}
        cow = alloc_free_block(root);
        memcpy(&cow->node, &buf->node, sizeof(buf->node));
-       cow->node.header.blocknr = cow->blocknr;
+       btrfs_set_header_blocknr(&cow->node.header, cow->blocknr);
        *cow_ret = cow;
        btrfs_inc_ref(root, buf);
        if (buf == root->node) {
  */
 static inline unsigned int leaf_data_end(struct leaf *leaf)
 {
-       unsigned int nr = leaf->header.nritems;
+       u32 nr = btrfs_header_nritems(&leaf->header);
        if (nr == 0)
                return sizeof(leaf->data);
        return leaf->items[nr-1].offset;
 int leaf_free_space(struct leaf *leaf)
 {
        int data_end = leaf_data_end(leaf);
-       int nritems = leaf->header.nritems;
+       int nritems = btrfs_header_nritems(&leaf->header);
        char *items_end = (char *)(leaf->items + nritems + 1);
        return (char *)(leaf->data + data_end) - (char *)items_end;
 }
        struct node *parent = NULL;
        struct node *node = &path->nodes[level]->node;
        int parent_slot;
+       u32 nritems = btrfs_header_nritems(&node->header);
 
        if (path->nodes[level + 1])
                parent = &path->nodes[level + 1]->node;
        parent_slot = path->slots[level + 1];
-       if (parent && node->header.nritems > 0) {
+       BUG_ON(nritems == 0);
+       if (parent) {
                struct key *parent_key;
                parent_key = &parent->keys[parent_slot];
                BUG_ON(memcmp(parent_key, node->keys, sizeof(struct key)));
-               BUG_ON(parent->blockptrs[parent_slot] != node->header.blocknr);
+               BUG_ON(parent->blockptrs[parent_slot] !=
+                      btrfs_header_blocknr(&node->header));
        }
-       BUG_ON(node->header.nritems > NODEPTRS_PER_BLOCK);
-       for (i = 0; i < node->header.nritems - 2; i++) {
+       BUG_ON(nritems > NODEPTRS_PER_BLOCK);
+       for (i = 0; nritems > 1 && i < nritems - 2; i++) {
                BUG_ON(comp_keys(&node->keys[i], &node->keys[i+1]) >= 0);
        }
        return 0;
        struct leaf *leaf = &path->nodes[level]->leaf;
        struct node *parent = NULL;
        int parent_slot;
+       u32 nritems = btrfs_header_nritems(&leaf->header);
 
        if (path->nodes[level + 1])
                parent = &path->nodes[level + 1]->node;
        parent_slot = path->slots[level + 1];
-       if (parent && leaf->header.nritems > 0) {
+       BUG_ON(leaf_free_space(leaf) < 0);
+
+       if (nritems == 0)
+               return 0;
+
+       if (parent) {
                struct key *parent_key;
                parent_key = &parent->keys[parent_slot];
                BUG_ON(memcmp(parent_key, &leaf->items[0].key,
                       sizeof(struct key)));
-               BUG_ON(parent->blockptrs[parent_slot] != leaf->header.blocknr);
+               BUG_ON(parent->blockptrs[parent_slot] !=
+                      btrfs_header_blocknr(&leaf->header));
        }
-       for (i = 0; i < leaf->header.nritems - 2; i++) {
+       for (i = 0; nritems > 1 && i < nritems - 2; i++) {
                BUG_ON(comp_keys(&leaf->items[i].key,
                                 &leaf->items[i+1].key) >= 0);
                BUG_ON(leaf->items[i].offset != leaf->items[i + 1].offset +
                                LEAF_DATA_SIZE);
                }
        }
-       BUG_ON(leaf_free_space(leaf) < 0);
        return 0;
 }
 
