Re: NFS kernel oops with Thecus DMA patch

[Lennert Buytenhek <buytenh@wantstofly.org>]

On Tue, Sep 22, 2009 at 11:28:52PM -0700, Steve Langasek wrote:

> After building myself a 2.6.30 kernel with the iop dma patches for
> my Thecus, I started seeing reproducible kernel oopses on large NFS
> transfers, such as the one included below.  After some prodding at
> the source for other uses of down_read(), I concluded that we're not
> supposed to call down_read(&current->mm->mmap_sem) if in_atomic() is
> true.  Updating the dma1
> patch from http://people.debian.org/~tbm/dma/dma-patch to the
> attached appears to have fixed the problem for me, giving me a
> stable DMA-enabled squeeze kernel.

Looks good, I guess.  This is basically the same technique as
arch/arm/lib/uaccess_with_memcpy.c uses.