From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 6A290D1A61E for ; Fri, 9 Jan 2026 13:19:28 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B7B206B0088; Fri, 9 Jan 2026 08:19:27 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id B27FC6B0089; Fri, 9 Jan 2026 08:19:27 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A0A166B008A; Fri, 9 Jan 2026 08:19:27 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 8CAEA6B0088 for ; Fri, 9 Jan 2026 08:19:27 -0500 (EST) Received: from smtpin10.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 413771A07B1 for ; Fri, 9 Jan 2026 13:19:27 +0000 (UTC) X-FDA: 84312481974.10.B54C2BF Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf30.hostedemail.com (Postfix) with ESMTP id 6C2C980010 for ; Fri, 9 Jan 2026 13:19:25 +0000 (UTC) Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=YUSONdW5; spf=pass (imf30.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1767964765; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=ioXowgmpNI0UKX6q4o0eJgu7Lpuu95sk8b6raaeg3Qg=; b=G8+fMTp6/Ww8j7VrhRae2HJYuTqgvzG/L24fxlzcGoLGLBHfpHmFN9swRoFvkYIBVh34RC 8HW2ZHMz6vUYcRUBOkSwLJ1PZVfahiPC2+oT0hQKkuw6pVNLtyCNoKrbVzSkpsMjc1uFqo VZCXI5yO/i5G+7ZBRhbxr4Hfk2UGZ9U= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=YUSONdW5; spf=pass (imf30.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1767964765; a=rsa-sha256; cv=none; b=EHzIADYE6mupGI7eiQVNHs2QYGgNAiULDsJa1l7WnVYiZeY+481Lfogy1I6kEwPiOUnuTq cuW70D8yBQ9SiUMfB9q8Y5k/YklIjl9mRhVqhEomWb+00vZc9ZQMDSPaZ6ctFR+qYFc6jh AMbNecADE/augKXE18BBOPBBpL7IzvU= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 4757643A0F; Fri, 9 Jan 2026 13:19:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D83ADC4CEF1; Fri, 9 Jan 2026 13:19:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1767964764; bh=dOxdIeEYnf0HHhRSlCVN+8qvKXOjd/cuc/y3jSDfBf4=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=YUSONdW55AHnI3b6E7AM+H4ziSAbRNNojnS9YaKKU56OSEAVcyjGNmbj6ESfHJ3V5 xf67oZKNsHgnOLFuemh01jIB8kvlYYLup79S+W+UOwzKpa/XM91lGXBwGEr91CArqJ dNtKCj7HeuNPuSE9dlKijCprNkLxX5uoFRilwErcAEIWAGVj9sNDdAxO7DQ6ZhTPZt 04mQOhkgpmVlqbCRpYUPBFRYvsMqel6SzBsAaCB4Fs/b+9EZ2xUWtLOpD8sdViTUGx nJJw7wuj4MIEt9ouViJadObqt9nlWeGsYHnGauTsWRL37Gq9GujZHd5hFuHKr1mB3C Hn3TsHoXRQ0FA== Message-ID: <59fb1669-2908-4cab-b3c0-b97479da3fb9@kernel.org> Date: Fri, 9 Jan 2026 14:19:16 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/7] mm: Add folio_split_unref helper To: Francois Dugast , intel-xe@lists.freedesktop.org Cc: dri-devel@lists.freedesktop.org, Matthew Brost , Balbir Singh , Andrew Morton , Lorenzo Stoakes , Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Alistair Popple References: <20260109085605.443316-1-francois.dugast@intel.com> <20260109085605.443316-2-francois.dugast@intel.com> From: "David Hildenbrand (Red Hat)" 