From: Theodore Ts'o Subject: Re: [PATCH] ext4: fix deadlock of i_data_sem in ext4_mark_inode_dirty() Date: Thu, 4 Sep 2014 23:30:54 -0400 Message-ID: <20140905033054.GE1971@thunk.org> References: <20140905015935.GF4364@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Ext4 Developers List , Andreas Dilger , Jan Kara To: Li Xi Return-path: Received: from imap.thunk.org ([74.207.234.97]:39200 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752812AbaIEDw4 (ORCPT ); Thu, 4 Sep 2014 23:52:56 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: 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. 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.) Regards, - Ted