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 #ifndef __GENERATING_BOUNDS_H
  10 #include <linux/mm_types.h>
  11 #include <generated/bounds.h>
  12 #endif /* !__GENERATING_BOUNDS_H */
  13
  14 /*
  15  * Various page->flags bits:
  16  *
  17  * PG_reserved is set for special pages, which can never be swapped out. Some
  18  * of them might not even exist (eg empty_bad_page)...
  19  *
  20  * The PG_private bitflag is set on pagecache pages if they contain filesystem
  21  * specific data (which is normally at page->private). It can be used by
  22  * private allocations for its own usage.
  23  *
  24  * During initiation of disk I/O, PG_locked is set. This bit is set before I/O
  25  * and cleared when writeback _starts_ or when read _completes_. PG_writeback
  26  * is set before writeback starts and cleared when it finishes.
  27  *
  28  * PG_locked also pins a page in pagecache, and blocks truncation of the file
  29  * while it is held.
  30  *
  31  * page_waitqueue(page) is a wait queue of all tasks waiting for the page
  32  * to become unlocked.
  33  *
  34  * PG_uptodate tells whether the page's contents is valid.  When a read
  35  * completes, the page becomes uptodate, unless a disk I/O error happened.
  36  *
  37  * PG_referenced, PG_reclaim are used for page reclaim for anonymous and
  38  * file-backed pagecache (see mm/vmscan.c).
  39  *
  40  * PG_error is set to indicate that an I/O error occurred on this page.
  41  *
  42  * PG_arch_1 is an architecture specific page state bit.  The generic code
  43  * guarantees that this bit is cleared for a page when it first is entered into
  44  * the page cache.
  45  *
  46  * PG_highmem pages are not permanently mapped into the kernel virtual address
  47  * space, they need to be kmapped separately for doing IO on the pages.  The
  48  * struct page (these bits with information) are always mapped into kernel
  49  * address space...
  50  *
  51  * PG_hwpoison indicates that a page got corrupted in hardware and contains
  52  * data with incorrect ECC bits that triggered a machine check. Accessing is
  53  * not safe since it may cause another machine check. Don't touch!
  54  */
  55
  56 /*
  57  * Don't use the *_dontuse flags.  Use the macros.  Otherwise you'll break
  58  * locked- and dirty-page accounting.
  59  *
  60  * The page flags field is split into two parts, the main flags area
  61  * which extends from the low bits upwards, and the fields area which
  62  * extends from the high bits downwards.
  63  *
  64  *  | FIELD | ... | FLAGS |
  65  *  N-1           ^       0
  66  *               (NR_PAGEFLAGS)
  67  *
  68  * The fields area is reserved for fields mapping zone, node (for NUMA) and
  69  * SPARSEMEM section (for variants of SPARSEMEM that require section ids like
  70  * SPARSEMEM_EXTREME with !SPARSEMEM_VMEMMAP).
  71  */
  72 enum pageflags {
  73         PG_locked,              /* Page is locked. Don't touch. */
  74         PG_error,
  75         PG_referenced,
  76         PG_uptodate,
  77         PG_dirty,
  78         PG_lru,
  79         PG_active,
  80         PG_slab,
  81         PG_owner_priv_1,        /* Owner use. If pagecache, fs may use*/
  82         PG_arch_1,
  83         PG_reserved,
  84         PG_private,             /* If pagecache, has fs-private data */
  85         PG_private_2,           /* If pagecache, has fs aux data */
  86         PG_writeback,           /* Page is under writeback */
  87 #ifdef CONFIG_PAGEFLAGS_EXTENDED
  88         PG_head,                /* A head page */
  89         PG_tail,                /* A tail page */
  90 #else
  91         PG_compound,            /* A compound page */
  92 #endif
  93         PG_swapcache,           /* Swap page: swp_entry_t in private */
  94         PG_mappedtodisk,        /* Has blocks allocated on-disk */
  95         PG_reclaim,             /* To be reclaimed asap */
  96         PG_swapbacked,          /* Page is backed by RAM/swap */
  97         PG_unevictable,         /* Page is "unevictable"  */
  98 #ifdef CONFIG_MMU
  99         PG_mlocked,             /* Page is vma mlocked */
 100 #endif
 101 #ifdef CONFIG_ARCH_USES_PG_UNCACHED
 102         PG_uncached,            /* Page has been mapped as uncached */
 103 #endif
 104 #ifdef CONFIG_MEMORY_FAILURE
 105         PG_hwpoison,            /* hardware poisoned page. Don't touch */
 106 #endif
 107 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 108         PG_compound_lock,
 109 #endif
 110         __NR_PAGEFLAGS,
 111
 112         /* Filesystems */
 113         PG_checked = PG_owner_priv_1,
 114
 115         /* Two page bits are conscripted by FS-Cache to maintain local caching
 116          * state.  These bits are set on pages belonging to the netfs's inodes
 117          * when those inodes are being locally cached.
