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_buddy is set to indicate that the page is free and in the buddy system
  52  * (see mm/page_alloc.c).
  53  *
  54  * PG_hwpoison indicates that a page got corrupted in hardware and contains
  55  * data with incorrect ECC bits that triggered a machine check. Accessing is
  56  * not safe since it may cause another machine check. Don't touch!
  57  */
  58
  59 /*
  60  * Don't use the *_dontuse flags.  Use the macros.  Otherwise you'll break
  61  * locked- and dirty-page accounting.
  62  *
  63  * The page flags field is split into two parts, the main flags area
  64  * which extends from the low bits upwards, and the fields area which
  65  * extends from the high bits downwards.
  66  *
  67  *  | FIELD | ... | FLAGS |
  68  *  N-1           ^       0
  69  *               (NR_PAGEFLAGS)
  70  *
  71  * The fields area is reserved for fields mapping zone, node (for NUMA) and
  72  * SPARSEMEM section (for variants of SPARSEMEM that require section ids like
  73  * SPARSEMEM_EXTREME with !SPARSEMEM_VMEMMAP).
  74  */
  75 enum pageflags {
  76         PG_locked,              /* Page is locked. Don't touch. */
  77         PG_error,
  78         PG_referenced,
  79         PG_uptodate,
  80         PG_dirty,
  81         PG_lru,
  82         PG_active,
  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 #ifdef CONFIG_PAGEFLAGS_EXTENDED
  91         PG_head,                /* A head page */
  92         PG_tail,                /* A tail page */
  93 #else
  94         PG_compound,            /* A compound page */
  95 #endif
  96         PG_swapcache,           /* Swap page: swp_entry_t in private */
  97         PG_mappedtodisk,        /* Has blocks allocated on-disk */
  98         PG_reclaim,             /* To be reclaimed asap */
  99         PG_buddy,               /* Page is free, on buddy lists */
 100         PG_swapbacked,          /* Page is backed by RAM/swap */
 101         PG_unevictable,         /* Page is "unevictable"  */
 102 #ifdef CONFIG_MMU
 103         PG_mlocked,             /* Page is vma mlocked */
 104 #endif
 105 #ifdef CONFIG_ARCH_USES_PG_UNCACHED
 106         PG_uncached,            /* Page has been mapped as uncached */
 107 #endif
 108 #ifdef CONFIG_MEMORY_FAILURE
 109         PG_hwpoison,            /* hardware poisoned page. Don't touch */
 110 #endif
 111 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 112         PG_compound_lock,
 113 #endif
 114         __NR_PAGEFLAGS,
 115
 116         /* Filesystems */
 117         PG_checked = PG_owner_priv_1,
 118
 119         /* Two page bits are conscripted by FS-Cache to maintain local caching
 120          * state.  These bits are set on pages belonging to the netfs's inodes
 121          * when those inodes are being locally cached.
 122          */
 123         PG_fscache = PG_private_2,      /* page backed by cache */
 124
 125         /* XEN */
 126         PG_pinned = PG_owner_priv_1,
 127         PG_savepinned = PG_dirty,
 128
 129         /* SLOB */
 130         PG_slob_free = PG_private,
 131
 132         /* SLUB */
 133         PG_slub_frozen = PG_active,
 134 };
 135
 136 #ifndef __GENERATING_BOUNDS_H
 137
 138 /*
 139  * Macros to create function definitions for page flags
 140  */
 141 #define TESTPAGEFLAG(uname, lname)                                      \
 142 static inline int Page##uname(struct page *page)                        \
 143                         { return test_bit(PG_##lname, &page->flags); }
 144
 145 #define SETPAGEFLAG(uname, lname)                                       \
 146 static inline void SetPage##uname(struct page *page)                    \
 147                         { set_bit(PG_##lname, &page->flags); }
 148
 149 #define CLEARPAGEFLAG(uname, lname)                                     \
 150 static inline void ClearPage##uname(struct page *page)                  \
 151                         { clear_bit(PG_##lname, &page->flags); }
 152
 153 #define __SETPAGEFLAG(uname, lname)                                     \
 154 static inline void __SetPage##uname(struct page *page)                  \
 155                         { __set_bit(PG_##lname, &page->flags); }
 156
