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SubjectRe: [PATCH 4/4] Btrfs: add basic DIO read/write support V3
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 so looking at debug_kmap_atomic it seems that KM_IRQ0 is ok to use in all
cases, in_irq(), !irqs_disabled() and !in_interrupt(), so I should be safe. If
you still don't like it, would something like this be acceptable?

if (in_interrupt() || irqs_disabled()) {
if (in_irq())
type = KM_IRQ0;
else if (!irqs_disabled())
type = KM_SOFTIRQ0;
else
type = KM_IRQ0;
} else {
type = KM_USER0;
}
Hrm, you'd think somebody would have had this problem before and already come up
with a nice helper, oh well. Thanks,

Josef


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