Btrfs: Block sized tree extents and extent deletion

Signed-off-by: Chris Mason <chris.mason@oracle.com>

5 files changed, 252 insertions, 135 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 1b4e82d8074d..f0abcf1f3939 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -8,9 +8,12 @@
 #define SEARCH_READ 0
 #define SEARCH_WRITE 1
 
-static int refill_alloc_extent(struct ctree_root *root);
+#define CTREE_EXTENT_PENDING 0
+
 int split_node(struct ctree_root *root, struct ctree_path *path, int level);
 int split_leaf(struct ctree_root *root, struct ctree_path *path, int data_size);
+struct tree_buffer *alloc_free_block(struct ctree_root *root);
+int free_extent(struct ctree_root *root, u64 blocknr, u64 num_blocks);
 
 static inline void init_path(struct ctree_path *p)
 {
@@ -682,8 +685,6 @@ int insert_item(struct ctree_root *root, struct key *key,
         unsigned int data_end;
         struct ctree_path path;
 
-        refill_alloc_extent(root);
-
         /* create a root if there isn't one */
         if (!root->node)
                 BUG();
@@ -756,6 +757,7 @@ int del_ptr(struct ctree_root *root, struct ctree_path *path, int level)
         struct tree_buffer *t;
         struct node *node;
         int nritems;
+        u64 blocknr;
 
         while(1) {
                 t = path->nodes[level];
@@ -774,6 +776,7 @@ int del_ptr(struct ctree_root *root, struct ctree_path *path, int level)
                 }
                 node->header.nritems--;
                 write_tree_block(root, t);
+                blocknr = t->blocknr;
                 if (node->header.nritems != 0) {
                         int tslot;
                         if (slot == 0)
@@ -799,6 +802,7 @@ int del_ptr(struct ctree_root *root, struct ctree_path *path, int level)
                         break;
                 }
                 level++;
+                free_extent(root, blocknr, 1);
                 if (!path->nodes[level])
                         BUG();
         }
@@ -841,8 +845,10 @@ int del_item(struct ctree_root *root, struct ctree_path *path)
                 if (leaf_buf == root->node) {
                         leaf->header.flags = node_level(0);
                         write_tree_block(root, leaf_buf);
-                } else
+                } else {
                         del_ptr(root, path, 1);
+                        free_extent(root, leaf_buf->blocknr, 1);
+                }
         } else {
                 if (slot == 0)
                         fixup_low_keys(root, path, &leaf->items[0].key, 1);
@@ -867,6 +873,72 @@ int del_item(struct ctree_root *root, struct ctree_path *path)
         return 0;
 }
 
+static int del_pending_extents(struct ctree_root *extent_root)
+{
+        int ret;
+        struct key key;
+        struct tree_buffer *gang[4];
+        int i;
+        struct ctree_path path;
+
+        while(1) {
+                ret = radix_tree_gang_lookup_tag(&extent_root->cache_radix,
+                                                 (void **)gang, 0, ARRAY_SIZE(gang),
+                                                 CTREE_EXTENT_PENDING);
+                if (!ret)
+                        break;
+                for (i = 0; i < ret; i++) {
+                        key.objectid = gang[i]->blocknr;
+                        key.flags = 0;
+                        key.offset = 1;
+                        init_path(&path);
+                        ret = search_slot(extent_root, &key, &path, 0);
+                        if (ret) {
+                                BUG();
+                                // FIXME undo it and return sane
+                                return ret;
+                        }
+                        ret = del_item(extent_root, &path);
+                        if (ret) {
+                                BUG();
+                                return ret;
+                        }
+                        release_path(extent_root, &path);
+                        radix_tree_tag_clear(&extent_root->cache_radix, gang[i]->blocknr,
+                                                CTREE_EXTENT_PENDING);
+                        tree_block_release(extent_root, gang[i]);
+                }
+        }
+        return 0;
+}
+
+int free_extent(struct ctree_root *root, u64 blocknr, u64 num_blocks)
+{
+        struct ctree_path path;
+        struct key key;
+        struct ctree_root *extent_root = root->extent_root;
+        struct tree_buffer *t;
+        int pending_ret;
+        int ret;
+
+        key.objectid = blocknr;
+        key.flags = 0;
+        key.offset = num_blocks;
+        if (root == extent_root) {
+                t = read_tree_block(root, key.objectid);
+                radix_tree_tag_set(&root->cache_radix, key.objectid, CTREE_EXTENT_PENDING);
+                return 0;
+        }
+        init_path(&path);
+        ret = search_slot(extent_root, &key, &path, 0);
+        if (ret)
+                BUG();
+        ret = del_item(extent_root, &path);
+        release_path(extent_root, &path);
+        pending_ret = del_pending_extents(root->extent_root);
+        return ret ? ret : pending_ret;
+}
+
 int next_leaf(struct ctree_root *root, struct ctree_path *path)
 {
         int slot;
@@ -904,8 +976,8 @@ int next_leaf(struct ctree_root *root, struct ctree_path *path)
         return 0;
 }
 
