linux-kernel - Re: Doubts on IO requests in USB subsystem

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Message-ID: <1379329599.15916.25.camel@linux-fkkt.site>
Date:	Mon, 16 Sep 2013 13:06:39 +0200
From:	Oliver Neukum <oliver@...kum.org>
To:	"Morales, Alejandra" <alejandra.morales@....de>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Doubts on IO requests in USB subsystem

On Mon, 2013-09-16 at 10:33 +0000, Morales, Alejandra wrote:
> 2013/9/9 Oliver Neukum <oliver@...kum.org>
> >
> > Your prime suspect is the detection of medium change which was
> > moved into the kernel in 3.2 or so. It can be disabled by sysfs.
> > Generally the notion that a certain task originates a read or write
> > on a block device is iffy. Read-ahead and shared data structures
> > make it impossible to accurately tell.
> >
> > USB storage devices are notorious for setting the removable bit
> > even if they have no removable medium.
> >
> 
> Thanks for the answer Oliver. Unfortunately it doesn't seem to be the
> medium change detection what is causing these requests, since the
> removable bit is disabled and the polling period is set to -1:

Interesting. Then you have no choice. Make a usbmon trace and look
at the SCSI commands going to the device.

	HTH
		Oliver


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