mm: vmscan: stall page reclaim after a list of pages have been processed

Commit "mm: vmscan: Block kswapd if it is encountering pages under
writeback" blocks page reclaim if it encounters pages under writeback
marked for immediate reclaim.  It blocks while pages are still isolated
from the LRU which is unnecessary.  This patch defers the blocking until
after the isolated pages have been processed and tidies up some of the
comments.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Rik van Riel <riel@redhat.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
Cc: Zlatko Calusic <zcalusic@bitsync.net>
Cc: dormando <dormando@rydia.net>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Git-commit: b1a6f21e3b2315d46ae8af88a8f4eb8ea2763107
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Change-Id: Ia6da0949d7bf81cd7c8d3951a7f9c723131b9037
Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>