[RFC] Add support for BTRFS raid5/6 to GRUB

[Goffredo Baroncelli]

Hi All,

Below you can find a patch to add support for accessing files from grub in a 
RAID5/6 btrfs filesystem. This is a RFC because it is missing the support for 
recovery (i.e. if some devices are missed). In the next days (weeks ?) I will 
extend this patch to support also this case.

Comments are welcome.

BR
G.Baroncelli


---

commit 8c80a1b7c913faf50f95c5c76b4666ed17685666
Author: Goffredo Baroncelli <address@hidden>
Date:   Tue Apr 17 21:40:31 2018 +0200

    Add initial support for btrfs raid5/6 chunk

diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
index be195448d..4c5632acb 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 +766,39 @@ 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;
+             grub_uint64_t parity_pos;
+             grub_uint64_t stripe_nr, high;
+             grub_uint64_t 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;
+               }
+
+             stripe_nr = grub_divmod64 (off, chunk_stripe_length, &low);
+
+             high = grub_divmod64 (stripe_nr, nstripes - nparities, &stripen);
+             grub_divmod64 (high+nstripes-nparities, nstripes, &parity_pos);
+             grub_divmod64 (parity_pos+nparities+stripen, nstripes, &stripen);
+
+             stripe_offset = low + chunk_stripe_length * high;
+             csize = chunk_stripe_length - low;
+
              break;
            }
          default:


-- 
gpg @keyserver.linux.it: Goffredo Baroncelli <kreijackATinwind.it>
Key fingerprint BBF5 1610 0B64 DAC6 5F7D  17B2 0EDA 9B37 8B82 E0B5