include/linux/page-flags.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  * Macros for manipulating and testing page->flags
   4  */
   5
   6 #ifndef PAGE_FLAGS_H
   7 #define PAGE_FLAGS_H
   8
   9 #include <linux/types.h>
  10 #include <linux/bug.h>
  11 #include <linux/mmdebug.h>
  12 #ifndef __GENERATING_BOUNDS_H
  13 #include <linux/mm_types.h>
  14 #include <generated/bounds.h>
  15 #endif /* !__GENERATING_BOUNDS_H */
  16
  17 /*
  18  * Various page->flags bits:
  19  *
  20  * PG_reserved is set for special pages, which can never be swapped out. Some
  21  * of them might not even exist...
  22  *
  23  * The PG_private bitflag is set on pagecache pages if they contain filesystem
  24  * specific data (which is normally at page->private). It can be used by
  25  * private allocations for its own usage.
  26  *
  27  * During initiation of disk I/O, PG_locked is set. This bit is set before I/O
  28  * and cleared when writeback _starts_ or when read _completes_. PG_writeback
  29  * is set before writeback starts and cleared when it finishes.
  30  *
  31  * PG_locked also pins a page in pagecache, and blocks truncation of the file
  32  * while it is held.
  33  *
  34  * page_waitqueue(page) is a wait queue of all tasks waiting for the page
  35  * to become unlocked.
  36  *
  37  * PG_uptodate tells whether the page's contents is valid.  When a read
  38  * completes, the page becomes uptodate, unless a disk I/O error happened.
  39  *
  40  * PG_referenced, PG_reclaim are used for page reclaim for anonymous and
  41  * file-backed pagecache (see mm/vmscan.c).
  42  *
  43  * PG_error is set to indicate that an I/O error occurred on this page.
  44  *
  45  * PG_arch_1 is an architecture specific page state bit.  The generic code
  46  * guarantees that this bit is cleared for a page when it first is entered into
  47  * the page cache.
  48  *
  49  * PG_hwpoison indicates that a page got corrupted in hardware and contains
  50  * data with incorrect ECC bits that triggered a machine check. Accessing is
  51  * not safe since it may cause another machine check. Don't touch!
  52  */
  53
  54 /*
  55  * Don't use the *_dontuse flags.  Use the macros.  Otherwise you'll break
  56  * locked- and dirty-page accounting.
  57  *
  58  * The page flags field is split into two parts, the main flags area
  59  * which extends from the low bits upwards, and the fields area which
  60  * extends from the high bits downwards.
  61  *
  62  *  | FIELD | ... | FLAGS |
  63  *  N-1           ^       0
  64  *               (NR_PAGEFLAGS)
  65  *
  66  * The fields area is reserved for fields mapping zone, node (for NUMA) and
  67  * SPARSEMEM section (for variants of SPARSEMEM that require section ids like
  68  * SPARSEMEM_EXTREME with !SPARSEMEM_VMEMMAP).
  69  */
  70 enum pageflags {
  71         PG_locked,              /* Page is locked. Don't touch. */
  72         PG_error,
  73         PG_referenced,
  74         PG_uptodate,
  75         PG_dirty,
  76         PG_lru,
  77         PG_active,
  78         PG_waiters,             /* Page has waiters, check its waitqueue. Must be bit #7 and in the same byte as "PG_locked" */
  79         PG_slab,
  80         PG_owner_priv_1,        /* Owner use. If pagecache, fs may use*/
  81         PG_arch_1,
  82         PG_reserved,
  83         PG_private,             /* If pagecache, has fs-private data */
  84         PG_private_2,           /* If pagecache, has fs aux data */
  85         PG_writeback,           /* Page is under writeback */
  86         PG_head,                /* A head page */
  87         PG_mappedtodisk,        /* Has blocks allocated on-disk */
  88         PG_reclaim,             /* To be reclaimed asap */
  89         PG_swapbacked,          /* Page is backed by RAM/swap */
  90         PG_unevictable,         /* Page is "unevictable"  */
  91 #ifdef CONFIG_MMU
  92         PG_mlocked,             /* Page is vma mlocked */
  93 #endif
  94 #ifdef CONFIG_ARCH_USES_PG_UNCACHED
  95         PG_uncached,            /* Page has been mapped as uncached */
  96 #endif
  97 #ifdef CONFIG_MEMORY_FAILURE
  98         PG_hwpoison,            /* hardware poisoned page. Don't touch */
  99 #endif
 100 #if defined(CONFIG_IDLE_PAGE_TRACKING) && defined(CONFIG_64BIT)
 101         PG_young,
 102         PG_idle,
 103 #endif
 104         __NR_PAGEFLAGS,
 105
 106         /* Filesystems */
 107         PG_checked = PG_owner_priv_1,
 108
 109         /* SwapBacked */
 110         PG_swapcache = PG_owner_priv_1, /* Swap page: swp_entry_t in private */
 111
 112         /* Two page bits are conscripted by FS-Cache to maintain local caching
 113          * state.  These bits are set on pages belonging to the netfs's inodes
 114          * when those inodes are being locally cached.
