Re: [PATCH 7/9] btrfs: Add support for recovery for a RAID 5 btrfs profiles.

[Daniel Kiper]

On Thu, Sep 27, 2018 at 08:35:02PM +0200, Goffredo Baroncelli wrote:
> From: Goffredo Baroncelli <address@hidden>
>
> Add support for recovery for a RAID 5 btrfs profile. In addition
> it is added some code as preparatory work for RAID 6 recovery code.
>
> Signed-off-by: Goffredo Baroncelli <address@hidden>
> ---
>  grub-core/fs/btrfs.c | 160 +++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 155 insertions(+), 5 deletions(-)
>
> diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
> index 554f350c5..db8df0eea 100644
> --- a/grub-core/fs/btrfs.c
> +++ b/grub-core/fs/btrfs.c
> @@ -29,6 +29,7 @@
>  #include <minilzo.h>
>  #include <grub/i18n.h>
>  #include <grub/btrfs.h>
> +#include <grub/crypto.h>
>
>  GRUB_MOD_LICENSE ("GPLv3+");
>
> @@ -665,6 +666,139 @@ btrfs_read_from_chunk (struct grub_btrfs_data *data,
>      return err;
>  }
>
> +struct raid56_buffer {
> +  void *buf;
> +  int  data_is_valid;
> +};
> +
> +static void
> +rebuild_raid5 (char *dest, struct raid56_buffer *buffers,
> +            grub_uint64_t nstripes, grub_uint64_t csize)
> +{
> +  grub_uint64_t i;
> +  int first;
> +
> +  for(i = 0; buffers[i].data_is_valid && i < nstripes; i++);
> +
> +  if (i == nstripes)
> +    {
> +      grub_dprintf ("btrfs", "called rebuild_raid5(), but all disks are 
> OK\n");
> +      return;
> +    }
> +
> +  grub_dprintf ("btrfs", "rebuilding RAID 5 stripe #%" PRIuGRUB_UINT64_T 
> "\n", i);
> +
> +  for (i = 0, first = 1; i < nstripes; i++)
> +    {
> +      if (!buffers[i].data_is_valid)
> +     continue;
> +
> +      if (first) {
> +     grub_memcpy(dest, buffers[i].buf, csize);
> +     first = 0;
> +      } else
> +     grub_crypto_xor (dest, dest, buffers[i].buf, csize);
> +
> +    }
> +}
> +
> +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 csize, void *buf)
> +{
> +  struct raid56_buffer *buffers;
> +  grub_uint64_t nstripes = grub_le_to_cpu16 (chunk->nstripes);
> +  grub_uint64_t chunk_type = grub_le_to_cpu64 (chunk->type);
> +  grub_err_t ret = GRUB_ERR_OUT_OF_MEMORY;
> +  grub_uint64_t i, failed_devices;
> +
> +  buffers = grub_zalloc (sizeof(*buffers) * nstripes);
> +  if (!buffers)
> +    goto cleanup;
> +
> +  for (i = 0; i < nstripes; i++)
> +    {
> +      buffers[i].buf = grub_zalloc (csize);
> +      if (!buffers[i].buf)
> +     goto cleanup;
> +    }
> +
> +  for (failed_devices = 0, i = 0; i < nstripes; i++)
> +    {
> +      struct grub_btrfs_chunk_stripe *stripe;
> +      grub_disk_addr_t paddr;
> +      grub_device_t dev;
> +      grub_err_t err;
> +
> +      stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1) + i;

I think that "chunk + 1" requires short comment why...

