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 enum pageflags {
  71         PG_locked,              /* Page is locked. Don't touch. */
  72         PG_error,
  73         PG_referenced,
  74         PG_uptodate,
  75         PG_dirty,
  76         PG_lru,
  77         PG_active,
  78         PG_slab,
  79         PG_owner_priv_1,        /* Owner use. If pagecache, fs may use*/
  80         PG_checked = PG_owner_priv_1, /* Used by some filesystems */
  81         PG_pinned = PG_owner_priv_1, /* Xen pinned pagetable */
  82         PG_arch_1,
  83         PG_reserved,
  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_readahead is only used for file reads; PG_reclaim is only for writes */
  91         PG_readahead = PG_reclaim, /* Reminder to do async read-ahead */
  92         PG_buddy,               /* Page is free, on buddy lists */
  93
  94 #if (BITS_PER_LONG > 32)
  95 /*
  96  * 64-bit-only flags build down from bit 31
  97  *
  98  * 32 bit  -------------------------------| FIELDS |       FLAGS         |
  99  * 64 bit  |           FIELDS             | ??????         FLAGS         |
 100  *         63                            32                              0
 101  */
 102         PG_uncached = 31,               /* Page has been mapped as uncached */
 103 #endif
 104         NR_PAGEFLAGS
 105 };
 106
 107 /*
 108  * Manipulation of page state flags
 109  */
 110 #define PageLocked(page)                \
 111                 test_bit(PG_locked, &(page)->flags)
 112 #define SetPageLocked(page)             \
 113                 set_bit(PG_locked, &(page)->flags)
 114 #define TestSetPageLocked(page)         \
 115                 test_and_set_bit(PG_locked, &(page)->flags)
 116 #define ClearPageLocked(page)           \
 117                 clear_bit(PG_locked, &(page)->flags)
 118 #define TestClearPageLocked(page)       \
 119                 test_and_clear_bit(PG_locked, &(page)->flags)
 120
 121 #define PageError(page)         test_bit(PG_error, &(page)->flags)
 122 #define SetPageError(page)      set_bit(PG_error, &(page)->flags)
 123 #define ClearPageError(page)    clear_bit(PG_error, &(page)->flags)
 124
 125 #define PageReferenced(page)    test_bit(PG_referenced, &(page)->flags)
 126 #define SetPageReferenced(page) set_bit(PG_referenced, &(page)->flags)
 127 #define ClearPageReferenced(page)       clear_bit(PG_referenced, &(page)->flags)
 128 #define TestClearPageReferenced(page) test_and_clear_bit(PG_referenced, &(page)->flags)
 129
 130 static inline int PageUptodate(struct page *page)
 131 {
 132         int ret = test_bit(PG_uptodate, &(page)->flags);
 133
 134         /*
 135          * Must ensure that the data we read out of the page is loaded
 136          * _after_ we've loaded page->flags to check for PageUptodate.
 137          * We can skip the barrier if the page is not uptodate, because
 138          * we wouldn't be reading anything from it.
 139          *
 140          * See SetPageUptodate() for the other side of the story.
 141          */
 142         if (ret)
 143                 smp_rmb();
 144
 145         return ret;
 146 }
 147
 148 static inline void __SetPageUptodate(struct page *page)
 149 {
 150         smp_wmb();
 151         __set_bit(PG_uptodate, &(page)->flags);
 152 #ifdef CONFIG_S390
 153         page_clear_dirty(page);
 154 #endif
 155 }
 156
 157 static inline void SetPageUptodate(struct page *page)
 158 {
 159 #ifdef CONFIG_S390
 160         if (!test_and_set_bit(PG_uptodate, &page->flags))
 161                 page_clear_dirty(page);
 162 #else
 163         /*
 164          * Memory barrier must be issued before setting the PG_uptodate bit,
 165          * so that all previous stores issued in order to bring the page
 166          * uptodate are actually visible before PageUptodate becomes true.
