Re: [PATCH v2 4/4] btrfs: Do super block verification before writing it to disk

[David Sterba <dsterba@suse.cz>]

On Tue, Apr 24, 2018 at 12:48:09PM +0800, Qu Wenruo wrote:
> -static int btrfs_validate_super(struct btrfs_fs_info *fs_info)
> +/*
> + * Check the validation of btrfs super block.
> + *
> + * @sb:			super block to check
> + * @super_mirror:	the super block number to check its bytenr.
> + * 			0 means the primary (1st) sb, 1 and 2 means 2nd and
> + * 			3rd backup sb, while -1 means to skip bytenr check.

Please format the values like:

/*
 * Check the validity of btrfs super block
 *
 * @sb:                        super block to check
 * @super_mirror:      the super block number to check its bytenr:
 *                     0 means the primary (1st) sb,
 *                     1 and 2 means 2nd and 3rd backup copy
 *                     -1 means to skip bytenr check
 */

> + */
> +static int btrfs_validate_super(struct btrfs_fs_info *fs_info,
> +				struct btrfs_super_block *sb,
> +				int super_mirror)
>  {
> -	struct btrfs_super_block *sb = fs_info->super_copy;
>  	u64 nodesize = btrfs_super_nodesize(sb);
>  	u64 sectorsize = btrfs_super_sectorsize(sb);
>  	int ret = 0;
> @@ -4088,9 +4109,10 @@ static int btrfs_validate_super(struct btrfs_fs_info *fs_info)
>  		ret = -EINVAL;
>  	}
>  
> -	if (btrfs_super_bytenr(sb) != BTRFS_SUPER_INFO_OFFSET) {
> -		btrfs_err(fs_info, "super offset mismatch %llu != %u",
> -			  btrfs_super_bytenr(sb), BTRFS_SUPER_INFO_OFFSET);
> +	if (super_mirror >= 0 && btrfs_super_bytenr(sb) !=
> +	    btrfs_sb_offset(super_mirror)) {

The preferred condition split is after the operators, not in the middle
of the expression. Like this:

	if (super_mirror >= 0 &&
	    btrfs_super_bytenr(sb) != btrfs_sb_offset(super_mirror)) {