linux/include/linux/page-flags.h
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   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 */
  74enum 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#ifdef CONFIG_PAGEFLAGS_EXTENDED
  90        PG_head,                /* A head page */
  91        PG_tail,                /* A tail page */
  92#else
  93        PG_compound,            /* A compound page */
  94#endif
  95        PG_swapcache,           /* Swap page: swp_entry_t in private */
  96        PG_mappedtodisk,        /* Has blocks allocated on-disk */
  97        PG_reclaim,             /* To be reclaimed asap */
  98        PG_swapbacked,          /* Page is backed by RAM/swap */
  99        PG_unevictable,         /* Page is "unevictable"  */
 100#ifdef CONFIG_MMU
 101        PG_mlocked,             /* Page is vma mlocked */
 102#endif
 103#ifdef CONFIG_ARCH_USES_PG_UNCACHED
 104        PG_uncached,            /* Page has been mapped as uncached */
 105#endif
 106#ifdef CONFIG_MEMORY_FAILURE
 107        PG_hwpoison,            /* hardware poisoned page. Don't touch */
 108#endif
 109#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 110        PG_compound_lock,
 111#endif
 112#if defined(CONFIG_IDLE_PAGE_TRACKING) && defined(CONFIG_64BIT)
 113        PG_young,
 114        PG_idle,
 115#endif
 116        __NR_PAGEFLAGS,
 117
 118        /* Filesystems */
 119        PG_checked = PG_owner_priv_1,
 120
 121        /* Two page bits are conscripted by FS-Cache to maintain local caching
 122         * state.  These bits are set on pages belonging to the netfs's inodes
 123         * when those inodes are being locally cached.
 124         */
 125        PG_fscache = PG_private_2,      /* page backed by cache */
 126
 127        /* XEN */
 128        /* Pinned in Xen as a read-only pagetable page. */
 129        PG_pinned = PG_owner_priv_1,
 130        /* Pinned as part of domain save (see xen_mm_pin_all()). */
 131        PG_savepinned = PG_dirty,
 132        /* Has a grant mapping of another (foreign) domain's page. */
 133        PG_foreign = PG_owner_priv_1,
 134
 135        /* SLOB */
 136        PG_slob_free = PG_private,
 137};
 138
 139#ifndef __GENERATING_BOUNDS_H
 140
 141/*
 142 * Macros to create function definitions for page flags
 143 */
 144#define TESTPAGEFLAG(uname, lname)                                      \
 145static inline int Page##uname(const struct page *page)                  \
 146                        { return test_bit(PG_##lname, &page->flags); }
 147
 148#define SETPAGEFLAG(uname, lname)                                       \
 149static inline void SetPage##uname(struct page *page)                    \
 150                        { set_bit(PG_##lname, &page->flags); }
 151
 152#define CLEARPAGEFLAG(uname, lname)                                     \
 153static inline void ClearPage##uname(struct page *page)                  \
 154                        { clear_bit(PG_##lname, &page->flags); }
 155
 156#define __SETPAGEFLAG(uname, lname)                                     \
 157static inline void __SetPage##uname(struct page *page)                  \
 158                        { __set_bit(PG_##lname, &page->flags); }
 159
 160#define __CLEARPAGEFLAG(uname, lname)                                   \
 161static inline void __ClearPage##uname(struct page *page)                \
 162                        { __clear_bit(PG_##lname, &page->flags); }
 163
 164#define TESTSETFLAG(uname, lname)                                       \
 165static inline int TestSetPage##uname(struct page *page)                 \
 166                { return test_and_set_bit(PG_##lname, &page->flags); }
 167
 168#define TESTCLEARFLAG(uname, lname)                                     \
 169static inline int TestClearPage##uname(struct page *page)               \
 170                { return test_and_clear_bit(PG_##lname, &page->flags); }
 171
 172#define __TESTCLEARFLAG(uname, lname)                                   \
 173static inline int __TestClearPage##uname(struct page *page)             \
