Re: [PATCH] Btrfs: fix wrong superblock generation mismatch while scrubbing superblocks

[Wang Shilong <wangsl.fnst@cn.fujitsu.com>]

On 12/02/2013 10:52 AM, Wang Shilong wrote:
> While scrubbing superblocks we will check every superblock's checksum
> and generation. However, checking superblock's generation may cause
> some problems, this is because tree log sync only flush first superblock
> , while this will cause other superblocks' generation mismatch.
>
> We only report superblock generation mismatch if it is first superblock
> or we make sure we are not doing tree log.
I am sorry, My miss, this is not true, because tree log won't update 
superblock's
generation. I will try to track this issue as soon as possible.

>
> Reported-by: Sebastian Ochmann <ochmann@informatik.uni-bonn.de>
> Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
> Reviewed-by: Miao Xie <miaox@cn.fujitsu.com>
Miao is innocent, he found my fault as soon as possible.
don't blame him.

> ---
>   fs/btrfs/scrub.c | 11 +++++++++--
>   1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
> index 2544805..b29a91f 100644
> --- a/fs/btrfs/scrub.c
> +++ b/fs/btrfs/scrub.c
> @@ -1794,8 +1794,15 @@ static int scrub_checksum_super(struct scrub_block *sblock)
>   	if (sblock->pagev[0]->logical != btrfs_super_bytenr(s))
>   		++fail_cor;
>   
> -	if (sblock->pagev[0]->generation != btrfs_super_generation(s))
> -		++fail_gen;
> +	if (sblock->pagev[0]->generation != btrfs_super_generation(s)) {
> +		/*
> +		 * we only report a generation mismatch if this is first
> +		 * superblock or we can make sure we are not doing tree log.
> +		 */
> +		if (btrfs_super_bytenr(s) == btrfs_sb_offset(0) ||
> +				!root->fs_info->log_root_tree)
> +			++fail_gen;
> +	}
>   
>   	if (memcmp(s->fsid, fs_info->fsid, BTRFS_UUID_SIZE))
>   		++fail_cor;