Re: [PATCH 0/2] scsi:donot skip lun if inquiry returns PQ=1 for all hosts

[Wenchao Hao <haowenchao@huawei.com>]

On 2022/12/23 23:54, Christoph Hellwig wrote:
> On Fri, Dec 16, 2022 at 07:41:26PM +0800, Wenchao Hao wrote:
>> For nothing, I want the iscsi_tcp transport do not skip PQ=1 default
>> as what it did before commit 948e922fc4461 ("scsi: core: map PQ=1,
>> PDT=other values to SCSI_SCAN_TARGET_PRESENT").
> 
> Well, that commit was very much intentional and is now three an a half
> years old, so we've not just going to partially revert it on a
> per-transport basis when it is in no way transport related.
> 
> If you can come up with a good enough rationale we could do the
> sysfs override, but so far the reason mostly seems to be "I want"
> and not anctual explanation of why it is useful.
> .


Sorry, I did not describe in detail.

Here is the reason of my patches.

1. The SPC did not tell PQ=1 means the addressed lun is invalid explicitly.
2. scsi_bus_match() would prevent luns with PQ=1 be handled by any scsi
   drivers, so the only influence if we do not skip luns with PQ=1 is we
   would add an scsi_device and an sg device.

The reason I force a specific behavior for iSCSI:

1. This issue is occurred with iSCSI, it means there are scenarios where
   targets would return PQ=1 for an valid LUN which should not be skipped.
2. The changes for iSCSI could be tested

I did not change other transports' behavior is because I do not know if PQ=1
would be returned, and I do not have the related environment. If other
transports like adaptec raid also needs these changes, they can override
the default value by other patches.

Thanks.