(2012/07/05 9:45), Johannes Weiner wrote:

shmem knows for sure that the page is in swap cache when attempting to
charge a page, because the cache charge entry function has a check for
it.  Only anon pages may be removed from swap cache already when
trying to charge their swapin.

Adjust the comment, though: '4969c11 mm: fix swapin race condition'
added a stable PageSwapCache check under the page lock in the
do_swap_page() before calling the memory controller, so it's
unuse_pte()'s pte_same() that may fail.

Signed-off-by: Johannes Weiner <redacted>

Acked-by: KAMEZAWA Hiroyuki <redacted>