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 #define __TESTCLEARFLAG(uname, lname)                                   \
 168 static inline int __TestClearPage##uname(struct page *page)             \
 169                 { return __test_and_clear_bit(PG_##lname, &page->flags); }
 170
 171 #define PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)               \
 172         SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname)
 173
 174 #define __PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)             \
 175         __SETPAGEFLAG(uname, lname)  __CLEARPAGEFLAG(uname, lname)
 176
 177 #define PAGEFLAG_FALSE(uname)                                           \
 178 static inline int Page##uname(struct page *page)                        \
 179                         { return 0; }
 180
 181 #define TESTSCFLAG(uname, lname)                                        \
 182         TESTSETFLAG(uname, lname) TESTCLEARFLAG(uname, lname)
 183
 184 #define SETPAGEFLAG_NOOP(uname)                                         \
 185 static inline void SetPage##uname(struct page *page) {  }
 186
 187 #define CLEARPAGEFLAG_NOOP(uname)                                       \
 188 static inline void ClearPage##uname(struct page *page) {  }
 189
 190 #define __CLEARPAGEFLAG_NOOP(uname)                                     \
 191 static inline void __ClearPage##uname(struct page *page) {  }
 192
 193 #define TESTCLEARFLAG_FALSE(uname)                                      \
 194 static inline int TestClearPage##uname(struct page *page) { return 0; }
 195
 196 #define __TESTCLEARFLAG_FALSE(uname)                                    \
 197 static inline int __TestClearPage##uname(struct page *page) { return 0; }
 198
 199 struct page;    /* forward declaration */
 200
 201 TESTPAGEFLAG(Locked, locked) TESTSETFLAG(Locked, locked)
 202 PAGEFLAG(Error, error)
 203 PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced)
 204 PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty, dirty)
 205 PAGEFLAG(LRU, lru) __CLEARPAGEFLAG(LRU, lru)
 206 PAGEFLAG(Active, active) __CLEARPAGEFLAG(Active, active)
 207         TESTCLEARFLAG(Active, active)
 208 __PAGEFLAG(Slab, slab)
 209 PAGEFLAG(Checked, checked)              /* Used by some filesystems */
 210 PAGEFLAG(Pinned, pinned) TESTSCFLAG(Pinned, pinned)     /* Xen */
 211 PAGEFLAG(SavePinned, savepinned);                       /* Xen */
 212 PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
 213 PAGEFLAG(SwapBacked, swapbacked) __CLEARPAGEFLAG(SwapBacked, swapbacked)
 214
 215 __PAGEFLAG(SlobFree, slob_free)
 216
 217 __PAGEFLAG(SlubFrozen, slub_frozen)
 218 __PAGEFLAG(SlubDebug, slub_debug)
 219
 220 /*
 221  * Private page markings that may be used by the filesystem that owns the page
 222  * for its own purposes.
 223  * - PG_private and PG_private_2 cause releasepage() and co to be invoked
 224  */
 225 PAGEFLAG(Private, private) __SETPAGEFLAG(Private, private)
 226         __CLEARPAGEFLAG(Private, private)
 227 PAGEFLAG(Private2, private_2) TESTSCFLAG(Private2, private_2)
 228 PAGEFLAG(OwnerPriv1, owner_priv_1) TESTCLEARFLAG(OwnerPriv1, owner_priv_1)
 229
 230 /*
 231  * Only test-and-set exist for PG_writeback.  The unconditional operators are
 232  * risky: they bypass page accounting.
 233  */
 234 TESTPAGEFLAG(Writeback, writeback) TESTSCFLAG(Writeback, writeback)
 235 __PAGEFLAG(Buddy, buddy)
 236 PAGEFLAG(MappedToDisk, mappedtodisk)
 237
 238 /* PG_readahead is only used for file reads; PG_reclaim is only for writes */
 239 PAGEFLAG(Reclaim, reclaim) TESTCLEARFLAG(Reclaim, reclaim)
 240 PAGEFLAG(Readahead, reclaim)            /* Reminder to do async read-ahead */
 241
 242 #ifdef CONFIG_HIGHMEM
 243 /*
 244  * Must use a macro here due to header dependency issues. page_zone() is not
 245  * available at this point.
