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From: Josef Bacik on 13 May 2010 14:00
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,

Josef
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From: Andrew Morton on 13 May 2010 14:20
On Thu, 13 May 2010 14:01:37 -0400
Josef Bacik <josef(a)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().
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From: Josef Bacik on 13 May 2010 14:40
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(a)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().

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

Josef
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