From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 564A1334C08 for ; Tue, 16 Jun 2026 14:04:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781618649; cv=none; b=DsopsOjg2cbToJOwggc19vf3Hoj/AlIF+MGXqkSttrXc8CNmLH7wfiv1qxXzPPdwd31TtJ5VDhMngVb3qOJ9OpvAmMGYtRH2M3QxbKeJ9vzMfb0PuQx0GugCVe0yvIWNW15kbImKrL1ezitB4fx9S5oCPsUYPzBwY+p0J1npmIU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781618649; c=relaxed/simple; bh=3C5Qx7kjldp/kQ99kboC0QTUobYD0jzlzoqdncK6kQQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=bLTRTp4RR1oWSvr5BtDbDKy77YEvL1jj2ywergBgXs4arDfBmheCklJRfDDQzvFgRMExmSXFBAu2nNdPf8FhNFs17xoKqVqAirI4iscNhPwWnLKw0jr4arKYOLKraS40BEq64BVMh+Ul19OI6HM2soKFKYMDAEtYGHqyqAZKoWU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=heS7qKoI; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="heS7qKoI" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 63DD41F000E9; Tue, 16 Jun 2026 14:04:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781618648; bh=5cv4U/lCwTmC1Xu4fCZeo9kmaEne3SOba71hNwtJ2ZA=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=heS7qKoIs7GLheXLM0LdXqaE8U5e2V6+skaM9EFHXTFuQnZUHAUHupN0raqx6JJ+7 ankYbPAZkMcRuX7CWQOFcvmCNIVxRcM2282rFLaMN9+H73dTEeUilu8ioObWl128uR IgUA+hzNWFZp4w1lmQrlY9zr6G+b1HqGV6Mkk2YrD1jGCuc0Qtcobc37xOLWAZRtuK WLc79EguaTWIrTWqRgRXk4ENgaaLry1Hac44Oa+RscZEVFW3qzhJcqTPlbDJpdWNqo LDDn116OjgilAu6yXDE5H1CGf2f8YmaTdJyLVNG2I+DIf5Iw2dO3Ly+pGc46UAAhQH tbDTXSAhrYUgg== Message-ID: <2a1781f3-741b-4073-b23f-f5cb3f0d98e2@kernel.org> Date: Tue, 16 Jun 2026 16:04:00 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 09/12] mm/rmap: Add batched version of folio_try_share_anon_rmap_pte To: Dev Jain , akpm@linux-foundation.org, ljs@kernel.org, chrisl@kernel.org, kasong@tencent.com, hughd@google.com, liam@infradead.org Cc: riel@surriel.com, vbabka@kernel.org, harry@kernel.org, jannh@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, qi.zheng@linux.dev, shakeel.butt@linux.dev, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, bhe@redhat.com, youngjun.park@lge.com, baolin.wang@linux.alibaba.com, pfalcato@suse.de, ryan.roberts@arm.com, anshuman.khandual@arm.com References: <20260526063635.61721-1-dev.jain@arm.com> <20260526063635.61721-10-dev.jain@arm.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/26/26 08:36, Dev Jain wrote: > To enable batched unmapping of anonymous folios, we need to handle the > sharing of exclusive pages. Hence, a batched version of > folio_try_share_anon_rmap_pte is required. > > Currently, the sole purpose of nr_pages in __folio_try_share_anon_rmap is > to do some rmap sanity checks. Now, clear the PageAnonExclusive bit on a > batch of nr_pages. Refactor the function such that the clearing of the bit > can be done at one place without duplication. > > Note that __folio_try_share_anon_rmap can receive nr_pages == HPAGE_PMD_NR > from the PMD path, but currently we only clear the bit on the head page. > Retain this behaviour by setting nr_pages = 1 in case the caller is > folio_try_share_anon_rmap_pmd. > > While at it, convert nr_pages to unsigned long to future-proof from > overflow in case P4D-huge mappings etc get supported down the road. > I haven't made such a change in each function receiving nr_pages in > try_to_unmap_one - perhaps this can be done incrementally. > > Signed-off-by: Dev Jain > --- > include/linux/rmap.h | 52 +++++++++++++++++++++++++++++--------------- > 1 file changed, 35 insertions(+), 17 deletions(-) > > diff --git a/include/linux/rmap.h b/include/linux/rmap.h > index 8dc0871e5f001..64929490a7cfc 100644 > --- a/include/linux/rmap.h > +++ b/include/linux/rmap.h > @@ -706,17 +706,18 @@ static inline int folio_try_dup_anon_rmap_pmd(struct folio *folio, > } > > static __always_inline int __folio_try_share_anon_rmap(struct folio *folio, > - struct page *page, int nr_pages, enum pgtable_level level) > + struct page *page, unsigned long nr_pages, enum pgtable_level level) > { > + /* device private folios cannot get pinned via GUP. */ > + const bool pinnable = likely(!folio_is_device_private(folio)); We don't seem to have a lot of users of likely/unlikely when assigning variables, so I wonder if the compiler really uses that information then. git grep " = " | grep "likely(" | grep ";$" | wc -l 32 Maybe clearer to just push the "likely" into the actual two condition below. [...] > /** > - * folio_try_share_anon_rmap_pte - try marking an exclusive anonymous page > - * mapped by a PTE possibly shared to prepare > + * folio_try_share_anon_rmap_ptes - try marking exclusive anonymous pages > + * mapped by PTEs possibly shared to prepare > * for KSM or temporary unmapping > * @folio: The folio to share a mapping of > - * @page: The mapped exclusive page > + * @page: The first mapped exclusive page of the batch in the folio > + * @nr_pages: The number of pages to share in the folio (batch size) > * > * The caller needs to hold the page table lock and has to have the page table > * entries cleared/invalidated. > @@ -797,11 +807,19 @@ static __always_inline int __folio_try_share_anon_rmap(struct folio *folio, > * > * Returns 0 if marking the mapped page possibly shared succeeded. Returns > * -EBUSY otherwise. > + * > + * The caller needs to hold the page table lock. Isn't that stated further above? > */ > +static inline int folio_try_share_anon_rmap_ptes(struct folio *folio, > + struct page *page, unsigned long nr_pages) > +{ > + return __folio_try_share_anon_rmap(folio, page, nr_pages, PGTABLE_LEVEL_PTE); > +} > + > static inline int folio_try_share_anon_rmap_pte(struct folio *folio, > struct page *page) > { > - return __folio_try_share_anon_rmap(folio, page, 1, PGTABLE_LEVEL_PTE); > + return folio_try_share_anon_rmap_ptes(folio, page, 1); > } > > /** In general, LGTM. -- Cheers, David