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_waiters,             /* Page has waiters, check its waitqueue. Must be bit #7 and in the same byte as "PG_locked" */
  83         PG_slab,
  84         PG_owner_priv_1,        /* Owner use. If pagecache, fs may use*/
  85         PG_arch_1,
  86         PG_reserved,
  87         PG_private,             /* If pagecache, has fs-private data */
  88         PG_private_2,           /* If pagecache, has fs aux data */
  89         PG_writeback,           /* Page is under writeback */
  90         PG_head,                /* A head page */
  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         /* SwapBacked */
 114         PG_swapcache = PG_owner_priv_1, /* Swap page: swp_entry_t in private */
 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         /* Compound pages. Stored in first tail page's flags */
 134         PG_double_map = PG_private_2,
 135
 136         /* non-lru isolated movable page */
 137         PG_isolated = PG_reclaim,
 138 };
 139
 140 #ifndef __GENERATING_BOUNDS_H
 141
 142 struct page;    /* forward declaration */
 143
 144 static inline struct page *compound_head(struct page *page)
 145 {
 146         unsigned long head = READ_ONCE(page->compound_head);
 147
 148         if (unlikely(head & 1))
 149                 return (struct page *) (head - 1);
 150         return page;
 151 }
 152
 153 static __always_inline int PageTail(struct page *page)
 154 {
 155         return READ_ONCE(page->compound_head) & 1;
 156 }
 157
 158 static __always_inline int PageCompound(struct page *page)
 159 {
 160         return test_bit(PG_head, &page->flags) || PageTail(page);
 161 }
 162
 163 /*
 164  * Page flags policies wrt compound pages
 165  *
 166  * PF_ANY:
 167  *     the page flag is relevant for small, head and tail pages.
 168  *
 169  * PF_HEAD:
 170  *     for compound page all operations related to the page flag applied to
 171  *     head page.
 172  *
 173  * PF_ONLY_HEAD:
 174  *     for compound page, callers only ever operate on the head page.
 175  *
 176  * PF_NO_TAIL:
 177  *     modifications of the page flag must be done on small or head pages,
 178  *     checks can be done on tail pages too.
 179  *
 180  * PF_NO_COMPOUND:
 181  *     the page flag is not relevant for compound pages.
 182  */
 183 #define PF_ANY(page, enforce)   page
 184 #define PF_HEAD(page, enforce)  compound_head(page)
 185 #define PF_ONLY_HEAD(page, enforce) ({                                  \
 186                 VM_BUG_ON_PGFLAGS(PageTail(page), page);                \
 187                 page;})
 188 #define PF_NO_TAIL(page, enforce) ({                                    \
 189                 VM_BUG_ON_PGFLAGS(enforce && PageTail(page), page);     \
 190                 compound_head(page);})
 191 #define PF_NO_COMPOUND(page, enforce) ({                                \
 192                 VM_BUG_ON_PGFLAGS(enforce && PageCompound(page), page); \
 193                 page;})
 194
 195 /*
 196  * Macros to create function definitions for page flags
 197  */
 198 #define TESTPAGEFLAG(uname, lname, policy)                              \
 199 static __always_inline int Page##uname(struct page *page)               \
 200         { return test_bit(PG_##lname, &policy(page, 0)->flags); }
 201
 202 #define SETPAGEFLAG(uname, lname, policy)                               \
 203 static __always_inline void SetPage##uname(struct page *page)           \
 204         { set_bit(PG_##lname, &policy(page, 1)->flags); }
 205
 206 #define CLEARPAGEFLAG(uname, lname, policy)                             \
 207 static __always_inline void ClearPage##uname(struct page *page)         \
 208         { clear_bit(PG_##lname, &policy(page, 1)->flags); }
 209
 210 #define __SETPAGEFLAG(uname, lname, policy)                             \
 211 static __always_inline void __SetPage##uname(struct page *page)         \
 212         { __set_bit(PG_##lname, &policy(page, 1)->flags); }
 213
 214 #define __CLEARPAGEFLAG(uname, lname, policy)                           \
 215 static __always_inline void __ClearPage##uname(struct page *page)       \