 118          */
 119         PG_fscache = PG_private_2,      /* page backed by cache */
 120
 121         /* XEN */
 122         PG_pinned = PG_owner_priv_1,
 123         PG_savepinned = PG_dirty,
 124
 125         /* SLOB */
 126         PG_slob_free = PG_private,
 127
 128         /* SLUB */
 129         PG_slub_frozen = PG_active,
 130 };
 131
 132 #ifndef __GENERATING_BOUNDS_H
 133
 134 /*
 135  * Macros to create function definitions for page flags
 136  */
 137 #define TESTPAGEFLAG(uname, lname)                                      \
 138 static inline int Page##uname(struct page *page)                        \
 139                         { return test_bit(PG_##lname, &page->flags); }
 140
 141 #define SETPAGEFLAG(uname, lname)                                       \
 142 static inline void SetPage##uname(struct page *page)                    \
 143                         { set_bit(PG_##lname, &page->flags); }
 144
 145 #define CLEARPAGEFLAG(uname, lname)                                     \
 146 static inline void ClearPage##uname(struct page *page)                  \
 147                         { clear_bit(PG_##lname, &page->flags); }
 148
 149 #define __SETPAGEFLAG(uname, lname)                                     \
 150 static inline void __SetPage##uname(struct page *page)                  \
 151                         { __set_bit(PG_##lname, &page->flags); }
 152
 153 #define __CLEARPAGEFLAG(uname, lname)                                   \
 154 static inline void __ClearPage##uname(struct page *page)                \
 155                         { __clear_bit(PG_##lname, &page->flags); }
 156
 157 #define TESTSETFLAG(uname, lname)                                       \
 158 static inline int TestSetPage##uname(struct page *page)                 \
 159                 { return test_and_set_bit(PG_##lname, &page->flags); }
 160
 161 #define TESTCLEARFLAG(uname, lname)                                     \
 162 static inline int TestClearPage##uname(struct page *page)               \
 163                 { return test_and_clear_bit(PG_##lname, &page->flags); }
 164
 165 #define __TESTCLEARFLAG(uname, lname)                                   \
 166 static inline int __TestClearPage##uname(struct page *page)             \
 167                 { return __test_and_clear_bit(PG_##lname, &page->flags); }
 168
 169 #define PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)               \
 170         SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname)
 171
 172 #define __PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)             \
 173         __SETPAGEFLAG(uname, lname)  __CLEARPAGEFLAG(uname, lname)
 174
 175 #define PAGEFLAG_FALSE(uname)                                           \
 176 static inline int Page##uname(struct page *page)                        \
 177                         { return 0; }
 178
 179 #define TESTSCFLAG(uname, lname)                                        \
 180         TESTSETFLAG(uname, lname) TESTCLEARFLAG(uname, lname)
 181
 182 #define SETPAGEFLAG_NOOP(uname)                                         \
 183 static inline void SetPage##uname(struct page *page) {  }
 184
 185 #define CLEARPAGEFLAG_NOOP(uname)                                       \
 186 static inline void ClearPage##uname(struct page *page) {  }
 187
 188 #define __CLEARPAGEFLAG_NOOP(uname)                                     \
 189 static inline void __ClearPage##uname(struct page *page) {  }
 190
 191 #define TESTCLEARFLAG_FALSE(uname)                                      \
 192 static inline int TestClearPage##uname(struct page *page) { return 0; }
 193
 194 #define __TESTCLEARFLAG_FALSE(uname)                                    \
 195 static inline int __TestClearPage##uname(struct page *page) { return 0; }
 196
 197 struct page;    /* forward declaration */
 198
 199 TESTPAGEFLAG(Locked, locked)
 200 PAGEFLAG(Error, error) TESTCLEARFLAG(Error, error)
 201 PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(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
 213 __PAGEFLAG(SlobFree, slob_free)
 214
 215 __PAGEFLAG(SlubFrozen, slub_frozen)
 216
 217 /*
 218  * Private page markings that may be used by the filesystem that owns the page
 219  * for its own purposes.
