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

[Daniel Kiper]

On Wed, Sep 19, 2018 at 08:40:38PM +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 | 169 +++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 164 insertions(+), 5 deletions(-)
>
> diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
> index 5c1ebae77..55a7eeffc 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 +666,148 @@ 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;
> +
> +  i = 0;
> +  while (buffers[i].data_is_valid && i < nstripes)
> +    ++i;

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);

One line here please.

> +  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);
> +
> +    }

Hmmm... I think that this function can be simpler. You can drop first
while/for and "if (i == nstripes)". Then here:

if (first) {
  grub_dprintf ("btrfs", "called rebuild_raid5(), but all disks are OK\n");

Am I right?

> +}
> +
> +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_NONE;

s/GRUB_ERR_NONE/GRUB_ERR_OUT_OF_MEMORY/ and then you can drop at
least two relevant assigments and some curly brackets. Of course
before cleanup label you have to add ret = GRUB_ERR_NONE.

> +  grub_uint64_t i, failed_devices;
> +
> +  buffers = grub_zalloc (sizeof(*buffers) * nstripes);
> +  if (!buffers)
> +    {
> +      ret = GRUB_ERR_OUT_OF_MEMORY;
> +      goto cleanup;
> +    }
> +
> +  for (i = 0; i < nstripes; i++)
> +    {
> +      buffers[i].buf = grub_zalloc (csize);
> +      if (!buffers[i].buf)
> +     {
> +       ret = GRUB_ERR_OUT_OF_MEMORY;
> +       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 err2;

s/err2/err/?

> +
> +      stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
> +      stripe += i;

Why not stripe = ((struct grub_btrfs_chunk_stripe *) (chunk + 1)) + i;?

Daniel