 216         { __clear_bit(PG_##lname, &policy(page, 1)->flags); }
 217
 218 #define TESTSETFLAG(uname, lname, policy)                               \
 219 static __always_inline int TestSetPage##uname(struct page *page)        \
 220         { return test_and_set_bit(PG_##lname, &policy(page, 1)->flags); }
 221
 222 #define TESTCLEARFLAG(uname, lname, policy)                             \
 223 static __always_inline int TestClearPage##uname(struct page *page)      \
 224         { return test_and_clear_bit(PG_##lname, &policy(page, 1)->flags); }
 225
 226 #define PAGEFLAG(uname, lname, policy)                                  \
 227         TESTPAGEFLAG(uname, lname, policy)                              \
 228         SETPAGEFLAG(uname, lname, policy)                               \
 229         CLEARPAGEFLAG(uname, lname, policy)
 230
 231 #define __PAGEFLAG(uname, lname, policy)                                \
 232         TESTPAGEFLAG(uname, lname, policy)                              \
 233         __SETPAGEFLAG(uname, lname, policy)                             \
 234         __CLEARPAGEFLAG(uname, lname, policy)
 235
 236 #define TESTSCFLAG(uname, lname, policy)                                \
 237         TESTSETFLAG(uname, lname, policy)                               \
 238         TESTCLEARFLAG(uname, lname, policy)
 239
 240 #define TESTPAGEFLAG_FALSE(uname)                                       \
 241 static inline int Page##uname(const struct page *page) { return 0; }
 242
 243 #define SETPAGEFLAG_NOOP(uname)                                         \
 244 static inline void SetPage##uname(struct page *page) {  }
 245
 246 #define CLEARPAGEFLAG_NOOP(uname)                                       \
 247 static inline void ClearPage##uname(struct page *page) {  }
 248
 249 #define __CLEARPAGEFLAG_NOOP(uname)                                     \
 250 static inline void __ClearPage##uname(struct page *page) {  }
 251
 252 #define TESTSETFLAG_FALSE(uname)                                        \
 253 static inline int TestSetPage##uname(struct page *page) { return 0; }
 254
 255 #define TESTCLEARFLAG_FALSE(uname)                                      \
 256 static inline int TestClearPage##uname(struct page *page) { return 0; }
 257
 258 #define PAGEFLAG_FALSE(uname) TESTPAGEFLAG_FALSE(uname)                 \
 259         SETPAGEFLAG_NOOP(uname) CLEARPAGEFLAG_NOOP(uname)
 260
 261 #define TESTSCFLAG_FALSE(uname)                                         \
 262         TESTSETFLAG_FALSE(uname) TESTCLEARFLAG_FALSE(uname)
 263
 264 __PAGEFLAG(Locked, locked, PF_NO_TAIL)
 265 PAGEFLAG(Waiters, waiters, PF_ONLY_HEAD) __CLEARPAGEFLAG(Waiters, waiters, PF_ONLY_HEAD)
 266 PAGEFLAG(Error, error, PF_NO_COMPOUND) TESTCLEARFLAG(Error, error, PF_NO_COMPOUND)
 267 PAGEFLAG(Referenced, referenced, PF_HEAD)
 268         TESTCLEARFLAG(Referenced, referenced, PF_HEAD)
 269         __SETPAGEFLAG(Referenced, referenced, PF_HEAD)
 270 PAGEFLAG(Dirty, dirty, PF_HEAD) TESTSCFLAG(Dirty, dirty, PF_HEAD)
 271         __CLEARPAGEFLAG(Dirty, dirty, PF_HEAD)
 272 PAGEFLAG(LRU, lru, PF_HEAD) __CLEARPAGEFLAG(LRU, lru, PF_HEAD)
 273 PAGEFLAG(Active, active, PF_HEAD) __CLEARPAGEFLAG(Active, active, PF_HEAD)
 274         TESTCLEARFLAG(Active, active, PF_HEAD)
 275 __PAGEFLAG(Slab, slab, PF_NO_TAIL)
 276 __PAGEFLAG(SlobFree, slob_free, PF_NO_TAIL)
 277 PAGEFLAG(Checked, checked, PF_NO_COMPOUND)         /* Used by some filesystems */
 278
 279 /* Xen */
 280 PAGEFLAG(Pinned, pinned, PF_NO_COMPOUND)
 281         TESTSCFLAG(Pinned, pinned, PF_NO_COMPOUND)
 282 PAGEFLAG(SavePinned, savepinned, PF_NO_COMPOUND);
 283 PAGEFLAG(Foreign, foreign, PF_NO_COMPOUND);
 284
 285 PAGEFLAG(Reserved, reserved, PF_NO_COMPOUND)
 286         __CLEARPAGEFLAG(Reserved, reserved, PF_NO_COMPOUND)
 287 PAGEFLAG(SwapBacked, swapbacked, PF_NO_TAIL)
 288         __CLEARPAGEFLAG(SwapBacked, swapbacked, PF_NO_TAIL)
 289         __SETPAGEFLAG(SwapBacked, swapbacked, PF_NO_TAIL)
 290
 291 /*
 292  * Private page markings that may be used by the filesystem that owns the page
 293  * for its own purposes.
