mm/page_owner: initialize page owner without holding the zone lock

It's not necessary to initialized page_owner with holding the zone lock.
It would cause more contention on the zone lock although it's not a big
problem since it is just debug feature.  But, it is better than before
so do it.  This is also preparation step to use stackdepot in page owner
feature.  Stackdepot allocates new pages when there is no reserved space
and holding the zone lock in this case will cause deadlock.

Change-Id: Id96ab8444f194bead3fa4a8ddda30cdcca4ddc9f
Link: http://lkml.kernel.org/r/1464230275-25791-2-git-send-email-iamjoonsoo.kim@lge.com


Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Alexander Potapenko <glider@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Git-commit: 83358ece26b70f20c0ba2e0e00dc84b0ee24fe6d
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


[guptap@codeaurora.org: resolve trivial merge conflicts]
Signed-off-by: Prakash Gupta <guptap@codeaurora.org>