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

Commit Message

Hugh Dickins June 10, 2021, 6:50 a.m. UTC

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 <[e-mail]>
Cc: <[e-mail]>
---
 mm/page_vma_mapped.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

Comments

Kirill A . Shutemov June 10, 2021, 9:40 a.m. UTC | #1

On Wed, Jun 09, 2021 at 11:50:23PM -0700, Hugh Dickins wrote:
> 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 <[e-mail]>
> Cc: <[e-mail]>

Acked-by: Kirill A. Shutemov <[e-mail]>

Patch

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)