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/bug.h>
  10 #include <linux/mmdebug.h>
  11 #ifndef __GENERATING_BOUNDS_H
  12 #include <linux/mm_types.h>
  13 #include <generated/bounds.h>
  14 #endif /* !__GENERATING_BOUNDS_H */
  15
  16 /*
  17  * Various page->flags bits:
  18  *
  19  * PG_reserved is set for special pages, which can never be swapped out. Some
  20  * of them might not even exist (eg empty_bad_page)...
  21  *
  22  * The PG_private bitflag is set on pagecache pages if they contain filesystem
  23  * specific data (which is normally at page->private). It can be used by
  24  * private allocations for its own usage.
  25  *
  26  * During initiation of disk I/O, PG_locked is set. This bit is set before I/O
  27  * and cleared when writeback _starts_ or when read _completes_. PG_writeback
  28  * is set before writeback starts and cleared when it finishes.
  29  *
  30  * PG_locked also pins a page in pagecache, and blocks truncation of the file
  31  * while it is held.
  32  *
  33  * page_waitqueue(page) is a wait queue of all tasks waiting for the page
  34  * to become unlocked.
  35  *
  36  * PG_uptodate tells whether the page's contents is valid.  When a read
  37  * completes, the page becomes uptodate, unless a disk I/O error happened.
  38  *
  39  * PG_referenced, PG_reclaim are used for page reclaim for anonymous and
  40  * file-backed pagecache (see mm/vmscan.c).
  41  *
  42  * PG_error is set to indicate that an I/O error occurred on this page.
  43  *
  44  * PG_arch_1 is an architecture specific page state bit.  The generic code
  45  * guarantees that this bit is cleared for a page when it first is entered into
  46  * the page cache.
  47  *
  48  * PG_highmem pages are not permanently mapped into the kernel virtual address
  49  * space, they need to be kmapped separately for doing IO on the pages.  The
  50  * struct page (these bits with information) are always mapped into kernel
  51  * address space...
  52  *
  53  * PG_hwpoison indicates that a page got corrupted in hardware and contains
  54  * data with incorrect ECC bits that triggered a machine check. Accessing is
  55  * not safe since it may cause another machine check. Don't touch!
  56  */
  57
  58 /*
  59  * Don't use the *_dontuse flags.  Use the macros.  Otherwise you'll break
  60  * locked- and dirty-page accounting.
  61  *
  62  * The page flags field is split into two parts, the main flags area
  63  * which extends from the low bits upwards, and the fields area which
  64  * extends from the high bits downwards.
  65  *
  66  *  | FIELD | ... | FLAGS |
  67  *  N-1           ^       0
  68  *               (NR_PAGEFLAGS)
  69  *
  70  * The fields area is reserved for fields mapping zone, node (for NUMA) and
  71  * SPARSEMEM section (for variants of SPARSEMEM that require section ids like
  72  * SPARSEMEM_EXTREME with !SPARSEMEM_VMEMMAP).
  73  */
  74 enum pageflags {
  75         PG_locked,              /* Page is locked. Don't touch. */
  76         PG_error,
  77         PG_referenced,
  78         PG_uptodate,
  79         PG_dirty,
  80         PG_lru,
  81         PG_active,
  82         PG_slab,
  83         PG_owner_priv_1,        /* Owner use. If pagecache, fs may use*/
  84         PG_arch_1,
  85         PG_reserved,
  86         PG_private,             /* If pagecache, has fs-private data */
  87         PG_private_2,           /* If pagecache, has fs aux data */
  88         PG_writeback,           /* Page is under writeback */
  89         PG_head,                /* A head page */
  90         PG_swapcache,           /* Swap page: swp_entry_t in private */
  91         PG_mappedtodisk,        /* Has blocks allocated on-disk */
  92         PG_reclaim,             /* To be reclaimed asap */
  93         PG_swapbacked,          /* Page is backed by RAM/swap */
  94         PG_unevictable,         /* Page is "unevictable"  */
  95 #ifdef CONFIG_MMU
  96         PG_mlocked,             /* Page is vma mlocked */
  97 #endif
  98 #ifdef CONFIG_ARCH_USES_PG_UNCACHED
  99         PG_uncached,            /* Page has been mapped as uncached */
 100 #endif
 101 #ifdef CONFIG_MEMORY_FAILURE
 102         PG_hwpoison,            /* hardware poisoned page. Don't touch */
 103 #endif
 104 #if defined(CONFIG_IDLE_PAGE_TRACKING) && defined(CONFIG_64BIT)
 105         PG_young,
 106         PG_idle,
 107 #endif
 108         __NR_PAGEFLAGS,
 109
 110         /* Filesystems */
 111         PG_checked = PG_owner_priv_1,
 112
 113         /* Two page bits are conscripted by FS-Cache to maintain local caching
 114          * state.  These bits are set on pages belonging to the netfs's inodes
 115          * when those inodes are being locally cached.
 116          */
 117         PG_fscache = PG_private_2,      /* page backed by cache */
 118
 119         /* XEN */
 120         /* Pinned in Xen as a read-only pagetable page. */
 121         PG_pinned = PG_owner_priv_1,
 122         /* Pinned as part of domain save (see xen_mm_pin_all()). */
 123         PG_savepinned = PG_dirty,
 124         /* Has a grant mapping of another (foreign) domain's page. */
 125         PG_foreign = PG_owner_priv_1,
 126
 127         /* SLOB */
 128         PG_slob_free = PG_private,
 129
 130         /* Compound pages. Stored in first tail page's flags */
 131         PG_double_map = PG_private_2,
 132 };
 133
 134 #ifndef __GENERATING_BOUNDS_H
 135
 136 struct page;    /* forward declaration */
 137
 138 static inline struct page *compound_head(struct page *page)
 139 {
 140         unsigned long head = READ_ONCE(page->compound_head);
 141
 142         if (unlikely(head & 1))
 143                 return (struct page *) (head - 1);
 144         return page;
 145 }
 146
 147 static inline int PageTail(struct page *page)
 148 {
 149         return READ_ONCE(page->compound_head) & 1;
 150 }
 151
 152 static inline int PageCompound(struct page *page)
 153 {
 154         return test_bit(PG_head, &page->flags) || PageTail(page);
 155 }
 156
 157 /*
 158  * Page flags policies wrt compound pages
 159  *
 160  * PF_ANY:
 161  *     the page flag is relevant for small, head and tail pages.
 162  *
 163  * PF_HEAD:
 164  *     for compound page all operations related to the page flag applied to
 165  *     head page.
 166  *
 167  * PF_NO_TAIL:
 168  *     modifications of the page flag must be done on small or head pages,
 169  *     checks can be done on tail pages too.
 170  *
 171  * PF_NO_COMPOUND:
 172  *     the page flag is not relevant for compound pages.
