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 #ifndef __GENERATING_BOUNDS_H
  10 #include <linux/mm_types.h>
  11 #include <linux/bounds.h>
  12 #endif /* !__GENERATING_BOUNDS_H */
  13
  14 /*
  15  * Various page->flags bits:
  16  *
  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)...
  19  *
  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.
  23  *
  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.
  27  *
  28  * PG_locked also pins a page in pagecache, and blocks truncation of the file
  29  * while it is held.
  30  *
  31  * page_waitqueue(page) is a wait queue of all tasks waiting for the page
  32  * to become unlocked.
  33  *
  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.
  36  *
  37  * PG_referenced, PG_reclaim are used for page reclaim for anonymous and
  38  * file-backed pagecache (see mm/vmscan.c).
  39  *
  40  * PG_error is set to indicate that an I/O error occurred on this page.
  41  *
  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
  44  * the page cache.
  45  *
  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
  49  * address space...
  50  *
  51  * PG_buddy is set to indicate that the page is free and in the buddy system
  52  * (see mm/page_alloc.c).
  53  *
  54  */
  55
  56 /*
  57  * Don't use the *_dontuse flags.  Use the macros.  Otherwise you'll break
  58  * locked- and dirty-page accounting.
  59  *
  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.
  63  *
  64  *  | FIELD | ... | FLAGS |
  65  *  N-1           ^       0
  66  *               (NR_PAGEFLAGS)
  67  *
  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).
  71  */
  72 enum pageflags {
  73         PG_locked,              /* Page is locked. Don't touch. */
  74         PG_error,
  75         PG_referenced,
  76         PG_uptodate,
  77         PG_dirty,
  78         PG_lru,
  79         PG_active,
  80         PG_slab,
  81         PG_owner_priv_1,        /* Owner use. If pagecache, fs may use*/
  82         PG_arch_1,
  83         PG_reserved,
  84         PG_private,             /* If pagecache, has fs-private data */
  85         PG_writeback,           /* Page is under writeback */
  86 #ifdef CONFIG_PAGEFLAGS_EXTENDED
  87         PG_head,                /* A head page */
  88         PG_tail,                /* A tail page */
  89 #else
  90         PG_compound,            /* A compound page */
  91 #endif
  92         PG_swapcache,           /* Swap page: swp_entry_t in private */
  93         PG_mappedtodisk,        /* Has blocks allocated on-disk */
  94         PG_reclaim,             /* To be reclaimed asap */
  95         PG_buddy,               /* Page is free, on buddy lists */
  96         PG_swapbacked,          /* Page is backed by RAM/swap */
  97 #ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
  98         PG_uncached,            /* Page has been mapped as uncached */
  99 #endif
 100         __NR_PAGEFLAGS,
 101
 102         /* Filesystems */
 103         PG_checked = PG_owner_priv_1,
 104
 105         /* XEN */
 106         PG_pinned = PG_owner_priv_1,
 107         PG_savepinned = PG_dirty,
 108
 109         /* SLOB */
 110         PG_slob_page = PG_active,
 111         PG_slob_free = PG_private,
 112
 113         /* SLUB */
 114         PG_slub_frozen = PG_active,
 115         PG_slub_debug = PG_error,
 116 };
 117
 118 #ifndef __GENERATING_BOUNDS_H
 119
 120 /*
 121  * Macros to create function definitions for page flags
 122  */
 123 #define TESTPAGEFLAG(uname, lname)                                      \
 124 static inline int Page##uname(struct page *page)                        \
 125                         { return test_bit(PG_##lname, &page->flags); }
 126
 127 #define SETPAGEFLAG(uname, lname)                                       \
 128 static inline void SetPage##uname(struct page *page)                    \
 129                         { set_bit(PG_##lname, &page->flags); }
 130
 131 #define CLEARPAGEFLAG(uname, lname)                                     \
 132 static inline void ClearPage##uname(struct page *page)                  \
 133                         { clear_bit(PG_##lname, &page->flags); }
 134
 135 #define __SETPAGEFLAG(uname, lname)                                     \
 136 static inline void __SetPage##uname(struct page *page)                  \
 137                         { __set_bit(PG_##lname, &page->flags); }
 138
 139 #define __CLEARPAGEFLAG(uname, lname)                                   \
 140 static inline void __ClearPage##uname(struct page *page)                \