 294  * - PG_private and PG_private_2 cause releasepage() and co to be invoked
 295  */
 296 PAGEFLAG(Private, private, PF_ANY) __SETPAGEFLAG(Private, private, PF_ANY)
 297         __CLEARPAGEFLAG(Private, private, PF_ANY)
 298 PAGEFLAG(Private2, private_2, PF_ANY) TESTSCFLAG(Private2, private_2, PF_ANY)
 299 PAGEFLAG(OwnerPriv1, owner_priv_1, PF_ANY)
 300         TESTCLEARFLAG(OwnerPriv1, owner_priv_1, PF_ANY)
 301
 302 /*
 303  * Only test-and-set exist for PG_writeback.  The unconditional operators are
 304  * risky: they bypass page accounting.
 305  */
 306 TESTPAGEFLAG(Writeback, writeback, PF_NO_COMPOUND)
 307         TESTSCFLAG(Writeback, writeback, PF_NO_COMPOUND)
 308 PAGEFLAG(MappedToDisk, mappedtodisk, PF_NO_TAIL)
 309
 310 /* PG_readahead is only used for reads; PG_reclaim is only for writes */
 311 PAGEFLAG(Reclaim, reclaim, PF_NO_TAIL)
 312         TESTCLEARFLAG(Reclaim, reclaim, PF_NO_TAIL)
 313 PAGEFLAG(Readahead, reclaim, PF_NO_COMPOUND)
 314         TESTCLEARFLAG(Readahead, reclaim, PF_NO_COMPOUND)
 315
 316 #ifdef CONFIG_HIGHMEM
 317 /*
 318  * Must use a macro here due to header dependency issues. page_zone() is not
 319  * available at this point.
 320  */
 321 #define PageHighMem(__p) is_highmem_idx(page_zonenum(__p))
 322 #else
 323 PAGEFLAG_FALSE(HighMem)
 324 #endif
 325
 326 #ifdef CONFIG_SWAP
 327 static __always_inline int PageSwapCache(struct page *page)
 328 {
 329 #ifdef CONFIG_THP_SWAP
 330         page = compound_head(page);
 331 #endif
 332         return PageSwapBacked(page) && test_bit(PG_swapcache, &page->flags);
 333
 334 }
 335 SETPAGEFLAG(SwapCache, swapcache, PF_NO_TAIL)
 336 CLEARPAGEFLAG(SwapCache, swapcache, PF_NO_TAIL)
 337 #else
 338 PAGEFLAG_FALSE(SwapCache)
 339 #endif
 340
 341 PAGEFLAG(Unevictable, unevictable, PF_HEAD)
 342         __CLEARPAGEFLAG(Unevictable, unevictable, PF_HEAD)
 343         TESTCLEARFLAG(Unevictable, unevictable, PF_HEAD)
 344
 345 #ifdef CONFIG_MMU
 346 PAGEFLAG(Mlocked, mlocked, PF_NO_TAIL)
 347         __CLEARPAGEFLAG(Mlocked, mlocked, PF_NO_TAIL)
 348         TESTSCFLAG(Mlocked, mlocked, PF_NO_TAIL)
 349 #else
 350 PAGEFLAG_FALSE(Mlocked) __CLEARPAGEFLAG_NOOP(Mlocked)
 351         TESTSCFLAG_FALSE(Mlocked)
 352 #endif
 353
 354 #ifdef CONFIG_ARCH_USES_PG_UNCACHED
 355 PAGEFLAG(Uncached, uncached, PF_NO_COMPOUND)
 356 #else
 357 PAGEFLAG_FALSE(Uncached)
 358 #endif
 359
 360 #ifdef CONFIG_MEMORY_FAILURE
 361 PAGEFLAG(HWPoison, hwpoison, PF_ANY)
 362 TESTSCFLAG(HWPoison, hwpoison, PF_ANY)
 363 #define __PG_HWPOISON (1UL << PG_hwpoison)
 364 #else
 365 PAGEFLAG_FALSE(HWPoison)
 366 #define __PG_HWPOISON 0
 367 #endif
 368
 369 #if defined(CONFIG_IDLE_PAGE_TRACKING) && defined(CONFIG_64BIT)
 370 TESTPAGEFLAG(Young, young, PF_ANY)
 371 SETPAGEFLAG(Young, young, PF_ANY)
 372 TESTCLEARFLAG(Young, young, PF_ANY)
 373 PAGEFLAG(Idle, idle, PF_ANY)
 374 #endif
 375
 376 /*
 377  * On an anonymous page mapped into a user virtual memory area,
 378  * page->mapping points to its anon_vma, not to a struct address_space;
 379  * with the PAGE_MAPPING_ANON bit set to distinguish it.  See rmap.h.
