1 files changed, 10 insertions, 8 deletions

diff --git a/drivers/block/drbd/drbd_actlog.c b/drivers/block/drbd/drbd_actlog.c
index 933404e6ba28..aeb483daea06 100644
--- a/drivers/block/drbd/drbd_actlog.c
+++ b/drivers/block/drbd/drbd_actlog.c
@@ -212,13 +212,22 @@ void drbd_al_begin_io(struct drbd_conf *mdev, struct drbd_interval *i)
         unsigned first = i->sector >> (AL_EXTENT_SHIFT-9);
         unsigned last = (i->sector + (i->size >> 9) - 1) >> (AL_EXTENT_SHIFT-9);
         unsigned enr;
+        bool locked = false;
+
 
         D_ASSERT(atomic_read(&mdev->local_cnt) > 0);
 
         for (enr = first; enr <= last; enr++)
                 wait_event(mdev->al_wait, _al_get(mdev, enr) != NULL);
 
-        if (mdev->act_log->pending_changes) {
+        /* Serialize multiple transactions.
+         * This uses test_and_set_bit, memory barrier is implicit.
+         */
+        wait_event(mdev->al_wait,
+                        mdev->act_log->pending_changes == 0 ||
+                        (locked = lc_try_lock_for_transaction(mdev->act_log)));
+
+        if (locked) {
                 /* drbd_al_write_transaction(mdev,al_ext,enr);
                  * recurses into generic_make_request(), which
                  * disallows recursion, bios being serialized on the
@@ -226,13 +235,6 @@ void drbd_al_begin_io(struct drbd_conf *mdev, struct drbd_interval *i)
                  * we have to delegate updates to the activity log
                  * to the worker thread. */
 
-                /* Serialize multiple transactions.
-                 * This uses test_and_set_bit, memory barrier is implicit.
-                 * Optimization potential:
-                 * first check for transaction number > old transaction number,
-                 * so not all waiters have to lock/unlock.  */
-                wait_event(mdev->al_wait, lc_try_lock_for_transaction(mdev->act_log));
-
                 /* Double check: it may have been committed by someone else,
                  * while we have been waiting for the lock. */
                 if (mdev->act_log->pending_changes) {