Just got two oopses from 2.1.82. The first occurred at pagemap.h:76
(remove_page_from_hash_queue):
if(page->next_hash)
page->next_hash->pprev_hash = page->pprev_hash;
Problem is, page->next_hash is 0x800. kswapd then became a zombie!
If it's any help, page->count is 1, and page->inode is non-zero (and not
&swapper_inode) [just following the code sequence in shrink_mmap].
Tim.
*/