linux-kernel - RE: [PATCH v4] drivers/block/mtip32xx: Adding new driver mtip32xx

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Date:	Fri, 9 Sep 2011 08:10:42 -0700
From:	"Sam Bradshaw (sbradshaw)" <sbradshaw@...ron.com>
To:	"Jens Axboe" <jaxboe@...ionio.com>,
	"Christoph Hellwig" <hch@...radead.org>
Cc:	<alan@...rguk.ukuu.org.uk>, <linux-ide@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, "Jeff Garzik" <jgarzik@...ox.com>,
	<jmoyer@...hat.com>,
	"Asai Thambi Samymuthu Pattrayasamy (asamymuthupa) [CONTRACTOR]" 
	<asamymuthupa@...ron.com>
Subject: RE: [PATCH v4] drivers/block/mtip32xx: Adding new driver mtip32xx


> On 2011-09-09 10:54, Christoph Hellwig wrote:
> > On Mon, Aug 22, 2011 at 02:28:11PM -0700, Sam Bradshaw (sbradshaw)
wrote:
> >> New patch for mtip32xx driver based on feedback from
> >> Jens Axboe, Christoph Hellwig, and Alan Cox.
> >
> > A few comments that need addressing:
> >
> >  - the ioctl handler always returns 0 for the BLKFLSBUF ioctl,
without
> >    doing anything.  Given that the ioctl is supposed to flush all
kinds
> >    of higher level cached data this is a serious data integrity
issue.
> >    It must simply do the default -ENOTTY return for it and let the
block
> >    layer do the right thing.
> >  - handling of REQ_FUA / REQ_FLUSH requests is completely broken.
> >    There is a weird barrier flag to mtip_hw_submit_io which set the
> >    hwardware FUA bit if the FLUSH bit is set on a request.
> >    Please take a look at how this should be handled, the
> >    Documentation/block/writeback_cache_control.txt file is the
canonical
> >    resource.  Implementing your driver at the make_request layer
> >    unfortunately means you will have to do all the hard work
yourself.
> >  - also the call to blk_queue_flush(queue, 0); from ->make_request
for
> >    a non-data request is completely wrong.
> 
> I noticed both of these flush/fua problems too and have fixed them up.
> 
> >  - the 64-bit case in fill_command_sg will blow up on big endian
> >    systems, please use your current 32-bit case unconditionally
> >  - mtip_block_getgeo should just use sector_div instead of the ifdef
> >    mess.
> >  - please check the driver using sparse, and most importantly the
> >    optional endianess checking pass of it.  Currently the driver
> >    uses plain unsigned int and similar types for little endian
> >    hardware structures.  Take a look at Documentation/sparse.txt
> >    on how to use it.
> >  - the mtip_check_surprise_removal check should be unconditional,
not
> >    under #ifdef CONFIG_HOTPLUG
> 
> In general, the dependency on HOTPLUG_PCI_PCIE is odd as well.
> 
> >  - Given that the driver has a single c implementation file all
symbols
> >    should be marked static, and there should be no prototypes in the
> >    header
> 
> Sam, would be nice if you could send in patches for the other bugs
that
> Christoph have pointed out. I already found and fixed the flush parts.

Will do.  I'll send out patches against for-3.2/mtip32xx, given that
Jens has already made some changes.

Thanks for the tip on sparse endianness checking.  I wasn't aware of
this tool until now.

-Sam


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