Merge branch 'master'

1 files changed, 15 insertions, 2 deletions

diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index e5041a02e21f..eac48bec1479 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -1732,8 +1732,21 @@ void blk_run_queue(struct request_queue *q)
 
         spin_lock_irqsave(q->queue_lock, flags);
         blk_remove_plug(q);
-        if (!elv_queue_empty(q))
-                q->request_fn(q);
+
+        /*
+         * Only recurse once to avoid overrunning the stack, let the unplug
+         * handling reinvoke the handler shortly if we already got there.
+         */
+        if (!elv_queue_empty(q)) {
+                if (!test_and_set_bit(QUEUE_FLAG_REENTER, &q->queue_flags)) {
+                        q->request_fn(q);
+                        clear_bit(QUEUE_FLAG_REENTER, &q->queue_flags);
+                } else {
+                        blk_plug_device(q);
+                        kblockd_schedule_work(&q->unplug_work);
+                }
+        }
+
         spin_unlock_irqrestore(q->queue_lock, flags);
 }
 EXPORT_SYMBOL(blk_run_queue);