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

From: [email-masked] (Russell King - ARM Linux)
Date: Mon, 7 Nov 2016 11:48:45 +0000

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.)

As this path gets used for filesystem read/write, it would be a
good idea to keep it as efficient as possible.

-- 
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