mm: hugetlb: proc: add hugetlb-related fields to /proc/PID/smaps

Currently /proc/PID/smaps provides no usage info for vma(VM_HUGETLB),
which is inconvenient when we want to know per-task or per-vma base
hugetlb usage.  To solve this, this patch adds new fields for hugetlb
usage like below:

  Size:              20480 kB
  Rss:                   0 kB
  Pss:                   0 kB
  Shared_Clean:          0 kB
  Shared_Dirty:          0 kB
  Private_Clean:         0 kB
  Private_Dirty:         0 kB
  Referenced:            0 kB
  Anonymous:             0 kB
  AnonHugePages:         0 kB
  Shared_Hugetlb:    18432 kB
  Private_Hugetlb:    2048 kB
  Swap:                  0 kB
  KernelPageSize:     2048 kB
  MMUPageSize:        2048 kB
  Locked:                0 kB
  VmFlags: rd wr mr mw me de ht

[hughd@google.com: fix Private_Hugetlb alignment ]
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Joern Engel <joern@logfs.org>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/filesystems/proc.txt

@@ -424,6 +424,9 @@ Private_Clean:         0 kB
 Private_Dirty:         0 kB
 Referenced:          892 kB
 Anonymous:             0 kB
+AnonHugePages:         0 kB
+Shared_Hugetlb:        0 kB
+Private_Hugetlb:       0 kB
 Swap:                  0 kB
 SwapPss:               0 kB
 KernelPageSize:        4 kB
@@ -452,6 +455,11 @@ and a page is modified, the file page is replaced by a private anonymous copy.
 "Swap" shows how much would-be-anonymous memory is also used, but out on
 swap.
 "SwapPss" shows proportional swap share of this mapping.
+"AnonHugePages" shows the ammount of memory backed by transparent hugepage.
+"Shared_Hugetlb" and "Private_Hugetlb" show the ammounts of memory backed by
+hugetlbfs page which is *not* counted in "RSS" or "PSS" field for historical
+reasons. And these are not included in {Shared,Private}_{Clean,Dirty} field.
+
 "VmFlags" field deserves a separate description. This member represents the kernel
 flags associated with the particular virtual memory area in two letter encoded
 manner. The codes are the following: