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

[Goffredo Baroncelli]

On 05/30/2018 02:15 PM, Daniel Kiper wrote:
> 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/

ok

>> 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?

I would like; however this would mean that the handling of the raid 5 and raid 
6 rebuilding code would be totally different. This has a big impact on the 
patches set and the related tests performed until now.
Are you sure that this effort will be really needed ?
> 
>> +    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?
OK
> 
>> +                    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.
You are right
> 
> Daniel
> 

I think that I implemented all your requests in the next patches set. The only 
exception is the removing the memcpy in the raid6 recovery path.
Now I am starting the test. when I will completed the test phase, I will resend 
the patches.

BR
G.Baroncelli
-- 
gpg @keyserver.linux.it: Goffredo Baroncelli <kreijackATinwind.it>
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