From: Goffredo Baroncelli <kreijack@xxxxxxxxx>
Signed-off-by: Goffredo Baroncelli <kreijack@xxxxxxxxx>
---
grub-core/fs/btrfs.c | 74 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 74 insertions(+)
diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
index be195448d..9bc6d399d 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 +766,78 @@ 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;
+ }
+
+ /*
+ * A RAID 6 layout consists of several stripes spread on the
+ * disks, following a layout like the one below
+ *
+ * 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.
+ * Pay attention that the BTRFS terminolgy may be different
+ * from others RAID implementation (e.g. lvm/dm or md). In BTRFS
+ * a contiguous block of data of a disk (like A1) is called
+ * stripe.
+ * In the code below:
+ * - stripe_nr is the stripe number without the parities
+ * (A1 = 0, B1 = 1, A2 = 2, B2 = 3, ...),
+ * - high is the row number (0 for A1...Q1, 1 for Q2...P2, ...),
+ * - stripen is the disk number in a row (0 for A1,Q2,P3, 1 for
+ * B1...),
+ * - off is the logical address to read,
+ * - chunk_stripe_length is the size of a stripe (typically 64k),
+ * - nstripes is the number of disks of 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 RAID5, 2 for
+ * RAID6); used only in RAID5/6 code.
+ */
+ stripe_nr = grub_divmod64 (off, chunk_stripe_length, &low);
+
+ /*
+ * stripen is computed without the parities (0 for A1, A2, A3...
+ * 1 for B1, B2...).
+ */
+ high = grub_divmod64 (stripe_nr, nstripes - nparities, &stripen);
+
+ /*
+ * the stripes are spread across the disks, each row their
+ * position is shifted by 1 place. So to compute the real disk
+ * number occuped by a stripe, we need to sum also the
+ * "row number" in modulo nstripes (0 for A1, 1 for A2, 2 for
+ * A3....).
+ */
+ grub_divmod64 (high + stripen, nstripes, &stripen);
+
+ stripe_offset = low + chunk_stripe_length * high;
+ csize = chunk_stripe_length - low;
+
break;
}
default:
--
2.19.0
