smaps: teach smaps_pte_range() about THP pmds

This adds code to explicitly detect and handle pmd_trans_huge() pmds.  It
then passes HPAGE_SIZE units in to the smap_pte_entry() function instead
of PAGE_SIZE.

This means that using /proc/$pid/smaps now will no longer cause THPs to be
broken down in to small pages.

Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
Reviewed-by: Eric B Munson <emunson@mgebm.net>
Tested-by: Eric B Munson <emunson@mgebm.net>
Acked-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Michael J Wolf <mjwolf@us.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 21 insertions, 2 deletions

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index d7e2af334076..26f9cc00102c 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1,5 +1,6 @@
 #include <linux/mm.h>
 #include <linux/hugetlb.h>
+#include <linux/huge_mm.h>
 #include <linux/mount.h>
 #include <linux/seq_file.h>
 #include <linux/highmem.h>
@@ -7,6 +8,7 @@
 #include <linux/slab.h>
 #include <linux/pagemap.h>
 #include <linux/mempolicy.h>
+#include <linux/rmap.h>
 #include <linux/swap.h>
 #include <linux/swapops.h>
 
@@ -385,8 +387,25 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
         pte_t *pte;
         spinlock_t *ptl;
 
-        split_huge_page_pmd(walk->mm, pmd);
-
+        spin_lock(&walk->mm->page_table_lock);
+        if (pmd_trans_huge(*pmd)) {
+                if (pmd_trans_splitting(*pmd)) {
+                        spin_unlock(&walk->mm->page_table_lock);
+                        wait_split_huge_page(vma->anon_vma, pmd);
+                } else {
+                        smaps_pte_entry(*(pte_t *)pmd, addr,
+                                        HPAGE_PMD_SIZE, walk);
+                        spin_unlock(&walk->mm->page_table_lock);
+                        return 0;
+                }
+        } else {
+                spin_unlock(&walk->mm->page_table_lock);
+        }
+        /*
+         * The mmap_sem held all the way back in m_start() is what
+         * keeps khugepaged out of here and from collapsing things
+         * in here.
+         */
         pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
         for (; addr != end; pte++, addr += PAGE_SIZE)
                 smaps_pte_entry(*pte, addr, PAGE_SIZE, walk);