linux-kernel - Re: [PATCH] scsi: core: Add BLIST_NO_ASK_VPD

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Message-ID: <11a582f0-723c-95e1-0e44-0a19e1a8a9a8@acm.org>
Date:   Sun, 2 Oct 2022 14:16:19 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Lee Duncan <leeman.duncan@...il.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Lee Duncan <lduncan@...e.com>, Martin Wilck <mwilck@...e.com>,
        Hannes Reinecke <hare@...e.de>
Subject: Re: [PATCH] scsi: core: Add BLIST_NO_ASK_VPD_SIZE for some VDASD

On 9/28/22 11:13, Lee Duncan wrote:
> From: Lee Duncan <lduncan@...e.com>
> 
> Some storage, such as AIX VDASD (virtual storage) and IBM 2076
> (front end) do not like the recent commit:
> 
> commit c92a6b5d6335 ("scsi: core: Query VPD size before getting full page")
> 
> That commit changed getting SCSI VPD pages so that we now read
> just enough of the page to get the actual page size, then read
> the whole page in a second read. The problem is that the above
> mentioned hardware returns zero for the page size, because of
> a firmware error. In such cases, until the firmware is fixed,
> this new black flag says to revert to the original method of
> reading the VPD pages, i.e. try to read as a whole buffer's
> worth on the first try.
> 
> Fixes: c92a6b5d6335 ("scsi: core: Query VPD size before getting full page")

Hi Lee,

If we introduce a blacklist flag to skip querying the VPD page size then 
we will have to find all SCSI devices that do not handle querying the 
VPD page size correctly. Has it been considered instead of introducing a 
blacklist flag to not use the reported VPD page size if the device 
reports that the VPD page size is zero? I am not aware of any VPD pages 
for which zero is a valid size.

Thanks,

Bart.