diff options
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/mm.h | 5 | ||||
| -rw-r--r-- | include/linux/mm_types.h | 28 |
2 files changed, 17 insertions, 16 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index 51fe207026f8..61a7f680f0ba 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1210,11 +1210,6 @@ static inline int folio_entire_mapcount(const struct folio *folio) return atomic_read(&folio->_entire_mapcount) + 1; } -/* - * The atomic page->_mapcount, starts from -1: so that transitions - * both from it and to it can be tracked, using atomic_inc_and_test - * and atomic_add_negative(-1). - */ static inline void page_mapcount_reset(struct page *page) { atomic_set(&(page)->_mapcount, -1); diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index af3a0256fa93..278eade2ad4c 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -46,9 +46,7 @@ struct mem_cgroup; * which is guaranteed to be aligned. If you use the same storage as * page->mapping, you must restore it to NULL before freeing the page. * - * If your page will not be mapped to userspace, you can also use the four - * bytes in the mapcount union, but you must call page_mapcount_reset() - * before freeing it. + * The mapcount field must not be used for own purposes. * * If you want to use the refcount field, it must be used in such a way * that other CPUs temporarily incrementing and then decrementing the @@ -152,18 +150,26 @@ struct page { union { /* This union is 4 bytes in size. */ /* - * If the page can be mapped to userspace, encodes the number - * of times this page is referenced by a page table. + * For head pages of typed folios, the value stored here + * allows for determining what this page is used for. The + * tail pages of typed folios will not store a type + * (page_type == _mapcount == -1). + * + * See page-flags.h for a list of page types which are currently + * stored here. */ - atomic_t _mapcount; + unsigned int page_type; /* - * If the page is neither PageSlab nor mappable to userspace, - * the value stored here may help determine what this page - * is used for. See page-flags.h for a list of page types - * which are currently stored here. + * For pages that are part of non-typed folios for which mappings + * are tracked via the RMAP, encodes the number of times this page + * is directly referenced by a page table. + * + * Note that the mapcount is always initialized to -1, so that + * transitions both from it and to it can be tracked, using + * atomic_inc_and_test() and atomic_add_negative(-1). */ - unsigned int page_type; + atomic_t _mapcount; }; /* Usage count. *DO NOT USE DIRECTLY*. See page_ref.h */ |