Btrfs: Rewrite btrfs_drop_extents

Rewrite btrfs_drop_extents by using btrfs_duplicate_item, so we can
avoid calling lock_extent within transaction.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index cdbb054..a1a8db8 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1027,8 +1027,7 @@
 	BUG_ON(!trans);
 
 	/* punch hole in destination first */
-	btrfs_drop_extents(trans, root, inode, off, off + len,
-			   off + len, 0, &hint_byte, 1);
+	btrfs_drop_extents(trans, inode, off, off + len, &hint_byte, 1);
 
 	/* clone data */
 	key.objectid = src->i_ino;