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 49069C982D7 for ; Fri, 18 Sep 2026 22:10:23 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2D9176B0088; Fri, 18 Sep 2026 18:10:22 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 28A506B008A; Fri, 18 Sep 2026 18:10:22 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 153736B008C; Fri, 18 Sep 2026 18:10:22 -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 D31DC6B0088 for ; Fri, 18 Sep 2026 18:10:21 -0400 (EDT) Received: from smtpin30.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 113C280111 for ; Fri, 18 Sep 2026 22:10:21 +0000 (UTC) X-FDA: 85228277442.30.6E221F6 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf18.hostedemail.com (Postfix) with ESMTP id 298A71C000F for ; Fri, 18 Sep 2026 22:10:19 +0000 (UTC) Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=jE261qTp; spf=pass (imf18.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=1789769419; 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=W1TtV+41yhkTzs4bJ6Xi6VeMZvDli7BH7XL9fWmfv8U=; b=PsbIYAQxJ8D0XS8UJzfomjGDGkU/xZZ/PtLrg1ydk6cBOeoJO4dZvPIDritah+Bi8Uk2RG efvggOh/q/CI8rVtS9Faei5grad+KDyUe1vVQG81jZjflUqt+TrX2Q1KLokbp/LMUI88Oz 0Vlw+lzdBDSuXjAwScLF4p8aibgFdgg= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1789769419; b=ZPlZEg8A0Y705qrdbtaDdm9OajoTezTlTmp1ZEn5Z6nHdomKGZCkwIa4w97/uXYZEqdlVg I1PvFSsIh6AJuJsxMfBziKGB0GKjIN8eXWKyXcJ7r0YKUV6Js4GgzEBLYjX5X+3klBdgJ0 P5F36yFYEgQwiYzaXklinT5PZFZZZlg= ARC-Authentication-Results: i=1; imf18.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=jE261qTp; spf=pass (imf18.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 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 827B842E39; Fri, 18 Sep 2026 22:10:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A91F41F000FF; Fri, 18 Sep 2026 22:10:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789769417; bh=W1TtV+41yhkTzs4bJ6Xi6VeMZvDli7BH7XL9fWmfv8U=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=jE261qTp9wo1hjbhahG2879J1uBhEcvBx47yxsLOlwm6VaOtfYsQ5MV3uY2CoRazE ojo50Ej/0w+4dlMHzFgOuNTkfXQEmian3zp6SlfsrRnRvpvzqFmMnm1ZSDKwint7H/ azZKJ/20JDiCZaWIzfk3tmLjXfFz4BidDp5uhazO+p+4NGst6W5pnXEp+4s7dma+3M 3NYnQNdoUzlX6hfH9FHL8f35r1NIcJXvifSwlPf5Fx9DbrSkoWSVvNrn86rwtM7tNH rPYDxUP6gP0duKsHc0Wm77dmJQC36e7YgVa3uC91IawW8fybdXbCBFPz3HAxVvI9Aj jqUwA4HBOFLCw== Message-ID: <35f36d8b-d215-439c-8e77-3a70deed7609@kernel.org> Date: Sat, 19 Sep 2026 00:10:06 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RESEND v7 10/29] mm: make PMD migration-entry splitting explicit 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> <20260914122950.3283997-11-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: <20260914122950.3283997-11-usama.arif@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 298A71C000F X-Stat-Signature: tcih95myewqp7h1he5mit7img7m36dxw X-Rspam-User: X-HE-Tag: 1789769419-682039 X-HE-Meta: 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 IsQ+RNm/ P0vJVJ7moqwBFw/EQpcX3CSK1F4CAIp8MXOZDrUV7B8Y9IimkRFJhcg8z0W/K78j7d7dtxysELqkwOcZl4BXwHgDMgSrwRkiHL/hOQVdZtyTY8byUL2HemUYMqWpV5blyejn1s5fhPgFWizUYeVekK5amxu65GWIZ+YHKFTOgzRM4k6oSlpVkKlsSrjm21LauLPpP4vEWQuC3t+soXmz/q+HNCO6txUGHxqs+jQo+qzPEtFxHLoD+7lMcDdB8caHGDx3F9D75T7CDj2DpQT8c2uc2Ye4QjaXkNqfJ Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/14/26 14:28, Usama Arif wrote: > __split_huge_pmd() and friends take a "freeze" boolean that every caller > has to pass and almost every caller passes as false. The name says nothing > about what it selects, and the one thing it does select - PTE migration > entries instead of PTE mappings - is only ever wanted by the rmap migration > path. > > Rename it to use_migration_entries, keep it private to mm/huge_memory.c, > and add split_pmd_to_migration_entries() for try_to_migrate_one(), the only > caller that wants it. > > migrate_vma_split_unmapped_folio() also passed freeze=true, but only ever > runs on a PMD that is already a migration entry, which the generic helper > expands into PTE migration entries either way. Its folio_get() only existed > to balance the put_page() that freeze=true performs, so both go. > > No functional change intended. > > Suggested-by: David Hildenbrand (Arm) > Signed-off-by: Usama Arif [...] > +void split_pmd_to_migration_entries(struct vm_area_struct *vma, > + unsigned long address, pmd_t *pmd); Two tele tabbies please. > bool unmap_huge_pmd_locked(struct vm_area_struct *vma, unsigned long addr, > pmd_t *pmdp, struct folio *folio); > void map_anon_folio_pmd_nopf(struct folio *folio, pmd_t *pmd, > @@ -690,12 +690,14 @@ static inline void deferred_split_folio(struct folio *folio, bool partially_mapp > do { } while (0) > > static inline void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, > - unsigned long address, bool freeze) {} > + unsigned long address) {} > static inline void split_huge_pmd_address(struct vm_area_struct *vma, > - unsigned long address, bool freeze) {} > + unsigned long address) {} > static inline void split_huge_pmd_locked(struct vm_area_struct *vma, > - unsigned long address, pmd_t *pmd, > - bool freeze) {} > + unsigned long address, pmd_t *pmd) {} > +static inline void > +split_pmd_to_migration_entries(struct vm_area_struct *vma, > + unsigned long address, pmd_t *pmd) {} Dito. > > 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 ee8d46827ffdc..873887aed0bc2 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -2033,7 +2033,7 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, > pte_free(dst_mm, pgtable); > spin_unlock(src_ptl); > spin_unlock(dst_ptl); > - __split_huge_pmd(src_vma, src_pmd, addr, false); > + __split_huge_pmd(src_vma, src_pmd, addr); > return -EAGAIN; > } > add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); > @@ -2257,7 +2257,7 @@ vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf) > folio_unlock(folio); > spin_unlock(vmf->ptl); > fallback: > - __split_huge_pmd(vma, vmf->pmd, vmf->address, false); > + __split_huge_pmd(vma, vmf->pmd, vmf->address); > return VM_FAULT_FALLBACK; > } > > @@ -3190,7 +3190,7 @@ static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, > } > > static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > - unsigned long haddr, bool freeze) > + unsigned long haddr, bool use_migration_entries) Just curious: s/use_migration_entries/to_migration_entries/ > { > struct mm_struct *mm = vma->vm_mm; > struct folio *folio; > @@ -3291,10 +3291,10 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > * folios w.r.t anon exclusive handling. See the comments for > * folio handling and anon_exclusive below. > */ > - if (freeze && anon_exclusive && > + if (use_migration_entries && anon_exclusive && > folio_try_share_anon_rmap_pmd(folio, page)) > - freeze = false; > - if (!freeze) { > + use_migration_entries = false; > + if (!use_migration_entries) { > rmap_t rmap_flags = RMAP_NONE; > > folio_ref_add(folio, HPAGE_PMD_NR - 1); > @@ -3344,11 +3344,11 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio); > > /* > - * Without "freeze", we'll simply split the PMD, propagating the > - * PageAnonExclusive() flag for each PTE by setting it for > + * Without migration entries, we'll simply split the PMD and "When not splitting to migration entries .." > + * propagate the PageAnonExclusive() flag for each PTE by setting it for > * each subpage -- no need to (temporarily) clear. While at it: s/subpage/page/ > * > - * With "freeze" we want to replace mapped pages by > + * With migration entries we want to replace mapped pages by "When splitting to migration entries ..." > * migration entries right away. This is only possible if we > * managed to clear PageAnonExclusive() -- see > * set_pmd_migration_entry(). > @@ -3359,10 +3359,10 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > * See folio_try_share_anon_rmap_pmd(): invalidate PMD first. > */ > anon_exclusive = PageAnonExclusive(page); > - if (freeze && anon_exclusive && > + if (use_migration_entries && anon_exclusive && > folio_try_share_anon_rmap_pmd(folio, page)) > - freeze = false; > - if (!freeze) { > + use_migration_entries = false; > + if (!use_migration_entries) { > rmap_t rmap_flags = RMAP_NONE; > [...] > > smp_wmb(); /* make pte visible before pmd */ > @@ -3477,15 +3477,28 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > } > > void split_huge_pmd_locked(struct vm_area_struct *vma, unsigned long address, > - pmd_t *pmd, bool freeze) > + pmd_t *pmd) While at it ... > { > 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); > + __split_huge_pmd_locked(vma, pmd, address, false); > +} > + > +/* > + * Split a present PMD into PTE migration entries, for the rmap migration > + * walker. Like split_huge_pmd_locked(), the caller must hold the PMD lock and > + * must already be inside an mmu_notifier invalidate range. > + */ I'd prefer kerneldoc but I'll let you decide. > +void split_pmd_to_migration_entries(struct vm_area_struct *vma, > + unsigned long address, pmd_t *pmd) two tabs ... [...] > --- a/mm/migrate_device.c > +++ b/mm/migrate_device.c > @@ -918,12 +918,7 @@ static int migrate_vma_split_unmapped_folio(struct migrate_vma *migrate, > unsigned long flags; > int ret = 0; > > - /* > - * take a reference, since split_huge_pmd_address() with freeze = true > - * drops a reference at the end. > - */ > - folio_get(folio); > - split_huge_pmd_address(migrate->vma, addr, true); > + split_huge_pmd_address(migrate->vma, addr); Everything up to this point was trivial :) You say that it already is unmapped (which makes sense looking at the function name). In VM_WARN_ON_ONCE_FOLIO(folio_mapped(folio), folio) we verify. Did you run the hmm selftests with DEBUG_VM enabled, just to be sure? I remember they exercise at least some of the THP logic in here. > ret = folio_split_unmapped(folio, 0); > if (ret) > return ret; > diff --git a/mm/mprotect.c b/mm/mprotect.c > index 2888ee638d872..ee33bbb421008 100644 > --- a/mm/mprotect.c > +++ b/mm/mprotect.c > @@ -530,7 +530,7 @@ static inline long change_pmd_range(struct mmu_gather *tlb, > if (pmd_is_huge(_pmd)) { > if ((next - addr != HPAGE_PMD_SIZE) || > pgtable_split_needed(vma, cp_flags)) { > - __split_huge_pmd(vma, pmd, addr, false); > + __split_huge_pmd(vma, pmd, addr); > /* > * For file-backed, the pmd could have been > * cleared; make sure pmd populated if > diff --git a/mm/rmap.c b/mm/rmap.c > index 5332c52909be1..feb751e29b992 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -2290,7 +2290,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, > * restart so we can process the PTE-mapped THP. > */ > split_huge_pmd_locked(vma, pvmw.address, > - pvmw.pmd, false); > + pvmw.pmd); You can feel brave and squeeze it into a single line now :) Overall LGTM. -- Cheers, David