[PATCH 9/9] btrfs: add RAID 6 recovery for a btrfs filesystem.

[Goffredo Baroncelli]

Add the RAID 6 recovery, in order to use a RAID 6 filesystem even if some
disks (up to two) are missing. This code use the old md RAID 6 code already
present in grub.

Signed-off-by: Goffredo Baroncelli <address@hidden>
---
 grub-core/fs/btrfs.c | 45 +++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 40 insertions(+), 5 deletions(-)

diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
index 5fcaad86f..3d71b954e 100644
--- a/grub-core/fs/btrfs.c
+++ b/grub-core/fs/btrfs.c
@@ -30,6 +30,7 @@
 #include <grub/i18n.h>
 #include <grub/btrfs.h>
 #include <grub/crypto.h>
+#include <grub/diskfilter.h>
 
 GRUB_MOD_LICENSE ("GPLv3+");
 
@@ -695,11 +696,35 @@ rebuild_raid5 (struct raid56_buffer *buffers, 
grub_uint64_t nstripes,
                        csize);
 }
 
+static grub_err_t
+raid6_recover_read_buffer (void *data, int disk_nr,
+                          grub_uint64_t addr __attribute__ ((unused)),
+                          void *dest, grub_size_t size)
+{
+    struct raid56_buffer *buffers = data;
+
+    grub_memcpy(dest, buffers[disk_nr].buf, size);
+
+    grub_errno = buffers[disk_nr].data_is_valid ? GRUB_ERR_NONE : 
+                GRUB_ERR_READ_ERROR;
+    return grub_errno;
+}
+
+static void
+rebuild_raid6 (struct raid56_buffer *buffers, grub_uint64_t nstripes,
+               grub_uint64_t csize, grub_uint64_t parities_pos, void *dest,
+               grub_uint64_t stripen)
+
+{
+  grub_raid6_recover_gen (buffers, nstripes, stripen, parities_pos,
+                          dest, 0, csize, raid6_recover_read_buffer, 0);
+}
+
 static grub_err_t
 raid56_read_retry (struct grub_btrfs_data *data,
                   struct grub_btrfs_chunk_item *chunk,
                   grub_uint64_t stripe_offset, grub_uint64_t stripen,
-                  grub_uint64_t csize, void *buf)
+                  grub_uint64_t csize, void *buf, grub_uint64_t parities_pos)
 {
 
   struct raid56_buffer *buffers = NULL;
@@ -780,6 +805,15 @@ raid56_read_retry (struct grub_btrfs_data *data,
       ret = GRUB_ERR_READ_ERROR;
       goto cleanup;
     }
+  else if (failed_devices > 2 && (chunk_type & GRUB_BTRFS_CHUNK_TYPE_RAID6))
+    {
+      grub_dprintf ("btrfs",
+                   "not enough disks for raid6: total %" PRIuGRUB_UINT64_T
+                   ", missing %" PRIuGRUB_UINT64_T "\n",
+                   nstripes, failed_devices);
+      ret = GRUB_ERR_READ_ERROR;
+      goto cleanup;
+    }
   else
     {
       grub_dprintf ("btrfs",
@@ -796,7 +830,7 @@ raid56_read_retry (struct grub_btrfs_data *data,
     }
   else
     {
-      grub_dprintf ("btrfs", "called rebuild_raid6(), NOT IMPLEMENTED\n");
+      rebuild_raid6 (buffers, nstripes, csize, parities_pos, buf, stripen);
     }
 
 cleanup:
@@ -891,8 +925,9 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, 
grub_disk_addr_t addr,
        int is_raid56;
        grub_uint64_t parities_pos = 0;
 
-       is_raid56 = !!(grub_le_to_cpu64 (chunk->type) &
-                      GRUB_BTRFS_CHUNK_TYPE_RAID5);
+        is_raid56 = !!(grub_le_to_cpu64 (chunk->type) &
+                      (GRUB_BTRFS_CHUNK_TYPE_RAID5|
+                       GRUB_BTRFS_CHUNK_TYPE_RAID6));
 
        if (grub_le_to_cpu64 (chunk->size) <= off)
          {
@@ -1089,7 +1124,7 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, 
grub_disk_addr_t addr,
                                             csize, buf);
                if (err != GRUB_ERR_NONE)
                  err = raid56_read_retry (data, chunk, stripe_offset,
-                                          stripen, csize, buf);
+                                          stripen, csize, buf, parities_pos);
              }
 
            if (err == GRUB_ERR_NONE)
-- 
2.17.0