On Wed, May 04, 2016 at 02:16:11PM +0000, Vineet Gupta wrote:
> > static inline void *kmap_atomic(struct page *page)
> > {
> > preempt_disable();
> > pagefault_disable();
> > if (!PageHighMem(page))
> > return page_address(page);
> >
> > return __kmap_atomic(page);
> > }
>
> I actually want to return early for !PageHighMem and avoid the pointless 2
> LD-ADD-ST to memory for map and 2 LD-SUB-ST for unmap for regular pages for such
> cases.
So I'm fairly sure people rely on the fact you cannot have pagefault
inside a kmap_atomic().
But you could potentially get away with leaving preemption enabled. Give
it a try, see if something goes *bang* ;-)
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