Re: [PATCH] copy_from_high_bh

[Mark Hemment]

On Sun, 8 Jul 2001, Linus Torvalds wrote:
> On Sun, 8 Jul 2001 [e-mail] wrote:
> >
> >   mm/highmem.c/copy_from_high_bh() blocks interrupts while copying "down"
> > to a bounce buffer, for writing.
> >   This function is only ever called from create_bounce() (which cannot
> > be called from an interrupt context - it may block), and the kmap
> > 'KM_BOUNCE_WRITE' is only used in copy_from_high_bh().
>
> If so it's not just the interrupt disable that is unnecessary, the
> "kmap_atomic()" should also be just a plain "kmap()", I think.

  That might eat through kmap()'s virtual window too quickly.

  I did think about adding a test to see if the page was already mapped,
and falling back to kmap_atomic() if it isn't.  That should give the best
of both worlds?

Mark