 115          */
 116         PG_fscache = PG_private_2,      /* page backed by cache */
 117
 118         /* XEN */
 119         /* Pinned in Xen as a read-only pagetable page. */
 120         PG_pinned = PG_owner_priv_1,
 121         /* Pinned as part of domain save (see xen_mm_pin_all()). */
 122         PG_savepinned = PG_dirty,
 123         /* Has a grant mapping of another (foreign) domain's page. */
 124         PG_foreign = PG_owner_priv_1,
 125
 126         /* SLOB */
 127         PG_slob_free = PG_private,
 128
 129         /* Compound pages. Stored in first tail page's flags */
 130         PG_double_map = PG_private_2,
 131
 132         /* non-lru isolated movable page */
 133         PG_isolated = PG_reclaim,
 134 };
 135
 136 #ifndef __GENERATING_BOUNDS_H
 137
 138 struct page;    /* forward declaration */
 139
 140 static inline struct page *compound_head(struct page *page)
 141 {
 142         unsigned long head = READ_ONCE(page->compound_head);
 143
 144         if (unlikely(head & 1))
 145                 return (struct page *) (head - 1);
 146         return page;
 147 }
 148
 149 static __always_inline int PageTail(struct page *page)
 150 {
 151         return READ_ONCE(page->compound_head) & 1;
 152 }
 153
 154 static __always_inline int PageCompound(struct page *page)
 155 {
 156         return test_bit(PG_head, &page->flags) || PageTail(page);
 157 }
 158
 159 /*
 160  * Page flags policies wrt compound pages
 161  *
 162  * PF_ANY:
 163  *     the page flag is relevant for small, head and tail pages.
 164  *
 165  * PF_HEAD:
 166  *     for compound page all operations related to the page flag applied to
 167  *     head page.
 168  *
 169  * PF_ONLY_HEAD:
 170  *     for compound page, callers only ever operate on the head page.
 171  *
 172  * PF_NO_TAIL:
 173  *     modifications of the page flag must be done on small or head pages,
 174  *     checks can be done on tail pages too.
 175  *
 176  * PF_NO_COMPOUND:
 177  *     the page flag is not relevant for compound pages.
 178  */
 179 #define PF_ANY(page, enforce)   page
 180 #define PF_HEAD(page, enforce)  compound_head(page)
 181 #define PF_ONLY_HEAD(page, enforce) ({                                  \
 182                 VM_BUG_ON_PGFLAGS(PageTail(page), page);                \
 183                 page;})
 184 #define PF_NO_TAIL(page, enforce) ({                                    \
 185                 VM_BUG_ON_PGFLAGS(enforce && PageTail(page), page);     \
 186                 compound_head(page);})
 187 #define PF_NO_COMPOUND(page, enforce) ({                                \
 188                 VM_BUG_ON_PGFLAGS(enforce && PageCompound(page), page); \
 189                 page;})
 190
 191 /*
 192  * Macros to create function definitions for page flags
 193  */
 194 #define TESTPAGEFLAG(uname, lname, policy)                              \
 195 static __always_inline int Page##uname(struct page *page)               \
 196         { return test_bit(PG_##lname, &policy(page, 0)->flags); }
 197
 198 #define SETPAGEFLAG(uname, lname, policy)                               \
 199 static __always_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 __always_inline void ClearPage##uname(struct page *page)         \
 204         { clear_bit(PG_##lname, &policy(page, 1)->flags); }
 205
 206 #define __SETPAGEFLAG(uname, lname, policy)                             \
 207 static __always_inline void __SetPage##uname(struct page *page)         \
 208         { __set_bit(PG_##lname, &policy(page, 1)->flags); }
 209
 210 #define __CLEARPAGEFLAG(uname, lname, policy)                           \
 211 static __always_inline void __ClearPage##uname(struct page *page)       \
 212         { __clear_bit(PG_##lname, &policy(page, 1)->flags); }
 213
 214 #define TESTSETFLAG(uname, lname, policy)                               \
 215 static __always_inline int TestSetPage##uname(struct page *page)        \
