diff mbox series

[06/11] mm: page_vma_mapped_walk(): crossing page table boundary

Message ID 799b3f9c-2a9e-dfef-5d89-26e9f76fd97@google.com (mailing list archive)
State New
Headers show
Series mm: page_vma_mapped_walk() cleanup and THP fixes | expand

Commit Message

Hugh Dickins June 10, 2021, 6:44 a.m. UTC
page_vma_mapped_walk() cleanup: adjust the test for crossing page table
boundary - I believe pvmw->address is always page-aligned, but nothing
else here assumed that; and remember to reset pvmw->pte to NULL after
unmapping the page table, though I never saw any bug from that.

Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: <stable@vger.kernel.org>
---
 mm/page_vma_mapped.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

Comments

Kirill A. Shutemov June 10, 2021, 9:32 a.m. UTC | #1
On Wed, Jun 09, 2021 at 11:44:10PM -0700, Hugh Dickins wrote:
> page_vma_mapped_walk() cleanup: adjust the test for crossing page table
> boundary - I believe pvmw->address is always page-aligned, but nothing
> else here assumed that;

Maybe we should just get it aligned instead? (PMD_SIZE - PAGE_SIZE) is not
most obvious mask calculation.

> and remember to reset pvmw->pte to NULL after
> unmapping the page table, though I never saw any bug from that.

Okay, it's fair enough.
diff mbox series

Patch

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index b96fae568bc2..0fe6e558d336 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -247,16 +247,16 @@  bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
 			if (pvmw->address >= end)
 				return not_found(pvmw);
 			/* Did we cross page table boundary? */
-			if (pvmw->address % PMD_SIZE == 0) {
-				pte_unmap(pvmw->pte);
+			if ((pvmw->address & (PMD_SIZE - PAGE_SIZE)) == 0) {
 				if (pvmw->ptl) {
 					spin_unlock(pvmw->ptl);
 					pvmw->ptl = NULL;
 				}
+				pte_unmap(pvmw->pte);
+				pvmw->pte = NULL;
 				goto restart;
-			} else {
-				pvmw->pte++;
 			}
+			pvmw->pte++;
 		} while (pte_none(*pvmw->pte));
 
 		if (!pvmw->ptl) {