-int alloc_extent(struct ctree_root *orig_root, u64 num_blocks, u64 search_start,
-                 u64 search_end, u64 owner, struct key *ins)
+int find_free_extent(struct ctree_root *orig_root, u64 num_blocks, u64 search_start,
+                         u64 search_end, struct key *ins)
 {
         struct ctree_path path;
         struct key *key;
@@ -915,15 +987,13 @@ int alloc_extent(struct ctree_root *orig_root, u64 num_blocks, u64 search_start,
         u64 last_block;
         int start_found = 0;
         struct leaf *l;
-        struct extent_item extent_item;
         struct ctree_root * root = orig_root->extent_root;
 
         init_path(&path);
         ins->objectid = search_start;
         ins->offset = 0;
         ins->flags = 0;
-
-        ret = search_slot(root, ins, &path, sizeof(struct extent_item));
+        ret = search_slot(root, ins, &path, 0);
         while (1) {
                 l = &path.nodes[0]->leaf;
                 slot = path.slots[0];
@@ -938,6 +1008,7 @@ int alloc_extent(struct ctree_root *orig_root, u64 num_blocks, u64 search_start,
                                 ins->objectid = search_start;
                                 ins->offset = num_blocks;
                                 hole_size = search_end - search_start;
+                                start_found = 1;
                                 goto insert;
                         }
                         ins->objectid = last_block;
@@ -956,51 +1027,119 @@ int alloc_extent(struct ctree_root *orig_root, u64 num_blocks, u64 search_start,
                 } else
                         start_found = 1;
                 last_block = key->objectid + key->offset;
+insert_failed:
                 path.slots[0]++;
         }
         // FIXME -ENOSPC
 insert:
+        if (orig_root->extent_root == orig_root) {
+                BUG_ON(num_blocks != 1);
+                if ((root->current_insert.objectid <= ins->objectid &&
+                    root->current_insert.objectid + root->current_insert.offset >
+                    ins->objectid) ||
+                   (root->current_insert.objectid > ins->objectid &&
+                    root->current_insert.objectid <= ins->objectid + ins->offset) ||
+                   radix_tree_tag_get(&root->cache_radix, ins->objectid,
+                                      CTREE_EXTENT_PENDING)) {
+                        last_block = ins->objectid + 1;
+                        search_start = last_block;
+                        goto insert_failed;
+                }
+        }
         release_path(root, &path);
+        if (ins->offset != 1)
+                BUG();
+        return 0;
+}
+
+static int insert_pending_extents(struct ctree_root *extent_root)
+{
+        int ret;
+        struct key key;
+        struct extent_item item;
+        struct tree_buffer *gang[4];
+        int i;
+
+        // FIXME -ENOSPC
+        item.refs = 1;
+        item.owner = extent_root->node->node.header.parentid;
+        while(1) {
+                ret = radix_tree_gang_lookup_tag(&extent_root->cache_radix,
+                                                 (void **)gang, 0, ARRAY_SIZE(gang),
+                                                 CTREE_EXTENT_PENDING);
+                if (!ret)
+                        break;
+                for (i = 0; i < ret; i++) {
+                        key.objectid = gang[i]->blocknr;
+                        key.flags = 0;
+                        key.offset = 1;
+                        ret = insert_item(extent_root, &key, &item, sizeof(item));
+                        if (ret) {
+                                BUG();
+                                // FIXME undo it and return sane
+                                return ret;
+                        }
+                        radix_tree_tag_clear(&extent_root->cache_radix, gang[i]->blocknr,
+                                                CTREE_EXTENT_PENDING);
+                        tree_block_release(extent_root, gang[i]);
+                }
+        }
+        return 0;
+}
+
+int alloc_extent(struct ctree_root *root, u64 num_blocks, u64 search_start,
+                         u64 search_end, u64 owner, struct key *ins, struct tree_buffer **buf)
+{
+        int ret;
+        int pending_ret;
+        struct extent_item extent_item;
+
         extent_item.refs = 1;
         extent_item.owner = owner;
-        if (root == orig_root && root->reserve_extent->num_blocks == 0) {
-                root->reserve_extent->blocknr = ins->objectid;
-                root->reserve_extent->num_blocks = ins->offset;
-                root->reserve_extent->num_used = 0;
+
+        ret = find_free_extent(root, num_blocks, search_start, search_end, ins);
+        if (ret)
+                return ret;
+
+        if (root != root->extent_root) {
+                memcpy(&root->extent_root->current_insert, ins, sizeof(*ins));
+                ret = insert_item(root->extent_root, ins, &extent_item, sizeof(extent_item));
+                memset(&root->extent_root->current_insert, 0, sizeof(struct key));
+                pending_ret = insert_pending_extents(root->extent_root);
+                if (ret)
+                        return ret;
+                if (pending_ret)
+                        return pending_ret;
+                *buf = find_tree_block(root, ins->objectid);
+                return 0;
         }
-        ret = insert_item(root->extent_root, ins, &extent_item, sizeof(extent_item));
-        return ret;
+        /* we're allocating an extent for the extent tree, don't recurse */
+        BUG_ON(ins->offset != 1);
+        *buf = find_tree_block(root, ins->objectid);
+        BUG_ON(!*buf);
+        radix_tree_tag_set(&root->cache_radix, ins->objectid, CTREE_EXTENT_PENDING);
+        (*buf)->count++;
+        return 0;
+
 }
 
