Message-ID: <1544454711.18488.1.camel@redhat.com>
Subject: Re: [PATCH] block: Restore tape support
From: Laurence Oberman <loberman@redhat.com>
To: Christoph Hellwig <hch@lst.de>,
        Bart Van Assche <bvanassche@acm.org>
Cc: Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
        Todd Aiken <taiken@mvtech.ca>,
        Keith Busch <keith.busch@intel.com>, stable@vger.kernel.org
Date: Mon, 10 Dec 2018 10:11:51 -0500
In-Reply-To: <20181210111729.GA21553@lst.de>
References: <20181210030814.13235-1-bvanassche@acm.org>
         <20181210111729.GA21553@lst.de>
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Sender: stable-owner@vger.kernel.org

On Mon, 2018-12-10 at 12:17 +0100, Christoph Hellwig wrote:
> On Sun, Dec 09, 2018 at 07:08:14PM -0800, Bart Van Assche wrote:
> > According to what I found in
> > https://bugzilla.kernel.org/show_bug.cgi?id=201935 patch "block:
> > Clear
> > kernel memory before copying to user" broke tape access. Hence
> > revert
> > that patch.
> 
> This looks wrong.  The patch from Keith is obviously correct for
> normal usage of bio_copy_user_iov.  The SCSI tape drivers use the
> somewhat odd null_mapped case, so we probably need to refine the
> checks
> for that a bit.

I am going to look into that, just connected a tape device so I can
reproduce and then see what we need to make it more specific in the st
driver.
I may need help from folks who understand the bio stuff better than I
do.

Back when I have more.

Regards
Laurence