 174                { return __test_and_clear_bit(PG_##lname, &page->flags); }
 175
 176#define PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)               \
 177        SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname)
 178
 179#define __PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)             \
 180        __SETPAGEFLAG(uname, lname)  __CLEARPAGEFLAG(uname, lname)
 181
 182#define TESTSCFLAG(uname, lname)                                        \
 183        TESTSETFLAG(uname, lname) TESTCLEARFLAG(uname, lname)
 184
 185#define TESTPAGEFLAG_FALSE(uname)                                       \
 186static inline int Page##uname(const struct page *page) { return 0; }
 187
 188#define SETPAGEFLAG_NOOP(uname)                                         \
 189static inline void SetPage##uname(struct page *page) {  }
 190
 191#define CLEARPAGEFLAG_NOOP(uname)                                       \
 192static inline void ClearPage##uname(struct page *page) {  }
 193
 194#define __CLEARPAGEFLAG_NOOP(uname)                                     \
 195static inline void __ClearPage##uname(struct page *page) {  }
 196
 197#define TESTSETFLAG_FALSE(uname)                                        \
 198static inline int TestSetPage##uname(struct page *page) { return 0; }
 199
 200#define TESTCLEARFLAG_FALSE(uname)                                      \
 201static inline int TestClearPage##uname(struct page *page) { return 0; }
 202
 203#define __TESTCLEARFLAG_FALSE(uname)                                    \
 204static inline int __TestClearPage##uname(struct page *page) { return 0; }
 205
 206#define PAGEFLAG_FALSE(uname) TESTPAGEFLAG_FALSE(uname)                 \
 207        SETPAGEFLAG_NOOP(uname) CLEARPAGEFLAG_NOOP(uname)
 208
 209#define TESTSCFLAG_FALSE(uname)                                         \
 210        TESTSETFLAG_FALSE(uname) TESTCLEARFLAG_FALSE(uname)
 211
 212struct page;    /* forward declaration */
 213
 214TESTPAGEFLAG(Locked, locked)
 215PAGEFLAG(Error, error) TESTCLEARFLAG(Error, error)
 216PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced)
 217        __SETPAGEFLAG(Referenced, referenced)
 218PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty, dirty)
 219PAGEFLAG(LRU, lru) __CLEARPAGEFLAG(LRU, lru)
 220PAGEFLAG(Active, active) __CLEARPAGEFLAG(Active, active)
 221        TESTCLEARFLAG(Active, active)
 222__PAGEFLAG(Slab, slab)
 223PAGEFLAG(Checked, checked)              /* Used by some filesystems */
 224PAGEFLAG(Pinned, pinned) TESTSCFLAG(Pinned, pinned)     /* Xen */
 225PAGEFLAG(SavePinned, savepinned);                       /* Xen */
 226PAGEFLAG(Foreign, foreign);                             /* Xen */
 227PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
 228PAGEFLAG(SwapBacked, swapbacked) __CLEARPAGEFLAG(SwapBacked, swapbacked)
 229        __SETPAGEFLAG(SwapBacked, swapbacked)
 230
 231__PAGEFLAG(SlobFree, slob_free)
 232
 233/*
 234 * Private page markings that may be used by the filesystem that owns the page
 235 * for its own purposes.
 236 * - PG_private and PG_private_2 cause releasepage() and co to be invoked
 237 */
 238PAGEFLAG(Private, private) __SETPAGEFLAG(Private, private)
 239        __CLEARPAGEFLAG(Private, private)
 240PAGEFLAG(Private2, private_2) TESTSCFLAG(Private2, private_2)
 241PAGEFLAG(OwnerPriv1, owner_priv_1) TESTCLEARFLAG(OwnerPriv1, owner_priv_1)
 242
 243/*
 244 * Only test-and-set exist for PG_writeback.  The unconditional operators are
 245 * risky: they bypass page accounting.
 246 */
 247TESTPAGEFLAG(Writeback, writeback) TESTSCFLAG(Writeback, writeback)
 248PAGEFLAG(MappedToDisk, mappedtodisk)
 249
 250/* PG_readahead is only used for reads; PG_reclaim is only for writes */
 251PAGEFLAG(Reclaim, reclaim) TESTCLEARFLAG(Reclaim, reclaim)
 252PAGEFLAG(Readahead, reclaim) TESTCLEARFLAG(Readahead, reclaim)
 253
 254#ifdef CONFIG_HIGHMEM
 255/*
 256 * Must use a macro here due to header dependency issues. page_zone() is not
 257 * available at this point.