 220  * - PG_private and PG_private_2 cause releasepage() and co to be invoked
 221  */
 222 PAGEFLAG(Private, private) __SETPAGEFLAG(Private, private)
 223         __CLEARPAGEFLAG(Private, private)
 224 PAGEFLAG(Private2, private_2) TESTSCFLAG(Private2, private_2)
 225 PAGEFLAG(OwnerPriv1, owner_priv_1) TESTCLEARFLAG(OwnerPriv1, owner_priv_1)
 226
 227 /*
 228  * Only test-and-set exist for PG_writeback.  The unconditional operators are
 229  * risky: they bypass page accounting.
 230  */
 231 TESTPAGEFLAG(Writeback, writeback) TESTSCFLAG(Writeback, writeback)
 232 PAGEFLAG(MappedToDisk, mappedtodisk)
 233
 234 /* PG_readahead is only used for file reads; PG_reclaim is only for writes */
 235 PAGEFLAG(Reclaim, reclaim) TESTCLEARFLAG(Reclaim, reclaim)
 236 PAGEFLAG(Readahead, reclaim)            /* Reminder to do async read-ahead */
 237
 238 #ifdef CONFIG_HIGHMEM
 239 /*
 240  * Must use a macro here due to header dependency issues. page_zone() is not
 241  * available at this point.
 242  */
 243 #define PageHighMem(__p) is_highmem(page_zone(__p))
 244 #else
 245 PAGEFLAG_FALSE(HighMem)
 246 #endif
 247
 248 #ifdef CONFIG_SWAP
 249 PAGEFLAG(SwapCache, swapcache)
 250 #else
 251 PAGEFLAG_FALSE(SwapCache)
 252         SETPAGEFLAG_NOOP(SwapCache) CLEARPAGEFLAG_NOOP(SwapCache)
 253 #endif
 254
 255 PAGEFLAG(Unevictable, unevictable) __CLEARPAGEFLAG(Unevictable, unevictable)
 256         TESTCLEARFLAG(Unevictable, unevictable)
 257
 258 #ifdef CONFIG_MMU
 259 PAGEFLAG(Mlocked, mlocked) __CLEARPAGEFLAG(Mlocked, mlocked)
 260         TESTSCFLAG(Mlocked, mlocked) __TESTCLEARFLAG(Mlocked, mlocked)
 261 #else
 262 PAGEFLAG_FALSE(Mlocked) SETPAGEFLAG_NOOP(Mlocked)
 263         TESTCLEARFLAG_FALSE(Mlocked) __TESTCLEARFLAG_FALSE(Mlocked)
 264 #endif
 265
 266 #ifdef CONFIG_ARCH_USES_PG_UNCACHED
 267 PAGEFLAG(Uncached, uncached)
 268 #else
 269 PAGEFLAG_FALSE(Uncached)
 270 #endif
 271
 272 #ifdef CONFIG_MEMORY_FAILURE
 273 PAGEFLAG(HWPoison, hwpoison)
 274 TESTSCFLAG(HWPoison, hwpoison)
 275 #define __PG_HWPOISON (1UL << PG_hwpoison)
 276 #else
 277 PAGEFLAG_FALSE(HWPoison)
 278 #define __PG_HWPOISON 0
 279 #endif
 280
 281 u64 stable_page_flags(struct page *page);
 282
 283 static inline int PageUptodate(struct page *page)
 284 {
 285         int ret = test_bit(PG_uptodate, &(page)->flags);
 286
 287         /*
 288          * Must ensure that the data we read out of the page is loaded
 289          * _after_ we've loaded page->flags to check for PageUptodate.
