[PATCH v10 12/22] mm: pagewalk: Allow walking without vma

[Steven Price]

Since 48684a65b4e3: "mm: pagewalk: fix misbehavior of walk_page_range
for vma(VM_PFNMAP)", page_table_walk() will report any kernel area as
a hole, because it lacks a vma.

This means each arch has re-implemented page table walking when needed,
for example in the per-arch ptdump walker.

Remove the requirement to have a vma except when trying to split huge
pages.

Signed-off-by: Steven Price <steven.pr...@arm.com>
---
 mm/pagewalk.c | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index 98373a9f88b8..1cbef99e9258 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -36,7 +36,7 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, 
unsigned long end,
        do {
 again:
                next = pmd_addr_end(addr, end);
-               if (pmd_none(*pmd) || !walk->vma) {
+               if (pmd_none(*pmd)) {
                        if (walk->pte_hole)
                                err = walk->pte_hole(addr, next, walk);
                        if (err)
@@ -59,9 +59,14 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, 
unsigned long end,
                if (!walk->pte_entry)
                        continue;
 
-               split_huge_pmd(walk->vma, pmd, addr);
-               if (pmd_trans_unstable(pmd))
-                       goto again;
+               if (walk->vma) {
+                       split_huge_pmd(walk->vma, pmd, addr);
+                       if (pmd_trans_unstable(pmd))
+                               goto again;
+               } else if (pmd_leaf(*pmd)) {
+                       continue;
+               }
+
                err = walk_pte_range(pmd, addr, next, walk);
                if (err)
                        break;
@@ -81,7 +86,7 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, 
unsigned long end,
        do {
  again:
                next = pud_addr_end(addr, end);
-               if (pud_none(*pud) || !walk->vma) {
+               if (pud_none(*pud)) {
                        if (walk->pte_hole)
                                err = walk->pte_hole(addr, next, walk);
                        if (err)
@@ -95,9 +100,13 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, 
unsigned long end,
                                break;
                }
 
-               split_huge_pud(walk->vma, pud, addr);
-               if (pud_none(*pud))
-                       goto again;
+               if (walk->vma) {
+                       split_huge_pud(walk->vma, pud, addr);
+                       if (pud_none(*pud))
+                               goto again;
+               } else if (pud_leaf(*pud)) {
+                       continue;
+               }
 
                if (walk->pmd_entry || walk->pte_entry)
                        err = walk_pmd_range(pud, addr, next, walk);
-- 
2.20.1