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Message-ID: <57c12317-c229-8cbe-b3d2-d799ea5f554c@huawei.com>
Date:   Thu, 15 Dec 2022 17:09:31 +0800
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Subject: Re: [PATCH 0/2] scsi:donot skip lun if inquiry returns PQ=1 for all
 hosts
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To:     Christoph Hellwig <hch@infradead.org>
CC:     "Martin K . Petersen" <martin.petersen@oracle.com>,
        Mike Christie <michael.christie@oracle.com>,
        "James E . J . Bottomley" <jejb@linux.ibm.com>,
        Lee Duncan <lduncan@suse.com>, Chris Leech <cleech@redhat.com>,
        <open-iscsi@googlegroups.com>, <linux-scsi@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <liuzhiqiang26@huawei.com>,
        <linfeilong@huawei.com>
References: <20221214070846.1808300-1-haowenchao@huawei.com>
 <Y5rHX95Vvl1aLhbp@infradead.org>
From:   Wenchao Hao <haowenchao@huawei.com>
In-Reply-To: <Y5rHX95Vvl1aLhbp@infradead.org>
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On 2022/12/15 15:06, Christoph Hellwig wrote:
> On Wed, Dec 14, 2022 at 03:08:44PM +0800, Wenchao Hao wrote:
>> When iSCSI initiator logged in target, the target attached none valid
>> lun but lun0. lun0 is not an valid disk, while it would response
>> inquiry command with PQ=1 and other general scsi commands like probe lun.
>> The others luns of target is added/removed dynamicly.
> 
> I can't find any special casing of LUN0 in RFC7144, can you clarify
> where you think that treats LUN0 any differently than other transports?
> .
This is not described in RFC7144. The sense described above
aims to tell that a dummy lun is useful.

In my opinion, if the addressed lun still response the
inquiry and other commands, we should not skip it,
maybe let the scsi drivers like sd/st/sg to determine
how to handle this lun accordint to the PQ value.

As discussed in following mail, another drivers would
be broken too.

https://lore.kernel.org/linux-scsi/CA+PODjqrRzyJnOKoabMOV4EPByNnL1LgTi+QAKENP3NwUq5YCw@mail.gmail.com/

The key point of my patch is to add one way to map
dummy lun to an sg device.