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*/
84 PG_private, /* If pagecache, has fs-private data */
85 PG_writeback, /* Page is under writeback */
86 #ifdef CONFIG_PAGEFLAGS_EXTENDED
87 PG_head, /* A head page */
88 PG_tail, /* A tail page */
90 PG_compound, /* A compound page */
92 PG_swapcache, /* Swap page: swp_entry_t in private */
93 PG_mappedtodisk, /* Has blocks allocated on-disk */
94 PG_reclaim, /* To be reclaimed asap */
95 PG_buddy, /* Page is free, on buddy lists */
96 #ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
97 PG_uncached, /* Page has been mapped as uncached */
102 PG_checked = PG_owner_priv_1,
105 PG_pinned = PG_owner_priv_1,
106 PG_savepinned = PG_dirty,
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 PAGEFLAG_FALSE(uname) \
150 static inline int Page##uname(struct page *page) \
153 #define TESTSCFLAG(uname, lname) \
154 TESTSETFLAG(uname, lname) TESTCLEARFLAG(uname, lname)
156 struct page; /* forward declaration */
158 PAGEFLAG(Locked, locked) TESTSCFLAG(Locked, locked)
159 PAGEFLAG(Error, error)
160 PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced)
161 PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty, dirty)
162 PAGEFLAG(LRU, lru) __CLEARPAGEFLAG(LRU, lru)
163 PAGEFLAG(Active, active) __CLEARPAGEFLAG(Active, active)
164 __PAGEFLAG(Slab, slab)
165 PAGEFLAG(Checked, checked) /* Used by some filesystems */
166 PAGEFLAG(Pinned, pinned) TESTSCFLAG(Pinned, pinned) /* Xen */
167 PAGEFLAG(SavePinned, savepinned); /* Xen */
168 PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
169 PAGEFLAG(Private, private) __CLEARPAGEFLAG(Private, private)
170 __SETPAGEFLAG(Private, private)
173 * Only test-and-set exist for PG_writeback. The unconditional operators are
174 * risky: they bypass page accounting.
176 TESTPAGEFLAG(Writeback, writeback) TESTSCFLAG(Writeback, writeback)
177 __PAGEFLAG(Buddy, buddy)
178 PAGEFLAG(MappedToDisk, mappedtodisk)
180 /* PG_readahead is only used for file reads; PG_reclaim is only for writes */
181 PAGEFLAG(Reclaim, reclaim) TESTCLEARFLAG(Reclaim, reclaim)
182 PAGEFLAG(Readahead, reclaim) /* Reminder to do async read-ahead */
184 #ifdef CONFIG_HIGHMEM
186 * Must use a macro here due to header dependency issues. page_zone() is not
187 * available at this point.
189 #define PageHighMem(__p) is_highmem(page_zone(__p))
191 PAGEFLAG_FALSE(HighMem)
195 PAGEFLAG(SwapCache, swapcache)
197 PAGEFLAG_FALSE(SwapCache)
200 #ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
201 PAGEFLAG(Uncached, uncached)
203 PAGEFLAG_FALSE(Uncached)
206 static inline int PageUptodate(struct page *page)
208 int ret = test_bit(PG_uptodate, &(page)->flags);
211 * Must ensure that the data we read out of the page is loaded
212 * _after_ we've loaded page->flags to check for PageUptodate.
213 * We can skip the barrier if the page is not uptodate, because
214 * we wouldn't be reading anything from it.
216 * See SetPageUptodate() for the other side of the story.
224 static inline void __SetPageUptodate(struct page *page)
227 __set_bit(PG_uptodate, &(page)->flags);
229 page_clear_dirty(page);
233 static inline void SetPageUptodate(struct page *page)
236 if (!test_and_set_bit(PG_uptodate, &page->flags))
237 page_clear_dirty(page);
240 * Memory barrier must be issued before setting the PG_uptodate bit,
241 * so that all previous stores issued in order to bring the page
242 * uptodate are actually visible before PageUptodate becomes true.
244 * s390 doesn't need an explicit smp_wmb here because the test and
245 * set bit already provides full barriers.
248 set_bit(PG_uptodate, &(page)->flags);
252 CLEARPAGEFLAG(Uptodate, uptodate)
254 extern void cancel_dirty_page(struct page *page, unsigned int account_size);
256 int test_clear_page_writeback(struct page *page);
257 int test_set_page_writeback(struct page *page);
259 static inline void set_page_writeback(struct page *page)
261 test_set_page_writeback(page);
264 #ifdef CONFIG_PAGEFLAGS_EXTENDED
266 * System with lots of page flags available. This allows separate
267 * flags for PageHead() and PageTail() checks of compound pages so that bit
268 * tests can be used in performance sensitive paths. PageCompound is
269 * generally not used in hot code paths.
271 __PAGEFLAG(Head, head)
272 __PAGEFLAG(Tail, tail)
274 static inline int PageCompound(struct page *page)
276 return page->flags & ((1L << PG_head) | (1L << PG_tail));
281 * Reduce page flag use as much as possible by overlapping
282 * compound page flags with the flags used for page cache pages. Possible
283 * because PageCompound is always set for compound pages and not for
284 * pages on the LRU and/or pagecache.
286 TESTPAGEFLAG(Compound, compound)
287 __PAGEFLAG(Head, compound)
290 * PG_reclaim is used in combination with PG_compound to mark the
291 * head and tail of a compound page. This saves one page flag
292 * but makes it impossible to use compound pages for the page cache.
293 * The PG_reclaim bit would have to be used for reclaim or readahead
294 * if compound pages enter the page cache.
296 * PG_compound & PG_reclaim => Tail page
297 * PG_compound & ~PG_reclaim => Head page
299 #define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))
301 static inline int PageTail(struct page *page)
303 return ((page->flags & PG_head_tail_mask) == PG_head_tail_mask);
306 static inline void __SetPageTail(struct page *page)
308 page->flags |= PG_head_tail_mask;
311 static inline void __ClearPageTail(struct page *page)
313 page->flags &= ~PG_head_tail_mask;
316 #endif /* !PAGEFLAGS_EXTENDED */
318 #define PAGE_FLAGS (1 << PG_lru | 1 << PG_private | 1 << PG_locked | \
319 1 << PG_buddy | 1 << PG_writeback | \
320 1 << PG_slab | 1 << PG_swapcache | 1 << PG_active)
323 * Flags checked in bad_page(). Pages on the free list should not have
324 * these flags set. It they are, there is a problem.
326 #define PAGE_FLAGS_CLEAR_WHEN_BAD (PAGE_FLAGS | 1 << PG_reclaim | 1 << PG_dirty)
329 * Flags checked when a page is freed. Pages being freed should not have
330 * these flags set. It they are, there is a problem.
332 #define PAGE_FLAGS_CHECK_AT_FREE (PAGE_FLAGS | 1 << PG_reserved)
335 * Flags checked when a page is prepped for return by the page allocator.
336 * Pages being prepped should not have these flags set. It they are, there
339 #define PAGE_FLAGS_CHECK_AT_PREP (PAGE_FLAGS | 1 << PG_reserved | 1 << PG_dirty)
341 #endif /* !__GENERATING_BOUNDS_H */
342 #endif /* PAGE_FLAGS_H */