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  */
  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_buddy,               /* Page is free, on buddy lists */
  97         PG_swapbacked,          /* Page is backed by RAM/swap */
  98         PG_unevictable,         /* Page is "unevictable"  */
  99 #ifdef CONFIG_HAVE_MLOCKED_PAGE_BIT
 100         PG_mlocked,             /* Page is vma mlocked */
 101 #endif
 102 #ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
 103         PG_uncached,            /* Page has been mapped as uncached */
 104 #endif
 105         __NR_PAGEFLAGS,
 106
 107         /* Filesystems */
 108         PG_checked = PG_owner_priv_1,
 109
 110         /* Two page bits are conscripted by FS-Cache to maintain local caching
 111          * state.  These bits are set on pages belonging to the netfs's inodes
 112          * when those inodes are being locally cached.
 113          */
 114         PG_fscache = PG_private_2,      /* page backed by cache */
 115
 116         /* XEN */
 117         PG_pinned = PG_owner_priv_1,
 118         PG_savepinned = PG_dirty,
 119
 120         /* SLOB */
 121         PG_slob_free = PG_private,
 122
 123         /* SLUB */
 124         PG_slub_frozen = PG_active,
 125         PG_slub_debug = PG_error,
 126 };
 127
 128 #ifndef __GENERATING_BOUNDS_H
 129
 130 /*
 131  * Macros to create function definitions for page flags
 132  */
 133 #define TESTPAGEFLAG(uname, lname)                                      \
 134 static inline int Page##uname(struct page *page)                        \
 135                         { return test_bit(PG_##lname, &page->flags); }
 136
 137 #define SETPAGEFLAG(uname, lname)                                       \
 138 static inline void SetPage##uname(struct page *page)                    \
 139                         { set_bit(PG_##lname, &page->flags); }
 140
 141 #define CLEARPAGEFLAG(uname, lname)                                     \
 142 static inline void ClearPage##uname(struct page *page)                  \
 143                         { clear_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 TESTSETFLAG(uname, lname)                                       \
 154 static inline int TestSetPage##uname(struct page *page)                 \
 155                 { return test_and_set_bit(PG_##lname, &page->flags); }
 156
 157 #define TESTCLEARFLAG(uname, lname)                                     \
 158 static inline int TestClearPage##uname(struct page *page)               \
 159                 { return test_and_clear_bit(PG_##lname, &page->flags); }
 160
 161
 162 #define PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)               \
 163         SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname)
 164
 165 #define __PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)             \
 166         __SETPAGEFLAG(uname, lname)  __CLEARPAGEFLAG(uname, lname)
 167
 168 #define PAGEFLAG_FALSE(uname)                                           \
 169 static inline int Page##uname(struct page *page)                        \
 170                         { return 0; }
 171
 172 #define TESTSCFLAG(uname, lname)                                        \
 173         TESTSETFLAG(uname, lname) TESTCLEARFLAG(uname, lname)
 174
 175 #define SETPAGEFLAG_NOOP(uname)                                         \
 176 static inline void SetPage##uname(struct page *page) {  }
 177
 178 #define CLEARPAGEFLAG_NOOP(uname)                                       \
 179 static inline void ClearPage##uname(struct page *page) {  }
 180
 181 #define __CLEARPAGEFLAG_NOOP(uname)                                     \
 182 static inline void __ClearPage##uname(struct page *page) {  }
 183
 184 #define TESTCLEARFLAG_FALSE(uname)                                      \
 185 static inline int TestClearPage##uname(struct page *page) { return 0; }
 186
 187 struct page;    /* forward declaration */
 188
 189 TESTPAGEFLAG(Locked, locked) TESTSETFLAG(Locked, locked)
 190 PAGEFLAG(Error, error)
 191 PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced)
 192 PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty, dirty)
 193 PAGEFLAG(LRU, lru) __CLEARPAGEFLAG(LRU, lru)
 194 PAGEFLAG(Active, active) __CLEARPAGEFLAG(Active, active)
 195         TESTCLEARFLAG(Active, active)
 196 __PAGEFLAG(Slab, slab)
 197 PAGEFLAG(Checked, checked)              /* Used by some filesystems */
 198 PAGEFLAG(Pinned, pinned) TESTSCFLAG(Pinned, pinned)     /* Xen */
 199 PAGEFLAG(SavePinned, savepinned);                       /* Xen */
 200 PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
 201 PAGEFLAG(SwapBacked, swapbacked) __CLEARPAGEFLAG(SwapBacked, swapbacked)
 202
 203 __PAGEFLAG(SlobFree, slob_free)
 204
 205 __PAGEFLAG(SlubFrozen, slub_frozen)
 206 __PAGEFLAG(SlubDebug, slub_debug)
 207
 208 /*
 209  * Private page markings that may be used by the filesystem that owns the page
 210  * for its own purposes.
