On Sat, 19 Aug 2006 13:36:33 -0400
Douglas Gilbert <dougg@xxxxxxxxxx> wrote:
> Matthew Wilcox wrote:
> > On Sat, Aug 19, 2006 at 12:11:34AM -0400, Douglas Gilbert wrote:
> >>> Your point about the change to sg_vma_nopage() between
> >>> lk 2.6.15 and lk 2.6.16 also seems to be correct.
> >>> The most indented part of that function has been
> >>> changed from incrementing the change count on the
> >>> reported page (as indicated by 'offset') in a
> >>> compound page allocation to ignoring the 'offset'
> >>> and incrementing the page count on the first page
> >>> in a compound page allocation.
> >> if (offset < len) {
> >> - page = sg->page;
> >> + page = virt_to_page(page_address(sg->page) + offset);
> >> get_page(page); /* increment page count */
> >
> > But page_address can return NULL on highmem machines. Or are you
> > guaranteed that these are lowmem pages?
>
> Matthew,
> The allocation is typically compound done with:
> alloc_pages(GFP_ATOMIC|__GFP_COMP|__GFP_NOWARN, order)
> where 'order' is 3 (hence 32 KB).
ow, GFP_ATOMIC is bad. Can we avoid that?
> The lack of a '__GFP_HIGHMEM' flag should mean these are
> lowmem pages (?).
Yup.
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