 173  */
 174 #define PF_ANY(page, enforce)   page
 175 #define PF_HEAD(page, enforce)  compound_head(page)
 176 #define PF_NO_TAIL(page, enforce) ({                                    \
 177                 VM_BUG_ON_PGFLAGS(enforce && PageTail(page), page);     \
 178                 compound_head(page);})
 179 #define PF_NO_COMPOUND(page, enforce) ({                                \
 180                 VM_BUG_ON_PGFLAGS(enforce && PageCompound(page), page); \
 181                 page;})
 182
 183 /*
 184  * Macros to create function definitions for page flags
 185  */
 186 #define TESTPAGEFLAG(uname, lname, policy)                              \
 187 static inline int Page##uname(struct page *page)                        \
 188         { return test_bit(PG_##lname, &policy(page, 0)->flags); }
 189
 190 #define SETPAGEFLAG(uname, lname, policy)                               \
 191 static inline void SetPage##uname(struct page *page)                    \
 192         { set_bit(PG_##lname, &policy(page, 1)->flags); }
 193
 194 #define CLEARPAGEFLAG(uname, lname, policy)                             \
 195 static inline void ClearPage##uname(struct page *page)                  \
 196         { clear_bit(PG_##lname, &policy(page, 1)->flags); }
 197
 198 #define __SETPAGEFLAG(uname, lname, policy)                             \
 199 static inline void __SetPage##uname(struct page *page)                  \
 200         { __set_bit(PG_##lname, &policy(page, 1)->flags); }
 201
 202 #define __CLEARPAGEFLAG(uname, lname, policy)                           \
 203 static inline void __ClearPage##uname(struct page *page)                \
 204         { __clear_bit(PG_##lname, &policy(page, 1)->flags); }
 205
 206 #define TESTSETFLAG(uname, lname, policy)                               \
 207 static inline int TestSetPage##uname(struct page *page)                 \
 208         { return test_and_set_bit(PG_##lname, &policy(page, 1)->flags); }
 209
 210 #define TESTCLEARFLAG(uname, lname, policy)                             \
 211 static inline int TestClearPage##uname(struct page *page)               \
 212         { return test_and_clear_bit(PG_##lname, &policy(page, 1)->flags); }
 213
 214 #define PAGEFLAG(uname, lname, policy)                                  \
 215         TESTPAGEFLAG(uname, lname, policy)                              \
 216         SETPAGEFLAG(uname, lname, policy)                               \
 217         CLEARPAGEFLAG(uname, lname, policy)
 218
 219 #define __PAGEFLAG(uname, lname, policy)                                \
 220         TESTPAGEFLAG(uname, lname, policy)                              \
 221         __SETPAGEFLAG(uname, lname, policy)                             \
 222         __CLEARPAGEFLAG(uname, lname, policy)
 223
 224 #define TESTSCFLAG(uname, lname, policy)                                \
 225         TESTSETFLAG(uname, lname, policy)                               \
 226         TESTCLEARFLAG(uname, lname, policy)
 227
 228 #define TESTPAGEFLAG_FALSE(uname)                                       \
 229 static inline int Page##uname(const struct page *page) { return 0; }
 230
 231 #define SETPAGEFLAG_NOOP(uname)                                         \
 232 static inline void SetPage##uname(struct page *page) {  }
 233
 234 #define CLEARPAGEFLAG_NOOP(uname)                                       \
 235 static inline void ClearPage##uname(struct page *page) {  }
