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 #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         __NR_PAGEFLAGS,
 113
 114         /* Filesystems */
 115         PG_checked = PG_owner_priv_1,
 116
 117         /* Two page bits are conscripted by FS-Cache to maintain local caching
 118          * state.  These bits are set on pages belonging to the netfs's inodes
 119          * when those inodes are being locally cached.
 120          */
 121         PG_fscache = PG_private_2,      /* page backed by cache */
 122
 123         /* XEN */
 124         PG_pinned = PG_owner_priv_1,
 125         PG_savepinned = PG_dirty,
 126
 127         /* SLOB */
 128         PG_slob_free = PG_private,
 129 };
 130
 131 #ifndef __GENERATING_BOUNDS_H
 132
 133 /*
 134  * Macros to create function definitions for page flags
 135  */
 136 #define TESTPAGEFLAG(uname, lname)                                      \
 137 static inline int Page##uname(const struct page *page)                  \
 138                         { return test_bit(PG_##lname, &page->flags); }
 139
 140 #define SETPAGEFLAG(uname, lname)                                       \
 141 static inline void SetPage##uname(struct page *page)                    \
 142                         { set_bit(PG_##lname, &page->flags); }
 143
 144 #define CLEARPAGEFLAG(uname, lname)                                     \
 145 static inline void ClearPage##uname(struct page *page)                  \
 146                         { clear_bit(PG_##lname, &page->flags); }
 147
 148 #define __SETPAGEFLAG(uname, lname)                                     \
 149 static inline void __SetPage##uname(struct page *page)                  \
 150                         { __set_bit(PG_##lname, &page->flags); }
 151
 152 #define __CLEARPAGEFLAG(uname, lname)                                   \
 153 static inline void __ClearPage##uname(struct page *page)                \
 154                         { __clear_bit(PG_##lname, &page->flags); }
 155
 156 #define TESTSETFLAG(uname, lname)                                       \
 157 static inline int TestSetPage##uname(struct page *page)                 \
 158                 { return test_and_set_bit(PG_##lname, &page->flags); }
 159
 160 #define TESTCLEARFLAG(uname, lname)                                     \
 161 static inline int TestClearPage##uname(struct page *page)               \
 162                 { return test_and_clear_bit(PG_##lname, &page->flags); }
 163
 164 #define __TESTCLEARFLAG(uname, lname)                                   \
 165 static inline int __TestClearPage##uname(struct page *page)             \
 166                 { return __test_and_clear_bit(PG_##lname, &page->flags); }
 167
 168 #define PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)               \
 169         SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname)
 170
 171 #define __PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)             \
 172         __SETPAGEFLAG(uname, lname)  __CLEARPAGEFLAG(uname, lname)
 173
 174 #define TESTSCFLAG(uname, lname)                                        \
 175         TESTSETFLAG(uname, lname) TESTCLEARFLAG(uname, lname)
 176
 177 #define TESTPAGEFLAG_FALSE(uname)                                       \
 178 static inline int Page##uname(const struct page *page) { return 0; }
 179
 180 #define SETPAGEFLAG_NOOP(uname)                                         \
 181 static inline void SetPage##uname(struct page *page) {  }
 182
 183 #define CLEARPAGEFLAG_NOOP(uname)                                       \
 184 static inline void ClearPage##uname(struct page *page) {  }
 185
 186 #define __CLEARPAGEFLAG_NOOP(uname)                                     \
 187 static inline void __ClearPage##uname(struct page *page) {  }
 188
 189 #define TESTSETFLAG_FALSE(uname)                                        \
 190 static inline int TestSetPage##uname(struct page *page) { return 0; }
 191
 192 #define TESTCLEARFLAG_FALSE(uname)                                      \
 193 static inline int TestClearPage##uname(struct page *page) { return 0; }
 194
 195 #define __TESTCLEARFLAG_FALSE(uname)                                    \
 196 static inline int __TestClearPage##uname(struct page *page) { return 0; }
 197
 198 #define PAGEFLAG_FALSE(uname) TESTPAGEFLAG_FALSE(uname)                 \
 199         SETPAGEFLAG_NOOP(uname) CLEARPAGEFLAG_NOOP(uname)
 200
 201 #define TESTSCFLAG_FALSE(uname)                                         \
 202         TESTSETFLAG_FALSE(uname) TESTCLEARFLAG_FALSE(uname)
 203
 204 struct page;    /* forward declaration */
 205
 206 TESTPAGEFLAG(Locked, locked)
 207 PAGEFLAG(Error, error) TESTCLEARFLAG(Error, error)
 208 PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced)
 209         __SETPAGEFLAG(Referenced, referenced)
 210 PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty, dirty)
 211 PAGEFLAG(LRU, lru) __CLEARPAGEFLAG(LRU, lru)
 212 PAGEFLAG(Active, active) __CLEARPAGEFLAG(Active, active)
 213         TESTCLEARFLAG(Active, active)
 214 __PAGEFLAG(Slab, slab)
 215 PAGEFLAG(Checked, checked)              /* Used by some filesystems */
 216 PAGEFLAG(Pinned, pinned) TESTSCFLAG(Pinned, pinned)     /* Xen */
 217 PAGEFLAG(SavePinned, savepinned);                       /* Xen */
 218 PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
 219 PAGEFLAG(SwapBacked, swapbacked) __CLEARPAGEFLAG(SwapBacked, swapbacked)
 220         __SETPAGEFLAG(SwapBacked, swapbacked)
 221
 222 __PAGEFLAG(SlobFree, slob_free)
 223
 224 /*
 225  * Private page markings that may be used by the filesystem that owns the page
 226  * for its own purposes.