 290          * We can skip the barrier if the page is not uptodate, because
 291          * we wouldn't be reading anything from it.
 292          *
 293          * See SetPageUptodate() for the other side of the story.
 294          */
 295         if (ret)
 296                 smp_rmb();
 297
 298         return ret;
 299 }
 300
 301 static inline void __SetPageUptodate(struct page *page)
 302 {
 303         smp_wmb();
 304         __set_bit(PG_uptodate, &(page)->flags);
 305 }
 306
 307 static inline void SetPageUptodate(struct page *page)
 308 {
 309 #ifdef CONFIG_S390
 310         if (!test_and_set_bit(PG_uptodate, &page->flags))
 311                 page_clear_dirty(page, 0);
 312 #else
 313         /*
 314          * Memory barrier must be issued before setting the PG_uptodate bit,
 315          * so that all previous stores issued in order to bring the page
 316          * uptodate are actually visible before PageUptodate becomes true.
 317          *
 318          * s390 doesn't need an explicit smp_wmb here because the test and
 319          * set bit already provides full barriers.
 320          */
 321         smp_wmb();
 322         set_bit(PG_uptodate, &(page)->flags);
 323 #endif
 324 }
 325
 326 CLEARPAGEFLAG(Uptodate, uptodate)
 327
 328 extern void cancel_dirty_page(struct page *page, unsigned int account_size);
 329
 330 int test_clear_page_writeback(struct page *page);
 331 int test_set_page_writeback(struct page *page);
 332
 333 static inline void set_page_writeback(struct page *page)
 334 {
 335         test_set_page_writeback(page);
 336 }
 337
 338 #ifdef CONFIG_PAGEFLAGS_EXTENDED
 339 /*
 340  * System with lots of page flags available. This allows separate
 341  * flags for PageHead() and PageTail() checks of compound pages so that bit
 342  * tests can be used in performance sensitive paths. PageCompound is
 343  * generally not used in hot code paths.
 344  */
 345 __PAGEFLAG(Head, head) CLEARPAGEFLAG(Head, head)
 346 __PAGEFLAG(Tail, tail)
 347
 348 static inline int PageCompound(struct page *page)
 349 {
 350         return page->flags & ((1L << PG_head) | (1L << PG_tail));
 351
 352 }
 353 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 354 static inline void ClearPageCompound(struct page *page)
 355 {
 356         BUG_ON(!PageHead(page));
 357         ClearPageHead(page);
 358 }
 359 #endif
 360 #else
 361 /*
 362  * Reduce page flag use as much as possible by overlapping
 363  * compound page flags with the flags used for page cache pages. Possible
 364  * because PageCompound is always set for compound pages and not for
 365  * pages on the LRU and/or pagecache.
 366  */
 367 TESTPAGEFLAG(Compound, compound)
 368 __PAGEFLAG(Head, compound)
 369
 370 /*
 371  * PG_reclaim is used in combination with PG_compound to mark the
 372  * head and tail of a compound page. This saves one page flag
 373  * but makes it impossible to use compound pages for the page cache.
 374  * The PG_reclaim bit would have to be used for reclaim or readahead
 375  * if compound pages enter the page cache.