 236
 237 #define __CLEARPAGEFLAG_NOOP(uname)                                     \
 238 static inline void __ClearPage##uname(struct page *page) {  }
 239
 240 #define TESTSETFLAG_FALSE(uname)                                        \
 241 static inline int TestSetPage##uname(struct page *page) { return 0; }
 242
 243 #define TESTCLEARFLAG_FALSE(uname)                                      \
 244 static inline int TestClearPage##uname(struct page *page) { return 0; }
 245
 246 #define PAGEFLAG_FALSE(uname) TESTPAGEFLAG_FALSE(uname)                 \
 247         SETPAGEFLAG_NOOP(uname) CLEARPAGEFLAG_NOOP(uname)
 248
 249 #define TESTSCFLAG_FALSE(uname)                                         \
 250         TESTSETFLAG_FALSE(uname) TESTCLEARFLAG_FALSE(uname)
 251
 252 __PAGEFLAG(Locked, locked, PF_NO_TAIL)
 253 PAGEFLAG(Error, error, PF_NO_COMPOUND) TESTCLEARFLAG(Error, error, PF_NO_COMPOUND)
 254 PAGEFLAG(Referenced, referenced, PF_HEAD)
 255         TESTCLEARFLAG(Referenced, referenced, PF_HEAD)
 256         __SETPAGEFLAG(Referenced, referenced, PF_HEAD)
 257 PAGEFLAG(Dirty, dirty, PF_HEAD) TESTSCFLAG(Dirty, dirty, PF_HEAD)
 258         __CLEARPAGEFLAG(Dirty, dirty, PF_HEAD)
 259 PAGEFLAG(LRU, lru, PF_HEAD) __CLEARPAGEFLAG(LRU, lru, PF_HEAD)
 260 PAGEFLAG(Active, active, PF_HEAD) __CLEARPAGEFLAG(Active, active, PF_HEAD)
 261         TESTCLEARFLAG(Active, active, PF_HEAD)
 262 __PAGEFLAG(Slab, slab, PF_NO_TAIL)
 263 __PAGEFLAG(SlobFree, slob_free, PF_NO_TAIL)
 264 PAGEFLAG(Checked, checked, PF_NO_COMPOUND)         /* Used by some filesystems */
 265
 266 /* Xen */
 267 PAGEFLAG(Pinned, pinned, PF_NO_COMPOUND)
 268         TESTSCFLAG(Pinned, pinned, PF_NO_COMPOUND)
 269 PAGEFLAG(SavePinned, savepinned, PF_NO_COMPOUND);
 270 PAGEFLAG(Foreign, foreign, PF_NO_COMPOUND);
 271
 272 PAGEFLAG(Reserved, reserved, PF_NO_COMPOUND)
 273         __CLEARPAGEFLAG(Reserved, reserved, PF_NO_COMPOUND)
 274 PAGEFLAG(SwapBacked, swapbacked, PF_NO_TAIL)
 275         __CLEARPAGEFLAG(SwapBacked, swapbacked, PF_NO_TAIL)
 276         __SETPAGEFLAG(SwapBacked, swapbacked, PF_NO_TAIL)
 277
 278 /*
 279  * Private page markings that may be used by the filesystem that owns the page
 280  * for its own purposes.
 281  * - PG_private and PG_private_2 cause releasepage() and co to be invoked
 282  */
 283 PAGEFLAG(Private, private, PF_ANY) __SETPAGEFLAG(Private, private, PF_ANY)
 284         __CLEARPAGEFLAG(Private, private, PF_ANY)
 285 PAGEFLAG(Private2, private_2, PF_ANY) TESTSCFLAG(Private2, private_2, PF_ANY)
 286 PAGEFLAG(OwnerPriv1, owner_priv_1, PF_ANY)
 287         TESTCLEARFLAG(OwnerPriv1, owner_priv_1, PF_ANY)
 288
 289 /*
 290  * Only test-and-set exist for PG_writeback.  The unconditional operators are
 291  * risky: they bypass page accounting.
 292  */
 293 TESTPAGEFLAG(Writeback, writeback, PF_NO_COMPOUND)
 294         TESTSCFLAG(Writeback, writeback, PF_NO_COMPOUND)
 295 PAGEFLAG(MappedToDisk, mappedtodisk, PF_NO_COMPOUND)
 296
 297 /* PG_readahead is only used for reads; PG_reclaim is only for writes */
 298 PAGEFLAG(Reclaim, reclaim, PF_NO_COMPOUND)
 299         TESTCLEARFLAG(Reclaim, reclaim, PF_NO_COMPOUND)
 300 PAGEFLAG(Readahead, reclaim, PF_NO_COMPOUND)
 301         TESTCLEARFLAG(Readahead, reclaim, PF_NO_COMPOUND)
 302
 303 #ifdef CONFIG_HIGHMEM
 304 /*
 305  * Must use a macro here due to header dependency issues. page_zone() is not
 306  * available at this point.
