On Thu, 14 Apr 2011 14:46:56 -0700 (PDT) David Rientjes <rientjes@xxxxxxxxxx> 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 <rientjes@xxxxxxxxxx> > --- > 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@xxxxxxxxxx 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: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>