[PATCH] Add /proc/PID/{smaps, numa_maps} support for DAX

[Fan Du]

So user could check those interface for more detailed
information about how much DAX mappings are currently
created.

Here we use vma_is_dax method to find specific page
struture with DAX {huge, normal}page mappings,
vm_normal_page routine works as before without any
impact on the existing logical where _vm_normal_page
are called.

Signed-off-by: Fan Du <fan...@intel.com>
---
 fs/proc/task_mmu.c | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 5589b4b..ba2e58c 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -528,7 +528,11 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,
        struct page *page = NULL;
 
        if (pte_present(*pte)) {
-               page = vm_normal_page(vma, addr, *pte);
+               if (!vma_is_dax(vma))
+                       page = vm_normal_page(vma, addr, *pte);
+               else
+                       page = pte_page(*pte);
+
        } else if (is_swap_pte(*pte)) {
                swp_entry_t swpent = pte_to_swp_entry(*pte);
 
@@ -579,7 +583,11 @@ static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,
        struct page *page;
 
        /* FOLL_DUMP will return -EFAULT on huge zero page */
-       page = follow_trans_huge_pmd(vma, addr, pmd, FOLL_DUMP);
+       if (!vma_is_dax(vma))
+               page = follow_trans_huge_pmd(vma, addr, pmd, FOLL_DUMP);
+       else
+               page = pmd_page(*pmd);
+
        if (IS_ERR_OR_NULL(page))
                return;
        if (PageAnon(page))
@@ -1668,13 +1676,15 @@ static int gather_pte_stats(pmd_t *pmd, unsigned long 
addr,
        spinlock_t *ptl;
        pte_t *orig_pte;
        pte_t *pte;
+       struct page *page;
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
        ptl = pmd_trans_huge_lock(pmd, vma);
        if (ptl) {
-               struct page *page;
-
-               page = can_gather_numa_stats_pmd(*pmd, vma, addr);
+               if (!vma_is_dax(vma))
+                       page = can_gather_numa_stats_pmd(*pmd, vma, addr);
+               else
+                       page = pmd_page(*pmd);
                if (page)
                        gather_stats(page, md, pmd_dirty(*pmd),
                                     HPAGE_PMD_SIZE/PAGE_SIZE);
@@ -1687,7 +1697,10 @@ static int gather_pte_stats(pmd_t *pmd, unsigned long 
addr,
 #endif
        orig_pte = pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
        do {
-               struct page *page = can_gather_numa_stats(*pte, vma, addr);
+               if (!vma_is_dax(vma))
+                       page = can_gather_numa_stats(*pte, vma, addr);
+               else
+                       page = pte_page(*pte);
                if (!page)
                        continue;
                gather_stats(page, md, pte_dirty(*pte), 1);
-- 
1.8.3.1