Revert "mm: batch activate_page() to reduce lock contention"

Revert "mm: batch activate_page() to reduce lock contention"

This reverts commit 744ed1442757767ffede5008bb13e0805085902e.

Chris Mason ended up chasing down some page allocation errors and pages
stuck waiting on the IO scheduler, and was able to narrow it down to two
commits: commit 744ed1442757 ("mm: batch activate_page() to reduce lock
contention") and d8505dee1a87 ("mm: simplify code of swap.c").

This reverts the first of them.

Reported-and-debugged-by: Chris Mason <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: linux-mm <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Shaohua Li <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>