 258 */
 259#define PageHighMem(__p) is_highmem(page_zone(__p))
 260#else
 261PAGEFLAG_FALSE(HighMem)
 262#endif
 263
 264#ifdef CONFIG_SWAP
 265PAGEFLAG(SwapCache, swapcache)
 266#else
 267PAGEFLAG_FALSE(SwapCache)
 268#endif
 269
 270PAGEFLAG(Unevictable, unevictable) __CLEARPAGEFLAG(Unevictable, unevictable)
 271        TESTCLEARFLAG(Unevictable, unevictable)
 272
 273#ifdef CONFIG_MMU
 274PAGEFLAG(Mlocked, mlocked) __CLEARPAGEFLAG(Mlocked, mlocked)
 275        TESTSCFLAG(Mlocked, mlocked) __TESTCLEARFLAG(Mlocked, mlocked)
 276#else
 277PAGEFLAG_FALSE(Mlocked) __CLEARPAGEFLAG_NOOP(Mlocked)
 278        TESTSCFLAG_FALSE(Mlocked) __TESTCLEARFLAG_FALSE(Mlocked)
 279#endif
 280
 281#ifdef CONFIG_ARCH_USES_PG_UNCACHED
 282PAGEFLAG(Uncached, uncached)
 283#else
 284PAGEFLAG_FALSE(Uncached)
 285#endif
 286
 287#ifdef CONFIG_MEMORY_FAILURE
 288PAGEFLAG(HWPoison, hwpoison)
 289TESTSCFLAG(HWPoison, hwpoison)
 290#define __PG_HWPOISON (1UL << PG_hwpoison)
 291#else
 292PAGEFLAG_FALSE(HWPoison)
 293#define __PG_HWPOISON 0
 294#endif
 295
 296#if defined(CONFIG_IDLE_PAGE_TRACKING) && defined(CONFIG_64BIT)
 297TESTPAGEFLAG(Young, young)
 298SETPAGEFLAG(Young, young)
 299TESTCLEARFLAG(Young, young)
 300PAGEFLAG(Idle, idle)
 301#endif
 302
 303/*
 304 * On an anonymous page mapped into a user virtual memory area,
 305 * page->mapping points to its anon_vma, not to a struct address_space;
 306 * with the PAGE_MAPPING_ANON bit set to distinguish it.  See rmap.h.
 307 *
 308 * On an anonymous page in a VM_MERGEABLE area, if CONFIG_KSM is enabled,
 309 * the PAGE_MAPPING_KSM bit may be set along with the PAGE_MAPPING_ANON bit;
 310 * and then page->mapping points, not to an anon_vma, but to a private
 311 * structure which KSM associates with that merged page.  See ksm.h.
 312 *
 313 * PAGE_MAPPING_KSM without PAGE_MAPPING_ANON is currently never used.
 314 *
 315 * Please note that, confusingly, "page_mapping" refers to the inode
 316 * address_space which maps the page from disk; whereas "page_mapped"
 317 * refers to user virtual address space into which the page is mapped.
 318 */
 319#define PAGE_MAPPING_ANON       1
 320#define PAGE_MAPPING_KSM        2
 321#define PAGE_MAPPING_FLAGS      (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM)
 322
 323static inline int PageAnon(struct page *page)
 324{
 325        return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0;
 326}
 327
 328#ifdef CONFIG_KSM
 329/*
 330 * A KSM page is one of those write-protected "shared pages" or "merged pages"
 331 * which KSM maps into multiple mms, wherever identical anonymous page content
 332 * is found in VM_MERGEABLE vmas.  It's a PageAnon page, pointing not to any
 333 * anon_vma, but to that page's node of the stable tree.
