Slightly simplify page queue code.

[markj]

Summary

• Add vm_pagequeue_remove(), which updates page queue state as required when removing a page.
• Get rid of vm_page_pagequeue_lockptr(). When I added it I planned to use it more widely, but it is only used in vm_page_dequeue(). Modify vm_page_pagequeue() to handle a queue index of PQ_NONE, and use it instead. Make it local to vm_page.c; there are no external consumers and page queue management should be limited to vm_page.c and vm_pageout.c.

No functional change intended.

[alc]

sys/vm/vm_page.c

3327

I'm not sure that I see the point of this assignment or the variable pq1, since the very first statement within this loop will replace the value assigned here.

[markj]

• Remove pq1.
• Fix an assertion added in r338276. I meant to assert that either the page lock is held or that vm_page_dequeue() is being called from the page allocator. But testing m->order is not right, we have m->order == VM_NFREEORDER for any allocated page, so the assertion didn't really test anything.

[markj]

Re-add pq1, and reload the page queue pointer only once if a mismatch
is detected after locking the page queue.