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_writeback,           /* Page is under writeback */
  86 #ifdef CONFIG_PAGEFLAGS_EXTENDED
  87         PG_head,                /* A head page */
  88         PG_tail,                /* A tail page */
  89 #else
  90         PG_compound,            /* A compound page */
  91 #endif
  92         PG_swapcache,           /* Swap page: swp_entry_t in private */
  93         PG_mappedtodisk,        /* Has blocks allocated on-disk */
  94         PG_reclaim,             /* To be reclaimed asap */
  95         PG_buddy,               /* Page is free, on buddy lists */
  96         PG_swapbacked,          /* Page is backed by RAM/swap */
  97 #ifdef CONFIG_UNEVICTABLE_LRU
  98         PG_unevictable,         /* Page is "unevictable"  */
  99         PG_mlocked,             /* Page is vma mlocked */
 100 #endif
 101 #ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
 102         PG_uncached,            /* Page has been mapped as uncached */
 103 #endif
 104         __NR_PAGEFLAGS,
 105
 106         /* Filesystems */
 107         PG_checked = PG_owner_priv_1,
 108
 109         /* XEN */
 110         PG_pinned = PG_owner_priv_1,
 111         PG_savepinned = PG_dirty,
 112
 113         /* SLOB */
 114         PG_slob_page = PG_active,
 115         PG_slob_free = PG_private,
 116
 117         /* SLUB */
 118         PG_slub_frozen = PG_active,
 119         PG_slub_debug = PG_error,
 120 };
 121
 122 #ifndef __GENERATING_BOUNDS_H
 123
 124 /*
 125  * Macros to create function definitions for page flags
 126  */
 127 #define TESTPAGEFLAG(uname, lname)                                      \
 128 static inline int Page##uname(struct page *page)                        \
 129                         { return test_bit(PG_##lname, &page->flags); }
 130
 131 #define SETPAGEFLAG(uname, lname)                                       \
 132 static inline void SetPage##uname(struct page *page)                    \
 133                         { set_bit(PG_##lname, &page->flags); }
 134
 135 #define CLEARPAGEFLAG(uname, lname)                                     \
 136 static inline void ClearPage##uname(struct page *page)                  \
 137                         { clear_bit(PG_##lname, &page->flags); }
 138
 139 #define __SETPAGEFLAG(uname, lname)                                     \
 140 static inline void __SetPage##uname(struct page *page)                  \
 141                         { __set_bit(PG_##lname, &page->flags); }
 142
 143 #define __CLEARPAGEFLAG(uname, lname)                                   \
 144 static inline void __ClearPage##uname(struct page *page)                \
 145                         { __clear_bit(PG_##lname, &page->flags); }
 146
 147 #define TESTSETFLAG(uname, lname)                                       \
 148 static inline int TestSetPage##uname(struct page *page)                 \
 149                 { return test_and_set_bit(PG_##lname, &page->flags); }
 150
 151 #define TESTCLEARFLAG(uname, lname)                                     \
 152 static inline int TestClearPage##uname(struct page *page)               \
 153                 { return test_and_clear_bit(PG_##lname, &page->flags); }
 154
 155
 156 #define PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)               \
 157         SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname)
 158
 159 #define __PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)             \
 160         __SETPAGEFLAG(uname, lname)  __CLEARPAGEFLAG(uname, lname)
 161
 162 #define PAGEFLAG_FALSE(uname)                                           \
 163 static inline int Page##uname(struct page *page)                        \
 164                         { return 0; }
 165
 166 #define TESTSCFLAG(uname, lname)                                        \
 167         TESTSETFLAG(uname, lname) TESTCLEARFLAG(uname, lname)
 168
 169 #define SETPAGEFLAG_NOOP(uname)                                         \
 170 static inline void SetPage##uname(struct page *page) {  }
 171
 172 #define CLEARPAGEFLAG_NOOP(uname)                                       \
 173 static inline void ClearPage##uname(struct page *page) {  }
 174
 175 #define __CLEARPAGEFLAG_NOOP(uname)                                     \
 176 static inline void __ClearPage##uname(struct page *page) {  }
 177
 178 #define TESTCLEARFLAG_FALSE(uname)                                      \
 179 static inline int TestClearPage##uname(struct page *page) { return 0; }
 180
 181 struct page;    /* forward declaration */
 182
 183 TESTPAGEFLAG(Locked, locked)
 184 PAGEFLAG(Error, error)
 185 PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced)
 186 PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty, dirty)
 187 PAGEFLAG(LRU, lru) __CLEARPAGEFLAG(LRU, lru)
 188 PAGEFLAG(Active, active) __CLEARPAGEFLAG(Active, active)
 189         TESTCLEARFLAG(Active, active)
 190 __PAGEFLAG(Slab, slab)
 191 PAGEFLAG(Checked, checked)              /* Used by some filesystems */
 192 PAGEFLAG(Pinned, pinned) TESTSCFLAG(Pinned, pinned)     /* Xen */
 193 PAGEFLAG(SavePinned, savepinned);                       /* Xen */
 194 PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
 195 PAGEFLAG(Private, private) __CLEARPAGEFLAG(Private, private)
 196         __SETPAGEFLAG(Private, private)
 197 PAGEFLAG(SwapBacked, swapbacked) __CLEARPAGEFLAG(SwapBacked, swapbacked)
 198
 199 __PAGEFLAG(SlobPage, slob_page)
 200 __PAGEFLAG(SlobFree, slob_free)
 201
 202 __PAGEFLAG(SlubFrozen, slub_frozen)
 203 __PAGEFLAG(SlubDebug, slub_debug)
 204
 205 /*
 206  * Only test-and-set exist for PG_writeback.  The unconditional operators are
 207  * risky: they bypass page accounting.