 307  */
 308 #define PageHighMem(__p) is_highmem_idx(page_zonenum(__p))
 309 #else
 310 PAGEFLAG_FALSE(HighMem)
 311 #endif
 312
 313 #ifdef CONFIG_SWAP
 314 PAGEFLAG(SwapCache, swapcache, PF_NO_COMPOUND)
 315 #else
 316 PAGEFLAG_FALSE(SwapCache)
 317 #endif
 318
 319 PAGEFLAG(Unevictable, unevictable, PF_HEAD)
 320         __CLEARPAGEFLAG(Unevictable, unevictable, PF_HEAD)
 321         TESTCLEARFLAG(Unevictable, unevictable, PF_HEAD)
 322
 323 #ifdef CONFIG_MMU
 324 PAGEFLAG(Mlocked, mlocked, PF_NO_TAIL)
 325         __CLEARPAGEFLAG(Mlocked, mlocked, PF_NO_TAIL)
 326         TESTSCFLAG(Mlocked, mlocked, PF_NO_TAIL)
 327 #else
 328 PAGEFLAG_FALSE(Mlocked) __CLEARPAGEFLAG_NOOP(Mlocked)
 329         TESTSCFLAG_FALSE(Mlocked)
 330 #endif
 331
 332 #ifdef CONFIG_ARCH_USES_PG_UNCACHED
 333 PAGEFLAG(Uncached, uncached, PF_NO_COMPOUND)
 334 #else
 335 PAGEFLAG_FALSE(Uncached)
 336 #endif
 337
 338 #ifdef CONFIG_MEMORY_FAILURE
 339 PAGEFLAG(HWPoison, hwpoison, PF_ANY)
 340 TESTSCFLAG(HWPoison, hwpoison, PF_ANY)
 341 #define __PG_HWPOISON (1UL << PG_hwpoison)
 342 #else
 343 PAGEFLAG_FALSE(HWPoison)
 344 #define __PG_HWPOISON 0
 345 #endif
 346
 347 #if defined(CONFIG_IDLE_PAGE_TRACKING) && defined(CONFIG_64BIT)
 348 TESTPAGEFLAG(Young, young, PF_ANY)
 349 SETPAGEFLAG(Young, young, PF_ANY)
 350 TESTCLEARFLAG(Young, young, PF_ANY)
 351 PAGEFLAG(Idle, idle, PF_ANY)
 352 #endif
 353
 354 /*
 355  * On an anonymous page mapped into a user virtual memory area,
 356  * page->mapping points to its anon_vma, not to a struct address_space;
 357  * with the PAGE_MAPPING_ANON bit set to distinguish it.  See rmap.h.
 358  *
 359  * On an anonymous page in a VM_MERGEABLE area, if CONFIG_KSM is enabled,
 360  * the PAGE_MAPPING_KSM bit may be set along with the PAGE_MAPPING_ANON bit;
 361  * and then page->mapping points, not to an anon_vma, but to a private
 362  * structure which KSM associates with that merged page.  See ksm.h.
 363  *
 364  * PAGE_MAPPING_KSM without PAGE_MAPPING_ANON is currently never used.
 365  *
 366  * Please note that, confusingly, "page_mapping" refers to the inode
 367  * address_space which maps the page from disk; whereas "page_mapped"
 368  * refers to user virtual address space into which the page is mapped.
 369  */
 370 #define PAGE_MAPPING_ANON       1
 371 #define PAGE_MAPPING_KSM        2
 372 #define PAGE_MAPPING_FLAGS      (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM)
 373
 374 static inline int PageAnon(struct page *page)
 375 {
 376         page = compound_head(page);
 377         return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0;
 378 }
 379
 380 #ifdef CONFIG_KSM
 381 /*
 382  * A KSM page is one of those write-protected "shared pages" or "merged pages"
 383  * which KSM maps into multiple mms, wherever identical anonymous page content
 384  * is found in VM_MERGEABLE vmas.  It's a PageAnon page, pointing not to any
 385  * anon_vma, but to that page's node of the stable tree.
