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 6A0FEC36010 for ; Fri, 11 Apr 2025 08:37:26 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8A30828018D; Fri, 11 Apr 2025 04:37:25 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 85378280188; Fri, 11 Apr 2025 04:37:25 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6A50D28018D; Fri, 11 Apr 2025 04:37:25 -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 425E8280188 for ; Fri, 11 Apr 2025 04:37:25 -0400 (EDT) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 4FACF1CECE2 for ; Fri, 11 Apr 2025 08:37:25 +0000 (UTC) X-FDA: 83321108850.26.9F40392 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf10.hostedemail.com (Postfix) with ESMTP id C318AC0004 for ; Fri, 11 Apr 2025 08:37:22 +0000 (UTC) Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=ezYBy5GS; dmarc=pass (policy=quarantine) header.from=redhat.com; spf=pass (imf10.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=1744360643; a=rsa-sha256; cv=none; b=ZtegiHiqu1Dai+6yOW/yLayHqiQs6J09WFwXxNUcEXbdH5KZj5HcwcftgQUrHIQuPg6Hnw 6mQZjKCEM+0ZSmPMngRL8ifn0Lmn0mBQrR1lA+T/kJ7Jn8ImEz69PrP6RWVTgDZfhOKJs7 sBcIct6c1oQK9ASK9NN9UMUoMtQUjns= ARC-Authentication-Results: i=1; imf10.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=ezYBy5GS; dmarc=pass (policy=quarantine) header.from=redhat.com; spf=pass (imf10.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=1744360643; 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=JLslcSIDe5LlgtBN6zquly6cspPZPxoniRKKH+HI3wY=; b=WeLAhqJZEg9RDgbWkorcb1R2jOVxtgVtXPK5+afDjJuoyB61Vs1eX8IvJ8hFBhTgTi2BKe eD+PVvB3wKysMoINtDY7Y9mf/BhGBFP/QMWHMhFOZDbI81nQ4eeW+P3d8u/YOaK+urwYKC EZgFv08+fRFzku4dHDR8W4yCJgMGmxM= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1744360642; 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=JLslcSIDe5LlgtBN6zquly6cspPZPxoniRKKH+HI3wY=; b=ezYBy5GSwwPhmhlwbS+49FIzVAz7yFv2J0UXQt/DUWW8q6sSwzzdiFNIoG06cNfY7VY6NI T4nXtxxfTf8lRHSG4XW2o9rtB5axRVoh2XQZIXzSEfMSHpdww9lbhb8Q1pxQdIm357poVK zBG/Bsuh2/AK4bS06pnO844hvRPBKOE= Received: from mail-wr1-f69.google.com (mail-wr1-f69.google.com [209.85.221.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-59-d1vOWamgMou6gRalLz91kA-1; Fri, 11 Apr 2025 04:37:20 -0400 X-MC-Unique: d1vOWamgMou6gRalLz91kA-1 X-Mimecast-MFC-AGG-ID: d1vOWamgMou6gRalLz91kA_1744360640 Received: by mail-wr1-f69.google.com with SMTP id ffacd0b85a97d-39d917b105bso892394f8f.2 for ; Fri, 11 Apr 2025 01:37:20 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1744360639; x=1744965439; h=content-transfer-encoding:in-reply-to:organization:autocrypt:cc :from:content-language:references:to:subject:user-agent:mime-version :date:message-id:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=JLslcSIDe5LlgtBN6zquly6cspPZPxoniRKKH+HI3wY=; b=Pt6Sx3gbfe5ocQ1EvMN9J/sWILZZJl0GldZu2Gaj8V/E43DQGNOM9vc/uolJQhFkJ3 qrTOS7cbkCjdi0zM0duxAS78FzMrq9pGeTXjRBlkeW4c9h2yCV/p/QETllxEu5L5J5ei mODNqjwW0TNCCW8TRQCZFHCYmGjlx3kJ7P1o6e3fAAkRxaPQ0+fUtJ1l1DyASM2W6eVP vcybptSFJ8SEJQL5PECisXIZn6j8e8+O/8p2SObYjzInGchmbECaH3MVAGFk2+fUY6ah SjRTAsHQvEZ7zcwDEXeHKDqEmcc0CXu0iEMKh5ACRZDaVAXii3mUFbscYdGmlGwdSdLW wrpA== X-Gm-Message-State: AOJu0YyIEX52DEe1qLHQLeStf0NGniBLzwCVrWdo3kZsaUah8ZW3f/qo VC5wNKRBu0RcR6vYqDO1q7xv0Q6s9vgdXaUec6nRX4MDewAf89U9g6o/rICebLGOJ3BBGO0bPY7 +aIDZSxGLSHV4g3s8R4kOtMmvKCTadx5f+/578iWlHOpZgikWAtnHpZLq6kQ= X-Gm-Gg: ASbGnct5npC2QtMBZNXc2xb6c/PhzOeC2v3LBFEaejezpoUtqAzgPCELU980NjBoEE3 4jWkd5HXuwWnI7lonxHKXC76SNKtJOWk8+RUJxUL0lEEe5mxb0bheTA/qHRT+aV9XE4YYEPLUsI +gle5FTWzkWcV47ssIz/Zjr2+RSDMWWrXe2zrQsKKrBw5ZXpt63msQz/elO9N65zBjGOhNGUW62 pb1/pdyAIB7JpnVl6OzaOJUhc3ISnmc07PJ8lffqIMCE9nyv+MGyQRcKDRCfkeG6xqqy+oa6A2T Cx1A9wHkeZY9Dx/UNAmA+uR27vp4iAs3k2vgaxXic3YwKVZ1gcVZTZj0NKs5RYLHZC0zxSizgGC L0DJIsE23wAcNU4Kd42ZUWnAnnTaKVb51XuyZ X-Received: by 2002:a5d:584b:0:b0:390:de33:b0ef with SMTP id ffacd0b85a97d-39ea644020dmr1231852f8f.30.1744360639573; Fri, 11 Apr 2025 01:37:19 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFy/nxOARvXAgp07ONVwaKQG7V6q2L0VxkCLDReSCXO28buDSxhWR/BAmHdCLtwrV6dKAUbOg== X-Received: by 2002:a5d:584b:0:b0:390:de33:b0ef with SMTP id ffacd0b85a97d-39ea644020dmr1231822f8f.30.1744360639093; Fri, 11 Apr 2025 01:37:19 -0700 (PDT) Received: from ?IPV6:2003:cb:c726:6800:7ddf:5fc:2ee5:f08a? (p200300cbc72668007ddf05fc2ee5f08a.dip0.t-ipconnect.de. [2003:cb:c726:6800:7ddf:5fc:2ee5:f08a]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-39eaf43cb29sm1309748f8f.76.2025.04.11.01.37.