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