2 * Macros for manipulating and testing page->flags
8 #include <linux/types.h>
9 #ifndef __GENERATING_BOUNDS_H
10 #include <linux/mm_types.h>
11 #include <linux/bounds.h>
12 #endif /* !__GENERATING_BOUNDS_H */
15 * Various page->flags bits:
17 * PG_reserved is set for special pages, which can never be swapped out. Some
18 * of them might not even exist (eg empty_bad_page)...
20 * The PG_private bitflag is set on pagecache pages if they contain filesystem
21 * specific data (which is normally at page->private). It can be used by
22 * private allocations for its own usage.
24 * During initiation of disk I/O, PG_locked is set. This bit is set before I/O
25 * and cleared when writeback _starts_ or when read _completes_. PG_writeback
26 * is set before writeback starts and cleared when it finishes.
28 * PG_locked also pins a page in pagecache, and blocks truncation of the file
31 * page_waitqueue(page) is a wait queue of all tasks waiting for the page
34 * PG_uptodate tells whether the page's contents is valid. When a read
35 * completes, the page becomes uptodate, unless a disk I/O error happened.
37 * PG_referenced, PG_reclaim are used for page reclaim for anonymous and
38 * file-backed pagecache (see mm/vmscan.c).
40 * PG_error is set to indicate that an I/O error occurred on this page.
42 * PG_arch_1 is an architecture specific page state bit. The generic code
43 * guarantees that this bit is cleared for a page when it first is entered into
46 * PG_highmem pages are not permanently mapped into the kernel virtual address
47 * space, they need to be kmapped separately for doing IO on the pages. The
48 * struct page (these bits with information) are always mapped into kernel
51 * PG_buddy is set to indicate that the page is free and in the buddy system
52 * (see mm/page_alloc.c).
57 * Don't use the *_dontuse flags. Use the macros. Otherwise you'll break
58 * locked- and dirty-page accounting.
60 * The page flags field is split into two parts, the main flags area
61 * which extends from the low bits upwards, and the fields area which
62 * extends from the high bits downwards.
64 * | FIELD | ... | FLAGS |
68 * The fields area is reserved for fields mapping zone, node (for NUMA) and
69 * SPARSEMEM section (for variants of SPARSEMEM that require section ids like
70 * SPARSEMEM_EXTREME with !SPARSEMEM_VMEMMAP).
73 PG_locked, /* Page is locked. Don't touch. */
81 PG_owner_priv_1, /* Owner use. If pagecache, fs may use*/
82 PG_checked = PG_owner_priv_1, /* Used by some filesystems */
83 PG_pinned = PG_owner_priv_1, /* Xen pinned pagetable */
86 PG_private, /* If pagecache, has fs-private data */
87 PG_writeback, /* Page is under writeback */
88 PG_compound, /* A compound page */
89 PG_swapcache, /* Swap page: swp_entry_t in private */
90 PG_mappedtodisk, /* Has blocks allocated on-disk */
91 PG_reclaim, /* To be reclaimed asap */
92 /* PG_readahead is only used for file reads; PG_reclaim is only for writes */
93 PG_readahead = PG_reclaim, /* Reminder to do async read-ahead */
94 PG_buddy, /* Page is free, on buddy lists */
96 #if (BITS_PER_LONG > 32)
98 * 64-bit-only flags build down from bit 31
100 * 32 bit -------------------------------| FIELDS | FLAGS |
101 * 64 bit | FIELDS | ?????? FLAGS |
104 PG_uncached = 31, /* Page has been mapped as uncached */
109 #ifndef __GENERATING_BOUNDS_H
112 * Macros to create function definitions for page flags
114 #define TESTPAGEFLAG(uname, lname) \
115 static inline int Page##uname(struct page *page) \
116 { return test_bit(PG_##lname, &page->flags); }
118 #define SETPAGEFLAG(uname, lname) \
119 static inline void SetPage##uname(struct page *page) \
120 { set_bit(PG_##lname, &page->flags); }
122 #define CLEARPAGEFLAG(uname, lname) \
123 static inline void ClearPage##uname(struct page *page) \
124 { clear_bit(PG_##lname, &page->flags); }
126 #define __SETPAGEFLAG(uname, lname) \
127 static inline void __SetPage##uname(struct page *page) \
128 { __set_bit(PG_##lname, &page->flags); }
130 #define __CLEARPAGEFLAG(uname, lname) \
131 static inline void __ClearPage##uname(struct page *page) \
132 { __clear_bit(PG_##lname, &page->flags); }
134 #define TESTSETFLAG(uname, lname) \
135 static inline int TestSetPage##uname(struct page *page) \
136 { return test_and_set_bit(PG_##lname, &page->flags); }
138 #define TESTCLEARFLAG(uname, lname) \
139 static inline int TestClearPage##uname(struct page *page) \
140 { return test_and_clear_bit(PG_##lname, &page->flags); }
143 #define PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname) \
144 SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname)
146 #define __PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname) \
147 __SETPAGEFLAG(uname, lname) __CLEARPAGEFLAG(uname, lname)
149 #define TESTSCFLAG(uname, lname) \
150 TESTSETFLAG(uname, lname) TESTCLEARFLAG(uname, lname)
152 struct page; /* forward declaration */
154 PAGEFLAG(Locked, locked) TESTSCFLAG(Locked, locked)
155 PAGEFLAG(Error, error)
156 PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced)
157 PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty, dirty)
158 PAGEFLAG(LRU, lru) __CLEARPAGEFLAG(LRU, lru)
159 PAGEFLAG(Active, active) __CLEARPAGEFLAG(Active, active)
160 __PAGEFLAG(Slab, slab)
161 PAGEFLAG(Checked, checked) /* Used by some filesystems */
162 PAGEFLAG(Pinned, pinned) /* Xen pinned pagetable */
163 PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
164 PAGEFLAG(Private, private) __CLEARPAGEFLAG(Private, private)
165 __SETPAGEFLAG(Private, private)
168 * Only test-and-set exist for PG_writeback. The unconditional operators are
169 * risky: they bypass page accounting.
