On 12/19/2016 03:07 PM, Linus Torvalds wrote:
> +wait_queue_head_t *bit_waitqueue(void *word, int bit)
> +{
> + const int __maybe_unused nid = page_to_nid(virt_to_page(word));
> +
> + return __bit_waitqueue(word, bit, nid);
>
> No can do. Part of the problem with the old coffee was that it did that
> virt_to_page() crud. That doesn't work with the virtually mapped stack.
Ahhh, got it.
So, what did you have in mind? Just redirect bit_waitqueue() to the
"first_online_node" waitqueues?
wait_queue_head_t *bit_waitqueue(void *word, int bit)
{
return __bit_waitqueue(word, bit, first_online_node);
}
We could do some fancy stuff like only do virt_to_page() for things in
the linear map, but I'm not sure we'll see much of a gain for it. None
of the other waitqueue users look as pathological as the 'struct page'
ones. Maybe:
wait_queue_head_t *bit_waitqueue(void *word, int bit)
{
int nid
if (word >= VMALLOC_START) /* all addrs not in linear map */
nid = first_online_node;
else
nid = page_to_nid(virt_to_page(word));
return __bit_waitqueue(word, bit, nid);
}
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