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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C38E0C8302F for ; Tue, 1 Jul 2025 10:19:58 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [127.0.0.1]) by lists.ozlabs.org (Postfix) with ESMTP id 4bWfCx2zfWz307q; Tue, 1 Jul 2025 20:19:57 +1000 (AEST) Authentication-Results: lists.ozlabs.org; arc=none smtp.remote-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1751365197; cv=none; b=lVAiIrG8Vhl8bD5ppwhQ/M1VwSmm4w3w4Fve0qQLINqnEFp4k5XUvTgUcvUTy630jOwKerabZDGv3Zq0Ri8SJyaFSp7d6PQR4zDOTZ50aAIGKq+Dbg21BWn2AcMmLxRxSUjc4BPCyZKIDSg8BBS2IXzFoRC7QS4UewTiXj+1wxLSJKnI7N8lMk6Lp1/7rlKaqP7XABdXpCEehoDXzDReJQh7avcB68fh7mrDGQAZ8z3DXAwd71v3Szu7zT+FxVGBDKrkY/SVMM0gL4xp2vdNmizQMluSG9aqZD6pV8xJhDltYniPpF6o7FhRZD3MBr2mlouXBO2+Mv2Xz+39qbg4aA== ARC-Message-Signature: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1751365197; c=relaxed/relaxed; bh=F4jCtuuDml1rKQTvhcRaw4++6CgpogXopSkG6zuHOew=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=fZpckTczmFEtrsHdnbXpb+Cvdn8Qdk5A6bUoO8LwkyFVvE8HK1iPZ3c/yQl5q7bQ2FqzN3q5J/WExwwDdVljAxvsUkAiXDtCa6ZebWWoZYI/AjemZOSG/zd8acpmpD9UTcDMFQMbcHikU0yoWN5E781okitJd3oQVmzkdjr6qMrvKHb37lRs7lSv1GA2NmhgODpbWYFdenVQ4JZZvF0k73ifP0g4Ziio1Pws6MtSm2RUTC0oH0NEjh2V6eRYj/RbRXtw/webkkU9A/rW9+25IOk/BT3ZiHnfCyz50y3kZJwSfC5sdPmTs9coZe5VaCN9G64oi4rIBAjiuLcwj5xMTA== ARC-Authentication-Results: i=1; lists.ozlabs.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=hP4FIARG; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=H9MkZkfb; dkim-atps=neutral; spf=pass (client-ip=170.10.133.124; helo=us-smtp-delivery-124.mimecast.com; envelope-from=david@redhat.com; receiver=lists.ozlabs.org) smtp.mailfrom=redhat.com Authentication-Results: lists.ozlabs.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=hP4FIARG; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=H9MkZkfb; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=redhat.com (client-ip=170.10.133.124; helo=us-smtp-delivery-124.mimecast.com; envelope-from=david@redhat.com; receiver=lists.ozlabs.org) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4bWfCw3zy1z2xPc for ; Tue, 1 Jul 2025 20:19:56 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1751365193; 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=F4jCtuuDml1rKQTvhcRaw4++6CgpogXopSkG6zuHOew=; b=hP4FIARGLZg6aDGishO5XGwX4BLjwYeXc9hMnOLTn9nKzWGVHr96u+tdM+58gKJU12O2Rz EXb3D1TP5ZiwOgpj6xl0MVfW0S7k2ZAQ3ywjg0jMt2oLQH1BLaNrcNv4R0q2OPJAPYpuKA nNEGYXLbu55SpJTdvYI/mOuHYpbmYUE= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1751365194; 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=F4jCtuuDml1rKQTvhcRaw4++6CgpogXopSkG6zuHOew=; b=H9MkZkfbN3N7I0E7BtST7dez0bR7s/V/ySo/jFVG0y3lNOIaeuUJKRJgFXZCcEiRt/igFx 4gH312PoacGskPdPjjIfvboQiqfoCsswBwgsZf/HpGack3wpCnd4nH9hWP8oCBv9uhR4aS xYOFR11++o0dSViWsxSO3AECZfm2VKE= 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-380-wkivPCrNMD67rW-YVFrKug-1; Tue, 01 Jul 2025 06:19:52 -0400 X-MC-Unique: wkivPCrNMD67rW-YVFrKug-1 X-Mimecast-MFC-AGG-ID: wkivPCrNMD67rW-YVFrKug_1751365191 Received: by mail-wm1-f69.google.com with SMTP id 5b1f17b1804b1-453817323afso32653915e9.1 for ; Tue, 01 Jul 2025 03:19:51 