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 DF9B8C433EF for ; Fri, 26 Nov 2021 02:32:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351952AbhKZCfV (ORCPT ); Thu, 25 Nov 2021 21:35:21 -0500 Received: from mail.kernel.org ([198.145.29.99]:47710 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1357635AbhKZCdU (ORCPT ); Thu, 25 Nov 2021 21:33:20 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id EF78A61139; Fri, 26 Nov 2021 02:30:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1637893808; bh=jx7FhoL2r/nh8GzjL+YOzztn+6+ZcFtosRvBUb3cDuI=; h=From:To:Cc:Subject:Date:From; b=uuWw4TA/tbiAATVbBo2JGx6YvCYFs0Q2RyNd7UB39bw8T9dUBHr2zYjk/x+nGql5M BsNX4CUysGSWhzPjzuwJyj1RYlJhkzzh02Me1PUcC2gXijR5P7urNKVfLjRNIKewYk DLQ1gxsUcoAOtN7LI85tYmH5oxfXvt+5dqp7ohmu1xeqbn3hSzt7biQ8Gg7J4ctzID bC2Ksaow++pN3xEOQbyhr+bk7jRoyxV543+Uhx4appk6u2gTuxQw/cl+8GRe5SngKU h0pcF5tfkGDY2utOyvqa4Fdo5CkkvhoeQyUy9BdIs1rIEuZTiLGH4qY8kW5MywwVSU VqKs/xhook/gw== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Chao Yu , Yi Zhuang , Jaegeuk Kim , Sasha Levin , linux-f2fs-devel@lists.sourceforge.net Subject: [PATCH AUTOSEL 5.15 1/7] f2fs: quota: fix potential deadlock Date: Thu, 25 Nov 2021 21:30:00 -0500 Message-Id: <20211126023006.440839-1-sashal@kernel.org> X-Mailer: git-send-email 2.33.0 MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Chao Yu [ Upstream commit a5c0042200b28fff3bde6fa128ddeaef97990f8d ] 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: Sasha Levin --- fs/f2fs/checkpoint.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c index 83e9bc0f91ffd..7b02827242312 100644 --- a/fs/f2fs/checkpoint.c +++ b/fs/f2fs/checkpoint.c @@ -1162,7 +1162,8 @@ static bool __need_flush_quota(struct f2fs_sb_info *sbi) 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)) { -- 2.33.0