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    SubjectRe: [PATCH] mm: extend prefault helpers to fault in more than PAGE_SIZE
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    On Thu, Mar 1, 2012 at 20:22, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
    > +/* Multipage variants of the above prefault helpers, useful if more than
    > + * PAGE_SIZE of date needs to be prefaulted. These are separate from the above
    > + * functions (which only handle up to PAGE_SIZE) to avoid clobbering the
    > + * filemap.c hotpaths. */
    > +static inline int fault_in_multipages_writeable(char __user *uaddr, int size)
    > +{
    > +       int ret;
    > +       const char __user *end = uaddr + size - 1;

    Please drop the const.

    > +
    > +       if (unlikely(size == 0))
    > +               return 0;
    > +
    > +       /*
    > +        * Writing zeroes into userspace here is OK, because we know that if
    > +        * the zero gets there, we'll be overwriting it.
    > +        */
    > +       while (uaddr <= end) {
    > +               ret = __put_user(0, uaddr);
    > +               if (ret != 0)
    > +                       return ret;
    > +               uaddr += PAGE_SIZE;
    > +       }
    > +
    > +       /* Check whether the range spilled into the next page. */
    > +       if (((unsigned long)uaddr & PAGE_MASK) ==
    > +                       ((unsigned long)end & PAGE_MASK))
    > +               ret = __put_user(0, end);

    include/linux/pagemap.h:483:3: error: read-only location '*end' used
    as 'asm' output

    Now in -next:

    http://kisskb.ellerman.id.au/kisskb/buildresult/6100650/
    http://kisskb.ellerman.id.au/kisskb/buildresult/6100673/
    http://kisskb.ellerman.id.au/kisskb/buildresult/6100860/

    Gr{oetje,eeting}s,

                            Geert

    --
    Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

    In personal conversations with technical people, I call myself a hacker. But
    when I'm talking to journalists I just say "programmer" or something like that.
                                    -- Linus Torvalds
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