diff options
| -rw-r--r-- | include/linux/mm_types.h | 13 | ||||
| -rw-r--r-- | include/linux/page-flags.h | 45 | ||||
| -rw-r--r-- | kernel/crash_core.c | 1 | ||||
| -rw-r--r-- | mm/page_alloc.c | 13 | ||||
| -rwxr-xr-x | scripts/tags.sh | 6 |
5 files changed, 43 insertions, 35 deletions
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index eb9da245286d..3a554fdf45c2 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -96,6 +96,14 @@ struct page { }; union { + /* + * 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. + */ + unsigned int page_type; + _slub_counter_t counters; unsigned int active; /* SLAB */ struct { /* SLUB */ @@ -109,11 +117,6 @@ struct page { /* * Count of ptes mapped in mms, to show when * page is mapped & limit reverse map searches. - * - * Extra information about page type may be - * stored here for pages that are never mapped, - * in which case the value MUST BE <= -2. - * See page-flags.h for more details. */ atomic_t _mapcount; diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index e34a27727b9a..8c25b28a35aa 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -642,49 +642,56 @@ PAGEFLAG_FALSE(DoubleMap) #endif /* - * For pages that are never mapped to userspace, page->mapcount may be - * used for storing extra information about page type. Any value used - * for this purpose must be <= -2, but it's better start not too close - * to -2 so that an underflow of the page_mapcount() won't be mistaken - * for a special page. + * For pages that are never mapped to userspace (and aren't PageSlab), + * page_type may be used. Because it is initialised to -1, we invert the + * sense of the bit, so __SetPageFoo *clears* the bit used for PageFoo, and + * __ClearPageFoo *sets* the bit used for PageFoo. We reserve a few high and + * low bits so that an underflow or overflow of page_mapcount() won't be + * mistaken for a page type value. */ -#define PAGE_MAPCOUNT_OPS(uname, lname) \ + +#define PAGE_TYPE_BASE 0xf0000000 +/* Reserve 0x0000007f to catch underflows of page_mapcount */ +#define PG_buddy 0x00000080 +#define PG_balloon 0x00000100 +#define PG_kmemcg 0x00000200 + +#define PageType(page, flag) \ + ((page->page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE) + +#define PAGE_TYPE_OPS(uname, lname) \ static __always_inline int Page##uname(struct page *page) \ { \ - return atomic_read(&page->_mapcount) == \ - PAGE_##lname##_MAPCOUNT_VALUE; \ + return PageType(page, PG_##lname); \ } \ static __always_inline void __SetPage##uname(struct page *page) \ { \ - VM_BUG_ON_PAGE(atomic_read(&page->_mapcount) != -1, page); \ - atomic_set(&page->_mapcount, PAGE_##lname##_MAPCOUNT_VALUE); \ + VM_BUG_ON_PAGE(!PageType(page, 0), page); \ + page->page_type &= ~PG_##lname; \ } \ static __always_inline void __ClearPage##uname(struct page *page) \ { \ VM_BUG_ON_PAGE(!Page##uname(page), page); \ - atomic_set(&page->_mapcount, -1); \ + page->page_type |= PG_##lname; \ } /* - * PageBuddy() indicate that the page is free and in the buddy system + * PageBuddy() indicates that the page is free and in the buddy system * (see mm/page_alloc.c). */ -#define PAGE_BUDDY_MAPCOUNT_VALUE (-128) -PAGE_MAPCOUNT_OPS(Buddy, BUDDY) +PAGE_TYPE_OPS(Buddy, buddy) /* - * PageBalloon() is set on pages that are on the balloon page list + * PageBalloon() is true for pages that are on the balloon page list * (see mm/balloon_compaction.c). */ -#define