linux/include/linux/page-flags.h
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   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 */
  72enum 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)                                      \
 128static inline int Page##uname(struct page *page)                        \
 129                        { return test_bit(PG_##lname, &page->flags); }
 130
 131#define SETPAGEFLAG(uname, lname)                                       \
 132static inline void SetPage##uname(struct page *page)                    \
 133                        { set_bit(PG_##lname, &page->flags); }
 134
 135#define CLEARPAGEFLAG(uname, lname)                                     \
 136static inline void ClearPage##uname(struct page *page)                  \
 137                        { clear_bit(PG_##lname, &page->flags); }
 138
 139#define __SETPAGEFLAG(uname, lname)                                     \
 140static inline void __SetPage##uname(struct page *page)                  \
 141                        { __set_bit(PG_##lname, &page->flags); }
 142
 143#define __CLEARPAGEFLAG(uname, lname)                                   \
 144static inline void __ClearPage##uname(struct page *page)                \
 145                        { __clear_bit(PG_##lname, &page->flags); }
 146
 147#define TESTSETFLAG(uname, lname)                                       \
 148static inline int TestSetPage##uname(struct page *page)                 \
 149                { return test_and_set_bit(PG_##lname, &page->flags); }
 150
 151#define TESTCLEARFLAG(uname, lname)                                     \
 152static 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)                                           \
 163static 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)                                         \
 170static inline void SetPage##uname(struct page *page) {  }
 171
 172#define CLEARPAGEFLAG_NOOP(uname)                                       \
 173static inline void ClearPage##uname(struct page *page) {  }
 174
 175#define __CLEARPAGEFLAG_NOOP(uname)                                     \
 176static inline void __ClearPage##uname(struct page *page) {  }
 177
 178#define TESTCLEARFLAG_FALSE(uname)                                      \
 179static inline int TestClearPage##uname(struct page *page) { return 0; }
 180
 181struct page;    /* forward declaration */
 182
 183TESTPAGEFLAG(Locked, locked)
 184PAGEFLAG(Error, error)
 185PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced)
 186PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty, dirty)
 187PAGEFLAG(LRU, lru) __CLEARPAGEFLAG(LRU, lru)
 188PAGEFLAG(Active, active) __CLEARPAGEFLAG(Active, active)
 189        TESTCLEARFLAG(Active, active)
 190__PAGEFLAG(Slab, slab)
 191PAGEFLAG(Checked, checked)              /* Used by some filesystems */
 192PAGEFLAG(Pinned, pinned) TESTSCFLAG(Pinned, pinned)     /* Xen */
 193PAGEFLAG(SavePinned, savepinned);                       /* Xen */
 194PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
 195PAGEFLAG(Private, private) __CLEARPAGEFLAG(Private, private)
 196        __SETPAGEFLAG(Private, private)
 197PAGEFLAG(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 */
 209TESTPAGEFLAG(Writeback, writeback) TESTSCFLAG(Writeback, writeback)
 210__PAGEFLAG(Buddy, buddy)
 211PAGEFLAG(MappedToDisk, mappedtodisk)
 212
 213/* PG_readahead is only used for file reads; PG_reclaim is only for writes */
 214PAGEFLAG(Reclaim, reclaim) TESTCLEARFLAG(Reclaim, reclaim)
 215PAGEFLAG(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
 224PAGEFLAG_FALSE(HighMem)
 225#endif
 226
 227#ifdef CONFIG_SWAP
 228PAGEFLAG(SwapCache, swapcache)
 229#else
 230PAGEFLAG_FALSE(SwapCache)
 231#endif
 232
 233#ifdef CONFIG_UNEVICTABLE_LRU
 234PAGEFLAG(Unevictable, unevictable) __CLEARPAGEFLAG(Unevictable, unevictable)
 235        TESTCLEARFLAG(Unevictable, unevictable)
 236
 237#define MLOCK_PAGES 1
 238PAGEFLAG(Mlocked, mlocked) __CLEARPAGEFLAG(Mlocked, mlocked)
 239        TESTSCFLAG(Mlocked, mlocked)
 240
 241#else
 242
 243#define MLOCK_PAGES 0
 244PAGEFLAG_FALSE(Mlocked)
 245        SETPAGEFLAG_NOOP(Mlocked) TESTCLEARFLAG_FALSE(Mlocked)
 246
 247PAGEFLAG_FALSE(Unevictable) TESTCLEARFLAG_FALSE(Unevictable)
 248        SETPAGEFLAG_NOOP(Unevictable) CLEARPAGEFLAG_NOOP(Unevictable)
 249        __CLEARPAGEFLAG_NOOP(Unevictable)
 250#endif
 251
 252#ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
 253PAGEFLAG(Uncached, uncached)
 254#else
 255PAGEFLAG_FALSE(Uncached)
 256#endif
 257
 258static inline int PageUptodate(struct page *page)
 259{
 260        int ret = test_bit(PG_uptodate, &(page)->flags);
 261
 262        /*
 263         * Must ensure that the data we read out of the page is loaded
 264         * _after_ we've loaded page->flags to check for PageUptodate.
 265         * We can skip the barrier if the page is not uptodate, because
 266         * we wouldn't be reading anything from it.
