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 5890547A0C4 for ; Thu, 27 Aug 2026 16:54:18 +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=1787849662; cv=none; b=sQb6cqt1VjYvYcd5554lKZzzc8nL8go76OEWI5oXfMFrlWhqhYESj0bJz8dq1JJA1M7Ztxj7UHDAbUqxFvjwJyOyA/tQcKnzmK9RmIHNL1q8QwRDpe25aYdtHew1Cc4Dmy0MhWX35HWeQmFrRgp+OX7rMfE0tFUDV3V1yrXYiao= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787849662; c=relaxed/simple; bh=u11lJuZ3CHy20gCd2pC2khIydn89D9sUB56pU5B3pww=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=UK5CelsN5q96u7VTEF3BuQ1fwE/cmGVQ/bvttPt7HeCdGChoyBrB5QYQWBuGBVH4bmB31xrLJhR9QjDAkEHWlR/yCVrK3puMOoluDvv0S1Q8CvWfJcfVTJGUfjNiKCrFSXMOA8kTJkD3/7h6oODYwLwBIW9WIkDrX/xI/hhFXj8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Q1mbqkIR; 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="Q1mbqkIR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 557821F000E9; Thu, 27 Aug 2026 16:54:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787849657; bh=/0EijgfI0VhQhjrOTV+mfho0EuTlFA7vhzH58UT/Nl4=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Q1mbqkIRp/j8VBTOJgQerAlZU8RI7OgMeuHkcQerXu9CaZBcqP7GmXXu/I7HJd4UV nvesbXLzUiwZJILNPf+do8UBEBx2LlzwBCFJV4eUzdKAYa6h5uSoIJ84Zkl7QawPdb Kb57R5YJkfKxgl8s56xglIX1+EAU882cbnWtS827eSn5DSGlkG9lEqkYhhD9v3zSq5 2+oobrJHgm0lDln30e2YrGv5zDLds5wuUgPLaGHKREyWeNjoSp2hDzL3LqPskXtk87 6BlFyemKV7gEye1DEnBcLG5K4Wy24J50jRxArPG3d3ew4VqgxEQT/pzACBPe6X8kKD BxcsE9VUob95w== Message-ID: Date: Thu, 27 Aug 2026 18:54:09 +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 v3 16/18] mm/huge_memory: clarify supported split orders in comment To: kasong@tencent.com, linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Andrew Morton , Lorenzo Stoakes , Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Lance Yang , Usama Arif , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Chris Li , Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , Youngjun Park , Shivam Kalra , Kairui Song References: <20260821-swap-thp-cleanup-v3-0-9b43f5163238@tencent.com> <20260821-swap-thp-cleanup-v3-16-9b43f5163238@tencent.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: <20260821-swap-thp-cleanup-v3-16-9b43f5163238@tencent.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/20/26 20:55, Kairui Song via B4 Relay wrote: > From: Kairui Song > > The doc comment for __split_huge_page_to_list_to_order() needs an > update: only order 1 is rejected for anon and swapcache folios, > matching the new_order == 1 check in folio_check_splittable(). I'm confused, why is that not updated in patch #15, which also updates that comment? If there is some preexisting inconsistency, the comment should be fixed before patch #15. > > Also realign the continuation line of the function signature while at > it. > > Signed-off-by: Kairui Song > --- > mm/huge_memory.c | 11 +++++------ > 1 file changed, 5 insertions(+), 6 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 06f353f937d1..0a971ca48151 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -4400,11 +4400,10 @@ int folio_split_unmapped(struct folio *folio, unsigned int new_order) > * GUP pins, will result in the folio not getting split; instead, the caller > * will receive an -EAGAIN. > * > - * 4) @new_order > 1, usually. Order-1 is not supported for anon or swapcache > - * folios: anon folios need subpage 2 for _deferred_list, which order-1 > - * folios lack, and a swapcache folio may become anon once faulted in. > - * File-backed order-1 folios are supported, since they do not use > - * _deferred_list. > + * 4) @new_order != 1 for anon or swapcache. Anon folios need subpage 2 for > + * _deferred_list, which order-1 folios lack, and a swapcache folio may > + * become anon once faulted in. File-backed order-1 folios are supported, > + * since they do not use _deferred_list. > * > * After splitting, the caller's folio reference will be transferred to @page, > * resulting in a raised refcount of @page after this call. The other pages may > @@ -4432,7 +4431,7 @@ int folio_split_unmapped(struct folio *folio, unsigned int new_order) > * with the folio. Splitting to order 0 is compatible with all folios. > */ > int __split_huge_page_to_list_to_order(struct page *page, struct list_head *list, > - unsigned int new_order) > + unsigned int new_order) These functions should all be concerted to double-tab as we you them. -- Cheers, David