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 605ACEA3F2F for ; Tue, 10 Feb 2026 09:40:03 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8AA8B6B0005; Tue, 10 Feb 2026 04:40:02 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 8824F6B0088; Tue, 10 Feb 2026 04:40:02 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 763E86B0089; Tue, 10 Feb 2026 04:40:02 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 629096B0005 for ; Tue, 10 Feb 2026 04:40:02 -0500 (EST) Received: from smtpin10.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id E12DA8BA09 for ; Tue, 10 Feb 2026 09:40:01 +0000 (UTC) X-FDA: 84428050602.10.248B0E3 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf13.hostedemail.com (Postfix) with ESMTP id 2F56C20004 for ; Tue, 10 Feb 2026 09:40:00 +0000 (UTC) Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=B7lWpTip; spf=pass (imf13.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=1770716400; 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=YsZoBatqJujkGSoy53OMu5mmb2wpVoZDtkrDbecmkzU=; b=TgSnUvH9bXgtcg6n2PfSNlj+R8bEqc12R0T24w2fvHRDlRieobB+xgINnM8dHt9lpTt6sY QKKpnfG5fqqIYrlDl51IPN8Y32KiwALcMJCyaAjnJP3MQYd+DujRVcRchvNfPGJdBCM7MJ xx4Hdh7G6d0JGbJ4Oam4CZDpTwReztI= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=B7lWpTip; spf=pass (imf13.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=1770716400; a=rsa-sha256; cv=none; b=1qvsrEZzrXHaTzBMq/MkVSGmKsyXGjhc+Zfm/kKeCMZnF94G51u/aqCSyjcur5m2u+RdZx wE60T/sTiRo0cn9nzCssIJiG0G6Ak0bRwdcZRX8XejVAov4gSmsSO4VAxDQcdET9TF3rEs U7+OTMAd8jGO5XXwriZazQ5O44pAVe0= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 91B1660123; Tue, 10 Feb 2026 09:39:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5730BC116C6; Tue, 10 Feb 2026 09:39:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770716399; bh=Eccl98ukGWgNNJ3Ns+n3BAHpoXOLPuE1FhV9dtp8PE0=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=B7lWpTipz8Y9RgpbghBDeJ1gOQwvIaoHpCQoey7fC9NySgW6z8RDjmOKULKTduY60 4FBeV4bwR00MOG6RTRjI92ly147Jr8kaglgtPh5lH/zdd75gczl2DaoQGDRgulGWvs lvTdNoyAk5ia7oIGVLba0Am5a64y7zWcGQ1MvyBA6DTj3yL7n6y3H2RdIXlLO17aQC iEpHJUfKyLeIc5LUox9WlOsdCwP0eEsZlzvimRjXgAZXxqceiKpxEc+utSBXAEyi00 RTf2aWDbe//aC8LuGPUDluXqR+CISP9ydAaV6R20RMxVS7e/u6Awrn0V+SmWm+2+rD kH8D2iiHOMhLg== Message-ID: <76750d20-cdfe-41bb-a228-9b3f171675ec@kernel.org> Date: Tue, 10 Feb 2026 10:39:48 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [v7 11/16] mm/migrate_device: add THP splitting during migration To: Balbir Singh , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-mm@kvack.org Cc: akpm@linux-foundation.org, Zi Yan , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Oscar Salvador , Lorenzo Stoakes , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lyude Paul , Danilo Krummrich , David Airlie , Simona Vetter , Ralph Campbell , =?UTF-8?Q?Mika_Penttil=C3=A4?= , Matthew Brost , Francois Dugast References: <20251001065707.920170-1-balbirs@nvidia.com> <20251001065707.920170-12-balbirs@nvidia.com> <13f3fcda-7328-4aa5-afc6-75a294a82b2a@nvidia.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: <13f3fcda-7328-4aa5-afc6-75a294a82b2a@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Stat-Signature: x9jueb8oheqzc3ed9s5pg19iczpdgugg X-Rspamd-Queue-Id: 2F56C20004 X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1770716400-812982 X-HE-Meta: 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 KE/U45r0 /ScDUZCnjF1UpcGd0/RquaO/Kr0hUK/Hl5/1P7ZuWksN3igRejkUuTiqqUFwDamdRqk89YITo/7VZgZxT31CD4w8el0BA5T2ZdmXRx4fo5ZkVcZpHpKoYJtAp0Zv0ysbSEzhqaqTuLUzUrLT5Z2952nU5oXGiOCUPLjkFufAf0y1e/4PYineWxCKqd5msHXZ54cZ9MiyEUjShWaHrxWikLS7cFsy4xwR/DVn1QJXr2A9+2EkVnbWhKCHptO1B27AtLKz/0scRNF4i7Jkx50CgXxkHlnZ4fh3szQA5lZXGn93UIKkTGjqCMAymr9LSIpOsgbdNx60JK/elcqe+G+C75Y20qHNZjbXdyMLQ3Z/n9jqX0C2uvI/RDA/asW2ZD31I+4Xalg7IyGA3vXz8xJMytKvGuA== 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 2/9/26 22:57, Balbir Singh wrote: > On 2/10/26 03:00, David Hildenbrand (Arm) wrote: >> >>> index 8c95a658b3ec..022b0729f826 100644 >>> --- a/mm/huge_memory.c >>> +++ b/mm/huge_memory.c >>> @@ -3463,15 +3463,6 @@ static void __split_folio_to_order(struct folio *folio, int old_order, >>>           new_folio->mapping = folio->mapping; >>>           new_folio->index = folio->index + i; >>>   -        /* >>> -         * page->private should not be set in tail pages. Fix up and warn once >>> -         * if private is unexpectedly set. >>> -         */ >>> -        if (unlikely(new_folio->private)) { >>> -            VM_WARN_ON_ONCE_PAGE(true, new_head); >>> -            new_folio->private = NULL; >>> -        } >>> - >> >> Balbir, why did you drop this check? >> Thanks for your reply. > > Are we running into this somewhere? This change clearly seems unrelated to the intent of the > patch that made this change (by me). We stumbled over its surprise removal while discussing something related. I thought you removed it because of some ZONE_DEVICE magic; the check has been proven helpful to catch bugs in the past. We always document carefully what our patches do, and why; and avoid doing unrelated things in our patches where possible. > I was seeing new_folio->private as NULL everywhere during > my testing and so I removed the check, happy to bring this defensive test back. I'll take care of re-adding it if is still useful after the other ->private changes we are planning. -- Cheers, David