diff --git a/[refs] b/[refs]
index c83cde97c4d1..79800a3b7a11 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 4815053aba7f2304055745df820cd74a39fdaab2
+refs/heads/master: d72c0842ff0e71342857723bb65f35b71f57b264
diff --git a/trunk/fs/btrfs/ioctl.c b/trunk/fs/btrfs/ioctl.c
index b3d249d6eba7..028a4b8c12cd 100644
--- a/trunk/fs/btrfs/ioctl.c
+++ b/trunk/fs/btrfs/ioctl.c
@@ -2333,14 +2333,21 @@ static noinline long btrfs_ioctl_clone(struct file *file, unsigned long srcfd,
 
 			if (type == BTRFS_FILE_EXTENT_REG ||
 			    type == BTRFS_FILE_EXTENT_PREALLOC) {
+				/*
+				 *    a  | --- range to clone ---|  b
+				 * | ------------- extent ------------- |
+				 */
+
+				/* substract range b */
+				if (key.offset + datal > off + len)
+					datal = off + len - key.offset;
+
+				/* substract range a */
 				if (off > key.offset) {
 					datao += off - key.offset;
 					datal -= off - key.offset;
 				}
 
-				if (key.offset + datal > off + len)
-					datal = off + len - key.offset;
-
 				ret = btrfs_drop_extents(trans, inode,
 							 new_key.offset,
 							 new_key.offset + datal,