On Wed, Aug 18, 2021 at 10:16 AM Roman Gushchin <guro@xxxxxx> wrote:
>
> On Tue, Aug 17, 2021 at 11:30:32AM +0800, Muchun Song wrote:
> > Instead of hard-coding ((1UL << NR_PAGEFLAGS) - 1) everywhere, introducing
> > PAGEFLAGS_MASK to make the code clear to get the page flags.
> >
> > Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> > ---
> > include/linux/page-flags.h | 4 +++-
> > include/trace/events/page_ref.h | 4 ++--
> > lib/test_printf.c | 2 +-
> > lib/vsprintf.c | 2 +-
> > 4 files changed, 7 insertions(+), 5 deletions(-)
> >
> > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> > index 54c4af35c628..1f951ac24a5e 100644
> > --- a/include/linux/page-flags.h
> > +++ b/include/linux/page-flags.h
> > @@ -180,6 +180,8 @@ enum pageflags {
> > PG_reported = PG_uptodate,
> > };
> >
> > +#define PAGEFLAGS_MASK (~((1UL << NR_PAGEFLAGS) - 1))
>
> Hm, isn't it better to invert it? Like
> #define PAGEFLAGS_MASK ((1UL << NR_PAGEFLAGS) - 1)
>
> It feels more usual and will simplify the rest of the patch.
Actually, I learned from PAGE_MASK. So I thought the macro
like xxx_MASK should be the format of 0xff...ff00...00. I don't
know if it is an unwritten rule. I can invert PAGEFLAGS_MASK
if it's not a rule.
Thanks.
>
> Thanks!
>
> > +
> > #ifndef __GENERATING_BOUNDS_H
> >
> > static inline unsigned long _compound_head(const struct page *page)
> > @@ -975,7 +977,7 @@ static inline void ClearPageSlabPfmemalloc(struct page *page)
> > * alloc-free cycle to prevent from reusing the page.
> > */
> > #define PAGE_FLAGS_CHECK_AT_PREP \
> > - (((1UL << NR_PAGEFLAGS) - 1) & ~__PG_HWPOISON)
> > + (~(PAGEFLAGS_MASK | __PG_HWPOISON))
> >
> > #define PAGE_FLAGS_PRIVATE \
> > (1UL << PG_private | 1UL << PG_private_2)
> > diff --git a/include/trace/events/page_ref.h b/include/trace/events/page_ref.h
> > index 5d2ea93956ce..643b1b4e9f27 100644
> > --- a/include/trace/events/page_ref.h
> > +++ b/include/trace/events/page_ref.h
> > @@ -38,7 +38,7 @@ DECLARE_EVENT_CLASS(page_ref_mod_template,
> >
> > TP_printk("pfn=0x%lx flags=%s count=%d mapcount=%d mapping=%p mt=%d val=%d",
> > __entry->pfn,
> > - show_page_flags(__entry->flags & ((1UL << NR_PAGEFLAGS) - 1)),
> > + show_page_flags(__entry->flags & ~PAGEFLAGS_MASK),
> > __entry->count,
> > __entry->mapcount, __entry->mapping, __entry->mt,
> > __entry->val)
> > @@ -88,7 +88,7 @@ DECLARE_EVENT_CLASS(page_ref_mod_and_test_template,
> >
> > TP_printk("pfn=0x%lx flags=%s count=%d mapcount=%d mapping=%p mt=%d val=%d ret=%d",
> > __entry->pfn,
> > - show_page_flags(__entry->flags & ((1UL << NR_PAGEFLAGS) - 1)),
> > + show_page_flags(__entry->flags & ~PAGEFLAGS_MASK),
> > __entry->count,
> > __entry->mapcount, __entry->mapping, __entry->mt,
> > __entry->val, __entry->ret)
> > diff --git a/lib/test_printf.c b/lib/test_printf.c
> > index 8ac71aee46af..eadcc6458b10 100644
> > --- a/lib/test_printf.c
> > +++ b/lib/test_printf.c
> > @@ -614,7 +614,7 @@ page_flags_test(int section, int node, int zone, int last_cpupid,
> > bool append = false;
> > int i;
> >
> > - flags &= BIT(NR_PAGEFLAGS) - 1;
> > + flags &= ~PAGEFLAGS_MASK;
> > if (flags) {
> > page_flags |= flags;
> > snprintf(cmp_buf + size, BUF_SIZE - size, "%s", name);
> > diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> > index dd006adfe853..ff7c180a2971 100644
> > --- a/lib/vsprintf.c
> > +++ b/lib/vsprintf.c
> > @@ -2019,7 +2019,7 @@ static const struct page_flags_fields pff[] = {
> > static
> > char *format_page_flags(char *buf, char *end, unsigned long flags)
> > {
> > - unsigned long main_flags = flags & (BIT(NR_PAGEFLAGS) - 1);
> > + unsigned long main_flags = flags & ~PAGEFLAGS_MASK;
> > bool append = false;
> > int i;
> >
> > --
> > 2.11.0
> >