 211  * - PG_private and PG_private_2 cause releasepage() and co to be invoked
 212  */
 213 PAGEFLAG(Private, private) __SETPAGEFLAG(Private, private)
 214         __CLEARPAGEFLAG(Private, private)
 215 PAGEFLAG(Private2, private_2) TESTSCFLAG(Private2, private_2)
 216 PAGEFLAG(OwnerPriv1, owner_priv_1) TESTCLEARFLAG(OwnerPriv1, owner_priv_1)
 217
 218 /*
 219  * Only test-and-set exist for PG_writeback.  The unconditional operators are
 220  * risky: they bypass page accounting.
 221  */
 222 TESTPAGEFLAG(Writeback, writeback) TESTSCFLAG(Writeback, writeback)
 223 __PAGEFLAG(Buddy, buddy)
 224 PAGEFLAG(MappedToDisk, mappedtodisk)
 225
 226 /* PG_readahead is only used for file reads; PG_reclaim is only for writes */
 227 PAGEFLAG(Reclaim, reclaim) TESTCLEARFLAG(Reclaim, reclaim)
 228 PAGEFLAG(Readahead, reclaim)            /* Reminder to do async read-ahead */
 229
 230 #ifdef CONFIG_HIGHMEM
 231 /*
 232  * Must use a macro here due to header dependency issues. page_zone() is not
 233  * available at this point.
 234  */
 235 #define PageHighMem(__p) is_highmem(page_zone(__p))
 236 #else
 237 PAGEFLAG_FALSE(HighMem)
 238 #endif
 239
 240 #ifdef CONFIG_SWAP
 241 PAGEFLAG(SwapCache, swapcache)
 242 #else
 243 PAGEFLAG_FALSE(SwapCache)
 244         SETPAGEFLAG_NOOP(SwapCache) CLEARPAGEFLAG_NOOP(SwapCache)
 245 #endif
 246
 247 PAGEFLAG(Unevictable, unevictable) __CLEARPAGEFLAG(Unevictable, unevictable)
 248         TESTCLEARFLAG(Unevictable, unevictable)
 249
 250 #ifdef CONFIG_HAVE_MLOCKED_PAGE_BIT
 251 #define MLOCK_PAGES 1
 252 PAGEFLAG(Mlocked, mlocked) __CLEARPAGEFLAG(Mlocked, mlocked)
 253         TESTSCFLAG(Mlocked, mlocked)
 254 #else
 255 #define MLOCK_PAGES 0
 256 PAGEFLAG_FALSE(Mlocked)
 257         SETPAGEFLAG_NOOP(Mlocked) TESTCLEARFLAG_FALSE(Mlocked)
 258 #endif
 259
 260 #ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
 261 PAGEFLAG(Uncached, uncached)
 262 #else
 263 PAGEFLAG_FALSE(Uncached)
 264 #endif
 265
 266 static inline int PageUptodate(struct page *page)
 267 {
 268         int ret = test_bit(PG_uptodate, &(page)->flags);
 269
 270         /*
 271          * Must ensure that the data we read out of the page is loaded
 272          * _after_ we've loaded page->flags to check for PageUptodate.
 273          * We can skip the barrier if the page is not uptodate, because
 274          * we wouldn't be reading anything from it.
 275          *
 276          * See SetPageUptodate() for the other side of the story.
 277          */
 278         if (ret)
 279                 smp_rmb();
 280
 281         return ret;
 282 }
 283
 284 static inline void __SetPageUptodate(struct page *page)
 285 {
 286         smp_wmb();
 287         __set_bit(PG_uptodate, &(page)->flags);
 288 }
 289
 290 static inline void SetPageUptodate(struct page *page)
 291 {
 292 #ifdef CONFIG_S390
 293         if (!test_and_set_bit(PG_uptodate, &page->flags))
 294                 page_clear_dirty(page);
 295 #else
 296         /*
 297          * Memory barrier must be issued before setting the PG_uptodate bit,
 298          * so that all previous stores issued in order to bring the page
 299          * uptodate are actually visible before PageUptodate becomes true.
