+	if (!bv)
+		return -ENOMEM;
+
+	pages = (void *)(bv + npages);

I think this cast should be to struct page **… not void *.

+	npages = alloc_pages_bulk_array(GFP_USER, npages, pages);
+	if (!npages) {
+		kfree(bv);
+		return -ENOMEM;
+	}

+	reclaim = npages * PAGE_SIZE;
+	remain = 0;
+	if (ret > 0) {
+		reclaim -= ret;
+		remain = ret;

...

+	/* Free any pages that didn't get touched at all. */
+	reclaim /= PAGE_SIZE;

Any reason not to keep reclaim in PAGE_SIZE units to start with?