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[v13,12/22] mm: pagewalk: Allow walking without vma

Message ID 20191024093716.49420-13-steven.price@arm.com
State New, archived
Headers show
Series Generic page walk and ptdump | expand

Commit Message

Steven Price Oct. 24, 2019, 9:37 a.m. UTC
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.price@arm.com>
---
 mm/pagewalk.c | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

Comments

Steven Price Oct. 28, 2019, 10:46 a.m. UTC | #1
On 27/10/2019 07:59, kbuild test robot wrote:
> Hi Steven,
> 
> Thank you for the patch! Yet something to improve:
> 
> [auto build test ERROR on linus/master]
> [also build test ERROR on v5.4-rc4 next-20191025]
> [if your patch is applied to the wrong git tree, please drop us a note to help
> improve the system. BTW, we also suggest to use '--base' option to specify the
> base tree in git format-patch, please see https://stackoverflow.com/a/37406982]
> 
> url:    https://github.com/0day-ci/linux/commits/Steven-Price/Generic-page-walk-and-ptdump/20191027-140322
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 5a1e843c66fa6438f389045981c37e4073917641
> config: arc-defconfig (attached as .config)
> compiler: arc-elf-gcc (GCC) 7.4.0
> reproduce:
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # save the attached .config to linux build tree
>         GCC_VERSION=7.4.0 make.cross ARCH=arc 

First off, these instructions don't work! make.cross attempts to
download a sparc toolchain.

However, the issue is actually quite easy to see if you look more
closely at patch 2:

> +#define pmd_leaf(x)                    (pmd_val(pmd) & _PAGE_HW_SZ)

That 'pmd' variable should really have been 'x'!

Below diff should fix this up - I'll repost with this squashed in shortly:

----8<----
diff --git a/arch/arc/include/asm/pgtable.h b/arch/arc/include/asm/pgtable.h
index 5ec798e50836..b4a0cf27ac1c 100644
--- a/arch/arc/include/asm/pgtable.h
+++ b/arch/arc/include/asm/pgtable.h
@@ -274,7 +274,7 @@ static inline void pmd_set(pmd_t *pmdp, pte_t *ptep)
 #define pmd_none(x)                    (!pmd_val(x))
 #define        pmd_bad(x)                      ((pmd_val(x) & ~PAGE_MASK))
 #define pmd_present(x)                 (pmd_val(x))
-#define pmd_leaf(x)                    (pmd_val(pmd) & _PAGE_HW_SZ)
+#define pmd_leaf(x)                    (pmd_val(x) & _PAGE_HW_SZ)
 #define pmd_clear(xp)                  do { pmd_val(*(xp)) = 0; } while (0)

 #define pte_page(pte)          pfn_to_page(pte_pfn(pte))
diff mbox series

Patch

diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index fc4d98a3a5a0..4139e9163aee 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -38,7 +38,7 @@  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 (ops->pte_hole)
 				err = ops->pte_hole(addr, next, walk);
 			if (err)
@@ -61,9 +61,14 @@  static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
 		if (!ops->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;
@@ -84,7 +89,7 @@  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 (ops->pte_hole)
 				err = ops->pte_hole(addr, next, walk);
 			if (err)
@@ -98,9 +103,13 @@  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 (ops->pmd_entry || ops->pte_entry)
 			err = walk_pmd_range(pud, addr, next, walk);