 380  *
 381  * On an anonymous page in a VM_MERGEABLE area, if CONFIG_KSM is enabled,
 382  * the PAGE_MAPPING_MOVABLE bit may be set along with the PAGE_MAPPING_ANON
 383  * bit; and then page->mapping points, not to an anon_vma, but to a private
 384  * structure which KSM associates with that merged page.  See ksm.h.
 385  *
 386  * PAGE_MAPPING_KSM without PAGE_MAPPING_ANON is used for non-lru movable
 387  * page and then page->mapping points a struct address_space.
 388  *
 389  * Please note that, confusingly, "page_mapping" refers to the inode
 390  * address_space which maps the page from disk; whereas "page_mapped"
 391  * refers to user virtual address space into which the page is mapped.
 392  */
 393 #define PAGE_MAPPING_ANON       0x1
 394 #define PAGE_MAPPING_MOVABLE    0x2
 395 #define PAGE_MAPPING_KSM        (PAGE_MAPPING_ANON | PAGE_MAPPING_MOVABLE)
 396 #define PAGE_MAPPING_FLAGS      (PAGE_MAPPING_ANON | PAGE_MAPPING_MOVABLE)
 397
 398 static __always_inline int PageMappingFlags(struct page *page)
 399 {
 400         return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) != 0;
 401 }
 402
 403 static __always_inline int PageAnon(struct page *page)
 404 {
 405         page = compound_head(page);
 406         return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0;
 407 }
 408
 409 static __always_inline int __PageMovable(struct page *page)
 410 {
 411         return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) ==
 412                                 PAGE_MAPPING_MOVABLE;
 413 }
 414
 415 #ifdef CONFIG_KSM
 416 /*
 417  * A KSM page is one of those write-protected "shared pages" or "merged pages"
 418  * which KSM maps into multiple mms, wherever identical anonymous page content
 419  * is found in VM_MERGEABLE vmas.  It's a PageAnon page, pointing not to any
 420  * anon_vma, but to that page's node of the stable tree.
 421  */
 422 static __always_inline int PageKsm(struct page *page)
 423 {
 424         page = compound_head(page);
 425         return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) ==
 426                                 PAGE_MAPPING_KSM;
 427 }
 428 #else
 429 TESTPAGEFLAG_FALSE(Ksm)
 430 #endif
 431
 432 u64 stable_page_flags(struct page *page);
 433
 434 static inline int PageUptodate(struct page *page)
 435 {
 436         int ret;
 437         page = compound_head(page);
 438         ret = test_bit(PG_uptodate, &(page)->flags);
 439         /*
 440          * Must ensure that the data we read out of the page is loaded
 441          * _after_ we've loaded page->flags to check for PageUptodate.
 442          * We can skip the barrier if the page is not uptodate, because
 443          * we wouldn't be reading anything from it.
 444          *
 445          * See SetPageUptodate() for the other side of the story.
