> > > * Liang, Kan <kan.li...@intel.com> wrote: > > > > * tip-bot for Kan Liang <tip...@zytor.com> wrote: > > > > > > > --- a/kernel/events/core.c > > > > +++ b/kernel/events/core.c > > > > @@ -4446,7 +4446,7 @@ static int perf_mmap(struct file *file, struct > > > vm_area_struct *vma) > > > > * If we have rb pages ensure they're a power-of-two number, so > > > we > > > > * can do bitmasks instead of modulo. > > > > */ > > > > - if (!is_power_of_2(nr_pages)) > > > > + if (nr_pages != 0 && !is_power_of_2(nr_pages)) > > > > return -EINVAL; > > > > > > Hm, what does is_power_of_2(0) return? It should return 0, because 0 > is > > > not a power of 2! > > > > > > and if it's fixed to return 0, then the check should properly be > something > > > like: > > > > > > if (!nr_pages || !is_power_of_2(nr_pages)) > > > > > > or so? > > > > nr_pages == 0 is valid, we cannot return -EINVAL. Because > > vma_size = vma->vm_end - vma->vm_start; > > nr_pages = (vma_size / PAGE_SIZE) - 1; > > > > So here we only want to check is_power_of_2 > > when the pages > 1 (or nr_pages > 0). > > I don't think you answered my first question, on which my later > comments rely: > > > > Hm, what does is_power_of_2(0) return? It should return 0, because 0 > is > > > not a power of 2!
Yes, is_power_of_2(0) returns 0. Thanks, Kan > > Thanks, > > Ingo -- 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/
