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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Thu, 5 Jan 2023 11:06:21 -0800
Message-ID: <CAHk-=wiKUWm3VoYHK-oKixc9nF5Qdwp598MPSoh=jdxKAU1bOw@mail.gmail.com>
Subject: Re: Linux 6.2-rc1
To:     Jens Axboe <axboe@kernel.dk>
Cc:     =?UTF-8?Q?Pali_Roh=C3=A1r?= <pali@kernel.org>,
        Christoph Hellwig <hch@infradead.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Thu, Jan 5, 2023 at 9:45 AM Jens Axboe <axboe@kernel.dk> wrote:
>
> Not quite sure what that refers to, as I'm pretty sure I did all of that
> work. But maybe Linus can refresh my memory here :-)

I was definitely there, part of making it actually work for *every*
block device.

Long long ago, it used to be limited to the sg_io() interface, and
only worked for SCSI devices.

So you couldn't actually burn CD's with the regular IDE/ATA CD ROM
drivers directly, but had to use a shim driver, kind of like pktcdvd.
Except I think it was just /dev/cdrom.

See

  https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/?id=90df68e70b

for some of it (exposing SG_IO to all the block ioctls), and the "make
it more usable" parts that made it do sane permission checking in

  https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/?id=a75aaa84276

and the commits preceding it for that part of the work.

But yes, you were very much involved too.

> As mentioned, I don't think this kind of code belongs in the kernel. sr
> or cdrom could easily be modified to support the necessary bits to
> handle a writeable open, but the grunt of the pktcdvd code deals with
> retrieving and writing out bigger chunks of data. And that part really
> does belong in userspace imho.

Well, it's the UDF write support that is the issue.. I didn't even
realize people did that.

You'd presumably have to re-do it as a FUSE thing.

                 Linus