On Thu, 26 Mar 2015, Ritesh Harjani wrote:
> > diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> > index 83cd5ac..3f1ac51 100644
> > --- a/arch/arm/mm/dma-mapping.c
> > +++ b/arch/arm/mm/dma-mapping.c
> > @@ -1150,13 +1150,28 @@ static struct page **__iommu_alloc_buffer(struct
> > device *dev, size_t size,
> > gfp |= __GFP_NOWARN | __GFP_HIGHMEM;
> >
> > while (count) {
> > - int j, order = __fls(count);
> > + int j, order;
> > +
> > + for (order = __fls(count); order > 0; --order) {
> > + /*
> > + * We do not want OOM killer to be invoked as long
> > + * as we can fall back to single pages, so we force
> > + * __GFP_NORETRY for orders higher than zero.
> > + */
> > + pages[i] = alloc_pages(gfp | __GFP_NORETRY, order);
> > + if (pages[i])
> > + break;
> > + }
> >
> > - pages[i] = alloc_pages(gfp, order);
> > - while (!pages[i] && order)
> > - pages[i] = alloc_pages(gfp, --order);
> > - if (!pages[i])
> > - goto error;
> > + if (!pages[i]) {
> > + /*
> > + * Fall back to single page allocation.
> > + * Might invoke OOM killer as last resort.
> > + */
> > + pages[i] = alloc_pages(gfp, 0);
> I think down the code in this while loop, i & count is being
> calculated based on the "order" of allocation in the current
> iteration.
> Since value of order will be automatically 0 here if (!pages[i]) is
> true then, why hard code order to value of 0 here.
> Comment clearly says what this code is doing right?
>
Gcc is smart enough to know that order == 0 here, the code generation on
arm will be the same, so this is only a matter of how the source looks.
To me, it doesn't make a lot of sense to write it as alloc_pages(gfp,
order) when order is always equal to 0. I think it's clearer the way that
Tomasz wrote it.
> I know it is just a minor thing. Don't know if it is relevant.
>
> > + if (!pages[i])
> > + goto error;
> > + }
> >
> > if (order) {
> > split_page(pages[i], order);
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
