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_EXTENDEDPG_head,/* A head page */PG_tail,/* A tail page */#elsePG_compound,/* A compound page */#endifPG_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_ALLOCATORPG_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))#elsePAGEFLAG_FALSE(HighMem)#endif#ifdef CONFIG_SWAPPAGEFLAG(SwapCache, swapcache)#elsePAGEFLAG_FALSE(SwapCache)#endif#ifdef CONFIG_IA64_UNCACHED_ALLOCATORPAGEFLAG(Uncached, uncached)#elsePAGEFLAG_FALSE(Uncached)#endif