 216         { return test_and_set_bit(PG_##lname, &policy(page, 1)->flags); }
 217
 218 #define TESTCLEARFLAG(uname, lname, policy)                             \
 219 static __always_inline int TestClearPage##uname(struct page *page)      \
 220         { return test_and_clear_bit(PG_##lname, &policy(page, 1)->flags); }
 221
 222 #define PAGEFLAG(uname, lname, policy)                                  \
 223         TESTPAGEFLAG(uname, lname, policy)                              \
 224         SETPAGEFLAG(uname, lname, policy)                               \
 225         CLEARPAGEFLAG(uname, lname, policy)
 226
 227 #define __PAGEFLAG(uname, lname, policy)                                \
 228         TESTPAGEFLAG(uname, lname, policy)                              \
 229         __SETPAGEFLAG(uname, lname, policy)                             \
 230         __CLEARPAGEFLAG(uname, lname, policy)
 231
 232 #define TESTSCFLAG(uname, lname, policy)                                \
 233         TESTSETFLAG(uname, lname, policy)                               \
 234         TESTCLEARFLAG(uname, lname, policy)
 235
 236 #define TESTPAGEFLAG_FALSE(uname)                                       \
 237 static inline int Page##uname(const struct page *page) { return 0; }
 238
 239 #define SETPAGEFLAG_NOOP(uname)                                         \
 240 static inline void SetPage##uname(struct page *page) {  }
 241
 242 #define CLEARPAGEFLAG_NOOP(uname)                                       \
 243 static inline void ClearPage##uname(struct page *page) {  }
 244
 245 #define __CLEARPAGEFLAG_NOOP(uname)                                     \
 246 static inline void __ClearPage##uname(struct page *page) {  }
 247
 248 #define TESTSETFLAG_FALSE(uname)                                        \
 249 static inline int TestSetPage##uname(struct page *page) { return 0; }
 250
 251 #define TESTCLEARFLAG_FALSE(uname)                                      \
 252 static inline int TestClearPage##uname(struct page *page) { return 0; }
 253
 254 #define PAGEFLAG_FALSE(uname) TESTPAGEFLAG_FALSE(uname)                 \
 255         SETPAGEFLAG_NOOP(uname) CLEARPAGEFLAG_NOOP(uname)
 256
 257 #define TESTSCFLAG_FALSE(uname)                                         \
 258         TESTSETFLAG_FALSE(uname) TESTCLEARFLAG_FALSE(uname)
 259
 260 __PAGEFLAG(Locked, locked, PF_NO_TAIL)
 261 PAGEFLAG(Waiters, waiters, PF_ONLY_HEAD) __CLEARPAGEFLAG(Waiters, waiters, PF_ONLY_HEAD)
 262 PAGEFLAG(Error, error, PF_NO_COMPOUND) TESTCLEARFLAG(Error, error, PF_NO_COMPOUND)
 263 PAGEFLAG(Referenced, referenced, PF_HEAD)
 264         TESTCLEARFLAG(Referenced, referenced, PF_HEAD)
 265         __SETPAGEFLAG(Referenced, referenced, PF_HEAD)
 266 PAGEFLAG(Dirty, dirty, PF_HEAD) TESTSCFLAG(Dirty, dirty, PF_HEAD)
 267         __CLEARPAGEFLAG(Dirty, dirty, PF_HEAD)
 268 PAGEFLAG(LRU, lru, PF_HEAD) __CLEARPAGEFLAG(LRU, lru, PF_HEAD)
 269 PAGEFLAG(Active, active, PF_HEAD) __CLEARPAGEFLAG(Active, active, PF_HEAD)
 270         TESTCLEARFLAG(Active, active, PF_HEAD)
 271 __PAGEFLAG(Slab, slab, PF_NO_TAIL)
 272 __PAGEFLAG(SlobFree, slob_free, PF_NO_TAIL)
 273 PAGEFLAG(Checked, checked, PF_NO_COMPOUND)         /* Used by some filesystems */
 274
 275 /* Xen */
 276 PAGEFLAG(Pinned, pinned, PF_NO_COMPOUND)
 277         TESTSCFLAG(Pinned, pinned, PF_NO_COMPOUND)
 278 PAGEFLAG(SavePinned, savepinned, PF_NO_COMPOUND);
 279 PAGEFLAG(Foreign, foreign, PF_NO_COMPOUND);
 280
 281 PAGEFLAG(Reserved, reserved, PF_NO_COMPOUND)
 282         __CLEARPAGEFLAG(Reserved, reserved, PF_NO_COMPOUND)
 283 PAGEFLAG(SwapBacked, swapbacked, PF_NO_TAIL)
 284         __CLEARPAGEFLAG(SwapBacked, swapbacked, PF_NO_TAIL)
 285         __SETPAGEFLAG(SwapBacked, swapbacked, PF_NO_TAIL)
 286
 287 /*
 288  * Private page markings that may be used by the filesystem that owns the page
 289  * for its own purposes.
