linux-kernel - Re: [BUG] FLOPPY DRIVER since 5.10.20

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Date:   Mon, 26 Jul 2021 08:23:48 -0400
From:   Mark Hounschell <markh@...pro.net>
To:     Denis Efremov <efremov@...ux.com>, dmarkh@....rr.com,
        linux-block@...r.kernel.org,
        Linux-kernel <linux-kernel@...r.kernel.org>
Cc:     Jiri Kosina <jkosina@...e.cz>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [BUG] FLOPPY DRIVER since 5.10.20

On 7/26/21 7:37 AM, Denis Efremov wrote:
> 
> 
> On 7/26/21 2:17 PM, Mark Hounschell wrote:
>> On 7/26/21 3:57 AM, Denis Efremov wrote:
>>> Hi,
>>>
>>> On 7/23/21 9:47 PM, Mark Hounschell wrote:
>>>>
>>>> These 2 incremental patches, patch-5.10.19-20 and patch-5.11.2-3 have broken the user land fd = open("/dev/fd0", (O_RDWR | O_NDELAY)); functionality.
>>>
>>> Thank you for the report, I'm looking into this.
>>>
>>>> Since FOREVER before the patch, when using O_NDELAY, one could open the floppy device with no media inserted or even with write protected media without error. "Read-only file system" status is returned only when we actually tried to write to it. We have software still in use today that relies on this functionality.
>>>
>>> If it's a project with open sources could you please give a link?
>>>
>>> Regards,
>>> Denis
>>>
>> This is immaterial but fdutils and libdsk both use rely on this flag. Who can know who else does. The point is it should NOT have been changed.
> 
> Yes, I asked this only to add utils and this behavior to the tests.
> And be more specific about why we should preserve this behavior in
> next commit messages.
> 

Well, first thing is now you can't open a floppy with a write protected 
floppy installed. I don't think that was intended but that is now how it is.

Next there are commands that can be sent to the floppy via "ioctl(fd, 
FDRAWCMD,  &raw_cmd);" that do NOT require a floppy diskette to be 
installed.

All commands issued to the device that require a floppy diskette without 
a diskette installed fail with the proper status letting you know the 
device is not ready / no diskette installed. That goes for write 
protected floppies too.

There is no reason to force a user to only be able to operate on Linux 
fdformat formatted floppies.

Regards
Mark