On Tue, 23 Aug 2011 01:29:06 +0900
Akinobu Mita [off-list ref] wrote:

This adds support for highmem pages poisoning and verification to the
debug-pagealloc feature for no-architecture support.

...

 static void poison_page(struct page *page)
 {
 	void *addr;
-
-	if (PageHighMem(page)) {
-		poison_highpage(page);
-		return;
+	unsigned long flags;
+	bool highmem = PageHighMem(page);
+
+	if (highmem) {
+		local_irq_save(flags);
+		addr = kmap_atomic(page);
+	} else {
+		addr = page_address(page);
 	}
 	set_page_poison(page);
-	addr = page_address(page);
 	memset(addr, PAGE_POISON, PAGE_SIZE);
+
+	if (highmem) {
+		kunmap_atomic(addr);
+		local_irq_restore(flags);
+	}
 }

This seems more complicated than is needed.  Couldn't we just do

static void poison_page(struct page *page)
{
	void *addr;

	preempt_disable();
	addr = kmap_atomic(page);
	set_page_poison(page);
	memset(addr, PAGE_POISON, PAGE_SIZE);
	kunmap_atomic(addr);
	preempt_enable();
}

?

+		addr = kmap_atomic(page);

That reminds me - we need to convert every "kmap_atomic(p, foo)" to
"kmap_atomic(p)" then remove the kmap_atomic back-compatibility macro.

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