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 DA3A6C87FD2 for ; Mon, 11 Aug 2025 13:03:46 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 6AA0C8E0050; Mon, 11 Aug 2025 09:03:46 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 681CE8E0045; Mon, 11 Aug 2025 09:03:46 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 571B08E0050; Mon, 11 Aug 2025 09:03:46 -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 447D88E0045 for ; Mon, 11 Aug 2025 09:03:46 -0400 (EDT) Received: from smtpin13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id EF0841A01AF for ; Mon, 11 Aug 2025 13:03:45 +0000 (UTC) X-FDA: 83764493610.13.D35EED0 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf04.hostedemail.com (Postfix) with ESMTP id 63CA740005 for ; Mon, 11 Aug 2025 13:03:43 +0000 (UTC) Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=h0S+5SxM; spf=pass (imf04.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=quarantine) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1754917423; 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=l0BtLxYidZI73LQEwOGP96I9gxCnmhJ4MxHYnaXFggA=; b=cSFFHOtjI+Q9FlVbYffGcpByS5VePL2RwSPMhno7zL+C/pdAKqMXcsQ6oMgNBDLBfqT+po S6u9OVRHlTBr4SEOoN2aOn2NLoUKU2RU0tN9wKWYIPWwgH80LaW5bp1+Di8IpLb0Z6rqxJ ZxpKjrv6pz6Ts+v62Eymh0jkofnGD+I= ARC-Authentication-Results: i=1; imf04.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=h0S+5SxM; spf=pass (imf04.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=quarantine) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1754917423; a=rsa-sha256; cv=none; b=2gCw0RBnMWLh2qxrgoh0gIZxKkVAHxdm+CpvY/FNM/03p/0E90TyJs9ZOXd7KZOzN1k21H Zu76ilF2P93zRnb6fFgDiLQlv0YF5E6ubkA41cJnLvymUdNXLYjgMqoXVaA9E8Dyvr/rXq DX3PX1UIUo038hIF36TBQIE8hghPuAw= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1754917422; 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=l0BtLxYidZI73LQEwOGP96I9gxCnmhJ4MxHYnaXFggA=; b=h0S+5SxMcKloA6D87PY0YC8cKjxKQNnDkGqWMCmi4LLWwij7JTHLqrAT/xKwmHlGx0VeFh sBlN0kG/A29DiOg7CiLm2J08wg0u3Mhf5qGNv7QLQG16qWJQzd6DG/foSF0jnDb0Kr77fe q0Be5imIFaDFehWZ5lkVkngf9KBD+no= 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-370-X_cs-xwfMsum91ElKQ7bMg-1; Mon, 11 Aug 2025 09:03:41 -0400 X-MC-Unique: X_cs-xwfMsum91ElKQ7bMg-1 X-Mimecast-MFC-AGG-ID: X_cs-xwfMsum91ElKQ7bMg_1754917419 Received: by mail-wm1-f72.google.com with SMTP id 5b1f17b1804b1-459d8020b7bso22037675e9.3 for ; Mon, 11 Aug 2025 06:03:40 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1754917419; x=1755522219; 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=l0BtLxYidZI73LQEwOGP96I9gxCnmhJ4MxHYnaXFggA=; b=MC7/9TQTkum5UFRnc7RYdKVP7JFNCw2zam92SxQc2UQY688MWtM6v0cxpB9jzamiiu eBykZdR3Gzm85fv3CPDuG5aVT0ruxnAUUD4T0hLIwQw1ssWw95Mb2GobWHJmQy6/6Sf7 4HNgD9kQWsjKXCPXBjJQwCFopM/N/UiXPivdBAbYnIDl1Hlu48ZkGf64CifpCEXmUOmr SThM7/ocrqkIZKifMhJ838+ZpUqg36LEOpADmCLUTyukPkrxpVmKsFxCtAogOhSc78/y EADVdER02el1tGPGNHYOLZwRl6mvrXaHsOh4BNz99gEHrFrX+D5RDWzyMKfYjtLXJrk+ Qu0A== X-Forwarded-Encrypted: i=1; AJvYcCVEQYa4qnoJ7z3qUd0ENzqyp2WznJ5cnZOjTBqnj6nbp0F2SJdUq3qTzAobjKOZ0IjO/yn9SnJSew==@kvack.org X-Gm-Message-State: AOJu0Yw8ENEAas3j5qpUNZ9mOUZoQxVxyK2aOF5aBhhYfXghvlmPYPhU Hn0iGFOlG0qUXb7Y6oxbnqdHYlvKgohBgzwNSkN3EDls/LhFqU+7pZapLpTxKRFd5F17EoXnUPU