 157 #define __CLEARPAGEFLAG(uname, lname)                                   \
 158 static inline void __ClearPage##uname(struct page *page)                \
 159                         { __clear_bit(PG_##lname, &page->flags); }
 160
 161 #define TESTSETFLAG(uname, lname)                                       \
 162 static inline int TestSetPage##uname(struct page *page)                 \
 163                 { return test_and_set_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 __TESTCLEARFLAG(uname, lname)                                   \
 170 static inline int __TestClearPage##uname(struct page *page)             \
 171                 { return __test_and_clear_bit(PG_##lname, &page->flags); }
 172
 173 #define PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)               \
 174         SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname)
 175
 176 #define __PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)             \
 177         __SETPAGEFLAG(uname, lname)  __CLEARPAGEFLAG(uname, lname)
 178
 179 #define PAGEFLAG_FALSE(uname)                                           \
 180 static inline int Page##uname(struct page *page)                        \
 181                         { return 0; }
 182
 183 #define TESTSCFLAG(uname, lname)                                        \
 184         TESTSETFLAG(uname, lname) TESTCLEARFLAG(uname, lname)
 185
 186 #define SETPAGEFLAG_NOOP(uname)                                         \
 187 static inline void SetPage##uname(struct page *page) {  }
 188
 189 #define CLEARPAGEFLAG_NOOP(uname)                                       \
 190 static inline void ClearPage##uname(struct page *page) {  }
 191
 192 #define __CLEARPAGEFLAG_NOOP(uname)                                     \
 193 static inline void __ClearPage##uname(struct page *page) {  }
 194
 195 #define TESTCLEARFLAG_FALSE(uname)                                      \
 196 static inline int TestClearPage##uname(struct page *page) { return 0; }
 197
 198 #define __TESTCLEARFLAG_FALSE(uname)                                    \
 199 static inline int __TestClearPage##uname(struct page *page) { return 0; }
 200
 201 struct page;    /* forward declaration */
 202
 203 TESTPAGEFLAG(Locked, locked) TESTSETFLAG(Locked, locked)
 204 PAGEFLAG(Error, error) TESTCLEARFLAG(Error, error)
 205 PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced)
 206 PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty, dirty)
 207 PAGEFLAG(LRU, lru) __CLEARPAGEFLAG(LRU, lru)
 208 PAGEFLAG(Active, active) __CLEARPAGEFLAG(Active, active)
 209         TESTCLEARFLAG(Active, active)
 210 __PAGEFLAG(Slab, slab)
 211 PAGEFLAG(Checked, checked)              /* Used by some filesystems */
 212 PAGEFLAG(Pinned, pinned) TESTSCFLAG(Pinned, pinned)     /* Xen */
 213 PAGEFLAG(SavePinned, savepinned);                       /* Xen */
 214 PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
 215 PAGEFLAG(SwapBacked, swapbacked) __CLEARPAGEFLAG(SwapBacked, swapbacked)
 216
 217 __PAGEFLAG(SlobFree, slob_free)
 218
 219 __PAGEFLAG(SlubFrozen, slub_frozen)
 220
 221 /*
 222  * Private page markings that may be used by the filesystem that owns the page
 223  * for its own purposes.
 224  * - PG_private and PG_private_2 cause releasepage() and co to be invoked
 225  */
 226 PAGEFLAG(Private, private) __SETPAGEFLAG(Private, private)
 227         __CLEARPAGEFLAG(Private, private)
 228 PAGEFLAG(Private2, private_2) TESTSCFLAG(Private2, private_2)
 229 PAGEFLAG(OwnerPriv1, owner_priv_1) TESTCLEARFLAG(OwnerPriv1, owner_priv_1)
 230
 231 /*
 232  * Only test-and-set exist for PG_writeback.  The unconditional operators are
 233  * risky: they bypass page accounting.
 234  */
 235 TESTPAGEFLAG(Writeback, writeback) TESTSCFLAG(Writeback, writeback)
 236 __PAGEFLAG(Buddy, buddy)
 237 PAGEFLAG(MappedToDisk, mappedtodisk)
 238
 239 /* PG_readahead is only used for file reads; PG_reclaim is only for writes */
 240 PAGEFLAG(Reclaim, reclaim) TESTCLEARFLAG(Reclaim, reclaim)
 241 PAGEFLAG(Readahead, reclaim)            /* Reminder to do async read-ahead */
 242
 243 #ifdef CONFIG_HIGHMEM
 244 /*
 245  * Must use a macro here due to header dependency issues. page_zone() is not
 246  * available at this point.
