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 8CEF0FF885D for ; Tue, 28 Apr 2026 08:24:54 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id CC4396B0096; Tue, 28 Apr 2026 04:24:53 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C75516B0099; Tue, 28 Apr 2026 04:24:53 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B64A26B009B; Tue, 28 Apr 2026 04:24:53 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id A1CA16B0096 for ; Tue, 28 Apr 2026 04:24:53 -0400 (EDT) Received: from smtpin17.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 48A0440421 for ; Tue, 28 Apr 2026 08:24:53 +0000 (UTC) X-FDA: 84707278866.17.96D4AD6 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf10.hostedemail.com (Postfix) with ESMTP id 8EAD3C000D for ; Tue, 28 Apr 2026 08:24:51 +0000 (UTC) Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=rq2g6itF; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf10.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1777364691; 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=Kl9plSYya29YBeTxwNBrUzw/z6Exv/Si0DhUaCe5cI8=; b=IgrbyKU+56rH783Uzjh0tCnZPYQxusAzgTXYjOy3WopOudTLRbPUknI/sx2R3MjAuJZlvQ GYwW6c7qhpXdli7UrazsJKa0+9rUtQ9/14Au8ct0K7VgTiTdNXL49KdfPnrBI+lX3GWG4u bscC8/8TGaNBESgvOY21uRUEZ/pOD4k= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1777364691; a=rsa-sha256; cv=none; b=X9p/zZBigLmE+j8IUz9QYuivsEyIVnC38nlkknhdyrrw/sMTifYX4gXvPjkSxmTYam2OyH dMIe1kCcJaEkBtFiSUyIfG6Ec98OIOBjvFS35NwJVpfQfmlf6XVpaesPM2IY1EPzi1HfFg 6Rz0Rq1AiOHO5OEn39F96XUju8WI/NY= ARC-Authentication-Results: i=1; imf10.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=rq2g6itF; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf10.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id EA29060142; Tue, 28 Apr 2026 08:24:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 58C45C2BCAF; Tue, 28 Apr 2026 08:24:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777364690; bh=BuBD+B3KjaLGM+cuwGM0YX6GxNQ9f7gGmlxYjNR9YHU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=rq2g6itFGPzC5B/NbC48GPVPtOm2DxQsOPeqABJmdCwIsyRcQuLqv50l8MEg1gPjz oykmS98fvUsS96ls4vuvf45GMeFTCR+HI9XIl3F4TT+to+GutI+XBk/DKnA2mR81Sm 2qHWdk2ipcoXcmZmPgcPH6grudsHXLMWJAto+I/cJJYlYZcl81Cunf1EwWdVSd//H1 oM7xbbubKjFOz2Jwzo7Q1Rm0ym9KwIaK7dB8hLtuz/QcMqeYIZEH7tgxhX190x2gkD ZFw0OV0FmTYEHhZS5Hu2YqRMMMw46MK71MVbB9I4RaOb0MK2RFuidPjJkHn3xo/dyk GbGtenqhrZZoQ== Message-ID: Date: Tue, 28 Apr 2026 10:24:42 +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 Cc: 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, linux-mm@kvack.org, Gavin Guo References: <20260415010839.20124-1-richard.weiyang@gmail.com> <20260415010839.20124-2-richard.weiyang@gmail.com> <79e164a2-47ce-4a02-82f5-164515760b6d@kernel.org> <20260426091957.a227zxgkqapibtud@master> 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: <20260426091957.a227zxgkqapibtud@master> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 8EAD3C000D X-Stat-Signature: 34hggp9a13rhtxgz9h7drnftj7uhkm5u X-Rspam-User: X-HE-Tag: 1777364691-586071 X-HE-Meta: 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 hrGXiWIc 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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 4/26/26 11:19, Wei Yang wrote: > On Fri, Apr 24, 2026 at 09:29:18PM +0200, David Hildenbrand (Arm) wrote: >> 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? >> > > Will adjust related places. > >>> 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". >> > > Got it. > >>> } >>> >>> 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? >> > > Here is my understanding. > > We get here when page_vma_mapped_walk() touch a pmd entry, with three cases: > > * pmd_trans_huge() > * pmd_is_migration_entry() > * pmd_is_device_private_entry() > > For the first two cases, we grab pmd_lock() and then check the condition is > still valid before return. But for case 3, after grab pmd_lock(), it return > directly. > > This may give chance for another thread to split pmd_is_device_private_entry() > to pte mapped, IIUC. For this case, we should restart the walk here. So what you are saying is that we should re-validate in page_vma_mapped_walk() that we indeed still have a device-private entry after grabbing the lock? That's what we do in map_pte() through pmd_same() check. Likely we should apply the same model here! -- Cheers, David