Re: 2.6.23-rc1: BUG_ON in kmap_atomic_prot()

On 7/24/07, Jens Axboe [off-list ref] wrote:

What about the new async crypto stuff? I've been looking, but is it
guarenteed that async_memcpy() runs in process context with interrupts
enabled always? If not, there's a km type bug there.

Currently the only user is the MD raid456 driver, and yes, it only
performs copies from the handle_stripe routine which is always run in
process context with interrupts enabled.  However this is not
documented.  Would it be advisable to add a WARN_ON for this
condition?

In general, I think the highmem stuff could do with more safety checks:

- People ALWAYS get the atomic unmaps wrong, passing in the page instead
  of the address. I've seen tons of these. And since kunmap_atomic()
  takes a void pointer, nobody notices until it goes boom.
- People easily get the km type wrong - they use KM_USERx in interrupt
  context, or one of the irq variants without disabling interrupts.

If we could just catch these two types of bugs, we've got a lot of these
problems covered.


--
Jens Axboe

--
Dan