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 1428DFED3FA for ; Fri, 24 Apr 2026 19:29:32 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5539E6B00AF; Fri, 24 Apr 2026 15:29:31 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 506D76B00B1; Fri, 24 Apr 2026 15:29:31 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3F42D6B00B2; Fri, 24 Apr 2026 15:29:31 -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 2E1136B00AF for ; Fri, 24 Apr 2026 15:29:31 -0400 (EDT) Received: from smtpin24.hostedemail.com (lb01b-stub [10.200.18.250]) by unirelay08.hostedemail.com (Postfix) with ESMTP id B1F471402A4 for ; Fri, 24 Apr 2026 19:29:30 +0000 (UTC) X-FDA: 84694438500.24.C12A4F3 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf20.hostedemail.com (Postfix) with ESMTP id 0A11C1C0008 for ; Fri, 24 Apr 2026 19:29:28 +0000 (UTC) Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b="kz/F3IYP"; spf=pass (imf20.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=1777058969; 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=LPDBEMMgmDfTV/OJSjXDo/CYCBkEdX9MSnfA3+/UEzk=; b=Rdqqlg3ABQCyuZ1VHuz/Dm9bER54YG4L3GFJA52Tq43/ZkuMusRJLRPJxn/8Yi+16/LkJA Wuvv9gtvcjcW2c8PY0JqIWmw/mvoZrV6nTFLsMKA7K4dJtzayOJQDkmGJ6yiGQEK+unvlp wWuZxQ+LvhnLLKyucGo844luDJ2iJJU= ARC-Authentication-Results: i=1; imf20.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b="kz/F3IYP"; spf=pass (imf20.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=1777058969; a=rsa-sha256; cv=none; b=dF8zfEfrVZwjiXJU3/angGnjIAtXM3b8Dn+jGi2SBrlVEzTbjJkOyKR5XY5bMbB9WMWK1l 84VQIh2HFrnvMeG3tmRJiFU3VaCoI7FIitf7Nc1YkO94uoJDCNOdeqtmgPn21zZrTWK11M Ks4xdbSRMPdOJq7pn6DWlZzrcX1eYfk= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 64EA7600AE; Fri, 24 Apr 2026 19:29:28 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 36A49C19425; Fri, 24 Apr 2026 19:29:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777058968; bh=kavgWFCSVJr+yXjb86gLc2o7iHJh/J0BL1U0+J76Rro=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=kz/F3IYPrZp1IphSARmdw8OPZ1EBmXc7nvbl6gA+sEJEd4zwGa7pdXqtsyWgefZ4F ts21+WQctCKyn6Ab7rJ2vTVFBlFfrMF5Gq3lA5H7YdJvzq6zY+edPITRNZT8QDg/2c Phf9LxvN3lIcI4ki3zhu8uA136wUT9w+VTrHN2t/btS7SueVPOtIlfAKkj3bC8zziZ xHWskCpOOdjTqLmLz9sN/FF2Bzx2SJltQ65pgcg3b41K69lmGIckmpoLwm4CCPVHKj vnJvan5pooE5GYvAUYSjW/KiQ50SueL3Wfy94DD2zMsyHlG4pH5I399HCL9IPFnYxL froKodkU+B30w== Message-ID: <79e164a2-47ce-4a02-82f5-164515760b6d@kernel.org> Date: Fri, 24 Apr 2026 21:29:18 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] mm/huge_memory: return true if split_huge_pmd_locked() split PMD to migration entry To: Wei Yang , akpm@linux-foundation.org, ljs@kernel.org, ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, riel@surriel.com, vbabka@kernel.org, harry@kernel.org, jannh@google.com, rppt@kernel.org, surenb@google.com, mhocko@suse.com, shuah@kernel.org Cc: linux-mm@kvack.org, Gavin Guo References: <20260415010839.20124-1-richard.weiyang@gmail.com> <20260415010839.20124-2-richard.weiyang@gmail.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: <20260415010839.20124-2-richard.weiyang@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: nex6g7rbwcrrw5t9jgz8tdt7su7cw83d X-Rspamd-Queue-Id: 0A11C1C0008 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1777058968-981257 X-HE-Meta: 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 3THkylt0 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/15/26 03:08, Wei Yang wrote: > When @freeze is set to true, split_huge_pmd_locked() is intended to > split the PMD to migration entry. But if it doesn't manage to clear > PageAnonExclusive(), it just split PMD and leave the folio mapped > through PTE. > > This patch let split_huge_pmd_locked() return true to indicate it does > split PMD to migration entry. With this knowledge, we can return > directly in