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Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1rb6BA-00000005ko1-3kDg; Fri, 16 Feb 2024 21:55:32 +0000 Date: Fri, 16 Feb 2024 21:55:32 +0000 From: Matthew Wilcox To: Sidhartha Kumar Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, apopple@nvidia.com Subject: Re: [PATCH v2 4/6] mm/migrate_device: convert __migrate_device_pages() to folios Message-ID: References: <20240216211320.222431-1-sidhartha.kumar@oracle.com> <20240216211320.222431-4-sidhartha.kumar@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240216211320.222431-4-sidhartha.kumar@oracle.com> X-Rspamd-Queue-Id: 6ECFF18000C X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: pietyjdxquii7a9xb49rcbjz3e94b5h4 X-HE-Tag: 1708120536-59853 X-HE-Meta: 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 zpCZs9CN atPGT1FRru9vLEqoUM18z4yak9gcJYu/2TzVqPo8TGzrIV95YfRpbBbeqcDNNdgJN8gb71tFoFFwxPYUNruzHI8ueHvWGZr83YWrs89ZxeTfW3bDIGHychrdsdUF13T65UPg1KlCB/6CkiYzIJQOmxxrqzOddTT7XwHDWWcqt/TrT9cB0OzM7rcMojA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Feb 16, 2024 at 01:13:18PM -0800, Sidhartha Kumar wrote: > Use migrate_pfn_to_folio() so we can work with folios directly in > __migrate_device_pages(). i don't understand why this would be correct if we have multipage folios. > @@ -719,33 +719,29 @@ static void __migrate_device_pages(unsigned long *src_pfns, > migrate->pgmap_owner); > mmu_notifier_invalidate_range_start(&range); > } > - migrate_vma_insert_page(migrate, addr, newpage, > + migrate_vma_insert_page(migrate, addr, &dst->page, seems to me that a migration pfn is going to refer to a precise page. now you're telling it to insert the head page of the folio. isn't this wrong? > @@ -753,13 +749,11 @@ static void __migrate_device_pages(unsigned long *src_pfns, > continue; > } > > - if (migrate && migrate->fault_page == page) > - r = migrate_folio_extra(mapping, page_folio(newpage), > - page_folio(page), > - MIGRATE_SYNC_NO_COPY, 1); > + if (migrate && migrate->fault_page == &src->page) shouldn't this rather be "page_folio(migrate->fault_page) == src"? ie we're looking for two pages from the same folio, rather than the page being the same as the head page of the folio?