From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:5166 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752544AbaKKUco (ORCPT ); Tue, 11 Nov 2014 15:32:44 -0500 Date: Tue, 11 Nov 2014 15:30:58 -0500 From: Chris Mason Subject: Re: kernel >= 3.16 saturates I/O endlessly and without reason To: Julien Muchembled CC: Message-ID: <1415737858.25389.0@mail.thefacebook.com> In-Reply-To: <54626D23.20701@jmuchemb.eu> References: <54626D23.20701@jmuchemb.eu> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Tue, Nov 11, 2014 at 3:10 PM, Julien Muchembled wrote: > Hello, > > I upgraded my kernel from 3.15.10 to 3.17.2 and after a while, btrfs > kworkers started to read/write data at maximum speed for hours > whereas I was doing nothing. So I rebooted with kernel 3.15.10 and > hopefully everything went back to normal. Later attempts to upgrade > to 3.16.7 or 3.17.2 showed the same issue, immediately at boot or > after a while. > > In order to investigate a little, I copied the partition and mounted > it in qemu (snapshot mode, with cow file in tmpfs, debian kernel > 3.16.7-2). I could see that btrfs always wrote the same ~8MB in loop. > qemu used all cpu and when I stopped it, it wrote 190G and the > generation number raised from 625955 to 853922. > > I dumped the FS with btrfs-image. The restored FS has the same issue > so I can send the image (78M) to anyone who would like to debug. Which mount options are you using? This sounds like something in autodefrag... -chris