From: Tao Ma Subject: Re: [URGENT PATCH] ext4: fix potential deadlock in ext4_evict_inode() Date: Fri, 26 Aug 2011 17:03:14 +0800 Message-ID: <4E576152.9060405@tao.ma> References: <20110826073507.GZ3162@dastard> <20110826084403.GA3162@dastard> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Theodore Ts'o , Jiaying Zhang , linux-ext4@vger.kernel.org To: Dave Chinner Return-path: Received: from oproxy4-pub.bluehost.com ([69.89.21.11]:58752 "HELO oproxy4-pub.bluehost.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753592Ab1HZJDW (ORCPT ); Fri, 26 Aug 2011 05:03:22 -0400 In-Reply-To: <20110826084403.GA3162@dastard> Sender: linux-ext4-owner@vger.kernel.org List-ID: On 08/26/2011 04:44 PM, Dave Chinner wrote: > On Fri, Aug 26, 2011 at 05:35:07PM +1000, Dave Chinner wrote: >> On Thu, Aug 25, 2011 at 11:33:44PM -0400, Theodore Ts'o wrote: >>> >>> Note: this will probably need to be sent to Linus as an emergency >>> bugfix ASAP, since it was introduced in 3.1-rc1, so it represents a >>> regression. >> >> It doesn't appear to be a bug. All of the new ext4 lockdep reports >> in 3.1 I've seen (except for the mmap_sem/i_mutex one) are false >> positives.... > > While the lockdep report is false positive, I agree that your > change is the right fix to make - the IO completions are already > queued on the workqueue, so they don't need to be flushed to get > them to complete. All that needs to be done is call > ext4_ioend_wait() for them to complete, and that gets rid of the > i_mutex altogether. (*) ext4_ioend_wait can't work here for a nasty bug. Please see the commit log of 2581fdc8. Thanks Tao