 141                         { __clear_bit(PG_##lname, &page->flags); }
 142
 143 #define TESTSETFLAG(uname, lname)                                       \
 144 static inline int TestSetPage##uname(struct page *page)                 \
 145                 { return test_and_set_bit(PG_##lname, &page->flags); }
 146
 147 #define TESTCLEARFLAG(uname, lname)                                     \
 148 static inline int TestClearPage##uname(struct page *page)               \
 149                 { return test_and_clear_bit(PG_##lname, &page->flags); }
 150
 151
 152 #define PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)               \
 153         SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname)
 154
 155 #define __PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)             \
 156         __SETPAGEFLAG(uname, lname)  __CLEARPAGEFLAG(uname, lname)
 157
 158 #define PAGEFLAG_FALSE(uname)                                           \
 159 static inline int Page##uname(struct page *page)                        \
 160                         { return 0; }
 161
 162 #define TESTSCFLAG(uname, lname)                                        \
 163         TESTSETFLAG(uname, lname) TESTCLEARFLAG(uname, lname)
 164
 165 struct page;    /* forward declaration */
 166
 167 TESTPAGEFLAG(Locked, locked)
 168 PAGEFLAG(Error, error)
 169 PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced)
 170 PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty, dirty)
 171 PAGEFLAG(LRU, lru) __CLEARPAGEFLAG(LRU, lru)
 172 PAGEFLAG(Active, active) __CLEARPAGEFLAG(Active, active)
 173 __PAGEFLAG(Slab, slab)
 174 PAGEFLAG(Checked, checked)              /* Used by some filesystems */
 175 PAGEFLAG(Pinned, pinned) TESTSCFLAG(Pinned, pinned)     /* Xen */
 176 PAGEFLAG(SavePinned, savepinned);                       /* Xen */
 177 PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
 178 PAGEFLAG(Private, private) __CLEARPAGEFLAG(Private, private)
 179         __SETPAGEFLAG(Private, private)
 180 PAGEFLAG(SwapBacked, swapbacked) __CLEARPAGEFLAG(SwapBacked, swapbacked)
 181
 182 __PAGEFLAG(SlobPage, slob_page)
 183 __PAGEFLAG(SlobFree, slob_free)
 184
 185 __PAGEFLAG(SlubFrozen, slub_frozen)
 186 __PAGEFLAG(SlubDebug, slub_debug)
 187
 188 /*
 189  * Only test-and-set exist for PG_writeback.  The unconditional operators are
 190  * risky: they bypass page accounting.
 191  */
 192 TESTPAGEFLAG(Writeback, writeback) TESTSCFLAG(Writeback, writeback)
 193 __PAGEFLAG(Buddy, buddy)
 194 PAGEFLAG(MappedToDisk, mappedtodisk)
 195
 196 /* PG_readahead is only used for file reads; PG_reclaim is only for writes */
 197 PAGEFLAG(Reclaim, reclaim) TESTCLEARFLAG(Reclaim, reclaim)
 198 PAGEFLAG(Readahead, reclaim)            /* Reminder to do async read-ahead */
 199
 200 #ifdef CONFIG_HIGHMEM
 201 /*
 202  * Must use a macro here due to header dependency issues. page_zone() is not
 203  * available at this point.
 204  */
 205 #define PageHighMem(__p) is_highmem(page_zone(__p))
 206 #else
 207 PAGEFLAG_FALSE(HighMem)
 208 #endif
 209
 210 #ifdef CONFIG_SWAP
 211 PAGEFLAG(SwapCache, swapcache)
 212 #else
 213 PAGEFLAG_FALSE(SwapCache)
 214 #endif
 215
 216 #ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
 217 PAGEFLAG(Uncached, uncached)
 218 #else
 219 PAGEFLAG_FALSE(Uncached)
 220 #endif
 221
 222 static inline int PageUptodate(struct page *page)
 223 {
 224         int ret = test_bit(PG_uptodate, &(page)->flags);
 225
 226         /*
 227          * Must ensure that the data we read out of the page is loaded
 228          * _after_ we've loaded page->flags to check for PageUptodate.
 229          * We can skip the barrier if the page is not uptodate, because
 230          * we wouldn't be reading anything from it.
 231          *
 232          * See SetPageUptodate() for the other side of the story.
 233          */
 234         if (ret)
 235                 smp_rmb();
 236
 237         return ret;
 238 }
 239
 240 static inline void __SetPageUptodate(struct page *page)
 241 {
 242         smp_wmb();
 243         __set_bit(PG_uptodate, &(page)->flags);
 244 }
 245
 246 static inline void SetPageUptodate(struct page *page)
 247 {
 248 #ifdef CONFIG_S390
 249         if (!test_and_set_bit(PG_uptodate, &page->flags))
 250                 page_clear_dirty(page);
 251 #else
 252         /*
 253          * Memory barrier must be issued before setting the PG_uptodate bit,
 254          * so that all previous stores issued in order to bring the page
 255          * uptodate are actually visible before PageUptodate becomes true.