 300          *
 301          * s390 doesn't need an explicit smp_wmb here because the test and
 302          * set bit already provides full barriers.
 303          */
 304         smp_wmb();
 305         set_bit(PG_uptodate, &(page)->flags);
 306 #endif
 307 }
 308
 309 CLEARPAGEFLAG(Uptodate, uptodate)
 310
 311 extern void cancel_dirty_page(struct page *page, unsigned int account_size);
 312
 313 int test_clear_page_writeback(struct page *page);
 314 int test_set_page_writeback(struct page *page);
 315
 316 static inline void set_page_writeback(struct page *page)
 317 {
 318         test_set_page_writeback(page);
 319 }
 320
 321 #ifdef CONFIG_PAGEFLAGS_EXTENDED
 322 /*
 323  * System with lots of page flags available. This allows separate
 324  * flags for PageHead() and PageTail() checks of compound pages so that bit
 325  * tests can be used in performance sensitive paths. PageCompound is
 326  * generally not used in hot code paths.
 327  */
 328 __PAGEFLAG(Head, head)
 329 __PAGEFLAG(Tail, tail)
 330
 331 static inline int PageCompound(struct page *page)
 332 {
 333         return page->flags & ((1L << PG_head) | (1L << PG_tail));
 334
 335 }
 336 #else
 337 /*
 338  * Reduce page flag use as much as possible by overlapping
 339  * compound page flags with the flags used for page cache pages. Possible
 340  * because PageCompound is always set for compound pages and not for
 341  * pages on the LRU and/or pagecache.
 342  */
 343 TESTPAGEFLAG(Compound, compound)
 344 __PAGEFLAG(Head, compound)
 345
 346 /*
 347  * PG_reclaim is used in combination with PG_compound to mark the
 348  * head and tail of a compound page. This saves one page flag
 349  * but makes it impossible to use compound pages for the page cache.
 350  * The PG_reclaim bit would have to be used for reclaim or readahead
 351  * if compound pages enter the page cache.
 352  *
 353  * PG_compound & PG_reclaim     => Tail page
 354  * PG_compound & ~PG_reclaim    => Head page
 355  */
 356 #define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))
 357
 358 static inline int PageTail(struct page *page)
 359 {
 360         return ((page->flags & PG_head_tail_mask) == PG_head_tail_mask);
 361 }
 362
 363 static inline void __SetPageTail(struct page *page)
 364 {
 365         page->flags |= PG_head_tail_mask;
 366 }
 367
 368 static inline void __ClearPageTail(struct page *page)
 369 {
 370         page->flags &= ~PG_head_tail_mask;
 371 }
 372
 373 #endif /* !PAGEFLAGS_EXTENDED */
 374
 375 #ifdef CONFIG_HAVE_MLOCKED_PAGE_BIT
 376 #define __PG_MLOCKED            (1 << PG_mlocked)
 377 #else
 378 #define __PG_MLOCKED            0
 379 #endif
 380
 381 /*
 382  * Flags checked when a page is freed.  Pages being freed should not have
 383  * these flags set.  It they are, there is a problem.
 384  */
 385 #define PAGE_FLAGS_CHECK_AT_FREE \
 386         (1 << PG_lru     | 1 << PG_locked    | \
 387          1 << PG_private | 1 << PG_private_2 | \
 388          1 << PG_buddy   | 1 << PG_writeback | 1 << PG_reserved | \
 389          1 << PG_slab    | 1 << PG_swapcache | 1 << PG_active | \
 390          1 << PG_unevictable | __PG_MLOCKED)
 391
 392 /*
 393  * Flags checked when a page is prepped for return by the page allocator.
 394  * Pages being prepped should not have any flags set.  It they are set,
 395  * there has been a kernel bug or struct page corruption.
 396  */
 397 #define PAGE_FLAGS_CHECK_AT_PREP        ((1 << NR_PAGEFLAGS) - 1)
 398
 399 #endif /* !__GENERATING_BOUNDS_H */
 400
 401 /**
 402  * page_has_private - Determine if page has private stuff
 403  * @page: The page to be checked
 404  *
 405  * Determine if a page has private stuff, indicating that release routines
 406  * should be invoked upon it.
 407  */
 408 #define page_has_private(page)                  \
 409         ((page)->flags & ((1 << PG_private) |   \
 410                           (1 << PG_private_2)))
 411
 412 #endif  /* PAGE_FLAGS_H */