md/raid5: use atomic_dec_return() instead of atomic_dec() and atomic_read().

Signed-off-by: majianpeng <majianpeng@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 3 insertions, 4 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 3f55145ff224..99b2bbf8b5d8 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -208,11 +208,10 @@ static void __release_stripe(struct r5conf *conf, struct stripe_head *sh)
                         md_wakeup_thread(conf->mddev->thread);
                 } else {
                         BUG_ON(stripe_operations_active(sh));
-                        if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
-                                atomic_dec(&conf->preread_active_stripes);
-                                if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD)
+                        if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
+                                if (atomic_dec_return(&conf->preread_active_stripes)
+                                    < IO_THRESHOLD)
                                         md_wakeup_thread(conf->mddev->thread);
-                        }
                         atomic_dec(&conf->active_stripes);
                         if (!test_bit(STRIPE_EXPANDING, &sh->state)) {
                                 list_add_tail(&sh->lru, &conf->inactive_list);