测试和修改page->flags的操作函数位于哪里？

用Source Insight阅读Linux源码的朋友一定注意到过，类似于PageReserved() PageDirty() PageWriteback()之类的函数，都是白色的，找不到它们的定义在哪里。如图所示：

在kernel/include/linux/page-flags.h 中我们找到了答案：

这些函数都是通过宏展开在编译期生成的。

下面以PageLocked()函数的生成过程为例：

/* PageLocked()的生成过程如下 */ #define TESTPAGEFLAG(uname, lname) / static inline int Page##uname(struct page *page) / { return test_bit(PG_##lname, &page->flags); } TESTPAGEFLAG(Locked, locked) /* 上面的宏展开后得到如下代码： */ static inline int PageLocked(struct page *page) { return test_bit(PG_locked, &page->flags); }

/* * 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, /* Filesystems */ PG_checked = PG_owner_priv_1, /* XEN */ PG_pinned = PG_owner_priv_1, PG_savepinned = PG_dirty, /* SLOB */ PG_slob_page = PG_active, PG_slob_free = PG_private, /* SLUB */ PG_slub_frozen = PG_active, PG_slub_debug = PG_error, }; #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 */ TESTPAGEFLAG(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, checked) /* Used by some filesystems */ PAGEFLAG(Pinned, pinned) TESTSCFLAG(Pinned, pinned) /* Xen */ PAGEFLAG(SavePinned, savepinned); /* Xen */ PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved) PAGEFLAG(Private, private) __CLEARPAGEFLAG(Private, private) __SETPAGEFLAG(Private, private) __PAGEFLAG(SlobPage, slob_page) __PAGEFLAG(SlobFree, slob_free) __PAGEFLAG(SlubFrozen, slub_frozen) __PAGEFLAG(SlubDebug, slub_debug) /* * 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