mm/memcontrol.c: make the walk_page_range() limit obvious

mem_cgroup_count_precharge() and mem_cgroup_move_charge() both call
walk_page_range() on the range 0 to ~0UL, neither provide a pte_hole
callback, which causes the current implementation to skip non-vma
regions.  This is all fine but follow up changes would like to make
walk_page_range more generic so it is better to be explicit about which
range to traverse so let's use highest_vm_end to explicitly traverse
only user mmaped memory.

[mhocko@kernel.org: rewrote changelog]
Link: http://lkml.kernel.org/r/1472655897-22532-1-git-send-email-james.morse@arm.com
Signed-off-by: James Morse <james.morse@arm.com>
Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index bdb796fd85f40962616478fdf944f0e6768b14e7..d150f70dc1991731be5adc7d7134bc03d5760eaf 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4668,7 +4668,8 @@ static unsigned long mem_cgroup_count_precharge(struct mm_struct *mm)
                .mm = mm,
        };
        down_read(&mm->mmap_sem);
-       walk_page_range(0, ~0UL, &mem_cgroup_count_precharge_walk);
+       walk_page_range(0, mm->highest_vm_end,
+                       &mem_cgroup_count_precharge_walk);
        up_read(&mm->mmap_sem);
 
        precharge = mc.precharge;
@@ -4956,7 +4957,8 @@ retry:
         * When we have consumed all precharges and failed in doing
         * additional charge, the page walk just aborts.
         */
-       walk_page_range(0, ~0UL, &mem_cgroup_move_charge_walk);
+       walk_page_range(0, mc.mm->highest_vm_end, &mem_cgroup_move_charge_walk);
+
        up_read(&mc.mm->mmap_sem);
        atomic_dec(&mc.from->moving_account);
 }