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Date: Tue, 6 Nov 2001 02:22:30 -0500 (EST)
From: Alexander Viro <viro@math.psu.edu>
To: Richard Gooch <rgooch@ras.ucalgary.ca>
cc: alain@linux.lu, Linus Torvalds <torvalds@transmeta.com>,
        linux-kernel@vger.kernel.org
Subject: Re: Poor floppy performance in kernel 2.4.10 
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On Tue, 6 Nov 2001, Richard Gooch wrote:

> IIRC that I've told you this already. Here it is again: devfs=only
> serves as a way of enforcing that the devfs entry->driver ops
> connection is the only way of accessing a driver. It deliberately
> breaks the fallback to major-table-lookup.
> 
> And it actually works now. It doesn't require massive 2.5 changes.
> When I boot with devfs=only (which is always), my system still works.

Try rmmod while blkdev_get() (from mount(2) or swapon(2)) sleeps on ->bd_sem.
And think what happens with value of ->bd_op.

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