 386  */
 387 static inline int PageKsm(struct page *page)
 388 {
 389         page = compound_head(page);
 390         return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) ==
 391                                 (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
 392 }
 393 #else
 394 TESTPAGEFLAG_FALSE(Ksm)
 395 #endif
 396
 397 u64 stable_page_flags(struct page *page);
 398
 399 static inline int PageUptodate(struct page *page)
 400 {
 401         int ret;
 402         page = compound_head(page);
 403         ret = test_bit(PG_uptodate, &(page)->flags);
 404         /*
 405          * Must ensure that the data we read out of the page is loaded
 406          * _after_ we've loaded page->flags to check for PageUptodate.
 407          * We can skip the barrier if the page is not uptodate, because
 408          * we wouldn't be reading anything from it.
 409          *
 410          * See SetPageUptodate() for the other side of the story.
 411          */
 412         if (ret)
 413                 smp_rmb();
 414
 415         return ret;
 416 }
 417
 418 static inline void __SetPageUptodate(struct page *page)
 419 {
 420         VM_BUG_ON_PAGE(PageTail(page), page);
 421         smp_wmb();
 422         __set_bit(PG_uptodate, &page->flags);
 423 }
 424
 425 static inline void SetPageUptodate(struct page *page)
 426 {
 427         VM_BUG_ON_PAGE(PageTail(page), page);
 428         /*
 429          * Memory barrier must be issued before setting the PG_uptodate bit,
 430          * so that all previous stores issued in order to bring the page
 431          * uptodate are actually visible before PageUptodate becomes true.
 432          */
 433         smp_wmb();
 434         set_bit(PG_uptodate, &page->flags);
 435 }
 436
 437 CLEARPAGEFLAG(Uptodate, uptodate, PF_NO_TAIL)
 438
 439 int test_clear_page_writeback(struct page *page);
 440 int __test_set_page_writeback(struct page *page, bool keep_write);
 441
 442 #define test_set_page_writeback(page)                   \
 443         __test_set_page_writeback(page, false)
 444 #define test_set_page_writeback_keepwrite(page) \
 445         __test_set_page_writeback(page, true)
 446
 447 static inline void set_page_writeback(struct page *page)
 448 {
 449         test_set_page_writeback(page);
 450 }
 451
 452 static inline void set_page_writeback_keepwrite(struct page *page)
 453 {
 454         test_set_page_writeback_keepwrite(page);
 455 }
 456
 457 __PAGEFLAG(Head, head, PF_ANY) CLEARPAGEFLAG(Head, head, PF_ANY)
 458
 459 static inline void set_compound_head(struct page *page, struct page *head)
 460 {
 461         WRITE_ONCE(page->compound_head, (unsigned long)head + 1);
 462 }
 463
 464 static inline void clear_compound_head(struct page *page)
 465 {
 466         WRITE_ONCE(page->compound_head, 0);
 467 }
 468
 469 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 470 static inline void ClearPageCompound(struct page *page)
 471 {
 472         BUG_ON(!PageHead(page));
 473         ClearPageHead(page);
 474 }
 475 #endif
 476
 477 #define PG_head_mask ((1L << PG_head))
 478
 479 #ifdef CONFIG_HUGETLB_PAGE
 480 int PageHuge(struct page *page);
 481 int PageHeadHuge(struct page *page);
 482 bool page_huge_active(struct page *page);
 483 #else
 484 TESTPAGEFLAG_FALSE(Huge)
 485 TESTPAGEFLAG_FALSE(HeadHuge)
 486
 487 static inline bool page_huge_active(struct page *page)
 488 {
 489         return 0;
 490 }
 491 #endif
 492
 493
 494 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 495 /*
 496  * PageHuge() only returns true for hugetlbfs pages, but not for
 497  * normal or transparent huge pages.
 498  *
 499  * PageTransHuge() returns true for both transparent huge and
 500  * hugetlbfs pages, but not normal pages. PageTransHuge() can only be
 501  * called only in the core VM paths where hugetlbfs pages can't exist.
