1 files changed, 21 insertions, 16 deletions

diff --git a/fs/btrfs/mkfs.c b/fs/btrfs/mkfs.c
index 584aba44e801..fd4e5dea7e1b 100644
--- a/fs/btrfs/mkfs.c
+++ b/fs/btrfs/mkfs.c
@@ -23,17 +23,10 @@ int mkfs(int fd)
         info[0].blocknr = 16;
         info[0].objectid = 1;
         info[0].tree_root = 17;
-        info[0].alloc_extent.blocknr = 0;
-        info[0].alloc_extent.num_blocks = 64;
-        /* 0-17 are used (inclusive) */
-        info[0].alloc_extent.num_used = 18;
 
         info[1].blocknr = 16;
         info[1].objectid = 2;
-        info[1].tree_root = 64;
-        info[1].alloc_extent.blocknr = 64;
-        info[1].alloc_extent.num_blocks = 64;
-        info[1].alloc_extent.num_used = 1;
+        info[1].tree_root = 18;
         ret = pwrite(fd, info, sizeof(info),
                      CTREE_SUPER_INFO_OFFSET(CTREE_BLOCKSIZE));
         if (ret != sizeof(info))
@@ -48,24 +41,36 @@ int mkfs(int fd)
                 return -1;
 
         empty_leaf.header.parentid = 2;
-        empty_leaf.header.blocknr = 64;
-        empty_leaf.header.nritems = 2;
+        empty_leaf.header.blocknr = 18;
+        empty_leaf.header.nritems = 3;
+
+        /* item1, reserve blocks 0-16 */
         item.key.objectid = 0;
-        item.key.offset = 64;
+        item.key.offset = 17;
         item.key.flags = 0;
         item.offset = LEAF_DATA_SIZE - sizeof(struct extent_item);
         item.size = sizeof(struct extent_item);
         extent_item.refs = 1;
-        extent_item.owner = 1;
+        extent_item.owner = 0;
         memcpy(empty_leaf.items, &item, sizeof(item));
         memcpy(empty_leaf.data + item.offset, &extent_item, item.size);
-        item.key.objectid = 64;
-        item.key.offset = 64;
+
+        /* item2, give block 17 to the root */
+        item.key.objectid = 17;
+        item.key.offset = 1;
         item.offset = LEAF_DATA_SIZE - sizeof(struct extent_item) * 2;
-        extent_item.owner = 2;
+        extent_item.owner = 1;
         memcpy(empty_leaf.items + 1, &item, sizeof(item));
         memcpy(empty_leaf.data + item.offset, &extent_item, item.size);
-        ret = pwrite(fd, &empty_leaf, sizeof(empty_leaf), 64 * CTREE_BLOCKSIZE);
+
+        /* item3, give block 18 for the extent root */
+        item.key.objectid = 18;
+        item.key.offset = 1;
+        item.offset = LEAF_DATA_SIZE - sizeof(struct extent_item) * 3;
+        extent_item.owner = 2;
+        memcpy(empty_leaf.items + 2, &item, sizeof(item));
+        memcpy(empty_leaf.data + item.offset, &extent_item, item.size);
+        ret = pwrite(fd, &empty_leaf, sizeof(empty_leaf), 18 * CTREE_BLOCKSIZE);
         if (ret != sizeof(empty_leaf))
                 return -1;
         return 0;