1 /*
2 * Macros for manipulating and testing page->flags
3 */
4
5 #ifndef PAGE_FLAGS_H
6 #define PAGE_FLAGS_H
7
8 #include <linux/types.h>
9 #include <linux/mm_types.h>
10
11 /*
12 * Various page->flags bits:
13 *
14 * PG_reserved is set for special pages, which can never be swapped out. Some
15 * of them might not even exist (eg empty_bad_page)...
16 *
17 * The PG_private bitflag is set on pagecache pages if they contain filesystem
18 * specific data (which is normally at page->private). It can be used by
19 * private allocations for its own usage.
20 *
21 * During initiation of disk I/O, PG_locked is set. This bit is set before I/O
22 * and cleared when writeback _starts_ or when read _completes_. PG_writeback
23 * is set before writeback starts and cleared when it finishes.
24 *
25 * PG_locked also pins a page in pagecache, and blocks truncation of the file
26 * while it is held.
27 *
28 * page_waitqueue(page) is a wait queue of all tasks waiting for the page
29 * to become unlocked.
30 *
31 * PG_uptodate tells whether the page's contents is valid. When a read
32 * completes, the page becomes uptodate, unless a disk I/O error happened.
33 *
34 * PG_referenced, PG_reclaim are used for page reclaim for anonymous and
35 * file-backed pagecache (see mm/vmscan.c).
36 *
37 * PG_error is set to indicate that an I/O error occurred on this page.
38 *
39 * PG_arch_1 is an architecture specific page state bit. The generic code
40 * guarantees that this bit is cleared for a page when it first is entered into
41 * the page cache.
42 *
43 * PG_highmem pages are not permanently mapped into the kernel virtual address
44 * space, they need to be kmapped separately for doing IO on the pages. The
45 * struct page (these bits with information) are always mapped into kernel
46 * address space...
47 *
48 * PG_buddy is set to indicate that the page is free and in the buddy system
49 * (see mm/page_alloc.c).
50 *
51 */
52
53 /*
54 * Don't use the *_dontuse flags. Use the macros. Otherwise you'll break
55 * locked- and dirty-page accounting.
56 *
57 * The page flags field is split into two parts, the main flags area
58 * which extends from the low bits upwards, and the fields area which
59 * extends from the high bits downwards.
60 *
61 * | FIELD | ... | FLAGS |
62 * N-1 ^ 0
63 * (N-FLAGS_RESERVED)
64 *
65 * The fields area is reserved for fields mapping zone, node and SPARSEMEM
66 * section. The boundry between these two areas is defined by
67 * FLAGS_RESERVED which defines the width of the fields section
68 * (see linux/mmzone.h). New flags must _not_ overlap with this area.
69 */
70 #define PG_locked 0 /* Page is locked. Don't touch. */
71 #define PG_error 1
72 #define PG_referenced 2
73 #define PG_uptodate 3
74
75 #define PG_dirty 4
76 #define PG_lru 5
77 #define PG_active 6
78 #define PG_slab 7 /* slab debug (Suparna wants this) */
79
80 #define PG_owner_priv_1 8 /* Owner use. If pagecache, fs may use*/
81 #define PG_arch_1 9
82 #define PG_reserved 10
83 #define PG_private 11 /* If pagecache, has fs-private data */
84
85 #define PG_writeback 12 /* Page is under writeback */
86 #define PG_compound 14 /* Part of a compound page */
87 #define PG_swapcache 15 /* Swap page: swp_entry_t in private */
88
89 #define PG_mappedtodisk 16 /* Has blocks allocated on-disk */
90 #define PG_reclaim 17 /* To be reclaimed asap */
91 #define PG_buddy 19 /* Page is free, on buddy lists */
92
93 /* PG_readahead is only used for file reads; PG_reclaim is only for writes */
94 #define PG_readahead PG_reclaim /* Reminder to do async read-ahead */
95
96 /* PG_owner_priv_1 users should have descriptive aliases */
97 #define PG_checked PG_owner_priv_1 /* Used by some filesystems */
98 #define PG_pinned PG_owner_priv_1 /* Xen pinned pagetable */
99
100 #if (BITS_PER_LONG > 32)
101 /*
102 * 64-bit-only flags build down from bit 31
103 *
104 * 32 bit -------------------------------| FIELDS | FLAGS |
105 * 64 bit | FIELDS | ?????? FLAGS |
106 * 63 32 0
107 */
108 #define PG_uncached 31 /* Page has been mapped as uncached */
109 #endif
110
111 /*
112 * Manipulation of page state flags
113 */
114 #define PageLocked(page) \
115 test_bit(PG_locked, &(page)->flags)
116 #define SetPageLocked(page) \
117 set_bit(PG_locked, &(page)->flags)
118 #define TestSetPageLocked(page) \
119 test_and_set_bit(PG_locked, &(page)->flags)
120 #define ClearPageLocked(page) \
121 clear_bit(PG_locked, &(page)->flags)
122 #define TestClearPageLocked(page) \
123 test_and_clear_bit(PG_locked, &(page)->flags)
124
125 #define PageError(page) test_bit(PG_error, &(page)->flags)
126 #define SetPageError(page) set_bit(PG_error, &(page)->flags)
127 #define ClearPageError(page) clear_bit(PG_error, &(page)->flags)
128
129 #define PageReferenced(page) test_bit(PG_referenced, &(page)->flags)
130 #define SetPageReferenced(page) set_bit(PG_referenced, &(page)->flags)
131 #define ClearPageReferenced(page) clear_bit(PG_referenced, &(page)->flags)
132 #define TestClearPageReferenced(page) test_and_clear_bit(PG_referenced, &(page)->flags)
133
134 static inline int PageUptodate(struct page *page)
135 {
136 int ret = test_bit(PG_uptodate, &(page)->flags);
137
138 /*
139 * Must ensure that the data we read out of the page is loaded
140 * _after_ we've loaded page->flags to check for PageUptodate.
