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To:     Denis Efremov <efremov@linux.com>, Jiri Kosina <jikos@kernel.org>,
        Jens Axboe <axboe@kernel.dk>
Cc:     linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
        Wim Osterholt <wim@djo.tudelft.nl>
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From:   Kurt Garloff <kurt@garloff.de>
Subject: Re: [PATCH] floppy: reintroduce O_NDELAY fix
Message-ID: <f822ebde-89d6-dbbf-ae4e-b06a4aadedf5@garloff.de>
Date:   Tue, 26 Jan 2021 10:31:07 +0100
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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@suse.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@vger.kernel.org
>> Reported-by: Wim Osterholt <wim@djo.tudelft.nl>
>> Tested-by: Wim Osterholt <wim@djo.tudelft.nl>
>> Reported-and-tested-by: Kurt Garloff <kurt@garloff.de>
>> Fixes: 09954bad4 ("floppy: refactor open() flags handling")
>> Fixes: f2791e7ead ("Revert "floppy: refactor open() flags handling"")
>> Signed-off-by: Jiri Kosina <jkosina@suse.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.

Thanks,

-- 
Kurt Garloff <kurt@garloff.de>, Cologne, Germany