 446          */
 447         if (ret)
 448                 smp_rmb();
 449
 450         return ret;
 451 }
 452
 453 static __always_inline void __SetPageUptodate(struct page *page)
 454 {
 455         VM_BUG_ON_PAGE(PageTail(page), page);
 456         smp_wmb();
 457         __set_bit(PG_uptodate, &page->flags);
 458 }
 459
 460 static __always_inline void SetPageUptodate(struct page *page)
 461 {
 462         VM_BUG_ON_PAGE(PageTail(page), page);
 463         /*
 464          * Memory barrier must be issued before setting the PG_uptodate bit,
 465          * so that all previous stores issued in order to bring the page
 466          * uptodate are actually visible before PageUptodate becomes true.
 467          */
 468         smp_wmb();
 469         set_bit(PG_uptodate, &page->flags);
 470 }
 471
 472 CLEARPAGEFLAG(Uptodate, uptodate, PF_NO_TAIL)
 473
 474 int test_clear_page_writeback(struct page *page);
 475 int __test_set_page_writeback(struct page *page, bool keep_write);
 476
 477 #define test_set_page_writeback(page)                   \
 478         __test_set_page_writeback(page, false)
 479 #define test_set_page_writeback_keepwrite(page) \
 480         __test_set_page_writeback(page, true)
 481
 482 static inline void set_page_writeback(struct page *page)
 483 {
 484         test_set_page_writeback(page);
 485 }
 486
 487 static inline void set_page_writeback_keepwrite(struct page *page)
 488 {
 489         test_set_page_writeback_keepwrite(page);
 490 }
 491
 492 __PAGEFLAG(Head, head, PF_ANY) CLEARPAGEFLAG(Head, head, PF_ANY)
 493
 494 static __always_inline void set_compound_head(struct page *page, struct page *head)
 495 {
 496         WRITE_ONCE(page->compound_head, (unsigned long)head + 1);
 497 }
 498
 499 static __always_inline void clear_compound_head(struct page *page)
 500 {
 501         WRITE_ONCE(page->compound_head, 0);
 502 }
 503
 504 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 505 static inline void ClearPageCompound(struct page *page)
 506 {
 507         BUG_ON(!PageHead(page));
 508         ClearPageHead(page);
 509 }
 510 #endif
 511
 512 #define PG_head_mask ((1UL << PG_head))
 513
 514 #ifdef CONFIG_HUGETLB_PAGE
 515 int PageHuge(struct page *page);
 516 int PageHeadHuge(struct page *page);
 517 bool page_huge_active(struct page *page);
 518 #else
 519 TESTPAGEFLAG_FALSE(Huge)
 520 TESTPAGEFLAG_FALSE(HeadHuge)
 521
 522 static inline bool page_huge_active(struct page *page)
 523 {
 524         return 0;
 525 }
 526 #endif
 527
 528
 529 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 530 /*
 531  * PageHuge() only returns true for hugetlbfs pages, but not for
 532  * normal or transparent huge pages.
 533  *
 534  * PageTransHuge() returns true for both transparent huge and
 535  * hugetlbfs pages, but not normal pages. PageTransHuge() can only be
 536  * called only in the core VM paths where hugetlbfs pages can't exist.
 537  */
 538 static inline int PageTransHuge(struct page *page)
 539 {
 540         VM_BUG_ON_PAGE(PageTail(page), page);
 541         return PageHead(page);
 542 }
 543
 544 /*
 545  * PageTransCompound returns true for both transparent huge pages
 546  * and hugetlbfs pages, so it should only be called when it's known
 547  * that hugetlbfs pages aren't involved.
 548  */
 549 static inline int PageTransCompound(struct page *page)
 550 {
 551         return PageCompound(page);
 552 }
 553
 554 /*
 555  * PageTransCompoundMap is the same as PageTransCompound, but it also
 556  * guarantees the primary MMU has the entire compound page mapped
 557  * through pmd_trans_huge, which in turn guarantees the secondary MMUs
 558  * can also map the entire compound page. This allows the secondary
 559  * MMUs to call get_user_pages() only once for each compound page and
 560  * to immediately map the entire compound page with a single secondary
 561  * MMU fault. If there will be a pmd split later, the secondary MMUs
 562  * will get an update through the MMU notifier invalidation through
 563  * split_huge_pmd().
