linux-kernel - Re: [PATCH -v2] debug-pagealloc: add support for highmem pages

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Message-Id: <20110825170302.81ed210c.akpm@linux-foundation.org>
Date:	Thu, 25 Aug 2011 17:03:02 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Akinobu Mita <akinobu.mita@...il.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH -v2] debug-pagealloc: add support for highmem pages

On Thu, 25 Aug 2011 23:14:09 +0900
Akinobu Mita <akinobu.mita@...il.com> wrote:

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

Sorry, I had a brainfart.  kmap_atomic() internally does the
preempt_disable() (actually pagefault_disable()).

--- a/mm/debug-pagealloc.c~debug-pagealloc-add-support-for-highmem-pages-fix
+++ a/mm/debug-pagealloc.c
@@ -23,14 +23,11 @@ static inline bool page_poison(struct pa
 
 static void poison_page(struct page *page)
 {
-	void *addr;
+	void *addr = kmap_atomic(page);
 
-	preempt_disable();
-	addr = kmap_atomic(page);
 	set_page_poison(page);
 	memset(addr, PAGE_POISON, PAGE_SIZE);
 	kunmap_atomic(addr);
-	preempt_enable();
 }
 
 static void poison_pages(struct page *page, int n)
@@ -82,12 +79,10 @@ static void unpoison_page(struct page *p
 	if (!page_poison(page))
 		return;
 
-	preempt_disable();
 	addr = kmap_atomic(page);
 	check_poison_mem(addr, PAGE_SIZE);
 	clear_page_poison(page);
 	kunmap_atomic(addr);
-	preempt_enable();
 }
 
 static void unpoison_pages(struct page *page, int n)
_

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