mm: optimize compound_head() by avoiding a shared page flag
[sfrench/cifs-2.6.git] / include / linux / page-flags.h
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_nosave               13      /* Used for system suspend/resume */
87 #define PG_compound             14      /* Part of a compound page */
88 #define PG_swapcache            15      /* Swap page: swp_entry_t in private */
89
90 #define PG_mappedtodisk         16      /* Has blocks allocated on-disk */
91 #define PG_reclaim              17      /* To be reclaimed asap */
92 #define PG_nosave_free          18      /* Used for system suspend/resume */
93 #define PG_buddy                19      /* Page is free, on buddy lists */
94
95 /* PG_owner_priv_1 users should have descriptive aliases */
96 #define PG_checked              PG_owner_priv_1 /* Used by some filesystems */
97
98 #if (BITS_PER_LONG > 32)
99 /*
100  * 64-bit-only flags build down from bit 31
101  *
102  * 32 bit  -------------------------------| FIELDS |       FLAGS         |
103  * 64 bit  |           FIELDS             | ??????         FLAGS         |
104  *         63                            32                              0
105  */
106 #define PG_uncached             31      /* Page has been mapped as uncached */
107 #endif
108
109 /*
110  * Manipulation of page state flags
111  */
112 #define PageLocked(page)                \
113                 test_bit(PG_locked, &(page)->flags)
114 #define SetPageLocked(page)             \
115                 set_bit(PG_locked, &(page)->flags)
116 #define TestSetPageLocked(page)         \
117                 test_and_set_bit(PG_locked, &(page)->flags)
118 #define ClearPageLocked(page)           \
119                 clear_bit(PG_locked, &(page)->flags)
120 #define TestClearPageLocked(page)       \
121                 test_and_clear_bit(PG_locked, &(page)->flags)
122
123 #define PageError(page)         test_bit(PG_error, &(page)->flags)
124 #define SetPageError(page)      set_bit(PG_error, &(page)->flags)
125 #define ClearPageError(page)    clear_bit(PG_error, &(page)->flags)
126
127 #define PageReferenced(page)    test_bit(PG_referenced, &(page)->flags)
128 #define SetPageReferenced(page) set_bit(PG_referenced, &(page)->flags)
129 #define ClearPageReferenced(page)       clear_bit(PG_referenced, &(page)->flags)
130 #define TestClearPageReferenced(page) test_and_clear_bit(PG_referenced, &(page)->flags)
131
132 #define PageUptodate(page)      test_bit(PG_uptodate, &(page)->flags)
133 #ifdef CONFIG_S390
134 static inline void SetPageUptodate(struct page *page)
135 {
136         if (!test_and_set_bit(PG_uptodate, &page->flags))
137                 page_clear_dirty(page);
138 }
139 #else
140 #define SetPageUptodate(page)   set_bit(PG_uptodate, &(page)->flags)
141 #endif
142 #define ClearPageUptodate(page) clear_bit(PG_uptodate, &(page)->flags)
143
144 #define PageDirty(page)         test_bit(PG_dirty, &(page)->flags)
145 #define SetPageDirty(page)      set_bit(PG_dirty, &(page)->flags)
146 #define TestSetPageDirty(page)  test_and_set_bit(PG_dirty, &(page)->flags)
147 #define ClearPageDirty(page)    clear_bit(PG_dirty, &(page)->flags)
148 #define __ClearPageDirty(page)  __clear_bit(PG_dirty, &(page)->flags)
149 #define TestClearPageDirty(page) test_and_clear_bit(PG_dirty, &(page)->flags)
150
151 #define PageLRU(page)           test_bit(PG_lru, &(page)->flags)
152 #define SetPageLRU(page)        set_bit(PG_lru, &(page)->flags)
153 #define ClearPageLRU(page)      clear_bit(PG_lru, &(page)->flags)
154 #define __ClearPageLRU(page)    __clear_bit(PG_lru, &(page)->flags)
155
156 #define PageActive(page)        test_bit(PG_active, &(page)->flags)
157 #define SetPageActive(page)     set_bit(PG_active, &(page)->flags)
158 #define ClearPageActive(page)   clear_bit(PG_active, &(page)->flags)
159 #define __ClearPageActive(page) __clear_bit(PG_active, &(page)->flags)
160
161 #define PageSlab(page)          test_bit(PG_slab, &(page)->flags)
162 #define __SetPageSlab(page)     __set_bit(PG_slab, &(page)->flags)
163 #define __ClearPageSlab(page)   __clear_bit(PG_slab, &(page)->flags)
164
165 #ifdef CONFIG_HIGHMEM
166 #define PageHighMem(page)       is_highmem(page_zone(page))
167 #else
168 #define PageHighMem(page)       0 /* needed to optimize away at compile time */
169 #endif
170
171 #define PageChecked(page)       test_bit(PG_checked, &(page)->flags)
172 #define SetPageChecked(page)    set_bit(PG_checked, &(page)->flags)
173 #define ClearPageChecked(page)  clear_bit(PG_checked, &(page)->flags)
174
175 #define PageReserved(page)      test_bit(PG_reserved, &(page)->flags)
176 #define SetPageReserved(page)   set_bit(PG_reserved, &(page)->flags)
177 #define ClearPageReserved(page) clear_bit(PG_reserved, &(page)->flags)
178 #define __ClearPageReserved(page)       __clear_bit(PG_reserved, &(page)->flags)
179
180 #define SetPagePrivate(page)    set_bit(PG_private, &(page)->flags)
181 #define ClearPagePrivate(page)  clear_bit(PG_private, &(page)->flags)
182 #define PagePrivate(page)       test_bit(PG_private, &(page)->flags)
183 #define __SetPagePrivate(page)  __set_bit(PG_private, &(page)->flags)
184 #define __ClearPagePrivate(page) __clear_bit(PG_private, &(page)->flags)
185
186 #define PageWriteback(page)     test_bit(PG_writeback, &(page)->flags)
187 #define SetPageWriteback(page)                                          \
188         do {                                                            \
