Re: [PATCH 1/7] Add support for reading a filesystem with a raid5 or raid6 profile.

[Daniel Kiper]

On Tue, Apr 24, 2018 at 09:13:10PM +0200, Goffredo Baroncelli wrote:
> Signed-off-by: Goffredo Baroncelli <address@hidden>
> ---
>  grub-core/fs/btrfs.c | 32 ++++++++++++++++++++++++++++++++
>  1 file changed, 32 insertions(+)
>
> diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
> index be195448d..b0032ea46 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

#define GRUB_BTRFS_CHUNK_TYPE_RAID5         0x80
#define GRUB_BTRFS_CHUNK_TYPE_RAID6         0x100
 Please start in one column...     ---->    ^^^^^

>    grub_uint8_t dummy2[0xc];
>    grub_uint16_t nstripes;
>    grub_uint16_t nsubstripes;
> @@ -764,6 +766,36 @@ 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 stripe_nr, high;
> +           grub_uint64_t low;

Could you define all in one line?

> +           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);

This is clear for me...

> +           high = grub_divmod64 (stripe_nr, nstripes - nparities, &stripen);
> +           grub_divmod64 (high + stripen, nstripes, &stripen);

... but not these two. Could you enlighten me?

> +           stripe_offset = low + chunk_stripe_length * high;

???

> +           csize = chunk_stripe_length - low;

Chunk size to read?

Daniel