linux-kernel - Re: [PATCH] mm: extend prefault helpers to fault in more than PAGE

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Message-ID: <20120216151425.GB19158@phenom.ffwll.local>
Date:	Thu, 16 Feb 2012 16:14:25 +0100
From:	Daniel Vetter <daniel@...ll.ch>
To:	Hillf Danton <dhillf@...il.com>
Cc:	Daniel Vetter <daniel.vetter@...ll.ch>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
	DRI Development <dri-devel@...ts.freedesktop.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux MM <linux-mm@...ck.org>
Subject: Re: [PATCH] mm: extend prefault helpers to fault in more than
 PAGE_SIZE

On Thu, Feb 16, 2012 at 09:32:08PM +0800, Hillf Danton wrote:
> On Thu, Feb 16, 2012 at 8:01 PM, Daniel Vetter <daniel.vetter@...ll.ch> wrote:
> > @@ -416,17 +417,20 @@ static inline int fault_in_pages_writeable(char __user *uaddr, int size)
> >         * Writing zeroes into userspace here is OK, because we know that if
> >         * the zero gets there, we'll be overwriting it.
> >         */
> > -       ret = __put_user(0, uaddr);
> > +       while (uaddr <= end) {
> > +               ret = __put_user(0, uaddr);
> > +               if (ret != 0)
> > +                       return ret;
> > +               uaddr += PAGE_SIZE;
> > +       }
> 
> What if
>              uaddr & ~PAGE_MASK == PAGE_SIZE -3 &&
>                 end & ~PAGE_MASK == 2

I don't quite follow - can you elaborate upon which issue you're seeing?
-Daniel
-- 
Daniel Vetter
Mail: daniel@...ll.ch
Mobile: +41 (0)79 365 57 48
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