 256          *
 257          * s390 doesn't need an explicit smp_wmb here because the test and
 258          * set bit already provides full barriers.
 259          */
 260         smp_wmb();
 261         set_bit(PG_uptodate, &(page)->flags);
 262 #endif
 263 }
 264
 265 CLEARPAGEFLAG(Uptodate, uptodate)
 266
 267 extern void cancel_dirty_page(struct page *page, unsigned int account_size);
 268
 269 int test_clear_page_writeback(struct page *page);
 270 int test_set_page_writeback(struct page *page);
 271
 272 static inline void set_page_writeback(struct page *page)
 273 {
 274         test_set_page_writeback(page);
 275 }
 276
 277 #ifdef CONFIG_PAGEFLAGS_EXTENDED
 278 /*
 279  * System with lots of page flags available. This allows separate
 280  * flags for PageHead() and PageTail() checks of compound pages so that bit
 281  * tests can be used in performance sensitive paths. PageCompound is
 282  * generally not used in hot code paths.
 283  */
 284 __PAGEFLAG(Head, head)
 285 __PAGEFLAG(Tail, tail)
 286
 287 static inline int PageCompound(struct page *page)
 288 {
 289         return page->flags & ((1L << PG_head) | (1L << PG_tail));
 290
 291 }
 292 #else
 293 /*
 294  * Reduce page flag use as much as possible by overlapping
 295  * compound page flags with the flags used for page cache pages. Possible
 296  * because PageCompound is always set for compound pages and not for
 297  * pages on the LRU and/or pagecache.
 298  */
 299 TESTPAGEFLAG(Compound, compound)
 300 __PAGEFLAG(Head, compound)
 301
 302 /*
 303  * PG_reclaim is used in combination with PG_compound to mark the
 304  * head and tail of a compound page. This saves one page flag
 305  * but makes it impossible to use compound pages for the page cache.
 306  * The PG_reclaim bit would have to be used for reclaim or readahead
 307  * if compound pages enter the page cache.
 308  *
 309  * PG_compound & PG_reclaim     => Tail page
 310  * PG_compound & ~PG_reclaim    => Head page
 311  */
 312 #define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))
 313
 314 static inline int PageTail(struct page *page)
 315 {
 316         return ((page->flags & PG_head_tail_mask) == PG_head_tail_mask);
 317 }
 318
 319 static inline void __SetPageTail(struct page *page)
 320 {
 321         page->flags |= PG_head_tail_mask;
 322 }
 323
 324 static inline void __ClearPageTail(struct page *page)
 325 {
 326         page->flags &= ~PG_head_tail_mask;
 327 }
 328
 329 #endif /* !PAGEFLAGS_EXTENDED */
 330
 331 #define PAGE_FLAGS      (1 << PG_lru   | 1 << PG_private   | 1 << PG_locked | \
 332                          1 << PG_buddy | 1 << PG_writeback | \
 333                          1 << PG_slab  | 1 << PG_swapcache | 1 << PG_active)
 334
 335 /*
 336  * Flags checked in bad_page().  Pages on the free list should not have
 337  * these flags set.  It they are, there is a problem.
 338  */
 339 #define PAGE_FLAGS_CLEAR_WHEN_BAD (PAGE_FLAGS | \
 340                 1 << PG_reclaim | 1 << PG_dirty | 1 << PG_swapbacked)
 341
 342 /*
 343  * Flags checked when a page is freed.  Pages being freed should not have
 344  * these flags set.  It they are, there is a problem.
 345  */
 346 #define PAGE_FLAGS_CHECK_AT_FREE (PAGE_FLAGS | 1 << PG_reserved)
 347
 348 /*
 349  * Flags checked when a page is prepped for return by the page allocator.
 350  * Pages being prepped should not have these flags set.  It they are, there
 351  * is a problem.
 352  */
 353 #define PAGE_FLAGS_CHECK_AT_PREP (PAGE_FLAGS | \
 354                 1 << PG_reserved | 1 << PG_dirty | 1 << PG_swapbacked)
 355
 356 #endif /* !__GENERATING_BOUNDS_H */
 357 #endif  /* PAGE_FLAGS_H */