On 08/08/2017 06:11 PM, Bart Van Assche wrote:
> On Tue, 2017-08-08 at 12:06 -0400, Alan Stern wrote:
>> On Tue, 8 Aug 2017, Hannes Reinecke wrote:
>>> On 08/08/2017 05:25 PM, Alan Stern wrote:
>>>> On Tue, 8 Aug 2017, Hannes Reinecke wrote:
>>>>
>>>>> When checking the model and vendor string we need to use the
>>>>> minimum value of either string, otherwise we'll miss out on
>>>>> wildcard matches.
>>>>> And we should avoid matching anything with zero size as this
>>>>> match will be incorrect.
>>>>> Without this patch certain Hitachi arrays will not be presenting
>>>>> VPD pages correctly.
>>>>>
>>>>> Fixes: 5e7ff2c ("SCSI: fix new bug in scsi_dev_info_list string
>>>>> matching")
>>>>> Signed-off-by: Hannes Reinecke <[email protected]>
>>>>
>>>> This is very questionable. As described in commit b704f70ce200
>>>> ("SCSI:
>>>> fix bug in scsi_dev_info_list matching"), there are devices which
>>>> have
>>>> vendor or model strings of length 0, and there are entries in the
>>>> global device list like that too. With this patch, such devices and
>>>> such entries would never match anything.
>>>>
>>>> Also, the idea of using the minimum length of either string doesn't
>>>> sound right. It would allow a device with string "abc" to match an
>>>> entry in the list with string "abcd", which would be wrong.
>>>>
>>>> Suggestion:
>>>>
>>>> Allow a device string to match a list entry if the lengths
>>>> are equal or the list entry is shorter (this would be a
>>>> wildcard match), but not if the list entry is longer. Here
>>>> the device string length is after leading and trailing blanks
>>>> have been removed.
>>>>
>>>> As a corollary, allow an empty device string to match an empty
>>>> list entry but nothing else.
>>>>
>>>> Alan Stern
>>>>
>>>
>>> Well, so far we haven't encountered any of those devices.
>>
>> But what if we do in the future? The code should be correct for
>> anything.
>>
>>> I _have_ validated the patch with the known problematic inquiry strings,
>>> namely
>>>
>>> "HITACHI" "OPEN-V"
>>> "Inateck" " "
>>> " " "Scanner"
>>> "Promise" "STEX"
>>>
>>> and it gives the correct result for all of these.
>>
>> How can " " "Scanner" give the correct result? Oh, I see -- the
>> patch description and the code comment both say that empty strings
>> never match, but in fact they do -- you allow a match if either the
>> vendor or model string is empty, but not if they are both empty.
>>
>>> If you have any inquiry strings for which this does _not_ produce the
>>> correct result please let me know.
>>
>> What about "HITA" "OPEN-V"? Or "" "OPEN-V"? Both of these will match
>> the "HITACHI" "OPEN-" entry, but neither of them should.
>>
>> What about "ABCD" "Scanner"? This will match the " " "Scanner"
>> entry, but it shouldn't.
>
> Hello Hannes,
>
> Is there any case for which you think it is useful to perform a prefix match
> on the vendor name? What would break if the code for comparing the vendor
> name would be changed into an exact match (after having trimmed trailing
> whitespace)?
>
Haen't thought about this; but sure, it would simplify things here.
Plus the vendor string typically is short enough so that people don't
feel the need to abbreviate it.
I'll check.
Cheers,
Hannes
--
Dr. Hannes Reinecke Teamlead Storage & Networking
[email protected] +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)