 167          *
 168          * s390 doesn't need an explicit smp_wmb here because the test and
 169          * set bit already provides full barriers.
 170          */
 171         smp_wmb();
 172         set_bit(PG_uptodate, &(page)->flags);
 173 #endif
 174 }
 175
 176 #define ClearPageUptodate(page) clear_bit(PG_uptodate, &(page)->flags)
 177
 178 #define PageDirty(page)         test_bit(PG_dirty, &(page)->flags)
 179 #define SetPageDirty(page)      set_bit(PG_dirty, &(page)->flags)
 180 #define TestSetPageDirty(page)  test_and_set_bit(PG_dirty, &(page)->flags)
 181 #define ClearPageDirty(page)    clear_bit(PG_dirty, &(page)->flags)
 182 #define __ClearPageDirty(page)  __clear_bit(PG_dirty, &(page)->flags)
 183 #define TestClearPageDirty(page) test_and_clear_bit(PG_dirty, &(page)->flags)
 184
 185 #define PageLRU(page)           test_bit(PG_lru, &(page)->flags)
 186 #define SetPageLRU(page)        set_bit(PG_lru, &(page)->flags)
 187 #define ClearPageLRU(page)      clear_bit(PG_lru, &(page)->flags)
 188 #define __ClearPageLRU(page)    __clear_bit(PG_lru, &(page)->flags)
 189
 190 #define PageActive(page)        test_bit(PG_active, &(page)->flags)
 191 #define SetPageActive(page)     set_bit(PG_active, &(page)->flags)
 192 #define ClearPageActive(page)   clear_bit(PG_active, &(page)->flags)
 193 #define __ClearPageActive(page) __clear_bit(PG_active, &(page)->flags)
 194
 195 #define PageSlab(page)          test_bit(PG_slab, &(page)->flags)
 196 #define __SetPageSlab(page)     __set_bit(PG_slab, &(page)->flags)
 197 #define __ClearPageSlab(page)   __clear_bit(PG_slab, &(page)->flags)
 198
 199 #ifdef CONFIG_HIGHMEM
 200 #define PageHighMem(page)       is_highmem(page_zone(page))
 201 #else
 202 #define PageHighMem(page)       0 /* needed to optimize away at compile time */
 203 #endif
 204
 205 #define PageChecked(page)       test_bit(PG_checked, &(page)->flags)
 206 #define SetPageChecked(page)    set_bit(PG_checked, &(page)->flags)
 207 #define ClearPageChecked(page)  clear_bit(PG_checked, &(page)->flags)
 208
 209 #define PagePinned(page)        test_bit(PG_pinned, &(page)->flags)
 210 #define SetPagePinned(page)     set_bit(PG_pinned, &(page)->flags)
 211 #define ClearPagePinned(page)   clear_bit(PG_pinned, &(page)->flags)
 212
 213 #define PageReserved(page)      test_bit(PG_reserved, &(page)->flags)
 214 #define SetPageReserved(page)   set_bit(PG_reserved, &(page)->flags)
 215 #define ClearPageReserved(page) clear_bit(PG_reserved, &(page)->flags)
 216 #define __ClearPageReserved(page)       __clear_bit(PG_reserved, &(page)->flags)
 217
 218 #define SetPagePrivate(page)    set_bit(PG_private, &(page)->flags)
 219 #define ClearPagePrivate(page)  clear_bit(PG_private, &(page)->flags)
 220 #define PagePrivate(page)       test_bit(PG_private, &(page)->flags)
 221 #define __SetPagePrivate(page)  __set_bit(PG_private, &(page)->flags)
 222 #define __ClearPagePrivate(page) __clear_bit(PG_private, &(page)->flags)
 223
 224 /*
 225  * Only test-and-set exist for PG_writeback.  The unconditional operators are
 226  * risky: they bypass page accounting.