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1751365191; x=1751969991; 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=F4jCtuuDml1rKQTvhcRaw4++6CgpogXopSkG6zuHOew=; b=ODRkdq7xzujJhCRwXKZfPhu+sEoP0GMVyEKZdt8rGv6USQiDs13hWnoEY+Wx1st5Wb U4rSsTdQ+OQghEGhNegxKLo0yFoMr3OiMgPO1IeWfaq0BVBLUZSL5CBmLEh+hAVcpSkU oxQMc3FiOftfMs0vpEw66hN9uUTejDxXUPYVMs7ZKcyPiEnYMGs1cpCR3tzoBvPOW33B Df7GjK6JmnL2dQmjf0TXfMcC07EiilZUpqFQdujbxDEBPtAEUY19u+riS30nUb15e6wq w+v5Qqw/WJUkFmu20hNB29QLdsR9SQi3fZr5NVGvnxMogEoEkqA+x73XTZb6+XYRYZIh KQzQ== X-Forwarded-Encrypted: i=1; AJvYcCU3ByvOe/Fms2551hRIQwEV+KwZ7FEMZb0dFsJNvFAPlR9/pfeLj5Ie5GY3kn3Wf43Eo0GL1iSQlwoXKEg=@lists.ozlabs.org X-Gm-Message-State: AOJu0Yw2Kq7tvLfG2+hvxcmbMtdXcV7HSI6GfEcYV1jRrJu4HHUhypnR S3oxdUCoOipLnVfD8iadPYBHNzCRqPEGUpNAdViBdZZZed9fq5ZkXwrIJbv7Y6YVZZkIIsHDVlb wwTTr2T07IdhjeP2pJQMdbPreT3VdINa7CPq6DxqZOQVk3QKF2HdVJPRLRHb67sLIt+8= X-Gm-Gg: ASbGncsYY1MLGKio41taDPBzvc6v2vzyJAZAk75krcRL6r3JKjaxrcFaQZJcPlFuMaw yU8YwljOf4NTTuxqK+rFo4PzA2fqS/yDhZIklqJsYiQ6mpu3GgrkcQxWnADVz1nsSF2KmDXQDqf syqNMtmV9C+3wRGj/BuUuX65rbzQwRIhMc3p1p8bsCD3K5e7S81CGKS19xkHboP5Fba7PBMQXfJ 1vqPzrPCUsymJTGGyLnemOunZMq/1C8hx+UoPYjJDor97sT5bYbXPMYI/hiuhYNcHJ4sTuhYYou mfJYQehXhjcnsjvpB1oODBI/z66UWZfh4uOtT3jgyj3WoV/9hb44pTu6kpBw6hlxg2HhfgAxec8 qSj7M8075ynpb4yF2YiCXY84B6saFvnRpfHQApMUT0Ugqdtn3Mg== X-Received: by 2002:a05:600c:8b6f:b0:43c:fe15:41dd with SMTP id 5b1f17b1804b1-4538f9b3107mr146369115e9.6.1751365190641; Tue, 01 Jul 2025 03:19:50 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHpCA3mH1COjv0bYFBhoLOUBhwD5kNXEqvEScAb8vhGq9c4wIOHtPDtpOwNJjwRv+ZSvZmz2Q== X-Received: by 2002:a05:600c:8b6f:b0:43c:fe15:41dd with SMTP id 5b1f17b1804b1-4538f9b3107mr146368525e9.6.1751365190153; Tue, 01 Jul 2025 03:19:50 -0700 (PDT) Received: from ?IPV6:2003:d8:2f18:7500:202e:b0f1:76d6:f9af? (p200300d82f187500202eb0f176d6f9af.dip0.t-ipconnect.de. [2003:d8:2f18:7500:202e:b0f1:76d6:f9af]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a88c7e7386sm12685296f8f.20.2025.07.01.03.19.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 01 Jul 2025 03:19:49 -0700 (PDT) Message-ID: <94333692-0093-4351-a081-13e202dd2322@redhat.com> Date: Tue, 1 Jul 2025 12:19:47 +0200 X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 13/29] mm/balloon_compaction: stop using __ClearPageMovable() To: Lorenzo Stoakes Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, virtualization@lists.linux.dev, linux-fsdevel@vger.kernel.org, Andrew Morton , Jonathan Corbet , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Jerrin Shaji George , Arnd Bergmann , Greg Kroah-Hartman , "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , Alexander Viro , Christian Brauner , Jan Kara , Zi Yan , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , "Matthew Wilcox (Oracle)" , Minchan Kim , Sergey Senozhatsky , Brendan Jackman , Johannes Weiner , Jason Gunthorpe , John Hubbard , Peter Xu , Xu Xin , Chengming Zhou , Miaohe Lin , Naoya Horiguchi , Oscar Salvador , Rik van Riel , Harry Yoo , Qi Zheng , Shakeel Butt References: <20250630130011.330477-1-david@redhat.com> <20250630130011.330477-14-david@redhat.com> <65804db3-71c0-47ff-8189-6a1587d4a0cc@lucifer.local> 