linux-kernel - [PATCH 02/11] mm: page_vma_mapped_walk(): settle PageHuge on entry

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Date:   Wed, 9 Jun 2021 23:36:36 -0700 (PDT)
From:   Hugh Dickins <hughd@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
cc:     Hugh Dickins <hughd@...gle.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Yang Shi <shy828301@...il.com>,
        Wang Yugui <wangyugui@...-tech.com>,
        Matthew Wilcox <willy@...radead.org>,
        Alistair Popple <apopple@...dia.com>,
        Ralph Campbell <rcampbell@...dia.com>, Zi Yan <ziy@...dia.com>,
        Peter Xu <peterx@...hat.com>, Will Deacon <will@...nel.org>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: [PATCH 02/11] mm: page_vma_mapped_walk(): settle PageHuge on entry

page_vma_mapped_walk() cleanup: get the hugetlbfs PageHuge case
out of the way at the start, so no need to worry about it later.

Signed-off-by: Hugh Dickins <hughd@...gle.com>
Cc: <stable@...r.kernel.org>
---
 mm/page_vma_mapped.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index a6dbf714ca15..7c0504641fb8 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -153,10 +153,11 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
 	if (pvmw->pmd && !pvmw->pte)
 		return not_found(pvmw);
 
-	if (pvmw->pte)
-		goto next_pte;
-
 	if (unlikely(PageHuge(page))) {
+		/* The only possible mapping was handled on last iteration */
+		if (pvmw->pte)
+			return not_found(pvmw);
+
 		/* when pud is not present, pte will be NULL */
 		pvmw->pte = huge_pte_offset(mm, pvmw->address, page_size(page));
 		if (!pvmw->pte)
@@ -168,6 +169,9 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
 			return not_found(pvmw);
 		return true;
 	}
+
+	if (pvmw->pte)
+		goto next_pte;
 restart:
 	pgd = pgd_offset(mm, pvmw->address);
 	if (!pgd_present(*pgd))
@@ -233,7 +237,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
 			return true;
 next_pte:
 		/* Seek to next pte only makes sense for THP */
-		if (!PageTransHuge(page) || PageHuge(page))
+		if (!PageTransHuge(page))
 			return not_found(pvmw);
 		end = vma_address_end(page, pvmw->vma);
 		do {
-- 
2.26.2