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_private_2,           /* If pagecache, has fs aux data */
  86         PG_writeback,           /* Page is under writeback */
  87 #ifdef CONFIG_PAGEFLAGS_EXTENDED
  88         PG_head,                /* A head page */
  89         PG_tail,                /* A tail page */
  90 #else
  91         PG_compound,            /* A compound page */
  92 #endif
  93         PG_swapcache,           /* Swap page: swp_entry_t in private */
  94         PG_mappedtodisk,        /* Has blocks allocated on-disk */
  95         PG_reclaim,             /* To be reclaimed asap */
  96         PG_buddy,               /* Page is free, on buddy lists */
  97         PG_swapbacked,          /* Page is backed by RAM/swap */
  98 #ifdef CONFIG_UNEVICTABLE_LRU
  99         PG_unevictable,         /* Page is "unevictable"  */
 100 #endif
 101 #ifdef CONFIG_HAVE_MLOCKED_PAGE_BIT
 102         PG_mlocked,             /* Page is vma mlocked */
 103 #endif
 104 #ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
 105         PG_uncached,            /* Page has been mapped as uncached */
 106 #endif
 107         __NR_PAGEFLAGS,
 108
 109         /* Filesystems */
 110         PG_checked = PG_owner_priv_1,
 111
 112         /* Two page bits are conscripted by FS-Cache to maintain local caching
 113          * state.  These bits are set on pages belonging to the netfs's inodes
 114          * when those inodes are being locally cached.
 115          */
 116         PG_fscache = PG_private_2,      /* page backed by cache */
 117
 118         /* XEN */
 119         PG_pinned = PG_owner_priv_1,
 120         PG_savepinned = PG_dirty,
 121
 122         /* SLOB */
 123         PG_slob_free = PG_private,
 124
 125         /* SLUB */
 126         PG_slub_frozen = PG_active,
 127         PG_slub_debug = PG_error,
 128 };
 129
 130 #ifndef __GENERATING_BOUNDS_H
 131
 132 /*
 133  * Macros to create function definitions for page flags
 134  */
 135 #define TESTPAGEFLAG(uname, lname)                                      \
 136 static inline int Page##uname(struct page *page)                        \
 137                         { return test_bit(PG_##lname, &page->flags); }
 138
 139 #define SETPAGEFLAG(uname, lname)                                       \
 140 static inline void SetPage##uname(struct page *page)                    \
 141                         { set_bit(PG_##lname, &page->flags); }
 142
 143 #define CLEARPAGEFLAG(uname, lname)                                     \
 144 static inline void ClearPage##uname(struct page *page)                  \
 145                         { clear_bit(PG_##lname, &page->flags); }
 146
 147 #define __SETPAGEFLAG(uname, lname)                                     \
 148 static inline void __SetPage##uname(struct page *page)                  \
 149                         { __set_bit(PG_##lname, &page->flags); }
 150
 151 #define __CLEARPAGEFLAG(uname, lname)                                   \
 152 static inline void __ClearPage##uname(struct page *page)                \
 153                         { __clear_bit(PG_##lname, &page->flags); }
 154
 155 #define TESTSETFLAG(uname, lname)                                       \
 156 static inline int TestSetPage##uname(struct page *page)                 \
 157                 { return test_and_set_bit(PG_##lname, &page->flags); }
 158
 159 #define TESTCLEARFLAG(uname, lname)                                     \
 160 static inline int TestClearPage##uname(struct page *page)               \
 161                 { return test_and_clear_bit(PG_##lname, &page->flags); }
 162
 163
 164 #define PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)               \
 165         SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname)
 166
 167 #define __PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)             \
 168         __SETPAGEFLAG(uname, lname)  __CLEARPAGEFLAG(uname, lname)
 169
 170 #define PAGEFLAG_FALSE(uname)                                           \
 171 static inline int Page##uname(struct page *page)                        \
 172                         { return 0; }
 173
 174 #define TESTSCFLAG(uname, lname)                                        \
 175         TESTSETFLAG(uname, lname) TESTCLEARFLAG(uname, lname)
 176
 177 #define SETPAGEFLAG_NOOP(uname)                                         \
 178 static inline void SetPage##uname(struct page *page) {  }
 179
 180 #define CLEARPAGEFLAG_NOOP(uname)                                       \
 181 static inline void ClearPage##uname(struct page *page) {  }
 182
 183 #define __CLEARPAGEFLAG_NOOP(uname)                                     \
 184 static inline void __ClearPage##uname(struct page *page) {  }
 185
 186 #define TESTCLEARFLAG_FALSE(uname)                                      \
 187 static inline int TestClearPage##uname(struct page *page) { return 0; }
 188
 189 struct page;    /* forward declaration */
 190
 191 TESTPAGEFLAG(Locked, locked) TESTSETFLAG(Locked, locked)
 192 PAGEFLAG(Error, error)
 193 PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced)
 194 PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty, dirty)
 195 PAGEFLAG(LRU, lru) __CLEARPAGEFLAG(LRU, lru)
 196 PAGEFLAG(Active, active) __CLEARPAGEFLAG(Active, active)
 197         TESTCLEARFLAG(Active, active)
 198 __PAGEFLAG(Slab, slab)
 199 PAGEFLAG(Checked, checked)              /* Used by some filesystems */
 200 PAGEFLAG(Pinned, pinned) TESTSCFLAG(Pinned, pinned)     /* Xen */
 201 PAGEFLAG(SavePinned, savepinned);                       /* Xen */
 202 PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
 203 PAGEFLAG(SwapBacked, swapbacked) __CLEARPAGEFLAG(SwapBacked, swapbacked)
 204
 205 __PAGEFLAG(SlobFree, slob_free)
 206
 207 __PAGEFLAG(SlubFrozen, slub_frozen)
 208 __PAGEFLAG(SlubDebug, slub_debug)
 209
 210 /*
 211  * Private page markings that may be used by the filesystem that owns the page
 212  * for its own purposes.