T206ZYbzkQoCZ9V62VIxDqm5AXVGI1lHF+zhMbTlOCX1HNKTMAzzf X-Gm-Gg: ASbGncuwFh1Ykv31yz/zZrYXUerCmhHfIuNCD49tPAvtHPzBTSDDwAIVisHkt4FAebE Sn1e9VfXDSRfBw3gAH6ISxZGNuXOA9I1uL9Ji0Hkqh7DbqF5DmBL5riRjesVxaWr1l2HmCDmDR5 OEmUkPhH6EaDvYiOLgeTlI8DKKtN4Cqsii1XrtcRj8PGbBFnOiDTuZQOttQf/g0HOMyr9f366pZ WlMtRbyJAhbG5k0cEexzBocrYB1J4mqvhHMvr5sKMTYJmqvW9xlvMiEDStXAD0Z2D9tiXlG/RFj SZXDuLTeEhh0cHvsCYU1s4kWI8qlbuvxEMFdSEIVMyFYL68C/gcnOGnlv38QgwLCLgPwYFGZvTg JwsqRJKu6Bvv8tFEzTLJnl+g8zReqNuQ79wmQ1TVHrdCDnbZBMeCsR6VsDpX8YBO7ZZs= X-Received: by 2002:a05:600c:310e:b0:458:6733:fb43 with SMTP id 5b1f17b1804b1-459f4f0f5c2mr117242565e9.19.1754917419076; Mon, 11 Aug 2025 06:03:39 -0700 (PDT) X-Google-Smtp-Source: AGHT+IH1mfWN2Xjl9R7zfCFKVnCaGu1ndRRL4tr/HVjclyc3vwPmExqtNC2qIKBRYzk0XdbpTd8QiQ== X-Received: by 2002:a05:600c:310e:b0:458:6733:fb43 with SMTP id 5b1f17b1804b1-459f4f0f5c2mr117242125e9.19.1754917418610; Mon, 11 Aug 2025 06:03:38 -0700 (PDT) Received: from ?IPV6:2003:d8:2f06:a600:a397:de1d:2f8b:b66f? (p200300d82f06a600a397de1d2f8bb66f.dip0.t-ipconnect.de. [2003:d8:2f06:a600:a397:de1d:2f8b:b66f]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-459e0cd2c90sm302174235e9.17.2025.08.11.06.03.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 11 Aug 2025 06:03:38 -0700 (PDT) Message-ID: <9178bf98-2ea7-4ad8-ad43-cdcc02ab863d@redhat.com> Date: Mon, 11 Aug 2025 15:03:36 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: swap: check for xa_zero_entry() on vma in swapoff path To: Lorenzo Stoakes , Charan Teja Kalla Cc: akpm@linux-foundation.org, shikemeng@huaweicloud.com, kasong@tencent.com, nphamcs@gmail.com, bhe@redhat.com, baohua@kernel.org, chrisl@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Liam R. Howlett" , Matthew Wilcox References: <20250808092156.1918973-1-quic_charante@quicinc.com> <29e080fd-5f9a-4760-876a-a6ccef33129f@quicinc.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/g1oFAmgsLPQFCRvGjuMACgkQTd4Q 9wD/g1o0bxAAqYC7gTyGj5rZwvy1VesF6YoQncH0yI79lvXUYOX+Nngko4v4dTlOQvrd/vhb 02e9FtpA1CxgwdgIPFKIuXvdSyXAp0xXuIuRPQYbgNriQFkaBlHe9mSf8O09J3SCVa/5ezKM OLW/OONSV/Fr2VI1wxAYj3/Rb+U6rpzqIQ3Uh/5Rjmla6pTl7Z9/o1zKlVOX1SxVGSrlXhqt kwdbjdj/csSzoAbUF/duDuhyEl11/xStm/lBMzVuf3ZhV5SSgLAflLBo4l6mR5RolpPv5wad GpYS/hm7HsmEA0PBAPNb5DvZQ7vNaX23FlgylSXyv72UVsObHsu6pT4sfoxvJ5nJxvzGi69U s1uryvlAfS6E+D5ULrV35taTwSpcBAh0/RqRbV0mTc57vvAoXofBDcs3Z30IReFS34QSpjvl Hxbe7itHGuuhEVM1qmq2U72ezOQ7MzADbwCtn+yGeISQqeFn9QMAZVAkXsc9Wp0SW/WQKb76 FkSRalBZcc2vXM0VqhFVzTb6iNqYXqVKyuPKwhBunhTt6XnIfhpRgqveCPNIasSX05VQR6/a OBHZX3seTikp7A1z9iZIsdtJxB88dGkpeMj6qJ5RLzUsPUVPodEcz1B5aTEbYK6428H8MeLq NFPwmknOlDzQNC6RND8Ez7YEhzqvw7263MojcmmPcLelYbfOwU0EVcufkQEQAOfX3n0g0fZz 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+DWgUCaCwtJQUJG8aPFAAKCRBN3hD3AP+DWlDnD/4k2TW+HyOOOePVm23F5HOhNNd7nNv3 Vq2cLcW1DteHUdxMO0X+zqrKDHI5hgnE/E2QH9jyV8mB8l/ndElobciaJcbl1cM43vVzPIWn 01vW62oxUNtEvzLLxGLPTrnMxWdZgxr7ACCWKUnMGE2E8eca0cT2pnIJoQRz242xqe/nYxBB /BAK+dsxHIfcQzl88G83oaO7vb7s/cWMYRKOg+WIgp0MJ8DO2IU5JmUtyJB+V3YzzM4cMic3 bNn8nHjTWw/9+QQ5vg3TXHZ5XMu9mtfw2La3bHJ6AybL0DvEkdGxk6YHqJVEukciLMWDWqQQ RtbBhqcprgUxipNvdn9KwNpGciM+hNtM9kf9gt0fjv79l/FiSw6KbCPX9b636GzgNy0Ev2UV