 208  */
 209 TESTPAGEFLAG(Writeback, writeback) TESTSCFLAG(Writeback, writeback)
 210 __PAGEFLAG(Buddy, buddy)
 211 PAGEFLAG(MappedToDisk, mappedtodisk)
 212
 213 /* PG_readahead is only used for file reads; PG_reclaim is only for writes */
 214 PAGEFLAG(Reclaim, reclaim) TESTCLEARFLAG(Reclaim, reclaim)
 215 PAGEFLAG(Readahead, reclaim)            /* Reminder to do async read-ahead */
 216
 217 #ifdef CONFIG_HIGHMEM
 218 /*
 219  * Must use a macro here due to header dependency issues. page_zone() is not
 220  * available at this point.
 221  */
 222 #define PageHighMem(__p) is_highmem(page_zone(__p))
 223 #else
 224 PAGEFLAG_FALSE(HighMem)
 225 #endif
 226
 227 #ifdef CONFIG_SWAP
 228 PAGEFLAG(SwapCache, swapcache)
 229 #else
 230 PAGEFLAG_FALSE(SwapCache)
 231         SETPAGEFLAG_NOOP(SwapCache) CLEARPAGEFLAG_NOOP(SwapCache)
 232 #endif
 233
 234 #ifdef CONFIG_UNEVICTABLE_LRU
 235 PAGEFLAG(Unevictable, unevictable) __CLEARPAGEFLAG(Unevictable, unevictable)
 236         TESTCLEARFLAG(Unevictable, unevictable)
 237
 238 #define MLOCK_PAGES 1
 239 PAGEFLAG(Mlocked, mlocked) __CLEARPAGEFLAG(Mlocked, mlocked)
 240         TESTSCFLAG(Mlocked, mlocked)
 241
 242 #else
 243
 244 #define MLOCK_PAGES 0
 245 PAGEFLAG_FALSE(Mlocked)
 246         SETPAGEFLAG_NOOP(Mlocked) TESTCLEARFLAG_FALSE(Mlocked)
 247
 248 PAGEFLAG_FALSE(Unevictable) TESTCLEARFLAG_FALSE(Unevictable)
 249         SETPAGEFLAG_NOOP(Unevictable) CLEARPAGEFLAG_NOOP(Unevictable)
 250         __CLEARPAGEFLAG_NOOP(Unevictable)
 251 #endif
 252
 253 #ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
 254 PAGEFLAG(Uncached, uncached)
 255 #else
 256 PAGEFLAG_FALSE(Uncached)
 257 #endif
 258
 259 static inline int PageUptodate(struct page *page)
 260 {
 261         int ret = test_bit(PG_uptodate, &(page)->flags);
 262
 263         /*
 264          * Must ensure that the data we read out of the page is loaded
 265          * _after_ we've loaded page->flags to check for PageUptodate.
 266          * We can skip the barrier if the page is not uptodate, because
 267          * we wouldn't be reading anything from it.
 268          *
 269          * See SetPageUptodate() for the other side of the story.