-static int refill_alloc_extent(struct ctree_root *root)
+struct tree_buffer *alloc_free_block(struct ctree_root *root)
 {
-        struct alloc_extent *ae = root->alloc_extent;
-        struct key key;
+        struct key ins;
         int ret;
-        int min_blocks = MAX_LEVEL * 2;
+        struct tree_buffer *buf = NULL;
 
-        if (ae->num_blocks > ae->num_used && ae->num_blocks - ae->num_used >
-            min_blocks)
-                return 0;
-        ae = root->reserve_extent;
-        if (ae->num_blocks > ae->num_used) {
-                if (root->alloc_extent->num_blocks == 0) {
-                        /* we should swap reserve/alloc_extent when alloc
-                         * fills up
-                         */
-                        BUG();
-                }
-                if (ae->num_blocks - ae->num_used < min_blocks)
-                        BUG();
-                return 0;
+        ret = alloc_extent(root, 1, 0, (unsigned long)-1, root->node->node.header.parentid,
+                           &ins, &buf);
+
+        if (ret) {
+                BUG();
+                return NULL;
         }
-        ret = alloc_extent(root,
-                           min_blocks * 2, 0, (unsigned long)-1,
-                           root->node->node.header.parentid, &key);
-        ae->blocknr = key.objectid;
-        ae->num_blocks = key.offset;
-        ae->num_used = 0;
-        return ret;
+        if (root != root->extent_root)
+                BUG_ON(radix_tree_tag_get(&root->extent_root->cache_radix, buf->blocknr,
+                                          CTREE_EXTENT_PENDING));
+        return buf;
 }
 
 void print_leaf(struct leaf *l)
@@ -1096,6 +1235,7 @@ int main() {
         print_tree(root, root->node);
         printf("map tree\n");
         print_tree(root->extent_root, root->extent_root->node);
+        fflush(stdout);
 
         srand(55);
         for (i = 0; i < run_size; i++) {
@@ -1111,12 +1251,6 @@ int main() {
                 if (!ret)
                         tree_size++;
         }
-        printf("root used: %lu\n", root->alloc_extent->num_used);
-        printf("root tree\n");
-        // print_tree(root, root->node);
-        printf("map tree\n");
-        printf("map used: %lu\n", root->extent_root->alloc_extent->num_used);
-        // print_tree(root->extent_root, root->extent_root->node);
         write_ctree_super(root, &super);
         close_ctree(root);
 
