use anopther RAID1(0) copy if main one fails

diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
index 7e31fa3f15cd5a4483ed94ffbb42f0b4c8861392..b7edb7e3970a16581f42e476c5d02f2ff5072b33 100644 (file)
--- a/grub-core/fs/btrfs.c
+++ b/grub-core/fs/btrfs.c
@@ -491,7 +491,8 @@ lower_bound (struct grub_btrfs_data *data,
 }
 
 static grub_device_t
-find_device (struct grub_btrfs_data *data, grub_uint64_t id)
+find_device (struct grub_btrfs_data *data, grub_uint64_t id,
+            int do_rescan)
 {
   grub_device_t dev_found = NULL;
   auto int hook (const char *name);
@@ -537,7 +538,8 @@ find_device (struct grub_btrfs_data *data, grub_uint64_t id)
   for (i = 0; i < data->n_devices_attached; i++)
     if (id == data->devices_attached[i].id)
       return data->devices_attached[i].dev;
-  grub_device_iterate (hook);
+  if (do_rescan)
+    grub_device_iterate (hook);
   if (!dev_found)
     {
       grub_error (GRUB_ERR_BAD_FS, "couldn't find a member device");
@@ -574,7 +576,6 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data,
       grub_uint8_t *ptr;
       struct grub_btrfs_key *key;
       struct grub_btrfs_chunk_item *chunk;  
-      struct grub_btrfs_chunk_stripe *stripe;
       grub_ssize_t csize;
       grub_err_t err; 
       struct grub_btrfs_key key_out;
@@ -598,7 +599,8 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data,
              + grub_le_to_cpu64 (chunk->size))
            goto chunk_found;
          ptr += sizeof (*key) + sizeof (*chunk)
-           + sizeof (*stripe) * grub_le_to_cpu16 (chunk->nstripes);
+           + sizeof (struct grub_btrfs_chunk_stripe)
+           * grub_le_to_cpu16 (chunk->nstripes);
        }
       struct grub_btrfs_key key_in;
       grub_size_t chsize;
@@ -634,9 +636,9 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data,
        grub_uint32_t stripen;
        grub_uint32_t stripe_offset;
        grub_uint64_t off = addr - grub_le_to_cpu64 (key->offset);
-       grub_disk_addr_t paddr;
+       unsigned redundancy = 1;
+       unsigned i, j;
 
-       stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
        switch (grub_le_to_cpu64 (chunk->type)
                & ~GRUB_BTRFS_CHUNK_TYPE_BITS_DONTCARE)
          {
@@ -661,6 +663,7 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data,
              stripen = 0;
              stripe_offset = off;
              csize = stripe_length - off;
+             redundancy = 2;
              break;
            }
          case GRUB_BTRFS_CHUNK_TYPE_RAID0:
@@ -692,6 +695,8 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data,
                                    &stripen);
              stripen *= grub_le_to_cpu16 (chunk->nstripes)
                / grub_le_to_cpu16 (chunk->nsubstripes);
+             redundancy = grub_le_to_cpu16 (chunk->nstripes)
+               / grub_le_to_cpu16 (chunk->nsubstripes);
              stripe_offset = low + grub_le_to_cpu64 (chunk->stripe_length)
                * high;
              csize = grub_le_to_cpu64 (chunk->stripe_length) - low;
@@ -702,35 +707,60 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data,
                               "unsupported RAID flags %" PRIxGRUB_UINT64_T,
                               grub_le_to_cpu64 (chunk->type));
          }
-       stripe += stripen;
        if (csize <= 0)
          return grub_error (GRUB_ERR_BAD_FS,
                             "couldn't find the chunk descriptor");
        if ((grub_size_t) csize > size)
          csize = size;
-       dev = find_device (data, stripe->device_id);
-       if (!dev)
-         return grub_errno;
-       grub_dprintf ("btrfs", "chunk 0x%" PRIxGRUB_UINT64_T
-                     "+0x%" PRIxGRUB_UINT64_T " (%d stripes (%d substripes) of %"
-                     PRIxGRUB_UINT64_T ") stripe %" PRIxGRUB_UINT32_T
-                     " maps to 0x%" PRIxGRUB_UINT64_T "\n",
-                     grub_le_to_cpu64 (key->offset),
-                     grub_le_to_cpu64 (chunk->size),
-                     grub_le_to_cpu16 (chunk->nstripes),
-                     grub_le_to_cpu16 (chunk->nsubstripes),
-                     grub_le_to_cpu64 (chunk->stripe_length),
-                     stripen,
-                     stripe->offset);
-       paddr = stripe->offset + stripe_offset;
-
-       grub_dprintf ("btrfs", "reading paddr 0x%" PRIxGRUB_UINT64_T
-                     " for laddr 0x%" PRIxGRUB_UINT64_T"\n", paddr,
-                     addr);      
-       err = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS, 
-                             paddr & (GRUB_DISK_SECTOR_SIZE - 1), csize, buf);
+
+       for (j = 0; j < 2; j++)
+         {
+           for (i = 0; i < redundancy; i++)
+             {
+               struct grub_btrfs_chunk_stripe *stripe;
+               grub_disk_addr_t paddr;
+
+               stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
+               /* Right now the redundancy handlind is easy.
+                  With RAID5-like it will be more difficult.  */
+               stripe += stripen + i;
+
+               paddr = stripe->offset + stripe_offset;
+
+               grub_dprintf ("btrfs", "chunk 0x%" PRIxGRUB_UINT64_T
+                             "+0x%" PRIxGRUB_UINT64_T " (%d stripes (%d substripes) of %"
+                             PRIxGRUB_UINT64_T ") stripe %" PRIxGRUB_UINT32_T
+                             " maps to 0x%" PRIxGRUB_UINT64_T "\n",
+                             grub_le_to_cpu64 (key->offset),
+                             grub_le_to_cpu64 (chunk->size),
+                             grub_le_to_cpu16 (chunk->nstripes),
+                             grub_le_to_cpu16 (chunk->nsubstripes),
+                             grub_le_to_cpu64 (chunk->stripe_length),
+                             stripen, stripe->offset);
+               grub_dprintf ("btrfs", "reading paddr 0x%" PRIxGRUB_UINT64_T
+                             " for laddr 0x%" PRIxGRUB_UINT64_T"\n", paddr,
+                             addr);
+
+               dev = find_device (data, stripe->device_id, j);
+               if (!dev)
+                 {
+                   err = grub_errno;
+                   grub_errno = GRUB_ERR_NONE;
+                   continue;
+                 }
+
+               err = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
+                                     paddr & (GRUB_DISK_SECTOR_SIZE - 1),
+                                     csize, buf);
+               if (!err)
+                 break;
+               grub_errno = GRUB_ERR_NONE;
+             }
+           if (i != redundancy)
+             break;
+         }
        if (err)
-         return err;
+         return grub_errno = err;
       }
       size -= csize;
       buf = (grub_uint8_t *) buf + csize;