 247  */
 248 #define PageHighMem(__p) is_highmem(page_zone(__p))
 249 #else
 250 PAGEFLAG_FALSE(HighMem)
 251 #endif
 252
 253 #ifdef CONFIG_SWAP
 254 PAGEFLAG(SwapCache, swapcache)
 255 #else
 256 PAGEFLAG_FALSE(SwapCache)
 257         SETPAGEFLAG_NOOP(SwapCache) CLEARPAGEFLAG_NOOP(SwapCache)
 258 #endif
 259
 260 PAGEFLAG(Unevictable, unevictable) __CLEARPAGEFLAG(Unevictable, unevictable)
 261         TESTCLEARFLAG(Unevictable, unevictable)
 262
 263 #ifdef CONFIG_MMU
 264 PAGEFLAG(Mlocked, mlocked) __CLEARPAGEFLAG(Mlocked, mlocked)
 265         TESTSCFLAG(Mlocked, mlocked) __TESTCLEARFLAG(Mlocked, mlocked)
 266 #else
 267 PAGEFLAG_FALSE(Mlocked) SETPAGEFLAG_NOOP(Mlocked)
 268         TESTCLEARFLAG_FALSE(Mlocked) __TESTCLEARFLAG_FALSE(Mlocked)
 269 #endif
 270
 271 #ifdef CONFIG_ARCH_USES_PG_UNCACHED
 272 PAGEFLAG(Uncached, uncached)
 273 #else
 274 PAGEFLAG_FALSE(Uncached)
 275 #endif
 276
 277 #ifdef CONFIG_MEMORY_FAILURE
 278 PAGEFLAG(HWPoison, hwpoison)
 279 TESTSCFLAG(HWPoison, hwpoison)
 280 #define __PG_HWPOISON (1UL << PG_hwpoison)
 281 #else
 282 PAGEFLAG_FALSE(HWPoison)
 283 #define __PG_HWPOISON 0
 284 #endif
 285
 286 u64 stable_page_flags(struct page *page);
 287
 288 static inline int PageUptodate(struct page *page)
 289 {
 290         int ret = test_bit(PG_uptodate, &(page)->flags);
 291
 292         /*
 293          * Must ensure that the data we read out of the page is loaded
 294          * _after_ we've loaded page->flags to check for PageUptodate.
 295          * We can skip the barrier if the page is not uptodate, because
 296          * we wouldn't be reading anything from it.
 297          *
 298          * See SetPageUptodate() for the other side of the story.
 299          */
 300         if (ret)
 301                 smp_rmb();
 302
 303         return ret;
 304 }
 305
 306 static inline void __SetPageUptodate(struct page *page)
 307 {
 308         smp_wmb();
 309         __set_bit(PG_uptodate, &(page)->flags);
 310 }
 311
 312 static inline void SetPageUptodate(struct page *page)
 313 {
 314 #ifdef CONFIG_S390
 315         if (!test_and_set_bit(PG_uptodate, &page->flags))
 316                 page_clear_dirty(page, 0);
 317 #else
 318         /*
 319          * Memory barrier must be issued before setting the PG_uptodate bit,
 320          * so that all previous stores issued in order to bring the page
 321          * uptodate are actually visible before PageUptodate becomes true.
 322          *
 323          * s390 doesn't need an explicit smp_wmb here because the test and
 324          * set bit already provides full barriers.
 325          */
 326         smp_wmb();
 327         set_bit(PG_uptodate, &(page)->flags);
 328 #endif
 329 }
 330
 331 CLEARPAGEFLAG(Uptodate, uptodate)
 332
 333 extern void cancel_dirty_page(struct page *page, unsigned int account_size);
 334
 335 int test_clear_page_writeback(struct page *page);
 336 int test_set_page_writeback(struct page *page);
 337
 338 static inline void set_page_writeback(struct page *page)
 339 {
 340         test_set_page_writeback(page);
 341 }
 342
 343 #ifdef CONFIG_PAGEFLAGS_EXTENDED
 344 /*
 345  * System with lots of page flags available. This allows separate
 346  * flags for PageHead() and PageTail() checks of compound pages so that bit
 347  * tests can be used in performance sensitive paths. PageCompound is
 348  * generally not used in hot code paths.
 349  */
 350 __PAGEFLAG(Head, head) CLEARPAGEFLAG(Head, head)
 351 __PAGEFLAG(Tail, tail)
 352
 353 static inline int PageCompound(struct page *page)
 354 {
 355         return page->flags & ((1L << PG_head) | (1L << PG_tail));
 356
 357 }
 358 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 359 static inline void ClearPageCompound(struct page *page)
 360 {
 361         BUG_ON(!PageHead(page));
 362         ClearPageHead(page);
 363 }
 364 #endif
 365 #else
 366 /*
 367  * Reduce page flag use as much as possible by overlapping
 368  * compound page flags with the flags used for page cache pages. Possible
 369  * because PageCompound is always set for compound pages and not for
 370  * pages on the LRU and/or pagecache.
