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Date:   Thu, 15 Dec 2022 23:11:13 -0800
From:   Christoph Hellwig <hch@infradead.org>
To:     Ulrich Windl <Ulrich.Windl@rz.uni-regensburg.de>
Cc:     haowenchao@huawei.com, open-iscsi <open-iscsi@googlegroups.com>,
        linfeilong@huawei.com, liuzhiqiang26@huawei.com,
        jejb@linux.ibm.com, martin.petersen@oracle.com,
        michael.christie@oracle.com, Chris Leech <cleech@redhat.com>,
        Lee Duncan <lduncan@suse.com>, linux-kernel@vger.kernel.org,
        linux-scsi@vger.kernel.org
Subject: Re: Antw: [EXT] Re: [PATCH 0/2] scsi:donot skip lun if inquiry
 returns PQ=1 for all hosts
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On Thu, Dec 15, 2022 at 09:07:28AM +0100, Ulrich Windl wrote:
> Actusally I have no idea, but as a user of FC SAN systems I can remember a case when a storage system had to present a dummy LUN0 to enable hosts to find other LUNs (while LUN0 was never actually used). Maybe the client code was imperfect, I don't know.

Ignoring some of the well known LU bits that never really became
practically relevant, lun0 is needed to use the REPORT_LUNS command
to scane for the other logical units.  But unless the PQ says it
actually is a valid logic unit, we never add a sdev for it.