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 320E5C3DA64 for ; Sun, 28 Jul 2024 22:35:38 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id BA3946B007B; Sun, 28 Jul 2024 18:35:37 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B2BF86B0083; Sun, 28 Jul 2024 18:35:37 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9CC386B0085; Sun, 28 Jul 2024 18:35:37 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 7DCF86B007B for ; Sun, 28 Jul 2024 18:35:37 -0400 (EDT) Received: from smtpin01.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id F0381C0117 for ; Sun, 28 Jul 2024 22:35:36 +0000 (UTC) X-FDA: 82390619472.01.18BC9C5 Received: from out30-119.freemail.mail.aliyun.com (out30-119.freemail.mail.aliyun.com [115.124.30.119]) by imf18.hostedemail.com (Postfix) with ESMTP id B47D21C0012 for ; Sun, 28 Jul 2024 22:35:33 +0000 (UTC) Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=linux.alibaba.com header.s=default header.b=GpegNqVG; spf=pass (imf18.hostedemail.com: domain of hsiangkao@linux.alibaba.com designates 115.124.30.119 as permitted sender) smtp.mailfrom=hsiangkao@linux.alibaba.com; dmarc=pass (policy=none) header.from=linux.alibaba.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1722206065; 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=P9/Y+mej2So4jx4de2w01BkC1NpRz5XlWcJk7/0wxTY=; b=otJAHtWI+A9DdeTBLITS/INGZ7gMxxIre2LJwcu450Zyuy1l5xeovaKC42+ArNanDMuzZA XW2ZhCjmDGcmuPfpdLWwwL6aVxUUIgDpua2KRZRTSFP6PYA6ifk3G5aIN49NZQAQYCx8S4 LQ5Pch+kWs1IGxrHp2rWIoo3eVLklnM= ARC-Authentication-Results: i=1; imf18.hostedemail.com; dkim=pass header.d=linux.alibaba.com header.s=default header.b=GpegNqVG; spf=pass (imf18.hostedemail.com: domain of hsiangkao@linux.alibaba.com designates 115.124.30.119 as permitted sender) smtp.mailfrom=hsiangkao@linux.alibaba.com; dmarc=pass (policy=none) header.from=linux.alibaba.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1722206065; a=rsa-sha256; cv=none; b=ACU39mLkg55/iBKqpYGdtUyAMtZbKHcIosu2VXmNO5lH9dVxV/m6hphJPhyXMV08clutvz ZM3vT9ec+njVRNbmpANjszdoNLO6TRfJqjkrYZ5rpckVmm0z3iGM3Ol0UaHw4/TynDrUSN Kkue8SusRggUTd4rrPFQfaQsz9F7Riw= DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1722206130; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=P9/Y+mej2So4jx4de2w01BkC1NpRz5XlWcJk7/0wxTY=; b=GpegNqVGoWyWaMwjMaX6jIB2lpGMxARlrZAxLDPZKCs6KUqnzcGFsFCtJYNom3dJ5lEeZat3Q6ErtM99J+kEhYEQ5MsSr7nfsQYpL5DPlIlf85FrvyQ15FdpQmBi6/oJG2W4eWyXTgbi4S+5uAqSlgZJ3q5VIwte48ubX0wORQQ= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R201e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033037067110;MF=hsiangkao@linux.alibaba.com;NM=1;PH=DS;RN=5;SR=0;TI=SMTPD_---0WBSCAoQ_1722206126; Received: from 172.20.10.3(mailfrom:hsiangkao@linux.alibaba.com fp:SMTPD_---0WBSCAoQ_1722206126) by smtp.aliyun-inc.com; Mon, 29 Jul 2024 06:35:29 +0800 Message-ID: <47dd353a-754c-4ded-a9bb-11f8400ac3fe@linux.alibaba.com> Date: Mon, 29 Jul 2024 06:35:22 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/migrate: fix deadlock in migrate_pages_batch() on large folios To: Matthew Wilcox , Huang Ying , Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20240728154913.4023977-1-hsiangkao@linux.alibaba.com> <20240728125005.c1171fa2d1beb6c1fe867d48@linux-foundation.org> From: Gao Xiang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: B47D21C0012 X-Stat-Signature: z1h3wbrkeznan16p9i788fas38tfc759 X-Rspam-User: X-HE-Tag: 1722206133-72704 X-HE-Meta: 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 5fhzd6HP N92o0Fd6qMHTnaSciM3PBjid4Im1UEs9nDzJ9rkMh3IGAfRdHiBunLtl7AHshIPr+io4+4cRBljPJ9iuO3QUyUMmml6W5epPVOJj8C3F/cV56ItgFl9ryGQlC4FfpqL+VHxwYGO2urwd8ntmuo/GgncXEIMhJcvH48MG/87BIUDVIPyvlGAzdza496TSNIOGiYUjYRmhgbEt9sG87GW80jTpUXMseagawOVEiYIP6m8dWrNxemC5LpyGxkJkSnLM1FkI1IfX/uidxUjwDltavZhAlKw0IMHQXyKwvLu0VLr6WoszCinSTp3tURzSpvAxZVwb+ 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: Hi, On 2024/7/29 05:17, Matthew Wilcox wrote: > On Sun, Jul 28, 2024 at 12:50:05PM -0700, Andrew Morton wrote: >> On Sun, 28 Jul 2024 23:49:13 +0800 Gao Xiang wrote: >>> Currently, migrate_pages_batch() can lock multiple locked folios >>> with an arbitrary order. Although folio_trylock() is used to avoid >>> deadlock as commit 2ef7dbb26990 ("migrate_pages: try migrate in batch >>> asynchronously firstly") mentioned, it seems try_split_folio() is >>> still missing. >> >> Am I correct in believing that folio_lock() doesn't have lockdep coverage? > > Yes. It can't; it is taken in process context and released by whatever > context the read completion happens in (could be hard/soft irq, could be > a workqueue, could be J. Random kthread, depending on the device driver) > So it doesn't match the lockdep model at all. > >>> It was found by compaction stress test when I explicitly enable EROFS >>> compressed files to use large folios, which case I cannot reproduce with >>> the same workload if large folio support is off (current mainline). >>> Typically, filesystem reads (with locked file-backed folios) could use >>> another bdev/meta inode to load some other I/Os (e.g. inode extent >>> metadata or caching compressed data), so the locking order will be: >> >> Which kernels need fixing. Do we expect that any code paths in 6.10 or >> earlier are vulnerable to this? > > I would suggest it goes back to the introduction of large folios, but > that's just a gut feeling based on absolutely no reading of code or > inspection of git history. According to 5dfab109d519 ("migrate_pages: batch _unmap and _move"), I think it's v6.3+. Yet I don't have more time to look info all history of batching migration, hoping Huang, Ying could give more hints on this. Thanks, Gao Xiang