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 B37D6CF6495 for ; Sat, 28 Sep 2024 08:34:09 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2BC4D6B01A2; Sat, 28 Sep 2024 04:34:09 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 26B366B01A3; Sat, 28 Sep 2024 04:34:09 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0E5A16B01A4; Sat, 28 Sep 2024 04:34:09 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id E59B66B01A2 for ; Sat, 28 Sep 2024 04:34:08 -0400 (EDT) Received: from smtpin04.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 987FC1619BA for ; Sat, 28 Sep 2024 08:34:08 +0000 (UTC) X-FDA: 82613484576.04.2264739 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf17.hostedemail.com (Postfix) with ESMTP id 5727C40008 for ; Sat, 28 Sep 2024 08:34:06 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=GXEvJY3X; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf17.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1727512355; a=rsa-sha256; cv=none; b=bCuHxFcGlPvxasNi7IN3xWeSZWbgCkaAMi1UDuSsaMqPPDJ8OhaBR+8ztmi3lRCnqXeYh/ VJR+tAa/Q1bzwUuFY9KzAQdEaAx+wmlbFCNbJ9mOq4HTa+DLRcLMKiecBvFh/PVDcN5HUl vRY2qDhgcINsPAE7D4EzoPSJi0dMWbQ= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=GXEvJY3X; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf17.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1727512355; 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=Uujt+C8bZS9gkUB6BLUw4zZvdel2da2WL/+BBNWpHS0=; b=QbARDUAZ87lUl/VSDKnNEZpLFU2PDwPgfmZhjYgPW8U+fKemPRo04RWXJ82b5Wdr6lUTbg LJLZ7a8/WHczN612SOkLZmZw36ysQlKHNqSbxG6NNvdJR23thjG+rID9wHUs46EdEtrCXS RDIlB5EjxFvZqMd/Uls0HqeieJhKdyg= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1727512445; 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=Uujt+C8bZS9gkUB6BLUw4zZvdel2da2WL/+BBNWpHS0=; b=GXEvJY3XMBeQeA7OqCEd/NURTXj3z4E05RuChQuahG9PEin0m6nszqEQDL8NCqon69K85y pzWhideId4ZxeMnxvDv5uu59cVo+dFmBH/0kz5Hj+DcV2pQhJOwoO32tMwLLnCAxFhpI/r GNEm2dhj3D6Jj+jrhPrqWBPtTE+UZ0w= Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-645-_W6tXjOAN4m197BU7JGAHg-1; Sat, 28 Sep 2024 04:34:04 -0400 X-MC-Unique: _W6tXjOAN4m197BU7JGAHg-1 Received: by mail-wm1-f72.google.com with SMTP id 5b1f17b1804b1-42cb374f0cdso15421245e9.0 for ; Sat, 28 Sep 2024 01:34:03 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1727512443; x=1728117243; h=content-transfer-encoding:in-reply-to:organization:autocrypt:from :content-language: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=Uujt+C8bZS9gkUB6BLUw4zZvdel2da2WL/+BBNWpHS0=; b=lfoopNS0/M3A9KUt2GCX1Augpo83oB94KrhxtKnqz5CBMaiD1nitpcW3lUti/DREGF /Hx07tANQTEb8BB1dfhK0gdHnYXnpIQ2wO7JpUfw79CWg9FL+D+YAdxpwOyGpBbuRQVM NJFpK8+MweauNkb/RMmSble5nzZ+/Fe/USTZDKBKNS3Fr7JXtBa+Lu1h/u49/jJ045pz 4avJpwk4FJRsCbWhVifT4sc94pdpemfeamEL2YMvaztOFkp6ihfFuNAG1dn+QXeoLwCF 95NyJ6bQ44sckPwvamDFdRoQhaJW69o+ik6GtyySX6vAZRn3T9SdQF/zv38RAfxG8wEz nJIw== X-Forwarded-Encrypted: i=1; AJvYcCWeWtCoP2erxQ8wVGvvTciwd4q6Kc+6OAAIjRSDpthxFXsXhFEyW43ggDFP2x0tGgADLIO1yn1gXQ==@kvack.org X-Gm-Message-State: AOJu0YwoZaf/B4hnl8MnIOaxUK8bnI+VckDqYI/2KGjhc/CaGaTKC6Tb YPMwLdX5Dotr5uu3k5jfa08piV2NgKFgtQn0BaxYTwK7TG8kjcAklmkVTspb6MaYiYDArobkLmY 6sz3LEMO+SjTw7O/rTIc8t9bq2twMnPHhPGveNpTwHRMf+K/1 X-Received: by 2002:a05:600c:1389:b0:424:a7f1:ba2 with SMTP id 5b1f17b1804b1-42f522089a3mr53212425e9.17.1727512442889; Sat, 28 Sep 2024 01:34:02 -0700 (PDT) X-Google-Smtp-Source: AGHT+IH8O1GvyW5zq5u8OuQaQOTgEpaMPO3SBpF0WJDup/GQ7WGql46LftVZIbJhcfdzjBU6ZiruGA== X-Received: by 2002:a05:600c:1389:b0:424:a7f1:ba2 with SMTP id 5b1f17b1804b1-42f522089a3mr53212295e9.17.1727512442518; Sat, 28 Sep 2024 01:34:02 -0700 (PDT) Received: from [192.168.3.141] (p4ff2399b.dip0.t-ipconnect.de. [79.242.57.155]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-42f57de11aasm47375875e9.16.2024.09.28.01.34.