From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vladislav Bolkhovitin Subject: Re: [PATCH 26/30] ext4: do not send discards as barriers Date: Thu, 02 Sep 2010 22:46:35 +0400 Message-ID: <4C7FF10B.2040102@vlnb.net> References: <1282751267-3530-27-git-send-email-tj@kernel.org> <20100825155842.GA3229@lst.de> <20100825160032.GC3229@lst.de> <4C753D75.2010305@kernel.org> <20100825200223.GE2738@quack.suse.cz> <4C76250B.6060800@kernel.org> <20100827173147.GA12374@quack.suse.cz> <20100830202034.GB12226@quack.quadriga.com> <4C7C170D.9090409@vlnb.net> <20100830210205.GD12226@quack.quadriga.com> <4C7CD18B.2060608@panasas.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4C7CD18B.2060608@panasas.com> Sender: linux-ide-owner@vger.kernel.org To: Boaz Harrosh Cc: Jan Kara , Jeff Moyer , Tejun Heo , Christoph Hellwig , jaxboe@fusionio.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-scsi@vger.kernel.org, linux-ide@vger.kernel.org, linux-raid@vger.kernel.org, James.Bottomley@suse.de, tytso@mit.edu, chris.mason@oracle.com, swhiteho@redhat.com, konishi.ryusuke@lab.ntt.co.jp, dm-devel@redhat.com, rwheeler@redhat.com, hare@suse.de, neilb@suse.de, rusty@rustcorp.com.au, mst@redhat.com, jeremy@goop.org, snitzer@redhat.com, k-ueda@ct.jp.nec.com, Christoph Hellwig List-Id: dm-devel.ids Boaz Harrosh, on 08/31/2010 01:55 PM wrote: >>>>>> An update: I've set up an ext4 barrier testing in KVM - run fsstress, >>>>>> kill KVM at some random moment and check that the filesystem is consistent >>>>>> (kvm is run in cache=writeback mode to simulate disk cache). About 70 runs >>>>> >>>>> But doesn't your "disk cache" survive the "power cycle" of your guest? >>>> Yes, you're right. Thinking about it now the test setup was wrong because >>>> it didn't refuse writes to the VM's data partition after the moment I >>>> killed KVM. Thanks for catching this. I will probably have to use the fault >>>> injection on the host to disallow writing the device at a certain moment. >>>> Or does somebody have a better option? >>> >>> Have you considered to setup a second box as an iSCSI target (e.g. >>> with iSCSI-SCST)? With it killing the connectivity is just a matter >>> of a single iptables command + a lot more options. > > Still same problem no? the data is still cached on the backing store device > how do you trash the cached data? If you need to kill the device's cache you can crash/panic/power off the target. That also can be well scriptable. Vlad