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

[Goffredo Baroncelli <kreijack@libero.it>]

On 25/09/2018 21.10, Daniel Kiper wrote:
> On Wed, Sep 19, 2018 at 08:40:38PM +0200, Goffredo Baroncelli wrote:
>> From: Goffredo Baroncelli <kreijack@inwind.it>
>>
>> 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 <kreijack@inwind.it>
>> ---
>>  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?

Ehm.. no. The "if" is an internal check to avoid BUG. rebuild_raid5() should be called only if some disk is missed.
To perform this control, the code checks if all buffers are valid. Otherwise there is an internal BUG.

Checking "first" is a completely different test.

>> +}
>> +
>> +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/?

Ok

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

Make sense
> 
> Daniel
> 


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