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, 16 insertions, 0 deletions

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 9be4fd2db0f4..5942b9384088 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -2555,6 +2555,7 @@ static int check_dev_super(struct btrfs_device *dev)
 {
 	struct btrfs_fs_info *fs_info = dev->fs_info;
 	struct btrfs_super_block *sb;
+	u16 csum_type;
 	int ret = 0;
 
 	/* This should be called with fs still frozen. */
@@ -2569,6 +2570,21 @@ static int check_dev_super(struct btrfs_device *dev)
 	if (IS_ERR(sb))
 		return PTR_ERR(sb);
 
+	/* Verify the checksum. */
+	csum_type = btrfs_super_csum_type(sb);
+	if (csum_type != btrfs_super_csum_type(fs_info->super_copy)) {
+		btrfs_err(fs_info, "csum type changed, has %u expect %u",
+			  csum_type, btrfs_super_csum_type(fs_info->super_copy));
+		ret = -EUCLEAN;
+		goto out;
+	}
+
+	if (btrfs_check_super_csum(fs_info, sb)) {
+		btrfs_err(fs_info, "csum for on-disk super block no longer matches");
+		ret = -EUCLEAN;
+		goto out;
+	}
+
 	/* Btrfs_validate_super() includes fsid check against super->fsid. */
 	ret = btrfs_validate_super(fs_info, sb, 0);
 	if (ret < 0)