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

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 318bdae9b56ca9e90c875c17123252b3534d6870..297e260921787f490b63ddf88a9ea5adbdfd82c4 100644 (file)
--- 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)