/* * Macros for manipulating and testing page->flags */ #ifndef PAGE_FLAGS_H #define PAGE_FLAGS_H #include <linux/types.h> #ifndef __GENERATING_BOUNDS_H #include <linux/mm_types.h> #include <linux/bounds.h> #endif /* !__GENERATING_BOUNDS_H */ /* * Various page->flags bits: * * PG_reserved is set for special pages, which can never be swapped out. Some * of them might not even exist (eg empty_bad_page)... * * The PG_private bitflag is set on pagecache pages if they contain filesystem * specific data (which is normally at page->private). It can be used by * private allocations for its own usage. * * During initiation of disk I/O, PG_locked is set. This bit is set before I/O * and cleared when writeback _starts_ or when read _completes_. PG_writeback * is set before writeback starts and cleared when it finishes. * * PG_locked also pins a page in pagecache, and blocks truncation of the file * while it is held. * * page_waitqueue(page) is a wait queue of all tasks waiting for the page * to become unlocked. * * PG_uptodate tells whether the page's contents is valid. When a read * completes, the page becomes uptodate, unless a disk I/O error happened. * * PG_referenced, PG_reclaim are used for page reclaim for anonymous and * file-backed pagecache (see mm/vmscan.c). * * PG_error is set to indicate that an I/O error occurred on this page. * * PG_arch_1 is an architecture specific page state bit. The generic code * guarantees that this bit is cleared for a page when it first is entered into * the page cache. * * PG_highmem pages are not permanently mapped into the kernel virtual address * space, they need to be kmapped separately for doing IO on the pages. The * struct page (these bits with information) are always mapped into kernel * address space... * * PG_buddy is set to indicate that the page is free and in the buddy system * (see mm/page_alloc.c). * */ /* * Don't use the *_dontuse flags. Use the macros. Otherwise you'll break * locked- and dirty-page accounting. * * The page flags field is split into two parts, the main flags area * which extends from the low bits upwards, and the fields area which * extends from the high bits downwards. * * | FIELD | ... | FLAGS | * N-1 ^ 0 * (NR_PAGEFLAGS) * * The fields area is reserved for fields mapping zone, node (for NUMA) and * SPARSEMEM section (for variants of SPARSEMEM that require section ids like * SPARSEMEM_EXTREME with !SPARSEMEM_VMEMMAP). */ enum pageflags { PG_locked, /* Page is locked. Don't touch. */ PG_error, PG_referenced, PG_uptodate, PG_dirty, PG_lru, PG_active, PG_slab, PG_owner_priv_1, /* Owner use. If pagecache, fs may use*/ PG_arch_1, PG_reserved, PG_private, /* If pagecache, has fs-private data */ PG_writeback, /* Page is under writeback */ #ifdef CONFIG_PAGEFLAGS_EXTENDED PG_head, /* A head page */ PG_tail, /* A tail page */ #else PG_compound, /* A compound page */ #endif PG_swapcache, /* Swap page: swp_entry_t in private */ PG_mappedtodisk, /* Has blocks allocated on-disk */ PG_reclaim, /* To be reclaimed asap */ PG_buddy, /* Page is free, on buddy lists */ #ifdef CONFIG_IA64_UNCACHED_ALLOCATOR PG_uncached, /* Page has been mapped as uncached */ #endif __NR_PAGEFLAGS }; #ifndef __GENERATING_BOUNDS_H /* * Macros to create function definitions for page flags */ #define TESTPAGEFLAG(uname, lname) \ static inline int Page##uname(struct page *page) \ { return test_bit(PG_##lname, &page->flags); } #define SETPAGEFLAG(uname, lname) \ static inline void SetPage##uname(struct page *page) \ { set_bit(PG_##lname, &page->flags); } #define CLEARPAGEFLAG(uname, lname) \ static inline void ClearPage##uname(struct page *page) \ { clear_bit(PG_##lname, &page->flags); } #define __SETPAGEFLAG(uname, lname) \ static inline void __SetPage##uname(struct page *page) \ { __set_bit(PG_##lname, &page->flags); } #define __CLEARPAGEFLAG(uname, lname) \ static inline void __ClearPage##uname(struct page *page) \ { __clear_bit(PG_##lname, &page->flags); } #define TESTSETFLAG(uname, lname) \ static inline int TestSetPage##uname(struct page *page) \ { return test_and_set_bit(PG_##lname, &page->flags); } #define TESTCLEARFLAG(uname, lname) \ static inline int TestClearPage##uname(struct page *page) \ { return test_and_clear_bit(PG_##lname, &page->flags); } #define PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname) \ SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname) #define __PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname) \ __SETPAGEFLAG(uname, lname) __CLEARPAGEFLAG(uname, lname) #define PAGEFLAG_FALSE(uname) \ static inline int Page##uname(struct page *page) \ { return 0; } #define TESTSCFLAG(uname, lname) \ TESTSETFLAG(uname, lname) TESTCLEARFLAG(uname, lname) struct page; /* forward declaration */ PAGEFLAG(Locked, locked) TESTSCFLAG(Locked, locked) PAGEFLAG(Error, error) PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced) PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty, dirty) PAGEFLAG(LRU, lru) __CLEARPAGEFLAG(LRU, lru) PAGEFLAG(Active, active) __CLEARPAGEFLAG(Active, active) __PAGEFLAG(Slab, slab) PAGEFLAG(Checked, owner_priv_1) /* Used