 371  */
 372 TESTPAGEFLAG(Compound, compound)
 373 __PAGEFLAG(Head, compound)
 374
 375 /*
 376  * PG_reclaim is used in combination with PG_compound to mark the
 377  * head and tail of a compound page. This saves one page flag
 378  * but makes it impossible to use compound pages for the page cache.
 379  * The PG_reclaim bit would have to be used for reclaim or readahead
 380  * if compound pages enter the page cache.
 381  *
 382  * PG_compound & PG_reclaim     => Tail page
 383  * PG_compound & ~PG_reclaim    => Head page
 384  */
 385 #define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))
 386
 387 static inline int PageTail(struct page *page)
 388 {
 389         return ((page->flags & PG_head_tail_mask) == PG_head_tail_mask);
 390 }
 391
 392 static inline void __SetPageTail(struct page *page)
 393 {
 394         page->flags |= PG_head_tail_mask;
 395 }
 396
 397 static inline void __ClearPageTail(struct page *page)
 398 {
 399         page->flags &= ~PG_head_tail_mask;
 400 }
 401
 402 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 403 static inline void ClearPageCompound(struct page *page)
 404 {
 405         BUG_ON((page->flags & PG_head_tail_mask) != (1 << PG_compound));
 406         clear_bit(PG_compound, &page->flags);
 407 }
 408 #endif
 409
 410 #endif /* !PAGEFLAGS_EXTENDED */
 411
 412 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 413 /*
 414  * PageHuge() only returns true for hugetlbfs pages, but not for
 415  * normal or transparent huge pages.
 416  *
 417  * PageTransHuge() returns true for both transparent huge and
 418  * hugetlbfs pages, but not normal pages. PageTransHuge() can only be
 419  * called only in the core VM paths where hugetlbfs pages can't exist.
 420  */
 421 static inline int PageTransHuge(struct page *page)
 422 {
 423         VM_BUG_ON(PageTail(page));
 424         return PageHead(page);
 425 }
 426
 427 static inline int PageTransCompound(struct page *page)
 428 {
 429         return PageCompound(page);
 430 }
 431
 432 #else
 433
 434 static inline int PageTransHuge(struct page *page)
 435 {
 436         return 0;
 437 }
 438
 439 static inline int PageTransCompound(struct page *page)
 440 {
 441         return 0;
 442 }
 443 #endif
 444
 445 #ifdef CONFIG_MMU
 446 #define __PG_MLOCKED            (1 << PG_mlocked)
 447 #else
 448 #define __PG_MLOCKED            0
 449 #endif
 450
 451 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 452 #define __PG_COMPOUND_LOCK              (1 << PG_compound_lock)
 453 #else
 454 #define __PG_COMPOUND_LOCK              0
 455 #endif
 456
 457 /*
 458  * Flags checked when a page is freed.  Pages being freed should not have
 459  * these flags set.  It they are, there is a problem.
 460  */
 461 #define PAGE_FLAGS_CHECK_AT_FREE \
 462         (1 << PG_lru     | 1 << PG_locked    | \
 463          1 << PG_private | 1 << PG_private_2 | \
 464          1 << PG_buddy   | 1 << PG_writeback | 1 << PG_reserved | \
 465          1 << PG_slab    | 1 << PG_swapcache | 1 << PG_active | \
 466          1 << PG_unevictable | __PG_MLOCKED | __PG_HWPOISON | \
 467          __PG_COMPOUND_LOCK)
 468
 469 /*
 470  * Flags checked when a page is prepped for return by the page allocator.
 471  * Pages being prepped should not have any flags set.  It they are set,
 472  * there has been a kernel bug or struct page corruption.
 473  */
 474 #define PAGE_FLAGS_CHECK_AT_PREP        ((1 << NR_PAGEFLAGS) - 1)
 475
 476 #define PAGE_FLAGS_PRIVATE                              \
 477         (1 << PG_private | 1 << PG_private_2)
 478 /**
 479  * page_has_private - Determine if page has private stuff
 480  * @page: The page to be checked
 481  *
 482  * Determine if a page has private stuff, indicating that release routines
 483  * should be invoked upon it.
 484  */
 485 static inline int page_has_private(struct page *page)
 486 {
 487         return !!(page->flags & PAGE_FLAGS_PRIVATE);
 488 }
 489
 490 #endif /* !__GENERATING_BOUNDS_H */
 491
 492 #endif  /* PAGE_FLAGS_H */