mm, vmalloc: iterate vmap_area_list, instead of vmlist, in vmallocinfo()

mm, vmalloc: iterate vmap_area_list, instead of vmlist, in vmallocinfo()

This patch is a preparatory step for removing vmlist entirely.  For above
purpose, we change iterating a vmap_list codes to iterating a
vmap_area_list.  It is somewhat trivial change, but just one thing should
be noticed.

Using vmap_area_list in vmallocinfo() introduce ordering problem in SMP
system.  In s_show(), we retrieve some values from vm_struct.  vm_struct's
values is not fully setup when va->vm is assigned.  Full setup is notified
by removing VM_UNLIST flag without holding a lock.  When we see that
VM_UNLIST is removed, it is not ensured that vm_struct has proper values
in view of other CPUs.  So we need smp_[rw]mb for ensuring that proper
values is assigned when we see that VM_UNLIST is removed.

Therefore, this patch not only change a iteration list, but also add a
appropriate smp_[rw]mb to right places.

Signed-off-by: Joonsoo Kim <js1304@gmail.com>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Dave Anderson <anderson@redhat.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>