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authorBart Van Assche <bart.vanassche@sandisk.com>2017-04-27 10:11:24 -0700
committerMike Snitzer <snitzer@redhat.com>2017-04-27 17:08:45 -0400
commitca5beb76c32af33e5be4e01c85c8bd5a067c4543 (patch)
treeda891f5543130b6f7ead7bc135d1d203104471eb /drivers/md
parent7e0d574f2683a2346c978613a72ff07afc89b17a (diff)
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 <bart.vanassche@sandisk.com> Reviewed-by: Hannes Reinecke <hare@suse.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/dm-mpath.c70
1 files 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
@@ -442,47 +442,6 @@ failed:
}
/*
- * 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)
*/
static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
@@ -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);