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