From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id 4F5026B004F for ; Mon, 15 Jun 2009 20:33:52 -0400 (EDT) Date: Tue, 16 Jun 2009 08:34:40 +0800 From: Wu Fengguang Subject: Re: [PATCH 10/22] HWPOISON: check and isolate corrupted free pages v2 Message-ID: <20090616003440.GA7329@localhost> References: <20090615024520.786814520@intel.com> <20090615031253.715406280@intel.com> <20090615184112.ed8e2f03.kamezawa.hiroyu@jp.fujitsu.com> <20090615101620.GA7216@localhost> <20090616085222.1545cc05.kamezawa.hiroyu@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090616085222.1545cc05.kamezawa.hiroyu@jp.fujitsu.com> Sender: owner-linux-mm@kvack.org To: KAMEZAWA Hiroyuki Cc: Andrew Morton , LKML , Andi Kleen , Ingo Molnar , Mel Gorman , Thomas Gleixner , "H. Peter Anvin" , Peter Zijlstra , Nick Piggin , Hugh Dickins , Andi Kleen , "riel@redhat.com" , "chris.mason@oracle.com" , "linux-mm@kvack.org" List-ID: On Tue, Jun 16, 2009 at 07:52:22AM +0800, KAMEZAWA Hiroyuki wrote: > On Mon, 15 Jun 2009 18:16:20 +0800 > Wu Fengguang wrote: > > > On Mon, Jun 15, 2009 at 05:41:12PM +0800, KAMEZAWA Hiroyuki wrote: > > > On Mon, 15 Jun 2009 10:45:30 +0800 > > > Wu Fengguang wrote: > > > > > > > From: Wu Fengguang > > > > > > > > If memory corruption hits the free buddy pages, we can safely ignore them. > > > > No one will access them until page allocation time, then prep_new_page() > > > > will automatically check and isolate PG_hwpoison page for us (for 0-order > > > > allocation). > > > > > > > > This patch expands prep_new_page() to check every component page in a high > > > > order page allocation, in order to completely stop PG_hwpoison pages from > > > > being recirculated. > > > > > > > > Note that the common case -- only allocating a single page, doesn't > > > > do any more work than before. Allocating > order 0 does a bit more work, > > > > but that's relatively uncommon. > > > > > > > > This simple implementation may drop some innocent neighbor pages, hopefully > > > > it is not a big problem because the event should be rare enough. > > > > > > > > This patch adds some runtime costs to high order page users. > > > > > > > > [AK: Improved description] > > > > > > > > v2: Andi Kleen: > > > > Port to -mm code > > > > Move check into separate function. > > > > Don't dump stack in bad_pages for hwpoisoned pages. > > > > > > > > Signed-off-by: Wu Fengguang > > > > Signed-off-by: Andi Kleen > > > > > > > > --- > > > > mm/page_alloc.c | 20 +++++++++++++++++++- > > > > 1 file changed, 19 insertions(+), 1 deletion(-) > > > > > > > > --- sound-2.6.orig/mm/page_alloc.c > > > > +++ sound-2.6/mm/page_alloc.c > > > > @@ -233,6 +233,12 @@ static void bad_page(struct page *page) > > > > static unsigned long nr_shown; > > > > static unsigned long nr_unshown; > > > > > > > > + /* Don't complain about poisoned pages */ > > > > + if (PageHWPoison(page)) { > > > > + __ClearPageBuddy(page); > > > > + return; > > > > + } > > > > > > Hmm ? why __ClearPageBuddy() is necessary ? > > > > Because this page is considered to be "allocated" out of the buddy > > system, even though we fail the allocation here. > > > > The page is now owned by no one, especially not owned by the buddy > > allocator. > > > I just wonder "why __ClearPageBuddy() is necessary." > > When bad_page() is called, a page is removed from buddy allocator and no > PG_buddy flag at all....I'm sorry if you added bad_page() caller in buddy allocator. You are right. But I didn't add bad_page() callers either :) > Buddy Allocator I call here is just 2 functions. > - __free_one_page() > - expand() Right. Then the original __ClearPageBuddy() call in bad_page() is questionable, I guess this line was there just for the sake of safety (ie. the buddy allocator itself goes wrong): sound-2.6/mm/page_alloc.c @@ -269,7 +269,6 @@ static void bad_page(struct page *page) dump_stack(); out: /* Leave bad fields for debug, except PageBuddy could make trouble */ ===> __ClearPageBuddy(page); add_taint(TAINT_BAD_PAGE); } Thanks, Fengguang -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org