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 B8BA3107637F for ; Wed, 1 Apr 2026 14:35:26 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 24BB46B0005; Wed, 1 Apr 2026 10:35:26 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 222EF6B0089; Wed, 1 Apr 2026 10:35:26 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0EB566B008A; Wed, 1 Apr 2026 10:35:26 -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 EF2466B0005 for ; Wed, 1 Apr 2026 10:35:25 -0400 (EDT) Received: from smtpin09.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 9B1B35B8C1 for ; Wed, 1 Apr 2026 14:35:25 +0000 (UTC) X-FDA: 84610235010.09.2380914 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf14.hostedemail.com (Postfix) with ESMTP id BD7C2100013 for ; Wed, 1 Apr 2026 14:35:23 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=YJJhGtI9; spf=pass (imf14.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1775054123; a=rsa-sha256; cv=none; b=Hl8mAUyeOu6t2Q1cNS78ZFuygJkxhy/a0tUIh8Jt9iigXvD2Uh0wSRgMq7ukc4c1+qTPka SdP1+SbJvYb/wTo8TVDiQ8QSqux8PcEQOI1cBAXtOrgJMkV/jm9B7BaqZ0mLbqMrqA2EYs km6buEbdaD/X2PKzTGWjvlNbPE54kZs= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1775054123; 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=DsuaJggPJGRJFR8J9on8seMW50aa+Y4/5qPXMJ7I3/s=; b=QCke0wmpScT5xsFS7hZJ8+wN0VYiD+cmex0aqDArccFCWSUJwS0XG1LynzzflKsru4Tszt dxHxaR2oPlO/w3NmstE66Zp3us/2OmkdxoVRCo/5Bd//KidPT4H1iiH9Ed9bJT7l7FdDf7 bqaK9UVVrUHLV9270y6yhx8XnmDJKIo= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=YJJhGtI9; spf=pass (imf14.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 2E1F060125; Wed, 1 Apr 2026 14:35:23 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D8489C4CEF7; Wed, 1 Apr 2026 14:35:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1775054122; bh=8L15mk7uBbIcb7Tq2K1XChKVrDaUFFZb9Sv7JfqIHto=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=YJJhGtI9LqaXWQGbRVZsPCUbXFlAgkfoX4ONmNboth4EOEPZ/BavQQ76K3894U6UB o4e7o4BAATRZ8R3zHDRokeuqDK+++QlmsrEtiFtENF3l6Xr4yce6xsquadb55zT+ZV S3QgbVdUGD2S+OTVwVxuRaB0p98IpDkit7XG2XsPRkTcGWwzN6/Cvyrys7jiHKpTrJ zZr1KX1PsRCo+vzPxmj9IolWPJMLgx5+x3O9Jtm3i82jP5VrpwOR/r0f4kOl27syp/ DUaRPDO008259oUk3rrNfXm5o8c8cwGeOFbDTrwdQKVIPjt3mFJ5J9Nu1wr+ANUAqb w/mSd6j0BrhxQ== Message-ID: Date: Wed, 1 Apr 2026 16:35:14 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 03/10] mm: fs: remove filemap_nr_thps*() functions and their users To: Zi Yan , "Lorenzo Stoakes (Oracle)" Cc: "Matthew Wilcox (Oracle)" , Song Liu , Chris Mason , David Sterba , Alexander Viro , Christian Brauner , Jan Kara , Andrew Morton , 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: <20260327014255.2058916-1-ziy@nvidia.com> <20260327014255.2058916-4-ziy@nvidia.com> <53cf6157-58b1-4539-a276-2486e8796c57@lucifer.local> <25899F67-955D-44DC-935E-D7F234BD335A@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: <25899F67-955D-44DC-935E-D7F234BD335A@nvidia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: BD7C2100013 X-Stat-Signature: txi3pg7sfiqdjgq7wwtsskxp34k6ypfo X-HE-Tag: 1775054123-879271 X-HE-Meta: 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 pt3CdLjj KU92AM83qJpOtMm8XGfLvKTS262t1ZI1j35a2VNWUc0OcsuXJb7gNxvQi/aJQIC5FgxOTN7HUE9hNiKp74piRaZOnQLPKK/EcCxrBFe0ZBt+AP7LzV9lZz5hpUOBQl+n9NFfXp7IRZBnGixTu5JHFvEC2MHci/JPfjwOiX3DqXLGgy0X0DCgBFULFDrwT9wgN4AsOMcM+iE9lAZmC1okq8jIJ2gtvO+dkhfToungS3fWYyNUVurF4y3/RaEG5yjUtGOc6vsemgesx6eCREsWEdf3T19auuTo6mxQnxzr5V3hvhWLS+5rAUY/IHA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/27/26 16:05, Zi Yan wrote: > On 27 Mar 2026, at 10:23, Lorenzo Stoakes (Oracle) wrote: > >> On Fri, Mar 27, 2026 at 02:58:12PM +0100, David Hildenbrand (Arm) wrote: >>> >>> There could now be a race between collapsing and the file getting opened >>> r/w. >>> >>> Are we sure that all code can really deal with that? >>> >>> IOW, "they already had to handle it separately" -- is that true? >>> khugepaged would have never collapse in writable files, so I wonder if >>> all code paths are prepared for that. >> >> OK I guess I overlooked a part of this code... :) see below. >> >> This is fine and would be a no-op anyway >> >> - if (f->f_mode & FMODE_WRITE) { >> - /* >> - * Depends on full fence from get_write_access() to synchronize >> - * against collapse_file() regarding i_writecount and nr_thps >> - * updates. Ensures subsequent insertion of THPs into the page >> - * cache will fail. >> - */ >> - if (filemap_nr_thps(inode->i_mapping)) { >> >> But this: >> >> - if (!is_shmem) { >> - filemap_nr_thps_inc(mapping); >> - /* >> - * Paired with the fence in do_dentry_open() -> get_write_access() >> - * to ensure i_writecount is up to date and the update to nr_thps >> - * is visible. Ensures the page cache will be truncated if the >> - * file is opened writable. >> - */ >> - smp_mb(); >> >> We can drop barrier >> >> - if (inode_is_open_for_write(mapping->host)) { >> - result = SCAN_FAIL; >> >> But this is a functional change! >> >> Yup missed this. > > But I added > > + if (!is_shmem && inode_is_open_for_write(mapping->host)) > + result = SCAN_FAIL; > > That keeps the original bail out, right? Independent of that, are we sure that the possible race we allow is ok? -- Cheers, David