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_page = PG_active,
 124         PG_slob_free = PG_private,
 125
 126         /* SLUB */
 127         PG_slub_frozen = PG_active,
 128         PG_slub_debug = PG_error,
 129 };
 130
 131 #ifndef __GENERATING_BOUNDS_H
 132
 133 /*
 134  * Macros to create function definitions for page flags
 135  */
 136 #define TESTPAGEFLAG(uname, lname)                                      \
 137 static inline int Page##uname(struct page *page)                        \
 138                         { return test_bit(PG_##lname, &page->flags); }
 139
 140 #define SETPAGEFLAG(uname, lname)                                       \
 141 static inline void SetPage##uname(struct page *page)                    \
 142                         { set_bit(PG_##lname, &page->flags); }
 143
 144 #define CLEARPAGEFLAG(uname, lname)                                     \
 145 static inline void ClearPage##uname(struct page *page)                  \
 146                         { clear_bit(PG_##lname, &page->flags); }
 147
 148 #define __SETPAGEFLAG(uname, lname)                                     \
 149 static inline void __SetPage##uname(struct page *page)                  \
 150                         { __set_bit(PG_##lname, &page->flags); }
 151
 152 #define __CLEARPAGEFLAG(uname, lname)                                   \
 153 static inline void __ClearPage##uname(struct page *page)                \
 154                         { __clear_bit(PG_##lname, &page->flags); }
 155
 156 #define TESTSETFLAG(uname, lname)                                       \
 157 static inline int TestSetPage##uname(struct page *page)                 \
 158                 { return test_and_set_bit(PG_##lname, &page->flags); }
 159
 160 #define TESTCLEARFLAG(uname, lname)                                     \
 161 static inline int TestClearPage##uname(struct page *page)               \
 162                 { return test_and_clear_bit(PG_##lname, &page->flags); }
 163
 164
 165 #define PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)               \
 166         SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname)
 167
 168 #define __PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)             \
 169         __SETPAGEFLAG(uname, lname)  __CLEARPAGEFLAG(uname, lname)
 170
 171 #define PAGEFLAG_FALSE(uname)                                           \
 172 static inline int Page##uname(struct page *page)                        \
 173                         { return 0; }
 174
 175 #define TESTSCFLAG(uname, lname)                                        \
 176         TESTSETFLAG(uname, lname) TESTCLEARFLAG(uname, lname)
 177
 178 #define SETPAGEFLAG_NOOP(uname)                                         \
 179 static inline void SetPage##uname(struct page *page) {  }
 180
 181 #define CLEARPAGEFLAG_NOOP(uname)                                       \
 182 static inline void ClearPage##uname(struct page *page) {  }
 183
 184 #define __CLEARPAGEFLAG_NOOP(uname)                                     \
 185 static inline void __ClearPage##uname(struct page *page) {  }
 186
 187 #define TESTCLEARFLAG_FALSE(uname)                                      \
 188 static inline int TestClearPage##uname(struct page *page) { return 0; }
 189
 190 struct page;    /* forward declaration */
 191
 192 TESTPAGEFLAG(Locked, locked) TESTSETFLAG(Locked, locked)
 193 PAGEFLAG(Error, error)
 194 PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced)
 195 PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty, dirty)
 196 PAGEFLAG(LRU, lru) __CLEARPAGEFLAG(LRU, lru)
 197 PAGEFLAG(Active, active) __CLEARPAGEFLAG(Active, active)
 198         TESTCLEARFLAG(Active, active)
 199 __PAGEFLAG(Slab, slab)
 200 PAGEFLAG(Checked, checked)              /* Used by some filesystems */
 201 PAGEFLAG(Pinned, pinned) TESTSCFLAG(Pinned, pinned)     /* Xen */
 202 PAGEFLAG(SavePinned, savepinned);                       /* Xen */
 203 PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
 204 PAGEFLAG(SwapBacked, swapbacked) __CLEARPAGEFLAG(SwapBacked, swapbacked)
 205
 206 __PAGEFLAG(SlobPage, slob_page)
 207 __PAGEFLAG(SlobFree, slob_free)
 208
 209 __PAGEFLAG(SlubFrozen, slub_frozen)
 210 __PAGEFLAG(SlubDebug, slub_debug)
 211
 212 /*
 213  * Private page markings that may be used by the filesystem that owns the page
 214  * for its own purposes.
