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

[Goffredo Baroncelli]

On 06/14/2018 03:03 PM, Daniel Kiper wrote:
> On Sun, Jun 03, 2018 at 08:53:46PM +0200, Goffredo Baroncelli wrote:
>> Add support for recovery fo a RAID 5 btrfs profile. In addition
> 
> s/fo /for /
> 
>> 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 | 180 +++++++++++++++++++++++++++++++++++++++++--
>>  1 file changed, 175 insertions(+), 5 deletions(-)
>>
>> diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
>> index 9cdbfe792..c8f034641 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+");
>>
>> @@ -666,6 +667,157 @@ 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;
> 
> grub_uint64_t i = 0;
> int first = 1;
> 
>> +  int first;
>> +
>> +  i = 0;
> 
> Then you can drop this assignment.

I prefer to tie the assignment to the place where it is used.

> 
>> +  while (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);
> 
> This can be in one line.
> 
>> +  first = 1;
> 
> And you can drop this assignment too.
> 
>> +  for (i = 0; i < nstripes; i++)
>> +    {
>> +      if (!buffers[i].data_is_valid)
>> +    continue;
>> +
>> +      if (first)
>> +    grub_memcpy(dest, buffers[i].buf, csize);
>> +      else
>> +    grub_crypto_xor (dest, dest, buffers[i].buf, csize);
> 
> I am not sure why at first you use grub_memcpy() and
> then move to grub_crypto_xor(). Could you explain this?
> Why do not use grub_crypto_xor() in all cases?

This avoid to require that dest has to be initialized to zero.

> 
>> +
>> +      first = 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 csize, void *buf)
>> +{
>> +
> 
> Please drop this empty line. I have asked about that earlier.
> 
>> +  struct raid56_buffer *buffers = NULL;
>> +  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;
>> +  grub_uint64_t i, failed_devices;
>> +
>> +  buffers = grub_zalloc (sizeof(*buffers) * nstripes);
> 
> How often this function is called? Maybe you should consider
> doing memory allocation for this function only once and free
> it at btrfs module unload.

This is only needed in case of recovery. Which should happen no too often. 
Usually, this function is never called.
> 
>> +  if (!buffers)
>> +    {
>> +      ret = GRUB_ERR_OUT_OF_MEMORY;
>> +      goto cleanup;
>> +    }
>> +
>> +  for (i = 0; i < nstripes; i++)
>> +    {
>> +      buffers[i].buf = grub_zalloc (csize);
> 
> Ditto.
> 
>> +      if (!buffers[i].buf)
>> +    {
>> +      ret = GRUB_ERR_OUT_OF_MEMORY;
>> +      goto cleanup;
>> +    }
>> +    }
>> +
>> +  for (i = 0; i < nstripes; i++)
>> +    {
>> +      struct grub_btrfs_chunk_stripe *stripe;
>> +      grub_disk_addr_t paddr;
>> +      grub_device_t dev;
>> +      grub_err_t err2;
>> +
>> +      stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
>> +      stripe += i;
>> +
>> +      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);
>> +      continue;
>> +    }
>> +
>> +      err2 = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
>> +                         paddr & (GRUB_DISK_SECTOR_SIZE - 1),
>> +                         csize, buffers[i].buf);
>> +      if (err2 == 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 = 0;
>> +  for (i = 0; i < nstripes; i++)
> 
> for (failed_devices = i = 0; i < nstripes; i++)

Nice
> 
>> +    if (!buffers[i].data_is_valid)
>> +      ++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");
>> +
>> +cleanup:
> 
> Space before the label please.
> I have asked about earlier.

The line before the label is already a space; Am I missing something ?

> 
>> +
> 
> Please drop this empty line.
> 
> Daniel
> 


-- 
gpg @keyserver.linux.it: Goffredo Baroncelli <kreijackATinwind.it>
Key fingerprint BBF5 1610 0B64 DAC6 5F7D  17B2 0EDA 9B37 8B82 E0B5