On Wed, Jan 18, 2006 at 07:59:37PM -0800, Andrew Morton wrote:
> Nick Piggin <npiggin@xxxxxxx> wrote:
> > - /* N.B. correction _not_ applied to base page of each allocation */
> > - for (k = 0; k < rsv_schp->k_use_sg; ++k, ++sg) {
> > - for (m = PAGE_SIZE; m < sg->length; m += PAGE_SIZE) {
> > - page = sg->page;
> > - if (startFinish)
> > - get_page(page);
> > - else {
> > - if (page_count(page) > 0)
> > - __put_page(page);
> > - }
> > - }
> > - }
> > -}
>
> What on earth is the above trying to do? The inner loop is a rather
> complex way of doing atomic_add(&page->count, sg->length/PAGE_SIZE). One
> suspects there's a missing "[m]" in there.
>
It does this on the first mmap of the device, in the hope that subsequent
nopage, unmaps would not free the constituent pages in the scatterlist.
> Yes, using a compound page for the refcounting sounds sane, but I think
> this code is fragile and has monsters in it.
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