include/linux/pagemap.h

   1 #ifndef _LINUX_PAGEMAP_H
   2 #define _LINUX_PAGEMAP_H
   3
   4 /*
   5  * Copyright 1995 Linus Torvalds
   6  */
   7 #include <linux/mm.h>
   8 #include <linux/fs.h>
   9 #include <linux/list.h>
  10 #include <linux/highmem.h>
  11 #include <linux/compiler.h>
  12 #include <asm/uaccess.h>
  13 #include <linux/gfp.h>
  14
  15 /*
  16  * Bits in mapping->flags.  The lower __GFP_BITS_SHIFT bits are the page
  17  * allocation mode flags.
  18  */
  19 #define AS_EIO          (__GFP_BITS_SHIFT + 0)  /* IO error on async write */
  20 #define AS_ENOSPC       (__GFP_BITS_SHIFT + 1)  /* ENOSPC on async write */
  21
  22 static inline gfp_t mapping_gfp_mask(struct address_space * mapping)
  23 {
  24         return (__force gfp_t)mapping->flags & __GFP_BITS_MASK;
  25 }
  26
  27 /*
  28  * This is non-atomic.  Only to be used before the mapping is activated.
  29  * Probably needs a barrier...
  30  */
  31 static inline void mapping_set_gfp_mask(struct address_space *m, gfp_t mask)
  32 {
  33         m->flags = (m->flags & ~(__force unsigned long)__GFP_BITS_MASK) |
  34                                 (__force unsigned long)mask;
  35 }
  36
  37 /*
  38  * The page cache can done in larger chunks than
  39  * one page, because it allows for more efficient
  40  * throughput (it can then be mapped into user
  41  * space in smaller chunks for same flexibility).
  42  *
  43  * Or rather, it _will_ be done in larger chunks.
  44  */
  45 #define PAGE_CACHE_SHIFT        PAGE_SHIFT
  46 #define PAGE_CACHE_SIZE         PAGE_SIZE
  47 #define PAGE_CACHE_MASK         PAGE_MASK
  48 #define PAGE_CACHE_ALIGN(addr)  (((addr)+PAGE_CACHE_SIZE-1)&PAGE_CACHE_MASK)
  49
  50 #define page_cache_get(page)            get_page(page)
  51 #define page_cache_release(page)        put_page(page)
  52 void release_pages(struct page **pages, int nr, int cold);
  53
  54 #ifdef CONFIG_NUMA
  55 extern struct page *page_cache_alloc(struct address_space *x);
  56 extern struct page *page_cache_alloc_cold(struct address_space *x);
  57 #else
  58 static inline struct page *page_cache_alloc(struct address_space *x)
  59 {
  60         return alloc_pages(mapping_gfp_mask(x), 0);
  61 }
  62
  63 static inline struct page *page_cache_alloc_cold(struct address_space *x)
  64 {
  65         return alloc_pages(mapping_gfp_mask(x)|__GFP_COLD, 0);
  66 }
  67 #endif
  68
  69 typedef int filler_t(void *, struct page *);
  70
  71 extern struct page * find_get_page(struct address_space *mapping,
  72                                 unsigned long index);
  73 extern struct page * find_lock_page(struct address_space *mapping,
  74                                 unsigned long index);
  75 extern __deprecated_for_modules struct page * find_trylock_page(
  76                         struct address_space *mapping, unsigned long index);
  77 extern struct page * find_or_create_page(struct address_space *mapping,
  78                                 unsigned long index, gfp_t gfp_mask);
  79 unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
  80                         unsigned int nr_pages, struct page **pages);
  81 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t start,
  82                                unsigned int nr_pages, struct page **pages);
  83 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
  84                         int tag, unsigned int nr_pages, struct page **pages);
  85
  86 /*
  87  * Returns locked page at given index in given cache, creating it if needed.
  88  */
  89 static inline struct page *grab_cache_page(struct address_space *mapping, unsigned long index)
  90 {
  91         return find_or_create_page(mapping, index, mapping_gfp_mask(mapping));
  92 }
  93
  94 extern struct page * grab_cache_page_nowait(struct address_space *mapping,
  95                                 unsigned long index);
  96 extern struct page * read_cache_page(struct address_space *mapping,
  97                                 unsigned long index, filler_t *filler,
  98                                 void *data);
  99 extern int read_cache_pages(struct address_space *mapping,
 100                 struct list_head *pages, filler_t *filler, void *data);
 101
 102 static inline struct page *read_mapping_page(struct address_space *mapping,
 103                                              unsigned long index, void *data)
 104 {
 105         filler_t *filler = (filler_t *)mapping->a_ops->readpage;
 106         return read_cache_page(mapping, index, filler, data);
 107 }
 108
 109 int add_to_page_cache(struct page *page, struct address_space *mapping,
 110                                 unsigned long index, gfp_t gfp_mask);
 111 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
 112                                 unsigned long index, gfp_t gfp_mask);
 113 extern void remove_from_page_cache(struct page *page);
 114 extern void __remove_from_page_cache(struct page *page);
 115
 116 extern atomic_t nr_pagecache;
 117
 118 #ifdef CONFIG_SMP
 119
 120 #define PAGECACHE_ACCT_THRESHOLD        max(16, NR_CPUS * 2)
 121 DECLARE_PER_CPU(long, nr_pagecache_local);
 122
 123 /*
 124  * pagecache_acct implements approximate accounting for pagecache.