 502  */
 503 static inline int PageTransHuge(struct page *page)
 504 {
 505         VM_BUG_ON_PAGE(PageTail(page), page);
 506         return PageHead(page);
 507 }
 508
 509 /*
 510  * PageTransCompound returns true for both transparent huge pages
 511  * and hugetlbfs pages, so it should only be called when it's known
 512  * that hugetlbfs pages aren't involved.
 513  */
 514 static inline int PageTransCompound(struct page *page)
 515 {
 516         return PageCompound(page);
 517 }
 518
 519 /*
 520  * PageTransTail returns true for both transparent huge pages
 521  * and hugetlbfs pages, so it should only be called when it's known
 522  * that hugetlbfs pages aren't involved.
 523  */
 524 static inline int PageTransTail(struct page *page)
 525 {
 526         return PageTail(page);
 527 }
 528
 529 /*
 530  * PageDoubleMap indicates that the compound page is mapped with PTEs as well
 531  * as PMDs.
 532  *
 533  * This is required for optimization of rmap operations for THP: we can postpone
 534  * per small page mapcount accounting (and its overhead from atomic operations)
 535  * until the first PMD split.
 536  *
 537  * For the page PageDoubleMap means ->_mapcount in all sub-pages is offset up
 538  * by one. This reference will go away with last compound_mapcount.
 539  *
 540  * See also __split_huge_pmd_locked() and page_remove_anon_compound_rmap().
 541  */
 542 static inline int PageDoubleMap(struct page *page)
 543 {
 544         return PageHead(page) && test_bit(PG_double_map, &page[1].flags);
 545 }
 546
 547 static inline int TestSetPageDoubleMap(struct page *page)
 548 {
 549         VM_BUG_ON_PAGE(!PageHead(page), page);
 550         return test_and_set_bit(PG_double_map, &page[1].flags);
 551 }
 552
 553 static inline int TestClearPageDoubleMap(struct page *page)
 554 {
 555         VM_BUG_ON_PAGE(!PageHead(page), page);
 556         return test_and_clear_bit(PG_double_map, &page[1].flags);
 557 }
 558
 559 #else
 560 TESTPAGEFLAG_FALSE(TransHuge)
 561 TESTPAGEFLAG_FALSE(TransCompound)
 562 TESTPAGEFLAG_FALSE(TransTail)
 563 TESTPAGEFLAG_FALSE(DoubleMap)
 564         TESTSETFLAG_FALSE(DoubleMap)
 565         TESTCLEARFLAG_FALSE(DoubleMap)
 566 #endif
 567
 568 /*
 569  * PageBuddy() indicate that the page is free and in the buddy system
 570  * (see mm/page_alloc.c).
 571  *
 572  * PAGE_BUDDY_MAPCOUNT_VALUE must be <= -2 but better not too close to
 573  * -2 so that an underflow of the page_mapcount() won't be mistaken
 574  * for a genuine PAGE_BUDDY_MAPCOUNT_VALUE. -128 can be created very
 575  * efficiently by most CPU architectures.
 576  */
 577 #define PAGE_BUDDY_MAPCOUNT_VALUE (-128)
 578
 579 static inline int PageBuddy(struct page *page)
 580 {
 581         return atomic_read(&page->_mapcount) == PAGE_BUDDY_MAPCOUNT_VALUE;
 582 }
 583
 584 static inline void __SetPageBuddy(struct page *page)
 585 {
 586         VM_BUG_ON_PAGE(atomic_read(&page->_mapcount) != -1, page);
 587         atomic_set(&page->_mapcount, PAGE_BUDDY_MAPCOUNT_VALUE);
 588 }
 589
 590 static inline void __ClearPageBuddy(struct page *page)
 591 {
 592         VM_BUG_ON_PAGE(!PageBuddy(page), page);
 593         atomic_set(&page->_mapcount, -1);
 594 }
 595
 596 #define PAGE_BALLOON_MAPCOUNT_VALUE (-256)
 597
 598 static inline int PageBalloon(struct page *page)
 599 {
 600         return atomic_read(&page->_mapcount) == PAGE_BALLOON_MAPCOUNT_VALUE;
 601 }
 602
 603 static inline void __SetPageBalloon(struct page *page)
 604 {
 605         VM_BUG_ON_PAGE(atomic_read(&page->_mapcount) != -1, page);
 606         atomic_set(&page->_mapcount, PAGE_BALLOON_MAPCOUNT_VALUE);
 607 }
 608
 609 static inline void __ClearPageBalloon(struct page *page)
 610 {
 611         VM_BUG_ON_PAGE(!PageBalloon(page), page);
 612         atomic_set(&page->_mapcount, -1);
 613 }
 614
 615 /*
 616  * If network-based swap is enabled, sl*b must keep track of whether pages
 617  * were allocated from pfmemalloc reserves.
