From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Anderson Subject: Re: [PATCH 7/9] scsi_dh: Add support for SDEV_PASSIVE Date: Tue, 5 Feb 2008 13:56:57 -0800 Message-ID: <20080205215657.GA20963@linux.vnet.ibm.com> References: <20080124003010.18871.84095.sendpatchset@localhost.localdomain> <20080124003203.18871.52040.sendpatchset@localhost.localdomain> <1202151498.3096.84.camel@localhost.localdomain> <1202156151.13537.14.camel@linuxchandra> <1202156914.3096.112.camel@localhost.localdomain> <47A8C14A.3030207@cs.wisc.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from e1.ny.us.ibm.com ([32.97.182.141]:38466 "EHLO e1.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756707AbYBEV5R (ORCPT ); Tue, 5 Feb 2008 16:57:17 -0500 Received: from d01relay04.pok.ibm.com (d01relay04.pok.ibm.com [9.56.227.236]) by e1.ny.us.ibm.com (8.13.8/8.13.8) with ESMTP id m15LvGLI010232 for ; Tue, 5 Feb 2008 16:57:16 -0500 Received: from d01av04.pok.ibm.com (d01av04.pok.ibm.com [9.56.224.64]) by d01relay04.pok.ibm.com (8.13.8/8.13.8/NCO v8.7) with ESMTP id m15LvGHa277270 for ; Tue, 5 Feb 2008 16:57:16 -0500 Received: from d01av04.pok.ibm.com (loopback [127.0.0.1]) by d01av04.pok.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id m15LvF6W030472 for ; Tue, 5 Feb 2008 16:57:16 -0500 Content-Disposition: inline In-Reply-To: <47A8C14A.3030207@cs.wisc.edu> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Mike Christie Cc: James Bottomley , sekharan@us.ibm.com, dm-devel@redhat.com, linux-scsi@vger.kernel.org, jens.axboe@oracle.com Mike Christie wrote: > When IO is sent to a path that cannot execute IO optimally, the scsi hw > handler hook for sense processing (see rdac_check_sense in "[PATCH 8/9] > scsi_dh: add lsi rdac device handler" and the scsi_error.c hook in in > "scsi_dh: add skeleton for SCSI Device Handlers") will detect this and set > the state to passive so future IO is not execute on the path > (SG_IO/passthrough is allowed). > > I am not sure about alternatives. If we just exported the port access state > in sysfs, but did not fail IO from scsi_prep_state_check, then the users > could still check the state before sending IO. Would it be horrible to > convert apps to do this? The majority of the boot up delays is caused by the kernel partition scanning and other kernel init code (Chandra please correct if that is not true). Sysfs attributes would not help here. One option maybe to add handling of the newer BLKERR_ codes in the generators of IO or some similar solution with a rollout possibly focused at the top generators of IO. A number of user apps like lvm scanning that execute media access commands already have filter capability to filter devices that one does not want to scan. Another class of device scanners just use inquiries which are not effected by the passive state (though some could probably use udevinfo and reduce the amount of repeated SCSI inquiries execute on the system. -andmike -- Michael Anderson andmike@linux.vnet.ibm.com