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

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Date:	Tue, 24 Nov 2009 19:00:37 +0100
From:	Jan Kara <jack@...e.cz>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	tmhikaru@...il.com, 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 Tue 24-11-09 12:16:17, Alan Stern wrote:
> 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.
  My naive guess would be that those non-retried reads were actually
readahead. That's not retried if I remember correctly. Later, when we
really needed the data, we sent another read request...

								Honza
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