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 11 Apr 2025 01:37:18 -0700 (PDT) Message-ID: <6e1a9ad5-c1e1-4f04-af67-cfc05246acbc@redhat.com> Date: Fri, 11 Apr 2025 10:37:17 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1] fs/dax: fix folio splitting issue by resetting old folio order + _nr_pages To: Alistair Popple References: <20250410091020.119116-1-david@redhat.com> From: David Hildenbrand Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, nvdimm@lists.linux.dev, Alison Schofield , Alexander Viro , Christian Brauner , Jan Kara , Dan Williams , Matthew Wilcox , Andrew Morton , Alistair Popple , Christoph Hellwig , "linux-kernel@vger.kernel.org" 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-MFC-PROC-ID: Cc4QXbEO3pBIU8T-3yTxVIuL7XCPEwJqU4geLEvS0VA_1744360640 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: C318AC0004 X-Stat-Signature: zeotnmmfuchbp3y1zio4si8bxbbgf5f9 X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1744360642-700580 X-HE-Meta: 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 odq7gdm6 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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: (adding CC list again, because I assume it was dropped by accident) >> diff --git a/fs/dax.c b/fs/dax.c >> index af5045b0f476e..676303419e9e8 100644 >> --- a/fs/dax.c >> +++ b/fs/dax.c >> @@ -396,6 +396,7 @@ static inline unsigned long dax_folio_put(struct folio *folio) >> order = folio_order(folio); >> if (!order) >> return 0; >> + folio_reset_order(folio); > > Wouldn't it be better to also move the loop below into this function? The intent > of this loop was to reinitialise the small folios after splitting which is what > I think this helper should be doing. As the function does nothing on small folios (as documented), I think this is good enough for now. Once we decouple folio from page, this code will likely have to change either way ... The first large folio will become a small folio (so resetting kind-of makes sense), but the other small folios would have to allocate a new "struct folio" for small folios. > >> for (i = 0; i < (1UL << order); i++) { >> struct dev_pagemap *pgmap = page_pgmap(&folio->page); >> diff --git a/include/linux/mm.h b/include/linux/mm.h >> index b7f13f087954b..bf55206935c46 100644 >> --- a/include/linux/mm.h >> +++ b/include/linux/mm.h >> @@ -1218,6 +1218,23 @@ static inline unsigned int folio_order(const struct folio *folio) >> return folio_large_order(folio); >> } >> >> +/** >> + * folio_reset_order - Reset the folio order and derived _nr_pages >> + * @folio: The folio. >> + * >> + * Reset the order and derived _nr_pages to 0. Must only be used in the >> + * process of splitting large folios. >> + */ >> +static inline void folio_reset_order(struct folio *folio) >> +{ >> + if (WARN_ON_ONCE(!folio_test_large(folio))) >> + return; >> + folio->_flags_1 &= ~0xffUL; >> +#ifdef NR_PAGES_IN_LARGE_FOLIO >> + folio->_nr_pages = 0; >> +#endif >> +} >> + I'm still not sure if this splitting code in fs/dax.c is more similar to THP splitting or to "splitting when freeing in the buddy". I think it's something in between: we want small folios, but the new folios are essentially free. Likely, to be future-proof, we should also look into doing folio->_flags_1 &= ~PAGE_FLAGS_SECOND; Or alternatively (better?) new_folio->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; ... but that problem will go away once we decouple page from folio (see above), so I'm not sure if we should really do that at this point unless there is an issue. -- Cheers, David / dhildenb