1 files changed, 24 insertions, 0 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 141104835952..6dbee46240c5 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -141,6 +141,8 @@ struct cfq_queue {
         int queued[2];
         /* currently allocated requests */
         int allocated[2];
+        /* pending metadata requests */
+        int meta_pending;
         /* fifo list of requests in sort_list */
         struct list_head fifo;
 
@@ -248,6 +250,10 @@ cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2)
                 return rq1;
         else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
                 return rq2;
+        if (rq_is_meta(rq1) && !rq_is_meta(rq2))
+                return rq1;
+        else if (rq_is_meta(rq2) && !rq_is_meta(rq1))
+                return rq2;
 
         s1 = rq1->sector;
         s2 = rq2->sector;
@@ -510,6 +516,11 @@ static void cfq_remove_request(struct request *rq)
 
         list_del_init(&rq->queuelist);
         cfq_del_rq_rb(rq);
+
+        if (rq_is_meta(rq)) {
+                WARN_ON(!cfqq->meta_pending);
+                cfqq->meta_pending--;
+        }
 }
 
 static int
@@ -1527,8 +1538,18 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
          */
         if (new_cfqq->slice_left < cfqd->cfq_slice_idle)
                 return 0;
+        /*
+         * if the new request is sync, but the currently running queue is
+         * not, let the sync request have priority.
+         */
         if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
                 return 1;
+        /*
+         * So both queues are sync. Let the new request get disk time if
+         * it's a metadata request and the current queue is doing regular IO.
+         */
+        if (rq_is_meta(rq) && !cfqq->meta_pending)
+                return 1;
 
         return 0;
 }
@@ -1564,6 +1585,9 @@ cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 {
         struct cfq_io_context *cic = RQ_CIC(rq);
 
+        if (rq_is_meta(rq))
+                cfqq->meta_pending++;
+
         /*
          * check if this request is a better next-serve candidate)) {
          */