On Wed, Sep 19, 2018 at 08:40:40PM +0200, Goffredo Baroncelli wrote: > From: Goffredo Baroncelli <kreij...@inwind.it> > > 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 md RAID 6 code already > present in grub. > > Signed-off-by: Goffredo Baroncelli <kreij...@inwind.it> > --- > grub-core/fs/btrfs.c | 54 +++++++++++++++++++++++++++++++++++++++----- > 1 file changed, 48 insertions(+), 6 deletions(-) > > diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c > index 55a7eeffc..400cd56b6 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+"); > > @@ -705,11 +706,36 @@ rebuild_raid5 (char *dest, struct raid56_buffer > *buffers, > } > } > > +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; > + > + if (!buffers[disk_nr].data_is_valid) > + return grub_errno = GRUB_ERR_READ_ERROR; > + > + grub_memcpy(dest, buffers[disk_nr].buf, size); > + > + return grub_errno = GRUB_ERR_NONE; > +} > + > +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, 0, raid6_recover_read_buffer); > +} > + > 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) > + grub_uint64_t stripe_offset, grub_uint64_t stripen, > + grub_uint64_t csize, void *buf, grub_uint64_t parities_pos) > { > struct raid56_buffer *buffers; > grub_uint64_t nstripes = grub_le_to_cpu16 (chunk->nstripes); > @@ -787,6 +813,15 @@ 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", > "enough disks for RAID 5 rebuilding: total %" > @@ -797,7 +832,7 @@ raid56_read_retry (struct grub_btrfs_data *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"); > + rebuild_raid6 (buffers, nstripes, csize, parities_pos, buf, stripen); > > cleanup: > if (buffers) > @@ -886,9 +921,11 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, > grub_disk_addr_t addr, > unsigned redundancy = 1; > unsigned i, j; > 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 | > + GRUB_BTRFS_CHUNK_TYPE_RAID6)); > > if (grub_le_to_cpu64 (chunk->size) <= off) > { > @@ -1015,6 +1052,8 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, > grub_disk_addr_t addr, > * - stripe_offset is the disk offset, > * - csize is the "potential" data to read. It will be reduced to > * size if the latter is smaller. > + * - parities_pos is the position of the parity inside a row (
s/inside/in/ > + * 2 for P1, 3 for P2...) > */ > block_nr = grub_divmod64 (off, chunk_stripe_length, &low); > > @@ -1030,6 +1069,9 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, > grub_disk_addr_t addr, > */ > grub_divmod64 (high + stripen, nstripes, &stripen); > > + grub_divmod64 (high + nstripes - nparities, nstripes, > + &parities_pos); I think that this math requires a bit of explanation in the comment before grub_divmod64(). Especially I am interested in why high + nstripes - nparities works as expected. Daniel