Btrfs: calc file extent num_bytes correctly in file clone

num_bytes should be 4096 not 12288.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index b3d249d..028a4b8 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/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,