On 7/14/21 2:17 AM, 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 5922031ffab6..358d3f6fa976 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -178,6 +178,8 @@ enum pageflags {
> PG_reported = PG_uptodate,
> };
>
> +#define PAGEFLAGS_MASK (~((1UL << NR_PAGEFLAGS) - 1))
Can you explain why you chose this definition instead of
#define PAGEFLAGS_MASK ((1UL << NR_PAGEFLAGS) - 1)
and mostly use ~PAGEFLAGS_MASK below?
--
Mike Kravetz
> +
> #ifndef __GENERATING_BOUNDS_H
>
> static inline unsigned long _compound_head(const struct page *page)
> @@ -859,7 +861,7 @@ 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;
>
>
