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 <linux/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_HAVE_MLOCKED_PAGE_BIT
 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         __NR_PAGEFLAGS,
 112
 113         /* Filesystems */
 114         PG_checked = PG_owner_priv_1,
 115
 116         /* Two page bits are conscripted by FS-Cache to maintain local caching
 117          * state.  These bits are set on pages belonging to the netfs's inodes
 118          * when those inodes are being locally cached.
 119          */
 120         PG_fscache = PG_private_2,      /* page backed by cache */
 121
 122         /* XEN */
 123         PG_pinned = PG_owner_priv_1,
 124         PG_savepinned = PG_dirty,
 125
 126         /* SLOB */
 127         PG_slob_free = PG_private,
 128
 129         /* SLUB */
 130         PG_slub_frozen = PG_active,
 131         PG_slub_debug = PG_error,
 132 };
 133
 134 #ifndef __GENERATING_BOUNDS_H
 135
 136 /*
 137  * Macros to create function definitions for page flags
 138  */
 139 #define TESTPAGEFLAG(uname, lname)                                      \
 140 static inline int Page##uname(struct page *page)                        \
 141                         { return test_bit(PG_##lname, &page->flags); }
 142
 143 #define SETPAGEFLAG(uname, lname)                                       \
 144 static inline void SetPage##uname(struct page *page)                    \
 145                         { set_bit(PG_##lname, &page->flags); }
 146
 147 #define CLEARPAGEFLAG(uname, lname)                                     \
 148 static inline void ClearPage##uname(struct page *page)                  \
 149                         { clear_bit(PG_##lname, &page->flags); }
 150
 151 #define __SETPAGEFLAG(uname, lname)                                     \
 152 static inline void __SetPage##uname(struct page *page)                  \
 153                         { __set_bit(PG_##lname, &page->flags); }
 154
 155 #define __CLEARPAGEFLAG(uname, lname)                                   \
 156 static inline void __ClearPage##uname(struct page *page)                \
 157                         { __clear_bit(PG_##lname, &page->flags); }
 158
 159 #define TESTSETFLAG(uname, lname)                                       \
 160 static inline int TestSetPage##uname(struct page *page)                 \
 161                 { return test_and_set_bit(PG_##lname, &page->flags); }
 162
 163 #define TESTCLEARFLAG(uname, lname)                                     \
 164 static inline int TestClearPage##uname(struct page *page)               \
 165                 { return test_and_clear_bit(PG_##lname, &page->flags); }
 166
 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(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 struct page;    /* forward declaration */
 194
 195 TESTPAGEFLAG(Locked, locked) TESTSETFLAG(Locked, locked)
 196 PAGEFLAG(Error, error)
 197 PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced)
 198 PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty, dirty)
 199 PAGEFLAG(LRU, lru) __CLEARPAGEFLAG(LRU, lru)
 200 PAGEFLAG(Active, active) __CLEARPAGEFLAG(Active, active)
 201         TESTCLEARFLAG(Active, active)
 202 __PAGEFLAG(Slab, slab)
 203 PAGEFLAG(Checked, checked)              /* Used by some filesystems */
 204 PAGEFLAG(Pinned, pinned) TESTSCFLAG(Pinned, pinned)     /* Xen */
 205 PAGEFLAG(SavePinned, savepinned);                       /* Xen */
 206 PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
 207 PAGEFLAG(SwapBacked, swapbacked) __CLEARPAGEFLAG(SwapBacked, swapbacked)
 208
 209 __PAGEFLAG(SlobFree, slob_free)
 210
 211 __PAGEFLAG(SlubFrozen, slub_frozen)
 212 __PAGEFLAG(SlubDebug, slub_debug)
 213
 214 /*
 215  * Private page markings that may be used by the filesystem that owns the page
 216  * for its own purposes.