  */
 int bin_search(struct node *c, struct key *key, int *slot)
 {
-       if (is_leaf(c->header.flags)) {
+       if (btrfs_is_leaf(c)) {
                struct leaf *l = (struct leaf *)c;
                return generic_bin_search((void *)l->items, sizeof(struct item),
-                                         key, c->header.nritems, slot);
+                                         key, btrfs_header_nritems(&c->header),
+                                         slot);
        } else {
                return generic_bin_search((void *)c->keys, sizeof(struct key),
-                                         key, c->header.nritems, slot);
+                                         key, btrfs_header_nritems(&c->header),
+                                         slot);
        }
        return -1;
 }
        struct node *node = &parent_buf->node;
        if (slot < 0)
                return NULL;
-       if (slot >= node->header.nritems)
+       if (slot >= btrfs_header_nritems(&node->header))
                return NULL;
        return read_tree_block(root, node->blockptrs[slot]);
 }
                struct tree_buffer *child;
                u64 blocknr = mid_buf->blocknr;
 
-               if (mid->header.nritems != 1)
+               if (btrfs_header_nritems(&mid->header) != 1)
                        return 0;
 
                /* promote the child to a root */
        }
        parent = &parent_buf->node;
 
-       if (mid->header.nritems > NODEPTRS_PER_BLOCK / 4)
+       if (btrfs_header_nritems(&mid->header) > NODEPTRS_PER_BLOCK / 4)
                return 0;
 
        left_buf = read_node_slot(root, parent_buf, pslot - 1);
                btrfs_cow_block(root, left_buf, parent_buf,
                                pslot - 1, &left_buf);
                left = &left_buf->node;
-               orig_slot += left->header.nritems;
+               orig_slot += btrfs_header_nritems(&left->header);
                wret = push_node_left(root, left_buf, mid_buf);
                if (wret < 0)
                        ret = wret;
                wret = push_node_left(root, mid_buf, right_buf);
                if (wret < 0)
                        ret = wret;
-               if (right->header.nritems == 0) {
+               if (btrfs_header_nritems(&right->header) == 0) {
                        u64 blocknr = right_buf->blocknr;
                        tree_block_release(root, right_buf);
                        clean_tree_block(root, right_buf);
                        BUG_ON(list_empty(&parent_buf->dirty));
                }
        }
-       if (mid->header.nritems == 1) {
+       if (btrfs_header_nritems(&mid->header) == 1) {
                /*
                 * we're not allowed to leave a node with one item in the
                 * tree during a delete.  A deletion from lower in the tree
                        ret = wret;
                BUG_ON(wret == 1);
        }
-       if (mid->header.nritems == 0) {
+       if (btrfs_header_nritems(&mid->header) == 0) {
                /* we've managed to empty the middle node, drop it */
                u64 blocknr = mid_buf->blocknr;
                tree_block_release(root, mid_buf);
 
        /* update the path */
        if (left_buf) {
-               if (left->header.nritems > orig_slot) {
+               if (btrfs_header_nritems(&left->header) > orig_slot) {
                        left_buf->count++; // released below
                        path->nodes[level] = left_buf;
                        path->slots[level + 1] -= 1;
                        if (mid_buf)
                                tree_block_release(root, mid_buf);
                } else {
-                       orig_slot -= left->header.nritems;
+                       orig_slot -= btrfs_header_nritems(&left->header);
                        path->slots[level] = orig_slot;
                }
        }
        b = root->node;
        b->count++;
        while (b) {
-               level = node_level(b->node.header.flags);
+               level = btrfs_header_level(&b->node.header);
                if (cow) {
                        int wret;
                        wret = btrfs_cow_block(root, b, p->nodes[level + 1],
                if (ret)
                        return -1;
                ret = bin_search(c, key, &slot);
-               if (!is_leaf(c->header.flags)) {
+               if (!btrfs_is_leaf(c)) {
                        if (ret && slot > 0)
                                slot -= 1;
                        p->slots[level] = slot;
-                       if (ins_len > 0 &&
-                           c->header.nritems == NODEPTRS_PER_BLOCK) {
+                       if (ins_len > 0 && btrfs_header_nritems(&c->header) ==
+                           NODEPTRS_PER_BLOCK) {
                                int sret = split_node(root, p, level);
                                BUG_ON(sret > 0);
                                if (sret)
                                        goto again;
                                c = &b->node;
                                slot = p->slots[level];
-                               BUG_ON(c->header.nritems == 1);
+                               BUG_ON(btrfs_header_nritems(&c->header) == 1);
                        }
                        b = read_tree_block(root, c->blockptrs[slot]);
                } else {
        int dst_nritems;
        int ret = 0;
 