 213  * - PG_private and PG_private_2 cause releasepage() and co to be invoked
 214  */
 215 PAGEFLAG(Private, private) __SETPAGEFLAG(Private, private)
 216         __CLEARPAGEFLAG(Private, private)
 217 PAGEFLAG(Private2, private_2) TESTSCFLAG(Private2, private_2)
 218 PAGEFLAG(OwnerPriv1, owner_priv_1) TESTCLEARFLAG(OwnerPriv1, owner_priv_1)
 219
 220 /*
 221  * Only test-and-set exist for PG_writeback.  The unconditional operators are
 222  * risky: they bypass page accounting.
 223  */
 224 TESTPAGEFLAG(Writeback, writeback) TESTSCFLAG(Writeback, writeback)
 225 __PAGEFLAG(Buddy, buddy)
 226 PAGEFLAG(MappedToDisk, mappedtodisk)
 227
 228 /* PG_readahead is only used for file reads; PG_reclaim is only for writes */
 229 PAGEFLAG(Reclaim, reclaim) TESTCLEARFLAG(Reclaim, reclaim)
 230 PAGEFLAG(Readahead, reclaim)            /* Reminder to do async read-ahead */
 231
 232 #ifdef CONFIG_HIGHMEM
 233 /*
 234  * Must use a macro here due to header dependency issues. page_zone() is not
 235  * available at this point.
 236  */
 237 #define PageHighMem(__p) is_highmem(page_zone(__p))
 238 #else
 239 PAGEFLAG_FALSE(HighMem)
 240 #endif
 241
 242 #ifdef CONFIG_SWAP
 243 PAGEFLAG(SwapCache, swapcache)
 244 #else
 245 PAGEFLAG_FALSE(SwapCache)
 246         SETPAGEFLAG_NOOP(SwapCache) CLEARPAGEFLAG_NOOP(SwapCache)
 247 #endif
 248
 249 #ifdef CONFIG_UNEVICTABLE_LRU
 250 PAGEFLAG(Unevictable, unevictable) __CLEARPAGEFLAG(Unevictable, unevictable)
 251         TESTCLEARFLAG(Unevictable, unevictable)
 252 #else
 253 PAGEFLAG_FALSE(Unevictable) TESTCLEARFLAG_FALSE(Unevictable)
 254         SETPAGEFLAG_NOOP(Unevictable) CLEARPAGEFLAG_NOOP(Unevictable)
 255         __CLEARPAGEFLAG_NOOP(Unevictable)
 256 #endif
 257
 258 #ifdef CONFIG_HAVE_MLOCKED_PAGE_BIT
 259 #define MLOCK_PAGES 1
 260 PAGEFLAG(Mlocked, mlocked) __CLEARPAGEFLAG(Mlocked, mlocked)
 261         TESTSCFLAG(Mlocked, mlocked)
 262 #else
 263 #define MLOCK_PAGES 0
 264 PAGEFLAG_FALSE(Mlocked)
 265         SETPAGEFLAG_NOOP(Mlocked) TESTCLEARFLAG_FALSE(Mlocked)
 266 #endif
 267
 268 #ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
 269 PAGEFLAG(Uncached, uncached)
 270 #else
 271 PAGEFLAG_FALSE(Uncached)
 272 #endif
 273
 274 static inline int PageUptodate(struct page *page)
 275 {
 276         int ret = test_bit(PG_uptodate, &(page)->flags);
 277
 278         /*
 279          * Must ensure that the data we read out of the page is loaded
 280          * _after_ we've loaded page->flags to check for PageUptodate.
 281          * We can skip the barrier if the page is not uptodate, because
 282          * we wouldn't be reading anything from it.
 283          *
 284          * See SetPageUptodate() for the other side of the story.
