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 68D14C88E77 for ; Mon, 14 Sep 2026 14:19:26 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 522016B0092; Mon, 14 Sep 2026 10:19:25 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4D1796B0093; Mon, 14 Sep 2026 10:19:25 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 39D586B0096; Mon, 14 Sep 2026 10:19:25 -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 F09A66B0092 for ; Mon, 14 Sep 2026 10:19:24 -0400 (EDT) Received: from smtpin10.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 60C321C033E for ; Mon, 14 Sep 2026 14:19:24 +0000 (UTC) X-FDA: 85212575448.10.4CEC69E Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf31.hostedemail.com (Postfix) with ESMTP id 9515020009 for ; Mon, 14 Sep 2026 14:19:22 +0000 (UTC) Authentication-Results: imf31.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b="U/iC27fy"; spf=pass (imf31.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1789395562; 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=10wyQv57KEE9SMXNGbyIiW8Kh9XTq71YhEymhF3vAwk=; b=CRDcK0vHL98WOt80yQG+CnirPdCyrsZ291X/oGEmBjBlzldIhNWSNb+kubUzAXNglCBJw1 t8YBJUGODJPfEnPdV9g0VbaZP2y39rOyc3U0eXuU+MjIn7dKUpb1SfQ2gqw0IR0UkLnNx3 eSoPOqMwJCu5QMzP2W/Prsof+J8be0E= ARC-Authentication-Results: i=1; imf31.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b="U/iC27fy"; spf=pass (imf31.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1789395562; b=tgJLe+4RjtT2s12W3PI3V4chwW7rxeHAGZ5nNW+WJPIpVSy/O2TviWtS8E2VS6j3vKLOnU tV+MVVkdQW2AasiZBu/I/yNkhqOaayxrEvBTdkX8Yo1ZJd53xYI9uThXzofBlsocMVi8p0 291I4DmMJjUXm+c9iXGIdflY7Jw+msE= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id C2B2A4192E; Mon, 14 Sep 2026 14:19:21 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 160C81F000FF; Mon, 14 Sep 2026 14:19:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789395561; bh=10wyQv57KEE9SMXNGbyIiW8Kh9XTq71YhEymhF3vAwk=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=U/iC27fyYo0NPgeyFOP9BJKiSUvPwYxMYnTV89LUYfkhdwEmfDiyojfMr3GWRDzIE K4lAh3RyhH3m933a2edNrwxqagBPjvV2ryDAzqrpr4iMNO+O/MX7EWQmV4JJCURfeu XVkCpCY8AIULJn3mqtnkUwC0Ke43LA5VTMGIiL9jjbLxSJxbugnQJkN/huizL1v3d7 ClWriOS3JzN80e4ZFPcSUL6YPhHHS/cHeYb4uaFdOMM9NbXZ6CShf5uhBjYvqg5VV3 YckvqbwUn3qQt8Pa2JjAcLR0Cae5cNHcx7d8usO+OZTlCfsu/hNdH9d0gyUOm7TQVS dcLMIRq4lr0QA== Message-ID: <00dcd8d2-67f3-4ecd-bd7f-06ba1f9c106a@kernel.org> Date: Mon, 14 Sep 2026 16:19:11 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] khugepaged: hold invalidate_lock across collapse_file() readahead To: "Lorenzo Stoakes (ARM)" , Andrew Morton Cc: Nguyen Ngoc Thang , Zi Yan , Baolin Wang , "Liam R . Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Matthew Wilcox , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Jan Kara , Hugh Dickins , Mike Rapoport References: <20260913163644.122133-1-ngocthang2710.1999@gmail.com> <20260913111700.6de78b5834842f7dd3f12d07@linux-foundation.org> 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: rspam02 X-Rspamd-Queue-Id: 9515020009 X-Stat-Signature: rbiu4teemufj53bdz77cmrmbk1xozgua X-Rspam-User: X-HE-Tag: 1789395562-366687 X-HE-Meta: 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 iVh8uasp 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/13/26 20:48, Lorenzo Stoakes (ARM) wrote: > (Nguyen - do not send v2 in reply to v1, look across mm and see how things are > done here). > > somebody who has a > > On Sun, Sep 13, 2026 at 11:17:00AM -0700, Andrew Morton wrote: >> On Sun, 13 Sep 2026 23:36:44 +0700 Nguyen Ngoc Thang wrote: >> >>> collapse_file() calls page_cache_sync_readahead() to fault in missing >>> pages before collapsing them into a THP. That helper takes >>> mapping->invalidate_lock itself for the duration of the call, then >>> drops it -- but truncate (e.g. ext4_setattr() -> truncate_pagecache()) >>> takes invalidate_lock and then waits on each page's folio lock while >>> holding it. If collapse_file() has already locked one of those folios >>> by the time truncate reaches it, and then tries to acquire >>> invalidate_lock again (e.g. on the first readahead call, since >>> invalidate_lock is not yet held at that point), the two paths can >>> deadlock/hang on each other's lock: truncate blocked on the folio lock >>> collapse holds, and collapse blocked waiting for invalidate_lock that >>> truncate holds. >>> >>> Reproducing this over ~150,000 collapse iterations with truncate >>> racing concurrently reliably hits hung_task: blocked tasks within >>> about 20 seconds on an unpatched kernel. >>> >>> Fix it by taking invalidate_lock_shared once for the whole scan, after >>> alloc_charge_folio() succeeds and before locking any folio, and using >>> page_cache_ra_unbounded() directly in the readahead call site instead >>> of page_cache_sync_readahead(), since the latter would try to retake >>> the lock we already hold. page_cache_ra_unbounded() does not clamp to >>> EOF like the helper it replaces, so clamp the requested range >>> explicitly. >>> >>> 730633f0b7f9 added invalidate_lock acquisition around readahead but >>> missed collapse_file(), which already locks pages while calling >>> readahead; later filesystem conversions made the deadlock reachable by >>> taking invalidate_lock before waiting on page locks during truncate. >>> >>> Reported-by: syzbot+16bf7cd0ebeb1de93aa5@syzkaller.appspotmail.com >>> Closes: https://syzkaller.appspot.com/bug?extid=16bf7cd0ebeb1de93aa5 >>> Fixes: 730633f0b7f9 ("mm: Protect operations adding pages to page cache with invalidate_lock") >> >> (You forgot to cc the original author) > > Also a change log, and that mm doesn't like sending a respin in-reply-to a > previous version. Which is all consistent with somebody using e.g. openclaw to > pepper generated patches across the kernel... > >> >> Five years. >> >> I wonder why this hasn't been discovered by lockdep, AI, syzbot or any >> other of the tools we've been using for so long. >> >> Thanks for doing all this. > > See https://lore.kernel.org/linux-mm/aqbtfms0_2ULBIT7@gremlin/ > > I am not really entirely happy with somebody who has sent a flurry of patches > across disparate subsystems with no previous track record being in charge of a > potentially backported fix. > > It's David's decision but I think this fix should be taken over by somebody > else. IIUC, this patch might be responsible for random CI failures (Mike still investigating). So I'd prefer if this is taken over by someone familiar with that code. @Willy, @Zi, @Lance? -- Cheers, David