diff options
Diffstat (limited to 'include/linux/mm_types.h')
| -rw-r--r-- | include/linux/mm_types.h | 21 |
1 files changed, 17 insertions, 4 deletions
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 774b8952deb..10a2f62cd56 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -62,10 +62,23 @@ struct page { struct { union { - atomic_t _mapcount; /* Count of ptes mapped in mms, - * to show when page is mapped - * & limit reverse map searches. - */ + /* + * Count of ptes mapped in + * mms, to show when page is + * mapped & limit reverse map + * searches. + * + * Used also for tail pages + * refcounting instead of + * _count. Tail pages cannot + * be mapped and keeping the + * tail page _count zero at + * all times guarantees + * get_page_unless_zero() will + * never succeed on tail + * pages. + */ + atomic_t _mapcount; struct { unsigned inuse:16; |