 217  * - PG_private and PG_private_2 cause releasepage() and co to be invoked
 218  */
 219 PAGEFLAG(Private, private) __SETPAGEFLAG(Private, private)
 220         __CLEARPAGEFLAG(Private, private)
 221 PAGEFLAG(Private2, private_2) TESTSCFLAG(Private2, private_2)
 222 PAGEFLAG(OwnerPriv1, owner_priv_1) TESTCLEARFLAG(OwnerPriv1, owner_priv_1)
 223
 224 /*
 225  * Only test-and-set exist for PG_writeback.  The unconditional operators are
 226  * risky: they bypass page accounting.
 227  */
 228 TESTPAGEFLAG(Writeback, writeback) TESTSCFLAG(Writeback, writeback)
 229 __PAGEFLAG(Buddy, buddy)
 230 PAGEFLAG(MappedToDisk, mappedtodisk)
 231
 232 /* PG_readahead is only used for file reads; PG_reclaim is only for writes */
 233 PAGEFLAG(Reclaim, reclaim) TESTCLEARFLAG(Reclaim, reclaim)
 234 PAGEFLAG(Readahead, reclaim)            /* Reminder to do async read-ahead */
 235
 236 #ifdef CONFIG_HIGHMEM
 237 /*
 238  * Must use a macro here due to header dependency issues. page_zone() is not
 239  * available at this point.
 240  */
 241 #define PageHighMem(__p) is_highmem(page_zone(__p))
 242 #else
 243 PAGEFLAG_FALSE(HighMem)
 244 #endif
 245
 246 #ifdef CONFIG_SWAP
 247 PAGEFLAG(SwapCache, swapcache)
 248 #else
 249 PAGEFLAG_FALSE(SwapCache)
 250         SETPAGEFLAG_NOOP(SwapCache) CLEARPAGEFLAG_NOOP(SwapCache)
 251 #endif
 252
 253 PAGEFLAG(Unevictable, unevictable) __CLEARPAGEFLAG(Unevictable, unevictable)
 254         TESTCLEARFLAG(Unevictable, unevictable)
 255
 256 #ifdef CONFIG_HAVE_MLOCKED_PAGE_BIT
 257 #define MLOCK_PAGES 1
 258 PAGEFLAG(Mlocked, mlocked) __CLEARPAGEFLAG(Mlocked, mlocked)
 259         TESTSCFLAG(Mlocked, mlocked)
 260 #else
 261 #define MLOCK_PAGES 0
 262 PAGEFLAG_FALSE(Mlocked)
 263         SETPAGEFLAG_NOOP(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 TESTSETFLAG(HWPoison, hwpoison)
 275 #define __PG_HWPOISON (1UL << PG_hwpoison)
 276 #else
 277 PAGEFLAG_FALSE(HWPoison)
 278 #define __PG_HWPOISON 0
 279 #endif
 280
 281 static inline int PageUptodate(struct page *page)
 282 {
 283         int ret = test_bit(PG_uptodate, &(page)->flags);
 284
 285         /*
 286          * Must ensure that the data we read out of the page is loaded
 287          * _after_ we've loaded page->flags to check for PageUptodate.
 288          * We can skip the barrier if the page is not uptodate, because
 289          * we wouldn't be reading anything from it.
 290          *
 291          * See SetPageUptodate() for the other side of the story.
 292          */
 293         if (ret)
 294                 smp_rmb();
 295
 296         return ret;
 297 }
 298
 299 static inline void __SetPageUptodate(struct page *page)
 300 {
 301         smp_wmb();
 302         __set_bit(PG_uptodate, &(page)->flags);
 303 }
 304
 305 static inline void SetPageUptodate(struct page *page)
 306 {
 307 #ifdef CONFIG_S390
 308         if (!test_and_set_bit(PG_uptodate, &page->flags))
 309                 page_clear_dirty(page);
 310 #else
 311         /*
 312          * Memory barrier must be issued before setting the PG_uptodate bit,
 313          * so that all previous stores issued in order to bring the page
 314          * uptodate are actually visible before PageUptodate becomes true.
 315          *
 316          * s390 doesn't need an explicit smp_wmb here because the test and
 317          * set bit already provides full barriers.