 246  */
 247 #define PageHighMem(__p) is_highmem(page_zone(__p))
 248 #else
 249 PAGEFLAG_FALSE(HighMem)
 250 #endif
 251
 252 #ifdef CONFIG_SWAP
 253 PAGEFLAG(SwapCache, swapcache)
 254 #else
 255 PAGEFLAG_FALSE(SwapCache)
 256         SETPAGEFLAG_NOOP(SwapCache) CLEARPAGEFLAG_NOOP(SwapCache)
 257 #endif
 258
 259 PAGEFLAG(Unevictable, unevictable) __CLEARPAGEFLAG(Unevictable, unevictable)
 260         TESTCLEARFLAG(Unevictable, unevictable)
 261
 262 #ifdef CONFIG_HAVE_MLOCKED_PAGE_BIT
 263 #define MLOCK_PAGES 1
 264 PAGEFLAG(Mlocked, mlocked) __CLEARPAGEFLAG(Mlocked, mlocked)
 265         TESTSCFLAG(Mlocked, mlocked) __TESTCLEARFLAG(Mlocked, mlocked)
 266 #else
 267 #define MLOCK_PAGES 0
 268 PAGEFLAG_FALSE(Mlocked) SETPAGEFLAG_NOOP(Mlocked)
 269         TESTCLEARFLAG_FALSE(Mlocked) __TESTCLEARFLAG_FALSE(Mlocked)
 270 #endif
 271
 272 #ifdef CONFIG_ARCH_USES_PG_UNCACHED
 273 PAGEFLAG(Uncached, uncached)
 274 #else
 275 PAGEFLAG_FALSE(Uncached)
 276 #endif
 277
 278 #ifdef CONFIG_MEMORY_FAILURE
 279 PAGEFLAG(HWPoison, hwpoison)
 280 TESTSETFLAG(HWPoison, hwpoison)
 281 #define __PG_HWPOISON (1UL << PG_hwpoison)
 282 #else
 283 PAGEFLAG_FALSE(HWPoison)
 284 #define __PG_HWPOISON 0
 285 #endif
 286
 287 static inline int PageUptodate(struct page *page)
 288 {
 289         int ret = test_bit(PG_uptodate, &(page)->flags);
 290
 291         /*
 292          * Must ensure that the data we read out of the page is loaded
 293          * _after_ we've loaded page->flags to check for PageUptodate.
 294          * We can skip the barrier if the page is not uptodate, because
 295          * we wouldn't be reading anything from it.
 296          *
 297          * See SetPageUptodate() for the other side of the story.
 298          */
 299         if (ret)
 300                 smp_rmb();
 301
 302         return ret;
 303 }
 304
 305 static inline void __SetPageUptodate(struct page *page)
 306 {
 307         smp_wmb();
 308         __set_bit(PG_uptodate, &(page)->flags);
 309 }
 310
 311 static inline void SetPageUptodate(struct page *page)
 312 {
 313 #ifdef CONFIG_S390
 314         if (!test_and_set_bit(PG_uptodate, &page->flags))
 315                 page_clear_dirty(page);
 316 #else
 317         /*
 318          * Memory barrier must be issued before setting the PG_uptodate bit,
 319          * so that all previous stores issued in order to bring the page
 320          * uptodate are actually visible before PageUptodate becomes true.
 321          *
 322          * s390 doesn't need an explicit smp_wmb here because the test and
 323          * set bit already provides full barriers.
