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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1qOqqm-00742b-Pu; Thu, 27 Jul 2023 02:35:36 +0000 Date: Thu, 27 Jul 2023 03:35:36 +0100 From: Matthew Wilcox To: "Huang, Ying" Cc: Yu Zhao , Ryan Roberts , Andrew Morton , Yin Fengwei , David Hildenbrand , Yang Shi , Zi Yan , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v3 2/3] mm: Implement folio_remove_rmap_range() Message-ID: References: <20230720112955.643283-1-ryan.roberts@arm.com> <20230720112955.643283-3-ryan.roberts@arm.com> <87r0ouw39n.fsf@yhuang6-desk2.ccr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87r0ouw39n.fsf@yhuang6-desk2.ccr.corp.intel.com> X-Stat-Signature: afi5d5ef6tfp3rk9u6rrhd1mt3ww8zfp X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 50FFE4001E X-Rspam-User: X-HE-Tag: 1690425354-322576 X-HE-Meta: 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 RMShSfAG 2cNvhrFeVx5I2AgFANnNjlD+vJmLIjuJCtLfYvjpL3K4s0h86ZgZ2rRdkNHMOhGMmrVm16ZhoDjx6475Sf9sAsOesOCalcFd4HOTdc09FvHz2e8r/YJ0Qxz9wOuSPJNfPBB7lwpMiNF+T7Stg0dvWfDL/FMSB/gqjUDF57y3i5VTlbFRP0tfl9KiT0u0nh4ic+ehCQeCen9uBl1W2g7++MBF/Fkd0Um2a58uVMFEnUVQsscI/pG/00i/pVg== 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: On Thu, Jul 27, 2023 at 09:29:24AM +0800, Huang, Ying wrote: > Matthew Wilcox writes: > > I think that can make sense. Because we limit to a single page table, > > specifying 'nr = 1 << PMD_ORDER' is the same as 'compound = true'. > > Just make it folio, page, nr, vma. I'd actually prefer it as (vma, > > folio, page, nr), but that isn't the convention we've had in rmap up > > until now. > > IIUC, even if 'nr = 1 << PMD_ORDER', we may remove one PMD 'compound' > mapping, or 'nr' PTE mapping. So, we will still need 'compound' (or > some better name) as parameter. Oh, this is removing ... so you're concerned with the case where we've split the PMD into PTEs, but all the PTEs are still present in a single page table? OK, I don't have a good answer to that. Maybe that torpedoes the whole idea; I'll think about it.