On 06/14/2018 01:17 PM, Daniel Kiper wrote: > On Sun, Jun 03, 2018 at 08:53:40PM +0200, Goffredo Baroncelli wrote: >> Signed-off-by: Goffredo Baroncelli <kreij...@inwind.it> >> --- >> grub-core/fs/btrfs.c | 70 ++++++++++++++++++++++++++++++++++++++++++++ >> 1 file changed, 70 insertions(+) >> >> diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c >> index be195448d..4d418859b 100644 >> --- a/grub-core/fs/btrfs.c >> +++ b/grub-core/fs/btrfs.c >> @@ -119,6 +119,8 @@ struct grub_btrfs_chunk_item >> #define GRUB_BTRFS_CHUNK_TYPE_RAID1 0x10 >> #define GRUB_BTRFS_CHUNK_TYPE_DUPLICATED 0x20 >> #define GRUB_BTRFS_CHUNK_TYPE_RAID10 0x40 >> +#define GRUB_BTRFS_CHUNK_TYPE_RAID5 0x80 >> +#define GRUB_BTRFS_CHUNK_TYPE_RAID6 0x100 >> grub_uint8_t dummy2[0xc]; >> grub_uint16_t nstripes; >> grub_uint16_t nsubstripes; >> @@ -764,6 +766,74 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, >> grub_disk_addr_t addr, >> stripe_offset = low + chunk_stripe_length >> * high; >> csize = chunk_stripe_length - low; >> + break; >> + } >> + case GRUB_BTRFS_CHUNK_TYPE_RAID5: >> + case GRUB_BTRFS_CHUNK_TYPE_RAID6: >> + { >> + grub_uint64_t nparities, stripe_nr, high, low; >> + >> + redundancy = 1; /* no redundancy for now */ >> + >> + if (grub_le_to_cpu64 (chunk->type) & GRUB_BTRFS_CHUNK_TYPE_RAID5) >> + { >> + grub_dprintf ("btrfs", "RAID5\n"); >> + nparities = 1; >> + } >> + else >> + { >> + grub_dprintf ("btrfs", "RAID6\n"); >> + nparities = 2; >> + } >> + >> + /* >> + * Below is an example of a RAID 6 layout and the meaning of the >> + * variables. The same applies to RAID 5. The only differences is >> + * that there is only one parity disk instead of two. >> + * >> + * A RAID 6 layout consists of several stripes spread >> + * on the disks, following a layout like the one below >> + * >> + * Disk1 Disk2 Disk3 Ddisk4 > > Numbering seems confusing to me. I think that it should be > Disk0 Disk1 Disk2 Disk3 > >> + * >> + * A1 B1 P1 Q1 >> + * Q2 A2 B2 P2 >> + * P3 Q3 A3 B3 >> + * [...] >> + * >> + * Note that the placement of the parities depends on row index. >> + * In the code below: >> + * - stripe_nr is the stripe number not considering the parities >> + * (A1=0, B1=1, A2 = 2, B2 = 3, ...), > > Please be consistent. A1 = 0, B1 = 1, A2 = 2, B2 = 3, ... > >> + * - high is the row number (0 for A1...Q1, 1 for Q2..P2, ...), > > Ditto. Please always use "..." not "..". > >> + * - stripen is the column number (or disk number), > > AIUI starting from 0. Right? If yes then I think that > drawing above requires disks/columns renumbering. right > >> + * - off is the logical address to read (from the beginning of >> + * the chunk space), > > s/chunk space/chunk/? > >> + * - chunk_stripe_length is the size of a stripe (typically 64k), >> + * - nstripes is the number of disks, >> + * - low is the offset of the data inside a stripe, >> + * - stripe_offset is the offset from the beginning of the chunk >> + * disks physical address, > > I am not sure that I understand. Could clarify this? - stripe_offset is the offset (in bytes) from the beginning of the chunk portion stored on disk.
You can think "stripe_offset" as the "row" in the drawing, but measured in bytes. > >> + * - csize is the "potential" data to read. It will be reduced to >> + * size if the latter is smaller. >> + */ >> + stripe_nr = grub_divmod64 (off, chunk_stripe_length, &low); > > OK. > >> + /* >> + * stripen is evaluated without considering >> + * the parities (0 for A1, A2, A3... 1 for B1, B2...). >> + */ >> + high = grub_divmod64 (stripe_nr, nstripes - nparities, &stripen); > > OK. > >> + /* >> + * stripen now considers also the parities (0 for A1, 1 for A2, >> + * 2 for A3....). The math is performed modulo number of disks. >> + */ >> + grub_divmod64 (high + stripen, nstripes, &stripen); > > OK. > >> + stripe_offset = low + chunk_stripe_length * high; > > Hmmm... I am confused. What does it mean? > > Daniel > > _______________________________________________ > Grub-devel mailing list > Grub-devel@gnu.org > https://lists.gnu.org/mailman/listinfo/grub-devel > -- gpg @keyserver.linux.it: Goffredo Baroncelli <kreijackATinwind.it> Key fingerprint BBF5 1610 0B64 DAC6 5F7D 17B2 0EDA 9B37 8B82 E0B5 _______________________________________________ Grub-devel mailing list Grub-devel@gnu.org https://lists.gnu.org/mailman/listinfo/grub-devel