 334 */
 335static inline int PageKsm(struct page *page)
 336{
 337        return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) ==
 338                                (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
 339}
 340#else
 341TESTPAGEFLAG_FALSE(Ksm)
 342#endif
 343
 344u64 stable_page_flags(struct page *page);
 345
 346static inline int PageUptodate(struct page *page)
 347{
 348        int ret = test_bit(PG_uptodate, &(page)->flags);
 349
 350        /*
 351         * Must ensure that the data we read out of the page is loaded
 352         * _after_ we've loaded page->flags to check for PageUptodate.
 353         * We can skip the barrier if the page is not uptodate, because
 354         * we wouldn't be reading anything from it.
 355         *
 356         * See SetPageUptodate() for the other side of the story.
 357         */
 358        if (ret)
 359                smp_rmb();
 360
 361        return ret;
 362}
 363
 364static inline void __SetPageUptodate(struct page *page)
 365{
 366        smp_wmb();
 367        __set_bit(PG_uptodate, &(page)->flags);
 368}
 369
 370static inline void SetPageUptodate(struct page *page)
 371{
 372        /*
 373         * Memory barrier must be issued before setting the PG_uptodate bit,
 374         * so that all previous stores issued in order to bring the page
 375         * uptodate are actually visible before PageUptodate becomes true.
 376         */
 377        smp_wmb();
 378        set_bit(PG_uptodate, &(page)->flags);
 379}
 380
 381CLEARPAGEFLAG(Uptodate, uptodate)
 382
 383int test_clear_page_writeback(struct page *page);
 384int __test_set_page_writeback(struct page *page, bool keep_write);
 385
 386#define test_set_page_writeback(page)                   \
 387        __test_set_page_writeback(page, false)
 388#define test_set_page_writeback_keepwrite(page) \
 389        __test_set_page_writeback(page, true)
 390
 391static inline void set_page_writeback(struct page *page)
 392{
 393        test_set_page_writeback(page);
 394}
 395
 396static inline void set_page_writeback_keepwrite(struct page *page)
 397{
 398        test_set_page_writeback_keepwrite(page);
 399}
 400
 401#ifdef CONFIG_PAGEFLAGS_EXTENDED
 402/*
 403 * System with lots of page flags available. This allows separate
 404 * flags for PageHead() and PageTail() checks of compound pages so that bit
 405 * tests can be used in performance sensitive paths. PageCompound is
 406 * generally not used in hot code paths except arch/powerpc/mm/init_64.c
 407 * and arch/powerpc/kvm/book3s_64_vio_hv.c which use it to detect huge pages
 408 * and avoid handling those in real mode.
 409 */
 410__PAGEFLAG(Head, head) CLEARPAGEFLAG(Head, head)
 411__PAGEFLAG(Tail, tail)
 412
 413static inline int PageCompound(struct page *page)
 414{
 415        return page->flags & ((1L << PG_head) | (1L << PG_tail));
 416
 417}
 418#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 419static inline void ClearPageCompound(struct page *page)
 420{
 421        BUG_ON(!PageHead(page));
 422        ClearPageHead(page);
 423}
 424#endif
 425
 426#define PG_head_mask ((1L << PG_head))
 427
 428#else
 429/*
 430 * Reduce page flag use as much as possible by overlapping
 431 * compound page flags with the flags used for page cache pages. Possible
 432 * because PageCompound is always set for compound pages and not for
 433 * pages on the LRU and/or pagecache.
 434 */
 435TESTPAGEFLAG(Compound, compound)
 436__SETPAGEFLAG(Head, compound)  __CLEARPAGEFLAG(Head, compound)
 437
 438/*
 439 * PG_reclaim is used in combination with PG_compound to mark the
 440 * head and tail of a compound page. This saves one page flag
 441 * but makes it impossible to use compound pages for the page cache.
 442 * The PG_reclaim bit would have to be used for reclaim or readahead
 443 * if compound pages enter the page cache.
