Re: 2.6.24-git: kmap_atomic() WARN_ON()

Nick Piggin
2008-02-26T23:51:26Z

On Wednesday 27 February 2008 07:49, Ingo Molnar wrote:
> * Andrew Morton <akpm@linux-foundation.org> wrote:
> > > This is only being done to satisfy kmap_atomic's requirements, not
> > > libata's.
> > >
> > > I could add a "kmap lock" but that just seems silly.
> >
> > It's a bit sad to disable interupts across a memset (how big is it?)
> > just for the small proportion of cases which are accessing a highmem
> > page.
> >
> > What you could do is to add an `unsigned long *flags' arg to
> > ata_scsi_rbuf_get() and ata_scsi_rbuf_put(), and then, in
> > ata_scsi_rbuf_get() do
> >
> > if (PageHighmem(page))
> > local_irq_disable(*flags);
>
> it would be much nicer to attach the irq disabling to the object, not to
> some arbitrary place in the code.
>
> i.e. to introduce a kmap_atomic_irqsave(...,flags) and
> kunmap_atomic_irqrestore() API variant. _That_ then could be mapped by
> -rt to a non-irq disabling thing.

Yeah that is the right way to fix it, but that name implies that
interrupts are disabled for non-highmem pages too, which we don't
want. Can you think of a better one?

kmap_atomic_irq_safe maybe?