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 PG_compound, /* A compound page */
87 PG_swapcache, /* Swap page: swp_entry_t in private */
88 PG_mappedtodisk, /* Has blocks allocated on-disk */
89 PG_reclaim, /* To be reclaimed asap */
90 PG_buddy, /* Page is free, on buddy lists */
91 #ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
92 PG_uncached, /* Page has been mapped as uncached */
97 #ifndef __GENERATING_BOUNDS_H
100 * Macros to create function definitions for page flags
102 #define TESTPAGEFLAG(uname, lname) \
103 static inline int Page##uname(struct page *page) \
104 { return test_bit(PG_##lname, &page->flags); }
106 #define SETPAGEFLAG(uname, lname) \
107 static inline void SetPage##uname(struct page *page) \
108 { set_bit(PG_##lname, &page->flags); }
110 #define CLEARPAGEFLAG(uname, lname) \
111 static inline void ClearPage##uname(struct page *page) \
112 { clear_bit(PG_##lname, &page->flags); }
114 #define __SETPAGEFLAG(uname, lname) \
115 static inline void __SetPage##uname(struct page *page) \
116 { __set_bit(PG_##lname, &page->flags); }
118 #define __CLEARPAGEFLAG(uname, lname) \
119 static inline void __ClearPage##uname(struct page *page) \
120 { __clear_bit(PG_##lname, &page->flags); }
122 #define TESTSETFLAG(uname, lname) \
123 static inline int TestSetPage##uname(struct page *page) \
124 { return test_and_set_bit(PG_##lname, &page->flags); }
126 #define TESTCLEARFLAG(uname, lname) \
127 static inline int TestClearPage##uname(struct page *page) \
128 { return test_and_clear_bit(PG_##lname, &page->flags); }
131 #define PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname) \
132 SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname)
134 #define __PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname) \
135 __SETPAGEFLAG(uname, lname) __CLEARPAGEFLAG(uname, lname)
137 #define TESTSCFLAG(uname, lname) \
138 TESTSETFLAG(uname, lname) TESTCLEARFLAG(uname, lname)
140 struct page; /* forward declaration */
142 PAGEFLAG(Locked, locked) TESTSCFLAG(Locked, locked)
143 PAGEFLAG(Error, error)
144 PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced)
145 PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty, dirty)
146 PAGEFLAG(LRU, lru) __CLEARPAGEFLAG(LRU, lru)
147 PAGEFLAG(Active, active) __CLEARPAGEFLAG(Active, active)
148 __PAGEFLAG(Slab, slab)
149 PAGEFLAG(Checked, owner_priv_1) /* Used by some filesystems */
150 PAGEFLAG(Pinned, owner_priv_1) TESTSCFLAG(Pinned, owner_priv_1) /* Xen */
151 PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
152 PAGEFLAG(Private, private) __CLEARPAGEFLAG(Private, private)
153 __SETPAGEFLAG(Private, private)
156 * Only test-and-set exist for PG_writeback. The unconditional operators are
157 * risky: they bypass page accounting.
159 TESTPAGEFLAG(Writeback, writeback) TESTSCFLAG(Writeback, writeback)
160 __PAGEFLAG(Buddy, buddy)
161 PAGEFLAG(MappedToDisk, mappedtodisk)
163 /* PG_readahead is only used for file reads; PG_reclaim is only for writes */
164 PAGEFLAG(Reclaim, reclaim) TESTCLEARFLAG(Reclaim, reclaim)
165 PAGEFLAG(Readahead, reclaim) /* Reminder to do async read-ahead */
167 #ifdef CONFIG_HIGHMEM
169 * Must use a macro here due to header dependency issues. page_zone() is not
170 * available at this point.
172 #define PageHighMem(__p) is_highmem(page_zone(__p))
174 static inline int PageHighMem(struct page *page)
181 PAGEFLAG(SwapCache, swapcache)
183 static inline int PageSwapCache(struct page *page)
189 #ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
190 PAGEFLAG(Uncached, uncached)
192 static inline int PageUncached(struct page *)
198 static inline int PageUptodate(struct page *page)
200 int ret = test_bit(PG_uptodate, &(page)->flags);
203 * Must ensure that the data we read out of the page is loaded
204 * _after_ we've loaded page->flags to check for PageUptodate.
205 * We can skip the barrier if the page is not uptodate, because
206 * we wouldn't be reading anything from it.
208 * See SetPageUptodate() for the other side of the story.
216 static inline void __SetPageUptodate(struct page *page)
219 __set_bit(PG_uptodate, &(page)->flags);
221 page_clear_dirty(page);
225 static inline void SetPageUptodate(struct page *page)
228 if (!test_and_set_bit(PG_uptodate, &page->flags))
229 page_clear_dirty(page);
232 * Memory barrier must be issued before setting the PG_uptodate bit,
233 * so that all previous stores issued in order to bring the page
234 * uptodate are actually visible before PageUptodate becomes true.
236 * s390 doesn't need an explicit smp_wmb here because the test and
237 * set bit already provides full barriers.
240 set_bit(PG_uptodate, &(page)->flags);
244 CLEARPAGEFLAG(Uptodate, uptodate)
246 extern void cancel_dirty_page(struct page *page, unsigned int account_size);
248 int test_clear_page_writeback(struct page *page);
249 int test_set_page_writeback(struct page *page);
251 static inline void set_page_writeback(struct page *page)
253 test_set_page_writeback(page);
256 TESTPAGEFLAG(Compound, compound)
257 __PAGEFLAG(Head, compound)
260 * PG_reclaim is used in combination with PG_compound to mark the
261 * head and tail of a compound page. This saves one page flag
262 * but makes it impossible to use compound pages for the page cache.
263 * The PG_reclaim bit would have to be used for reclaim or readahead
264 * if compound pages enter the page cache.
266 * PG_compound & PG_reclaim => Tail page
267 * PG_compound & ~PG_reclaim => Head page
269 #define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))
271 static inline int PageTail(struct page *page)
273 return ((page->flags & PG_head_tail_mask) == PG_head_tail_mask);
276 static inline void __SetPageTail(struct page *page)
278 page->flags |= PG_head_tail_mask;
281 static inline void __ClearPageTail(struct page *page)
283 page->flags &= ~PG_head_tail_mask;
286 #endif /* !__GENERATING_BOUNDS_H */
287 #endif /* PAGE_FLAGS_H */