4 files changed, 65 insertions, 12 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 454eb88611bb..ef3583cf74d6 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -91,10 +91,12 @@ struct btrfs_super_block {
         __le64 total_blocks;
         __le64 blocks_used;
         __le64 root_dir_objectid;
+        __le64 last_device_id;
         /* fields below here vary with the underlying disk */
         __le64 device_block_start;
         __le64 device_num_blocks;
         __le64 device_root;
+        __le64 device_id;
 } __attribute__ ((__packed__));
 
 /*
@@ -230,6 +232,7 @@ struct btrfs_csum_item {
 
 struct btrfs_device_item {
         __le16 pathlen;
+        __le64 device_id;
 } __attribute__ ((__packed__));
 
 struct crypto_hash;
@@ -798,6 +801,28 @@ static inline void btrfs_set_super_root_dir(struct btrfs_super_block *s, u64
         s->root_dir_objectid = cpu_to_le64(val);
 }
 
+static inline u64 btrfs_super_last_device_id(struct btrfs_super_block *s)
+{
+        return le64_to_cpu(s->last_device_id);
+}
+
+static inline void btrfs_set_super_last_device_id(struct btrfs_super_block *s,
+                                                  u64 val)
+{
+        s->last_device_id = cpu_to_le64(val);
+}
+
+static inline u64 btrfs_super_device_id(struct btrfs_super_block *s)
+{
+        return le64_to_cpu(s->device_id);
+}
+
+static inline void btrfs_set_super_device_id(struct btrfs_super_block *s,
+                                                  u64 val)
+{
+        s->device_id = cpu_to_le64(val);
+}
+
 static inline u64 btrfs_super_device_block_start(struct btrfs_super_block *s)
 {
         return le64_to_cpu(s->device_block_start);
@@ -910,6 +935,17 @@ static inline void btrfs_set_device_pathlen(struct btrfs_device_item *d,
         d->pathlen = cpu_to_le16(val);
 }
 
+static inline u64 btrfs_device_id(struct btrfs_device_item *d)
+{
+        return le64_to_cpu(d->device_id);
+}
+
+static inline void btrfs_set_device_id(struct btrfs_device_item *d,
+                                                u64 val)
+{
+        d->device_id = cpu_to_le64(val);
+}
+
 static inline struct btrfs_root *btrfs_sb(struct super_block *sb)
 {
         return sb->s_fs_info;
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 3ba4df20c913..06b969c14625 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -13,11 +13,13 @@
 struct dev_lookup {
         u64 block_start;
         u64 num_blocks;
+        u64 device_id;
         struct block_device *bdev;
 };
 
 int btrfs_insert_dev_radix(struct btrfs_root *root,
                            struct block_device *bdev,
+                           u64 device_id,
                            u64 block_start,
                            u64 num_blocks)
 {
@@ -31,6 +33,7 @@ int btrfs_insert_dev_radix(struct btrfs_root *root,
         lookup->block_start = block_start;
         lookup->num_blocks = num_blocks;
         lookup->bdev = bdev;
+        lookup->device_id = device_id;
 printk("inserting %s into dev radix %Lu %Lu\n", bdevname(bdev, b), block_start, num_blocks);
 
         ret = radix_tree_insert(&root->fs_info->dev_radix, block_start +
@@ -418,17 +421,14 @@ printk("all worked\n");
         return root;
 }
 
-int btrfs_open_disk(struct btrfs_root *root, u64 block_start, u64 num_blocks,
-                    char *filename, int name_len)
+static int btrfs_open_disk(struct btrfs_root *root, u64 device_id,
+                           u64 block_start, u64 num_blocks,
+                           char *filename, int name_len)
 {
         char *null_filename;
         struct block_device *bdev;
         int ret;
 
