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

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Date:	Thu, 16 Feb 2012 21:32:08 +0800
From:	Hillf Danton <dhillf@...il.com>
To:	Daniel Vetter <daniel.vetter@...ll.ch>
Cc:	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 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
--
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