From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Reinecke Subject: Re: [PATCH 2/5] scsi_scan: Restrict sequential scan to 256 LUNs Date: Fri, 28 Mar 2014 01:22:15 -0700 Message-ID: <53353137.2050603@suse.de> References: <1386673515-87133-1-git-send-email-hare@suse.de> <1386673515-87133-3-git-send-email-hare@suse.de> <20140327144926.GB16958@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from cantor2.suse.de ([195.135.220.15]:53538 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751274AbaC1IWR (ORCPT ); Fri, 28 Mar 2014 04:22:17 -0400 In-Reply-To: <20140327144926.GB16958@infradead.org> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Christoph Hellwig Cc: James Bottomley , linux-scsi@vger.kernel.org On 03/27/2014 07:49 AM, Christoph Hellwig wrote: > On Tue, Dec 10, 2013 at 12:05:12PM +0100, Hannes Reinecke wrote: >> Sequential scan for more than 256 LUNs is very fragile as >> LUNs might not be numbered sequentially after that point. >> >> SAM revisions later than SCSI-3 impose a structure on >> LUNs larger than 256, making LUN numbers between 256 >> and 16384 illegal. >> SCSI-3, however allows for plain 64-bit numbers with >> no internal structure. >> >> So restrict sequential LUN scan to 256 LUNs and add a >> new blacklist flag 'BLIST_SCSI3LUN' to scan up to >> max_lun devices. > > What do you need the blacklist flag for? There's no user of it, and > supporting that many LUNs without REPORT LUNS support doesn't sound v= ery > practical anyway. > Because there is no guarantee that pre-SCSI-3 devices (or devices=20 announcing to be pre-SCSI-3) will not allow to scan more than 256 devic= es. Thinking of older Symmetrix here with their weird 'SPC-3 masking as=20 SCSI-2' habit. Also currently we're allowing to scan beyond 256 without any=20 restrictions there might be installations out there which rely on this=20 behaviour. Hence this flag. Cheers, Hannes --=20 Dr. Hannes Reinecke zSeries & Storage hare@suse.de +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N=FCrnberg GF: J. Hawn, J. Guild, F. Imend=F6rffer, HRB 16746 (AG N=FCrnberg) -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html