PAGE_BALLOON_MAPCOUNT_VALUE (-256) -PAGE_MAPCOUNT_OPS(Balloon, BALLOON) +PAGE_TYPE_OPS(Balloon, balloon) /* * If kmemcg is enabled, the buddy allocator will set PageKmemcg() on * pages allocated with __GFP_ACCOUNT. It gets cleared on page free. */ -#define PAGE_KMEMCG_MAPCOUNT_VALUE (-512) -PAGE_MAPCOUNT_OPS(Kmemcg, KMEMCG) +PAGE_TYPE_OPS(Kmemcg, kmemcg) extern bool is_free_buddy_page(struct page *page); diff --git a/kernel/crash_core.c b/kernel/crash_core.c index f7674d676889..b66aced5e8c2 100644 --- a/kernel/crash_core.c +++ b/kernel/crash_core.c @@ -460,6 +460,7 @@ static int __init crash_save_vmcoreinfo_init(void) VMCOREINFO_NUMBER(PG_hwpoison); #endif VMCOREINFO_NUMBER(PG_head_mask); +#define PAGE_BUDDY_MAPCOUNT_VALUE (~PG_buddy) VMCOREINFO_NUMBER(PAGE_BUDDY_MAPCOUNT_VALUE); #ifdef CONFIG_HUGETLB_PAGE VMCOREINFO_NUMBER(HUGETLB_PAGE_DTOR); diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 96d48d24e1ef..5afdf495c374 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -705,16 +705,14 @@ static inline void rmv_page_order(struct page *page) /* * This function checks whether a page is free && is the buddy - * we can do coalesce a page and its buddy if + * we can coalesce a page and its buddy if * (a) the buddy is not in a hole (check before calling!) && * (b) the buddy is in the buddy system && * (c) a page and its buddy have the same order && * (d) a page and its buddy are in the same zone. * - * For recording whether a page is in the buddy system, we set ->_mapcount - * PAGE_BUDDY_MAPCOUNT_VALUE. - * Setting, clearing, and testing _mapcount PAGE_BUDDY_MAPCOUNT_VALUE is - * serialized by zone->lock. + * For recording whether a page is in the buddy system, we set PageBuddy. + * Setting, clearing, and testing PageBuddy is serialized by zone->lock. * * For recording page's order, we use page_private(page). */ @@ -759,9 +757,8 @@ static inline int page_is_buddy(struct page *page, struct page *buddy, * as necessary, plus some accounting needed to play nicely with other * parts of the VM system. * At each level, we keep a list of pages, which are heads of continuous - * free pages of length of (1 << order) and marked with _mapcount - * PAGE_BUDDY_MAPCOUNT_VALUE. Page's order is recorded in page_private(page) - * field. + * free pages of length of (1 << order) and marked with PageBuddy. + * Page's order is recorded in page_private(page) field. * So when we are allocating or freeing one, we can derive the state of the * other. That is, if we allocate a small block, and both were * free, the remainder of the region must be split into blocks. diff --git a/scripts/tags.sh b/scripts/tags.sh index e587610d1492..66f08bb1cce9 100755 --- a/scripts/tags.sh +++ b/scripts/tags.sh @@ -179,9 +179,9 @@ regex_c=( '/\<CLEARPAGEFLAG_NOOP(\([[:alnum:]_]*\).*/ClearPage\1/' '/\<__CLEARPAGEFLAG_NOOP(\([[:alnum:]_]*\).*/__ClearPage\1/' '/\<TESTCLEARFLAG_FALSE(\([[:alnum:]_]*\).*/TestClearPage\1/' - '/^PAGE_MAPCOUNT_OPS(\([[:alnum:]_]*\).*/Page\1/' - '/^PAGE_MAPCOUNT_OPS(\([[:alnum:]_]*\).*/__SetPage\1/' - '/^PAGE_MAPCOUNT_OPS(\([[:alnum:]_]*\).*/__ClearPage\1/' + '/^PAGE_TYPE_OPS(\([[:alnum:]_]*\).*/Page\1/' + '/^PAGE_TYPE_OPS(\([[:alnum:]_]*\).*/__SetPage\1/' + '/^PAGE_TYPE_OPS(\([[:alnum:]_]*\).*/__ClearPage\1/' '/^TASK_PFA_TEST([^,]*, *\([[:alnum:]_]*\))/task_\1/' '/^TASK_PFA_SET([^,]*, *\([[:alnum:]_]*\))/task_set_\1/' '/^TASK_PFA_CLEAR([^,]*, *\([[:alnum:]_]*\))/task_clear_\1/' |