Re: [RFC] Add support for BTRFS raid5/6 to GRUB

[Daniel Kiper]

On Tue, Apr 17, 2018 at 09:57:40PM +0200, Goffredo Baroncelli wrote:
> Hi All,
>
> Below you can find a patch to add support for accessing files from
> grub in a RAID5/6 btrfs filesystem. This is a RFC because it is
> missing the support for recovery (i.e. if some devices are missed). In
> the next days (weeks ?) I will extend this patch to support also this
> case.
>
> Comments are welcome.

More or less LGTM. Just a nitpick below... I am happy to take full blown
patch into GRUB if it is ready.

> BR
> G.Baroncelli
>
>
> ---
>
> commit 8c80a1b7c913faf50f95c5c76b4666ed17685666
> Author: Goffredo Baroncelli <address@hidden>
> Date:   Tue Apr 17 21:40:31 2018 +0200
>
>     Add initial support for btrfs raid5/6 chunk
>
> diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
> index be195448d..4c5632acb 100644
> --- a/grub-core/fs/btrfs.c
> +++ b/grub-core/fs/btrfs.c
> @@ -119,6 +119,8 @@ struct grub_btrfs_chunk_item
>  #define GRUB_BTRFS_CHUNK_TYPE_RAID1         0x10
>  #define GRUB_BTRFS_CHUNK_TYPE_DUPLICATED    0x20
>  #define GRUB_BTRFS_CHUNK_TYPE_RAID10        0x40
> +#define GRUB_BTRFS_CHUNK_TYPE_RAID5         0x80
> +#define GRUB_BTRFS_CHUNK_TYPE_RAID6        0x100
>    grub_uint8_t dummy2[0xc];
>    grub_uint16_t nstripes;
>    grub_uint16_t nsubstripes;
> @@ -764,6 +766,39 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, 
> grub_disk_addr_t addr,
>             stripe_offset = low + chunk_stripe_length
>               * high;
>             csize = chunk_stripe_length - low;
> +           break;
> +         }
> +       case GRUB_BTRFS_CHUNK_TYPE_RAID5:
> +       case GRUB_BTRFS_CHUNK_TYPE_RAID6:
> +         {
> +           grub_uint64_t nparities;
> +           grub_uint64_t parity_pos;
> +           grub_uint64_t stripe_nr, high;
> +           grub_uint64_t low;
> +
> +           redundancy = 1;   /* no redundancy for now */
> +
> +           if (grub_le_to_cpu64 (chunk->type) & GRUB_BTRFS_CHUNK_TYPE_RAID5)
> +             {
> +               grub_dprintf ("btrfs", "RAID5\n");
> +               nparities = 1;
> +             }
> +           else
> +             {
> +               grub_dprintf ("btrfs", "RAID6\n");
> +               nparities = 2;
> +             }
> +
> +           stripe_nr = grub_divmod64 (off, chunk_stripe_length, &low);
> +
> +           high = grub_divmod64 (stripe_nr, nstripes - nparities, &stripen);
> +           grub_divmod64 (high+nstripes-nparities, nstripes, &parity_pos);
> +           grub_divmod64 (parity_pos+nparities+stripen, nstripes, &stripen);

Missing spaces around "+" and "-".

Daniel