1 files changed, 18 insertions, 0 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 7d4f948bc22a..13a17477c4f4 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1502,6 +1502,7 @@ static int btrfs_finish_ordered_io(struct inode *inode, u64 start, u64 end)
         struct btrfs_trans_handle *trans;
         struct btrfs_ordered_extent *ordered_extent;
         struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
+        struct btrfs_path *path;
         int compressed = 0;
         int ret;
 
@@ -1509,6 +1510,23 @@ static int btrfs_finish_ordered_io(struct inode *inode, u64 start, u64 end)
         if (!ret)
                 return 0;
 
+        /*
+         * before we join the transaction, try to do some of our IO.
+         * This will limit the amount of IO that we have to do with
+         * the transaction running.  We're unlikely to need to do any
+         * IO if the file extents are new, the disk_i_size checks
+         * covers the most common case.
+         */
+        if (start < BTRFS_I(inode)->disk_i_size) {
+                path = btrfs_alloc_path();
+                if (path) {
+                        ret = btrfs_lookup_file_extent(NULL, root, path,
+                                                       inode->i_ino,
+                                                       start, 0);
+                        btrfs_free_path(path);
+                }
+        }
+
         trans = btrfs_join_transaction(root, 1);
 
         ordered_extent = btrfs_lookup_ordered_extent(inode, start);