linux-kernel - Re: [PATCH 4/4] Btrfs: add basic DIO read/write support V3

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Message-ID: <20100513183935.GI27011@dhcp231-156.rdu.redhat.com>
Date:	Thu, 13 May 2010 14:39:35 -0400
From:	Josef Bacik <josef@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Josef Bacik <josef@...hat.com>,
	Christoph Hellwig <hch@...radead.org>,
	linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 4/4] Btrfs: add basic DIO read/write support V3

On Thu, May 13, 2010 at 11:11:36AM -0700, Andrew Morton wrote:
> On Thu, 13 May 2010 14:01:37 -0400
> Josef Bacik <josef@...hat.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().

Great, thank you, I will fix this up and resend.

Josef
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