-        if (block_start == 0) {
-printk("skipping disk with block_start == 0\n");
-return 0;
-        }
         null_filename = kmalloc(name_len + 1, GFP_NOFS);
         if (!null_filename)
                 return -ENOMEM;
@@ -441,7 +441,8 @@ return 0;
                 goto out;
         }
         set_blocksize(bdev, root->fs_info->sb->s_blocksize);
-        ret = btrfs_insert_dev_radix(root, bdev, block_start, num_blocks);
+        ret = btrfs_insert_dev_radix(root, bdev, device_id,
+                                     block_start, num_blocks);
         BUG_ON(ret);
         ret = 0;
 out:
@@ -490,10 +491,14 @@ static int read_device_info(struct btrfs_root *root)
                 }
                 dev_item = btrfs_item_ptr(leaf, slot, struct btrfs_device_item);
 printk("found key %Lu %Lu\n", key.objectid, key.offset);
-                ret = btrfs_open_disk(root, key.objectid, key.offset,
-                                      (char *)(dev_item + 1),
-                                      btrfs_device_pathlen(dev_item));
-                BUG_ON(ret);
+                if (btrfs_device_id(dev_item) !=
+                    btrfs_super_device_id(root->fs_info->disk_super)) {
+                        ret = btrfs_open_disk(root, btrfs_device_id(dev_item),
+                                              key.objectid, key.offset,
+                                              (char *)(dev_item + 1),
+                                              btrfs_device_pathlen(dev_item));
+                        BUG_ON(ret);
+                }
                 path->slots[0]++;
         }
         btrfs_free_path(path);
@@ -556,6 +561,7 @@ struct btrfs_root *open_ctree(struct super_block *sb)
         dev_lookup->block_start = 0;
         dev_lookup->num_blocks = (u32)-2;
         dev_lookup->bdev = sb->s_bdev;
+        dev_lookup->device_id = 0;
         ret = radix_tree_insert(&fs_info->dev_radix, (u32)-2, dev_lookup);
         BUG_ON(ret);
         fs_info->sb_buffer = read_tree_block(tree_root,
@@ -575,6 +581,8 @@ struct btrfs_root *open_ctree(struct super_block *sb)
         radix_tree_delete(&fs_info->dev_radix, (u32)-2);
         dev_lookup->block_start = btrfs_super_device_block_start(disk_super);
         dev_lookup->num_blocks = btrfs_super_device_num_blocks(disk_super);
+        dev_lookup->device_id = btrfs_super_device_id(disk_super);
+
         ret = radix_tree_insert(&fs_info->dev_radix,
                                 dev_lookup->block_start +
                                 dev_lookup->num_blocks - 1, dev_lookup);
@@ -659,6 +667,7 @@ int del_fs_roots(struct btrfs_fs_info *fs_info)
         }
         return 0;
 }
+
 static int free_dev_radix(struct btrfs_fs_info *fs_info)
 {
         struct dev_lookup *lookup[8];
diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h
index aa9f56c38419..444ebb0141ae 100644
--- a/fs/btrfs/disk-io.h
+++ b/fs/btrfs/disk-io.h
@@ -44,6 +44,7 @@ struct btrfs_root *btrfs_read_fs_root(struct btrfs_fs_info *fs_info,
 u64 bh_blocknr(struct buffer_head *bh);
 int btrfs_insert_dev_radix(struct btrfs_root *root,
                            struct block_device *bdev,
+                           u64 device_id,
                            u64 block_start,
                            u64 num_blocks);
 int btrfs_map_bh_to_logical(struct btrfs_root *root, struct buffer_head *bh,
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index c46d7eafcf62..8dcf600e39ef 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1840,7 +1840,9 @@ static int add_disk(struct btrfs_root *root, char *name, int namelen)
         u16 item_size;
         u64 num_blocks;
         u64 new_blocks;
+        u64 device_id;
         int ret;
+
 printk("adding disk %s\n", name);
         path = btrfs_alloc_path();
         if (!path)
@@ -1875,9 +1877,14 @@ printk("insert failed %d\n", ret);
                                   path->slots[0], struct btrfs_device_item);
         btrfs_set_device_pathlen(dev_item, namelen);
         memcpy(dev_item + 1, name, namelen);
+
+        device_id = btrfs_super_last_device_id(root->fs_info->disk_super) + 1;
+        btrfs_set_super_last_device_id(root->fs_info->disk_super, device_id);
+        btrfs_set_device_id(dev_item, device_id);
         mark_buffer_dirty(path->nodes[0]);
 
-        ret = btrfs_insert_dev_radix(root, bdev, num_blocks, new_blocks);
+        ret = btrfs_insert_dev_radix(root, bdev, device_id, num_blocks,
+                                     new_blocks);
 
         if (!ret) {
                 btrfs_set_super_total_blocks(root->fs_info->disk_super,