From ca5beb76c32af33e5be4e01c85c8bd5a067c4543 Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Thu, 27 Apr 2017 10:11:24 -0700 Subject: [PATCH] dm mpath: micro-optimize the hot path relative to MPATHF_QUEUE_IF_NO_PATH Instead of checking MPATHF_QUEUE_IF_NO_PATH, MPATHF_SAVED_QUEUE_IF_NO_PATH and the no_flush flag to decide whether or not to push back a request (or bio) if there are no paths available, only clear MPATHF_QUEUE_IF_NO_PATH in queue_if_no_path() if no_flush has not been set. The result is that only a single bit has to be tested in the hot path to decide whether or not a request must be pushed back and also that m->lock does not have to be taken in the hot path. Signed-off-by: Bart Van Assche Reviewed-by: Hannes Reinecke Signed-off-by: Mike Snitzer --- drivers/md/dm-mpath.c | 70 +++++++------------------------------------ 1 file changed, 11 insertions(+), 59 deletions(-) diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c index 8336332bd61f..5cb1beccd1e2 100644 --- a/drivers/md/dm-mpath.c +++ b/drivers/md/dm-mpath.c @@ -441,47 +441,6 @@ failed: return NULL; } -/* - * Check whether bios must be queued in the device-mapper core rather - * than here in the target. - * - * If m->queue_if_no_path and m->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) -{ - return ((test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) != - test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags)) && - dm_noflush_suspending(m->ti)); -} - -static bool must_push_back_rq(struct multipath *m) -{ - bool r; - unsigned long flags; - - spin_lock_irqsave(&m->lock, flags); - r = (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) || - __must_push_back(m)); - spin_unlock_irqrestore(&m->lock, flags); - - return r; -} - -static bool must_push_back_bio(struct multipath *m) -{ - bool r; - unsigned long flags; - - spin_lock_irqsave(&m->lock, flags); - r = __must_push_back(m); - spin_unlock_irqrestore(&m->lock, flags); - - return r; -} - /* * Map cloned requests (request-based multipath) */ @@ -503,7 +462,7 @@ static int multipath_clone_and_map(struct dm_target *ti, struct request *rq, pgpath = choose_pgpath(m, nr_bytes); if (!pgpath) { - if (must_push_back_rq(m)) + if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) return DM_MAPIO_DELAY_REQUEUE; return -EIO; /* Failed */ } else if (test_bit(MPATHF_QUEUE_IO, &m->flags) || @@ -580,9 +539,9 @@ static int __multipath_map_bio(struct multipath *m, struct bio *bio, struct dm_m } if (!pgpath) { - if (!must_push_back_bio(m)) - return -EIO; - return DM_MAPIO_REQUEUE; + if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) + return DM_MAPIO_REQUEUE; + return -EIO; } mpio->pgpath = pgpath; @@ -674,7 +633,7 @@ static int queue_if_no_path(struct multipath *m, bool queue_if_no_path, else clear_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags); } - if (queue_if_no_path) + if (queue_if_no_path || dm_noflush_suspending(m->ti)) set_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags); else clear_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags); @@ -1519,12 +1478,9 @@ static int do_end_io(struct multipath *m, struct request *clone, if (mpio->pgpath) fail_path(mpio->pgpath); - if (!atomic_read(&m->nr_valid_paths)) { - if (!test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) { - if (!must_push_back_rq(m)) - r = -EIO; - } - } + if (atomic_read(&m->nr_valid_paths) == 0 && + !test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) + r = -EIO; return r; } @@ -1565,13 +1521,9 @@ static int do_end_io_bio(struct multipath *m, struct bio *clone, if (mpio->pgpath) fail_path(mpio->pgpath); - if (!atomic_read(&m->nr_valid_paths)) { - if (!test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) { - if (!must_push_back_bio(m)) - return -EIO; - return DM_ENDIO_REQUEUE; - } - } + if (atomic_read(&m->nr_valid_paths) == 0 && + !test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) + return -EIO; /* Queue for the daemon to resubmit */ dm_bio_restore(get_bio_details_from_bio(clone), clone);