[PATCH 5.4 63/71] mm: page_vma_mapped_walk(): get vma_address_end() earlier

From: Sasha Levin
Date: Mon Jun 28 2021 - 10:48:16 EST


From: Hugh Dickins <hughd@xxxxxxxxxx>

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.

Link: https://lkml.kernel.org/r/4542b34d-862f-7cb4-bb22-e0df6ce830a2@xxxxxxxxxx
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Ralph Campbell <rcampbell@xxxxxxxxxx>
Cc: Wang Yugui <wangyugui@xxxxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Cc: Zi Yan <ziy@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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 fc68ab2d3ea1..93dd79ba9969 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -166,6 +166,15 @@ 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:
@@ -233,10 +242,6 @@ 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)
--
2.30.2