btrfs: make thaw time super block check to also verify checksum

Previous commit a05d3c915314 ("btrfs: check superblock to ensure the fs
was not modified at thaw time") only checks the content of the super
block, but it doesn't really check if the on-disk super block has a
matching checksum.

This patch will add the checksum verification to thaw time superblock
verification.

This involves the following extra changes:

- Export btrfs_check_super_csum()
  As we need to call it in super.c.

- Change the argument list of btrfs_check_super_csum()
  Instead of passing a char *, directly pass struct btrfs_super_block *
  pointer.

- Verify that our checksum type didn't change before checking the
  checksum value, like it's done at mount time

Fixes: a05d3c915314 ("btrfs: check superblock to ensure the fs was not modified at thaw time")
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h
index c67c15d4d20b..9fa923e005a3 100644
--- a/fs/btrfs/disk-io.h
+++ b/fs/btrfs/disk-io.h
@@ -42,6 +42,8 @@ struct extent_buffer *btrfs_find_create_tree_block(
 void btrfs_clean_tree_block(struct extent_buffer *buf);
 void btrfs_clear_oneshot_options(struct btrfs_fs_info *fs_info);
 int btrfs_start_pre_rw_mount(struct btrfs_fs_info *fs_info);
+int btrfs_check_super_csum(struct btrfs_fs_info *fs_info,
+			   const struct btrfs_super_block *disk_sb);
 int __cold open_ctree(struct super_block *sb,
 	       struct btrfs_fs_devices *fs_devices,
 	       char *options);