-       src_nritems = src->header.nritems;
-       dst_nritems = dst->header.nritems;
+       src_nritems = btrfs_header_nritems(&src->header);
+       dst_nritems = btrfs_header_nritems(&dst->header);
        push_items = NODEPTRS_PER_BLOCK - dst_nritems;
        if (push_items <= 0) {
                return 1;
                memmove(src->blockptrs, src->blockptrs + push_items,
                        (src_nritems - push_items) * sizeof(u64));
        }
-       src->header.nritems -= push_items;
-       dst->header.nritems += push_items;
-
+       btrfs_set_header_nritems(&src->header, src_nritems - push_items);
+       btrfs_set_header_nritems(&dst->header, dst_nritems + push_items);
        BUG_ON(list_empty(&src_buf->dirty));
        BUG_ON(list_empty(&dst_buf->dirty));
        return ret;
        int dst_nritems;
        int ret = 0;
 
-       src_nritems = src->header.nritems;
-       dst_nritems = dst->header.nritems;
+       src_nritems = btrfs_header_nritems(&src->header);
+       dst_nritems = btrfs_header_nritems(&dst->header);
        push_items = NODEPTRS_PER_BLOCK - dst_nritems;
        if (push_items <= 0) {
                return 1;
        memcpy(dst->blockptrs, src->blockptrs + src_nritems - push_items,
                push_items * sizeof(u64));
 
-       src->header.nritems -= push_items;
-       dst->header.nritems += push_items;
+       btrfs_set_header_nritems(&src->header, src_nritems - push_items);
+       btrfs_set_header_nritems(&dst->header, dst_nritems + push_items);
 
        BUG_ON(list_empty(&src_buf->dirty));
        BUG_ON(list_empty(&dst_buf->dirty));
        t = alloc_free_block(root);
        c = &t->node;
        memset(c, 0, sizeof(c));
-       c->header.nritems = 1;
-       c->header.flags = node_level(level);
-       c->header.blocknr = t->blocknr;
-       c->header.parentid = root->node->node.header.parentid;
+       btrfs_set_header_nritems(&c->header, 1);
+       btrfs_set_header_level(&c->header, level);
+       btrfs_set_header_blocknr(&c->header, t->blocknr);
+       btrfs_set_header_parentid(&c->header,
+                              btrfs_header_parentid(&root->node->node.header));
        lower = &path->nodes[level-1]->node;
-       if (is_leaf(lower->header.flags))
+       if (btrfs_is_leaf(lower))
                lower_key = &((struct leaf *)lower)->items[0].key;
        else
                lower_key = lower->keys;
 
        BUG_ON(!path->nodes[level]);
        lower = &path->nodes[level]->node;
-       nritems = lower->header.nritems;
+       nritems = btrfs_header_nritems(&lower->header);
        if (slot > nritems)
                BUG();
        if (nritems == NODEPTRS_PER_BLOCK)
        }
        memcpy(lower->keys + slot, key, sizeof(struct key));
        lower->blockptrs[slot] = blocknr;
-       lower->header.nritems++;
+       btrfs_set_header_nritems(&lower->header, nritems + 1);
        if (lower->keys[1].objectid == 0)
                        BUG();
        BUG_ON(list_empty(&path->nodes[level]->dirty));
        int mid;
        int ret;
        int wret;
+       u32 c_nritems;
 
        t = path->nodes[level];
        c = &t->node;
                if (ret)
                        return ret;
        }
+       c_nritems = btrfs_header_nritems(&c->header);
        split_buffer = alloc_free_block(root);
        split = &split_buffer->node;
-       split->header.flags = c->header.flags;
-       split->header.blocknr = split_buffer->blocknr;
-       split->header.parentid = root->node->node.header.parentid;
-       mid = (c->header.nritems + 1) / 2;
+       btrfs_set_header_flags(&split->header, btrfs_header_flags(&c->header));
+       btrfs_set_header_blocknr(&split->header, split_buffer->blocknr);
+       btrfs_set_header_parentid(&split->header,
+                              btrfs_header_parentid(&root->node->node.header));
+       mid = (c_nritems + 1) / 2;
        memcpy(split->keys, c->keys + mid,
-               (c->header.nritems - mid) * sizeof(struct key));
+               (c_nritems - mid) * sizeof(struct key));
        memcpy(split->blockptrs, c->blockptrs + mid,
-               (c->header.nritems - mid) * sizeof(u64));
-       split->header.nritems = c->header.nritems - mid;
-       c->header.nritems = mid;
+               (c_nritems - mid) * sizeof(u64));
+       btrfs_set_header_nritems(&split->header, c_nritems - mid);
+       btrfs_set_header_nritems(&c->header, mid);
        ret = 0;
 
