From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bart Van Assche Subject: Re: [PATCHv3] scsi: disable automatic target scan Date: Sun, 20 Mar 2016 18:24:26 -0700 Message-ID: <56EF4D4A.6050000@sandisk.com> References: <1458200385-32088-1-git-send-email-hare@suse.de> <56EC797A.8000104@sandisk.com> <56ED6DB1.1050202@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-by2on0092.outbound.protection.outlook.com ([207.46.100.92]:14496 "EHLO na01-by2-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751155AbcCUBYc (ORCPT ); Sun, 20 Mar 2016 21:24:32 -0400 In-Reply-To: <56ED6DB1.1050202@suse.de> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Hannes Reinecke , "Martin K. Petersen" Cc: Christoph Hellwig , James Bottomley , linux-scsi@vger.kernel.org On 03/19/16 08:18, Hannes Reinecke wrote: > On 03/18/2016 10:56 PM, Bart Van Assche wrote: >> On 03/17/2016 12:39 AM, Hannes Reinecke wrote: >>> On larger installations it is useful to disable automatic LUN >>> scanning, and only add the required LUNs via udev rules. >>> This can speed up bootup dramatically. >>> >>> This patch introduces a new scan module parameter value 'manual', >>> which works like 'none', but can be overriden by setting the 'rescan' >>> value from scsi_scan_target to 'SCSI_SCAN_MANUAL'. >>> And it updates all relevant callers to set the 'rescan' value >>> to 'SCSI_SCAN_MANUAL' if invoked via the 'scan' option in sysfs. >> >> Hello Hannes, >> >> Will setting scsi_scan_type to 'manual' allow a system to boot from a >> SCSI disk? If not, are there alternatives to this approach? Would it be >> a valid alternative to e.g. introduce a new threshold parameter such >> that only LUN numbers below this threshold are scanned during boot? >> > I have a patch for dracut, which will generate udev rules for all > devices required for mounting the root fs. > Once the system is booted properly I've got another patch for systemd > which switches back to 'normal' scanning (ie by writing 'sync' into > /sys/modules/scsi_mod/parameters/scan) and rescan all scsi hosts. > > With that there's no need to have any arbitrary limits; only the > necessary devices are enabled during boot. Hello Hannes, That sounds like a really interesting approach. Will this approach also work if the SCSI host and/or LUN numbers change during a reboot? Thanks, Bart.