 267         *
 268         * See SetPageUptodate() for the other side of the story.
 269         */
 270        if (ret)
 271                smp_rmb();
 272
 273        return ret;
 274}
 275
 276static inline void __SetPageUptodate(struct page *page)
 277{
 278        smp_wmb();
 279        __set_bit(PG_uptodate, &(page)->flags);
 280}
 281
 282static inline void SetPageUptodate(struct page *page)
 283{
 284#ifdef CONFIG_S390
 285        if (!test_and_set_bit(PG_uptodate, &page->flags))
 286                page_clear_dirty(page);
 287#else
 288        /*
 289         * Memory barrier must be issued before setting the PG_uptodate bit,
 290         * so that all previous stores issued in order to bring the page
 291         * uptodate are actually visible before PageUptodate becomes true.
 292         *
 293         * s390 doesn't need an explicit smp_wmb here because the test and
 294         * set bit already provides full barriers.
 295         */
 296        smp_wmb();
 297        set_bit(PG_uptodate, &(page)->flags);
 298#endif
 299}
 300
 301CLEARPAGEFLAG(Uptodate, uptodate)
 302
 303extern void cancel_dirty_page(struct page *page, unsigned int account_size);
 304
 305int test_clear_page_writeback(struct page *page);
 306int test_set_page_writeback(struct page *page);
 307
 308static inline void set_page_writeback(struct page *page)
 309{
 310        test_set_page_writeback(page);
 311}
 312
 313#ifdef CONFIG_PAGEFLAGS_EXTENDED
 314/*
 315 * System with lots of page flags available. This allows separate
 316 * flags for PageHead() and PageTail() checks of compound pages so that bit
 317 * tests can be used in performance sensitive paths. PageCompound is
 318 * generally not used in hot code paths.
 319 */
 320__PAGEFLAG(Head, head)
 321__PAGEFLAG(Tail, tail)
 322
 323static inline int PageCompound(struct page *page)
 324{
 325        return page->flags & ((1L << PG_head) | (1L << PG_tail));
 326
 327}
 328#else
 329/*
 330 * Reduce page flag use as much as possible by overlapping
 331 * compound page flags with the flags used for page cache pages. Possible
 332 * because PageCompound is always set for compound pages and not for
 333 * pages on the LRU and/or pagecache.
 334 */
 335TESTPAGEFLAG(Compound, compound)
 336__PAGEFLAG(Head, compound)
 337
 338/*
 339 * PG_reclaim is used in combination with PG_compound to mark the
 340 * head and tail of a compound page. This saves one page flag
 341 * but makes it impossible to use compound pages for the page cache.
 342 * The PG_reclaim bit would have to be used for reclaim or readahead
 343 * if compound pages enter the page cache.
 344 *
 345 * PG_compound & PG_reclaim     => Tail page
 346 * PG_compound & ~PG_reclaim    => Head page
 347 */
 348#define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))
 349
 350static inline int PageTail(struct page *page)
 351{
 352        return ((page->flags & PG_head_tail_mask) == PG_head_tail_mask);
 353}
 354
 355static inline void __SetPageTail(struct page *page)
 356{
 357        page->flags |= PG_head_tail_mask;
 358}
 359
 360static inline void __ClearPageTail(struct page *page)
 361{
 362        page->flags &= ~PG_head_tail_mask;
 363}
 364
 365#endif /* !PAGEFLAGS_EXTENDED */
 366
 367#ifdef CONFIG_UNEVICTABLE_LRU
 368#define __PG_UNEVICTABLE        (1 << PG_unevictable)
 369#define __PG_MLOCKED            (1 << PG_mlocked)
 370#else
 371#define __PG_UNEVICTABLE        0
 372#define __PG_MLOCKED            0
 373#endif
 374
 375#define PAGE_FLAGS      (1 << PG_lru   | 1 << PG_private   | 1 << PG_locked | \
 376                         1 << PG_buddy | 1 << PG_writeback | \
 377                         1 << PG_slab  | 1 << PG_swapcache | 1 << PG_active | \
 378                         __PG_UNEVICTABLE | __PG_MLOCKED)
 379
 380/*
 381 * Flags checked in bad_page().  Pages on the free list should not have
 382 * these flags set.  It they are, there is a problem.
 383 */
 384#define PAGE_FLAGS_CLEAR_WHEN_BAD (PAGE_FLAGS | \
 385                1 << PG_reclaim | 1 << PG_dirty | 1 << PG_swapbacked)
 386
 387/*
 388 * Flags checked when a page is freed.  Pages being freed should not have
 389 * these flags set.  It they are, there is a problem.
 390 */
 391#define PAGE_FLAGS_CHECK_AT_FREE (PAGE_FLAGS | 1 << PG_reserved)
 392
 393/*
 394 * Flags checked when a page is prepped for return by the page allocator.
 395 * Pages being prepped should not have these flags set.  It they are, there
 396 * is a problem.
 397 */
 398#define PAGE_FLAGS_CHECK_AT_PREP (PAGE_FLAGS | \
 399                1 << PG_reserved | 1 << PG_dirty | 1 << PG_swapbacked)
 400
 401#endif /* !__GENERATING_BOUNDS_H */
 402#endif  /* PAGE_FLAGS_H */
 403
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