On Sat, Apr 17, 2021 at 09:22:40PM +0100, Matthew Wilcox wrote:
> On Sat, Apr 17, 2021 at 09:32:06PM +0300, Ilias Apalodimas wrote:
> > > +static inline void page_pool_set_dma_addr(struct page *page, dma_addr_t addr)
> > > +{
> > > + page->dma_addr[0] = addr;
> > > + if (sizeof(dma_addr_t) > sizeof(unsigned long))
> > > + page->dma_addr[1] = addr >> 16 >> 16;
> >
> > The 'error' that was reported will never trigger right?
> > I assume this was compiled with dma_addr_t as 32bits (so it triggered the
> > compilation error), but the if check will never allow this codepath to run.
> > If so can we add a comment explaining this, since none of us will remember why
> > in 6 months from now?
>
> That's right. I compiled it all three ways -- 32-bit, 64-bit dma, 32-bit long
> and 64-bit. The 32/64 bit case turn into:
>
> if (0)
> page->dma_addr[1] = addr >> 16 >> 16;
>
> which gets elided. So the only case that has to work is 64-bit dma and
> 32-bit long.
>
> I can replace this with upper_32_bits().
>
Ok up to you, I don't mind either way and thanks for solving this!
Acked-by: Ilias Apalodimas <ilias.apalodimas@xxxxxxxxxx>
