From mboxrd@z Thu Jan 1 00:00:00 1970 From: torn5 Subject: Ext4 and scsi commands resubmission Date: Tue, 28 Dec 2010 11:41:58 +0100 Message-ID: <4D19BEF6.5010007@shiftmail.org> Mime-Version: 1.0 Content-Type: text/plain; format=flowed; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from blade3.isti.cnr.it ([194.119.192.19]:52123 "EHLO BLADE3.ISTI.CNR.IT" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753143Ab0L1Km3 (ORCPT ); Tue, 28 Dec 2010 05:42:29 -0500 Received: from SCRIPT-SPFWL-DAEMON.mx.isti.cnr.it by mx.isti.cnr.it (PMDF V6.5-x5 #31825) id <01NVYB5L5AZ4NG4OI5@mx.isti.cnr.it> for linux-scsi@vger.kernel.org; Tue, 28 Dec 2010 11:41:54 +0100 (MET) Received: from conversionlocal.isti.cnr.it by mx.isti.cnr.it (PMDF V6.5-x5 #31825) id <01NVYB5KS2GWNG4JSC@mx.isti.cnr.it> for linux-scsi@vger.kernel.org; Tue, 28 Dec 2010 11:41:51 +0100 (MET) Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: linux-ext4@vger.kernel.org, "linux-scsi@vger.kernel.org" Hello all, in open-iscsi, when network connectivity is lost, scsi commands that were in-flight at the moment of disconnection are failed to the SCSI layer. These get resubmitted up to 5 times by the SCSI layer (or so is written in the open-iscsi docs) and after that they are held in the queue (device "blocked") until the network connection is restored. Now the question is: when SCSI resubmits commands to a device, I suppose they go to the end of the queue for the device, and not at the head like they were. Am I right? How do filesystems, and in particular ext4, react to that? I suppose the ordering goes awry, barriers cannot succeed in this way, especially if they were submitted as real SCSI barriers (i.e. without using flush + command + flush workaround) Thank you