linux-kernel - Re: [PATCH] floppy: reintroduce O

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Date:   Tue, 26 Jan 2021 12:59:08 +0300
From:   Denis Efremov <efremov@...ux.com>
To:     Kurt Garloff <kurt@...loff.de>, Jiri Kosina <jikos@...nel.org>,
        Jens Axboe <axboe@...nel.dk>
Cc:     linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        Wim Osterholt <wim@....tudelft.nl>
Subject: Re: [PATCH] floppy: reintroduce O_NDELAY fix



On 1/26/21 12:31 PM, Kurt Garloff wrote:
> Hi Denis, Jiri, Jens,
> 
> Am 26.01.21 um 09:21 schrieb Denis Efremov:
>> On 1/22/21 2:13 PM, Jiri Kosina wrote:
>>> From: Jiri Kosina <jkosina@...e.cz>
>>>
>>> This issue was originally fixed in 09954bad4 ("floppy: refactor open() 
>>> flags handling").
>>>
>>> The fix as a side-effect, however, introduce issue for open(O_ACCMODE) 
>>> that is being used for ioctl-only open. I wrote a fix for that, but 
>>> instead of it being merged, full revert of 09954bad4 was performed, 
>>> re-introducing the O_NDELAY / O_NONBLOCK issue, and it strikes again.
>>>
>>> This is a forward-port of the original fix to current codebase; the 
>>> original submission had the changelog below:
>>>
>>> ====
>>> 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
>>> Reported-by: Wim Osterholt <wim@....tudelft.nl>
>>> Tested-by: Wim Osterholt <wim@....tudelft.nl>
>>> Reported-and-tested-by: Kurt Garloff <kurt@...loff.de>
>>> Fixes: 09954bad4 ("floppy: refactor open() flags handling")
>>> Fixes: f2791e7ead ("Revert "floppy: refactor open() flags handling"")
>>> Signed-off-by: Jiri Kosina <jkosina@...e.cz>
>> Applied. I'll send it to Jens soon with a couple of cleanup patches.
>>
>> https://github.com/evdenis/linux-floppy/commit/e32f6163c47efbdbad06258560aa00d1c7e5b699
> 
> Great, thanks.
> 
> Due to libblkid (rightfully) using O_NONBLOCK these days when probing
> devices, the floppy driver does spit loads of
> [    9.533513] floppy0: disk absent or changed during operation
> [    9.534989] blk_update_request: I/O error, dev fd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
> [    9.537206] Buffer I/O error on dev fd0, logical block 0, async page read
> [    9.546837] floppy0: disk absent or changed during operation
> [    9.548389] blk_update_request: I/O error, dev fd0, sector 0 op 0x0:(READ) flags 0x80700 phys_seg 1
> and fails a mount prior to being opened without O_NONBLOCK at least once.
> (Reproduction is easy with qemu-kvm.)
> 
> The patch addresses it and I would suggest it to also be backported and
> applied to the active stable kernel trees.

Yes, it will be backported to all stable trees including v4.4

Thanks,
Denis