On 1/30/20 3:31 AM, Kirill A. Shutemov wrote: ... >>>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >>>> index 0a55dec68925..b1079aaa6f24 100644 >>>> --- a/mm/huge_memory.c >>>> +++ b/mm/huge_memory.c >>>> @@ -958,6 +958,11 @@ struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr, >>>> */ >>>> WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set"); >>>> + /* FOLL_GET and FOLL_PIN are mutually exclusive. */ >>>> + if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) == >>>> + (FOLL_PIN | FOLL_GET))) >>> >>> Too many parentheses. >> >> >> OK, I'll remove at least one. :) > > I see two. ah, correction: actually, the original statement has exactly the right number of parentheses. The relevant C precedence order is: == & | ...which means that both "&" and "|" operations need parentheses protection from the higher precedence "==" operation. (There are other places in the kernel that have this exact pattern, too, with the same pattern of parentheses that I'm using, of course.) thanks, -- John Hubbard NVIDIA
