Re: [PATCH 2/2] Btrfs: scrub raid56 stripes in the right way

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

Oops, this patch is not working right, please ignore this one,
i will send a v2.

Thanks,
Wang
On 03/24/2014 05:58 PM, Wang Shilong wrote:
> Steps to reproduce:
>   # mkfs.btrfs -f /dev/sda[8-11] -m raid5 -d raid5
>   # mount /dev/sda8 /mnt
>   # btrfs scrub start -BR /mnt
>   # echo $? <--unverified errors make return value be 3
>
> This is because we don't setup right mapping between physical
> and logical address for raid56, which makes checksum mismatch.
> But we will find everthing is fine later when rechecking using
> btrfs_map_block().
>
> This patch fixed the problem by settuping right mappings and
> we only verify data stripes' checksums.
>
> Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
> ---
>   fs/btrfs/scrub.c | 33 +++++++++++++++++++++++++--------
>   1 file changed, 25 insertions(+), 8 deletions(-)
>
> diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
> index db21a13..4182b44a 100644
> --- a/fs/btrfs/scrub.c
> +++ b/fs/btrfs/scrub.c
> @@ -2267,16 +2267,12 @@ static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
>   	u64 extent_logical;
>   	u64 extent_physical;
>   	u64 extent_len;
> +	u64 stripe_nr;
> +	u64 tmp;
> +	int stripe_index;
>   	struct btrfs_device *extent_dev;
>   	int extent_mirror_num;
> -	int stop_loop;
> -
> -	if (map->type & (BTRFS_BLOCK_GROUP_RAID5 |
> -			 BTRFS_BLOCK_GROUP_RAID6)) {
> -		if (num >= nr_data_stripes(map)) {
> -			return 0;
> -		}
> -	}
> +	int stop_loop = 0;
>   
>   	nstripes = length;
>   	offset = 0;
> @@ -2296,6 +2292,14 @@ static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
>   	} else if (map->type & BTRFS_BLOCK_GROUP_DUP) {
>   		increment = map->stripe_len;
>   		mirror_num = num % map->num_stripes + 1;
> +	} else if (map->type & (BTRFS_BLOCK_GROUP_RAID5 |
> +				BTRFS_BLOCK_GROUP_RAID6)) {
> +		if (num < nr_data_stripes(map))
> +			offset = num * map->stripe_len;
> +		else
> +			offset = (nr_data_stripes(map) - 1) * map->stripe_len;
> +		increment = map->stripe_len * nr_data_stripes(map);
> +		mirror_num = 1;
>   	} else {
>   		increment = map->stripe_len;
>   		mirror_num = 1;
> @@ -2361,6 +2365,18 @@ static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
>   	logic_end = logical + increment * nstripes;
>   	ret = 0;
>   	while (logical < logic_end) {
> +		/* skip parity */
> +		if (map->type & (BTRFS_BLOCK_GROUP_RAID5 |
> +				BTRFS_BLOCK_GROUP_RAID6)) {
> +			stripe_nr = logical - base;
> +			do_div(stripe_nr, map->stripe_len);
> +
> +			stripe_index = do_div(stripe_nr, nr_data_stripes(map));
> +			tmp = stripe_nr + stripe_index;
> +			stripe_index = do_div(tmp, map->num_stripes);
> +			if (stripe_index != num)
> +				goto skip;
> +		}
>   		/*
>   		 * canceled?
>   		 */
> @@ -2521,6 +2537,7 @@ next:
>   			path->slots[0]++;
>   		}
>   		btrfs_release_path(path);
> +skip:
>   		logical += increment;
>   		physical += map->stripe_len;
>   		spin_lock(&sctx->stat_lock);