m00EtcpRXXMlEpbP4V947ufWVK2Mz7RFUfU4+ETDd1scMQDHzrXItryHLZWhopPI4Z+ps0rB CQHfSpl+wG4XbJJu1D8/Ww3FsO42TMFrNr2/cmqwuUZ0a0uxrpkNYrsGjkEu7a+9MheyTzcm vyU2knz5/stkTN2LKz5REqOe24oRnypjpAfaoxRYXs+F8wml519InWlwCra49IUSxD1hXPxO WBe5lqcozu9LpNDH/brVSzHCSb7vjNGvvSVESDuoiHK8gNlf0v+epy5WYd7CGAgODPvDShGN g3eXuA== Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: IxdhMq9TAbD9WNURH9q4OglTd71N1ag0iSRlHJPhUX4_1754917419 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 63CA740005 X-Rspamd-Server: rspam04 X-Rspam-User: X-Stat-Signature: rwkxgdabd6wshjzzhtbkz6it6atc63pp X-HE-Tag: 1754917423-101403 X-HE-Meta: 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 vWrM/yE1 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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 11.08.25 14:14, Lorenzo Stoakes wrote: > On Mon, Aug 11, 2025 at 03:13:14PM +0530, Charan Teja Kalla wrote: >> Thanks David, for the reply!! >> On 8/8/2025 5:34 PM, David Hildenbrand wrote: >>>>         if (mpnt) { >>>>             mas_set_range(&vmi.mas, mpnt->vm_start, mpnt->vm_end - 1); >>>>             mas_store(&vmi.mas, XA_ZERO_ENTRY); >>>>             /* Avoid OOM iterating a broken tree */ >>>>             set_bit(MMF_OOM_SKIP, &mm->flags); >>>>         } >>>>         /* >>>>          * The mm_struct is going to exit, but the locks will be dropped >>>>          * first.  Set the mm_struct as unstable is advisable as it is >>>>          * not fully initialised. >>>>          */ >>>>         set_bit(MMF_UNSTABLE, &mm->flags); >>>>     } >>>> >>>> Shouldn't we just remove anything from the tree here that was not copied >>>> immediately? >>> >>> Another fix would be to just check MMF_UNSTABLE in unuse_mm(). But >>> having these MMF_UNSTABLE checks all over the place feels a bit like >>> whack-a-mole. >>> >> Seems MMF_UNSTABLE is the expectation per the commit, >> 64c37e134b12("kernel: be more careful about dup_mmap() failures and >> uprobe registering"). Excerpt(s) from the commit message: > > This really is whack-a-mole yeah. > >> >> This patch sets the MMF_OOM_SKIP to avoid the iteration of the vmas on >> the oom side (even though this is extremely unlikely to be selected as >> an oom victim in the race window), and __sets MMF_UNSTABLE to avoid >> other potential users from using a partially initialised mm_struct. >> > > But... maybe this is better for the _hotfix_ version as a nicer way of > doing this. I would prefer using MMF_UNSTABLE as a hotfix. > >> When registering vmas for uprobe, skip the vmas in an mm that is marked >> unstable. Modifying a vma in an unstable mm may cause issues if the mm >> isn't fully initialised.__ >> >>> Is there anything preventing us from just leaving a proper tree that >>> reflects reality in place before we drop the write lock? >> >> When you mean proper tree, is this about the your previous question? -- >> Shouldn't we just remove anything from the tree here that was not copied >> immediately? > > Commit d24062914837 (" fork: use __mt_dup() to duplicate maple tree in > dup_mmap()") did this for efficiency, so it'd be a regression to do this. We're talking about the case where fork *fails*. That cannot possibly be relevant for performance, can it? :) -- Cheers, David / dhildenb