Re: [PATCH md-6.9 04/10] md/raid1-10: add a helper raid1_check_read_range()

[Xiao Ni]

On Thu, Feb 22, 2024 at 4:04 PM Yu Kuai <yukuai1@xxxxxxxxxxxxxxx> wrote:
>
> From: Yu Kuai <yukuai3@xxxxxxxxxx>
>
> The checking and handler of bad blocks appear many timers during
> read_balance() in raid1 and raid10. This helper will be used in later
> patches to simplify read_balance() a lot.
>
> Co-developed-by: Paul Luse <paul.e.luse@xxxxxxxxxxxxxxx>
> Signed-off-by: Paul Luse <paul.e.luse@xxxxxxxxxxxxxxx>
> Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
> ---
>  drivers/md/raid1-10.c | 49 +++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 49 insertions(+)
>
> diff --git a/drivers/md/raid1-10.c b/drivers/md/raid1-10.c
> index 512746551f36..9bc0f0022a6c 100644
> --- a/drivers/md/raid1-10.c
> +++ b/drivers/md/raid1-10.c
> @@ -227,3 +227,52 @@ static inline bool exceed_read_errors(struct mddev *mddev, struct md_rdev *rdev)
>
>         return false;
>  }
> +
> +/**
> + * raid1_check_read_range() - check a given read range for bad blocks,
> + * available read length is returned;
> + * @rdev: the rdev to read;
> + * @this_sector: read position;
> + * @len: read length;
> + *
> + * helper function for read_balance()
> + *
> + * 1) If there are no bad blocks in the range, @len is returned;
> + * 2) If the range are all bad blocks, 0 is returned;
> + * 3) If there are partial bad blocks:
> + *  - If the bad block range starts after @this_sector, the length of first
> + *  good region is returned;
> + *  - If the bad block range starts before @this_sector, 0 is returned and
> + *  the @len is updated to the offset into the region before we get to the
> + *  good blocks;
> + */
> +static inline int raid1_check_read_range(struct md_rdev *rdev,
> +                                        sector_t this_sector, int *len)
> +{
> +       sector_t first_bad;
> +       int bad_sectors;
> +
> +       /* no bad block overlap */
> +       if (!is_badblock(rdev, this_sector, *len, &first_bad, &bad_sectors))
> +               return *len;
> +
> +       /*
> +        * bad block range starts offset into our range so we can return the
> +        * number of sectors before the bad blocks start.
> +        */
> +       if (first_bad > this_sector)
> +               return first_bad - this_sector;
> +
> +       /* read range is fully consumed by bad blocks. */
> +       if (this_sector + *len <= first_bad + bad_sectors)
> +               return 0;
> +
> +       /*
> +        * final case, bad block range starts before or at the start of our
> +        * range but does not cover our entire range so we still return 0 but
> +        * update the length with the number of sectors before we get to the
> +        * good ones.
> +        */
> +       *len = first_bad + bad_sectors - this_sector;
> +       return 0;
> +}
> --
> 2.39.2
>
>

This patch looks good to me.
Reviewed-by: Xiao Ni <xni@xxxxxxxxxx>