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Thu, 07 May 2026 02:34:33 -0700 (PDT) Date: Thu, 7 May 2026 09:34:33 +0000 From: Wei Yang To: Alexander Gordeev Cc: Andrew Morton , David Hildenbrand , Lorenzo Stoakes , Anshuman Khandual , Oscar Salvador , linux-s390@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Gerald Schaefer , Heiko Carstens , Vasily Gorbik Subject: Re: [PATCH v2] mm/page_vma_mapped_walk: Use ptep_get_lockless() for lockless access Message-ID: <20260507093433.q5xybwumryxclnqy@master> Reply-To: Wei Yang References: <20260504130434.2285053-1-agordeev@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260504130434.2285053-1-agordeev@linux.ibm.com> User-Agent: NeoMutt/20170113 (1.7.2) X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 797FE20007 X-Rspam-User: X-Stat-Signature: pfexqywqjg1eg1azg3fafnwyuy837sik X-HE-Tag: 1778146476-32472 X-HE-Meta: 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 32sFwSZ4 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, May 04, 2026 at 03:04:34PM +0200, Alexander Gordeev wrote: >Switch from ptep_get() to ptep_get_lockless() accessor for >PTE reads when no lock is taken. > >Signed-off-by: Alexander Gordeev >--- > mm/page_vma_mapped.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > >diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c >index a4d52fdb3056..6559e17f11c2 100644 >--- a/mm/page_vma_mapped.c >+++ b/mm/page_vma_mapped.c >@@ -41,7 +41,7 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw, pmd_t *pmdvalp, > if (!pvmw->pte) > return false; > >- ptent = ptep_get(pvmw->pte); >+ ptent = ptep_get_lockless(pvmw->pte); > > if (pte_none(ptent)) { > return false; >@@ -310,7 +310,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw) > goto restart; > } > pvmw->pte++; >- } while (pte_none(ptep_get(pvmw->pte))); >+ } while (pte_none(ptep_get_lockless(pvmw->pte))); As Oscar mentioned in lkml.org/lkml/2026/4/27/630, map_pte() may take the lock. So probably it is not right? > > if (!pvmw->ptl) { > spin_lock(ptl); >-- >2.51.0 > -- Wei Yang Help you, Help me