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).
The lack of a '__GFP_HIGHMEM' flag should mean these are
lowmem pages (?).
The (compound) pages in question would have already
been mmap()-ed by the user.
Doug Gilbert
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