[PATCH 6/7] Add support for recovery for a raid5 btrfs profiles.

[Goffredo Baroncelli]

Signed-off-by: Goffredo Baroncelli <address@hidden>
---
 grub-core/fs/btrfs.c | 206 +++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 199 insertions(+), 7 deletions(-)

diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
index 697322125..5c76a68f3 100644
--- a/grub-core/fs/btrfs.c
+++ b/grub-core/fs/btrfs.c
@@ -29,6 +29,7 @@
 #include <minilzo.h>
 #include <grub/i18n.h>
 #include <grub/btrfs.h>
+#include <grub/crypto.h>
 
 GRUB_MOD_LICENSE ("GPLv3+");
 
@@ -661,9 +662,180 @@ btrfs_read_from_chunk (struct grub_btrfs_data *data,
     err = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
                          paddr & (GRUB_DISK_SECTOR_SIZE - 1),
                          csize, buf);
+    grub_dprintf ("btrfs", "reading paddr 0x%" PRIxGRUB_UINT64_T "\n", paddr);
     return err;
 }
 
+struct raid56_buffer {
+  void *buf;
+  int  ok;
+};
+
+static void
+rebuild_raid5 (struct raid56_buffer *buffers, grub_uint64_t nstripes,
+               grub_uint64_t csize)
+{
+  grub_uint64_t target, i;
+
+  target = 0;
+  while (buffers[target].ok && target < nstripes)
+    ++target;
+
+  if (target == nstripes)
+    {
+      grub_dprintf ("btrfs", "called rebuild_raid5(), but all disks are OK\n");
+      return;
+    }
+
+  grub_dprintf ("btrfs", "rebuilding raid5 stripe #%" PRIuGRUB_UINT64_T "\n",
+               target);
+  for (i = 0; i < nstripes ; i++)
+    if (i != target)
+      grub_crypto_xor (buffers[target].buf, buffers[target].buf, 
buffers[i].buf,
+                       csize);
+}
+
+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)
+
+{
+  (void)buffers;
+  (void)nstripes;
+  (void)csize;
+  (void)parities_pos;
+  (void)dest;
+  (void)stripen;
+  grub_dprintf ("btrfs", "called rebuild_raid6(), NOT IMPLEMENTED\n");
+}
+
+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 parities_pos)
+{
+
+  struct raid56_buffer *buffers = NULL;
+  grub_uint64_t nstripes = grub_le_to_cpu16 (chunk->nstripes);
+  grub_uint64_t chunk_type = grub_le_to_cpu64 (chunk->type);
+  grub_err_t ret = GRUB_ERR_NONE;
+  grub_uint64_t i, failed_devices;
+
+  buffers = grub_zalloc (sizeof(struct raid56_buffer)* nstripes);
+  if (!buffers)
+    {
+      ret = GRUB_ERR_OUT_OF_MEMORY;
+      goto cleanup;
+    }
+
+  for (i = 0 ; i < nstripes ; i++)
+    {
+      buffers[i].buf = grub_zalloc(csize);
+      if (!buffers[i].buf)
+       {
+         ret = GRUB_ERR_OUT_OF_MEMORY;
+         goto cleanup;
+       }
+    }
+
+  for (i = 0 ; i < nstripes ; i++)
+    {
+      struct grub_btrfs_chunk_stripe *stripe;
+      grub_disk_addr_t paddr;
+      grub_device_t dev;
+      grub_err_t err2;
+
+      stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
+      stripe += i;
+
+      paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
+      grub_dprintf ("btrfs", "reading paddr %" PRIxGRUB_UINT64_T
+                    " from stripe ID %" PRIxGRUB_UINT64_T "\n", paddr,
+                    stripe->device_id);
+
+      /* FIXME: rescan the devices */
+      dev = find_device (data, stripe->device_id);
+      if (!dev)
+       {
+         buffers[i].ok = 0;
+         grub_dprintf ("btrfs", "stripe %" PRIuGRUB_UINT64_T " FAILED (dev ID 
%"
+                       PRIxGRUB_UINT64_T ")\n", i, stripe->device_id);
+         continue;
+        }
+
+      err2 = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
+                            paddr & (GRUB_DISK_SECTOR_SIZE - 1),
+                            csize, buffers[i].buf);
+      if (err2 == GRUB_ERR_NONE)
+       {
+         buffers[i].ok = 1;
+         grub_dprintf ("btrfs", "stripe %" PRIuGRUB_UINT64_T " Ok (dev ID %"
+                       PRIxGRUB_UINT64_T ")\n", i, stripe->device_id);
+       }
+      else
+       {
+         buffers[i].ok = 0;
+         grub_dprintf ("btrfs", "stripe %" PRIuGRUB_UINT64_T
+                       " FAILED (dev ID %" PRIxGRUB_UINT64_T ")\n", i,
+                       stripe->device_id);
+       }
+    }
+
+  failed_devices = 0;
+  for (i = 0 ; i < nstripes ; i++)
+    if (!buffers[i].ok)
+      ++failed_devices;
+  if (failed_devices > 1 && (chunk_type & GRUB_BTRFS_CHUNK_TYPE_RAID5))
+    {
+      grub_dprintf ("btrfs",
+                   "not enough disks for raid5: total %" PRIuGRUB_UINT64_T
+                   ", missing %" PRIuGRUB_UINT64_T "\n",
+                   nstripes, failed_devices);
+      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",
+                    "enough disks for raid5/6 rebuilding: total %"
+                   PRIuGRUB_UINT64_T ", missing %" PRIuGRUB_UINT64_T "\n",
+                    nstripes, failed_devices);
+    }
+
+  /* if these are enough, try to rebuild the data */
+  if (chunk_type & GRUB_BTRFS_CHUNK_TYPE_RAID5)
+    {
+      rebuild_raid5 (buffers, nstripes, csize);
+      grub_memcpy (buf, buffers[stripen].buf, csize);
+    }
+  else
+    {
+      rebuild_raid6 (buffers, nstripes, csize, parities_pos, buf, stripen);
+    }
+
+cleanup:
+  if (buffers)
+    {
+      for (i = 0 ; i < nstripes ; i++)
+       if (buffers[i].buf)
+         grub_free(buffers[i].buf);
+      grub_free(buffers);
+    }
+
+  return ret;
+}
+
 static grub_err_t
 grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
                         void *buf, grub_size_t size, int recursion_depth)
@@ -741,6 +913,11 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, 
grub_disk_addr_t addr,
        grub_uint16_t nstripes;
        unsigned redundancy = 1;
        unsigned i, j;
+        int is_raid56;
+       grub_uint64_t parities_pos = 0;
+
+        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)
          {
@@ -844,9 +1021,10 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, 
grub_disk_addr_t addr,
                }
 
