Re: [PATCH 9/9] btrfs: add RAID 6 recovery for a btrfs filesystem.

[Daniel Kiper]

On Wed, May 16, 2018 at 08:48:19PM +0200, Goffredo Baroncelli wrote:
> Add the RAID 6 recovery, in order to use a RAID 6 filesystem even if some
> disks (up to two) are missing. This code use the old md RAID 6 code already

s/the old md/the md/

> present in grub.
>
> Signed-off-by: Goffredo Baroncelli <address@hidden>
> ---
>  grub-core/fs/btrfs.c | 45 +++++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 40 insertions(+), 5 deletions(-)
>
> diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
> index 5fcaad86f..3d71b954e 100644
> --- a/grub-core/fs/btrfs.c
> +++ b/grub-core/fs/btrfs.c
> @@ -30,6 +30,7 @@
>  #include <grub/i18n.h>
>  #include <grub/btrfs.h>
>  #include <grub/crypto.h>
> +#include <grub/diskfilter.h>
>
>  GRUB_MOD_LICENSE ("GPLv3+");
>
> @@ -695,11 +696,35 @@ rebuild_raid5 (struct raid56_buffer *buffers, 
> grub_uint64_t nstripes,
>                         csize);
>  }
>
> +static grub_err_t
> +raid6_recover_read_buffer (void *data, int disk_nr,
> +                        grub_uint64_t addr __attribute__ ((unused)),
> +                        void *dest, grub_size_t size)
> +{
> +    struct raid56_buffer *buffers = data;
> +
> +    grub_memcpy(dest, buffers[disk_nr].buf, size);

Could we avoid this grub_memcpy() call somehow?

> +    grub_errno = buffers[disk_nr].data_is_valid ? GRUB_ERR_NONE :
> +              GRUB_ERR_READ_ERROR;
> +    return grub_errno;
> +}
> +
> +static void
> +rebuild_raid6 (struct raid56_buffer *buffers, grub_uint64_t nstripes,
> +               grub_uint64_t csize, grub_uint64_t parities_pos, void *dest,
> +               grub_uint64_t stripen)
> +
> +{
> +  grub_raid6_recover_gen (buffers, nstripes, stripen, parities_pos,
> +                          dest, 0, csize, raid6_recover_read_buffer, 0);
> +}
> +
>  static grub_err_t
>  raid56_read_retry (struct grub_btrfs_data *data,
>                  struct grub_btrfs_chunk_item *chunk,
>                  grub_uint64_t stripe_offset, grub_uint64_t stripen,
> -                grub_uint64_t csize, void *buf)
> +                grub_uint64_t csize, void *buf, grub_uint64_t parities_pos)
>  {
>
>    struct raid56_buffer *buffers = NULL;
> @@ -780,6 +805,15 @@ raid56_read_retry (struct grub_btrfs_data *data,
>        ret = GRUB_ERR_READ_ERROR;
>        goto cleanup;
>      }
> +  else if (failed_devices > 2 && (chunk_type & GRUB_BTRFS_CHUNK_TYPE_RAID6))
> +    {
> +      grub_dprintf ("btrfs",
> +                 "not enough disks for raid6: total %" PRIuGRUB_UINT64_T
> +                 ", missing %" PRIuGRUB_UINT64_T "\n",
> +                 nstripes, failed_devices);
> +      ret = GRUB_ERR_READ_ERROR;
> +      goto cleanup;
> +    }
>    else
>      {
>        grub_dprintf ("btrfs",
> @@ -796,7 +830,7 @@ raid56_read_retry (struct grub_btrfs_data *data,
>      }
>    else
>      {
> -      grub_dprintf ("btrfs", "called rebuild_raid6(), NOT IMPLEMENTED\n");
> +      rebuild_raid6 (buffers, nstripes, csize, parities_pos, buf, stripen);
>      }
>
>  cleanup:
> @@ -891,8 +925,9 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, 
> grub_disk_addr_t addr,
>       int is_raid56;
>       grub_uint64_t parities_pos = 0;
>
> -     is_raid56 = !!(grub_le_to_cpu64 (chunk->type) &
> -                    GRUB_BTRFS_CHUNK_TYPE_RAID5);
> +        is_raid56 = !!(grub_le_to_cpu64 (chunk->type) &
> +                    (GRUB_BTRFS_CHUNK_TYPE_RAID5|

Space before "|" please?

> +                     GRUB_BTRFS_CHUNK_TYPE_RAID6));
>
>       if (grub_le_to_cpu64 (chunk->size) <= off)
>         {
> @@ -1089,7 +1124,7 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, 
> grub_disk_addr_t addr,
>                                            csize, buf);
>               if (err != GRUB_ERR_NONE)
>                 err = raid56_read_retry (data, chunk, stripe_offset,
> -                                        stripen, csize, buf);
> +                                        stripen, csize, buf, parities_pos);

I am not sure what is parities_pos and where it is initialized.
If it is a part of earlier patch but it is not used then I think
that it should be a part of this patch.

Daniel