linux-kernel - [PATCH v2 03/12] arm: adjust_pte() use pte_offset_map

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Message-ID: <c959c62f-b186-cb41-55ab-59da79ece688@google.com>
Date:   Tue, 20 Jun 2023 00:43:50 -0700 (PDT)
From:   Hugh Dickins <hughd@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
cc:     Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Mike Rapoport <rppt@...nel.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Matthew Wilcox <willy@...radead.org>,
        David Hildenbrand <david@...hat.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Qi Zheng <zhengqi.arch@...edance.com>,
        Yang Shi <shy828301@...il.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Peter Xu <peterx@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will@...nel.org>, Yu Zhao <yuzhao@...gle.com>,
        Alistair Popple <apopple@...dia.com>,
        Ralph Campbell <rcampbell@...dia.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Steven Price <steven.price@....com>,
        SeongJae Park <sj@...nel.org>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Huang Ying <ying.huang@...el.com>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Zack Rusin <zackr@...are.com>, Jason Gunthorpe <jgg@...pe.ca>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Pasha Tatashin <pasha.tatashin@...een.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Minchan Kim <minchan@...nel.org>,
        Christoph Hellwig <hch@...radead.org>,
        Song Liu <song@...nel.org>,
        Thomas Hellstrom <thomas.hellstrom@...ux.intel.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Michael Ellerman <mpe@...erman.id.au>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Jann Horn <jannh@...gle.com>,
        Vishal Moola <vishal.moola@...il.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        linux-arm-kernel@...ts.infradead.org, sparclinux@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH v2 03/12] arm: adjust_pte() use pte_offset_map_nolock()

Instead of pte_lockptr(), use the recently added pte_offset_map_nolock()
in adjust_pte(): because it gives the not-locked ptl for precisely that
pte, which the caller can then safely lock; whereas pte_lockptr() is not
so tightly coupled, because it dereferences the pmd pointer again.

Signed-off-by: Hugh Dickins <hughd@...gle.com>
---
 arch/arm/mm/fault-armv.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/arm/mm/fault-armv.c b/arch/arm/mm/fault-armv.c
index ca5302b0b7ee..7cb125497976 100644
--- a/arch/arm/mm/fault-armv.c
+++ b/arch/arm/mm/fault-armv.c
@@ -117,11 +117,10 @@ static int adjust_pte(struct vm_area_struct *vma, unsigned long address,
 	 * must use the nested version.  This also means we need to
 	 * open-code the spin-locking.
 	 */
-	pte = pte_offset_map(pmd, address);
+	pte = pte_offset_map_nolock(vma->vm_mm, pmd, address, &ptl);
 	if (!pte)
 		return 0;
 
-	ptl = pte_lockptr(vma->vm_mm, pmd);
 	do_pte_lock(ptl);
 
 	ret = do_adjust_pte(vma, address, pfn, pte);
-- 
2.35.3