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         PG_compound,            /* A compound page */
  87         PG_swapcache,           /* Swap page: swp_entry_t in private */
  88         PG_mappedtodisk,        /* Has blocks allocated on-disk */
  89         PG_reclaim,             /* To be reclaimed asap */
  90         PG_buddy,               /* Page is free, on buddy lists */
  91 #ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
  92         PG_uncached,            /* Page has been mapped as uncached */
  93 #endif
  94         __NR_PAGEFLAGS
  95 };
  96
  97 #ifndef __GENERATING_BOUNDS_H
  98
  99 /*
 100  * Macros to create function definitions for page flags
 101  */
 102 #define TESTPAGEFLAG(uname, lname)                                      \
 103 static inline int Page##uname(struct page *page)                        \
 104                         { return test_bit(PG_##lname, &page->flags); }
 105
 106 #define SETPAGEFLAG(uname, lname)                                       \
 107 static inline void SetPage##uname(struct page *page)                    \
 108                         { set_bit(PG_##lname, &page->flags); }
 109
 110 #define CLEARPAGEFLAG(uname, lname)                                     \
 111 static inline void ClearPage##uname(struct page *page)                  \
 112                         { clear_bit(PG_##lname, &page->flags); }
 113
 114 #define __SETPAGEFLAG(uname, lname)                                     \
 115 static inline void __SetPage##uname(struct page *page)                  \
 116                         { __set_bit(PG_##lname, &page->flags); }
 117
 118 #define __CLEARPAGEFLAG(uname, lname)                                   \
 119 static inline void __ClearPage##uname(struct page *page)                \
 120                         { __clear_bit(PG_##lname, &page->flags); }
 121
 122 #define TESTSETFLAG(uname, lname)                                       \
 123 static inline int TestSetPage##uname(struct page *page)                 \
 124                 { return test_and_set_bit(PG_##lname, &page->flags); }
 125
 126 #define TESTCLEARFLAG(uname, lname)                                     \
 127 static inline int TestClearPage##uname(struct page *page)               \
 128                 { return test_and_clear_bit(PG_##lname, &page->flags); }
 129
 130
 131 #define PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)               \
 132         SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname)
 133
 134 #define __PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)             \
 135         __SETPAGEFLAG(uname, lname)  __CLEARPAGEFLAG(uname, lname)
 136
 137 #define PAGEFLAG_FALSE(uname)                                           \
 138 static inline int Page##uname(struct page *page)                        \
 139                         { return 0; }
 140
 141 #define TESTSCFLAG(uname, lname)                                        \
 142         TESTSETFLAG(uname, lname) TESTCLEARFLAG(uname, lname)
 143
 144 struct page;    /* forward declaration */
 145
 146 PAGEFLAG(Locked, locked) TESTSCFLAG(Locked, locked)
 147 PAGEFLAG(Error, error)
 148 PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced)
 149 PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty, dirty)
 150 PAGEFLAG(LRU, lru) __CLEARPAGEFLAG(LRU, lru)
 151 PAGEFLAG(Active, active) __CLEARPAGEFLAG(Active, active)
 152 __PAGEFLAG(Slab, slab)
 153 PAGEFLAG(Checked, owner_priv_1)         /* Used by some filesystems */
 154 PAGEFLAG(Pinned, owner_priv_1) TESTSCFLAG(Pinned, owner_priv_1) /* Xen */
 155 PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
 156 PAGEFLAG(Private, private) __CLEARPAGEFLAG(Private, private)
 157         __SETPAGEFLAG(Private, private)
 158
 159 /*
 160  * Only test-and-set exist for PG_writeback.  The unconditional operators are
 161  * risky: they bypass page accounting.
 162  */
 163 TESTPAGEFLAG(Writeback, writeback) TESTSCFLAG(Writeback, writeback)
 164 __PAGEFLAG(Buddy, buddy)
 165 PAGEFLAG(MappedToDisk, mappedtodisk)
 166
 167 /* PG_readahead is only used for file reads; PG_reclaim is only for writes */
 168 PAGEFLAG(Reclaim, reclaim) TESTCLEARFLAG(Reclaim, reclaim)
 169 PAGEFLAG(Readahead, reclaim)            /* Reminder to do async read-ahead */
 170
 171 #ifdef CONFIG_HIGHMEM
 172 /*
 173  * Must use a macro here due to header dependency issues. page_zone() is not
 174  * available at this point.
