btrfs: fix lost i_size update after cloning inline extent

When not using the NO_HOLES feature we were not marking the destination's
file range as written after cloning an inline extent into it. This can
lead to a data loss if the current destination file size is smaller than
the source file's size.

Example:

  $ mkfs.btrfs -f -O ^no-holes /dev/sdc
  $ mount /mnt/sdc /mnt

  $ echo "hello world" > /mnt/foo
  $ cp --reflink=always /mnt/foo /mnt/bar
  $ rm -f /mnt/foo
  $ umount /mnt

  $ mount /mnt/sdc /mnt
  $ cat /mnt/bar
  $
  $ stat -c %s /mnt/bar
  0

  # -> the file is empty, since we deleted foo, the data lost is forever

Fix that by calling btrfs_inode_set_file_extent_range() after cloning an
inline extent.

A test case for fstests will follow soon.

Link: https://lore.kernel.org/linux-btrfs/20200404193846.GA432065@latitude/
Reported-by: Johannes Hirte <johannes.hirte@datenkhaos.de>
Fixes: 9ddc959e802bf ("btrfs: use the file extent tree infrastructure")
Tested-by: Johannes Hirte <johannes.hirte@datenkhaos.de>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/reflink.c b/fs/btrfs/reflink.c
index d197314..040009d 100644 (file)
--- a/fs/btrfs/reflink.c
+++ b/fs/btrfs/reflink.c
@@ -264,6 +264,7 @@ copy_inline_extent:
                            size);
        inode_add_bytes(dst, datal);
        set_bit(BTRFS_INODE_NEEDS_FULL_SYNC, &BTRFS_I(dst)->runtime_flags);
+       ret = btrfs_inode_set_file_extent_range(BTRFS_I(dst), 0, aligned_end);
 out:
        if (!ret && !trans) {
                /*