On 08.03.22 18:15, Nadav Amit wrote: > > >> On Mar 8, 2022, at 6:14 AM, David Hildenbrand <david@xxxxxxxxxx> wrote: >> >> We want to pass the flags to more than one anon rmap function, getting >> rid of special "do_page_add_anon_rmap()". So let's pass around a distinct >> __bitwise type and refine documentation. >> >> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> >> --- >> include/linux/rmap.h | 22 ++++++++++++++++++---- >> mm/memory.c | 6 +++--- >> mm/rmap.c | 7 ++++--- >> 3 files changed, 25 insertions(+), 10 deletions(-) >> >> diff --git a/include/linux/rmap.h b/include/linux/rmap.h >> index 92c3585b8c6a..49f6b208938c 100644 >> --- a/include/linux/rmap.h >> +++ b/include/linux/rmap.h >> @@ -158,9 +158,23 @@ static inline void anon_vma_merge(struct vm_area_struct *vma, >> >> struct anon_vma *page_get_anon_vma(struct page *page); >> >> -/* bitflags for do_page_add_anon_rmap() */ >> -#define RMAP_EXCLUSIVE 0x01 >> -#define RMAP_COMPOUND 0x02 >> +/* RMAP flags, currently only relevant for some anon rmap operations. */ >> +typedef int __bitwise rmap_t; >> + >> +/* >> + * No special request: if the page is a subpage of a compound page, it is >> + * mapped via a PTE. The mapped (sub)page is possibly shared between processes. >> + */ >> +#define RMAP_NONE ((__force rmap_t)0) >> + >> +/* The (sub)page is exclusive to a single process. */ >> +#define RMAP_EXCLUSIVE ((__force rmap_t)BIT(0)) >> + >> +/* >> + * The compound page is not mapped via PTEs, but instead via a single PMD and >> + * should be accounted accordingly. >> + */ >> +#define RMAP_COMPOUND ((__force rmap_t)BIT(1)) > Hi Nadav, > I was once shouted at for a similar suggestion, but I am going to try > once more… If you already define a new type, why not to use bitfields? I don't have a strong opinion, however, I'd prefer keeping it consistent with existing ways of passing flags. Personally, I like __bitwise because it just behave the way we're used to pass flags -- with additional type safety. Especially once eventually passing many flags (like we do with GFP), bitfields might turn out rather nasty -- IMHO. Thanks! -- Thanks, David / dhildenb