 618  */
 619 static inline int PageSlabPfmemalloc(struct page *page)
 620 {
 621         VM_BUG_ON_PAGE(!PageSlab(page), page);
 622         return PageActive(page);
 623 }
 624
 625 static inline void SetPageSlabPfmemalloc(struct page *page)
 626 {
 627         VM_BUG_ON_PAGE(!PageSlab(page), page);
 628         SetPageActive(page);
 629 }
 630
 631 static inline void __ClearPageSlabPfmemalloc(struct page *page)
 632 {
 633         VM_BUG_ON_PAGE(!PageSlab(page), page);
 634         __ClearPageActive(page);
 635 }
 636
 637 static inline void ClearPageSlabPfmemalloc(struct page *page)
 638 {
 639         VM_BUG_ON_PAGE(!PageSlab(page), page);
 640         ClearPageActive(page);
 641 }
 642
 643 #ifdef CONFIG_MMU
 644 #define __PG_MLOCKED            (1 << PG_mlocked)
 645 #else
 646 #define __PG_MLOCKED            0
 647 #endif
 648
 649 /*
 650  * Flags checked when a page is freed.  Pages being freed should not have
 651  * these flags set.  It they are, there is a problem.
 652  */
 653 #define PAGE_FLAGS_CHECK_AT_FREE \
 654         (1 << PG_lru     | 1 << PG_locked    | \
 655          1 << PG_private | 1 << PG_private_2 | \
 656          1 << PG_writeback | 1 << PG_reserved | \
 657          1 << PG_slab    | 1 << PG_swapcache | 1 << PG_active | \
 658          1 << PG_unevictable | __PG_MLOCKED)
 659
 660 /*
 661  * Flags checked when a page is prepped for return by the page allocator.
 662  * Pages being prepped should not have these flags set.  It they are set,
 663  * there has been a kernel bug or struct page corruption.
 664  *
 665  * __PG_HWPOISON is exceptional because it needs to be kept beyond page's
 666  * alloc-free cycle to prevent from reusing the page.
 667  */
 668 #define PAGE_FLAGS_CHECK_AT_PREP        \
 669         (((1 << NR_PAGEFLAGS) - 1) & ~__PG_HWPOISON)
 670
 671 #define PAGE_FLAGS_PRIVATE                              \
 672         (1 << PG_private | 1 << PG_private_2)
 673 /**
 674  * page_has_private - Determine if page has private stuff
 675  * @page: The page to be checked
 676  *
 677  * Determine if a page has private stuff, indicating that release routines
 678  * should be invoked upon it.
 679  */
 680 static inline int page_has_private(struct page *page)
 681 {
 682         return !!(page->flags & PAGE_FLAGS_PRIVATE);
 683 }
 684
 685 #undef PF_ANY
 686 #undef PF_HEAD
 687 #undef PF_NO_TAIL
 688 #undef PF_NO_COMPOUND
 689 #endif /* !__GENERATING_BOUNDS_H */
 690
 691 #endif  /* PAGE_FLAGS_H */