try_to_migrate_one() if it does. > > Signed-off-by: Wei Yang > Cc: Gavin Guo > Cc: "David Hildenbrand (Red Hat)" > Cc: Zi Yan > Cc: Baolin Wang > Cc: Lance Yang > --- [...] > static inline bool unmap_huge_pmd_locked(struct vm_area_struct *vma, > unsigned long addr, pmd_t *pmdp, > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 970e077019b7..ec84bb4a0cc3 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -3087,7 +3087,7 @@ static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, > pmd_populate(mm, pmd, pgtable); > } > > -static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > +static bool __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > unsigned long haddr, bool freeze) > { > struct mm_struct *mm = vma->vm_mm; > @@ -3096,7 +3096,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > pgtable_t pgtable; > pmd_t old_pmd, _pmd; > bool soft_dirty, uffd_wp = false, young = false, write = false; > - bool anon_exclusive = false, dirty = false; > + bool anon_exclusive = false, dirty = false, ret = false; > unsigned long addr; > pte_t *pte; > int i; > @@ -3118,13 +3118,13 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > if (arch_needs_pgtable_deposit()) > zap_deposited_table(mm, pmd); > if (vma_is_special_huge(vma)) > - return; > + return ret; Why not "return false" in these cases where it really can always only false? > if (unlikely(pmd_is_migration_entry(old_pmd))) { > const softleaf_t old_entry = softleaf_from_pmd(old_pmd); > > folio = softleaf_to_folio(old_entry); > } else if (is_huge_zero_pmd(old_pmd)) { > - return; > + return ret; > } else { > page = pmd_page(old_pmd); > folio = page_folio(page); > @@ -3136,7 +3136,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > folio_put(folio); > } > add_mm_counter(mm, mm_counter_file(folio), -HPAGE_PMD_NR); > - return; > + return ret; > } > > if (is_huge_zero_pmd(*pmd)) { > @@ -3149,7 +3149,8 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > * small page also write protected so it does not seems useful > * to invalidate secondary mmu at this time. > */ > - return __split_huge_zero_page_pmd(vma, haddr, pmd); > + __split_huge_zero_page_pmd(vma, haddr, pmd); > + return ret; > } > > if (pmd_is_migration_entry(*pmd)) { > @@ -3309,6 +3310,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > VM_WARN_ON(!pte_none(ptep_get(pte + i))); > set_pte_at(mm, addr, pte + i, entry); > } > + ret = true; > } else if (pmd_is_device_private_entry(old_pmd)) { > pte_t entry; > swp_entry_t swp_entry; > @@ -3366,14 +3368,17 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > > smp_wmb(); /* make pte visible before pmd */ > pmd_populate(mm, pmd, pgtable); > + return ret; > } > > -void split_huge_pmd_locked(struct vm_area_struct *vma, unsigned long address, > +bool split_huge_pmd_locked(struct vm_area_struct *vma, unsigned long address, > pmd_t *pmd, bool freeze) > { > VM_WARN_ON_ONCE(!IS_ALIGNED(address, HPAGE_PMD_SIZE)); > if (pmd_trans_huge(*pmd) || pmd_is_valid_softleaf(*pmd)) > - __split_huge_pmd_locked(vma, pmd, address, freeze); > + return __split_huge_pmd_locked(vma, pmd, address, freeze); > + else > + return false; No need for the "else". > } > > void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, > diff --git a/mm/rmap.c b/mm/rmap.c > index 78b7fb5f367c..91fb495bebbe 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -2464,13 +2464,18 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, > > if (flags & TTU_SPLIT_HUGE_PMD) { > /* > - * split_huge_pmd_locked() might leave the > + * If split_huge_pmd_locked() does split PMD > + * to migration entry, we are done. > + * If split_huge_pmd_locked() leave the > * folio mapped through PTEs. Retry the walk > * so we can detect this scenario and properly > * abort the walk. Couldn't we just abort right away, based on the return value? -- Cheers, David