 290  * - PG_private and PG_private_2 cause releasepage() and co to be invoked
 291  */
 292 PAGEFLAG(Private, private, PF_ANY) __SETPAGEFLAG(Private, private, PF_ANY)
 293         __CLEARPAGEFLAG(Private, private, PF_ANY)
 294 PAGEFLAG(Private2, private_2, PF_ANY) TESTSCFLAG(Private2, private_2, PF_ANY)
 295 PAGEFLAG(OwnerPriv1, owner_priv_1, PF_ANY)
 296         TESTCLEARFLAG(OwnerPriv1, owner_priv_1, PF_ANY)
 297
 298 /*
 299  * Only test-and-set exist for PG_writeback.  The unconditional operators are
 300  * risky: they bypass page accounting.
 301  */
 302 TESTPAGEFLAG(Writeback, writeback, PF_NO_TAIL)
 303         TESTSCFLAG(Writeback, writeback, PF_NO_TAIL)
 304 PAGEFLAG(MappedToDisk, mappedtodisk, PF_NO_TAIL)
 305
 306 /* PG_readahead is only used for reads; PG_reclaim is only for writes */
 307 PAGEFLAG(Reclaim, reclaim, PF_NO_TAIL)
 308         TESTCLEARFLAG(Reclaim, reclaim, PF_NO_TAIL)
 309 PAGEFLAG(Readahead, reclaim, PF_NO_COMPOUND)
 310         TESTCLEARFLAG(Readahead, reclaim, PF_NO_COMPOUND)
 311
 312 #ifdef CONFIG_HIGHMEM
 313 /*
 314  * Must use a macro here due to header dependency issues. page_zone() is not
 315  * available at this point.
 316  */
 317 #define PageHighMem(__p) is_highmem_idx(page_zonenum(__p))
 318 #else
 319 PAGEFLAG_FALSE(HighMem)
 320 #endif
 321
 322 #ifdef CONFIG_SWAP
 323 static __always_inline int PageSwapCache(struct page *page)
 324 {
 325 #ifdef CONFIG_THP_SWAP
 326         page = compound_head(page);
 327 #endif
 328         return PageSwapBacked(page) && test_bit(PG_swapcache, &page->flags);
 329
 330 }
 331 SETPAGEFLAG(SwapCache, swapcache, PF_NO_TAIL)
 332 CLEARPAGEFLAG(SwapCache, swapcache, PF_NO_TAIL)
 333 #else
 334 PAGEFLAG_FALSE(SwapCache)
 335 #endif
 336
 337 PAGEFLAG(Unevictable, unevictable, PF_HEAD)
 338         __CLEARPAGEFLAG(Unevictable, unevictable, PF_HEAD)
 339         TESTCLEARFLAG(Unevictable, unevictable, PF_HEAD)
 340
 341 #ifdef CONFIG_MMU
 342 PAGEFLAG(Mlocked, mlocked, PF_NO_TAIL)
 343         __CLEARPAGEFLAG(Mlocked, mlocked, PF_NO_TAIL)
 344         TESTSCFLAG(Mlocked, mlocked, PF_NO_TAIL)
 345 #else
 346 PAGEFLAG_FALSE(Mlocked) __CLEARPAGEFLAG_NOOP(Mlocked)
 347         TESTSCFLAG_FALSE(Mlocked)
 348 #endif
 349
 350 #ifdef CONFIG_ARCH_USES_PG_UNCACHED
 351 PAGEFLAG(Uncached, uncached, PF_NO_COMPOUND)
 352 #else
 353 PAGEFLAG_FALSE(Uncached)
 354 #endif
 355
 356 #ifdef CONFIG_MEMORY_FAILURE
 357 PAGEFLAG(HWPoison, hwpoison, PF_ANY)
 358 TESTSCFLAG(HWPoison, hwpoison, PF_ANY)
 359 #define __PG_HWPOISON (1UL << PG_hwpoison)
 360 #else
 361 PAGEFLAG_FALSE(HWPoison)
 362 #define __PG_HWPOISON 0
 363 #endif
 364
 365 #if defined(CONFIG_IDLE_PAGE_TRACKING) && defined(CONFIG_64BIT)
 366 TESTPAGEFLAG(Young, young, PF_ANY)
 367 SETPAGEFLAG(Young, young, PF_ANY)
 368 TESTCLEARFLAG(Young, young, PF_ANY)
 369 PAGEFLAG(Idle, idle, PF_ANY)
 370 #endif
 371
 372 /*
 373  * On an anonymous page mapped into a user virtual memory area,