 376  *
 377  * PG_compound & PG_reclaim     => Tail page
 378  * PG_compound & ~PG_reclaim    => Head page
 379  */
 380 #define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))
 381
 382 static inline int PageTail(struct page *page)
 383 {
 384         return ((page->flags & PG_head_tail_mask) == PG_head_tail_mask);
 385 }
 386
 387 static inline void __SetPageTail(struct page *page)
 388 {
 389         page->flags |= PG_head_tail_mask;
 390 }
 391
 392 static inline void __ClearPageTail(struct page *page)
 393 {
 394         page->flags &= ~PG_head_tail_mask;
 395 }
 396
 397 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 398 static inline void ClearPageCompound(struct page *page)
 399 {
 400         BUG_ON((page->flags & PG_head_tail_mask) != (1 << PG_compound));
 401         clear_bit(PG_compound, &page->flags);
 402 }
 403 #endif
 404
 405 #endif /* !PAGEFLAGS_EXTENDED */
 406
 407 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 408 /*
 409  * PageHuge() only returns true for hugetlbfs pages, but not for
 410  * normal or transparent huge pages.
 411  *
 412  * PageTransHuge() returns true for both transparent huge and
 413  * hugetlbfs pages, but not normal pages. PageTransHuge() can only be
 414  * called only in the core VM paths where hugetlbfs pages can't exist.
 415  */
 416 static inline int PageTransHuge(struct page *page)
 417 {
 418         VM_BUG_ON(PageTail(page));
 419         return PageHead(page);
 420 }
 421
 422 static inline int PageTransCompound(struct page *page)
 423 {
 424         return PageCompound(page);
 425 }
 426
 427 #else
 428
 429 static inline int PageTransHuge(struct page *page)
 430 {
 431         return 0;
 432 }
 433
 434 static inline int PageTransCompound(struct page *page)
 435 {
 436         return 0;
 437 }
 438 #endif
 439
 440 #ifdef CONFIG_MMU
 441 #define __PG_MLOCKED            (1 << PG_mlocked)
 442 #else
 443 #define __PG_MLOCKED            0
 444 #endif
 445
 446 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 447 #define __PG_COMPOUND_LOCK              (1 << PG_compound_lock)
 448 #else
 449 #define __PG_COMPOUND_LOCK              0
 450 #endif
 451
 452 /*
 453  * Flags checked when a page is freed.  Pages being freed should not have
 454  * these flags set.  It they are, there is a problem.
 455  */
 456 #define PAGE_FLAGS_CHECK_AT_FREE \
 457         (1 << PG_lru     | 1 << PG_locked    | \
 458          1 << PG_private | 1 << PG_private_2 | \
 459          1 << PG_writeback | 1 << PG_reserved | \
 460          1 << PG_slab    | 1 << PG_swapcache | 1 << PG_active | \
 461          1 << PG_unevictable | __PG_MLOCKED | __PG_HWPOISON | \
 462          __PG_COMPOUND_LOCK)
 463
 464 /*
 465  * Flags checked when a page is prepped for return by the page allocator.
 466  * Pages being prepped should not have any flags set.  It they are set,
 467  * there has been a kernel bug or struct page corruption.
 468  */
 469 #define PAGE_FLAGS_CHECK_AT_PREP        ((1 << NR_PAGEFLAGS) - 1)
 470
 471 #define PAGE_FLAGS_PRIVATE                              \
 472         (1 << PG_private | 1 << PG_private_2)
 473 /**
 474  * page_has_private - Determine if page has private stuff
 475  * @page: The page to be checked
 476  *
 477  * Determine if a page has private stuff, indicating that release routines
 478  * should be invoked upon it.
 479  */
 480 static inline int page_has_private(struct page *page)
 481 {
 482         return !!(page->flags & PAGE_FLAGS_PRIVATE);
 483 }
 484
 485 #endif /* !__GENERATING_BOUNDS_H */
 486
 487 #endif  /* PAGE_FLAGS_H */