linux-kernel - Re: Resend: Another 4.4 to 4.5 floppy issue

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Date:	Mon, 11 Jul 2016 17:36:36 +0200 (CEST)
From:	Jiri Kosina <jikos@...nel.org>
To:	Mark Hounschell <markh@...pro.net>
cc:	Linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Resend: Another 4.4 to 4.5 floppy issue

On Tue, 5 Jul 2016, Mark Hounschell wrote:

> From: Jiri Kosina <jkosina@...e.cz>
> 
> Commit 09954bad4 ("floppy: refactor open() flags handling"), as a
> side-effect, causes open(/dev/fdX, O_ACCMODE) to fail. It turns out that
> this is being used setfdprm userspace for ioctl-only open().
> 
> Reintroduce back the original behavior wrt !(FMODE_READ|FMODE_WRITE)
> modes, while still keeping the original O_NDELAY bug fixed.
> 
> Cc: stable@...r.kernel.org # v4.5+
> Reported-by: Wim Osterholt <wim@....tudelft.nl>
> Tested-by: Wim Osterholt <wim@....tudelft.nl>
> Signed-off-by: Jiri Kosina <jkosina@...e.cz>
> ---
[ ... snip ... ]
> 
> But this does not completely fix all the problems induced by the original
> changes from 4.4 to 4.5. The following is what we use to open the floppy.
> 
> fd = open(device,  O_RDWR | O_NDELAY);
> 
> The FMODE_NDELAY check that was removed now prevents one from doing an open of
> the device with no media inserted. It also prevents one from doing an open of
> the device with media inserted that is not already formatted in a "standard"
> format.  I do both of these things a lot. I deal with a few very non-standard
> formats and this change prevents me from doing what I've been doing for YEARS.
> Could we please get the original behavior back in the floppy driver.

Hi Mark,

thanks for the regression report.

For my better understanding of your issue -- what behavior/semantics 
exactly does your userspace think it'll be getting from opening /dev/fd0 
with O_NDELAY?

Thanks,

-- 
Jiri Kosina
SUSE Labs