 564  *
 565  * Unlike PageTransCompound, this is safe to be called only while
 566  * split_huge_pmd() cannot run from under us, like if protected by the
 567  * MMU notifier, otherwise it may result in page->_mapcount < 0 false
 568  * positives.
 569  */
 570 static inline int PageTransCompoundMap(struct page *page)
 571 {
 572         return PageTransCompound(page) && atomic_read(&page->_mapcount) < 0;
 573 }
 574
 575 /*
 576  * PageTransTail returns true for both transparent huge pages
 577  * and hugetlbfs pages, so it should only be called when it's known
 578  * that hugetlbfs pages aren't involved.
 579  */
 580 static inline int PageTransTail(struct page *page)
 581 {
 582         return PageTail(page);
 583 }
 584
 585 /*
 586  * PageDoubleMap indicates that the compound page is mapped with PTEs as well
 587  * as PMDs.
 588  *
 589  * This is required for optimization of rmap operations for THP: we can postpone
 590  * per small page mapcount accounting (and its overhead from atomic operations)
 591  * until the first PMD split.
 592  *
 593  * For the page PageDoubleMap means ->_mapcount in all sub-pages is offset up
 594  * by one. This reference will go away with last compound_mapcount.
 595  *
 596  * See also __split_huge_pmd_locked() and page_remove_anon_compound_rmap().
 597  */
 598 static inline int PageDoubleMap(struct page *page)
 599 {
 600         return PageHead(page) && test_bit(PG_double_map, &page[1].flags);
 601 }
 602
 603 static inline void SetPageDoubleMap(struct page *page)
 604 {
 605         VM_BUG_ON_PAGE(!PageHead(page), page);
 606         set_bit(PG_double_map, &page[1].flags);
 607 }
 608
 609 static inline void ClearPageDoubleMap(struct page *page)
 610 {
 611         VM_BUG_ON_PAGE(!PageHead(page), page);
 612         clear_bit(PG_double_map, &page[1].flags);
 613 }
 614 static inline int TestSetPageDoubleMap(struct page *page)
 615 {
 616         VM_BUG_ON_PAGE(!PageHead(page), page);
 617         return test_and_set_bit(PG_double_map, &page[1].flags);
 618 }
 619
 620 static inline int TestClearPageDoubleMap(struct page *page)
 621 {
 622         VM_BUG_ON_PAGE(!PageHead(page), page);
 623         return test_and_clear_bit(PG_double_map, &page[1].flags);
 624 }
 625
 626 #else
 627 TESTPAGEFLAG_FALSE(TransHuge)
 628 TESTPAGEFLAG_FALSE(TransCompound)
 629 TESTPAGEFLAG_FALSE(TransCompoundMap)
 630 TESTPAGEFLAG_FALSE(TransTail)
 631 PAGEFLAG_FALSE(DoubleMap)
 632         TESTSETFLAG_FALSE(DoubleMap)
 633         TESTCLEARFLAG_FALSE(DoubleMap)
 634 #endif
 635
 636 /*
 637  * For pages that are never mapped to userspace, page->mapcount may be
 638  * used for storing extra information about page type. Any value used
 639  * for this purpose must be <= -2, but it's better start not too close
 640  * to -2 so that an underflow of the page_mapcount() won't be mistaken
 641  * for a special page.
 642  */
 643 #define PAGE_MAPCOUNT_OPS(uname, lname)                                 \
 644 static __always_inline int Page##uname(struct page *page)               \
 645 {                                                                       \
 646         return atomic_read(&page->_mapcount) ==                         \
 647                                 PAGE_##lname##_MAPCOUNT_VALUE;          \
 648 }                                                                       \
 649 static __always_inline void __SetPage##uname(struct page *page)         \
 650 {                                                                       \
 651         VM_BUG_ON_PAGE(atomic_read(&page->_mapcount) != -1, page);      \
 652         atomic_set(&page->_mapcount, PAGE_##lname##_MAPCOUNT_VALUE);    \
 653 }                                                                       \
 654 static __always_inline void __ClearPage##uname(struct page *page)       \
 655 {                                                                       \
 656         VM_BUG_ON_PAGE(!Page##uname(page), page);                       \
 657         atomic_set(&page->_mapcount, -1);                               \
 658 }
 659
 660 /*
 661  * PageBuddy() indicate that the page is free and in the buddy system
 662  * (see mm/page_alloc.c).
