From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794393037; b=scu+EIhVWC9Utxn0XSrMeQH/CeTCWPvXPClqWMqPHsWeDCMNR4xFxv5yugPRFCYED6hm Ffs2j5DXtSt0ODR5uMxIoir6Atfs59cTAovma/upLLN8IJs5HUXy1dQWgvNTtULkTH8kO cRAh84vUEx9la/cYbPAkAuyzxASCDmajb74Y0g8Oie76+Q48bQOo4sAYoqtWnOhI2dFcB +OYN2V5wSqm2e1JbHipuM5kVUXHAmfI77GVDVTGXSq1kMaa8tLhH9vgXmqEm/ZbVQ7cBZ iqtB9y2b/34z6KTT8ZkWHo7SPunFRPOzRHno+5VmqFbKfEcr8TMhc0sh7h7IsgbN/Gg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794393037; h=Received:DKIM-Signature:Message-ID:Date:MIME-Version:User-Agent: Subject:To:Cc:References:From:Content-Language:Autocrypt:In-Reply-To: Content-Type:Content-Transfer-Encoding; bh=KxrhFMa8/sp9xXjPYISbhRzyRkp2BmT2lD81VC2uH5g=; b=Zs7js/Fm54NGeiX/yV0TzeiAGKCHIifkQCy/vdUAkqUU5T1o4yWegYDVeeJKjdo1QhkR oXsKvDZluIWVNhXEJEDjlCJOj/vgwxo69dduTiLzd1+RgbGG8/E67gukjz1duKT9wYdlt DOsfPA/AUk+STXm2bTk5SsYY6/LGSalM0WWXRol8rzeoy9/BIOLemvx2Vm2pDxKvCNHxH DVyunG9lzbSAwkIcDKNUS+iL/iQzBhDSqy43Abeqy1xQk+audoCyiQwOyROwSSih9A4QO IeTCepgO3VdIfpPoHvMndhd66uELhjQllHi+k3qh4Yr8JH6FFyZpD7PxYVSFnAdmDKg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=JrTLwSLE; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D2D5E606A330 for ; Wed, 11 Nov 2026 10:30:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=JrTLwSLE Received: by smtp.kernel.org (Postfix) with ESMTPSA id EB69F1F00A05; Wed, 11 Nov 2026 10:30:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794393037; bh=KxrhFMa8/sp9xXjPYISbhRzyRkp2BmT2lD81VC2uH5g=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=JrTLwSLEd+YvzAemdyR51xbG4OegeC7uVGwCapD1h/0s5JMcEnFwWTDyHw8hxhFYc Yceo4rD3o841E85q5UtJ63r9LzJ+/IPSvgm54TH6mNqnP/tb0WyhsqEDBspvr1nMgU Hu4Q34UrszFwNjN+s0A0uWuX0SBJx41Hhlkwlrl2IZ2jWWBFyeM5f6ONI7me+XJd2x tDLrSIQN0h+XzgIJDmF0lUAShZ6b6bEeZ/g2Px2DPD5n88Mxnvvk5FF5+ArOFgekE3 KuBbgHWL/Op3aP1kzP2GjMevvmUd+kFCCVz2h+/uqELmyOPdyL+R577xO/dD9peHYL sFm19EJSuqEpQ== Message-ID: Date: Tue, 10 Nov 2026 14:06:23 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 5/6] mm: gup: introduce gup_unshared_pages() To: Yeoreum Yun , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Jason Gunthorpe , John Hubbard , Peter Xu , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Andrew Morton , Rik van Riel , Yuan-Hao Hsu References: <20261109-refactor_gup_fast-v3-0-2aaef02df0e1@arm.com> <20261109-refactor_gup_fast-v3-5-2aaef02df0e1@arm.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20261109-refactor_gup_fast-v3-5-2aaef02df0e1@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/9/26 13:32, Yeoreum Yun wrote: > This is preparatory patch to make gup_fast_pte_range() batchable. > > Introduce gup_unshared_pages() to count consecutive pages within a folio > that do not require unsharing, and use it to implement gup_must_unshare(). > > Also add a folio argument to gup_must_unshare() so callers can reuse an > existing folio and avoid the compound_head() call implicit in PageAnon(). > > There is no functional change. > > Signed-off-by: Yeoreum Yun > --- > mm/gup.c | 111 +++++++++++++++++++++++++++++++++++++-------------------------- > 1 file changed, 66 insertions(+), 45 deletions(-) > > diff --git a/mm/gup.c b/mm/gup.c > index bfe83ce1411d5..c863bae33e2f1 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -633,58 +633,39 @@ static struct page *no_page_table(struct vm_area_struct *vma, > return NULL; > } > > -/* > - * Indicates for which pages that are write-protected in the page table, > - * whether GUP has to trigger unsharing via FAULT_FLAG_UNSHARE such that the > - * GUP pin will remain consistent with the pages mapped into the page tables > - * of the MM. > - * > - * Temporary unmapping of PageAnonExclusive() pages or clearing of > - * PageAnonExclusive() has to protect against concurrent GUP: > - * * Ordinary GUP: Using the PT lock > - * * GUP-fast and fork(): mm->write_protect_seq > - * * GUP-fast and KSM or temporary unmapping (swap, migration): see > - * folio_try_share_anon_rmap_*() > - * > - * Must be called with the (sub)page that's actually referenced via the > - * page table entry, which might not necessarily be the head page for a > - * PTE-mapped THP. > - * > - * If the vma is NULL, we're coming from the GUP-fast path and might have > - * to fallback to the slow path just to lookup the vma. > - */ > -static inline bool gup_must_unshare(struct vm_area_struct *vma, > - unsigned int flags, struct page *page) > +static unsigned long gup_unshared_pages(struct vm_area_struct *vma, Besides the function name, LGTM. gup_pages_requiring_unsharing() ? Don't quite like it, but something along those lines. -- Cheers, David