fuse: convert readlink to simple api

static int fuse_readlink_page(struct inode *inode, struct page *page)

{

	struct fuse_conn *fc = get_fuse_conn(inode);

	struct fuse_req *req;

	int err;

	struct fuse_page_desc desc = { .length = PAGE_SIZE - 1 };

	struct fuse_args_pages ap = {

		.num_pages = 1,

		.pages = &page,

		.descs = &desc,

	};

	char *link;

	ssize_t res;

	ap.args.opcode = FUSE_READLINK;

	ap.args.nodeid = get_node_id(inode);

	ap.args.out_pages = true;

	ap.args.out_argvar = true;

	ap.args.page_zeroing = true;

	ap.args.out_numargs = 1;

	ap.args.out_args[0].size = desc.length;

	res = fuse_simple_request(fc, &ap.args);

	req = fuse_get_req(fc, 1);

	if (IS_ERR(req))

		return PTR_ERR(req);

	req->out.page_zeroing = 1;

	req->out.argpages = 1;

	req->num_pages = 1;

	req->pages[0] = page;

	req->page_descs[0].length = PAGE_SIZE - 1;

	req->in.h.opcode = FUSE_READLINK;

	req->in.h.nodeid = get_node_id(inode);

	req->out.argvar = 1;

	req->out.numargs = 1;

	req->out.args[0].size = PAGE_SIZE - 1;

	fuse_request_send(fc, req);

	err = req->out.h.error;

	fuse_invalidate_atime(inode);

	if (!err) {

		char *link = page_address(page);

		size_t len = req->out.args[0].size;

	if (res < 0)

		return res;

		BUG_ON(len >= PAGE_SIZE);

		link[len] = '\0';

	}

	if (WARN_ON(res >= PAGE_SIZE))

		return -EIO;

	fuse_put_request(fc, req);

	fuse_invalidate_atime(inode);

	link = page_address(page);

	link[res] = '\0';

	return err;

	return 0;

}

static const char *fuse_get_link(struct dentry *dentry, struct inode *inode,