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[99.254.121.117]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-451c870016csm22526741cf.19.2024.08.09.09.09.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 09 Aug 2024 09:09:27 -0700 (PDT) From: Peter Xu To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Sean Christopherson , Oscar Salvador , Jason Gunthorpe , Axel Rasmussen , linux-arm-kernel@lists.infradead.org, x86@kernel.org, peterx@redhat.com, Will Deacon , Gavin Shan , Paolo Bonzini , Zi Yan , Andrew Morton , Catalin Marinas , Ingo Molnar , Alistair Popple , Borislav Petkov , David Hildenbrand , Thomas Gleixner , kvm@vger.kernel.org, Dave Hansen , Alex Williamson , Yan Zhao Subject: [PATCH 06/19] mm/pagewalk: Check pfnmap early for folio_walk_start() Date: Fri, 9 Aug 2024 12:08:56 -0400 Message-ID: <20240809160909.1023470-7-peterx@redhat.com> X-Mailer: git-send-email 2.45.0 In-Reply-To: <20240809160909.1023470-1-peterx@redhat.com> References: <20240809160909.1023470-1-peterx@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240809_090936_874122_D99B18FF X-CRM114-Status: GOOD ( 12.71 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Pfnmaps can always be identified with special bits in the ptes/pmds/puds. However that's unnecessary if the vma is stable, and when it's mapped under VM_PFNMAP | VM_IO. Instead of adding similar checks in all the levels for huge pfnmaps, let folio_walk_start() fail even earlier for these mappings. It's also something gup-slow already does, so make them match. Cc: David Hildenbrand Signed-off-by: Peter Xu --- mm/pagewalk.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/mm/pagewalk.c b/mm/pagewalk.c index cd79fb3b89e5..fd3965efe773 100644 --- a/mm/pagewalk.c +++ b/mm/pagewalk.c @@ -727,6 +727,11 @@ struct folio *folio_walk_start(struct folio_walk *fw, p4d_t *p4dp; mmap_assert_locked(vma->vm_mm); + + /* It has no folio backing the mappings at all.. */ + if (vma->vm_flags & (VM_IO | VM_PFNMAP)) + return NULL; + vma_pgtable_walk_begin(vma); if (WARN_ON_ONCE(addr < vma->vm_start || addr >= vma->vm_end))