@@ -1167,12 +1301,27 @@ int main() {
                 ret = insert_item(root, &ins, buf, strlen(buf));
                 if (!ret)
                         tree_size++;
+                if (i >= 5) {
+                        struct key ugh;
+                        ugh.objectid = 5;
+                        ugh.flags = 0;
+                        ugh.offset = 0;
+                        init_path(&path);
+                        ret = search_slot(root, &ugh, &path, 0);
+                        if (ret) {
+                                print_tree(root, root->node);
+                                printf("unable to find 5 %d\n", num);
+                                exit(1);
+                        }
+                        release_path(root, &path);
+
+                }
         }
         write_ctree_super(root, &super);
         close_ctree(root);
         root = open_ctree("dbfile", &super);
-        printf("starting search2\n");
         srand(128);
+        printf("starting search2\n");
         for (i = 0; i < run_size; i++) {
                 num = next_key(i, max_key);
                 ins.objectid = num;
@@ -1219,5 +1368,7 @@ int main() {
         write_ctree_super(root, &super);
         close_ctree(root);
         printf("tree size is now %d\n", tree_size);
+        printf("map tree\n");
+        print_tree(root->extent_root, root->extent_root->node);
         return 0;
 }
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 78407d32db78..8c32c0e9267d 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -28,21 +28,12 @@ struct header {
 
 struct tree_buffer;
 
-struct alloc_extent {
-        u64 blocknr;
-        u64 num_blocks;
-        u64 num_used;
-} __attribute__ ((__packed__));
-
 struct ctree_root {
         struct tree_buffer *node;
         struct ctree_root *extent_root;
-        struct alloc_extent *alloc_extent;
-        struct alloc_extent *reserve_extent;
+        struct key current_insert;
         int fp;
         struct radix_tree_root cache_radix;
-        struct alloc_extent ai1;
-        struct alloc_extent ai2;
 };
 
 struct ctree_root_info {
@@ -52,8 +43,6 @@ struct ctree_root_info {
         u64 tree_root; /* the tree root */
         u32 csum;
         u32 ham;
-        struct alloc_extent alloc_extent;
-        struct alloc_extent reserve_extent;
         u64 snapuuid[2]; /* root specific uuid */
 } __attribute__ ((__packed__));
 
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index a696a4278ac5..14955e440773 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -12,33 +12,13 @@
 
 static int allocated_blocks = 0;
 
-static int get_free_block(struct ctree_root *root, u64 *block)
+static int check_tree_block(struct ctree_root *root, struct tree_buffer *buf)
 {
-        struct stat st;
-        int ret = 0;
-
-        if (root->alloc_extent->num_used >= root->alloc_extent->num_blocks)
-                return -1;
-
-        *block = root->alloc_extent->blocknr + root->alloc_extent->num_used;
-        root->alloc_extent->num_used += 1;
-        if (root->alloc_extent->num_used >= root->alloc_extent->num_blocks) {
-                struct alloc_extent *ae = root->alloc_extent;
-                root->alloc_extent = root->reserve_extent;
-                root->reserve_extent = ae;
-                ae->num_blocks = 0;
-        }
-        st.st_size = 0;
-        ret = fstat(root->fp, &st);
-        if (st.st_size < (*block + 1) * CTREE_BLOCKSIZE) {
-                ret = ftruncate(root->fp,
-                                (*block + 1) * CTREE_BLOCKSIZE);
-                if (ret) {
-                        perror("ftruncate");
-                        exit(1);
-                }
-        }
-        return ret;
+        if (buf->blocknr != buf->node.header.blocknr)
+                BUG();
+        if (root->node && buf->node.header.parentid != root->node->node.header.parentid)
+                BUG();
+        return 0;
 }
 
 struct tree_buffer *alloc_tree_block(struct ctree_root *root, u64 blocknr)
@@ -61,22 +41,23 @@ struct tree_buffer *alloc_tree_block(struct ctree_root *root, u64 blocknr)
         return buf;
 }
 
-struct tree_buffer *alloc_free_block(struct ctree_root *root)
+struct tree_buffer *find_tree_block(struct ctree_root *root, u64 blocknr)
 {
-        u64 free_block;
-        int ret;
-        struct tree_buffer * buf;
-        ret = get_free_block(root, &free_block);
-        if (ret) {
-                BUG();
-                return NULL;
+        struct tree_buffer *buf;
+        buf = radix_tree_lookup(&root->cache_radix, blocknr);
+        if (buf) {
+                buf->count++;
+        } else {
+                buf = alloc_tree_block(root, blocknr);
+                if (!buf) {
+                        BUG();
+                        return NULL;
+                }
         }
-        buf = alloc_tree_block(root, free_block);
-        if (!buf)
-                BUG();
         return buf;
 }
 