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAa2VybmVsLm9yZz7CwY0EEwEIADcWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCaKYhwAIbAwUJJlgIpAILCQQVCgkIAhYCAh4FAheAAAoJEE3eEPcA/4Naa5EP/3a1 9sgS9m7oiR0uenlj+C6kkIKlpWKRfGH/WvtFaHr/y06TKnWn6cMOZzJQ+8S39GOteyCCGADh 6ceBx1KPf6/AvMktnGETDTqZ0N9roR4/aEPSMt8kHu/GKR3gtPwzfosX2NgqXNmA7ErU4puf zica1DAmTvx44LOYjvBV24JQG99bZ5Bm2gTDjGXV15/X159CpS6Tc2e3KvYfnfRvezD+alhF XIym8OvvGMeo97BCHpX88pHVIfBg2g2JogR6f0PAJtHGYz6M/9YMxyUShJfo0Df1SOMAbU1Q Op0Ij4PlFCC64rovjH38ly0xfRZH37DZs6kP0jOj4QdExdaXcTILKJFIB3wWXWsqLbtJVgjR YhOrPokd6mDA3gAque7481KkpKM4JraOEELg8pF6eRb3KcAwPRekvf/nYVIbOVyT9lXD5mJn IZUY0LwZsFN0YhGhQJ8xronZy0A59faGBMuVnVb3oy2S0fO1y/r53IeUDTF1wCYF+fM5zo14 5L8mE1GsDJ7FNLj5eSDu/qdZIKqzfY0/l0SAUAAt5yYYejKuii4kfTyLDF/j4LyYZD1QzxLC MjQl36IEcmDTMznLf0/JvCHlxTYZsF0OjWWj1ATRMk41/Q+PX07XQlRCRcE13a8neEz3F6we 08oWh2DnC4AXKbP+kuD9ZP6+5+x1H1zEzsFNBFXLn5EBEADn1959INH2cwYJv0tsxf5MUCgh Cj/CA/lc/LMthqQ773gauB9mN+F1rE9cyyXb6jyOGn+GUjMbnq1o121Vm0+neKHUCBtHyseB fDXHA6m4B3mUTWo13nid0e4AM71r0DS8+KYh6zvweLX/LL5kQS9GQeT+QNroXcC1NzWbitts 6TZ+IrPOwT1hfB4WNC+X2n4AzDqp3+ILiVST2DT4VBc11Gz6jijpC/KI5Al8ZDhRwG47LUiu Qmt3yqrmN63V9wzaPhC+xbwIsNZlLUvuRnmBPkTJwwrFRZvwu5GPHNndBjVpAfaSTOfppyKB Tccu2AXJXWAE1Xjh6GOC8mlFjZwLxWFqdPHR1n2aPVgoiTLk34LR/bXO+e0GpzFXT7enwyvF FFyAS0Nk1q/7EChPcbRbhJqEBpRNZemxmg55zC3GLvgLKd5A09MOM2BrMea+l0FUR+PuTenh 2YmnmLRTro6eZ/qYwWkCu8FFIw4pT0OUDMyLgi+GI1aMpVogTZJ70FgV0pUAlpmrzk/bLbRk F3TwgucpyPtcpmQtTkWSgDS50QG9DR/1As3LLLcNkwJBZzBG6PWbvcOyrwMQUF1nl4SSPV0L LH63+BrrHasfJzxKXzqgrW28CTAE2x8qi7e/6M/+XXhrsMYG+uaViM7n2je3qKe7ofum3s4v q7oFCPsOgwARAQABwsF8BBgBCAAmAhsMFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAmic2qsF CSZYCKEACgkQTd4Q9wD/g1oq0xAAsAnw/OmsERdtdwRfAMpC74/++2wh9RvVQ0x8xXvoGJwZ rk0Jmck1ABIM//5sWDo7eDHk1uEcc95pbP9XGU6ZgeiQeh06+0vRYILwDk8Q/y06TrTb1n4n 7FRwyskKU1UWnNW86lvWUJuGPABXjrkfL41RJttSJHF3M1C0u2BnM5VnDuPFQKzhRRktBMK4 GkWBvXlsHFhn8Ev0xvPE/G99RAg9ufNAxyq2lSzbUIwrY918KHlziBKwNyLoPn9kgHD3hRBa Yakz87WKUZd17ZnPMZiXriCWZxwPx7zs6cSAqcfcVucmdPiIlyG1K/HIk2LX63T6oO2Libzz 7/0i4+oIpvpK2X6zZ2cu0k2uNcEYm2xAb+xGmqwnPnHX/ac8lJEyzH3lh+pt2slI4VcPNnz+ vzYeBAS1S+VJc1pcJr3l7PRSQ4bv5sObZvezRdqEFB4tUIfSbDdEBCCvvEMBgoisDB8ceYxO cFAM8nBWrEmNU2vvIGJzjJ/NVYYIY0TgOc5bS9wh6jKHL2+chrfDW5neLJjY2x3snF8q7U9G EIbBfNHDlOV8SyhEjtX0DyKxQKioTYPOHcW9gdV5fhSz5tEv+ipqt4kIgWqBgzK8ePtDTqRM qZq457g1/SXSoSQi4jN+gsneqvlTJdzaEu1bJP0iv6ViVf15+qHuY5iojCz8fa0= In-Reply-To: <20260109085605.443316-2-francois.dugast@intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: ba3wbps4to55e8zrw13kcyaeipmf44tk X-Rspamd-Queue-Id: 6C2C980010 X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1767964765-921542 X-HE-Meta: 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 v0/1kB13 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 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 1/9/26 09:54, Francois