md/raid5: STRIPE_ACTIVE has lock semantics, add barriers

All updates that occur under STRIPE_ACTIVE should be globally visible
when STRIPE_ACTIVE clears.  test_and_set_bit() implies a barrier, but
clear_bit() does not.

This is suitable for 3.1-stable.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Cc: stable@kernel.org

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 318bdae9b56c..297e26092178 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3110,7 +3110,7 @@ static void handle_stripe(struct stripe_head *sh)
         struct r5dev *pdev, *qdev;
 
         clear_bit(STRIPE_HANDLE, &sh->state);
-        if (test_and_set_bit(STRIPE_ACTIVE, &sh->state)) {
+        if (test_and_set_bit_lock(STRIPE_ACTIVE, &sh->state)) {
                 /* already being handled, ensure it gets handled
                  * again when current action finishes */
                 set_bit(STRIPE_HANDLE, &sh->state);
@@ -3375,7 +3375,7 @@ finish:
 
         return_io(s.return_bi);
 
-        clear_bit(STRIPE_ACTIVE, &sh->state);
+        clear_bit_unlock(STRIPE_ACTIVE, &sh->state);
 }
 
 static void raid5_activate_delayed(struct r5conf *conf)