teach /proc/$pid/numa_maps about transparent hugepages

This is modeled after the smaps code.

It detects transparent hugepages and then does a single gather_stats()
for the page as a whole.  This has two benifits:
 1. It is more efficient since it does many pages in a single shot.
 2. It does not have to break down the huge page.

Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
Acked-by: Hugh Dickins <hughd@google.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 20 insertions, 0 deletions

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 9dca07e0758d..5afaa58a8630 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -936,6 +936,26 @@ static int gather_pte_stats(pmd_t *pmd, unsigned long addr,
         pte_t *pte;
 
         md = walk->private;
+        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(md->vma->anon_vma, pmd);
+                } else {
+                        pte_t huge_pte = *(pte_t *)pmd;
+                        struct page *page;
+
+                        page = can_gather_numa_stats(huge_pte, md->vma, addr);
+                        if (page)
+                                gather_stats(page, md, pte_dirty(huge_pte),
+                                                HPAGE_PMD_SIZE/PAGE_SIZE);
+                        spin_unlock(&walk->mm->page_table_lock);
+                        return 0;
+                }
+        } else {
+                spin_unlock(&walk->mm->page_table_lock);
+        }
+
         orig_pte = pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
         do {
                 struct page *page = can_gather_numa_stats(*pte, md->vma, addr);