 444 *
 445 * PG_compound & PG_reclaim     => Tail page
 446 * PG_compound & ~PG_reclaim    => Head page
 447 */
 448#define PG_head_mask ((1L << PG_compound))
 449#define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))
 450
 451static inline int PageHead(struct page *page)
 452{
 453        return ((page->flags & PG_head_tail_mask) == PG_head_mask);
 454}
 455
 456static inline int PageTail(struct page *page)
 457{
 458        return ((page->flags & PG_head_tail_mask) == PG_head_tail_mask);
 459}
 460
 461static inline void __SetPageTail(struct page *page)
 462{
 463        page->flags |= PG_head_tail_mask;
 464}
 465
 466static inline void __ClearPageTail(struct page *page)
 467{
 468        page->flags &= ~PG_head_tail_mask;
 469}
 470
 471#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 472static inline void ClearPageCompound(struct page *page)
 473{
 474        BUG_ON((page->flags & PG_head_tail_mask) != (1 << PG_compound));
 475        clear_bit(PG_compound, &page->flags);
 476}
 477#endif
 478
 479#endif /* !PAGEFLAGS_EXTENDED */
 480
 481#ifdef CONFIG_HUGETLB_PAGE
 482int PageHuge(struct page *page);
 483int PageHeadHuge(struct page *page);
 484bool page_huge_active(struct page *page);
 485#else
 486TESTPAGEFLAG_FALSE(Huge)
 487TESTPAGEFLAG_FALSE(HeadHuge)
 488
 489static inline bool page_huge_active(struct page *page)
 490{
 491        return 0;
 492}
 493#endif
 494
 495
 496#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 497/*
 498 * PageHuge() only returns true for hugetlbfs pages, but not for
 499 * normal or transparent huge pages.
 500 *
 501 * PageTransHuge() returns true for both transparent huge and
 502 * hugetlbfs pages, but not normal pages. PageTransHuge() can only be
 503 * called only in the core VM paths where hugetlbfs pages can't exist.
 504 */
 505static inline int PageTransHuge(struct page *page)
 506{
 507        VM_BUG_ON_PAGE(PageTail(page), page);
 508        return PageHead(page);
 509}
 510
 511/*
 512 * PageTransCompound returns true for both transparent huge pages
 513 * and hugetlbfs pages, so it should only be called when it's known
 514 * that hugetlbfs pages aren't involved.
 515 */
 516static inline int PageTransCompound(struct page *page)
 517{
 518        return PageCompound(page);
 519}
 520
 521/*
 522 * PageTransTail returns true for both transparent huge pages
 523 * and hugetlbfs pages, so it should only be called when it's known
 524 * that hugetlbfs pages aren't involved.
 525 */
 526static inline int PageTransTail(struct page *page)
 527{
 528        return PageTail(page);
 529}
 530
 531#else
 532
 533static inline int PageTransHuge(struct page *page)
 534{
 535        return 0;
 536}
 537
 538static inline int PageTransCompound(struct page *page)
 539{
 540        return 0;
 541}
 542
 543static inline int PageTransTail(struct page *page)
 544{
 545        return 0;
 546}
 547#endif
 548
 549/*
 550 * PageBuddy() indicate that the page is free and in the buddy system
 551 * (see mm/page_alloc.c).
 552 *
 553 * PAGE_BUDDY_MAPCOUNT_VALUE must be <= -2 but better not too close to
 554 * -2 so that an underflow of the page_mapcount() won't be mistaken
 555 * for a genuine PAGE_BUDDY_MAPCOUNT_VALUE. -128 can be created very
 556 * efficiently by most CPU architectures.
