linux-kernel - Re: Weird I/O errors with USB hard drive not remounting filesystem readonly

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Date:	Tue, 24 Nov 2009 12:16:17 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	tmhikaru@...il.com
cc:	Jan Kara <jack@...e.cz>, <linux-kernel@...r.kernel.org>,
	<linux-usb@...r.kernel.org>, Jens Axboe <axboe@...nel.dk>,
	<linux-scsi@...r.kernel.org>, <linux-ext4@...r.kernel.org>
Subject: Re: Weird I/O errors with USB hard drive not remounting filesystem
 readonly

On Mon, 23 Nov 2009 tmhikaru@...il.com wrote:

> Thank you. I've gotten output of it screwing up, but it's a 62MB file. I
> don't think I'm allowed to send attachments here, nor do I know what I'm
> supposed to be looking for in this output. So, instead I'm putting the
> (compressed) file up on my home computer. If you've got suggestions for what
> I should use instead, let me know.
> 
> http://hikaru.no-ip.info:3000/1.mon.out.xz
> 
> Although I don't think you'll need it, I've included the dmesg output of
> what happened when I ran my backup script, just in case it helps at all.

Here's an annotated example of one of those hiccups:

f1aa1f00 2416018820 S Bo:1:003:1 -115 31 = 55534243 07050100 00100000 80000a28 000000ae ef000008 00000000 000000
f1aa1f00 2416018929 C Bo:1:003:1 0 31 >

The computer issued a READ command for 8 blocks (4096 bytes) starting
at block number 0x0000aeef = 44783.

d2588b00 2416019342 S Bi:1:003:2 -115 4096 <
d2588b00 2416019428 C Bi:1:003:2 -32 0
f1aa1f00 2416019435 S Co:1:003:0 s 02 01 0000 0082 0000 0
f1aa1f00 2416019554 C Co:1:003:0 0 0

The drive returned 0 bytes of data.

f1aa1f00 2416019560 S Bi:1:003:2 -115 13 <
f1aa1f00 2416019678 C Bi:1:003:2 0 13 = 55534253 07050100 00100000 00

And then it returned a status indicating no error but 4096 bytes
residue (i.e., incorrect or undelivered data).  This caused the
usb-storage driver to send the SCSI layer a result code of DID_ERROR
with no sense data.

> sd 0:0:0:0: [sda] Unhandled error code
> sd 0:0:0:0: [sda] Result: hostbyte=0x07 driverbyte=0x00
> end_request: I/O error, dev sda, sector 44783

The DID_ERROR code caused the SCSI layer to display this error message.  

> sd 0:0:0:0: [sda] Unhandled error code
> sd 0:0:0:0: [sda] Result: hostbyte=0x07 driverbyte=0x00
> end_request: I/O error, dev sda, sector 51823

I would have expected the READ to be retried, but in these two cases 
it wasn't.  The usbmon log contained five instances of this error 
sequence; the other three were retried successfully.  I don't know what 
the difference was.

Alan Stern

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