From: Jens Axboe <axboe@kernel.dk>
To: "Pali Rohár" <pali@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Christoph Hellwig <hch@infradead.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Linux 6.2-rc1
Date: Thu, 5 Jan 2023 10:45:47 -0700 [thread overview]
Message-ID: <58d3649f-3c8c-8b12-1930-f06f59837ad5@kernel.dk> (raw)
In-Reply-To: <20230105174210.jbjoqelllcrd57q6@pali>
On 1/5/23 10:42?AM, Pali Roh?r wrote:
> On Wednesday 04 January 2023 14:43:16 Jens Axboe wrote:
>> On 1/4/23 2:32?PM, Linus Torvalds wrote:
>>>> But here it is CD-RW media in read-write mode with kernel udf
>>>> filesystem driver without any userspace involved (after proper
>>>> formatting).
>>>
>>> ... but I'm not sure about direct writeable mount support.
>>>
>>> That may indeed be an area that only pktcdvd ended up doing. I've
>>> never used it myself, even historically.
>>>
>>> Let's bring in more people. Because they may not have thought about
>>> some RW UDF case.
>>
>> We did think about it, since that's the only reason for pktcdvd to
>> exist. Basically what the driver does is ensure that any write is 32K in
>> size, which is the size which can be written to media. It'll gather data
>> as needed to make that happen. Thats it. Outside of that, it's just some
>> setup and closing code.
>>
>> This obviously would be better to handle in userspace, all of it. Back
>> when I wrote this driver, we didn't have a lot of the fancier stuff we
>> have today. It could be done via ublk, for example, or something like
>> that.
>>
>> The surprising bit here is:
>>
>> 1) Someone is still using this driver, and
>> 2) It actually works!
>
> Yes, there are still users and userspace tools (cdrwtool / pktsetup) are
> still receiving either small patches or issue reports. I think that it
> was two years ago when cdrwtool received big fixups to support
> formatting CD-RW discs on new CD/DVD drives.
>
>> While I'd love to nudge folks in other directions for this use case, and
>> I strongly think that we should, it also doesn't seem fair to just yank
>> it while folks are using it... But I'd like to VERY strongly encourage
>> folks to come up with a new solution for this use case. It really isn't
>> a solution that belongs in the kernel today.
>
> Linus in previous email wrote that he did "make SCSI commands generic"
> work in past so direct usage of /dev/cdrom device works for CD-R burning
> and read-only mounting.
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 :-)
> So could not be (for example sr.c) driver extended to directly do
> pktcdvd's work? So when somebody opens /dev/cdrom device in O_RDWR mode
> and CD-RW medium is present then it would behave like pktcdvd device...
> To have /dev/cdrom generic also for CD-RW write access.
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.
--
Jens Axboe
next prev parent reply other threads:[~2023-01-05 17:46 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-25 22:07 Linux 6.2-rc1 Linus Torvalds
2022-12-26 19:52 ` Guenter Roeck
2022-12-26 20:56 ` Linus Torvalds
2022-12-26 21:03 ` Kees Cook
2022-12-26 22:10 ` Guenter Roeck
2022-12-27 0:29 ` Guenter Roeck
2022-12-27 1:32 ` Kees Cook
2022-12-27 5:52 ` Guenter Roeck
2022-12-28 3:40 ` Kees Cook
2022-12-28 14:44 ` Guenter Roeck
2023-01-07 0:06 ` Jaegeuk Kim
2022-12-26 22:41 ` Vlastimil Babka
2022-12-26 21:10 ` Max Filippov
2022-12-26 22:08 ` Guenter Roeck
2022-12-27 8:29 ` Build regressions/improvements in v6.2-rc1 Geert Uytterhoeven
2022-12-27 8:35 ` Geert Uytterhoeven
2023-01-01 1:33 ` Rob Landley
2023-01-01 12:24 ` Geert Uytterhoeven
2023-01-04 6:32 ` Michael Ellerman
2023-01-06 15:10 ` John Paul Adrian Glaubitz
2023-01-06 15:17 ` Geert Uytterhoeven
2023-01-06 15:18 ` Geert Uytterhoeven
2023-01-17 16:42 ` Calculating array sizes in C - was: " John Paul Adrian Glaubitz
2023-01-17 17:01 ` Geert Uytterhoeven
2023-01-17 17:06 ` John Paul Adrian Glaubitz
2023-01-17 20:05 ` Geert Uytterhoeven
2023-01-17 20:37 ` John Paul Adrian Glaubitz
2023-01-19 22:11 ` Michael.Karcher
2023-01-20 3:31 ` Rob Landley
2023-01-20 10:53 ` Segher Boessenkool
2023-01-20 18:29 ` Michael.Karcher
2023-01-20 8:49 ` John Paul Adrian Glaubitz
2023-01-20 19:29 ` Michael Karcher
2023-01-21 21:26 ` John Paul Adrian Glaubitz
2023-01-06 15:39 ` Alex Deucher
2023-01-04 19:01 ` Linux 6.2-rc1 Pali Rohár
2023-01-04 19:25 ` Linus Torvalds
2023-01-04 20:56 ` Pali Rohár
2023-01-04 21:27 ` Pali Rohár
2023-01-04 21:32 ` Linus Torvalds
2023-01-04 21:43 ` Jens Axboe
2023-01-05 11:25 ` Greg Kroah-Hartman
2023-01-05 15:26 ` Jens Axboe
2023-01-05 17:42 ` Pali Rohár
2023-01-05 17:45 ` Jens Axboe [this message]
2023-01-05 19:06 ` Linus Torvalds
2023-01-05 19:22 ` Pali Rohár
2023-01-05 19:40 ` Jens Axboe
2023-01-05 20:03 ` Linus Torvalds
2023-01-05 20:33 ` Jens Axboe
2023-01-06 16:58 ` Pali Rohár
2023-01-06 17:04 ` Jens Axboe
2023-01-28 19:34 ` pktcdvd Pali Rohár
2023-01-28 19:43 ` pktcdvd Linus Torvalds
2023-01-29 21:53 ` pktcdvd Jens Axboe
2023-01-29 21:55 ` pktcdvd Jens Axboe
2023-01-29 22:21 ` pktcdvd Pali Rohár
2023-01-29 22:34 ` pktcdvd Jens Axboe
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