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Date:	Wed, 30 Nov 2011 20:25:03 -0600
From:	Robert Hancock <hancockrwd@...il.com>
To:	sedat.dilek@...il.com
Cc:	Jens Axboe <axboe@...nel.dk>, Tejun Heo <tj@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-next <linux-next@...r.kernel.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: ERROR: end_request: I/O error, dev fd0, sector 0

On Sun, Nov 27, 2011 at 7:52 AM, Sedat Dilek <sedat.dilek@...glemail.com> wrote:
> On Sat, Nov 26, 2011 at 5:52 PM, Robert Hancock <hancockrwd@...il.com> wrote:
>> On 11/25/2011 06:53 AM, Sedat Dilek wrote:
>>>
>>> Hi,
>>>
>>> I am watching this issue for a long while, due to my
>>> floppy-blacklist.conf file since next-20110603.
>>>
>>> The bad: The boot-process stalls for approx 10-13 secs when booting
>>> into my Debian/sid i386 system.
>>>
>>> # dmesg | grep -A1 -B1 "end_request: I/O error, dev fd0, sector 0"
>>> [    2.422854] sd 2:0:0:0: [sdb] Attached SCSI disk
>>> [   15.289939] end_request: I/O error, dev fd0, sector 0
>>> [   15.342914] EXT4-fs (sda5): mounted filesystem with ordered data
>>> mode. Opts: (null)
>>>
>>> The funny part is my IBM laptop has no physical floppy drive!
>>>
>>> # dmesg | egrep -i 'floppy|fd0'
>>> [    0.726358] Floppy drive(s): fd0 is 1.44M
>>> [   15.289939] end_request: I/O error, dev fd0, sector 0
>>>
>>> If I blacklist "floppy" kernel-module, the boot-process is as expected
>>> without the above mentionned delay.
>>>
>>> [ /etc/modprobe.d/floppy-blacklist.conf ]
>>> # This file blacklists the floppy driver.
>>> #
>>> # XXX: Workaround: My IBM ThinkPad T40p (model 2374SG6) notebook has
>>> no physical FDD
>>> # dmesg from linux-next (next-20110603) says:
>>> # [    0.755294] Floppy drive(s): fd0 is 1.44M
>>> # [   15.238507] end_request: I/O error, dev fd0, sector 0
>>> blacklist floppy
>>> - EOF -
>>>
>>> I searched for the line and found bool blk_update_request() in
>>> block/blk-core.c file (see [1]).
>>>
>>> I have attached kern.log and dmesg.
>>>
>>> Hope this helps to narrow down the issue.
>>
>> It looks like your laptop's BIOS indicates it has a floppy controller that's
>> active:
>>
>> Nov 25 11:00:32 tbox kernel: [    0.060821] pnp 00:09: [io  0x03f0-0x03f5]
>> Nov 25 11:00:32 tbox kernel: [    0.060825] pnp 00:09: [io  0x03f7]
>> Nov 25 11:00:32 tbox kernel: [    0.060828] pnp 00:09: [irq 6]
>> Nov 25 11:00:32 tbox kernel: [    0.060831] pnp 00:09: [dma 2]
>> Nov 25 11:00:32 tbox kernel: [    0.060892] pnp 00:09: Plug and Play ACPI
>> device, IDs PNP0700 (active)
>>
>> That's presumably why the floppy driver ends up being loaded. And apparently
>> it does have a floppy controller, since the floppy driver seems able to talk
>> to it. Maybe that model of laptop had an optional bay-mounted floppy drive
>> or something?
>>
>
> Could be... next to CD_ROM bay maybe.
>
>> I'm not sure there's a workaround for this at the kernel level, since the
>> kernel probably can't determine if there's actually a floppy drive installed
>> without trying to read from it (which is likely being triggered by partition
>> probing or something). The read error will be what is triggering the message
>> you saw.
>>
>> Is there a BIOS option to disable the floppy controller?
>>
>
> I have disabled "Floppy-Drive" in BIOS setup now (was set to
> "enabled"), but I have still the modprobe backlist for floppy
> activated.
>
> Can you explain the stalling of ***10-12 seconds*** with a wrong FDD
> BIOS setting?
> That's really a long duration, with systemd my boot-process takes
> approx 15-18 seconds.

Well, I can imagine that the floppy request takes that long to time
out or fail. I'm not sure why this would be delaying the boot process,
however.

>
> Attached is the new dmesg output (kernel-config was not changed).

It looks like the BIOS is no longer reporting the floppy controller as
present, so hopefully you shouldn't need the workaround.
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