by some filesystems */ PAGEFLAG(Pinned, owner_priv_1) TESTSCFLAG(Pinned, owner_priv_1) /* Xen */ PAGEFLAG(SavePinned, dirty); /* Xen */ PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved) PAGEFLAG(Private, private) __CLEARPAGEFLAG(Private, private) __SETPAGEFLAG(Private, private) /* * Only test-and-set exist for PG_writeback. The unconditional operators are * risky: they bypass page accounting. */ TESTPAGEFLAG(Writeback, writeback) TESTSCFLAG(Writeback, writeback) __PAGEFLAG(Buddy, buddy) PAGEFLAG(MappedToDisk, mappedtodisk) /* PG_readahead is only used for file reads; PG_reclaim is only for writes */ PAGEFLAG(Reclaim, reclaim) TESTCLEARFLAG(Reclaim, reclaim) PAGEFLAG(Readahead, reclaim) /* Reminder to do async read-ahead */ #ifdef CONFIG_HIGHMEM /* * Must use a macro here due to header dependency issues. page_zone() is not * available at this point. */ #define PageHighMem(__p) is_highmem(page_zone(__p)) #else PAGEFLAG_FALSE(HighMem) #endif #ifdef CONFIG_SWAP PAGEFLAG(SwapCache, swapcache) #else PAGEFLAG_FALSE(SwapCache) #endif #ifdef CONFIG_IA64_UNCACHED_ALLOCATOR PAGEFLAG(Uncached, uncached) #else PAGEFLAG_FALSE(Uncached) #endif static inline int PageUptodate(struct page *page) { int ret = test_bit(PG_uptodate, &(page)->flags); /* * Must ensure that the data we read out of the page is loaded * _after_ we've loaded page->flags to check for PageUptodate. * We can skip the barrier if the page is not uptodate, because * we wouldn't be reading anything from it. * * See SetPageUptodate() for the other side of the story. */ if (ret) smp_rmb(); return ret; } static inline void __SetPageUptodate(struct page *page) { smp_wmb(); __set_bit(PG_uptodate, &(page)->flags); #ifdef CONFIG_S390 page_clear_dirty(page); #endif } static inline void SetPageUptodate(struct page *page) { #ifdef CONFIG_S390 if (!test_and_set_bit(PG_uptodate, &page->flags)) page_clear_dirty(page); #else /* * Memory barrier must be issued before setting the PG_uptodate bit, * so that all previous stores issued in order to bring the page * uptodate are actually visible before PageUptodate becomes true. * * s390 doesn't need an explicit smp_wmb here because the test and * set bit already provides full barriers. */ smp_wmb(); set_bit(PG_uptodate, &(page)->flags); #endif } CLEARPAGEFLAG(Uptodate, uptodate) extern void cancel_dirty_page(struct page *page, unsigned int account_size); int test_clear_page_writeback(struct page *page); int test_set_page_writeback(struct page *page); static inline void set_page_writeback(struct page *page) { test_set_page_writeback(page); } #ifdef CONFIG_PAGEFLAGS_EXTENDED /* * 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. */ __PAGEFLAG(Head, head) __PAGEFLAG(Tail, tail) static inline int PageCompound(struct page *page) { return page->flags & ((1L << PG_head) | (1L << PG_tail)); } #else /* * Reduce page flag use as much as possible by overlapping * compound page flags with the flags used for page cache pages. Possible * because PageCompound is always set for compound pages and not for * pages on the LRU and/or pagecache. */ TESTPAGEFLAG(Compound, compound) __PAGEFLAG(Head, compound) /* * PG_reclaim is used in combination with PG_compound to mark the * head and tail of a compound page. This saves one page flag * but makes it impossible to use compound pages for the page cache. * The PG_reclaim bit would have to be used for reclaim or readahead * if compound pages enter the page cache. * * PG_compound & PG_reclaim => Tail page * PG_compound & ~PG_reclaim => Head page */ #define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim)) static inline int PageTail(struct page *page) { return ((page->flags & PG_head_tail_mask) == PG_head_tail_mask); } static inline void __SetPageTail(struct page *page) { page->flags |= PG_head_tail_mask; } static inline void __ClearPageTail(struct page *page) { page->flags &= ~PG_head_tail_mask; } #endif /* !PAGEFLAGS_EXTENDED */ #define PAGE_FLAGS (1 << PG_lru | 1 << PG_private | 1 << PG_locked | \ 1 << PG_buddy | 1 << PG_writeback | \ 1 << PG_slab | 1 << PG_swapcache | 1 << PG_active) /* * Flags checked in bad_page(). Pages on the free list should not have * these flags set. It they are, there is a problem. */ #define PAGE_FLAGS_CLEAR_WHEN_BAD (PAGE_FLAGS | 1 << PG_reclaim | 1 << PG_dirty) /* * Flags checked when a page is freed. Pages being freed should not have * these flags set. It they are, there is a problem. */ #define PAGE_FLAGS_CHECK_AT_FREE (PAGE_FLAGS | 1 << PG_reserved) /* * Flags checked when a page is prepped for return by the page allocator. * Pages being prepped should not have these flags set. It they are, there * is a problem. */ #define PAGE_FLAGS_CHECK_AT_PREP (PAGE_FLAGS | 1 << PG_reserved | 1 << PG_dirty) #endif /* !__GENERATING_BOUNDS_H */ #endif /* PAGE_FLAGS_H */