[PATCH 7/9] btrfs: add support for recovery for a RAID 5 btrfs profiles.

[Goffredo Baroncelli]

Signed-off-by: Goffredo Baroncelli <address@hidden>
---
 grub-core/fs/btrfs.c | 174 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 170 insertions(+), 4 deletions(-)

diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
index 63651928b..5fcaad86f 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+");
 
@@ -666,6 +667,150 @@ btrfs_read_from_chunk (struct grub_btrfs_data *data,
     return err;
 }
 
+struct raid56_buffer {
+  void *buf;
+  int  data_is_valid;
+};
+
+static void
+rebuild_raid5 (struct raid56_buffer *buffers, grub_uint64_t nstripes,
+               grub_uint64_t csize)
+{
+  grub_uint64_t target = 0, i;
+
+  while (buffers[target].data_is_valid && 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 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)
+{
+
+  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(*buffers) * 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);
+
+      dev = find_device (data, stripe->device_id);
+      if (!dev)
+       {
+         buffers[i].data_is_valid = 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].data_is_valid = 1;
+         grub_dprintf ("btrfs", "stripe %" PRIuGRUB_UINT64_T " Ok (dev ID %"
+                       PRIxGRUB_UINT64_T ")\n", i, stripe->device_id);
+       }
+      else
+       {
+         buffers[i].data_is_valid = 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].data_is_valid)
+      ++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
+    {
+      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
+    {
+      grub_dprintf ("btrfs", "called rebuild_raid6(), NOT IMPLEMENTED\n");
+    }
+
+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)
@@ -743,6 +888,11 @@ 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);
 
        if (grub_le_to_cpu64 (chunk->size) <= off)
          {
@@ -885,6 +1035,8 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, 
grub_disk_addr_t addr,
               * number of disks
               */
              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;
@@ -917,15 +1069,29 @@ 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);
 
-           for (i = 0; i < redundancy; i++)
+           if (!is_raid56)
+             {
+               for (i = 0; i < redundancy; i++)
+                 {
+                   err = btrfs_read_from_chunk (data, chunk, stripen,
+                                                stripe_offset,
+                                                i,     /* redundancy */
+                                                csize, buf);
+                   if (err == GRUB_ERR_NONE)
+                       break;
+                 }
+             }
+           else
              {
                err = btrfs_read_from_chunk (data, chunk, stripen,
                                             stripe_offset,
-                                            i,     /* redundancy */
+                                            0,     /* no mirror */
                                             csize, buf);
-               if (err == GRUB_ERR_NONE)
-                   break;
+               if (err != GRUB_ERR_NONE)
+                 err = raid56_read_retry (data, chunk, stripe_offset,
+                                          stripen, csize, buf);
              }
+
            if (err == GRUB_ERR_NONE)
                break;
          }
-- 
2.17.0