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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DF45AC433EF for ; Mon, 10 Jan 2022 07:31:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239508AbiAJHbf (ORCPT ); Mon, 10 Jan 2022 02:31:35 -0500 Received: from dfw.source.kernel.org ([139.178.84.217]:38798 "EHLO dfw.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240238AbiAJH3c (ORCPT ); Mon, 10 Jan 2022 02:29:32 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 607AA611B7; Mon, 10 Jan 2022 07:29:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 43978C36AE9; Mon, 10 Jan 2022 07:29:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1641799771; bh=C3+AgHOGPU/JduDV9eThrDNKId/d6U1n4jEsZ2VuWJI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bCd6g9REulTuB5NyjytX/3iyEOzjBJK1bYspdDUam1PhNrrkehRyGZaq+R8pvRgfI egkv6Bs/Kej4eEBKqiRzDjpZnYe3v8ZBalOBgp+FWOE9baN2ejI9IY+s3BK07e0giX oybqnISVMClTVk6ICTxtkws63K3a4NEMk6Owhk/Q= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Yi Zhuang , Chao Yu , Jaegeuk Kim Subject: [PATCH 5.10 01/43] f2fs: quota: fix potential deadlock Date: Mon, 10 Jan 2022 08:22:58 +0100 Message-Id: <20220110071817.386947432@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220110071817.337619922@linuxfoundation.org> References: <20220110071817.337619922@linuxfoundation.org> User-Agent: quilt/0.66 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Chao Yu commit a5c0042200b28fff3bde6fa128ddeaef97990f8d upstream. As Yi Zhuang reported in bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=214299 There is potential deadlock during quota data flush as below: Thread A: Thread B: f2fs_dquot_acquire down_read(&sbi->quota_sem) f2fs_write_checkpoint block_operations f2fs_look_all down_write(&sbi->cp_rwsem) f2fs_quota_write f2fs_write_begin __do_map_lock f2fs_lock_op down_read(&sbi->cp_rwsem) __need_flush_qutoa down_write(&sbi->quota_sem) This patch changes block_operations() to use trylock, if it fails, it means there is potential quota data updater, in this condition, let's flush quota data first and then trylock again to check dirty status of quota data. The side effect is: in heavy race condition (e.g. multi quota data upaters vs quota data flusher), it may decrease the probability of synchronizing quota data successfully in checkpoint() due to limited retry time of quota flush. Reported-by: Yi Zhuang Signed-off-by: Chao Yu Signed-off-by: Jaegeuk Kim Signed-off-by: Greg Kroah-Hartman --- fs/f2fs/checkpoint.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/fs/f2fs/checkpoint.c +++ b/fs/f2fs/checkpoint.c @@ -1147,7 +1147,8 @@ static bool __need_flush_quota(struct f2 if (!is_journalled_quota(sbi)) return false; - down_write(&sbi->quota_sem); + if (!down_write_trylock(&sbi->quota_sem)) + return true; if (is_sbi_flag_set(sbi, SBI_QUOTA_SKIP_FLUSH)) { ret = false; } else if (is_sbi_flag_set(sbi, SBI_QUOTA_NEED_REPAIR)) {