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 X-Spam-Level: X-Spam-Status: No, score=-3.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,T_DKIMWL_WL_HIGH,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2B3A1ECDFB0 for ; Sun, 15 Jul 2018 01:10:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B9DFD208CC for ; Sun, 15 Jul 2018 01:10:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="BeWtHXaW" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B9DFD208CC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732248AbeGOBbS (ORCPT ); Sat, 14 Jul 2018 21:31:18 -0400 Received: from mail.kernel.org ([198.145.29.99]:51624 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731952AbeGOBbS (ORCPT ); Sat, 14 Jul 2018 21:31:18 -0400 Received: from localhost (unknown [104.132.152.71]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 304342089F; Sun, 15 Jul 2018 01:10:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1531617020; bh=IYWx7Ph0MuJdinicKPgiJfi/1xdAuDV1VE/s7EL3w98=; h=From:To:Cc:Subject:Date:From; b=BeWtHXaWUgVhw47OaI8Vk1qbvlBURk2nqMUABTaNBN+4DarodPTbND3BhpSxpipjN NI6Ek13Db0llVjulBFc3PNivBSP2CqdPA+aIdoDs+av5ySFKUFgKONlQNhIc6C6mCo 6KXByxPr5SeP/VkAe1vanjCdVJbA76EMiz53QUzM= From: Jaegeuk Kim To: linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net Cc: Jaegeuk Kim Subject: [PATCH] f2fs: avoid potential deadlock in f2fs_sbi_store Date: Sun, 15 Jul 2018 10:10:17 +0900 Message-Id: <20180715011017.11237-1-jaegeuk@kernel.org> X-Mailer: git-send-email 2.17.0.441.gb46fe60e1d-goog Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [ 155.018460] ====================================================== [ 155.021431] WARNING: possible circular locking dependency detected [ 155.024339] 4.18.0-rc3+ #5 Tainted: G OE [ 155.026879] ------------------------------------------------------ [ 155.029783] umount/2901 is trying to acquire lock: [ 155.032187] 00000000c4282f1f (kn->count#130){++++}, at: kernfs_remove+0x1f/0x30 [ 155.035439] [ 155.035439] but task is already holding lock: [ 155.038892] 0000000056e4307b (&type->s_umount_key#41){++++}, at: deactivate_super+0x33/0x50 [ 155.042602] [ 155.042602] which lock already depends on the new lock. [ 155.042602] [ 155.047465] [ 155.047465] the existing dependency chain (in reverse order) is: [ 155.051354] [ 155.051354] -> #1 (&type->s_umount_key#41){++++}: [ 155.054768] f2fs_sbi_store+0x61/0x460 [f2fs] [ 155.057083] kernfs_fop_write+0x113/0x1a0 [ 155.059277] __vfs_write+0x36/0x180 [ 155.061250] vfs_write+0xbe/0x1b0 [ 155.063179] ksys_write+0x55/0xc0 [ 155.065068] do_syscall_64+0x60/0x1b0 [ 155.067071] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 155.069529] [ 155.069529] -> #0 (kn->count#130){++++}: [ 155.072421] __kernfs_remove+0x26f/0x2e0 [ 155.074452] kernfs_remove+0x1f/0x30 [ 155.076342] kobject_del.part.5+0xe/0x40 [ 155.078354] f2fs_put_super+0x12d/0x290 [f2fs] [ 155.080500] generic_shutdown_super+0x6c/0x110 [ 155.082655] kill_block_super+0x21/0x50 [ 155.084634] kill_f2fs_super+0x9c/0xc0 [f2fs] [ 155.086726] deactivate_locked_super+0x3f/0x70 [ 155.088826] cleanup_mnt+0x3b/0x70 [ 155.090584] task_work_run+0x93/0xc0 [ 155.092367] exit_to_usermode_loop+0xf0/0x100 [ 155.094466] do_syscall_64+0x162/0x1b0 [ 155.096312] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 155.098603] [ 155.098603] other info that might help us debug this: [ 155.098603] [ 155.102418] Possible unsafe locking scenario: [ 155.102418] [ 155.105134] CPU0 CPU1 [ 155.107037] ---- ---- [ 155.108910] lock(&type->s_umount_key#41); [ 155.110674] lock(kn->count#130); [ 155.113010] lock(&type->s_umount_key#41); [ 155.115608] lock(kn->count#130); Signed-off-by: Jaegeuk Kim --- fs/f2fs/sysfs.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c index 5344e21853b2..bca1236fd6fa 100644 --- a/fs/f2fs/sysfs.c +++ b/fs/f2fs/sysfs.c @@ -287,8 +287,10 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a, bool gc_entry = (!strcmp(a->attr.name, "gc_urgent") || a->struct_type == GC_THREAD); - if (gc_entry) - down_read(&sbi->sb->s_umount); + if (gc_entry) { + if (!down_read_trylock(&sbi->sb->s_umount)) + return -EAGAIN; + } ret = __sbi_store(a, sbi, buf, count); if (gc_entry) up_read(&sbi->sb->s_umount); -- 2.17.0.441.gb46fe60e1d-goog