 215  * - PG_private and PG_private_2 cause releasepage() and co to be invoked
 216  */
 217 PAGEFLAG(Private, private) __SETPAGEFLAG(Private, private)
 218         __CLEARPAGEFLAG(Private, private)
 219 PAGEFLAG(Private2, private_2) TESTSCFLAG(Private2, private_2)
 220 PAGEFLAG(OwnerPriv1, owner_priv_1) TESTCLEARFLAG(OwnerPriv1, owner_priv_1)
 221
 222 /*
 223  * Only test-and-set exist for PG_writeback.  The unconditional operators are
 224  * risky: they bypass page accounting.
 225  */
 226 TESTPAGEFLAG(Writeback, writeback) TESTSCFLAG(Writeback, writeback)
 227 __PAGEFLAG(Buddy, buddy)
 228 PAGEFLAG(MappedToDisk, mappedtodisk)
 229
 230 /* PG_readahead is only used for file reads; PG_reclaim is only for writes */
 231 PAGEFLAG(Reclaim, reclaim) TESTCLEARFLAG(Reclaim, reclaim)
 232 PAGEFLAG(Readahead, reclaim)            /* Reminder to do async read-ahead */
 233
 234 #ifdef CONFIG_HIGHMEM
 235 /*
 236  * Must use a macro here due to header dependency issues. page_zone() is not
 237  * available at this point.
 238  */
 239 #define PageHighMem(__p) is_highmem(page_zone(__p))
 240 #else
 241 PAGEFLAG_FALSE(HighMem)
 242 #endif
 243
 244 #ifdef CONFIG_SWAP
 245 PAGEFLAG(SwapCache, swapcache)
 246 #else
 247 PAGEFLAG_FALSE(SwapCache)
 248         SETPAGEFLAG_NOOP(SwapCache) CLEARPAGEFLAG_NOOP(SwapCache)
 249 #endif
 250
 251 #ifdef CONFIG_UNEVICTABLE_LRU
 252 PAGEFLAG(Unevictable, unevictable) __CLEARPAGEFLAG(Unevictable, unevictable)
 253         TESTCLEARFLAG(Unevictable, unevictable)
 254 #else
 255 PAGEFLAG_FALSE(Unevictable) TESTCLEARFLAG_FALSE(Unevictable)
 256         SETPAGEFLAG_NOOP(Unevictable) CLEARPAGEFLAG_NOOP(Unevictable)
 257         __CLEARPAGEFLAG_NOOP(Unevictable)
 258 #endif
 259
 260 #ifdef CONFIG_HAVE_MLOCKED_PAGE_BIT
 261 #define MLOCK_PAGES 1
 262 PAGEFLAG(Mlocked, mlocked) __CLEARPAGEFLAG(Mlocked, mlocked)
 263         TESTSCFLAG(Mlocked, mlocked)
 264 #else
 265 #define MLOCK_PAGES 0
 266 PAGEFLAG_FALSE(Mlocked)
 267         SETPAGEFLAG_NOOP(Mlocked) TESTCLEARFLAG_FALSE(Mlocked)
 268 #endif
 269
 270 #ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
 271 PAGEFLAG(Uncached, uncached)
 272 #else
 273 PAGEFLAG_FALSE(Uncached)
 274 #endif
 275
 276 static inline int PageUptodate(struct page *page)
 277 {
 278         int ret = test_bit(PG_uptodate, &(page)->flags);
 279
 280         /*
 281          * Must ensure that the data we read out of the page is loaded
 282          * _after_ we've loaded page->flags to check for PageUptodate.
 283          * We can skip the barrier if the page is not uptodate, because
 284          * we wouldn't be reading anything from it.
 285          *
 286          * See SetPageUptodate() for the other side of the story.
 287          */
 288         if (ret)
 289                 smp_rmb();
 290
 291         return ret;
 292 }
 293
 294 static inline void __SetPageUptodate(struct page *page)
 295 {
 296         smp_wmb();
 297         __set_bit(PG_uptodate, &(page)->flags);
 298 }
 299
 300 static inline void SetPageUptodate(struct page *page)
 301 {
 302 #ifdef CONFIG_S390
 303         if (!test_and_set_bit(PG_uptodate, &page->flags))
 304                 page_clear_dirty(page);
 305 #else
 306         /*
 307          * Memory barrier must be issued before setting the PG_uptodate bit,
 308          * so that all previous stores issued in order to bring the page
 309          * uptodate are actually visible before PageUptodate becomes true.
 310          *
 311          * s390 doesn't need an explicit smp_wmb here because the test and
 312          * set bit already provides full barriers.
