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