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]) by smtp.lore.kernel.org (Postfix) with ESMTP id 102C2C2BBCA for ; Tue, 25 Jun 2024 20:02:03 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A0E666B0096; Tue, 25 Jun 2024 16:02:02 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9BF0F6B00B4; Tue, 25 Jun 2024 16:02:02 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7C25D6B00B6; Tue, 25 Jun 2024 16:02:02 -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 D7A9F6B0096 for ; Tue, 25 Jun 2024 16:02:01 -0400 (EDT) Received: from smtpin11.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 824D31204B4 for ; Tue, 25 Jun 2024 20:02:01 +0000 (UTC) X-FDA: 82270482042.11.D73DA5C Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf01.hostedemail.com (Postfix) with ESMTP id 1974740027 for ; Tue, 25 Jun 2024 20:01:58 +0000 (UTC) Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=FEAXgt+C; spf=pass (imf01.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1719345704; 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=IuAUeZx0tw8RngIE0GabU2dfwuqpvSQebG3NOHqSKZs=; b=fyxtc1RcQOrWzGl+JN/3MAjxekY9YOj8vYUh1cOa8AzVzsW3Acu6uC+yn8vZ6SBYwFCaFB wA9M3S/g4hMNEmljrNg8uw61Vbs4B3XEXsuRvJxM4JMEcFBRjc8dHBMG4inCIFl8alCun2 cx9hs3886BhYfIqPQl+OSN18/ICV/5s= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1719345704; a=rsa-sha256; cv=none; b=5t8i3WSyfiyTn3eMTM9y3sYBy5+VcGBHtNvWf2kDU4LBkqdGIMIIqE6Z1uXRJ7uGI6F9dw vTvWKJqPxtqiZGLke+ElathUOrYhi5g2f4DFVZprKLDYbTTeQouBtCB+mlFa3vdvDIVkPL sTir++muaJ9/LEKnSFpX6uRFvjehMVg= ARC-Authentication-Results: i=1; imf01.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=FEAXgt+C; spf=pass (imf01.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1719345718; h=from:from: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:autocrypt:autocrypt; bh=IuAUeZx0tw8RngIE0GabU2dfwuqpvSQebG3NOHqSKZs=; b=FEAXgt+CPH9ikzdLvXgZiQA9z/LmURckJc4vlGjEPo1N9kX9T2yE0BtRKDq34b4tyemsrj YeYVRmelt4PzzRH5VFK5B1wvivnF1A/LnFXzk5XS2SqGUn0v5UR5kA4kDN3u3qbwelBgxx syQ44vqi9KIjJvNXZ5UxnFVLsSbQC+4= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-311-q9IloccsM-CTX11MVSkuKg-1; Tue, 25 Jun 2024 16:01:55 -0400 X-MC-Unique: q9IloccsM-CTX11MVSkuKg-1 Received: by mail-wm1-f69.google.com with SMTP id 5b1f17b1804b1-421e17ae038so41313595e9.0 for ; Tue, 25 Jun 2024 13:01:54 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1719345714; x=1719950514; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:from:references:cc:to:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=IuAUeZx0tw8RngIE0GabU2dfwuqpvSQebG3NOHqSKZs=; b=M65YCEM2W9Y8Ke+tYg16l+3pZYv8PUGwNhNXyCe4amHqMDsgf7sgqKgw3YhMkpjoV5 FnMsCxSktWVW+XWUYMCdn8s+YgM5/QV0tq0CWl6kkRQlY0yYteMRPArpFzD+zYQfboUd 9mItKWwaZQ6HcgLdQ5jldKgHT4j+45uijKsnoIBosYvwBVUUgggd28FPSTzWAsYIrxBs Co/fbFVcUDUtpuNBZDkc+b2aVXcLls9iRuTUqW0BD1cLHLFuTyvE1bqvTfN9XwOrkt4H sCLJQq27Q+r4lMC0qMhpxwIHeV2Yu/UJJRzx5uSFJ5Mkz//S/N0xBzyUBoDWoAu4xG6d C3cQ== X-Forwarded-Encrypted: i=1; AJvYcCWbpR8wgclSnTraM5RzvabkcMEkiTP5Se20MxgRDqOdwSCmg9hYdEEE6w+Ird7U/4529Td1nph6UKH13LrUFsVKX4c= X-Gm-Message-State: AOJu0YzCiBfAxCakXWNP6BZuWPdiEAGa00fw4Bf7kpOSNQRbYAOaxZ2h gNOIGDGRziXOz4wwrSiLVBONirdlPlexqZaVOgnkeXh8ZDWlP5hfaIS7Ax75GHJjOHnBiMhnbKN 7f5vJu7xAnebRl/+Q1dYx5eJdjDaZTzkrxkqdwfFZdhul0uU4 X-Received: by 2002:a5d:6c68:0:b0:366:eade:bfbb with SMTP id ffacd0b85a97d-366eadec057mr6163714f8f.46.1719345713954; Tue, 25 Jun 2024 13:01:53 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEN7PqcufF9NDNRFSVfEmTSOfKjOq1maVH44H1bT9B7oLktcBYl4mXhxBS4nLRa0Y4N3T731A== X-Received: by 2002:a5d:6c68:0:b0:366:eade:bfbb with SMTP id ffacd0b85a97d-366eadec057mr6163688f8f.46.1719345713426; Tue, 25 Jun 2024 13:01:53 -0700 (PDT) Received: from [192.168.1.34] (p548825e3.dip0.t-ipconnect.de. [84.136.37.227]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-366389b85cesm14114523f8f.46.2024.06.25.13.01.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 25 Jun 2024 13:01:53 -0700 (PDT) Message-ID: Date: Tue, 25 Jun 2024 22:01:51 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH mm-unstable] mm: migrate: folio_ref_freeze() under xas_lock_irq() To: Hugh Dickins , Andrew Morton Cc: Kefeng Wang , linux-mm@kvack.org, Tony Luck , Miaohe Lin , nao.horiguchi@gmail.com, Matthew Wilcox , Muchun Song , Benjamin LaHaise , jglisse@redhat.com, Zi Yan , Jiaqi Yan , Vishal Moola , Alistair Popple , Jane Chu , Oscar Salvador References: <07edaae7-ea5d-b6ae-3a10-f611946f9688@google.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <07edaae7-ea5d-b6ae-3a10-f611946f9688@google.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 1974740027 X-Stat-Signature: i71jsmmf8xp6q1fobe6c4uuqt4y31d5u X-HE-Tag: 1719345718-131572 X-HE-Meta: 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 45JSdv1o 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 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 25.06.24 07:04, Hugh Dickins wrote: > Commit "mm: migrate: split folio_migrate_mapping()" drew attention to > "Note, the folio_ref_freeze() is moved out of xas_lock_irq(), Since the > folio is already isolated and locked during migration, so suppose that > there is no functional change." > > That was a mistake. Freezing a folio's refcount to 0 is much like taking > a spinlock: see how filemap_get_entry() takes rcu_read_lock() then spins > around until the folio is unfrozen. If the task freezing is preempted (or > calls cond_resched(), as folio_mc_copy() may do), then it risks deadlock: > in my case, one CPU in zap_pte_range() with free_swap_and_cache_nr() > trying to reclaim swap while PTL is held, all the other CPUs in reclaim > spinning for that PTL. Very much agreed. I think we should add a proper comment to folio_ref_freeze() to spell that out. -- Cheers, David / dhildenb