[PATCH] ARM: avoid cache flushing in flush_dcache_page()

[Catalin Marinas]

On Mon, Nov 07, 2016 at 11:48:45AM +0000, Russell King - ARM Linux wrote:
> On Mon, Nov 07, 2016 at 11:35:27AM +0000, Catalin Marinas wrote:
> > On Mon, Nov 07, 2016 at 11:30:24AM +0100, Rabin Vincent wrote:
> > > diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c
> > > index 3cced84..f1e6190 100644
> > > --- a/arch/arm/mm/flush.c
> > > +++ b/arch/arm/mm/flush.c
> > > @@ -327,6 +327,12 @@ void flush_dcache_page(struct page *page)
> > >  	if (page == ZERO_PAGE(0))
> > >  		return;
> > >  
> > > +	if (!cache_ops_need_broadcast() && cache_is_vipt_nonaliasing()) {
> > > +		if (test_bit(PG_dcache_clean, &page->flags))
> > > +			clear_bit(PG_dcache_clean, &page->flags);
> > > +		return;
> > > +	}
> > > +
> > >  	mapping = page_mapping(page);
> > >  
> > >  	if (!cache_ops_need_broadcast() &&
> > 
> > I'm ok with the logic in this patch but is there a way to combine the
> > two 'if' blocks together, just to keep the function shorter?
> 
> Probably not without reducing code readability, or moving
> page_mapping() before this new if() block (which may introduce
> extra code into the path.)

You are right, we would need 'mapping' in the subsequent checks, so I
don't think the code would be more readable if we are to keep it
efficient. In this case:

Reviewed-by: Catalin Marinas <catalin.marinas at arm.com>