 313          */
 314         smp_wmb();
 315         set_bit(PG_uptodate, &(page)->flags);
 316 #endif
 317 }
 318
 319 CLEARPAGEFLAG(Uptodate, uptodate)
 320
 321 extern void cancel_dirty_page(struct page *page, unsigned int account_size);
 322
 323 int test_clear_page_writeback(struct page *page);
 324 int test_set_page_writeback(struct page *page);
 325
 326 static inline void set_page_writeback(struct page *page)
 327 {
 328         test_set_page_writeback(page);
 329 }
 330
 331 #ifdef CONFIG_PAGEFLAGS_EXTENDED
 332 /*
 333  * System with lots of page flags available. This allows separate
 334  * flags for PageHead() and PageTail() checks of compound pages so that bit
 335  * tests can be used in performance sensitive paths. PageCompound is
 336  * generally not used in hot code paths.
 337  */
 338 __PAGEFLAG(Head, head)
 339 __PAGEFLAG(Tail, tail)
 340
 341 static inline int PageCompound(struct page *page)
 342 {
 343         return page->flags & ((1L << PG_head) | (1L << PG_tail));
 344
 345 }
 346 #else
 347 /*
 348  * Reduce page flag use as much as possible by overlapping
 349  * compound page flags with the flags used for page cache pages. Possible
 350  * because PageCompound is always set for compound pages and not for
 351  * pages on the LRU and/or pagecache.
 352  */
 353 TESTPAGEFLAG(Compound, compound)
 354 __PAGEFLAG(Head, compound)
 355
 356 /*
 357  * PG_reclaim is used in combination with PG_compound to mark the
 358  * head and tail of a compound page. This saves one page flag
 359  * but makes it impossible to use compound pages for the page cache.
 360  * The PG_reclaim bit would have to be used for reclaim or readahead
 361  * if compound pages enter the page cache.
 362  *
 363  * PG_compound & PG_reclaim     => Tail page
 364  * PG_compound & ~PG_reclaim    => Head page
 365  */
 366 #define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))
 367
 368 static inline int PageTail(struct page *page)
 369 {
 370         return ((page->flags & PG_head_tail_mask) == PG_head_tail_mask);
 371 }
 372
 373 static inline void __SetPageTail(struct page *page)
 374 {
 375         page->flags |= PG_head_tail_mask;
 376 }
 377
 378 static inline void __ClearPageTail(struct page *page)
 379 {
 380         page->flags &= ~PG_head_tail_mask;
 381 }
 382
 383 #endif /* !PAGEFLAGS_EXTENDED */
 384
 385 #ifdef CONFIG_UNEVICTABLE_LRU
 386 #define __PG_UNEVICTABLE        (1 << PG_unevictable)
 387 #else
 388 #define __PG_UNEVICTABLE        0
 389 #endif
 390
 391 #ifdef CONFIG_HAVE_MLOCKED_PAGE_BIT
 392 #define __PG_MLOCKED            (1 << PG_mlocked)
 393 #else
 394 #define __PG_MLOCKED            0
 395 #endif
 396
 397 /*
 398  * Flags checked when a page is freed.  Pages being freed should not have
 399  * these flags set.  It they are, there is a problem.
 400  */
 401 #define PAGE_FLAGS_CHECK_AT_FREE \
 402         (1 << PG_lru     | 1 << PG_locked    | \
 403          1 << PG_private | 1 << PG_private_2 | \
 404          1 << PG_buddy   | 1 << PG_writeback | 1 << PG_reserved | \
 405          1 << PG_slab    | 1 << PG_swapcache | 1 << PG_active | \
 406          __PG_UNEVICTABLE | __PG_MLOCKED)
 407
 408 /*
 409  * Flags checked when a page is prepped for return by the page allocator.
 410  * Pages being prepped should not have any flags set.  It they are set,
 411  * there has been a kernel bug or struct page corruption.
 412  */
 413 #define PAGE_FLAGS_CHECK_AT_PREP        ((1 << NR_PAGEFLAGS) - 1)
 414
 415 #endif /* !__GENERATING_BOUNDS_H */
 416
 417 /**
 418  * page_has_private - Determine if page has private stuff
 419  * @page: The page to be checked
 420  *
 421  * Determine if a page has private stuff, indicating that release routines
 422  * should be invoked upon it.
 423  */
 424 #define page_has_private(page)                  \
 425         ((page)->flags & ((1 << PG_private) |   \
 426                           (1 << PG_private_2)))
 427
 428 #endif  /* PAGE_FLAGS_H */