mm: account pud page tables

On a machine with 5-level paging support a process can allocate
significant amount of memory and stay unnoticed by oom-killer and memory
cgroup.  The trick is to allocate a lot of PUD page tables.  We don't
account PUD page tables, only PMD and PTE.

We already addressed the same issue for PMD page tables, see commit
dc6c9a35b66b ("mm: account pmd page tables to the process").
Introduction of 5-level paging brings the same issue for PUD page
tables.

The patch expands accounting to PUD level.

[kirill.shutemov@linux.intel.com: s/pmd_t/pud_t/]
  Link: http://lkml.kernel.org/r/20171004074305.x35eh5u7ybbt5kar@black.fi.intel.com
[heiko.carstens@de.ibm.com: s390/mm: fix pud table accounting]
  Link: http://lkml.kernel.org/r/20171103090551.18231-1-heiko.carstens@de.ibm.com
Link: http://lkml.kernel.org/r/20171002080427.3320-1-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index 07cc743698d3..a4eb6f289365 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -819,6 +819,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
         mm->core_state = NULL;
         atomic_long_set(&mm->nr_ptes, 0);
         mm_nr_pmds_init(mm);
+        mm_nr_puds_init(mm);
         mm->map_count = 0;
         mm->locked_vm = 0;
         mm->pinned_vm = 0;
@@ -878,6 +879,9 @@ static void check_mm(struct mm_struct *mm)
         if (mm_nr_pmds(mm))
                 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n",
                                 mm_nr_pmds(mm));
+        if (mm_nr_puds(mm))
+                pr_alert("BUG: non-zero nr_puds on freeing mm: %ld\n",
+                                mm_nr_puds(mm));
 
 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
         VM_BUG_ON_MM(mm->pmd_huge_pte, mm);