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 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@xxxxxxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxxx>
---
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 adde8a51e020..0eafe7a2070b 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -442,47 +442,6 @@ static struct pgpath *choose_pgpath(struct multipath *m, size_t nr_bytes)
}
/*
- * 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)) {
pr_debug("no path - requeueing\n");
return DM_MAPIO_DELAY_REQUEUE;
}
@@ -581,9 +540,9 @@ 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;
@@ -675,7 +634,7 @@ 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);
@@ -1523,12 +1482,9 @@ 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;
}
@@ -1569,13 +1525,9 @@ 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);
--
2.12.2
--
dm-devel mailing list
dm-devel@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/dm-devel
