From: Goffredo Baroncelli <kreij...@inwind.it>
Signed-off-by: Goffredo Baroncelli <kreij...@inwind.it>
---
grub-core/fs/btrfs.c | 66 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 66 insertions(+)
diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
index be195448d..56c42746d 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 +766,70 @@ 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, block_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 blocks spread on the disks.
+ * The raid terminology is used to call all the blocks of a row
+ * "stripe". Unfortunately the BTRFS terminology confuses block
+ * and stripe.
+ *
+ * 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:
+ * - block_nr is the block 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 (0 for A1,Q2,P3, 1 for B1...),
+ * - off is the logical address to read
+ * - chunk_stripe_length is the size of a block (typically 64k),
+ * - nstripes is the number of disks,
+ * - low is the offset of the data inside a stripe,
+ * - stripe_offset is the disk offset,
+ * - csize is the "potential" data to read. It will be reduced to
+ * size if the latter is smaller.
+ */
+ block_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 (block_nr, nstripes - nparities, &stripen);
+
+ /*
+ * stripen is recomputed considering the parities (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
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