189                 if (!test_and_set_bit(PG_writeback,                     \
190                                 &(page)->flags))                        \
191                         inc_zone_page_state(page, NR_WRITEBACK);        \
192         } while (0)
193 #define TestSetPageWriteback(page)                                      \
194         ({                                                              \
195                 int ret;                                                \
196                 ret = test_and_set_bit(PG_writeback,                    \
197                                         &(page)->flags);                \
198                 if (!ret)                                               \
199                         inc_zone_page_state(page, NR_WRITEBACK);        \
200                 ret;                                                    \
201         })
202 #define ClearPageWriteback(page)                                        \
203         do {                                                            \
204                 if (test_and_clear_bit(PG_writeback,                    \
205                                 &(page)->flags))                        \
206                         dec_zone_page_state(page, NR_WRITEBACK);        \
207         } while (0)
208 #define TestClearPageWriteback(page)                                    \
209         ({                                                              \
210                 int ret;                                                \
211                 ret = test_and_clear_bit(PG_writeback,                  \
212                                 &(page)->flags);                        \
213                 if (ret)                                                \
214                         dec_zone_page_state(page, NR_WRITEBACK);        \
215                 ret;                                                    \
216         })
217
218 #define PageNosave(page)        test_bit(PG_nosave, &(page)->flags)
219 #define SetPageNosave(page)     set_bit(PG_nosave, &(page)->flags)
220 #define TestSetPageNosave(page) test_and_set_bit(PG_nosave, &(page)->flags)
221 #define ClearPageNosave(page)           clear_bit(PG_nosave, &(page)->flags)
222 #define TestClearPageNosave(page)       test_and_clear_bit(PG_nosave, &(page)->flags)
223
224 #define PageNosaveFree(page)    test_bit(PG_nosave_free, &(page)->flags)
225 #define SetPageNosaveFree(page) set_bit(PG_nosave_free, &(page)->flags)
226 #define ClearPageNosaveFree(page)               clear_bit(PG_nosave_free, &(page)->flags)
227
228 #define PageBuddy(page)         test_bit(PG_buddy, &(page)->flags)
229 #define __SetPageBuddy(page)    __set_bit(PG_buddy, &(page)->flags)
230 #define __ClearPageBuddy(page)  __clear_bit(PG_buddy, &(page)->flags)
231
232 #define PageMappedToDisk(page)  test_bit(PG_mappedtodisk, &(page)->flags)
233 #define SetPageMappedToDisk(page) set_bit(PG_mappedtodisk, &(page)->flags)
234 #define ClearPageMappedToDisk(page) clear_bit(PG_mappedtodisk, &(page)->flags)
235
236 #define PageReclaim(page)       test_bit(PG_reclaim, &(page)->flags)
237 #define SetPageReclaim(page)    set_bit(PG_reclaim, &(page)->flags)
238 #define ClearPageReclaim(page)  clear_bit(PG_reclaim, &(page)->flags)
239 #define TestClearPageReclaim(page) test_and_clear_bit(PG_reclaim, &(page)->flags)
240
241 #define PageCompound(page)      test_bit(PG_compound, &(page)->flags)
242 #define __SetPageCompound(page) __set_bit(PG_compound, &(page)->flags)
243 #define __ClearPageCompound(page) __clear_bit(PG_compound, &(page)->flags)
244
245 /*
246  * PG_reclaim is used in combination with PG_compound to mark the
247  * head and tail of a compound page
248  *
249  * PG_compound & PG_reclaim     => Tail page
250  * PG_compound & ~PG_reclaim    => Head page
251  */
252
253 #define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))
254
255 #define PageTail(page)  ((page->flags & PG_head_tail_mask) \
256                                 == PG_head_tail_mask)
257
258 static inline void __SetPageTail(struct page *page)
259 {
260         page->flags |= PG_head_tail_mask;
261 }
262
263 static inline void __ClearPageTail(struct page *page)
264 {
265         page->flags &= ~PG_head_tail_mask;
266 }
267
268 #define PageHead(page)  ((page->flags & PG_head_tail_mask) \
269                                 == (1L << PG_compound))
270 #define __SetPageHead(page)     __SetPageCompound(page)
271 #define __ClearPageHead(page)   __ClearPageCompound(page)
272
273 #ifdef CONFIG_SWAP
274 #define PageSwapCache(page)     test_bit(PG_swapcache, &(page)->flags)
275 #define SetPageSwapCache(page)  set_bit(PG_swapcache, &(page)->flags)
276 #define ClearPageSwapCache(page) clear_bit(PG_swapcache, &(page)->flags)
277 #else
278 #define PageSwapCache(page)     0
279 #endif
280
281 #define PageUncached(page)      test_bit(PG_uncached, &(page)->flags)
282 #define SetPageUncached(page)   set_bit(PG_uncached, &(page)->flags)
283 #define ClearPageUncached(page) clear_bit(PG_uncached, &(page)->flags)
284
285 struct page;    /* forward declaration */
286
287 extern void cancel_dirty_page(struct page *page, unsigned int account_size);
288
289 int test_clear_page_writeback(struct page *page);
290 int test_set_page_writeback(struct page *page);
291
292 static inline void set_page_writeback(struct page *page)
293 {
294         test_set_page_writeback(page);
295 }
296
297 #endif  /* PAGE_FLAGS_H */