To:     Eric Wheeler <bcache@lists.ewheeler.net>
Cc:     "Martin K. Petersen" <martin.petersen@oracle.com>,
        Kent Overstreet <kent.overstreet@gmail.com>,
        Coly Li <colyli@suse.de>, linux-block@vger.kernel.org,
        Jonathan Corbet <corbet@lwn.net>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        "open list:BCACHE (BLOCK LAYER CACHE)" <linux-bcache@vger.kernel.org>
Subject: Re: [PATCH] bcache: make stripe_size configurable and persistent
 for hardware raid5/6
From:   "Martin K. Petersen" <martin.petersen@oracle.com>
Organization: Oracle Corporation
Message-ID: <yq1fspvq99j.fsf@ca-mkp.ca.oracle.com>
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Date:   Mon, 10 Jan 2022 21:55:21 -0500
In-Reply-To: <611f98fc-222-8dd2-6b81-d570fb91fc@ewheeler.net> (Eric Wheeler's
        message of "Mon, 10 Jan 2022 15:30:24 -0800 (PST)")
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Eric,

> Do you know if io_opt can be configured on scsi devices that do not
> have io_opt provided by the controller?  If so, or if it would be easy
> to add, then configuring io_opt at the scsi layer is probably a better
> option so subsystems besides bcache would benefit.

There is currently no way to do this in the SCSI sysfs interface.
However, io_opt is a queue_limits parameter. The appropriate location
for modification is blk-sysfs.c. We already allow overriding other block
device properties such as rotational, stable_writes, discards, max I/O
size, etc. I don't see any particular reason why we couldn't also permit
overriding the optimal I/O size.

-- 
Martin K. Petersen	Oracle Linux Engineering