171 TESTPAGEFLAG(Writeback, writeback) TESTSCFLAG(Writeback, writeback)
172 __PAGEFLAG(Buddy, buddy)
173 PAGEFLAG(MappedToDisk, mappedtodisk)
175 /* PG_readahead is only used for file reads; PG_reclaim is only for writes */
176 PAGEFLAG(Reclaim, reclaim) TESTCLEARFLAG(Reclaim, reclaim)
177 PAGEFLAG(Readahead, readahead) /* Reminder to do async read-ahead */
179 #ifdef CONFIG_HIGHMEM
181 * Must use a macro here due to header dependency issues. page_zone() is not
182 * available at this point.
184 #define PageHighMem(__p) is_highmem(page_zone(page))
186 static inline int PageHighMem(struct page *page)
193 PAGEFLAG(SwapCache, swapcache)
195 static inline int PageSwapCache(struct page *page)
201 #if (BITS_PER_LONG > 32)
202 PAGEFLAG(Uncached, uncached)
205 static inline int PageUptodate(struct page *page)
207 int ret = test_bit(PG_uptodate, &(page)->flags);
210 * Must ensure that the data we read out of the page is loaded
211 * _after_ we've loaded page->flags to check for PageUptodate.
212 * We can skip the barrier if the page is not uptodate, because
213 * we wouldn't be reading anything from it.
215 * See SetPageUptodate() for the other side of the story.
223 static inline void __SetPageUptodate(struct page *page)
226 __set_bit(PG_uptodate, &(page)->flags);
228 page_clear_dirty(page);
232 static inline void SetPageUptodate(struct page *page)
235 if (!test_and_set_bit(PG_uptodate, &page->flags))
236 page_clear_dirty(page);
239 * Memory barrier must be issued before setting the PG_uptodate bit,
240 * so that all previous stores issued in order to bring the page
241 * uptodate are actually visible before PageUptodate becomes true.
243 * s390 doesn't need an explicit smp_wmb here because the test and
244 * set bit already provides full barriers.
247 set_bit(PG_uptodate, &(page)->flags);
251 CLEARPAGEFLAG(Uptodate, uptodate)
253 extern void cancel_dirty_page(struct page *page, unsigned int account_size);
255 int test_clear_page_writeback(struct page *page);
256 int test_set_page_writeback(struct page *page);
258 static inline void set_page_writeback(struct page *page)
260 test_set_page_writeback(page);
263 TESTPAGEFLAG(Compound, compound)
264 __PAGEFLAG(Head, compound)
267 * PG_reclaim is used in combination with PG_compound to mark the
268 * head and tail of a compound page. This saves one page flag
269 * but makes it impossible to use compound pages for the page cache.
270 * The PG_reclaim bit would have to be used for reclaim or readahead
271 * if compound pages enter the page cache.
273 * PG_compound & PG_reclaim => Tail page
274 * PG_compound & ~PG_reclaim => Head page
276 #define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))
278 static inline int PageTail(struct page *page)
280 return ((page->flags & PG_head_tail_mask) == PG_head_tail_mask);
283 static inline void __SetPageTail(struct page *page)
285 page->flags |= PG_head_tail_mask;
288 static inline void __ClearPageTail(struct page *page)
290 page->flags &= ~PG_head_tail_mask;
293 #endif /* !__GENERATING_BOUNDS_H */
294 #endif /* PAGE_FLAGS_H */