From: Andrew Morton Subject: Re: A unresponsive file system can hang all I/O in the system on linux-2.6.23-rc6 (dirty_thresh problem?) Date: Fri, 28 Sep 2007 11:04:45 -0700 Message-ID: <20070928110445.69e687c0.akpm@linux-foundation.org> References: <20070927235034.ae7bd73d.akpm@linux-foundation.org> <10659.1190986132@lwn.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Cc: Chakri n , linux-pm , nfs@lists.sourceforge.net, lkml , Peter Zijlstra To: corbet@lwn.net (Jonathan Corbet) Return-path: In-Reply-To: <10659.1190986132@lwn.net> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-pm-bounces@lists.linux-foundation.org Errors-To: linux-pm-bounces@lists.linux-foundation.org List-ID: On Fri, 28 Sep 2007 07:28:52 -0600 corbet@lwn.net (Jonathan Corbet) wrote: > Andrew wrote: > > It's unrelated to the actual value of dirty_thresh: if the machine fills up > > with dirty (or unstable) NFS pages then eventually new writers will block > > until that condition clears. > > > > 2.4 doesn't have this problem at low levels of dirty data because 2.4 > > VFS/MM doesn't account for NFS pages at all. > > Is it really NFS-related? I was trying to back up my 2.6.23-rc8 system > to an external USB drive the other day when something flaked and the > drive fell off the bus. That, too, was sufficient to wedge the entire > system, even though the only thing which needed the dead drive was one > rsync process. It's kind of a bummer to have to hit the reset button > after the failure of (what should be) a non-critical piece of hardware. > > Not that I have a fix to propose...:) > That's a USB bug, surely. What should happen is that the kernel attempts writeback, gets an IO error and then your data gets lost.