1 files changed, 31 insertions, 0 deletions

diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index d72f2fef1cba..9f7ff1cb46ff 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -1226,6 +1226,37 @@ void do_submit(struct work_struct *ws)
                         break;
 
                 wait_event(mdev->al_wait, prepare_al_transaction_nonblock(mdev, &incoming, &pending));
+                /* Maybe more was queued, while we prepared the transaction?
+                 * Try to stuff them into this transaction as well.
+                 * Be strictly non-blocking here, no wait_event, we already
+                 * have something to commit.
+                 * Stop if we don't make any more progres.
+                 */
+                for (;;) {
+                        LIST_HEAD(more_pending);
+                        LIST_HEAD(more_incoming);
+                        bool made_progress;
+
+                        /* It is ok to look outside the lock,
+                         * it's only an optimization anyways */
+                        if (list_empty(&mdev->submit.writes))
+                                break;
+
+                        spin_lock(&mdev->submit.lock);
+                        list_splice_tail_init(&mdev->submit.writes, &more_incoming);
+                        spin_unlock(&mdev->submit.lock);
+
+                        if (list_empty(&more_incoming))
+                                break;
+
+                        made_progress = prepare_al_transaction_nonblock(mdev, &more_incoming, &more_pending);
+
+                        list_splice_tail_init(&more_pending, &pending);
+                        list_splice_tail_init(&more_incoming, &incoming);
+
+                        if (!made_progress)
+                                break;
+                }
                 drbd_al_begin_io_commit(mdev, false);
 
                 list_for_each_entry_safe(req, tmp, &pending, tl_requests) {