On Mon, Dec 10, 2018 at 02:35:13PM -0800, Anthony Yznaga wrote: > Certain pages that are never mapped to userspace have a type > indicated in the page_type field of their struct pages (e.g. PG_buddy). > page_type overlaps with _mapcount so set the count to 0 and avoid > calling page_mapcount() for these pages. > > Signed-off-by: Anthony Yznaga <[email protected]> > Acked-by: Matthew Wilcox <[email protected]>
Looks good to me. Reviewed-by: Naoya Horiguchi <[email protected]> > --- > v2 - incorporated feedback from Matthew Wilcox > > fs/proc/page.c | 2 +- > include/linux/page-flags.h | 6 ++++++ > 2 files changed, 7 insertions(+), 1 deletion(-) > > diff --git a/fs/proc/page.c b/fs/proc/page.c > index 6c517b11acf8..40b05e0d4274 100644 > --- a/fs/proc/page.c > +++ b/fs/proc/page.c > @@ -46,7 +46,7 @@ static ssize_t kpagecount_read(struct file *file, char > __user *buf, > ppage = pfn_to_page(pfn); > else > ppage = NULL; > - if (!ppage || PageSlab(ppage)) > + if (!ppage || PageSlab(ppage) || page_has_type(ppage)) > pcount = 0; > else > pcount = page_mapcount(ppage); > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > index 50ce1bddaf56..39b4494e29f1 100644 > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -669,6 +669,7 @@ static inline int TestClearPageDoubleMap(struct page > *page) > > #define PAGE_TYPE_BASE 0xf0000000 > /* Reserve 0x0000007f to catch underflows of page_mapcount */ > +#define PAGE_MAPCOUNT_RESERVE -128 > #define PG_buddy 0x00000080 > #define PG_balloon 0x00000100 > #define PG_kmemcg 0x00000200 > @@ -677,6 +678,11 @@ static inline int TestClearPageDoubleMap(struct page > *page) > #define PageType(page, flag) \ > ((page->page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE) > > +static inline int page_has_type(struct page *page) > +{ > + return (int)page->page_type < PAGE_MAPCOUNT_RESERVE; > +} > + > #define PAGE_TYPE_OPS(uname, lname) \ > static __always_inline int Page##uname(struct page *page) \ > { \ > -- > 1.8.3.1 > >