 270          */
 271         if (ret)
 272                 smp_rmb();
 273
 274         return ret;
 275 }
 276
 277 static inline void __SetPageUptodate(struct page *page)
 278 {
 279         smp_wmb();
 280         __set_bit(PG_uptodate, &(page)->flags);
 281 }
 282
 283 static inline void SetPageUptodate(struct page *page)
 284 {
 285 #ifdef CONFIG_S390
 286         if (!test_and_set_bit(PG_uptodate, &page->flags))
 287                 page_clear_dirty(page);
 288 #else
 289         /*
 290          * Memory barrier must be issued before setting the PG_uptodate bit,
 291          * so that all previous stores issued in order to bring the page
 292          * uptodate are actually visible before PageUptodate becomes true.
 293          *
 294          * s390 doesn't need an explicit smp_wmb here because the test and
 295          * set bit already provides full barriers.
 296          */
 297         smp_wmb();
 298         set_bit(PG_uptodate, &(page)->flags);
 299 #endif
 300 }
 301
 302 CLEARPAGEFLAG(Uptodate, uptodate)
 303
 304 extern void cancel_dirty_page(struct page *page, unsigned int account_size);
 305
 306 int test_clear_page_writeback(struct page *page);
 307 int test_set_page_writeback(struct page *page);
 308
 309 static inline void set_page_writeback(struct page *page)
 310 {
 311         test_set_page_writeback(page);
 312 }
 313
 314 #ifdef CONFIG_PAGEFLAGS_EXTENDED
 315 /*
 316  * System with lots of page flags available. This allows separate
 317  * flags for PageHead() and PageTail() checks of compound pages so that bit
 318  * tests can be used in performance sensitive paths. PageCompound is
 319  * generally not used in hot code paths.
 320  */
 321 __PAGEFLAG(Head, head)
 322 __PAGEFLAG(Tail, tail)
 323
 324 static inline int PageCompound(struct page *page)
 325 {
 326         return page->flags & ((1L << PG_head) | (1L << PG_tail));
 327
 328 }
 329 #else
 330 /*
 331  * Reduce page flag use as much as possible by overlapping
 332  * compound page flags with the flags used for page cache pages. Possible
 333  * because PageCompound is always set for compound pages and not for
 334  * pages on the LRU and/or pagecache.
 335  */
 336 TESTPAGEFLAG(Compound, compound)
 337 __PAGEFLAG(Head, compound)
 338
 339 /*
 340  * PG_reclaim is used in combination with PG_compound to mark the
 341  * head and tail of a compound page. This saves one page flag
 342  * but makes it impossible to use compound pages for the page cache.
 343  * The PG_reclaim bit would have to be used for reclaim or readahead
 344  * if compound pages enter the page cache.
 345  *
 346  * PG_compound & PG_reclaim     => Tail page
 347  * PG_compound & ~PG_reclaim    => Head page
 348  */
 349 #define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))
 350
 351 static inline int PageTail(struct page *page)
 352 {
 353         return ((page->flags & PG_head_tail_mask) == PG_head_tail_mask);
 354 }
 355
 356 static inline void __SetPageTail(struct page *page)
 357 {
 358         page->flags |= PG_head_tail_mask;
 359 }
 360
 361 static inline void __ClearPageTail(struct page *page)
 362 {
 363         page->flags &= ~PG_head_tail_mask;
 364 }
 365
 366 #endif /* !PAGEFLAGS_EXTENDED */
 367
 368 #ifdef CONFIG_UNEVICTABLE_LRU
 369 #define __PG_UNEVICTABLE        (1 << PG_unevictable)
 370 #define __PG_MLOCKED            (1 << PG_mlocked)
 371 #else
 372 #define __PG_UNEVICTABLE        0
 373 #define __PG_MLOCKED            0
 374 #endif
 375
 376 /*
 377  * Flags checked when a page is freed.  Pages being freed should not have
 378  * these flags set.  It they are, there is a problem.
 379  */
 380 #define PAGE_FLAGS_CHECK_AT_FREE \
 381         (1 << PG_lru   | 1 << PG_private   | 1 << PG_locked | \
 382          1 << PG_buddy | 1 << PG_writeback | 1 << PG_reserved | \
 383          1 << PG_slab  | 1 << PG_swapcache | 1 << PG_active | \
 384          __PG_UNEVICTABLE | __PG_MLOCKED)
 385
 386 /*
 387  * Flags checked when a page is prepped for return by the page allocator.
 388  * Pages being prepped should not have any flags set.  It they are set,
 389  * there has been a kernel bug or struct page corruption.
 390  */
 391 #define PAGE_FLAGS_CHECK_AT_PREP        ((1 << NR_PAGEFLAGS) - 1)
 392
 393 #endif /* !__GENERATING_BOUNDS_H */
 394 #endif  /* PAGE_FLAGS_H */