        BUG_ON(list_empty(&t->dirty));
        int push_space = 0;
        int push_items = 0;
        struct item *item;
+       u32 left_nritems;
+       u32 right_nritems;
 
        slot = path->slots[1];
        if (!path->nodes[1]) {
                return 1;
        }
        upper = path->nodes[1];
-       if (slot >= upper->node.header.nritems - 1) {
+       if (slot >= btrfs_header_nritems(&upper->node.header) - 1) {
                return 1;
        }
        right_buf = read_tree_block(root, upper->node.blockptrs[slot + 1]);
                return 1;
        }
 
-       for (i = left->header.nritems - 1; i >= 0; i--) {
+       left_nritems = btrfs_header_nritems(&left->header);
+       for (i = left_nritems - 1; i >= 0; i--) {
                item = left->items + i;
                if (path->slots[0] == i)
                        push_space += data_size + sizeof(*item);
                tree_block_release(root, right_buf);
                return 1;
        }
+       right_nritems = btrfs_header_nritems(&right->header);
        /* push left to right */
-       push_space = left->items[left->header.nritems - push_items].offset +
-                    left->items[left->header.nritems - push_items].size;
+       push_space = left->items[left_nritems - push_items].offset +
+                    left->items[left_nritems - push_items].size;
        push_space -= leaf_data_end(left);
        /* make room in the right data area */
        memmove(right->data + leaf_data_end(right) - push_space,
                left->data + leaf_data_end(left),
                push_space);
        memmove(right->items + push_items, right->items,
-               right->header.nritems * sizeof(struct item));
+               right_nritems * sizeof(struct item));
        /* copy the items from left to right */
-       memcpy(right->items, left->items + left->header.nritems - push_items,
+       memcpy(right->items, left->items + left_nritems - push_items,
                push_items * sizeof(struct item));
 
        /* update the item pointers */
-       right->header.nritems += push_items;
+       right_nritems += push_items;
+       btrfs_set_header_nritems(&right->header, right_nritems);
        push_space = LEAF_DATA_SIZE;
-       for (i = 0; i < right->header.nritems; i++) {
+       for (i = 0; i < right_nritems; i++) {
                right->items[i].offset = push_space - right->items[i].size;
                push_space = right->items[i].offset;
        }
-       left->header.nritems -= push_items;
+       left_nritems -= push_items;
+       btrfs_set_header_nritems(&left->header, left_nritems);
 
        BUG_ON(list_empty(&left_buf->dirty));
        BUG_ON(list_empty(&right_buf->dirty));
        BUG_ON(list_empty(&upper->dirty));
 
        /* then fixup the leaf pointer in the path */
-       if (path->slots[0] >= left->header.nritems) {
-               path->slots[0] -= left->header.nritems;
+       if (path->slots[0] >= left_nritems) {
+               path->slots[0] -= left_nritems;
                tree_block_release(root, path->nodes[0]);
                path->nodes[0] = right_buf;
                path->slots[1] += 1;
        int push_space = 0;
        int push_items = 0;
        struct item *item;
-       int old_left_nritems;
+       u32 old_left_nritems;
        int ret = 0;
        int wret;
 
