linux-kernel - Re: [PATCH 1/4] mm: add is_highmem

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Date:	Mon, 4 Apr 2016 17:05:58 +0200
From:	Boris Brezillon <boris.brezillon@...e-electrons.com>
To:	Vignesh R <vigneshr@...com>
Cc:	David Woodhouse <dwmw2@...radead.org>,
	Brian Norris <computersforpeace@...il.com>,
	<linux-mtd@...ts.infradead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Gordon <david.s.gordon@...el.com>,
	Mark Brown <broonie@...nel.org>, <linux-spi@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	Vinod Koul <vinod.koul@...el.com>,
	Dan Williams <dan.j.williams@...el.com>,
	<dmaengine@...r.kernel.org>,
	Mauro Carvalho Chehab <m.chehab@...sung.com>,
	Hans Verkuil <hans.verkuil@...co.com>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	<linux-media@...r.kernel.org>, Richard Weinberger <richard@....at>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	"David S. Miller" <davem@...emloft.net>,
	<linux-crypto@...r.kernel.org>, <linux-mm@...ck.org>,
	Joerg Roedel <joro@...tes.org>,
	<iommu@...ts.linux-foundation.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4] mm: add is_highmem_addr() helper

On Mon, 4 Apr 2016 13:44:11 +0530
Vignesh R <vigneshr@...com> wrote:

> Hi,
> 
> On 03/31/2016 05:59 PM, Boris Brezillon wrote:
> > Add an helper to check if a virtual address is in the highmem region.
> > 
> > Signed-off-by: Boris Brezillon <boris.brezillon@...e-electrons.com>
> > ---
> >  include/linux/highmem.h | 13 +++++++++++++
> >  1 file changed, 13 insertions(+)
> > 
> > diff --git a/include/linux/highmem.h b/include/linux/highmem.h
> > index bb3f329..13dff37 100644
> > --- a/include/linux/highmem.h
> > +++ b/include/linux/highmem.h
> > @@ -41,6 +41,14 @@ void kmap_flush_unused(void);
> >  
> >  struct page *kmap_to_page(void *addr);
> >  
> > +static inline bool is_highmem_addr(const void *x)
> > +{
> > +	unsigned long vaddr = (unsigned long)x;
> > +
> > +	return vaddr >=  PKMAP_BASE &&
> > +	       vaddr < ((PKMAP_BASE + LAST_PKMAP) * PAGE_SIZE);
> 
> 
> Shouldn't this be:
> 		vaddr < (PKMAP_BASE + (LAST_PKMAP * PAGE_SIZE)) ?

Oops, yes indeed.

Anyway, given Russell's feedback I don't think I'm gonna follow up on
this series.

Sorry.

Boris

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com