 227  * - PG_private and PG_private_2 cause releasepage() and co to be invoked
 228  */
 229 PAGEFLAG(Private, private) __SETPAGEFLAG(Private, private)
 230         __CLEARPAGEFLAG(Private, private)
 231 PAGEFLAG(Private2, private_2) TESTSCFLAG(Private2, private_2)
 232 PAGEFLAG(OwnerPriv1, owner_priv_1) TESTCLEARFLAG(OwnerPriv1, owner_priv_1)
 233
 234 /*
 235  * Only test-and-set exist for PG_writeback.  The unconditional operators are
 236  * risky: they bypass page accounting.
 237  */
 238 TESTPAGEFLAG(Writeback, writeback) TESTSCFLAG(Writeback, writeback)
 239 PAGEFLAG(MappedToDisk, mappedtodisk)
 240
 241 /* PG_readahead is only used for reads; PG_reclaim is only for writes */
 242 PAGEFLAG(Reclaim, reclaim) TESTCLEARFLAG(Reclaim, reclaim)
 243 PAGEFLAG(Readahead, reclaim) TESTCLEARFLAG(Readahead, reclaim)
 244
 245 #ifdef CONFIG_HIGHMEM
 246 /*
 247  * Must use a macro here due to header dependency issues. page_zone() is not
 248  * available at this point.
 249  */
 250 #define PageHighMem(__p) is_highmem(page_zone(__p))
 251 #else
 252 PAGEFLAG_FALSE(HighMem)
 253 #endif
 254
 255 #ifdef CONFIG_SWAP
 256 PAGEFLAG(SwapCache, swapcache)
 257 #else
 258 PAGEFLAG_FALSE(SwapCache)
 259 #endif
 260
 261 PAGEFLAG(Unevictable, unevictable) __CLEARPAGEFLAG(Unevictable, unevictable)
 262         TESTCLEARFLAG(Unevictable, unevictable)
 263
 264 #ifdef CONFIG_MMU
 265 PAGEFLAG(Mlocked, mlocked) __CLEARPAGEFLAG(Mlocked, mlocked)
 266         TESTSCFLAG(Mlocked, mlocked) __TESTCLEARFLAG(Mlocked, mlocked)
 267 #else
 268 PAGEFLAG_FALSE(Mlocked) __CLEARPAGEFLAG_NOOP(Mlocked)
 269         TESTSCFLAG_FALSE(Mlocked) __TESTCLEARFLAG_FALSE(Mlocked)
 270 #endif
 271
 272 #ifdef CONFIG_ARCH_USES_PG_UNCACHED
 273 PAGEFLAG(Uncached, uncached)
 274 #else
 275 PAGEFLAG_FALSE(Uncached)
 276 #endif
 277
 278 #ifdef CONFIG_MEMORY_FAILURE
 279 PAGEFLAG(HWPoison, hwpoison)
 280 TESTSCFLAG(HWPoison, hwpoison)
 281 #define __PG_HWPOISON (1UL << PG_hwpoison)
 282 #else
 283 PAGEFLAG_FALSE(HWPoison)
 284 #define __PG_HWPOISON 0
 285 #endif
 286
 287 u64 stable_page_flags(struct page *page);
 288
 289 static inline int PageUptodate(struct page *page)
 290 {
 291         int ret = test_bit(PG_uptodate, &(page)->flags);
 292
 293         /*
 294          * Must ensure that the data we read out of the page is loaded
 295          * _after_ we've loaded page->flags to check for PageUptodate.
 296          * We can skip the barrier if the page is not uptodate, because
 297          * we wouldn't be reading anything from it.
