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[70.27.3.10]) by smtp.gmail.com with ESMTPSA id l1-20020a05620a28c100b006b958c34bf1sm3222130qkp.10.2022.08.16.13.35.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 Aug 2022 13:35:05 -0700 (PDT) Date: Tue, 16 Aug 2022 16:35:04 -0400 From: Peter Xu To: huang ying Cc: Alistair Popple , linux-mm@kvack.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, "Sierra Guiza, Alejandro (Alex)" , Felix Kuehling , Jason Gunthorpe , John Hubbard , David Hildenbrand , Ralph Campbell , Matthew Wilcox , Karol Herbst , Lyude Paul , Ben Skeggs , Logan Gunthorpe , paulus@ozlabs.org, linuxppc-dev@lists.ozlabs.org, Huang Ying , stable@vger.kernel.org Subject: Re: [PATCH v2 1/2] mm/migrate_device.c: Copy pte dirty bit to page Message-ID: References: <6e77914685ede036c419fa65b6adc27f25a6c3e9.1660635033.git-series.apopple@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_NONE,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 16, 2022 at 04:10:29PM +0800, huang ying wrote: > > @@ -193,11 +194,10 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, > > bool anon_exclusive; > > pte_t swp_pte; > > > > + flush_cache_page(vma, addr, pte_pfn(*ptep)); > > + pte = ptep_clear_flush(vma, addr, ptep); > > Although I think it's possible to batch the TLB flushing just before > unlocking PTL. The current code looks correct. If we're with unconditionally ptep_clear_flush(), does it mean we should probably drop the "unmapped" and the last flush_tlb_range() already since they'll be redundant? If that'll need to be dropped, it looks indeed better to still keep the batch to me but just move it earlier (before unlock iiuc then it'll be safe), then we can keep using ptep_get_and_clear() afaiu but keep "pte" updated. Thanks, -- Peter Xu