drbd: Fixed inc_ap_bio()

The condition must be checked after perpare_to_wait(). The old
implementaion could loose wakeup events. Never observed in real
life.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 77ac6765fd576c671eb0f4f9dae9a2f7d60fac89..9a944604939fb0a88294399551244f385c3c0c98 100644 (file)
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -2309,15 +2309,21 @@ static inline int __inc_ap_bio_cond(struct drbd_conf *mdev)
        return 1;
 }
 
-/* I'd like to use wait_event_lock_irq,
- * but I'm not sure when it got introduced,
- * and not sure when it has 3 or 4 arguments */
-static inline void inc_ap_bio(struct drbd_conf *mdev, int count)
+static inline int _inc_ap_bio_cond(struct drbd_conf *mdev, int count)
 {
-       /* compare with after_state_ch,
-        * os.conn != C_WF_BITMAP_S && ns.conn == C_WF_BITMAP_S */
-       DEFINE_WAIT(wait);
+       int rv = 0;
+
+       spin_lock_irq(&mdev->req_lock);
+       rv = __inc_ap_bio_cond(mdev);
+       if (rv)
+               atomic_add(count, &mdev->ap_bio_cnt);
+       spin_unlock_irq(&mdev->req_lock);
+
+       return rv;
+}
 
+static inline void inc_ap_bio(struct drbd_conf *mdev, int count)
+{
        /* we wait here
         *    as long as the device is suspended
         *    until the bitmap is no longer on the fly during connection
@@ -2326,16 +2332,7 @@ static inline void inc_ap_bio(struct drbd_conf *mdev, int count)
         * to avoid races with the reconnect code,
         * we need to atomic_inc within the spinlock. */
 
-       spin_lock_irq(&mdev->req_lock);
-       while (!__inc_ap_bio_cond(mdev)) {
-               prepare_to_wait(&mdev->misc_wait, &wait, TASK_UNINTERRUPTIBLE);
-               spin_unlock_irq(&mdev->req_lock);
-               schedule();
-               finish_wait(&mdev->misc_wait, &wait);
-               spin_lock_irq(&mdev->req_lock);
-       }
-       atomic_add(count, &mdev->ap_bio_cnt);
-       spin_unlock_irq(&mdev->req_lock);
+       wait_event(mdev->misc_wait, _inc_ap_bio_cond(mdev, count));
 }
 
 static inline void dec_ap_bio(struct drbd_conf *mdev)