Re: [PATCH 2/9] btrfs-progs: use blocks_nr to determine the super used bytes

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

On 2021/8/21 上午3:11, Josef Bacik wrote:
> We were setting the superblock's used bytes to a static number.  However
> the number of blocks we have to write has the correct used size, so just
> add up the total number of blocks we're allocating as we determine their
> offsets.  This value will be used later which is why I'm calculating it
> this way instead of doing the math to set the bytes_super specifically.
>
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>

Reviewed-by: Qu Wenruo <wqu@suse.com>

Getting rid of an hardcoded immediate number is always a good thing.

Thanks,
Qu
> ---
>   mkfs/common.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/mkfs/common.c b/mkfs/common.c
> index e9ff529a..8902d39e 100644
> --- a/mkfs/common.c
> +++ b/mkfs/common.c
> @@ -162,6 +162,7 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
>   	u64 ref_root;
>   	u32 array_size;
>   	u32 item_size;
> +	u64 total_used = 0;
>   	int skinny_metadata = !!(cfg->features &
>   				 BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA);
>   	u64 num_bytes;
> @@ -207,6 +208,7 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
>   		if (blk == MKFS_SUPER_BLOCK)
>   			continue;
>   		cfg->blocks[blk] = system_group_offset + cfg->nodesize * i;
> +		total_used += cfg->nodesize;
>   	}
>
>   	btrfs_set_super_bytenr(&super, cfg->blocks[MKFS_SUPER_BLOCK]);
> @@ -216,7 +218,7 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
>   	btrfs_set_super_root(&super, cfg->blocks[MKFS_ROOT_TREE]);
>   	btrfs_set_super_chunk_root(&super, cfg->blocks[MKFS_CHUNK_TREE]);
>   	btrfs_set_super_total_bytes(&super, num_bytes);
> -	btrfs_set_super_bytes_used(&super, 6 * cfg->nodesize);
> +	btrfs_set_super_bytes_used(&super, total_used);
>   	btrfs_set_super_sectorsize(&super, cfg->sectorsize);
>   	super.__unused_leafsize = cpu_to_le32(cfg->nodesize);
>   	btrfs_set_super_nodesize(&super, cfg->nodesize);
>