 324          */
 325         smp_wmb();
 326         set_bit(PG_uptodate, &(page)->flags);
 327 #endif
 328 }
 329
 330 CLEARPAGEFLAG(Uptodate, uptodate)
 331
 332 extern void cancel_dirty_page(struct page *page, unsigned int account_size);
 333
 334 int test_clear_page_writeback(struct page *page);
 335 int test_set_page_writeback(struct page *page);
 336
 337 static inline void set_page_writeback(struct page *page)
 338 {
 339         test_set_page_writeback(page);
 340 }
 341
 342 #ifdef CONFIG_PAGEFLAGS_EXTENDED
 343 /*
 344  * System with lots of page flags available. This allows separate
 345  * flags for PageHead() and PageTail() checks of compound pages so that bit
 346  * tests can be used in performance sensitive paths. PageCompound is
 347  * generally not used in hot code paths.
 348  */
 349 __PAGEFLAG(Head, head)
 350 __PAGEFLAG(Tail, tail)
 351
 352 static inline int PageCompound(struct page *page)
 353 {
 354         return page->flags & ((1L << PG_head) | (1L << PG_tail));
 355
 356 }
 357 #else
 358 /*
 359  * Reduce page flag use as much as possible by overlapping
 360  * compound page flags with the flags used for page cache pages. Possible
 361  * because PageCompound is always set for compound pages and not for
 362  * pages on the LRU and/or pagecache.
 363  */
 364 TESTPAGEFLAG(Compound, compound)
 365 __PAGEFLAG(Head, compound)
 366
 367 /*
 368  * PG_reclaim is used in combination with PG_compound to mark the
 369  * head and tail of a compound page. This saves one page flag
 370  * but makes it impossible to use compound pages for the page cache.
 371  * The PG_reclaim bit would have to be used for reclaim or readahead
 372  * if compound pages enter the page cache.
 373  *
 374  * PG_compound & PG_reclaim     => Tail page
 375  * PG_compound & ~PG_reclaim    => Head page
 376  */
 377 #define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))
 378
 379 static inline int PageTail(struct page *page)
 380 {
 381         return ((page->flags & PG_head_tail_mask) == PG_head_tail_mask);
 382 }
 383
 384 static inline void __SetPageTail(struct page *page)
 385 {
 386         page->flags |= PG_head_tail_mask;
 387 }
 388
 389 static inline void __ClearPageTail(struct page *page)
 390 {
 391         page->flags &= ~PG_head_tail_mask;
 392 }
 393
 394 #endif /* !PAGEFLAGS_EXTENDED */
 395
 396 #ifdef CONFIG_HAVE_MLOCKED_PAGE_BIT
 397 #define __PG_MLOCKED            (1 << PG_mlocked)
 398 #else
 399 #define __PG_MLOCKED            0
 400 #endif
 401
 402 /*
 403  * Flags checked when a page is freed.  Pages being freed should not have
 404  * these flags set.  It they are, there is a problem.
 405  */
 406 #define PAGE_FLAGS_CHECK_AT_FREE \
 407         (1 << PG_lru     | 1 << PG_locked    | \
 408          1 << PG_private | 1 << PG_private_2 | \
 409          1 << PG_buddy   | 1 << PG_writeback | 1 << PG_reserved | \
 410          1 << PG_slab    | 1 << PG_swapcache | 1 << PG_active | \
 411          1 << PG_unevictable | __PG_MLOCKED | __PG_HWPOISON)
 412
 413 /*
 414  * Flags checked when a page is prepped for return by the page allocator.
 415  * Pages being prepped should not have any flags set.  It they are set,
 416  * there has been a kernel bug or struct page corruption.
 417  */
 418 #define PAGE_FLAGS_CHECK_AT_PREP        ((1 << NR_PAGEFLAGS) - 1)
 419
 420 #define PAGE_FLAGS_PRIVATE                              \
 421         (1 << PG_private | 1 << PG_private_2)
 422 /**
 423  * page_has_private - Determine if page has private stuff
 424  * @page: The page to be checked
 425  *
 426  * Determine if a page has private stuff, indicating that release routines
 427  * should be invoked upon it.
 428  */
 429 static inline int page_has_private(struct page *page)
 430 {
 431         return !!(page->flags & PAGE_FLAGS_PRIVATE);
 432 }
 433
 434 #endif /* !__GENERATING_BOUNDS_H */
 435
 436 #endif  /* PAGE_FLAGS_H */