 175  */
 176 #define PageHighMem(__p) is_highmem(page_zone(__p))
 177 #else
 178 PAGEFLAG_FALSE(HighMem)
 179 #endif
 180
 181 #ifdef CONFIG_SWAP
 182 PAGEFLAG(SwapCache, swapcache)
 183 #else
 184 PAGEFLAG_FALSE(SwapCache)
 185 #endif
 186
 187 #ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
 188 PAGEFLAG(Uncached, uncached)
 189 #else
 190 PAGEFLAG_FALSE(Uncached)
 191 #endif
 192
 193 static inline int PageUptodate(struct page *page)
 194 {
 195         int ret = test_bit(PG_uptodate, &(page)->flags);
 196
 197         /*
 198          * Must ensure that the data we read out of the page is loaded
 199          * _after_ we've loaded page->flags to check for PageUptodate.
 200          * We can skip the barrier if the page is not uptodate, because
 201          * we wouldn't be reading anything from it.
 202          *
 203          * See SetPageUptodate() for the other side of the story.
 204          */
 205         if (ret)
 206                 smp_rmb();
 207
 208         return ret;
 209 }
 210
 211 static inline void __SetPageUptodate(struct page *page)
 212 {
 213         smp_wmb();
 214         __set_bit(PG_uptodate, &(page)->flags);
 215 #ifdef CONFIG_S390
 216         page_clear_dirty(page);
 217 #endif
 218 }
 219
 220 static inline void SetPageUptodate(struct page *page)
 221 {
 222 #ifdef CONFIG_S390
 223         if (!test_and_set_bit(PG_uptodate, &page->flags))
 224                 page_clear_dirty(page);
 225 #else
 226         /*
 227          * Memory barrier must be issued before setting the PG_uptodate bit,
 228          * so that all previous stores issued in order to bring the page
 229          * uptodate are actually visible before PageUptodate becomes true.
 230          *
 231          * s390 doesn't need an explicit smp_wmb here because the test and
 232          * set bit already provides full barriers.
 233          */
 234         smp_wmb();
 235         set_bit(PG_uptodate, &(page)->flags);
 236 #endif
 237 }
 238
 239 CLEARPAGEFLAG(Uptodate, uptodate)
 240
 241 extern void cancel_dirty_page(struct page *page, unsigned int account_size);
 242
 243 int test_clear_page_writeback(struct page *page);
 244 int test_set_page_writeback(struct page *page);
 245
 246 static inline void set_page_writeback(struct page *page)
 247 {
 248         test_set_page_writeback(page);
 249 }
 250
 251 TESTPAGEFLAG(Compound, compound)
 252 __PAGEFLAG(Head, compound)
 253
 254 /*
 255  * PG_reclaim is used in combination with PG_compound to mark the
 256  * head and tail of a compound page. This saves one page flag
 257  * but makes it impossible to use compound pages for the page cache.
 258  * The PG_reclaim bit would have to be used for reclaim or readahead
 259  * if compound pages enter the page cache.
 260  *
 261  * PG_compound & PG_reclaim     => Tail page
 262  * PG_compound & ~PG_reclaim    => Head page
 263  */
 264 #define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))
 265
 266 static inline int PageTail(struct page *page)
 267 {
 268         return ((page->flags & PG_head_tail_mask) == PG_head_tail_mask);
 269 }
 270
 271 static inline void __SetPageTail(struct page *page)
 272 {
 273         page->flags |= PG_head_tail_mask;
 274 }
 275
 276 static inline void __ClearPageTail(struct page *page)
 277 {
 278         page->flags &= ~PG_head_tail_mask;
 279 }
 280
 281 #endif /* !__GENERATING_BOUNDS_H */
 282 #endif  /* PAGE_FLAGS_H */