linux-kernel - [PATCH 04/11] mm: page_vma_mapped

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Date:   Wed, 9 Jun 2021 23:40:08 -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 04/11] mm: page_vma_mapped_walk(): use pmde for *pvmw->pmd

page_vma_mapped_walk() cleanup: re-evaluate pmde after taking lock, then
use it in subsequent tests, instead of repeatedly dereferencing pointer.

Signed-off-by: Hugh Dickins <hughd@...gle.com>
Cc: <stable@...r.kernel.org>
---
 mm/page_vma_mapped.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index 973c3c4e72cc..81000dd0b5da 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -194,18 +194,19 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
 
 	if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde)) {
 		pvmw->ptl = pmd_lock(mm, pvmw->pmd);
-		if (likely(pmd_trans_huge(*pvmw->pmd))) {
+		pmde = *pvmw->pmd;
+		if (likely(pmd_trans_huge(pmde))) {
 			if (pvmw->flags & PVMW_MIGRATION)
 				return not_found(pvmw);
-			if (pmd_page(*pvmw->pmd) != page)
+			if (pmd_page(pmde) != page)
 				return not_found(pvmw);
 			return true;
-		} else if (!pmd_present(*pvmw->pmd)) {
+		} else if (!pmd_present(pmde)) {
 			if (thp_migration_supported()) {
 				if (!(pvmw->flags & PVMW_MIGRATION))
 					return not_found(pvmw);
-				if (is_migration_entry(pmd_to_swp_entry(*pvmw->pmd))) {
-					swp_entry_t entry = pmd_to_swp_entry(*pvmw->pmd);
+				if (is_migration_entry(pmd_to_swp_entry(pmde))) {
+					swp_entry_t entry = pmd_to_swp_entry(pmde);
 
 					if (migration_entry_to_page(entry) != page)
 						return not_found(pvmw);
-- 
2.26.2