[PATCH v7 4/6] mm: pvmw: add support for walking devmap pages

[Muchun Song]

The devmap pages can not use page_vma_mapped_walk() to check if a huge
devmap page is mapped into a vma.  Add support for walking huge devmap
pages so that DAX can use it in the next patch.

Signed-off-by: Muchun Song <songmuc...@bytedance.com>
---
 mm/page_vma_mapped.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index 1187f9c1ec5b..3da82bf65de8 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -210,16 +210,10 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk 
*pvmw)
                 */
                pmde = READ_ONCE(*pvmw->pmd);
 
-               if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde)) {
+               if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde) ||
+                   (pmd_present(pmde) && pmd_devmap(pmde))) {
                        pvmw->ptl = pmd_lock(mm, pvmw->pmd);
                        pmde = *pvmw->pmd;
-                       if (likely(pmd_trans_huge(pmde))) {
-                               if (pvmw->flags & PVMW_MIGRATION)
-                                       return not_found(pvmw);
-                               if (!check_pmd(pmd_pfn(pmde), pvmw))
-                                       return not_found(pvmw);
-                               return true;
-                       }
                        if (!pmd_present(pmde)) {
                                swp_entry_t entry;
 
@@ -232,6 +226,13 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk 
*pvmw)
                                        return not_found(pvmw);
                                return true;
                        }
+                       if (likely(pmd_trans_huge(pmde) || pmd_devmap(pmde))) {
+                               if (pvmw->flags & PVMW_MIGRATION)
+                                       return not_found(pvmw);
+                               if (!check_pmd(pmd_pfn(pmde), pvmw))
+                                       return not_found(pvmw);
+                               return true;
+                       }
                        /* THP pmd was split under us: handle on pte level */
                        spin_unlock(pvmw->ptl);
                        pvmw->ptl = NULL;
-- 
2.11.0