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
+ *
+ * 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, ...),
+ * - high is the row number (0 for A1...Q1, 1 for Q2..P2, ...),
+ * - stripen is the column number (or disk number),
+ * - off is the logical address to read (from the beginning of
+ * the chunk space),
+ * - 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,
+ * - 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);
+
+ /*
+ * stripen is evaluated without considering
+ * the parities (0 for A1, A2, A3... 1 for B1, B2...).
+ */
+ high = grub_divmod64 (stripe_nr, nstripes - nparities, &stripen);
+
+ /*
+ * 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);
+
+ stripe_offset = low + chunk_stripe_length * high;
+ csize = chunk_stripe_length - low;
+
break;
}
default:
--
2.17.1
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