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