Btrfs: add dummy extent if dst offset excceeds file end in

You can see there's no file extent with range [0, 4096]. Check this by
btrfsck:

 # btrfsck /dev/sda7
 root 5 inode 258 errors 100
 ...

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

1 files changed, 6 insertions, 0 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 028a4b8c12cd..63b4de1626d2 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2228,6 +2228,12 @@ static noinline long btrfs_ioctl_clone(struct file *file, unsigned long srcfd,
             !IS_ALIGNED(destoff, bs))
                 goto out_unlock;
 
+        if (destoff > inode->i_size) {
+                ret = btrfs_cont_expand(inode, inode->i_size, destoff);
+                if (ret)
+                        goto out_unlock;
+        }
+
         /* do any pending delalloc/csum calc on src, one way or
            another, and lock file content */
         while (1) {