diff options
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/mm.h | 14 | ||||
| -rw-r--r-- | include/linux/page-flags.h | 4 |
2 files changed, 17 insertions, 1 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index 8b6e55ee8855..1a0668e5a4ee 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -297,12 +297,26 @@ static inline int put_page_testzero(struct page *page) /* * Try to grab a ref unless the page has a refcount of zero, return false if * that is the case. + * This can be called when MMU is off so it must not access + * any of the virtual mappings. */ static inline int get_page_unless_zero(struct page *page) { return atomic_inc_not_zero(&page->_count); } +/* + * Try to drop a ref unless the page has a refcount of one, return false if + * that is the case. + * This is to make sure that the refcount won't become zero after this drop. + * This can be called when MMU is off so it must not access + * any of the virtual mappings. + */ +static inline int put_page_unless_one(struct page *page) +{ + return atomic_add_unless(&page->_count, -1, 1); +} + extern int page_is_ram(unsigned long pfn); /* Support for virtually mapped pages */ diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 6d53675c2b54..98ada58f9942 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -329,7 +329,9 @@ static inline void set_page_writeback(struct page *page) * System with lots of page flags available. This allows separate * flags for PageHead() and PageTail() checks of compound pages so that bit * tests can be used in performance sensitive paths. PageCompound is - * generally not used in hot code paths. + * generally not used in hot code paths except arch/powerpc/mm/init_64.c + * and arch/powerpc/kvm/book3s_64_vio_hv.c which use it to detect huge pages + * and avoid handling those in real mode. */ __PAGEFLAG(Head, head) CLEARPAGEFLAG(Head, head) __PAGEFLAG(Tail, tail) |