 663  */
 664 #define PAGE_BUDDY_MAPCOUNT_VALUE               (-128)
 665 PAGE_MAPCOUNT_OPS(Buddy, BUDDY)
 666
 667 /*
 668  * PageBalloon() is set on pages that are on the balloon page list
 669  * (see mm/balloon_compaction.c).
 670  */
 671 #define PAGE_BALLOON_MAPCOUNT_VALUE             (-256)
 672 PAGE_MAPCOUNT_OPS(Balloon, BALLOON)
 673
 674 /*
 675  * If kmemcg is enabled, the buddy allocator will set PageKmemcg() on
 676  * pages allocated with __GFP_ACCOUNT. It gets cleared on page free.
 677  */
 678 #define PAGE_KMEMCG_MAPCOUNT_VALUE              (-512)
 679 PAGE_MAPCOUNT_OPS(Kmemcg, KMEMCG)
 680
 681 extern bool is_free_buddy_page(struct page *page);
 682
 683 __PAGEFLAG(Isolated, isolated, PF_ANY);
 684
 685 /*
 686  * If network-based swap is enabled, sl*b must keep track of whether pages
 687  * were allocated from pfmemalloc reserves.
 688  */
 689 static inline int PageSlabPfmemalloc(struct page *page)
 690 {
 691         VM_BUG_ON_PAGE(!PageSlab(page), page);
 692         return PageActive(page);
 693 }
 694
 695 static inline void SetPageSlabPfmemalloc(struct page *page)
 696 {
 697         VM_BUG_ON_PAGE(!PageSlab(page), page);
 698         SetPageActive(page);
 699 }
 700
 701 static inline void __ClearPageSlabPfmemalloc(struct page *page)
 702 {
 703         VM_BUG_ON_PAGE(!PageSlab(page), page);
 704         __ClearPageActive(page);
 705 }
 706
 707 static inline void ClearPageSlabPfmemalloc(struct page *page)
 708 {
 709         VM_BUG_ON_PAGE(!PageSlab(page), page);
 710         ClearPageActive(page);
 711 }
 712
 713 #ifdef CONFIG_MMU
 714 #define __PG_MLOCKED            (1UL << PG_mlocked)
 715 #else
 716 #define __PG_MLOCKED            0
 717 #endif
 718
 719 /*
 720  * Flags checked when a page is freed.  Pages being freed should not have
 721  * these flags set.  It they are, there is a problem.
 722  */
 723 #define PAGE_FLAGS_CHECK_AT_FREE                                \
 724         (1UL << PG_lru          | 1UL << PG_locked      |       \
 725          1UL << PG_private      | 1UL << PG_private_2   |       \
 726          1UL << PG_writeback    | 1UL << PG_reserved    |       \
 727          1UL << PG_slab         | 1UL << PG_active      |       \
 728          1UL << PG_unevictable  | __PG_MLOCKED)
 729
 730 /*
 731  * Flags checked when a page is prepped for return by the page allocator.
 732  * Pages being prepped should not have these flags set.  It they are set,
 733  * there has been a kernel bug or struct page corruption.
 734  *
 735  * __PG_HWPOISON is exceptional because it needs to be kept beyond page's
 736  * alloc-free cycle to prevent from reusing the page.
 737  */
 738 #define PAGE_FLAGS_CHECK_AT_PREP        \
 739         (((1UL << NR_PAGEFLAGS) - 1) & ~__PG_HWPOISON)
 740
 741 #define PAGE_FLAGS_PRIVATE                              \
 742         (1UL << PG_private | 1UL << PG_private_2)
 743 /**
 744  * page_has_private - Determine if page has private stuff
 745  * @page: The page to be checked
 746  *
 747  * Determine if a page has private stuff, indicating that release routines
 748  * should be invoked upon it.
 749  */
 750 static inline int page_has_private(struct page *page)
 751 {
 752         return !!(page->flags & PAGE_FLAGS_PRIVATE);
 753 }
 754
 755 #undef PF_ANY
 756 #undef PF_HEAD
 757 #undef PF_ONLY_HEAD
 758 #undef PF_NO_TAIL
 759 #undef PF_NO_COMPOUND
 760 #endif /* !__GENERATING_BOUNDS_H */
 761
 762 #endif  /* PAGE_FLAGS_H */