 374  * page->mapping points to its anon_vma, not to a struct address_space;
 375  * with the PAGE_MAPPING_ANON bit set to distinguish it.  See rmap.h.
 376  *
 377  * On an anonymous page in a VM_MERGEABLE area, if CONFIG_KSM is enabled,
 378  * the PAGE_MAPPING_MOVABLE bit may be set along with the PAGE_MAPPING_ANON
 379  * bit; and then page->mapping points, not to an anon_vma, but to a private
 380  * structure which KSM associates with that merged page.  See ksm.h.
 381  *
 382  * PAGE_MAPPING_KSM without PAGE_MAPPING_ANON is used for non-lru movable
 383  * page and then page->mapping points a struct address_space.
 384  *
 385  * Please note that, confusingly, "page_mapping" refers to the inode
 386  * address_space which maps the page from disk; whereas "page_mapped"
 387  * refers to user virtual address space into which the page is mapped.
 388  */
 389 #define PAGE_MAPPING_ANON       0x1
 390 #define PAGE_MAPPING_MOVABLE    0x2
 391 #define PAGE_MAPPING_KSM        (PAGE_MAPPING_ANON | PAGE_MAPPING_MOVABLE)
 392 #define PAGE_MAPPING_FLAGS      (PAGE_MAPPING_ANON | PAGE_MAPPING_MOVABLE)
 393
 394 static __always_inline int PageMappingFlags(struct page *page)
 395 {
 396         return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) != 0;
 397 }
 398
 399 static __always_inline int PageAnon(struct page *page)
 400 {
 401         page = compound_head(page);
 402         return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0;
 403 }
 404
 405 static __always_inline int __PageMovable(struct page *page)
 406 {
 407         return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) ==
 408                                 PAGE_MAPPING_MOVABLE;
 409 }
 410
 411 #ifdef CONFIG_KSM
 412 /*
 413  * A KSM page is one of those write-protected "shared pages" or "merged pages"
 414  * which KSM maps into multiple mms, wherever identical anonymous page content
 415  * is found in VM_MERGEABLE vmas.  It's a PageAnon page, pointing not to any
 416  * anon_vma, but to that page's node of the stable tree.
 417  */
 418 static __always_inline int PageKsm(struct page *page)
 419 {
 420         page = compound_head(page);
 421         return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) ==
 422                                 PAGE_MAPPING_KSM;
 423 }
 424 #else
 425 TESTPAGEFLAG_FALSE(Ksm)
 426 #endif
 427
 428 u64 stable_page_flags(struct page *page);
 429
 430 static inline int PageUptodate(struct page *page)
 431 {
 432         int ret;
 433         page = compound_head(page);
 434         ret = test_bit(PG_uptodate, &(page)->flags);
 435         /*
 436          * Must ensure that the data we read out of the page is loaded
 437          * _after_ we've loaded page->flags to check for PageUptodate.
 438          * We can skip the barrier if the page is not uptodate, because
 439          * we wouldn't be reading anything from it.
 440          *
 441          * See SetPageUptodate() for the other side of the story.