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 28 Sep 2024 01:34:02 -0700 (PDT) Message-ID: <20a75b57-12a6-468f-bd7c-0aeb2f259228@redhat.com> Date: Sat, 28 Sep 2024 10:34:01 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/5] mm: memory_hotplug: remove head variable in do_migrate_range() To: Matthew Wilcox , Kefeng Wang Cc: Andrew Morton , Oscar Salvador , Miaohe Lin , Naoya Horiguchi , linux-mm@kvack.org, dan.carpenter@linaro.org, Jonathan Cameron References: <20240827114728.3212578-1-wangkefeng.wang@huawei.com> <20240827114728.3212578-2-wangkefeng.wang@huawei.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: 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-Rspamd-Queue-Id: 5727C40008 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: 9q4huj8mo3wifuu3m5hxzz7ga3s6nqnr X-HE-Tag: 1727512446-821540 X-HE-Meta: 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 aV98BPOm 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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 28.09.24 06:55, Matthew Wilcox wrote: > On Tue, Aug 27, 2024 at 07:47:24PM +0800, Kefeng Wang wrote: >> Directly use a folio for HugeTLB and THP when calculate the next pfn, then >> remove unused head variable. > > I just noticed this got merged. You're going to hit BUG_ON with it. > >> - if (PageHuge(page)) { >> - pfn = page_to_pfn(head) + compound_nr(head) - 1; >> - isolate_hugetlb(folio, &source); >> - continue; >> - } else if (PageTransHuge(page)) >> - pfn = page_to_pfn(head) + thp_nr_pages(page) - 1; >> + /* >> + * No reference or lock is held on the folio, so it might >> + * be modified concurrently (e.g. split). As such, >> + * folio_nr_pages() may read garbage. This is fine as the outer >> + * loop will revisit the split folio later. >> + */ >> + if (folio_test_large(folio)) { > > But it's not fine. Look at the implementation of folio_test_large(): > > static inline bool folio_test_large(const struct folio *folio) > { > return folio_test_head(folio); > } > > That's going to be provided by: > > #define FOLIO_TEST_FLAG(name, page) \ > static __always_inline bool folio_test_##name(const struct folio *folio) \ > { return test_bit(PG_##name, const_folio_flags(folio, page)); } > > and here's the BUG: > > static const unsigned long *const_folio_flags(const struct folio *folio, > unsigned n) > { > const struct page *page = &folio->page; > > VM_BUG_ON_PGFLAGS(PageTail(page), page); > VM_BUG_ON_PGFLAGS(n > 0 && !test_bit(PG_head, &page->flags), page); > return &page[n].flags; > } > > (this page can be transformed from a head page to a tail page because, > as the comment notes, we don't hold a reference. > > Please back this out. Should we generalize the approach in dump_folio() to locally copy a folio, so we can safely perform checks before deciding whether we want to try grabbing a reference on the real folio (if it's still a folio :) )? -- Cheers, David / dhildenb