From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id ED82E29B8CE for ; Thu, 12 Jun 2025 17:41:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749750116; cv=none; b=K64+kjDHSUnnkQ+8OeNUQx+OJ69JgHZNs2a/fJq+ukypcttLyfgL3kLLPCIQAbEHmqWCMr6KvCJP3uFP/UbikRmxFr6WmFsb7ucxkySMIrW+tkVx5km/C7xjS0KJVM85Md5F7knpuDfttGULCX/nTVxwGQ+wkhOVgibTptcIZzs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749750116; c=relaxed/simple; bh=B8VpAHwfvI8i7kBnmQPWL24V95l1cq9qu0i03mzZkrE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=J2IN8qWjgU2x9VhafT1Xz9mAx+nw/BkX9FBjj9RNOnjS6pM7kPJxyUvaffba13yAr4f6kKX99Y7PXPamtUeKnX0E0BfH+mMlpSGp89WMp78UHf4ieStAbhdAnUpuso1bWAp/mqvz4CYHWfU78qPtHFVMdri+sa5IcbDxKqOXYHM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=PEi7bVcU; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="PEi7bVcU" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1749750113; 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=Nd1EHOKRplIldRLyZRvXL96+1haDOUsvq+XwVjIOUoA=; b=PEi7bVcU1yWIgyUYlnVQMmtCTNWN76PPYsuJhnk8udrkiZjNGCSe37jZvwFwCPVScZGaO6 en2Okf+W61ibKD5Vv4P+J68NsBgCEa634a88/LFegO6vmvUH1Ivyooqf2m6iu/opy9uGas Cj7xXTB+BPygeABZDPYfHt5DjOBgLnE= Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-609-TDYwJTYBMM6vu7aWKI6HCQ-1; Thu, 12 Jun 2025 13:41:50 -0400 X-MC-Unique: TDYwJTYBMM6vu7aWKI6HCQ-1 X-Mimecast-MFC-AGG-ID: TDYwJTYBMM6vu7aWKI6HCQ_1749750110 Received: by mail-wr1-f72.google.com with SMTP id ffacd0b85a97d-3a4edf5bb4dso1021262f8f.0 for ; Thu, 12 Jun 2025 10:41:50 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1749750109; x=1750354909; 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=Nd1EHOKRplIldRLyZRvXL96+1haDOUsvq+XwVjIOUoA=; b=RoYtKhFFi2RyOSKy/i0Oy+F6ZgPkU0VfNqcRDmn/QI327sxL+rXHmrhIPYCR5XsM+q mmTx+/eeJGZVrUbLUu2Rls4kFVD6QjDqqBQkR1fWqqKlgDH0FPKcSpYR1Hr7Dzgi8CC3 Ys3wlwlT6iHAIHYBvghSDq9FTHuQaS79lSw/Ruccl1ycT0ClqL0YBH9OI3rOQvj5FKz/ cxI7D/C/NVSWqMLoV37uxXU/0p1oc5IDm9hOXgzwFeuKTLQ9OQ0301HZb9RMy/77fZPP FIxJcpEZz7snVzI/V13BE7EQhYlNrbtec+lhmcLgsbMuic9nLM7ETLiKVqdLy+KoMVOP E03A== X-Gm-Message-State: AOJu0Yy4GBQdf4eebXuW76/b+kMjGMBuCZm4J+nrcAs6YiTWigRdSSiB 9/6DA7Rt9wdHKIeVnUwmiD8KMYITHkR97jA++t8NnxbYnmTI5EaRuC6fEBUE36lNyCw8ZFQA/cc YSG6tKWRHyIDdj84BL/FPzLWJyuH9ekoqw/CUIXnwZbLTiijd49slAFy9RJ0fi0W2Nw== X-Gm-Gg: ASbGncuRs4ypI6apZZUcz1OwH8GnybDe43xalyOmUBIIHJ9D44QgS49gB/QYGWx2lo7 tLGknuzNqqsgYLs5BIXr9lxmXedKIbSnCWP5esHHjoJtxfmur7WHjYmZwrtV/T9jGYFIHsy8sCz qHgwuccG2x2jmCRUkgc7DvaM7B4t6xHv8NhygQzgSiSqAZhy9mvM1/JcunnzIIxdQ6blwwUc65Z NaD1OvA2+kdnguHhIFrDSwxsCtm/D8UvMe0/qjI1jK09A4U70zfDCCZfDqvrNFwO4zMxAqGsU/R Zoi/1zbqlxfjfPwT5JQQuKmlXAPA7rNE00g6vK3SdHqmTdFQytvyhmVq+wTYy2RxcX9BwFvuQn5 tampueHhtphNM2LUs5wn0CDE4LNwAP4DhILCSTJokvXWaQtvoEg== X-Received: by 2002:a05:6000:288b:b0:3a4:fe9d:1b10 with SMTP id ffacd0b85a97d-3a56873d3a8mr158684f8f.45.1749750109572; Thu, 12 Jun 2025 10:41:49 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHfpBKp7WSfATvU5HWRVC3xGg1b8tBhRVQX2JrvbDdW+mk61yVjqSa2K+6CTbQGfcAM+wsqmg== X-Received: by 2002:a05:6000:288b:b0:3a4:fe9d:1b10 with SMTP id ffacd0b85a97d-3a56873d3a8mr158669f8f.45.1749750109173; Thu, 12 Jun 2025 10:41:49 -0700 (PDT) Received: from ?IPV6:2003:d8:2f2c:1e00:1e1e:7a32:e798:6457? (p200300d82f2c1e001e1e7a32e7986457.dip0.t-ipconnect.de. [2003:d8:2f2c:1e00:1e1e:7a32:e798:6457]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a56199aa52sm2613251f8f.36.2025.06.12.10.41.