+
 struct tree_buffer *read_tree_block(struct ctree_root *root, u64 blocknr)
 {
         loff_t offset = blocknr * CTREE_BLOCKSIZE;
@@ -86,20 +67,17 @@ struct tree_buffer *read_tree_block(struct ctree_root *root, u64 blocknr)
         buf = radix_tree_lookup(&root->cache_radix, blocknr);
         if (buf) {
                 buf->count++;
-                goto test;
-        }
-        buf = alloc_tree_block(root, blocknr);
-        if (!buf)
-                return NULL;
-        ret = pread(root->fp, &buf->node, CTREE_BLOCKSIZE, offset);
-        if (ret != CTREE_BLOCKSIZE) {
-                free(buf);
-                return NULL;
+        } else {
+                buf = alloc_tree_block(root, blocknr);
+                if (!buf)
+                        return NULL;
+                ret = pread(root->fp, &buf->node, CTREE_BLOCKSIZE, offset);
+                if (ret != CTREE_BLOCKSIZE) {
+                        free(buf);
+                        return NULL;
+                }
         }
-test:
-        if (buf->blocknr != buf->node.header.blocknr)
-                BUG();
-        if (root->node && buf->node.header.parentid != root->node->node.header.parentid)
+        if (check_tree_block(root, buf))
                 BUG();
         return buf;
 }
@@ -121,17 +99,10 @@ int write_tree_block(struct ctree_root *root, struct tree_buffer *buf)
 static int __setup_root(struct ctree_root *root, struct ctree_root *extent_root,
                         struct ctree_root_info *info, int fp)
 {
-        INIT_RADIX_TREE(&root->cache_radix, GFP_KERNEL);
         root->fp = fp;
         root->node = NULL;
         root->node = read_tree_block(root, info->tree_root);
         root->extent_root = extent_root;
-        memcpy(&root->ai1, &info->alloc_extent, sizeof(info->alloc_extent));
-        memcpy(&root->ai2, &info->reserve_extent, sizeof(info->reserve_extent));
-        root->alloc_extent = &root->ai1;
-        root->reserve_extent = &root->ai2;
-        printf("setup done reading root %p, used %lu available %lu\n", root, root->alloc_extent->num_used, root->alloc_extent->num_blocks);
-        printf("setup done reading root %p, reserve used %lu available %lu\n", root, root->reserve_extent->num_used, root->reserve_extent->num_blocks);
         return 0;
 }
 
@@ -147,6 +118,8 @@ struct ctree_root *open_ctree(char *filename, struct ctree_super_block *super)
                 free(root);
                 return NULL;
         }
+        INIT_RADIX_TREE(&root->cache_radix, GFP_KERNEL);
+        INIT_RADIX_TREE(&extent_root->cache_radix, GFP_KERNEL);
         ret = pread(fp, super, sizeof(struct ctree_super_block),
                      CTREE_SUPER_INFO_OFFSET(CTREE_BLOCKSIZE));
         if (ret == 0 || super->root_info.tree_root == 0) {
@@ -168,8 +141,6 @@ struct ctree_root *open_ctree(char *filename, struct ctree_super_block *super)
 static int __update_root(struct ctree_root *root, struct ctree_root_info *info)
 {
         info->tree_root = root->node->blocknr;
-        memcpy(&info->alloc_extent, root->alloc_extent, sizeof(struct alloc_extent));
-        memcpy(&info->reserve_extent, root->reserve_extent, sizeof(struct alloc_extent));
         return 0;
 }
 
@@ -201,6 +172,7 @@ int close_ctree(struct ctree_root *root)
 void tree_block_release(struct ctree_root *root, struct tree_buffer *buf)
 {
         buf->count--;
+        write_tree_block(root, buf);
         if (buf->count < 0)
                 BUG();
         if (buf->count == 0) {
diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h
index e288fe883b9a..2729b757ddc1 100644
--- a/fs/btrfs/disk-io.h
+++ b/fs/btrfs/disk-io.h
@@ -11,11 +11,11 @@ struct tree_buffer {
 };
 
 struct tree_buffer *read_tree_block(struct ctree_root *root, u64 blocknr);
+struct tree_buffer *find_tree_block(struct ctree_root *root, u64 blocknr);
 int write_tree_block(struct ctree_root *root, struct tree_buffer *buf);
 struct ctree_root *open_ctree(char *filename, struct ctree_super_block *s);
 int close_ctree(struct ctree_root *root);
 void tree_block_release(struct ctree_root *root, struct tree_buffer *buf);
-struct tree_buffer *alloc_free_block(struct ctree_root *root);
 int write_ctree_super(struct ctree_root *root, struct ctree_super_block *s);
 int mkfs(int fd);
 
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;