 442          */
 443         if (ret)
 444                 smp_rmb();
 445
 446         return ret;
 447 }
 448
 449 static __always_inline void __SetPageUptodate(struct page *page)
 450 {
 451         VM_BUG_ON_PAGE(PageTail(page), page);
 452         smp_wmb();
 453         __set_bit(PG_uptodate, &page->flags);
 454 }
 455
 456 static __always_inline void SetPageUptodate(struct page *page)
 457 {
 458         VM_BUG_ON_PAGE(PageTail(page), page);
 459         /*
 460          * Memory barrier must be issued before setting the PG_uptodate bit,
 461          * so that all previous stores issued in order to bring the page
 462          * uptodate are actually visible before PageUptodate becomes true.
 463          */
 464         smp_wmb();
 465         set_bit(PG_uptodate, &page->flags);
 466 }
 467
 468 CLEARPAGEFLAG(Uptodate, uptodate, PF_NO_TAIL)
 469
 470 int test_clear_page_writeback(struct page *page);
 471 int __test_set_page_writeback(struct page *page, bool keep_write);
 472
 473 #define test_set_page_writeback(page)                   \
 474         __test_set_page_writeback(page, false)
 475 #define test_set_page_writeback_keepwrite(page) \
 476         __test_set_page_writeback(page, true)
 477
 478 static inline void set_page_writeback(struct page *page)
 479 {
 480         test_set_page_writeback(page);
 481 }
 482
 483 static inline void set_page_writeback_keepwrite(struct page *page)
 484 {
 485         test_set_page_writeback_keepwrite(page);
 486 }
 487
 488 __PAGEFLAG(Head, head, PF_ANY) CLEARPAGEFLAG(Head, head, PF_ANY)
 489
 490 static __always_inline void set_compound_head(struct page *page, struct page *head)
 491 {
 492         WRITE_ONCE(page->compound_head, (unsigned long)head + 1);
 493 }
 494
 495 static __always_inline void clear_compound_head(struct page *page)
 496 {
 497         WRITE_ONCE(page->compound_head, 0);
 498 }
 499
 500 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 501 static inline void ClearPageCompound(struct page *page)
 502 {
 503         BUG_ON(!PageHead(page));
 504         ClearPageHead(page);
 505 }
 506 #endif
 507
 508 #define PG_head_mask ((1UL << PG_head))
 509
 510 #ifdef CONFIG_HUGETLB_PAGE
 511 int PageHuge(struct page *page);
 512 int PageHeadHuge(struct page *page);
 513 bool page_huge_active(struct page *page);
 514 #else
 515 TESTPAGEFLAG_FALSE(Huge)
 516 TESTPAGEFLAG_FALSE(HeadHuge)
 517
 518 static inline bool page_huge_active(struct page *page)
 519 {
 520         return 0;
 521 }
 522 #endif
 523
 524
 525 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 526 /*
 527  * PageHuge() only returns true for hugetlbfs pages, but not for
 528  * normal or transparent huge pages.
 529  *
 530  * PageTransHuge() returns true for both transparent huge and
 531  * hugetlbfs pages, but not normal pages. PageTransHuge() can only be
 532  * called only in the core VM paths where hugetlbfs pages can't exist.
 533  */
 534 static inline int PageTransHuge(struct page *page)
 535 {
 536         VM_BUG_ON_PAGE(PageTail(page), page);
 537         return PageHead(page);
 538 }
 539
 540 /*
 541  * PageTransCompound returns true for both transparent huge pages
 542  * and hugetlbfs pages, so it should only be called when it's known
 543  * that hugetlbfs pages aren't involved.
 544  */
 545 static inline int PageTransCompound(struct page *page)
 546 {
 547         return PageCompound(page);
 548 }
 549
 550 /*
 551  * PageTransCompoundMap is the same as PageTransCompound, but it also
 552  * guarantees the primary MMU has the entire compound page mapped
 553  * through pmd_trans_huge, which in turn guarantees the secondary MMUs
 554  * can also map the entire compound page. This allows the secondary
 555  * MMUs to call get_user_pages() only once for each compound page and
 556  * to immediately map the entire compound page with a single secondary
 557  * MMU fault. If there will be a pmd split later, the secondary MMUs
 558  * will get an update through the MMU notifier invalidation through
 559  * split_huge_pmd().