 298          *
 299          * See SetPageUptodate() for the other side of the story.
 300          */
 301         if (ret)
 302                 smp_rmb();
 303
 304         return ret;
 305 }
 306
 307 static inline void __SetPageUptodate(struct page *page)
 308 {
 309         smp_wmb();
 310         __set_bit(PG_uptodate, &(page)->flags);
 311 }
 312
 313 static inline void SetPageUptodate(struct page *page)
 314 {
 315         /*
 316          * Memory barrier must be issued before setting the PG_uptodate bit,
 317          * so that all previous stores issued in order to bring the page
 318          * uptodate are actually visible before PageUptodate becomes true.
 319          */
 320         smp_wmb();
 321         set_bit(PG_uptodate, &(page)->flags);
 322 }
 323
 324 CLEARPAGEFLAG(Uptodate, uptodate)
 325
 326 extern void cancel_dirty_page(struct page *page, unsigned int account_size);
 327
 328 int test_clear_page_writeback(struct page *page);
 329 int __test_set_page_writeback(struct page *page, bool keep_write);
 330
 331 #define test_set_page_writeback(page)                   \
 332         __test_set_page_writeback(page, false)
 333 #define test_set_page_writeback_keepwrite(page) \
 334         __test_set_page_writeback(page, true)
 335
 336 static inline void set_page_writeback(struct page *page)
 337 {
 338         test_set_page_writeback(page);
 339 }
 340
 341 static inline void set_page_writeback_keepwrite(struct page *page)
 342 {
 343         test_set_page_writeback_keepwrite(page);
 344 }
 345
 346 #ifdef CONFIG_PAGEFLAGS_EXTENDED
 347 /*
 348  * System with lots of page flags available. This allows separate
 349  * flags for PageHead() and PageTail() checks of compound pages so that bit
 350  * tests can be used in performance sensitive paths. PageCompound is
 351  * generally not used in hot code paths except arch/powerpc/mm/init_64.c
 352  * and arch/powerpc/kvm/book3s_64_vio_hv.c which use it to detect huge pages
 353  * and avoid handling those in real mode.
 354  */
 355 __PAGEFLAG(Head, head) CLEARPAGEFLAG(Head, head)
 356 __PAGEFLAG(Tail, tail)
 357
 358 static inline int PageCompound(struct page *page)
 359 {
 360         return page->flags & ((1L << PG_head) | (1L << PG_tail));
 361
 362 }
 363 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 364 static inline void ClearPageCompound(struct page *page)
 365 {
 366         BUG_ON(!PageHead(page));
 367         ClearPageHead(page);
 368 }
 369 #endif
 370
 371 #define PG_head_mask ((1L << PG_head))
 372
 373 #else
 374 /*
 375  * Reduce page flag use as much as possible by overlapping
 376  * compound page flags with the flags used for page cache pages. Possible
 377  * because PageCompound is always set for compound pages and not for
 378  * pages on the LRU and/or pagecache.
 379  */
 380 TESTPAGEFLAG(Compound, compound)
 381 __SETPAGEFLAG(Head, compound)  __CLEARPAGEFLAG(Head, compound)
 382
 383 /*
 384  * PG_reclaim is used in combination with PG_compound to mark the
 385  * head and tail of a compound page. This saves one page flag
 386  * but makes it impossible to use compound pages for the page cache.
 387  * The PG_reclaim bit would have to be used for reclaim or readahead
 388  * if compound pages enter the page cache.
 389  *
 390  * PG_compound & PG_reclaim     => Tail page
 391  * PG_compound & ~PG_reclaim    => Head page
 392  */
 393 #define PG_head_mask ((1L << PG_compound))
 394 #define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))
 395
 396 static inline int PageHead(struct page *page)
 397 {
 398         return ((page->flags & PG_head_tail_mask) == PG_head_mask);
 399 }
 400
 401 static inline int PageTail(struct page *page)
 402 {
 403         return ((page->flags & PG_head_tail_mask) == PG_head_tail_mask);
 404 }
 405
 406 static inline void __SetPageTail(struct page *page)
 407 {
 408         page->flags |= PG_head_tail_mask;
 409 }
 410
 411 static inline void __ClearPageTail(struct page *page)
 412 {
 413         page->flags &= ~PG_head_tail_mask;
 414 }
 415
 416 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 417 static inline void ClearPageCompound(struct page *page)
 418 {
 419         BUG_ON((page->flags & PG_head_tail_mask) != (1 << PG_compound));
 420         clear_bit(PG_compound, &page->flags);
 421 }
 422 #endif
 423
 424 #endif /* !PAGEFLAGS_EXTENDED */
 425
 426 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 427 /*
 428  * PageHuge() only returns true for hugetlbfs pages, but not for
 429  * normal or transparent huge pages.
