On Fri, Aug 26, 2011 at 05:03:14PM +0800, Tao Ma wrote: > 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. Unless I'm missing something, the described race with ext4_truncate() flushing completions without the i_mutex lock held cannot occur if you've already waited for all pending completions to drain by calling ext4_ioend_wait().... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