 125  * vm_enough_memory() do not need high accuracy. Writers will keep
 126  * an offset in their per-cpu arena and will spill that into the
 127  * global count whenever the absolute value of the local count
 128  * exceeds the counter's threshold.
 129  *
 130  * MUST be protected from preemption.
 131  * current protection is mapping->page_lock.
 132  */
 133 static inline void pagecache_acct(int count)
 134 {
 135         long *local;
 136
 137         local = &__get_cpu_var(nr_pagecache_local);
 138         *local += count;
 139         if (*local > PAGECACHE_ACCT_THRESHOLD || *local < -PAGECACHE_ACCT_THRESHOLD) {
 140                 atomic_add(*local, &nr_pagecache);
 141                 *local = 0;
 142         }
 143 }
 144
 145 #else
 146
 147 static inline void pagecache_acct(int count)
 148 {
 149         atomic_add(count, &nr_pagecache);
 150 }
 151 #endif
 152
 153 static inline unsigned long get_page_cache_size(void)
 154 {
 155         int ret = atomic_read(&nr_pagecache);
 156         if (unlikely(ret < 0))
 157                 ret = 0;
 158         return ret;
 159 }
 160
 161 /*
 162  * Return byte-offset into filesystem object for page.
 163  */
 164 static inline loff_t page_offset(struct page *page)
 165 {
 166         return ((loff_t)page->index) << PAGE_CACHE_SHIFT;
 167 }
 168
 169 static inline pgoff_t linear_page_index(struct vm_area_struct *vma,
 170                                         unsigned long address)
 171 {
 172         pgoff_t pgoff = (address - vma->vm_start) >> PAGE_SHIFT;
 173         pgoff += vma->vm_pgoff;
 174         return pgoff >> (PAGE_CACHE_SHIFT - PAGE_SHIFT);
 175 }
 176
 177 extern void FASTCALL(__lock_page(struct page *page));
 178 extern void FASTCALL(unlock_page(struct page *page));
 179
 180 static inline void lock_page(struct page *page)
 181 {
 182         might_sleep();
 183         if (TestSetPageLocked(page))
 184                 __lock_page(page);
 185 }
 186
 187 /*
 188  * This is exported only for wait_on_page_locked/wait_on_page_writeback.
 189  * Never use this directly!
 190  */
 191 extern void FASTCALL(wait_on_page_bit(struct page *page, int bit_nr));
 192
 193 /*
 194  * Wait for a page to be unlocked.
 195  *
 196  * This must be called with the caller "holding" the page,
 197  * ie with increased "page->count" so that the page won't
 198  * go away during the wait..
 199  */
 200 static inline void wait_on_page_locked(struct page *page)
 201 {
 202         if (PageLocked(page))
 203                 wait_on_page_bit(page, PG_locked);
 204 }
 205
 206 /*
 207  * Wait for a page to complete writeback
 208  */
 209 static inline void wait_on_page_writeback(struct page *page)
 210 {
 211         if (PageWriteback(page))
 212                 wait_on_page_bit(page, PG_writeback);
 213 }
 214
 215 extern void end_page_writeback(struct page *page);
 216
 217 /*
 218  * Fault a userspace page into pagetables.  Return non-zero on a fault.
 219  *
 220  * This assumes that two userspace pages are always sufficient.  That's
 221  * not true if PAGE_CACHE_SIZE > PAGE_SIZE.
 222  */
 223 static inline int fault_in_pages_writeable(char __user *uaddr, int size)
 224 {
 225         int ret;
 226
 227         /*
 228          * Writing zeroes into userspace here is OK, because we know that if
 229          * the zero gets there, we'll be overwriting it.
 230          */
 231         ret = __put_user(0, uaddr);
 232         if (ret == 0) {
 233                 char __user *end = uaddr + size - 1;
 234
 235                 /*
 236                  * If the page was already mapped, this will get a cache miss
 237                  * for sure, so try to avoid doing it.
 238                  */
 239                 if (((unsigned long)uaddr & PAGE_MASK) !=
 240                                 ((unsigned long)end & PAGE_MASK))
 241                         ret = __put_user(0, end);
 242         }
 243         return ret;
 244 }
 245
 246 static inline void fault_in_pages_readable(const char __user *uaddr, int size)
 247 {
 248         volatile char c;
 249         int ret;
 250
 251         ret = __get_user(c, uaddr);
 252         if (ret == 0) {
 253                 const char __user *end = uaddr + size - 1;
 254
 255                 if (((unsigned long)uaddr & PAGE_MASK) !=
 256                                 ((unsigned long)end & PAGE_MASK))
 257                         __get_user(c, end);
 258         }
 259 }
 260
 261 #endif /* _LINUX_PAGEMAP_H */