 430  *
 431  * PageTransHuge() returns true for both transparent huge and
 432  * hugetlbfs pages, but not normal pages. PageTransHuge() can only be
 433  * called only in the core VM paths where hugetlbfs pages can't exist.
 434  */
 435 static inline int PageTransHuge(struct page *page)
 436 {
 437         VM_BUG_ON_PAGE(PageTail(page), page);
 438         return PageHead(page);
 439 }
 440
 441 /*
 442  * PageTransCompound returns true for both transparent huge pages
 443  * and hugetlbfs pages, so it should only be called when it's known
 444  * that hugetlbfs pages aren't involved.
 445  */
 446 static inline int PageTransCompound(struct page *page)
 447 {
 448         return PageCompound(page);
 449 }
 450
 451 /*
 452  * PageTransTail returns true for both transparent huge pages
 453  * and hugetlbfs pages, so it should only be called when it's known
 454  * that hugetlbfs pages aren't involved.
 455  */
 456 static inline int PageTransTail(struct page *page)
 457 {
 458         return PageTail(page);
 459 }
 460
 461 #else
 462
 463 static inline int PageTransHuge(struct page *page)
 464 {
 465         return 0;
 466 }
 467
 468 static inline int PageTransCompound(struct page *page)
 469 {
 470         return 0;
 471 }
 472
 473 static inline int PageTransTail(struct page *page)
 474 {
 475         return 0;
 476 }
 477 #endif
 478
 479 /*
 480  * If network-based swap is enabled, sl*b must keep track of whether pages
 481  * were allocated from pfmemalloc reserves.
 482  */
 483 static inline int PageSlabPfmemalloc(struct page *page)
 484 {
 485         VM_BUG_ON_PAGE(!PageSlab(page), page);
 486         return PageActive(page);
 487 }
 488
 489 static inline void SetPageSlabPfmemalloc(struct page *page)
 490 {
 491         VM_BUG_ON_PAGE(!PageSlab(page), page);
 492         SetPageActive(page);
 493 }
 494
 495 static inline void __ClearPageSlabPfmemalloc(struct page *page)
 496 {
 497         VM_BUG_ON_PAGE(!PageSlab(page), page);
 498         __ClearPageActive(page);
 499 }
 500
 501 static inline void ClearPageSlabPfmemalloc(struct page *page)
 502 {
 503         VM_BUG_ON_PAGE(!PageSlab(page), page);
 504         ClearPageActive(page);
 505 }
 506
 507 #ifdef CONFIG_MMU
 508 #define __PG_MLOCKED            (1 << PG_mlocked)
 509 #else
 510 #define __PG_MLOCKED            0
 511 #endif
 512
 513 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 514 #define __PG_COMPOUND_LOCK              (1 << PG_compound_lock)
 515 #else
 516 #define __PG_COMPOUND_LOCK              0
 517 #endif
 518
 519 /*
 520  * Flags checked when a page is freed.  Pages being freed should not have
 521  * these flags set.  It they are, there is a problem.
 522  */
 523 #define PAGE_FLAGS_CHECK_AT_FREE \
 524         (1 << PG_lru     | 1 << PG_locked    | \
 525          1 << PG_private | 1 << PG_private_2 | \
 526          1 << PG_writeback | 1 << PG_reserved | \
 527          1 << PG_slab    | 1 << PG_swapcache | 1 << PG_active | \
 528          1 << PG_unevictable | __PG_MLOCKED | __PG_HWPOISON | \
 529          __PG_COMPOUND_LOCK)
 530
 531 /*
 532  * Flags checked when a page is prepped for return by the page allocator.
 533  * Pages being prepped should not have any flags set.  It they are set,
 534  * there has been a kernel bug or struct page corruption.
 535  */
 536 #define PAGE_FLAGS_CHECK_AT_PREP        ((1 << NR_PAGEFLAGS) - 1)
 537
 538 #define PAGE_FLAGS_PRIVATE                              \
 539         (1 << PG_private | 1 << PG_private_2)
 540 /**
 541  * page_has_private - Determine if page has private stuff
 542  * @page: The page to be checked
 543  *
 544  * Determine if a page has private stuff, indicating that release routines
 545  * should be invoked upon it.
 546  */
 547 static inline int page_has_private(struct page *page)
 548 {
 549         return !!(page->flags & PAGE_FLAGS_PRIVATE);
 550 }
 551
 552 #endif /* !__GENERATING_BOUNDS_H */
 553
 554 #endif  /* PAGE_FLAGS_H */