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=-2.1 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, USER_AGENT_MUTT 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 F3375C6778A for ; Sun, 22 Jul 2018 22:08:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9B53C20854 for ; Sun, 22 Jul 2018 22:08:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=thunk.org header.i=@thunk.org header.b="qwEiRcvt" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9B53C20854 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=mit.edu 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 S1730928AbeGVXG6 (ORCPT ); Sun, 22 Jul 2018 19:06:58 -0400 Received: from imap.thunk.org ([74.207.234.97]:43620 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730611AbeGVXG6 (ORCPT ); Sun, 22 Jul 2018 19:06:58 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=thunk.org; s=ef5046eb; h=In-Reply-To:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=qVT9DsJUy3tWv6r2oWR9UxkTK51n9zJmFQaz3VqN2js=; b=qwEiRcvttzAxm6ip0psZj18ksE 9mJW+FPHr1BZy2FknJNayu+bwBgUcRI6b4Da6qVk6AyPDBpMpwGyaxtnF2ME1lFG750qGLwvBCgUs Nem4yNrBmFgdHxPxtTcSshli+pHzEt2nCTrvOF5btruhbQwGQ2/QhKNcxh5XOoOtI5P0=; Received: from root (helo=callcc.thunk.org) by imap.thunk.org with local-esmtp (Exim 4.89) (envelope-from ) id 1fhMWy-0005Sb-Uc; Sun, 22 Jul 2018 22:08:45 +0000 Received: by callcc.thunk.org (Postfix, from userid 15806) id AF7AB7A6463; Sun, 22 Jul 2018 18:08:41 -0400 (EDT) Date: Sun, 22 Jul 2018 18:08:41 -0400 From: "Theodore Y. Ts'o" To: Junil Lee Cc: adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, junil0814.lee@MIT.EDU Subject: Re: [PATCH] ext4: remove abnormal set for I_DATA_SEM subclass Message-ID: <20180722220841.GA3358@thunk.org> Mail-Followup-To: "Theodore Y. Ts'o" , Junil Lee , adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, junil0814.lee@MIT.EDU References: <1531123108-45918-1-git-send-email-junil0814.lee@lge.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1531123108-45918-1-git-send-email-junil0814.lee@lge.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: tytso@thunk.org X-SA-Exim-Scanned: No (on imap.thunk.org); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 09, 2018 at 04:58:28PM +0900, Junil Lee wrote: > The -EBUSY return value of dquot_enable() function means that just > want to update flags. If some users make a duplicate request to update > flags, lockdep could catch the false positive casued by needing to > allocate a quota block from inside ext4_map_blocks(), while holding > i_data_sem for a data inode. This results in this complaint: > > CPU0 CPU1 > ---- ---- > lock(&s->s_dquot.dqio_mutex); > lock(&ei->i_data_sem); > lock(&s->s_dquot.dqio_mutex); > lock(&ei->i_data_sem); How does this happen in practice? The function ext4_quota_enable() is only called by ext4_enable_quotas(), and I don't see the code path where this would happen. And if it does it would be resulting an EXT4-fs warning message getting printing indicating that a failure to enable quotas with an error of EBUSY. So how does this happen that "users would make a duplicate request to update flags"? - Ted