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