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 00715D26D60 for ; Fri, 9 Jan 2026 15:11:34 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 4F2746B0088; Fri, 9 Jan 2026 10:11:34 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 475B36B008C; Fri, 9 Jan 2026 10:11:34 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 34DF16B0092; Fri, 9 Jan 2026 10:11:34 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 21D566B0088 for ; Fri, 9 Jan 2026 10:11:34 -0500 (EST) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id C0DCA1AAAA for ; Fri, 9 Jan 2026 15:11:33 +0000 (UTC) X-FDA: 84312764466.02.8C88CE3 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf02.hostedemail.com (Postfix) with ESMTP id 1400D8000B for ; Fri, 9 Jan 2026 15:11:31 +0000 (UTC) Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=fSZakySj; spf=pass (imf02.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 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=1767971492; 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=khwm/bSHN3PX1PjrnS+3+ckVaSBmWQQcHL+HzPjFWbg=; b=KjYlmwnWzCYfmJVLfV8XsOHvp/VRfQSz4VAFDFLEPK1dXT528letal+6lRZTx9ia05mwsj ka1kHn+G6IfIYNxfegxFJj6F/Md+3WjYgbnY75Bo+YlnYXXUzA9srIAQywG8mFdm+tq+5h WW9DkOPb2SJEW26P2LITRqy0u2zV29k= ARC-Authentication-Results: i=1; imf02.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=fSZakySj; spf=pass (imf02.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 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=1767971492; a=rsa-sha256; cv=none; b=dvm9d8sGGBOlVGwvfPhMOdCRzIYcM53TSsBtYdIqDjzjzo83uLrrPkG/Te6Dd5QobXyaGi FsO+My7VzxBEovizma8nMfiJp/WOMRYNW5vyQ3wl6OCtC7msXPkz7LncFVK9nxP+AS3/Vi cz2qJkELCdrVWimRuZGCmRMPDR4oBcs= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 748E360151; Fri, 9 Jan 2026 15:11:31 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6881BC4CEF1; Fri, 9 Jan 2026 15:11:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1767971491; bh=2FBHrNHxevA7xEit3psQVoy33Em494KJnTdG6Fnk1wY=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=fSZakySjexp8G8Uu0Qz+AYFvOBvbPowqbgQ+u6hdU2jft9SSsnDPMWYRtoerKCThb Tppz6LSNxEvQN4B9A9LDh6y0sc3f2AHa9NEU/RBwVUABwOaxQrIpJoHb8n6XJ7WFEN c/ZU1/QBoUtebaWN/Ju+kycH1+Cly3f4wJTUCBLvHX3BPt/2aqZLfjlYuD/oGHE0GG m6s+4abpx0NmFh77ux70vvjS9d0q4YDTJHvM6PTOQjb0F77l3ZCZEUTqcLuAjB3XZB RLJEluiUmxXo9lCYUf9xDgtCZDZB5UFvabEDn0SngYXQVnYrio2l5wgUDbENPT+rIt W0mlzL2k1ZzRA== Message-ID: <85033126-c60a-4cac-8f6f-5bd2f6102fec@kernel.org> Date: Fri, 9 Jan 2026 16:11:23 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/7] mm: Add folio_split_unref helper To: Zi Yan Cc: Francois Dugast , intel-xe@lists.freedesktop.org, dri-devel@lists.freedesktop.org, Matthew Brost , Balbir Singh , Andrew Morton , Lorenzo Stoakes , 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> <59fb1669-2908-4cab-b3c0-b97479da3fb9@kernel.org> <1319a24a-bcfc-47e5-a022-f5d00994acc9@kernel.org> 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: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 1400D8000B X-Stat-Signature: cogbd3wiyf4yj7fxu8rpquo5yf5ofsoh X-HE-Tag: 1767971491-839085 X-HE-Meta: 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 veFKf2t4 iBT6CsMSvzKX6H2vWW/C6n65Fz2tgDRztIVMRDEV3ZlYT0QQegTVmuw6Ji93pneF2h+mzAWxRY5+aDMYWHvQL93toErZfdwcuQ6fIaitAY57ZFeZBIkyPHuTnpacWvjajh6xrMEWvTufZLwcUksfOoHFIIGYpbktmUVWlxVqfmMga38Dq3cQQHO6A+RfkzyDIoD6ZFrie/+RPy8xH7ZuhBuVXgRg2EhjjIhmKPI3xYL2CPvXTbWte03mPLxnCn2sGfZRgH1GRGu7deXb5AFP8qQDvXi7gQRTnB3FfGKjvPdWuw6f1xSwufa6RBP5T+ertoalCML87qJNg0mA= 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 15:30, Zi Yan wrote: > On 9 Jan 2026, at 8:26, David Hildenbrand (Red Hat) wrote: > >> On 1/9/26 14:19, David Hildenbrand (Red Hat) wrote: >>> 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. >>> >> >> Ah, I was CCed on #3 where we call this function on folios that are getting freed. >> >> In that case it would be acceptable to initialize folio->mapping (and folio->index?) of the split folios. Do we also have to initialize folio->flags, folio->private etc? >> >> See __split_huge_page_tail(). >> >> folio_split_freed() would likely be best, because then it is clearer that there is absolutely no state to copy from the large folio. > > Yes, basically, we do not have a reverse function of prep_compound_page() and > open codes the reverse process in free_pages_prepare(). For zone devices, > zone_device_page_init() calls prep_compound_page() to form a folio but > free_zone_device_folio() never does the reverse. FS DAX has its own > dax_folio_put() to do it. Alistair suggested to come up with a helper > function for both FS DAX and free_zone_device_folio(). > > Maybe free_zone_device_folio_prepare() is better. And put it in mm/memremap.c. That would be even better, if we can limit this completely to zone_device. -- Cheers David