee0d52eb7e2871194b6c79d54792f515f Mon Sep 17 00:00:00 2001

From: Mike Snitzer snitzer@redhat.com Date: Thu, 7 Dec 2017 22:42:27 -0500 Subject: [PATCH] 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: Mike Snitzer snitzer@redhat.com

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c index 35a2a2fa477f..f7810cc869ac 100644 --- a/drivers/md/dm-mpath.c +++ b/drivers/md/dm-mpath.c @@ -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)) { - dm_report_EIO(m); - *error = BLK_STS_IOERR; + if (must_push_back_bio(m)) { + r = DM_ENDIO_REQUEUE; + } else { + dm_report_EIO(m); + *error = BLK_STS_IOERR; + } goto done; }