1 files changed, 17 insertions, 1 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 23a5b0aba00a..2652660e6079 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -138,12 +138,18 @@ int run_scheduled_bios(struct btrfs_device *device)
 {
         struct bio *pending;
         struct backing_dev_info *bdi;
+        struct btrfs_fs_info *fs_info;
         struct bio *tail;
         struct bio *cur;
         int again = 0;
         unsigned long num_run = 0;
+        unsigned long limit;
 
         bdi = device->bdev->bd_inode->i_mapping->backing_dev_info;
+        fs_info = device->dev_root->fs_info;
+        limit = btrfs_async_submit_limit(fs_info);
+        limit = limit * 2 / 3;
+
 loop:
         spin_lock(&device->io_lock);
 
@@ -179,7 +185,11 @@ loop:
                 cur = pending;
                 pending = pending->bi_next;
                 cur->bi_next = NULL;
-                atomic_dec(&device->dev_root->fs_info->nr_async_bios);
+                atomic_dec(&fs_info->nr_async_bios);
+
+                if (atomic_read(&fs_info->nr_async_bios) < limit &&
+                    waitqueue_active(&fs_info->async_submit_wait))
+                        wake_up(&fs_info->async_submit_wait);
 
                 BUG_ON(atomic_read(&cur->bi_cnt) == 0);
                 bio_get(cur);
@@ -2135,6 +2145,7 @@ int schedule_bio(struct btrfs_root *root, struct btrfs_device *device,
                  int rw, struct bio *bio)
 {
         int should_queue = 1;
+        unsigned long limit;
 
         /* don't bother with additional async steps for reads, right now */
         if (!(rw & (1 << BIO_RW))) {
@@ -2171,6 +2182,11 @@ int schedule_bio(struct btrfs_root *root, struct btrfs_device *device,
         if (should_queue)
                 btrfs_queue_worker(&root->fs_info->submit_workers,
                                    &device->work);
+
+        limit = btrfs_async_submit_limit(root->fs_info);
+        wait_event_timeout(root->fs_info->async_submit_wait,
+                           (atomic_read(&root->fs_info->nr_async_bios) < limit),
+                           HZ/10);
         return 0;
 }