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 83C26C982D8 for ; Fri, 18 Sep 2026 21:56:45 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 77CF86B008C; Fri, 18 Sep 2026 17:56:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 72BD36B0093; Fri, 18 Sep 2026 17:56:39 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 61C236B0095; Fri, 18 Sep 2026 17:56:39 -0400 (EDT) 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 3646C6B008C for ; Fri, 18 Sep 2026 17:56:39 -0400 (EDT) Received: from smtpin15.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 74249A02E3 for ; Fri, 18 Sep 2026 21:56:38 +0000 (UTC) X-FDA: 85228242876.15.A64E57F Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf17.hostedemail.com (Postfix) with ESMTP id A51B740004 for ; Fri, 18 Sep 2026 21:56:36 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=XB65sneM; spf=pass (imf17.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=1789768596; 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=OAk72ickShxyJvFA5YeKR74a2fmwIdRBZIAeemruYsU=; b=xQXshBgzZbzAqSl4L5jv0HHYmJj303rxVlF2lSakJgPF0SfzhQ3UUcZ8gkQyiMu5HHgaN1 Sb5HchhOUw1EyfgtjwizfMp1bne8K6nWXK1beucWu91o2+Pr/OvRwpZSm6G/6tTD085AZO AJo3K/hz4SEEVYmO/Ktzedrr2CbtE3U= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=XB65sneM; spf=pass (imf17.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; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1789768596; b=0BNxhGB2eCrL8OMwNJ8vh9I0SQmMzhFjh67JKprHFzOi+VpR870J5gnCU1/FR7gFYIqdrF Lvguf2fCIH+lGgQzxL4Cmk0cLS622i9ADgg7V1FsxMq9mQdvA8ao1z5eygl/rs48UoEcMm FCn0Lm2doXudFYKSTgPovjgllBtEZOI= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id D840A42A8F; Fri, 18 Sep 2026 21:56:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 074981F000FF; Fri, 18 Sep 2026 21:56:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789768595; bh=OAk72ickShxyJvFA5YeKR74a2fmwIdRBZIAeemruYsU=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=XB65sneM2a63IsZ87kuQsI3f1vWdWz99Ik+6ztN6zUGP/Sq9slNqoHDXisEf2fuj5 ynkG6VbCzPASLkjL3wkbBgNR1IIUTnHmA+BASmqqmhVUhjP9JkSjhgfO+bl0PFn8AP oUTbqQLI3fFwFe3DYOC+EZfqSpj6u1NVMv2axil5YHLq/AJ0g7fUB/HVsaibGzfjeN AiDDdJPvjsi0XIjYTD3Qp3SWnh23eb1ciSWWOEFG2zC9RTaL7V7dk/wuamZOh5dHPc BdNj0na5q+HNJXaXMScKLSf4JnTPk5mvPjjHOfim3AM8WwrV00fp3ycF+FzVogLkpw MGORCIMKd73/w== Message-ID: Date: Fri, 18 Sep 2026 23:56:25 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RESEND v7 08/29] mm: recognize PMD swap entries in the softleaf layer To: Usama Arif , Andrew Morton , chrisl@kernel.org, kasong@tencent.com, ljs@kernel.org, ziy@nvidia.com, linux-mm@kvack.org Cc: ying.huang@linux.alibaba.com, Baoquan He , willy@infradead.org, youngjun.park@lge.com, hannes@cmpxchg.org, riel@surriel.com, shakeel.butt@linux.dev, alex@ghiti.fr, kas@kernel.org, baohua@kernel.org, dev.jain@arm.com, baolin.wang@linux.alibaba.com, Nico Pache , "Liam R. Howlett" , ryan.roberts@arm.com, Vlastimil Babka , lance.yang@linux.dev, linux-kernel@vger.kernel.org, nphamcs@gmail.com, shikemeng@huaweicloud.com, yosry@kernel.org, qi.zheng@linux.dev, luizcap@redhat.com, kernel-team@meta.com References: <20260914122950.3283997-1-usama.arif@linux.dev> <20260914122950.3283997-9-usama.arif@linux.dev> 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: <20260914122950.3283997-9-usama.arif@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: A51B740004 X-Stat-Signature: maan1kwbuodfbd7ouf8neyujrb3hc7pq X-Rspam-User: X-HE-Tag: 1789768596-201999 X-HE-Meta: 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 6LUKO7Ee