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: <65804db3-71c0-47ff-8189-6a1587d4a0cc@lucifer.local> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: LYQEoFfYJT7g3OzLZJDwfD-dkFzXsS92New7qREJjrQ_1751365191 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 01.07.25 12:03, Lorenzo Stoakes wrote: > On Mon, Jun 30, 2025 at 02:59:54PM +0200, David Hildenbrand wrote: >> We can just look at the balloon device (stored in page->private), to see >> if the page is still part of the balloon. >> >> As isolated balloon pages cannot get released (they are taken off the >> balloon list while isolated), we don't have to worry about this case in >> the putback and migration callback. Add a WARN_ON_ONCE for now. >> >> Signed-off-by: David Hildenbrand > > Seems reasonable, one comment below re: comment. > > Reviewed-by: Lorenzo Stoakes > >> --- >> include/linux/balloon_compaction.h | 4 +--- >> mm/balloon_compaction.c | 11 +++++++++++ >> 2 files changed, 12 insertions(+), 3 deletions(-) >> >> diff --git a/include/linux/balloon_compaction.h b/include/linux/balloon_compaction.h >> index bfc6e50bd004b..9bce8e9f5018c 100644 >> --- a/include/linux/balloon_compaction.h >> +++ b/include/linux/balloon_compaction.h >> @@ -136,10 +136,8 @@ static inline gfp_t balloon_mapping_gfp_mask(void) >> */ >> static inline void balloon_page_finalize(struct page *page) >> { >> - if (IS_ENABLED(CONFIG_BALLOON_COMPACTION)) { >> - __ClearPageMovable(page); >> + if (IS_ENABLED(CONFIG_BALLOON_COMPACTION)) >> set_page_private(page, 0); >> - } >> /* PageOffline is sticky until the page is freed to the buddy. */ >> } >> >> diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c >> index ec176bdb8a78b..e4f1a122d786b 100644 >> --- a/mm/balloon_compaction.c >> +++ b/mm/balloon_compaction.c >> @@ -206,6 +206,9 @@ static bool balloon_page_isolate(struct page *page, isolate_mode_t mode) >> struct balloon_dev_info *b_dev_info = balloon_page_device(page); >> unsigned long flags; >> >> + if (!b_dev_info) >> + return false; >> + >> spin_lock_irqsave(&b_dev_info->pages_lock, flags); >> list_del(&page->lru); >> b_dev_info->isolated_pages++; >> @@ -219,6 +222,10 @@ static void balloon_page_putback(struct page *page) >> struct balloon_dev_info *b_dev_info = balloon_page_device(page); >> unsigned long flags; >> >> + /* Isolated balloon pages cannot get deflated. */ >> + if (WARN_ON_ONCE(!b_dev_info)) >> + return; >> + >> spin_lock_irqsave(&b_dev_info->pages_lock, flags); >> list_add(&page->lru, &b_dev_info->pages); >> b_dev_info->isolated_pages--; >> @@ -234,6 +241,10 @@ static int balloon_page_migrate(struct page *newpage, struct page *page, >> VM_BUG_ON_PAGE(!PageLocked(page), page); >> VM_BUG_ON_PAGE(!PageLocked(newpage), newpage); >> >> + /* Isolated balloon pages cannot get deflated. */ > > Hm do you mean migrated? Well, they can get migrated, obviously :) Deflation would be the other code path where we would remove a balloon page from the balloon, and invalidate page->private, suddenly seeing !b_dev_info here. But that cannot happen, as isolation takes them off the balloon list. So deflating the balloon cannot find them until un-isolated. -- Cheers, David / dhildenb