> +
> +      paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
> +      grub_dprintf ("btrfs", "reading paddr %" PRIxGRUB_UINT64_T
> +                    " from stripe ID %" PRIxGRUB_UINT64_T "\n", paddr,
> +                    stripe->device_id);
> +
> +      dev = find_device (data, stripe->device_id);
> +      if (!dev)
> +     {
> +       buffers[i].data_is_valid = 0;
> +       grub_dprintf ("btrfs", "stripe %" PRIuGRUB_UINT64_T " FAILED (dev ID 
> %"
> +                     PRIxGRUB_UINT64_T ")\n", i, stripe->device_id);
> +       failed_devices++;
> +       continue;
> +     }
> +
> +      err = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
> +                         paddr & (GRUB_DISK_SECTOR_SIZE - 1),
> +                         csize, buffers[i].buf);
> +      if (err == GRUB_ERR_NONE)
> +     {
> +       buffers[i].data_is_valid = 1;
> +       grub_dprintf ("btrfs", "stripe %" PRIuGRUB_UINT64_T " Ok (dev ID %"
> +                     PRIxGRUB_UINT64_T ")\n", i, stripe->device_id);
> +     }
> +      else
> +     {
> +       buffers[i].data_is_valid = 0;
> +       grub_dprintf ("btrfs", "stripe %" PRIuGRUB_UINT64_T
> +                     " FAILED (dev ID %" PRIxGRUB_UINT64_T ")\n", i,
> +                     stripe->device_id);
> +       failed_devices++;
> +     }
> +    }
> +
> +  if (failed_devices > 1 && (chunk_type & GRUB_BTRFS_CHUNK_TYPE_RAID5))
> +    {
> +      grub_dprintf ("btrfs",
> +                 "not enough disks for RAID 5: total %" PRIuGRUB_UINT64_T
> +                 ", missing %" PRIuGRUB_UINT64_T "\n",
> +                 nstripes, failed_devices);
> +      ret = GRUB_ERR_READ_ERROR;
> +      goto cleanup;
> +    }
> +  else
> +    grub_dprintf ("btrfs",
> +               "enough disks for RAID 5 rebuilding: total %"
> +               PRIuGRUB_UINT64_T ", missing %" PRIuGRUB_UINT64_T "\n",
> +               nstripes, failed_devices);
> +
> +  /* if these are enough, try to rebuild the data */
> +  if (chunk_type & GRUB_BTRFS_CHUNK_TYPE_RAID5)
> +    rebuild_raid5 (buf, buffers, nstripes, csize);
> +  else
> +    grub_dprintf ("btrfs", "called rebuild_raid6(), NOT IMPLEMENTED\n");
> +
> +  ret = GRUB_ERR_NONE;
> + cleanup:
> +  if (buffers)
> +    for (i = 0; i < nstripes; i++)
> +     grub_free(buffers[i].buf);
> +  grub_free(buffers);
> +
> +  return ret;
> +}
> +
>  static grub_err_t
>  grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
>                        void *buf, grub_size_t size, int recursion_depth)
> @@ -742,6 +876,10 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, 
> grub_disk_addr_t addr,
>       grub_uint16_t nstripes;
>       unsigned redundancy = 1;
>       unsigned i, j;
> +     int is_raid56;
> +
> +     is_raid56 = !!(grub_le_to_cpu64 (chunk->type) &
> +                    GRUB_BTRFS_CHUNK_TYPE_RAID5);
>
>       if (grub_le_to_cpu64 (chunk->size) <= off)
>         {
> @@ -922,17 +1060,29 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, 
> grub_disk_addr_t addr,
>           grub_dprintf ("btrfs", "reading laddr 0x%" PRIxGRUB_UINT64_T "\n",
>                         addr);
>
> -         for (i = 0; i < redundancy; i++)
> +         if (!is_raid56)

Why not "if (is_raid56)"? This looks more natural here.

> +           for (i = 0; i < redundancy; i++)
> +             {
> +               err = btrfs_read_from_chunk (data, chunk, stripen,
> +                                            stripe_offset,
> +                                            i,     /* redundancy */
> +                                            csize, buf);
> +               if (!err)
> +                 break;
> +               grub_errno = GRUB_ERR_NONE;
> +             }
> +         else
>             {
>               err = btrfs_read_from_chunk (data, chunk, stripen,
>                                            stripe_offset,
> -                                          i,     /* redundancy */
> +                                          0,     /* no mirror */
>                                            csize, buf);
> -             if (!err)
> -               break;
>               grub_errno = GRUB_ERR_NONE;
> +             if (err != GRUB_ERR_NONE)

Please be consistent and use "if (err)" here.

> +               err = raid56_read_retry (data, chunk, stripe_offset,
> +                                        csize, buf);
>             }
> -         if (i != redundancy)
> +         if (err == GRUB_ERR_NONE)

if (!err) please...

Daniel