                return 1;
        }
 
-       for (i = 0; i < right->header.nritems; i++) {
+       for (i = 0; i < btrfs_header_nritems(&right->header); i++) {
                item = right->items + i;
                if (path->slots[0] == i)
                        push_space += data_size + sizeof(*item);
                return 1;
        }
        /* push data from right to left */
-       memcpy(left->items + left->header.nritems,
+       memcpy(left->items + btrfs_header_nritems(&left->header),
                right->items, push_items * sizeof(struct item));
        push_space = LEAF_DATA_SIZE - right->items[push_items -1].offset;
        memcpy(left->data + leaf_data_end(left) - push_space,
                right->data + right->items[push_items - 1].offset,
                push_space);
-       old_left_nritems = left->header.nritems;
+       old_left_nritems = btrfs_header_nritems(&left->header);
        BUG_ON(old_left_nritems < 0);
 
        for(i = old_left_nritems; i < old_left_nritems + push_items; i++) {
                left->items[i].offset -= LEAF_DATA_SIZE -
                        left->items[old_left_nritems -1].offset;
        }
-       left->header.nritems += push_items;
+       btrfs_set_header_nritems(&left->header, old_left_nritems + push_items);
 
        /* fixup right node */
        push_space = right->items[push_items-1].offset - leaf_data_end(right);
        memmove(right->data + LEAF_DATA_SIZE - push_space, right->data +
                leaf_data_end(right), push_space);
        memmove(right->items, right->items + push_items,
-               (right->header.nritems - push_items) * sizeof(struct item));
-       right->header.nritems -= push_items;
+               (btrfs_header_nritems(&right->header) - push_items) *
+               sizeof(struct item));
+       btrfs_set_header_nritems(&right->header,
+                                btrfs_header_nritems(&right->header) -
+                                push_items);
        push_space = LEAF_DATA_SIZE;
 
-       for (i = 0; i < right->header.nritems; i++) {
+       for (i = 0; i < btrfs_header_nritems(&right->header); i++) {
                right->items[i].offset = push_space - right->items[i].size;
                push_space = right->items[i].offset;
        }
 {
        struct tree_buffer *l_buf;
        struct leaf *l;
-       int nritems;
+       u32 nritems;
        int mid;
        int slot;
        struct leaf *right;
                        return ret;
        }
        slot = path->slots[0];
-       nritems = l->header.nritems;
+       nritems = btrfs_header_nritems(&l->header);
        mid = (nritems + 1)/ 2;
        right_buffer = alloc_free_block(root);
        BUG_ON(!right_buffer);
                        LEAF_DATA_SIZE)
                        BUG();
        }
-       right->header.nritems = nritems - mid;
-       right->header.blocknr = right_buffer->blocknr;
-       right->header.flags = node_level(0);
-       right->header.parentid = root->node->node.header.parentid;
+       btrfs_set_header_nritems(&right->header, nritems - mid);
+       btrfs_set_header_blocknr(&right->header, right_buffer->blocknr);
+       btrfs_set_header_level(&right->header, 0);
+       btrfs_set_header_parentid(&right->header,
+                              btrfs_header_parentid(&root->node->node.header));
        data_copy_size = l->items[mid].offset + l->items[mid].size -
                         leaf_data_end(l);
        memcpy(right->items, l->items + mid,
        rt_data_off = LEAF_DATA_SIZE -
                     (l->items[mid].offset + l->items[mid].size);
 
-       for (i = 0; i < right->header.nritems; i++)
+       for (i = 0; i < btrfs_header_nritems(&right->header); i++)
                right->items[i].offset += rt_data_off;
 
-       l->header.nritems = mid;
+       btrfs_set_header_nritems(&l->header, mid);
        ret = 0;
        wret = insert_ptr(root, path, &right->items[0].key,
                          right_buffer->blocknr, path->slots[1] + 1, 1);
        int slot_orig;
        struct leaf *leaf;
        struct tree_buffer *leaf_buf;
-       unsigned int nritems;
+       u32 nritems;
        unsigned int data_end;
        struct ctree_path path;
 
        leaf_buf = path.nodes[0];
        leaf = &leaf_buf->leaf;
 