141 * We can skip the barrier if the page is not uptodate, because
142 * we wouldn't be reading anything from it.
143 *
144 * See SetPageUptodate() for the other side of the story.
145 */
146 if (ret)
147 smp_rmb();
148
149 return ret;
150 }
151
152 static inline void __SetPageUptodate(struct page *page)
153 {
154 smp_wmb();
155 __set_bit(PG_uptodate, &(page)->flags);
156 #ifdef CONFIG_S390
157 page_clear_dirty(page);
158 #endif
159 }
160
161 static inline void SetPageUptodate(struct page *page)
162 {
163 #ifdef CONFIG_S390
164 if (!test_and_set_bit(PG_uptodate, &page->flags))
165 page_clear_dirty(page);
166 #else
167 /*
168 * Memory barrier must be issued before setting the PG_uptodate bit,
169 * so that all previous stores issued in order to bring the page
170 * uptodate are actually visible before PageUptodate becomes true.
171 *
172 * s390 doesn't need an explicit smp_wmb here because the test and
173 * set bit already provides full barriers.
174 */
175 smp_wmb();
176 set_bit(PG_uptodate, &(page)->flags);
177 #endif
178 }
179
180 #define ClearPageUptodate(page) clear_bit(PG_uptodate, &(page)->flags)
181
182 #define PageDirty(page) test_bit(PG_dirty, &(page)->flags)
183 #define SetPageDirty(page) set_bit(PG_dirty, &(page)->flags)
184 #define TestSetPageDirty(page) test_and_set_bit(PG_dirty, &(page)->flags)
185 #define ClearPageDirty(page) clear_bit(PG_dirty, &(page)->flags)
186 #define __ClearPageDirty(page) __clear_bit(PG_dirty, &(page)->flags)
187 #define TestClearPageDirty(page) test_and_clear_bit(PG_dirty, &(page)->flags)
188
189 #define PageLRU(page) test_bit(PG_lru, &(page)->flags)
190 #define SetPageLRU(page) set_bit(PG_lru, &(page)->flags)
191 #define ClearPageLRU(page) clear_bit(PG_lru, &(page)->flags)
192 #define __ClearPageLRU(page) __clear_bit(PG_lru, &(page)->flags)
193
194 #define PageActive(page) test_bit(PG_active, &(page)->flags)
195 #define SetPageActive(page) set_bit(PG_active, &(page)->flags)
196 #define ClearPageActive(page) clear_bit(PG_active, &(page)->flags)
197 #define __ClearPageActive(page) __clear_bit(PG_active, &(page)->flags)
198
199 #define PageSlab(page) test_bit(PG_slab, &(page)->flags)
200 #define __SetPageSlab(page) __set_bit(PG_slab, &(page)->flags)
201 #define __ClearPageSlab(page) __clear_bit(PG_slab, &(page)->flags)
202
203 #ifdef CONFIG_HIGHMEM
204 #define PageHighMem(page) is_highmem(page_zone(page))
205 #else
206 #define PageHighMem(page) 0 /* needed to optimize away at compile time */
207 #endif
208
209 #define PageChecked(page) test_bit(PG_checked, &(page)->flags)
210 #define SetPageChecked(page) set_bit(PG_checked, &(page)->flags)
211 #define ClearPageChecked(page) clear_bit(PG_checked, &(page)->flags)
212
213 #define PagePinned(page) test_bit(PG_pinned, &(page)->flags)
214 #define SetPagePinned(page) set_bit(PG_pinned, &(page)->flags)
215 #define ClearPagePinned(page) clear_bit(PG_pinned, &(page)->flags)
216
217 #define PageReserved(page) test_bit(PG_reserved, &(page)->flags)
218 #define SetPageReserved(page) set_bit(PG_reserved, &(page)->flags)
219 #define ClearPageReserved(page) clear_bit(PG_reserved, &(page)->flags)
220 #define __ClearPageReserved(page) __clear_bit(PG_reserved, &(page)->flags)
221
222 #define SetPagePrivate(page) set_bit(PG_private, &(page)->flags)
223 #define ClearPagePrivate(page) clear_bit(PG_private, &(page)->flags)
224 #define PagePrivate(page) test_bit(PG_private, &(page)->flags)
225 #define __SetPagePrivate(page) __set_bit(PG_private, &(page)->flags)
226 #define __ClearPagePrivate(page) __clear_bit(PG_private, &(page)->flags)
227
228 /*
229 * Only test-and-set exist for PG_writeback. The unconditional operators are
230 * risky: they bypass page accounting.
