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>

1 files changed, 14 insertions, 17 deletions

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 77ac6765fd57..9a944604939f 100644
--- 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)