-       nritems = leaf->header.nritems;
+       nritems = btrfs_header_nritems(&leaf->header);
        data_end = leaf_data_end(leaf);
 
        if (leaf_free_space(leaf) <  sizeof(struct item) + data_size)
        leaf->items[slot].offset = data_end - data_size;
        leaf->items[slot].size = data_size;
        memcpy(leaf->data + data_end - data_size, data, data_size);
-       leaf->header.nritems += 1;
+       btrfs_set_header_nritems(&leaf->header, nritems + 1);
 
        ret = 0;
        if (slot == 0)
 {
        struct node *node;
        struct tree_buffer *parent = path->nodes[level];
-       int nritems;
+       u32 nritems;
        int ret = 0;
        int wret;
 
        node = &parent->node;
-       nritems = node->header.nritems;
+       nritems = btrfs_header_nritems(&node->header);
        if (slot != nritems -1) {
                memmove(node->keys + slot, node->keys + slot + 1,
                        sizeof(struct key) * (nritems - slot - 1));
                        node->blockptrs + slot + 1,
                        sizeof(u64) * (nritems - slot - 1));
        }
-       node->header.nritems--;
-       if (node->header.nritems == 0 && parent == root->node) {
-               BUG_ON(node_level(root->node->node.header.flags) != 1);
+       nritems--;
+       btrfs_set_header_nritems(&node->header, nritems);
+       if (nritems == 0 && parent == root->node) {
+               BUG_ON(btrfs_header_level(&root->node->node.header) != 1);
                /* just turn the root into a leaf and break */
-               root->node->node.header.flags = node_level(0);
+               btrfs_set_header_level(&root->node->node.header, 0);
        } else if (slot == 0) {
                wret = fixup_low_keys(root, path, node->keys, level + 1);
                if (wret)
        int dsize;
        int ret = 0;
        int wret;
+       u32 nritems;
 
        leaf_buf = path->nodes[0];
        leaf = &leaf_buf->leaf;
        slot = path->slots[0];
        doff = leaf->items[slot].offset;
        dsize = leaf->items[slot].size;
+       nritems = btrfs_header_nritems(&leaf->header);
 
-       if (slot != leaf->header.nritems - 1) {
+       if (slot != nritems - 1) {
                int i;
                int data_end = leaf_data_end(leaf);
                memmove(leaf->data + data_end + dsize,
                        leaf->data + data_end,
                        doff - data_end);
-               for (i = slot + 1; i < leaf->header.nritems; i++)
+               for (i = slot + 1; i < nritems; i++)
                        leaf->items[i].offset += dsize;
                memmove(leaf->items + slot, leaf->items + slot + 1,
                        sizeof(struct item) *
-                       (leaf->header.nritems - slot - 1));
+                       (nritems - slot - 1));
        }
-       leaf->header.nritems -= 1;
+       btrfs_set_header_nritems(&leaf->header, nritems - 1);
+       nritems--;
        /* delete the leaf if we've emptied it */
-       if (leaf->header.nritems == 0) {
+       if (nritems == 0) {
                if (leaf_buf == root->node) {
-                       leaf->header.flags = node_level(0);
+                       btrfs_set_header_level(&leaf->header, 0);
                        BUG_ON(list_empty(&leaf_buf->dirty));
                } else {
                        clean_tree_block(root, leaf_buf);
                                ret = wret;
                }
        } else {
-               int used = leaf_space_used(leaf, 0, leaf->header.nritems);
+               int used = leaf_space_used(leaf, 0, nritems);
                if (slot == 0) {
                        wret = fixup_low_keys(root, path,
                                                   &leaf->items[0].key, 1);
                        if (wret < 0)
                                ret = wret;
                        if (path->nodes[0] == leaf_buf &&
-                           leaf->header.nritems) {
+                           btrfs_header_nritems(&leaf->header)) {
                                wret = push_leaf_right(root, path, 1);
                                if (wret < 0)
                                        ret = wret;
                        }
-                       if (leaf->header.nritems == 0) {
+                       if (btrfs_header_nritems(&leaf->header) == 0) {
                                u64 blocknr = leaf_buf->blocknr;
                                clean_tree_block(root, leaf_buf);
                                wret = del_ptr(root, path, 1, slot);
                        return 1;
                slot = path->slots[level] + 1;
                c = path->nodes[level];
-               if (slot >= c->node.header.nritems) {
+               if (slot >= btrfs_header_nritems(&c->node.header)) {
                        level++;
                        continue;
                }