YeVHyZMC8CJ/TU7ml+S3St16QQoOevtsszc5qEXXzb9zxVAviIHPMZczpEUZviShgk+FaiP0bjH4rDHAEjAUDMOcENE0IKdhHeqDrSraLSN7dv/x+/UOzGx/f5zjnsNp3qmb4zo8zPooOnLVYsbnYglpWkZ3ObDVjbr3eIKpGKAczBv7So8FHsxT2rSh12atvuvtzlu2LsUCzSVg8YMAGXZWdae3+NzFOIWX6B7wDb0q1Y0H8De8NbTJ+wmBUG4kPirzddh+D7wbhLzJj3VQmFkh3BZpF2nx3p3Ot Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/14/26 14:27, Usama Arif wrote: > Reclaim splits a PMD-mapped anonymous THP into PTE-level swap entries > before unmapping it, so an ordinary swap entry has never had to appear in a > PMD. Later patches install one there instead, and the softleaf layer is "Prepare for ..." > where every consumer decodes non-present PMDs. > > Accept swap entries as valid PMD softleaves and add pmd_is_swap_entry(). > A swap entry carries no PFN, so make pmd_softleaf_to_folio() warn and > return NULL rather than interpret a swap offset as a page frame number. > > Unlike migration and device-private entries, a PMD swap entry can also > carry the swap-exclusive marker, which softleaf_from_pmd() has to strip > before decoding. Strip all three overlays unconditionally while we are > here: each clear is a plain bit clear, so testing first only buys a branch. > > Signed-off-by: Usama Arif > --- [...] > +/** > + * pmd_is_swap_entry() - Does this PMD entry encode an actual swap entry? > + * @pmd: PMD entry. > + * > + * Returns: true if the PMD encodes a swap entry, otherwise false. > + */ > +static inline bool pmd_is_swap_entry(pmd_t pmd) > +{ > + return softleaf_is_swap(softleaf_from_pmd(pmd)); > } We don't have a pte_is_swap_entry(), I guess because we always want to handle different softleaf types through softleaf_from_pte() first. > > /** > * pmd_is_valid_softleaf() - Is this PMD entry a valid softleaf entry? > * @pmd: PMD entry. > * > - * PMD leaf entries are valid only if they are device private or migration > - * entries. This function asserts that a PMD leaf entry is valid in this > - * respect. > + * PMD leaf entries are valid only if they are device private, migration, > + * or swap entries. This function asserts that a PMD leaf entry is valid > + * in this respect. > * > * Returns: true if the PMD entry is a valid leaf entry, otherwise false. > */ > @@ -660,10 +670,12 @@ static inline bool pmd_is_valid_softleaf(pmd_t pmd) > * pmd_softleaf_to_folio() - Convert the PMD softleaf entry to a folio. > * @pmd: PMD entry. > * > - * The PMD entry is expected to be a valid PMD softleaf entry. > + * The PMD entry is expected to be a valid PMD softleaf entry that references a > + * PFN, that is a migration or device private entry. A PMD swap entry is a valid > + * softleaf entry but encodes swap slots rather than a PFN, so it has no folio. > * > - * Returns: the folio the softleaf entry references if this is a valid softleaf > - * entry, otherwise NULL. > + * Returns: the folio the softleaf entry references, or NULL if the entry is not > + * a valid PMD softleaf entry or does not reference a PFN. > */ > static inline struct folio *pmd_softleaf_to_folio(pmd_t pmd) > { > @@ -673,6 +685,10 @@ static inline struct folio *pmd_softleaf_to_folio(pmd_t pmd) > VM_WARN_ON_ONCE(true); > return NULL; > } > + if (!softleaf_has_pfn(entry)) { > + VM_WARN_ON_ONCE(true); > + return NULL; softleaf_to_folio() does a VM_WARN_ON_ONCE(!softleaf_has_pfn(entry)); Just curious: why is that not sufficient? Which could would we expect to call into this fuction with nonesense? (same applies to the existing runtime check) Acked-by: David Hildenbrand (Arm) -- Cheers, David