[PATCH V3 2/2] ARM: Handle user space mapped pages in flush_kernel_dcache_page

[Ming Lei]

On Fri, May 3, 2013 at 6:02 PM, Catalin Marinas <catalin.marinas at arm.com> wrote:
>>
>> I assume that you inhibited the call to flush_dcache_page() in
>> __get_user_pages() for anon pages.  Otherwise, you will be flooded
>> with warnings.
>
> I haven't done any stress testing so I don't think I hit this code path,
> so no warning. But yes, it should have triggered. Anyway, in this case
> flush_dcache_page() should have just ignored (clearing PG_arch_1 is
> harmless anyway if we also ignore this bit in __sync_icache_dcache for
> non-aliasing caches).

Yes, maybe we can do a little optimization for O_DIRECT since no
dcache alias and I/D coherency problem in this case on ARMv7, how
about below change?

diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c
index 1c8f7f5..962a657 100644
--- a/arch/arm/mm/flush.c
+++ b/arch/arm/mm/flush.c
@@ -287,6 +287,8 @@ void flush_dcache_page(struct page *page)
 	    mapping && !mapping_mapped(mapping))
 		clear_bit(PG_dcache_clean, &page->flags);
 	else {
+		if (!mapping && cache_is_vipt_nonaliasing())
+			return;
 		__flush_dcache_page(mapping, page);
 		if (mapping && cache_is_vivt())
 			__flush_dcache_aliases(mapping, page);

Thanks,
-- 
Ming Lei