 557 */
 558#define PAGE_BUDDY_MAPCOUNT_VALUE (-128)
 559
 560static inline int PageBuddy(struct page *page)
 561{
 562        return atomic_read(&page->_mapcount) == PAGE_BUDDY_MAPCOUNT_VALUE;
 563}
 564
 565static inline void __SetPageBuddy(struct page *page)
 566{
 567        VM_BUG_ON_PAGE(atomic_read(&page->_mapcount) != -1, page);
 568        atomic_set(&page->_mapcount, PAGE_BUDDY_MAPCOUNT_VALUE);
 569}
 570
 571static inline void __ClearPageBuddy(struct page *page)
 572{
 573        VM_BUG_ON_PAGE(!PageBuddy(page), page);
 574        atomic_set(&page->_mapcount, -1);
 575}
 576
 577#define PAGE_BALLOON_MAPCOUNT_VALUE (-256)
 578
 579static inline int PageBalloon(struct page *page)
 580{
 581        return atomic_read(&page->_mapcount) == PAGE_BALLOON_MAPCOUNT_VALUE;
 582}
 583
 584static inline void __SetPageBalloon(struct page *page)
 585{
 586        VM_BUG_ON_PAGE(atomic_read(&page->_mapcount) != -1, page);
 587        atomic_set(&page->_mapcount, PAGE_BALLOON_MAPCOUNT_VALUE);
 588}
 589
 590static inline void __ClearPageBalloon(struct page *page)
 591{
 592        VM_BUG_ON_PAGE(!PageBalloon(page), page);
 593        atomic_set(&page->_mapcount, -1);
 594}
 595
 596/*
 597 * If network-based swap is enabled, sl*b must keep track of whether pages
 598 * were allocated from pfmemalloc reserves.
 599 */
 600static inline int PageSlabPfmemalloc(struct page *page)
 601{
 602        VM_BUG_ON_PAGE(!PageSlab(page), page);
 603        return PageActive(page);
 604}
 605
 606static inline void SetPageSlabPfmemalloc(struct page *page)
 607{
 608        VM_BUG_ON_PAGE(!PageSlab(page), page);
 609        SetPageActive(page);
 610}
 611
 612static inline void __ClearPageSlabPfmemalloc(struct page *page)
 613{
 614        VM_BUG_ON_PAGE(!PageSlab(page), page);
 615        __ClearPageActive(page);
 616}
 617
 618static inline void ClearPageSlabPfmemalloc(struct page *page)
 619{
 620        VM_BUG_ON_PAGE(!PageSlab(page), page);
 621        ClearPageActive(page);
 622}
 623
 624#ifdef CONFIG_MMU
 625#define __PG_MLOCKED            (1 << PG_mlocked)
 626#else
 627#define __PG_MLOCKED            0
 628#endif
 629
 630#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 631#define __PG_COMPOUND_LOCK              (1 << PG_compound_lock)
 632#else
 633#define __PG_COMPOUND_LOCK              0
 634#endif
 635
 636/*
 637 * Flags checked when a page is freed.  Pages being freed should not have
 638 * these flags set.  It they are, there is a problem.
 639 */
 640#define PAGE_FLAGS_CHECK_AT_FREE \
 641        (1 << PG_lru     | 1 << PG_locked    | \
 642         1 << PG_private | 1 << PG_private_2 | \
 643         1 << PG_writeback | 1 << PG_reserved | \
 644         1 << PG_slab    | 1 << PG_swapcache | 1 << PG_active | \
 645         1 << PG_unevictable | __PG_MLOCKED | \
 646         __PG_COMPOUND_LOCK)
 647
 648/*
 649 * Flags checked when a page is prepped for return by the page allocator.
 650 * Pages being prepped should not have these flags set.  It they are set,
 651 * there has been a kernel bug or struct page corruption.
 652 *
 653 * __PG_HWPOISON is exceptional because it needs to be kept beyond page's
 654 * alloc-free cycle to prevent from reusing the page.
 655 */
 656#define PAGE_FLAGS_CHECK_AT_PREP        \
 657        (((1 << NR_PAGEFLAGS) - 1) & ~__PG_HWPOISON)
 658
 659#define PAGE_FLAGS_PRIVATE                              \
 660        (1 << PG_private | 1 << PG_private_2)
 661/**
 662 * page_has_private - Determine if page has private stuff
 663 * @page: The page to be checked
 664 *
 665 * Determine if a page has private stuff, indicating that release routines
 666 * should be invoked upon it.
 667 */
 668static inline int page_has_private(struct page *page)
 669{
 670        return !!(page->flags & PAGE_FLAGS_PRIVATE);
 671}
 672
 673#endif /* !__GENERATING_BOUNDS_H */
 674
 675#endif  /* PAGE_FLAGS_H */
 676