linux-kernel - Re: [PATCH] mm: hugetlb: flush dcache before returning zeroed huge page to userspace

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Date:	Thu, 16 Aug 2012 19:32:56 +0100
From:	Will Deacon <will.deacon@....com>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	Hugh Dickins <hughd@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Hillf Danton <dhillf@...il.com>,
	Russell King <linux@....linux.org.uk>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH] mm: hugetlb: flush dcache before returning zeroed huge
 page to userspace

On Thu, Aug 16, 2012 at 07:20:15PM +0100, Michal Hocko wrote:
> On Thu 16-08-12 17:09:54, Will Deacon wrote:
> > +static inline void arch_clear_hugepage_flags(struct page *page)
> > +{
> > +	flush_dcache_page(page);
> > +}
> > +
> 
> Why do we need the hook for ia64? hugetlb_no_page calls clear_huge_page
> and that one calls flush_dcache_page (via clear_user_page), right?
> The same applies to copy_huge_page for COW.

You're right, these are redundant for ppc and ia64 (although ppc does have a
comment moaning about the flush). Looks like it's just sh and ARM that need to
do anything.

Cheers,

Will
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