@@ -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 +766,77 @@ 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;
+ }
+
+ /*
+ * RAID 6 layout consists of several stripes spread over
+ * the disks, e.g.:
+ *
+ * Disk_0 Disk_1 Disk_2 Disk_3
+ * A0 B0 P0 Q0
+ * Q1 A1 B1 P1
+ * P2 Q2 A2 B2
+ *
+ * Note: placement of the parities depend on row number.
+ *
+ * Pay attention that the btrfs terminology may differ from
+ * terminology used in other RAID implementations, e.g. LVM,
+ * dm or md. The main difference is that btrfs calls contiguous
+ * block of data on a given disk, e.g. A0, stripe instead of chunk.
+ *
+ * The variables listed below have following meaning:
+ * - stripe_nr is the stripe number excluding the parities
+ * (A0 = 0, B0 = 1, A1 = 2, B1 = 3, etc.),
+ * - high is the row number (0 for A0...Q0, 1 for Q1...P1, etc.),
+ * - stripen is the disk number in a row (0 for A0, Q1, P2,
+ * 1 for B0, A1, Q2, etc.),
+ * - off is the logical address to read,
+ * - chunk_stripe_length is the size of a stripe (typically 64 KiB),
+ * - nstripes is the number of disks in a row,
+ * - low is the offset of the data inside a stripe,
+ * - stripe_offset is the data offset in an array,
+ * - csize is the "potential" data to read; it will be reduced
+ * to size if the latter is smaller,
+ * - nparities is the number of parities (1 for RAID 5, 2 for
+ * RAID 6); used only in RAID 5/6 code.
+ */
+ stripe_nr = grub_divmod64 (off, chunk_stripe_length, &low);
+
+ /*
+ * stripen is computed without the parities
+ * (0 for A0, A1, A2, 1 for B0, B1, B2, etc.).
+ */
+ high = grub_divmod64 (stripe_nr, nstripes - nparities, &stripen);
+
+ /*
+ * The stripes are spread over the disks. Every each row their
+ * positions are shifted by 1 place. So, the real disks number
+ * change. Hence, we have to take into account current row number
+ * modulo nstripes (0 for A0, 1 for A1, 2 for A2, etc.).
+ */
+ grub_divmod64 (high + stripen, nstripes, &stripen);
+
+ stripe_offset = low + chunk_stripe_length * high;
+ csize = chunk_stripe_length - low;
+
break;
}
default: