this is a completely useless wrapper that doesn't buy anything.

+int perthread_pages_reserve(int nrpages, int gfp)
+{
+	int i;
+	struct list_head  accumulator;
+	struct list_head *per_thread;
+
+	per_thread = get_per_thread_pages();
+	INIT_LIST_HEAD(&accumulator);
+	list_splice_init(per_thread, &accumulator);

Can probably be written much simpler as:

int perthread_pages_reserve(int nrpages, int gfp)
{
	LIST_HEAD(accumulator);
	int i;

	list_splice_init(&current->private_pages, &accumulator);

Now the big question is, what's synchronizing access to
current->private_pages?

+	for (i = 0; i < nrpages; ++i) {
+		struct page *page;
+
+		page = alloc_page(gfp);
+		if (page != NULL)
+			list_add(&page->lru, &accumulator);
+		else {
+			for (; i > 0; --i) {
+				page = list_entry(accumulator.next, struct page, lru);
+				list_del(&page->lru);
+				page_cache_release(page);
+			}
+			return -ENOMEM;
+		}
+	}

Would be much more readable with the error condition handling at the
end of the function and a goto.

+int perthread_pages_count(void)
+{
+	return current->private_pages_count;
+}
+EXPORT_SYMBOL(perthread_pages_count);

Again a completely useless wrapper.

+static inline struct page *
+perthread_pages_alloc(void)
+{
+	struct list_head *perthread_pages;
+
+	/*
+	 * try to allocate pages from the per-thread private_pages pool. No
+	 * locking is needed: this list can only be modified by the thread
+	 * itself, and not by interrupts or other threads.
+	 */
+	perthread_pages = get_per_thread_pages();
+	if (!in_interrupt() && !list_empty(perthread_pages)) {
+		struct page *page;
+
+		page = list_entry(perthread_pages->next, struct page, lru);
+		list_del(&page->lru);
+		current->private_pages_count--;
+		/*
+		 * per-thread page is already initialized, just return it.
+		 */
+		return page;
+	} else
+		return NULL;
+}

Would be written much cleaner with a single return statement and the
comment above the function, ala:

/*
 * try to allocate pages from the per-thread private_pages pool. No
 * locking is needed: this list can only be modified by the thread
 * itself, and not by interrupts or other threads.
 */
static inline struct page *perthread_pages_alloc(void)
{
	struct list_head *perthread_pages = &current->private_pages;
	struct page *page = NULL;

	if (!in_interrupt() && !list_empty(perthread_pages)) {
		page = list_entry(perthread_pages->next, struct page, lru);
		list_del(&page->lru);
		current->private_pages_count--;
	}

	return page;
}

+	if (order == 0) {
+		page = perthread_pages_alloc();
+		if (page != NULL)
+			return page;
+	}
+

You should at least move the !in_interrupt() condition out here.

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