 285          */
 286         if (ret)
 287                 smp_rmb();
 288
 289         return ret;
 290 }
 291
 292 static inline void __SetPageUptodate(struct page *page)
 293 {
 294         smp_wmb();
 295         __set_bit(PG_uptodate, &(page)->flags);
 296 }
 297
 298 static inline void SetPageUptodate(struct page *page)
 299 {
 300 #ifdef CONFIG_S390
 301         if (!test_and_set_bit(PG_uptodate, &page->flags))
 302                 page_clear_dirty(page);
 303 #else
 304         /*
 305          * Memory barrier must be issued before setting the PG_uptodate bit,
 306          * so that all previous stores issued in order to bring the page
 307          * uptodate are actually visible before PageUptodate becomes true.
 308          *
 309          * s390 doesn't need an explicit smp_wmb here because the test and
 310          * set bit already provides full barriers.
 311          */
 312         smp_wmb();
 313         set_bit(PG_uptodate, &(page)->flags);
 314 #endif
 315 }
 316
 317 CLEARPAGEFLAG(Uptodate, uptodate)
 318
 319 extern void cancel_dirty_page(struct page *page, unsigned int account_size);
 320
 321 int test_clear_page_writeback(struct page *page);
 322 int test_set_page_writeback(struct page *page);
 323
 324 static inline void set_page_writeback(struct page *page)
 325 {
 326         test_set_page_writeback(page);
 327 }
 328
 329 #ifdef CONFIG_PAGEFLAGS_EXTENDED
 330 /*
 331  * System with lots of page flags available. This allows separate
 332  * flags for PageHead() and PageTail() checks of compound pages so that bit
 333  * tests can be used in performance sensitive paths. PageCompound is
 334  * generally not used in hot code paths.
 335  */
 336 __PAGEFLAG(Head, head)
 337 __PAGEFLAG(Tail, tail)
 338
 339 static inline int PageCompound(struct page *page)
 340 {
 341         return page->flags & ((1L << PG_head) | (1L << PG_tail));
 342
 343 }
 344 #else
 345 /*
 346  * Reduce page flag use as much as possible by overlapping
 347  * compound page flags with the flags used for page cache pages. Possible
 348  * because PageCompound is always set for compound pages and not for
 349  * pages on the LRU and/or pagecache.
 350  */
 351 TESTPAGEFLAG(Compound, compound)
 352 __PAGEFLAG(Head, compound)
 353
 354 /*
 355  * PG_reclaim is used in combination with PG_compound to mark the
 356  * head and tail of a compound page. This saves one page flag
 357  * but makes it impossible to use compound pages for the page cache.
 358  * The PG_reclaim bit would have to be used for reclaim or readahead
 359  * if compound pages enter the page cache.
 360  *
 361  * PG_compound & PG_reclaim     => Tail page
 362  * PG_compound & ~PG_reclaim    => Head page
 363  */
 364 #define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))
 365
 366 static inline int PageTail(struct page *page)
 367 {
 368         return ((page->flags & PG_head_tail_mask) == PG_head_tail_mask);
 369 }
 370
 371 static inline void __SetPageTail(struct page *page)
 372 {
 373         page->flags |= PG_head_tail_mask;
 374 }
 375
 376 static inline void __ClearPageTail(struct page *page)
 377 {
 378         page->flags &= ~PG_head_tail_mask;
 379 }
 380
 381 #endif /* !PAGEFLAGS_EXTENDED */
 382
 383 #ifdef CONFIG_UNEVICTABLE_LRU
 384 #define __PG_UNEVICTABLE        (1 << PG_unevictable)
 385 #else
 386 #define __PG_UNEVICTABLE        0
 387 #endif
 388
 389 #ifdef CONFIG_HAVE_MLOCKED_PAGE_BIT
 390 #define __PG_MLOCKED            (1 << PG_mlocked)
 391 #else
 392 #define __PG_MLOCKED            0
 393 #endif
 394
 395 /*
 396  * Flags checked when a page is freed.  Pages being freed should not have
 397  * these flags set.  It they are, there is a problem.
 398  */
 399 #define PAGE_FLAGS_CHECK_AT_FREE \
 400         (1 << PG_lru     | 1 << PG_locked    | \
 401          1 << PG_private | 1 << PG_private_2 | \
 402          1 << PG_buddy   | 1 << PG_writeback | 1 << PG_reserved | \
 403          1 << PG_slab    | 1 << PG_swapcache | 1 << PG_active | \
 404          __PG_UNEVICTABLE | __PG_MLOCKED)
 405
 406 /*
 407  * Flags checked when a page is prepped for return by the page allocator.
 408  * Pages being prepped should not have any flags set.  It they are set,
 409  * there has been a kernel bug or struct page corruption.
 410  */
 411 #define PAGE_FLAGS_CHECK_AT_PREP        ((1 << NR_PAGEFLAGS) - 1)
 412
 413 #endif /* !__GENERATING_BOUNDS_H */
 414
 415 /**
 416  * page_has_private - Determine if page has private stuff
 417  * @page: The page to be checked
 418  *
 419  * Determine if a page has private stuff, indicating that release routines
 420  * should be invoked upon it.
 421  */
 422 #define page_has_private(page)                  \
 423         ((page)->flags & ((1 << PG_private) |   \
 424                           (1 << PG_private_2)))
 425
 426 #endif  /* PAGE_FLAGS_H */