 318          */
 319         smp_wmb();
 320         set_bit(PG_uptodate, &(page)->flags);
 321 #endif
 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);
 330
 331 static inline void set_page_writeback(struct page *page)
 332 {
 333         test_set_page_writeback(page);
 334 }
 335
 336 #ifdef CONFIG_PAGEFLAGS_EXTENDED
 337 /*
 338  * System with lots of page flags available. This allows separate
 339  * flags for PageHead() and PageTail() checks of compound pages so that bit
 340  * tests can be used in performance sensitive paths. PageCompound is
 341  * generally not used in hot code paths.
 342  */
 343 __PAGEFLAG(Head, head)
 344 __PAGEFLAG(Tail, tail)
 345
 346 static inline int PageCompound(struct page *page)
 347 {
 348         return page->flags & ((1L << PG_head) | (1L << PG_tail));
 349
 350 }
 351 #else
 352 /*
 353  * Reduce page flag use as much as possible by overlapping
 354  * compound page flags with the flags used for page cache pages. Possible
 355  * because PageCompound is always set for compound pages and not for
 356  * pages on the LRU and/or pagecache.
 357  */
 358 TESTPAGEFLAG(Compound, compound)
 359 __PAGEFLAG(Head, compound)
 360
 361 /*
 362  * PG_reclaim is used in combination with PG_compound to mark the
 363  * head and tail of a compound page. This saves one page flag
 364  * but makes it impossible to use compound pages for the page cache.
 365  * The PG_reclaim bit would have to be used for reclaim or readahead
 366  * if compound pages enter the page cache.
 367  *
 368  * PG_compound & PG_reclaim     => Tail page
 369  * PG_compound & ~PG_reclaim    => Head page
 370  */
 371 #define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))
 372
 373 static inline int PageTail(struct page *page)
 374 {
 375         return ((page->flags & PG_head_tail_mask) == PG_head_tail_mask);
 376 }
 377
 378 static inline void __SetPageTail(struct page *page)
 379 {
 380         page->flags |= PG_head_tail_mask;
 381 }
 382
 383 static inline void __ClearPageTail(struct page *page)
 384 {
 385         page->flags &= ~PG_head_tail_mask;
 386 }
 387
 388 #endif /* !PAGEFLAGS_EXTENDED */
 389
 390 #ifdef CONFIG_HAVE_MLOCKED_PAGE_BIT
 391 #define __PG_MLOCKED            (1 << PG_mlocked)
 392 #else
 393 #define __PG_MLOCKED            0
 394 #endif
 395
 396 /*
 397  * Flags checked when a page is freed.  Pages being freed should not have
 398  * these flags set.  It they are, there is a problem.
 399  */
 400 #define PAGE_FLAGS_CHECK_AT_FREE \
 401         (1 << PG_lru     | 1 << PG_locked    | \
 402          1 << PG_private | 1 << PG_private_2 | \
 403          1 << PG_buddy   | 1 << PG_writeback | 1 << PG_reserved | \
 404          1 << PG_slab    | 1 << PG_swapcache | 1 << PG_active | \
 405          1 << PG_unevictable | __PG_MLOCKED | __PG_HWPOISON)
 406
 407 /*
 408  * Flags checked when a page is prepped for return by the page allocator.
 409  * Pages being prepped should not have any flags set.  It they are set,
 410  * there has been a kernel bug or struct page corruption.
 411  */
 412 #define PAGE_FLAGS_CHECK_AT_PREP        ((1 << NR_PAGEFLAGS) - 1)
 413
 414 #endif /* !__GENERATING_BOUNDS_H */
 415
 416 /**
 417  * page_has_private - Determine if page has private stuff
 418  * @page: The page to be checked
 419  *
 420  * Determine if a page has private stuff, indicating that release routines
 421  * should be invoked upon it.
 422  */
 423 #define page_has_private(page)                  \
 424         ((page)->flags & ((1 << PG_private) |   \
 425                           (1 << PG_private_2)))
 426
 427 #endif  /* PAGE_FLAGS_H */