 560  *
 561  * Unlike PageTransCompound, this is safe to be called only while
 562  * split_huge_pmd() cannot run from under us, like if protected by the
 563  * MMU notifier, otherwise it may result in page->_mapcount < 0 false
 564  * positives.
 565  */
 566 static inline int PageTransCompoundMap(struct page *page)
 567 {
 568         return PageTransCompound(page) && atomic_read(&page->_mapcount) < 0;
 569 }
 570
 571 /*
 572  * PageTransTail returns true for both transparent huge pages
 573  * and hugetlbfs pages, so it should only be called when it's known
 574  * that hugetlbfs pages aren't involved.
 575  */
 576 static inline int PageTransTail(struct page *page)
 577 {
 578         return PageTail(page);
 579 }
 580
 581 /*
 582  * PageDoubleMap indicates that the compound page is mapped with PTEs as well
 583  * as PMDs.
 584  *
 585  * This is required for optimization of rmap operations for THP: we can postpone
 586  * per small page mapcount accounting (and its overhead from atomic operations)
 587  * until the first PMD split.
 588  *
 589  * For the page PageDoubleMap means ->_mapcount in all sub-pages is offset up
 590  * by one. This reference will go away with last compound_mapcount.
 591  *
 592  * See also __split_huge_pmd_locked() and page_remove_anon_compound_rmap().
 593  */
 594 static inline int PageDoubleMap(struct page *page)
 595 {
 596         return PageHead(page) && test_bit(PG_double_map, &page[1].flags);
 597 }
 598
 599 static inline void SetPageDoubleMap(struct page *page)
 600 {
 601         VM_BUG_ON_PAGE(!PageHead(page), page);
 602         set_bit(PG_double_map, &page[1].flags);
 603 }
 604
 605 static inline void ClearPageDoubleMap(struct page *page)
 606 {
 607         VM_BUG_ON_PAGE(!PageHead(page), page);
 608         clear_bit(PG_double_map, &page[1].flags);
 609 }
 610 static inline int TestSetPageDoubleMap(struct page *page)
 611 {
 612         VM_BUG_ON_PAGE(!PageHead(page), page);
 613         return test_and_set_bit(PG_double_map, &page[1].flags);
 614 }
 615
 616 static inline int TestClearPageDoubleMap(struct page *page)
 617 {
 618         VM_BUG_ON_PAGE(!PageHead(page), page);
 619         return test_and_clear_bit(PG_double_map, &page[1].flags);
 620 }
 621
 622 #else
 623 TESTPAGEFLAG_FALSE(TransHuge)
 624 TESTPAGEFLAG_FALSE(TransCompound)
 625 TESTPAGEFLAG_FALSE(TransCompoundMap)
 626 TESTPAGEFLAG_FALSE(TransTail)
 627 PAGEFLAG_FALSE(DoubleMap)
 628         TESTSETFLAG_FALSE(DoubleMap)
 629         TESTCLEARFLAG_FALSE(DoubleMap)
 630 #endif
 631
 632 /*
 633  * For pages that are never mapped to userspace, page->mapcount may be
 634  * used for storing extra information about page type. Any value used
 635  * for this purpose must be <= -2, but it's better start not too close
 636  * to -2 so that an underflow of the page_mapcount() won't be mistaken
 637  * for a special page.
 638  */
 639 #define PAGE_MAPCOUNT_OPS(uname, lname)                                 \
 640 static __always_inline int Page##uname(struct page *page)               \
 641 {                                                                       \
 642         return atomic_read(&page->_mapcount) ==                         \
 643                                 PAGE_##lname##_MAPCOUNT_VALUE;          \
 644 }                                                                       \
 645 static __always_inline void __SetPage##uname(struct page *page)         \
 646 {                                                                       \
 647         VM_BUG_ON_PAGE(atomic_read(&page->_mapcount) != -1, page);      \
 648         atomic_set(&page->_mapcount, PAGE_##lname##_MAPCOUNT_VALUE);    \
 649 }                                                                       \
 650 static __always_inline void __ClearPage##uname(struct page *page)       \
 651 {                                                                       \
 652         VM_BUG_ON_PAGE(!Page##uname(page), page);                       \
 653         atomic_set(&page->_mapcount, -1);                               \
 654 }
 655
 656 /*
 657  * PageBuddy() indicate that the page is free and in the buddy system
 658  * (see mm/page_alloc.c).
