From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with ESMTP id 2D027900086 for ; Thu, 14 Apr 2011 17:55:57 -0400 (EDT) Date: Thu, 14 Apr 2011 14:54:58 -0700 From: Andrew Morton Subject: Re: [patch] mm: fail GFP_DMA allocations when ZONE_DMA is not configured Message-Id: <20110414145458.f9bb7744.akpm@linux-foundation.org> In-Reply-To: References: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: Mel Gorman , KOSAKI Motohiro , KAMEZAWA Hiroyuki , Rik van Riel , linux-mm@kvack.org On Thu, 14 Apr 2011 14:46:56 -0700 (PDT) David Rientjes wrote: > The page allocator will improperly return a page from ZONE_NORMAL even > when __GFP_DMA is passed if CONFIG_ZONE_DMA is disabled. The caller > expects DMA memory, perhaps for ISA devices with 16-bit address > registers, and may get higher memory resulting in undefined behavior. > > This patch causes the page allocator to return NULL in such circumstances > with a warning emitted to the kernel log on the first occurrence. > > Signed-off-by: David Rientjes > --- > mm/page_alloc.c | 4 ++++ > 1 files changed, 4 insertions(+), 0 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -2225,6 +2225,10 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, > > if (should_fail_alloc_page(gfp_mask, order)) > return NULL; > +#ifndef CONFIG_ZONE_DMA > + if (WARN_ON_ONCE(gfp_mask & __GFP_DMA)) > + return NULL; > +#endif Worried. We have a large number of drivers which use GFP_DMA and I bet some of them didn't really need to set it, and can use DMA32 memory. They will now break. What is drivers/pci/intel-iommu.c doing with GFP_DMA btw? How commonly are people disabling ZONE_DMA? -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org