              stripe_nr = grub_divmod64 (off, chunk_stripe_length, &low);
-
              high = grub_divmod64 (stripe_nr, nstripes - nparities, &stripen);
              grub_divmod64 (high + stripen, nstripes, &stripen);
+             grub_divmod64 (high + nstripes - nparities, nstripes,
+                            &parities_pos);
 
              stripe_offset = low + chunk_stripe_length * high;
              csize = chunk_stripe_length - low;
@@ -881,12 +1059,26 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, 
grub_disk_addr_t addr,
            grub_dprintf ("btrfs", "reading laddr 0x%" PRIxGRUB_UINT64_T "\n",
                          addr);
 
-           err = GRUB_ERR_NONE + 1;
-           for (i = 0; i < redundancy && err != GRUB_ERR_NONE; i++)
-                err = btrfs_read_from_chunk (data, chunk, stripen,
-                                             stripe_offset,
-                                             i,     /* redundancy */
-                                             csize, buf);
+           if (!is_raid56)
+             {
+               err = GRUB_ERR_NONE+1;
+               for (i = 0; i < redundancy && err != GRUB_ERR_NONE; i++)
+                   err = btrfs_read_from_chunk (data, chunk, stripen,
+                                                stripe_offset,
+                                                i,     /* use mirror #nr */
+                                                csize, buf);
+             }
+           else
+             {
+               err = btrfs_read_from_chunk (data, chunk, stripen,
+                                            stripe_offset,
+                                            0,     /* no mirror */
+                                            csize, buf);
+               if (err != GRUB_ERR_NONE)
+                 err = raid56_read_retry (data, chunk, stripe_offset,
+                                          stripen, csize, buf, parities_pos);
+             }
+
          }
        if (err)
          return grub_errno = err;
-- 
2.17.0