linux-kernel - Re: [PATCH v3 3/3] scsi: Set allocation length to 255 for ATA Information VPD page

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Date:   Mon, 03 Jan 2022 16:37:46 -0500
From:   "Martin K. Petersen" <martin.petersen@...cle.com>
To:     Douglas Gilbert <dgilbert@...erlog.com>
Cc:     "Maciej W. Rozycki" <macro@...am.me.uk>,
        Khalid Aziz <khalid@...ehiking.org>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Christoph Hellwig <hch@....de>, Nix <nix@...eri.org.uk>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/3] scsi: Set allocation length to 255 for ATA
 Information VPD page

Doug,

> sd_read_write_same() seems a strange name for a function given that
> it is checking on WRITE SAME support. How about s/read/report/ ?

It was chosen to be consistent with all the other sd_read_$VPD()
functions. sd_read_cache_type(), sd_read_block_limits(), etc.

> And calling scsi_report_opcode() on INQUIRY seems a weird time waster
> (it actually checks if the SCSI version is < SPC-3 or does the check
> on a _mandatory_ command).

The call to validate INQUIRY is really to check whether REPORT SUPPORTED
OPERATION CODES command is supported.

> And for modern disks scsi_report_opcode() is called 5 times. Why not
> call the REPORT SUPPORTED OPERATION CODES command once and cache its
> result? It would save 4 commands in every disk setup (or
> revalidation).

I have some patches that clean up discovery and start using cached
VPDs. I hadn't thought of caching the RSOC output. Will look into that.

I held this series back since I was concerned about them clashing with
Christoph's recent revalidate changes. I'll get them sent out shortly.

-- 
Martin K. Petersen	Oracle Linux Engineering