 659  */
 660 #define PAGE_BUDDY_MAPCOUNT_VALUE               (-128)
 661 PAGE_MAPCOUNT_OPS(Buddy, BUDDY)
 662
 663 /*
 664  * PageBalloon() is set on pages that are on the balloon page list
 665  * (see mm/balloon_compaction.c).
 666  */
 667 #define PAGE_BALLOON_MAPCOUNT_VALUE             (-256)
 668 PAGE_MAPCOUNT_OPS(Balloon, BALLOON)
 669
 670 /*
 671  * If kmemcg is enabled, the buddy allocator will set PageKmemcg() on
 672  * pages allocated with __GFP_ACCOUNT. It gets cleared on page free.
 673  */
 674 #define PAGE_KMEMCG_MAPCOUNT_VALUE              (-512)
 675 PAGE_MAPCOUNT_OPS(Kmemcg, KMEMCG)
 676
 677 extern bool is_free_buddy_page(struct page *page);
 678
 679 __PAGEFLAG(Isolated, isolated, PF_ANY);
 680
 681 /*
 682  * If network-based swap is enabled, sl*b must keep track of whether pages
 683  * were allocated from pfmemalloc reserves.
 684  */
 685 static inline int PageSlabPfmemalloc(struct page *page)
 686 {
 687         VM_BUG_ON_PAGE(!PageSlab(page), page);
 688         return PageActive(page);
 689 }
 690
 691 static inline void SetPageSlabPfmemalloc(struct page *page)
 692 {
 693         VM_BUG_ON_PAGE(!PageSlab(page), page);
 694         SetPageActive(page);
 695 }
 696
 697 static inline void __ClearPageSlabPfmemalloc(struct page *page)
 698 {
 699         VM_BUG_ON_PAGE(!PageSlab(page), page);
 700         __ClearPageActive(page);
 701 }
 702
 703 static inline void ClearPageSlabPfmemalloc(struct page *page)
 704 {
 705         VM_BUG_ON_PAGE(!PageSlab(page), page);
 706         ClearPageActive(page);
 707 }
 708
 709 #ifdef CONFIG_MMU
 710 #define __PG_MLOCKED            (1UL << PG_mlocked)
 711 #else
 712 #define __PG_MLOCKED            0
 713 #endif
 714
 715 /*
 716  * Flags checked when a page is freed.  Pages being freed should not have
 717  * these flags set.  It they are, there is a problem.
 718  */
 719 #define PAGE_FLAGS_CHECK_AT_FREE                                \
 720         (1UL << PG_lru          | 1UL << PG_locked      |       \
 721          1UL << PG_private      | 1UL << PG_private_2   |       \
 722          1UL << PG_writeback    | 1UL << PG_reserved    |       \
 723          1UL << PG_slab         | 1UL << PG_active      |       \
 724          1UL << PG_unevictable  | __PG_MLOCKED)
 725
 726 /*
 727  * Flags checked when a page is prepped for return by the page allocator.
 728  * Pages being prepped should not have these flags set.  It they are set,
 729  * there has been a kernel bug or struct page corruption.
 730  *
 731  * __PG_HWPOISON is exceptional because it needs to be kept beyond page's
 732  * alloc-free cycle to prevent from reusing the page.
 733  */
 734 #define PAGE_FLAGS_CHECK_AT_PREP        \
 735         (((1UL << NR_PAGEFLAGS) - 1) & ~__PG_HWPOISON)
 736
 737 #define PAGE_FLAGS_PRIVATE                              \
 738         (1UL << PG_private | 1UL << PG_private_2)
 739 /**
 740  * page_has_private - Determine if page has private stuff
 741  * @page: The page to be checked
 742  *
 743  * Determine if a page has private stuff, indicating that release routines
 744  * should be invoked upon it.
 745  */
 746 static inline int page_has_private(struct page *page)
 747 {
 748         return !!(page->flags & PAGE_FLAGS_PRIVATE);
 749 }
 750
 751 #undef PF_ANY
 752 #undef PF_HEAD
 753 #undef PF_ONLY_HEAD
 754 #undef PF_NO_TAIL
 755 #undef PF_NO_COMPOUND
 756 #endif /* !__GENERATING_BOUNDS_H */
 757
 758 #endif  /* PAGE_FLAGS_H */