From: Li Xi Subject: Re: [PATCH] ext4: fix deadlock of i_data_sem in ext4_mark_inode_dirty() Date: Fri, 5 Sep 2014 12:44:49 +0800 Message-ID: References: <20140905015935.GF4364@thunk.org> <20140905033054.GE1971@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Cc: Ext4 Developers List , Andreas Dilger , Jan Kara To: "Theodore Ts'o" Return-path: Received: from mail-ie0-f171.google.com ([209.85.223.171]:43664 "EHLO mail-ie0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750711AbaIEEou (ORCPT ); Fri, 5 Sep 2014 00:44:50 -0400 Received: by mail-ie0-f171.google.com with SMTP id rp18so13119660iec.30 for ; Thu, 04 Sep 2014 21:44:49 -0700 (PDT) In-Reply-To: <20140905033054.GE1971@thunk.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Fri, Sep 5, 2014 at 11:30 AM, Theodore Ts'o wrote: > On Fri, Sep 05, 2014 at 10:29:16AM +0800, Li Xi wrote: >> On Fri, Sep 5, 2014 at 9:59 AM, Theodore Ts'o wrote: >> > On Thu, Sep 04, 2014 at 04:49:58PM +0800, Li Xi wrote: >> >> There are multiple places where ext4_mark_inode_dirty() is called holding >> >> write lock of EXT4_I(inode)->i_data_sem. However, if >> >> ext4_mark_inode_dirty() needs to expand inode size, this will cause >> >> deadlock when ext4_xattr_block_set() tries to get read lock of >> >> EXT4_I(inode)->i_data_sem. >> > >> > This was with inline data enabled, right? >> I hit this problem when starting a kernel with project quota support for ext4. >> The ext4 file system was not formated with project quota feature so it tried >> to extend the space for project ID. And this problem happened every time >> when the kernel was rebooted. Inline data was not enable on that file >> system. I am not sure whether this problem will happen under other >> circumstances. :) > > I'm not understanding why expanding the inode size would result in > needing to call ext4_xattr_block_set. Was that becuse you were > storing the project quota in the xattr? I'm just trying to understand > the context. Yeah, you are right. The problem happened when the project ID was saved as xattr. And I can't reproduce the same problem with the new patches. > > Please also note that a recent set of patches (sent to the ext4 list > and in the ext4 git tree) has removed the need for taking i_data_sem > in xattr.c: > > http://patchwork.ozlabs.org/patch/385347 > http://patchwork.ozlabs.org/patch/385348 > http://patchwork.ozlabs.org/patch/385346 > > (It's the 2/3 patch that removes taking i_data_sem read lock in xattr.c.) > Great! Please ignore this patch since it won't be a problem any more. Regards, - Li Xi