linux-kernel - Re: ERROR: end_request: I/O error, dev fd0, sector 0

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Date:	Sat, 26 Nov 2011 10:52:03 -0600
From:	Robert Hancock <hancockrwd@...il.com>
To:	sedat.dilek@...il.com
CC:	Sedat Dilek <sedat.dilek@...glemail.com>,
	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 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?

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?
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