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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 81A8ECD342F for ; Fri, 8 May 2026 20:09:38 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E23836B0274; Fri, 8 May 2026 16:09:37 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id DD4136B0275; Fri, 8 May 2026 16:09:37 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C9C096B0276; Fri, 8 May 2026 16:09:37 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id B7CC96B0274 for ; Fri, 8 May 2026 16:09:37 -0400 (EDT) Received: from smtpin19.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 5EB2087456 for ; Fri, 8 May 2026 20:09:37 +0000 (UTC) X-FDA: 84745342794.19.8F66D3C Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf06.hostedemail.com (Postfix) with ESMTP id 9F1E8180007 for ; Fri, 8 May 2026 20:09:35 +0000 (UTC) Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=m4tZNpao; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf06.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1778270975; 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=Gwpxap+WR2Bxv5srL+R/mh+gO8CoutdhNTSTODA7hxA=; b=NdOIdXFov0+zzUm7KOGdj+K2QaIJoWPen1j3oSqdM4UH1F5PHHI/UVGOf7PrYRa+ElfKY7 4+3XNfjQcAdfKxGvEpdW8+LsWf7XBQJ4Bl+k7ExdR9Dm67N9FJIqheNf9ISPjcl4j/1j4J XGl7+ITfMiG/2Hl3bTuqOSWWFWA3AmE= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1778270975; a=rsa-sha256; cv=none; b=5zQ5kN76ecxETFtN/AP1DJDlfDE8TY0VeSIswnR3ZSQ0ipAg1QsCFtVgWjDe8iZYZ+CVKq bxTMEctzFKQuqe4EzMXQYiwObw37ZQZOBnpueczGCV+L0meroSzuBfM33tJPdoMLCT1gJy p2WR+inrcNzdyo/NLVTY/GS2bdTKamg= ARC-Authentication-Results: i=1; imf06.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=m4tZNpao; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf06.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 118536024D; Fri, 8 May 2026 20:09:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BA8FCC2BCB0; Fri, 8 May 2026 20:09:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778270974; bh=t5h/pbwLwJoMHajI/15IwmnbpJqPM0yySlvu9EFrr1A=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=m4tZNpaoWxVYS7/LIvxw+3IqL/2lAfawJ/rtqwePsUP0JKCQYPGJ22Y1uZrgmLxif oeOwuxUIGI1ArhngJrhwS0oJ4IP0zZxelswhP7BWGQdm/judK0rGGnGaQMQMxeUJun Xk9zMcI7f1za1jyxBDZub+Onk+ZHcW9bdn71LcDLAerJSLENxxb4fZgBiI25X6xLT/ PsSfCQ6La7NtzuAewmc5mWbeunaktUwH4qyJEml/OagSokzAhutYcds/varYgMUC/K wIGRFD08sVLqcWQcEaKIa2HIvjhsfLv2Iz+sY66VqNtqowY/Ln81gcU1UWHdYW3Gxu L7sayZY/ZTw1g== Message-ID: <6b2a81e0-21c8-4454-a07b-dd025d032a67@kernel.org> Date: Fri, 8 May 2026 22:09:24 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 13/14] mm/khugepaged: enable clean pagecache folio collapse for writable files To: Zi Yan , Andrew Morton , "Matthew Wilcox (Oracle)" , Song Liu Cc: Chris Mason , David Sterba , Alexander Viro , Christian Brauner , Jan Kara , Lorenzo Stoakes , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org References: <20260429152924.727124-1-ziy@nvidia.com> <20260429153538.727855-9-ziy@nvidia.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 9F1E8180007 X-Stat-Signature: oxr65exbwij1ekchppxaedgs3wnu5ors X-Rspam-User: X-HE-Tag: 1778270975-824403 X-HE-Meta: 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 5VLnGAwC Kst5xQwd+XMWoXOnFB/80Q1hyDBaBb0NLOXeOiGt+ldKa6iZMHgrIrSSf/dKixa7Lcrwa2Qi14RZXcH8CGqfv8yQc58beK6bMeVpx5RA7Xml7b4pP/9/yA4ZeXA9KpmuXntXEgxpddHLH0UbdJYQnbu4GBBtXgs49dRJ1iYcQo9edReFOlyYQjODmkAO4JFIxgzDLovtA0jZ5Z64vDTqvVX9Xn1LhFn0oTEKImYCwj8H1q/pD2koAckD3Ivv6AyKEc7jV Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/30/26 17:18, Zi Yan wrote: > On 29 Apr 2026, at 11:35, Zi Yan wrote: > >> collapse_file() is capable of collapsing pagecache folios from writable >> files to PMD folios. Now enable clean pagecache folio collapse in addition >> to read-only pagecache folio collapse by removing the >> inode_is_open_for_write() from file_thp_enabled() and only performing >> filemap_flush() if the file is read-only. >> >> This means userspace needs to explicitly flush the content of pagecache >> folios before khugepaged can collapse the folios, or use >> madvise(MADV_COLLAPSE), which does the flush in the retry. The reason is >> that blindly enabling dirty pagecache folio from writable files collapse >> makes khugepaged flush these folios all the time. It is undesirable to >> cause system level pagecache flushes. >> >> To properly support dirty pagecache folio collapse, filemap_flush() needs >> to be avoided. Potentially, merging associated buffer instead of dropping >> it with filemap_release_folio() might be needed. >> >> NOTE: this breaks khugepaged selftests for writable file pagecache >> collapse, which is set to fail all the time. The next commit fix it. > > Sashiko: > > Is it acceptable to intentionally break the selftests in this commit? Each > commit should be self-contained and not knowingly introduce test regressions, > as this breaks bisectability. > > Answer: > > I am fine with squashing patch 14 into this one, but it is unlikely anyone > gets a kernel at exact this commit. For bisecting maybe problematic. I wouldn't squash it, though, instead prepare the selftests in a different way beforehand, such that they won't get broken? -- Cheers, David