231 */
232 #define PageWriteback(page) test_bit(PG_writeback, &(page)->flags)
233 #define TestSetPageWriteback(page) test_and_set_bit(PG_writeback, \
234 &(page)->flags)
235 #define TestClearPageWriteback(page) test_and_clear_bit(PG_writeback, \
236 &(page)->flags)
237
238 #define PageBuddy(page) test_bit(PG_buddy, &(page)->flags)
239 #define __SetPageBuddy(page) __set_bit(PG_buddy, &(page)->flags)
240 #define __ClearPageBuddy(page) __clear_bit(PG_buddy, &(page)->flags)
241
242 #define PageMappedToDisk(page) test_bit(PG_mappedtodisk, &(page)->flags)
243 #define SetPageMappedToDisk(page) set_bit(PG_mappedtodisk, &(page)->flags)
244 #define ClearPageMappedToDisk(page) clear_bit(PG_mappedtodisk, &(page)->flags)
245
246 #define PageReadahead(page) test_bit(PG_readahead, &(page)->flags)
247 #define SetPageReadahead(page) set_bit(PG_readahead, &(page)->flags)
248 #define ClearPageReadahead(page) clear_bit(PG_readahead, &(page)->flags)
249
250 #define PageReclaim(page) test_bit(PG_reclaim, &(page)->flags)
251 #define SetPageReclaim(page) set_bit(PG_reclaim, &(page)->flags)
252 #define ClearPageReclaim(page) clear_bit(PG_reclaim, &(page)->flags)
253 #define TestClearPageReclaim(page) test_and_clear_bit(PG_reclaim, &(page)->flags)
254
255 #define PageCompound(page) test_bit(PG_compound, &(page)->flags)
256 #define __SetPageCompound(page) __set_bit(PG_compound, &(page)->flags)
257 #define __ClearPageCompound(page) __clear_bit(PG_compound, &(page)->flags)
258
259 /*
260 * PG_reclaim is used in combination with PG_compound to mark the
261 * head and tail of a compound page
262 *
263 * PG_compound & PG_reclaim => Tail page
264 * PG_compound & ~PG_reclaim => Head page
265 */
266
267 #define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))
268
269 #define PageTail(page) (((page)->flags & PG_head_tail_mask) \
270 == PG_head_tail_mask)
271
272 static inline void __SetPageTail(struct page *page)
273 {
274 page->flags |= PG_head_tail_mask;
275 }
276
277 static inline void __ClearPageTail(struct page *page)
278 {
279 page->flags &= ~PG_head_tail_mask;
280 }
281
282 #define PageHead(page) (((page)->flags & PG_head_tail_mask) \
283 == (1L << PG_compound))
284 #define __SetPageHead(page) __SetPageCompound(page)
285 #define __ClearPageHead(page) __ClearPageCompound(page)
286
287 #ifdef CONFIG_SWAP
288 #define PageSwapCache(page) test_bit(PG_swapcache, &(page)->flags)
289 #define SetPageSwapCache(page) set_bit(PG_swapcache, &(page)->flags)
290 #define ClearPageSwapCache(page) clear_bit(PG_swapcache, &(page)->flags)
291 #else
292 #define PageSwapCache(page) 0
293 #endif
294
295 #define PageUncached(page) test_bit(PG_uncached, &(page)->flags)
296 #define SetPageUncached(page) set_bit(PG_uncached, &(page)->flags)
297 #define ClearPageUncached(page) clear_bit(PG_uncached, &(page)->flags)
298
299 struct page; /* forward declaration */
300
301 extern void cancel_dirty_page(struct page *page, unsigned int account_size);
302
303 int test_clear_page_writeback(struct page *page);
304 int test_set_page_writeback(struct page *page);
305
306 static inline void set_page_writeback(struct page *page)
307 {
308 test_set_page_writeback(page);
309 }
310
311 #endif /* PAGE_FLAGS_H */
312
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