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 */
92 #if (BITS_PER_LONG > 32)
94 * 64-bit-only flags build down from bit 31
96 * 32 bit -------------------------------| FIELDS | FLAGS |
97 * 64 bit | FIELDS | ?????? FLAGS |
100 PG_uncached = 31, /* Page has been mapped as uncached */
105 #ifndef __GENERATING_BOUNDS_H
108 * Macros to create function definitions for page flags
110 #define TESTPAGEFLAG(uname, lname) \
111 static inline int Page##uname(struct page *page) \
112 { return test_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 __SETPAGEFLAG(uname, lname) \
123 static inline void __SetPage##uname(struct page *page) \
124 { __set_bit(PG_##lname, &page->flags); }
126 #define __CLEARPAGEFLAG(uname, lname) \
127 static inline void __ClearPage##uname(struct page *page) \
128 { __clear_bit(PG_##lname, &page->flags); }
130 #define TESTSETFLAG(uname, lname) \
131 static inline int TestSetPage##uname(struct page *page) \
132 { return test_and_set_bit(PG_##lname, &page->flags); }
134 #define TESTCLEARFLAG(uname, lname) \
135 static inline int TestClearPage##uname(struct page *page) \
136 { return test_and_clear_bit(PG_##lname, &page->flags); }
139 #define PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname) \
140 SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname)
142 #define __PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname) \
143 __SETPAGEFLAG(uname, lname) __CLEARPAGEFLAG(uname, lname)
145 #define TESTSCFLAG(uname, lname) \
146 TESTSETFLAG(uname, lname) TESTCLEARFLAG(uname, lname)
148 struct page; /* forward declaration */
150 PAGEFLAG(Locked, locked) TESTSCFLAG(Locked, locked)
151 PAGEFLAG(Error, error)
152 PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced)
153 PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty, dirty)
154 PAGEFLAG(LRU, lru) __CLEARPAGEFLAG(LRU, lru)
155 PAGEFLAG(Active, active) __CLEARPAGEFLAG(Active, active)
156 __PAGEFLAG(Slab, slab)
157 PAGEFLAG(Checked, owner_priv_1) /* Used by some filesystems */
158 PAGEFLAG(Pinned, owner_priv_1) TESTSCFLAG(Pinned, owner_priv_1) /* Xen */
159 PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
160 PAGEFLAG(Private, private) __CLEARPAGEFLAG(Private, private)
161 __SETPAGEFLAG(Private, private)
164 * Only test-and-set exist for PG_writeback. The unconditional operators are
165 * risky: they bypass page accounting.
167 TESTPAGEFLAG(Writeback, writeback) TESTSCFLAG(Writeback, writeback)
168 __PAGEFLAG(Buddy, buddy)
169 PAGEFLAG(MappedToDisk, mappedtodisk)
171 /* PG_readahead is only used for file reads; PG_reclaim is only for writes */
172 PAGEFLAG(Reclaim, reclaim) TESTCLEARFLAG(Reclaim, reclaim)
173 PAGEFLAG(Readahead, reclaim) /* Reminder to do async read-ahead */
175 #ifdef CONFIG_HIGHMEM
177 * Must use a macro here due to header dependency issues. page_zone() is not
178 * available at this point.
180 #define PageHighMem(__p) is_highmem(page_zone(__p))
182 static inline int PageHighMem(struct page *page)
189 PAGEFLAG(SwapCache, swapcache)
191 static inline int PageSwapCache(struct page *page)
197 #if (BITS_PER_LONG > 32)
198 PAGEFLAG(Uncached, uncached)
201 static inline int PageUptodate(struct page *page)
203 int ret = test_bit(PG_uptodate, &(page)->flags);
206 * Must ensure that the data we read out of the page is loaded
207 * _after_ we've loaded page->flags to check for PageUptodate.
208 * We can skip the barrier if the page is not uptodate, because
209 * we wouldn't be reading anything from it.
211 * See SetPageUptodate() for the other side of the story.
219 static inline void __SetPageUptodate(struct page *page)
222 __set_bit(PG_uptodate, &(page)->flags);
224 page_clear_dirty(page);
228 static inline void SetPageUptodate(struct page *page)
231 if (!test_and_set_bit(PG_uptodate, &page->flags))
232 page_clear_dirty(page);
235 * Memory barrier must be issued before setting the PG_uptodate bit,
236 * so that all previous stores issued in order to bring the page
237 * uptodate are actually visible before PageUptodate becomes true.
239 * s390 doesn't need an explicit smp_wmb here because the test and
240 * set bit already provides full barriers.
243 set_bit(PG_uptodate, &(page)->flags);
247 CLEARPAGEFLAG(Uptodate, uptodate)
249 extern void cancel_dirty_page(struct page *page, unsigned int account_size);
251 int test_clear_page_writeback(struct page *page);
252 int test_set_page_writeback(struct page *page);
254 static inline void set_page_writeback(struct page *page)
256 test_set_page_writeback(page);
259 TESTPAGEFLAG(Compound, compound)
260 __PAGEFLAG(Head, compound)
263 * PG_reclaim is used in combination with PG_compound to mark the
264 * head and tail of a compound page. This saves one page flag
265 * but makes it impossible to use compound pages for the page cache.
266 * The PG_reclaim bit would have to be used for reclaim or readahead
267 * if compound pages enter the page cache.
269 * PG_compound & PG_reclaim => Tail page
270 * PG_compound & ~PG_reclaim => Head page
272 #define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))
274 static inline int PageTail(struct page *page)
276 return ((page->flags & PG_head_tail_mask) == PG_head_tail_mask);
279 static inline void __SetPageTail(struct page *page)
281 page->flags |= PG_head_tail_mask;
284 static inline void __ClearPageTail(struct page *page)
286 page->flags &= ~PG_head_tail_mask;
289 #endif /* !__GENERATING_BOUNDS_H */
290 #endif /* PAGE_FLAGS_H */