Date: Mon, 23 Nov 2009 13:20:26 -0500 (EST)
From: Alan Stern <stern@rowland.harvard.edu>
To: Jan Kara <jack@suse.cz>
cc: tmhikaru@gmail.com, <linux-kernel@vger.kernel.org>,
       <linux-usb@vger.kernel.org>, Jens Axboe <axboe@kernel.dk>,
       <linux-scsi@vger.kernel.org>, <linux-ext4@vger.kernel.org>
Subject: Re: Weird I/O errors with USB hard drive not remounting filesystem
 readonly
In-Reply-To: <20091123160914.GG15679@duck.suse.cz>
Message-ID: <Pine.LNX.4.44L0.0911231319060.2958-100000@iolanthe.rowland.org>
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On Mon, 23 Nov 2009, Jan Kara wrote:

> On Mon 23-11-09 10:06:03, Alan Stern wrote:
> > On Mon, 23 Nov 2009, Jan Kara wrote:
> > 
> > >   Yeah, from what you write, it looks like USB enclosure is at fault (or it
> > > could still be your USB controller but I doubt it).  It's still a bit
> > > bothering that the error reported by the drive was not properly propagated
> > > up to VFS. Either it's some block layer retry/ignore magic that I missed or
> > > we ignore errors from block layer in some place.
> > 
> > Is there any interest in tracking this down?  It's not hard to find out
> > what low-level errors are being reported and to generate them on demand
> > with an emulated USB disk drive.
>   Well, if you could provide me with the patch, I could try to track down
> why the errors aren't propagated... It would be interesting because if it's
> not some retry logic in block layer, it's a bug in VFS ;).

I can't provide a patch without first knowing what the errors are.  The 
way to find out is to use usbmon.  See Documentation/usb/usbmon.txt for 
instructions.

Alan Stern

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