 227  */
 228 #define PageWriteback(page)     test_bit(PG_writeback, &(page)->flags)
 229 #define TestSetPageWriteback(page) test_and_set_bit(PG_writeback,       \
 230                                                         &(page)->flags)
 231 #define TestClearPageWriteback(page) test_and_clear_bit(PG_writeback,   \
 232                                                         &(page)->flags)
 233
 234 #define PageBuddy(page)         test_bit(PG_buddy, &(page)->flags)
 235 #define __SetPageBuddy(page)    __set_bit(PG_buddy, &(page)->flags)
 236 #define __ClearPageBuddy(page)  __clear_bit(PG_buddy, &(page)->flags)
 237
 238 #define PageMappedToDisk(page)  test_bit(PG_mappedtodisk, &(page)->flags)
 239 #define SetPageMappedToDisk(page) set_bit(PG_mappedtodisk, &(page)->flags)
 240 #define ClearPageMappedToDisk(page) clear_bit(PG_mappedtodisk, &(page)->flags)
 241
 242 #define PageReadahead(page)     test_bit(PG_readahead, &(page)->flags)
 243 #define SetPageReadahead(page)  set_bit(PG_readahead, &(page)->flags)
 244 #define ClearPageReadahead(page) clear_bit(PG_readahead, &(page)->flags)
 245
 246 #define PageReclaim(page)       test_bit(PG_reclaim, &(page)->flags)
 247 #define SetPageReclaim(page)    set_bit(PG_reclaim, &(page)->flags)
 248 #define ClearPageReclaim(page)  clear_bit(PG_reclaim, &(page)->flags)
 249 #define TestClearPageReclaim(page) test_and_clear_bit(PG_reclaim, &(page)->flags)
 250
 251 #define PageCompound(page)      test_bit(PG_compound, &(page)->flags)
 252 #define __SetPageCompound(page) __set_bit(PG_compound, &(page)->flags)
 253 #define __ClearPageCompound(page) __clear_bit(PG_compound, &(page)->flags)
 254
 255 /*
 256  * PG_reclaim is used in combination with PG_compound to mark the
 257  * head and tail of a compound page
 258  *
 259  * PG_compound & PG_reclaim     => Tail page
 260  * PG_compound & ~PG_reclaim    => Head page
 261  */
 262
 263 #define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))
 264
 265 #define PageTail(page)  (((page)->flags & PG_head_tail_mask)    \
 266                                 == PG_head_tail_mask)
 267
 268 static inline void __SetPageTail(struct page *page)
 269 {
 270         page->flags |= PG_head_tail_mask;
 271 }
 272
 273 static inline void __ClearPageTail(struct page *page)
 274 {
 275         page->flags &= ~PG_head_tail_mask;
 276 }
 277
 278 #define PageHead(page)  (((page)->flags & PG_head_tail_mask)    \
 279                                 == (1L << PG_compound))
 280 #define __SetPageHead(page)     __SetPageCompound(page)
 281 #define __ClearPageHead(page)   __ClearPageCompound(page)
 282
 283 #ifdef CONFIG_SWAP
 284 #define PageSwapCache(page)     test_bit(PG_swapcache, &(page)->flags)
 285 #define SetPageSwapCache(page)  set_bit(PG_swapcache, &(page)->flags)
 286 #define ClearPageSwapCache(page) clear_bit(PG_swapcache, &(page)->flags)
 287 #else
 288 #define PageSwapCache(page)     0
 289 #endif
 290
 291 #define PageUncached(page)      test_bit(PG_uncached, &(page)->flags)
 292 #define SetPageUncached(page)   set_bit(PG_uncached, &(page)->flags)
 293 #define ClearPageUncached(page) clear_bit(PG_uncached, &(page)->flags)
 294
 295 struct page;    /* forward declaration */
 296
 297 extern void cancel_dirty_page(struct page *page, unsigned int account_size);
 298
 299 int test_clear_page_writeback(struct page *page);
 300 int test_set_page_writeback(struct page *page);
 301
 302 static inline void set_page_writeback(struct page *page)
 303 {
 304         test_set_page_writeback(page);
 305 }
 306
 307 #endif  /* PAGE_FLAGS_H */