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Date: Thu, 13 May 2010 11:11:36 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Josef Bacik <josef@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>, linux-btrfs@vger.kernel.org,
       linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 4/4] Btrfs: add basic DIO read/write support V3
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On Thu, 13 May 2010 14:01:37 -0400
Josef Bacik <josef@redhat.com> wrote:

> On Thu, May 13, 2010 at 11:26:39AM -0400, Christoph Hellwig wrote:
> > On Thu, May 13, 2010 at 11:31:45AM -0400, Josef Bacik wrote:
> > > AIO's aio_complete does kmap with KM_IRQ0/1 and it gets called in the same
> > > context as the btrfs completion handler, so if it's ok for aio_complete it
> > > should be ok for btrfs right?  Thanks,
> > 
> > aio_complete does a spin_lock_irqsave before that, which disables
> > interrupts on the local CPU.
> > 
> 
> Ok how about I just do
> 
> local_irq_disable()
> kmap(KM_IRQ0)
> local_irq_enable()
> 
> would that be acceptable?  Thanks,

yup.

local_irq_disable() (or local_irq_save())
kmap_atomic(KM_IRQx);
<stuff>
kunmap_atomic(KM_IRQx);
local_irq_enable() (or local_irq_restore()).

then perhaps flush_dcache_page().