[RFC] mm:change /proc/smaps caculation behavior

["Wang, Yalin" <Yalin.Wang@sonymobile.com>]

This patch change smaps pagetable walk behavior, to make
sure not skip VM_PFNMAP pagetables,
so that we can calculate COW pages of VM_PFNMAP as normal pages.

Signed-off-by: Yalin Wang <yalin.wang@sonymobile.com>
---
 fs/proc/task_mmu.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index c7267e9..00a5b73 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -503,6 +503,15 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,
 	smaps_account(mss, page, PAGE_SIZE, pte_young(*pte), pte_dirty(*pte));
 }
 
+static int smaps_test_walk(unsigned long addr, unsigned long next,
+		struct mm_walk *walk)
+{
+	/*
+	 * don't skip VM_PFNMAP, so that we can caculate some COW pages.
+	 */
+	return 0;
+}
+
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,
 		struct mm_walk *walk)
@@ -616,6 +625,7 @@ static int show_smap(struct seq_file *m, void *v, int is_pid)
 	struct mem_size_stats mss;
 	struct mm_walk smaps_walk = {
 		.pmd_entry = smaps_pte_range,
+		.test_walk = smaps_test_walk,
 		.mm = vma->vm_mm,
 		.private = &mss,
 	};
-- 
2.2.2