From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932918AbYDYXjO (ORCPT ); Fri, 25 Apr 2008 19:39:14 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758435AbYDYXi5 (ORCPT ); Fri, 25 Apr 2008 19:38:57 -0400 Received: from e3.ny.us.ibm.com ([32.97.182.143]:39175 "EHLO e3.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758567AbYDYXi4 (ORCPT ); Fri, 25 Apr 2008 19:38:56 -0400 Subject: Possible race between direct IO and JBD? From: Mingming Cao Reply-To: cmm@us.ibm.com To: akpm@linux-foundation.org Cc: pbadari@us.ibm.com, Jan Kara , linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20080306174209.GA14193@duck.suse.cz> References: <20080306174209.GA14193@duck.suse.cz> Content-Type: text/plain Organization: IBM Linux Technology Center Date: Fri, 25 Apr 2008 16:38:23 -0700 Message-Id: <1209166706.6040.20.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.8.0 (2.8.0-33.el5) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, While looking at a bug related to direct IO returns to EIO, after looking at the code, I found there is a window that try_to_free_buffers() from direct IO could race with JBD, which holds the reference to the data buffers before journal_commit_transaction() ensures the data buffers has reached to the disk. A little more detail: to prepare for direct IO, generic_file_direct_IO() calls invalidate_inode_pages2_range() to invalidate the pages in the cache before performaning direct IO. invalidate_inode_pages2_range() tries to free the buffers via try_to free_buffers(), but sometimes it can't, due to the buffers is possible still on some transaction's t_sync_datalist or t_locked_list waiting for journal_commit_transaction() to process it. Currently Direct IO simply returns EIO if try_to_free_buffers() finds the buffer is busy, as it has no clue that JBD is referencing it. Is this a known issue and expected behavior? Any thoughts? Mingming