+int
+ext_tree_prepare_commit(struct nfs4_layoutcommit_args *arg)
+{
+ struct pnfs_block_layout *bl = BLK_LO2EXT(NFS_I(arg->inode)->layout);
+ size_t count = 0, buffer_size = PAGE_SIZE;
+ __be32 *start_p;
+ int ret;
+
+ dprintk("%s enter\n", __func__);
+
+ arg->layoutupdate_page = alloc_page(GFP_NOFS);
+ if (!arg->layoutupdate_page)
+ return -ENOMEM;
+ start_p = page_address(arg->layoutupdate_page);
+ arg->layoutupdate_pages = &arg->layoutupdate_page;
+
+retry:
+ ret = ext_tree_encode_commit(bl, start_p + 1, buffer_size, &count);
+ if (unlikely(ret)) {
+ ext_tree_free_commitdata(arg, buffer_size);
+
+ buffer_size = sizeof(__be32) + BL_EXTENT_SIZE * count;
+ count = 0;
+
+ arg->layoutupdate_pages =
+ kcalloc(DIV_ROUND_UP(buffer_size, PAGE_SIZE),
+ sizeof(struct page *), GFP_NOFS);
+ if (!arg->layoutupdate_pages)
+ return -ENOMEM;
+
+ start_p = __vmalloc(buffer_size, GFP_NOFS, PAGE_KERNEL);
+ if (!start_p) {
+ kfree(arg->layoutupdate_pages);
+ return -ENOMEM;
+ }
+
+ goto retry;
+ }
+
+ *start_p = cpu_to_be32(count);
+ arg->layoutupdate_len = sizeof(__be32) + BL_EXTENT_SIZE * count;
+
+ if (unlikely(arg->layoutupdate_pages != &arg->layoutupdate_page)) {
+ __be32 *p = start_p;
+ int i = 0;
+
+ for (p = start_p;
+ p < start_p + arg->layoutupdate_len;
+ p += PAGE_SIZE) {
+ arg->layoutupdate_pages[i++] = vmalloc_to_page(p);
+ }
+ }
+
+ dprintk("%s found %zu ranges\n", __func__, count);
+ return 0;
+}
+