2 files changed, 13 insertions, 0 deletions

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index e9d594fd12cb..800aec7927de 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -463,6 +463,7 @@ out:
  */
 static void loop_add_bio(struct loop_device *lo, struct bio *bio)
 {
+        lo->lo_bio_count++;
         bio_list_add(&lo->lo_bio_list, bio);
 }
 
@@ -471,6 +472,7 @@ static void loop_add_bio(struct loop_device *lo, struct bio *bio)
  */
 static struct bio *loop_get_bio(struct loop_device *lo)
 {
+        lo->lo_bio_count--;
         return bio_list_pop(&lo->lo_bio_list);
 }
 
@@ -489,6 +491,10 @@ static void loop_make_request(struct request_queue *q, struct bio *old_bio)
                 goto out;
         if (unlikely(rw == WRITE && (lo->lo_flags & LO_FLAGS_READ_ONLY)))
                 goto out;
+        if (lo->lo_bio_count >= q->nr_congestion_on)
+                wait_event_lock_irq(lo->lo_req_wait,
+                                    lo->lo_bio_count < q->nr_congestion_off,
+                                    lo->lo_lock);
         loop_add_bio(lo, old_bio);
         wake_up(&lo->lo_event);
         spin_unlock_irq(&lo->lo_lock);
@@ -546,6 +552,8 @@ static int loop_thread(void *data)
                         continue;
                 spin_lock_irq(&lo->lo_lock);
                 bio = loop_get_bio(lo);
+                if (lo->lo_bio_count < lo->lo_queue->nr_congestion_off)
+                        wake_up(&lo->lo_req_wait);
                 spin_unlock_irq(&lo->lo_lock);
 
                 BUG_ON(!bio);
@@ -873,6 +881,7 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
         lo->transfer = transfer_none;
         lo->ioctl = NULL;
         lo->lo_sizelimit = 0;
+        lo->lo_bio_count = 0;
         lo->old_gfp_mask = mapping_gfp_mask(mapping);
         mapping_set_gfp_mask(mapping, lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
 
@@ -1660,6 +1669,7 @@ static int loop_add(struct loop_device **l, int i)
         lo->lo_number           = i;
         lo->lo_thread           = NULL;
         init_waitqueue_head(&lo->lo_event);
+        init_waitqueue_head(&lo->lo_req_wait);
         spin_lock_init(&lo->lo_lock);
         disk->major             = LOOP_MAJOR;
         disk->first_minor       = i << part_shift;
diff --git a/include/linux/loop.h b/include/linux/loop.h
index 6492181bcb1d..460b60fa7adf 100644
--- a/include/linux/loop.h
+++ b/include/linux/loop.h
@@ -53,10 +53,13 @@ struct loop_device {
 
         spinlock_t              lo_lock;
         struct bio_list         lo_bio_list;
+        unsigned int            lo_bio_count;
         int                     lo_state;
         struct mutex            lo_ctl_mutex;
         struct task_struct      *lo_thread;
         wait_queue_head_t       lo_event;
+        /* wait queue for incoming requests */
+        wait_queue_head_t       lo_req_wait;
 
         struct request_queue    *lo_queue;
         struct gendisk          *lo_disk;