[PATCH 09/11] mm: page_vma_mapped_walk(): get vma_address_end() earlier

Hugh Dickins
2021-06-10T06:50:28Z

page_vma_mapped_walk() cleanup: get THP's vma_address_end() at the start,
rather than later at next_pte. It's a little unnecessary overhead on the
first call, but makes for a simpler loop in the following commit.

Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: <stable@vger.kernel.org>
---
mm/page_vma_mapped.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index 006f4814abbc..f6839f536645 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -171,6 +171,15 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
return true;
}

+ /*
+ * Seek to next pte only makes sense for THP.
+ * But more important than that optimization, is to filter out
+ * any PageKsm page: whose page->index misleads vma_address()
+ * and vma_address_end() to disaster.
+ */
+ end = PageTransCompound(page) ?
+ vma_address_end(page, pvmw->vma) :
+ pvmw->address + PAGE_SIZE;
if (pvmw->pte)
goto next_pte;
restart:
@@ -239,10 +248,6 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
if (check_pte(pvmw))
return true;
next_pte:
- /* Seek to next pte only makes sense for THP */
- if (!PageTransHuge(page))
- return not_found(pvmw);
- end = vma_address_end(page, pvmw->vma);
do {
pvmw->address += PAGE_SIZE;
if (pvmw->address >= end)
--
2.26.2