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 12 Jun 2025 10:41:48 -0700 (PDT) Message-ID: Date: Thu, 12 Jun 2025 19:41:47 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 3/3] mm/huge_memory: don't mark refcounted folios special in vmf_insert_folio_pud() To: Lorenzo Stoakes Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, Andrew Morton , Alistair Popple , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Dan Williams , Oscar Salvador References: <20250611120654.545963-1-david@redhat.com> <20250611120654.545963-4-david@redhat.com> <177cb5d1-4fde-4fa0-adbc-8e295fba403b@lucifer.local> <11d1ff4d-3f75-42a5-968e-8f4bad84ab78@redhat.com> <43e2b05f-c499-48c3-b8e4-a23ef5efc818@lucifer.local> From: David Hildenbrand Content-Language: en-US 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: <43e2b05f-c499-48c3-b8e4-a23ef5efc818@lucifer.local> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 12.06.25 19:08, Lorenzo Stoakes wrote: > On Thu, Jun 12, 2025 at 07:00:01PM +0200, David Hildenbrand wrote: >> On 12.06.25 18:49, Lorenzo Stoakes wrote: >>> On Wed, Jun 11, 2025 at 02:06:54PM +0200, David Hildenbrand wrote: >>>> Marking PUDs that map a "normal" refcounted folios as special is >>>> against our rules documented for vm_normal_page(). >>> >>> Might be worth referring to specifically which rule. I'm guessing it's the >>> general one of special == don't touch (from vm_normal_page() comment): >>> >>> /* >>> * vm_normal_page -- This function gets the "struct page" associated with a pte. >>> * >>> * "Special" mappings do not wish to be associated with a "struct page" (either >>> * it doesn't exist, or it exists but they don't want to touch it). In this >>> * case, NULL is returned here. "Normal" mappings do have a struct page. >>> * >>> * ... >>> * >>> */ >> >> Well, yes, the one vm_normal_page() is all about ... ? :) > > Lol yes to be fair that is pretty obvious... > >> >>> >>> But don't we already violate this E.g.: >>> >>> if (vma->vm_ops && vma->vm_ops->find_special_page) >>> return vma->vm_ops->find_special_page(vma, addr); >>>> I mean this in itself perhaps means we should update this comment to say >> 'except >>> when file-backed and there is a find_special_page() hook'. >> >> I rather hope we severely break this case such that we can remove that hack. >> >> Read as in: I couldn't care less about this XEN hack, in particular, not >> documenting it. >> >> I was already wondering about hiding it behind a XEN config so not each and >> every sane user of this function has to perform this crappy-hack check. > > Yeah, I'm not a fan of generalised hooks if they can be avoided, especially ones > where you pass critical data structures like VMAs. > > It means you can, in theory, make no assumptions about what the caller does and > yeah. > > To do this for such a stupid edge case is ridiculous. Also, I am not sure if this works at all as intended. I want to look into cleaning that up ... When we inserted the page, we sure must have taken a reference, but when we inserted it we set pte_special() and ... didn't take a reference? Hmmmm > >> >> [...] >> >>>> } >>>> >>>> - entry = pud_mkhuge(pfn_t_pud(pfn, prot)); >>>> - if (pfn_t_devmap(pfn)) >>>> - entry = pud_mkdevmap(entry); >>>> - else >>>> - entry = pud_mkspecial(entry); >>>> + if (fop.is_folio) { >>>> + entry = folio_mk_pud(fop.folio, vma->vm_page_prot); >>>> + >>>> + folio_get(fop.folio); >>>> + folio_add_file_rmap_pud(fop.folio, &fop.folio->page, vma); >>>> + add_mm_counter(mm, mm_counter_file(fop.folio), HPAGE_PUD_NR); >>> >>> Nit, but might be nice to abstract for PMD/PUD. >> >> Which part exactly? Likely a follow-up if it should be abstracted. > > Ah on second thoughts it doesn't matter, because you're using pud variants of > everything such that it wouldn't be worth it. > > Disregard this ;) Ah, I was already suspecting that you might have missed the sneaky _pud :) -- Cheers, David / dhildenb