Dugast wrote: > From: Matthew Brost > > Add folio_split_unref helper which splits an unreferenced folio split_unref reads like "split and unref". You probably want to call this something like "folio_split_frozen" ? The very definition of "frozen" is "refcount = 0 ", so you can simplify the documentation. Are the folios you want to pass in there completely unused (-> free) or might they still be in use (e.g., migration entries point at them during folio split) So I am not sure yet if this should be "folio_split_frozen()" or "folio_split_freed()" or sth like that. I'm not CCed on the other patches in the series or the cover letter, so I don't see the context. You should describe in this patch here in which context the function is supposed to be used in later commits. > (refcount == 0) into individual pages. Intended to be called on special > pages (e.g., device-private, DAX, etc.) when returning the folio to the > free page pool. > > Cc: Balbir Singh > Cc: Andrew Morton > Cc: David Hildenbrand > Cc: Lorenzo Stoakes > Cc: Zi Yan > Cc: Baolin Wang > Cc: "Liam R. Howlett" > Cc: Nico Pache > Cc: Ryan Roberts > Cc: Dev Jain > Cc: Barry Song > Cc: Lance Yang > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org > Suggested-by: Alistair Popple > Signed-off-by: Matthew Brost > Signed-off-by: Francois Dugast > --- > include/linux/huge_mm.h | 1 + > mm/huge_memory.c | 39 +++++++++++++++++++++++++++++++++++++++ > 2 files changed, 40 insertions(+) > > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h > index a4d9f964dfde..18cb9728d8f1 100644 > --- a/include/linux/huge_mm.h > +++ b/include/linux/huge_mm.h > @@ -369,6 +369,7 @@ enum split_type { > SPLIT_TYPE_NON_UNIFORM, > }; > > +void folio_split_unref(struct folio *folio); > int __split_huge_page_to_list_to_order(struct page *page, struct list_head *list, > unsigned int new_order); > int folio_split_unmapped(struct folio *folio, unsigned int new_order); > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 40cf59301c21..0eb9e6ad8639 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -3580,6 +3580,45 @@ static void __split_folio_to_order(struct folio *folio, int old_order, > ClearPageCompound(&folio->page); > } > > +/** > + * folio_split_unref() - split an unreferenced folio (refcount == 0) > + * @folio: the to-be-split folio > + * > + * Split an unreferenced folio (refcount == 0) into individual pages. > + * Intended to be called on special pages (e.g., device-private, DAX, etc.) > + * when returning the folio to the free page pool. > + */ > +void folio_split_unref(struct folio *folio) > +{ > + struct dev_pagemap *pgmap = page_pgmap(&folio->page); > + int order, i; > + > + folio->mapping = NULL; It's unclear why you mess with the mapping. Usually, throughout a folio split, we populate the folio->mapping to all split folios. -- Cheers David