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Date:   Sun, 18 Dec 2022 15:37:40 -0600
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Subject: Re: [PATCH 1/2] scsi:core:Add sysfs interface to control if skip lun
 with PQ=1
To:     Wenchao Hao <haowenchao@huawei.com>,
        "Martin K . Petersen" <martin.petersen@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
Cc:     linux-kernel@vger.kernel.org, liuzhiqiang26@huawei.com,
        linfeilong@huawei.com
References: <20221214070846.1808300-1-haowenchao@huawei.com>
 <20221214070846.1808300-2-haowenchao@huawei.com>
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From:   Mike Christie <michael.christie@oracle.com>
In-Reply-To: <20221214070846.1808300-2-haowenchao@huawei.com>
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On 12/14/22 1:08 AM, 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.
> 
> We want the lun0 to be mapped to an sg device in initiator, so we can
> probe luns of target based on lun0.

What do you want to do exactly? Is the idea with your patch we would create
an sg device, then in userpsace you would do some scan related commands. If
you find devices then you use sysfs to have scsi-ml scan/add a specific device
like

echo 5 0 0 8 > host5/scan

?

It's not really clear to me why you need the sg device, and can't just do?

echo - - - > .../hostN/scan

? Do you only want to add specific devices like you are doing some sort of
LUN masking on the initiator side?

Is the issue that you need the sg device there, so you can detect when a device
is no longer present on the target and then you will have userspace remove the
device via the sysfs delete file?