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 int add_to_page_cache(struct page *page, struct address_space *mapping,
 103                                 unsigned long index, gfp_t gfp_mask);
 104 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
 105                                 unsigned long index, gfp_t gfp_mask);
 106 extern void remove_from_page_cache(struct page *page);
 107 extern void __remove_from_page_cache(struct page *page);
 108
 109 extern atomic_t nr_pagecache;
 110
 111 #ifdef CONFIG_SMP
 112
 113 #define PAGECACHE_ACCT_THRESHOLD        max(16, NR_CPUS * 2)
 114 DECLARE_PER_CPU(long, nr_pagecache_local);
 115
 116 /*
 117  * pagecache_acct implements approximate accounting for pagecache.
 118  * vm_enough_memory() do not need high accuracy. Writers will keep
 119  * an offset in their per-cpu arena and will spill that into the
 120  * global count whenever the absolute value of the local count
 121  * exceeds the counter's threshold.
 122  *
 123  * MUST be protected from preemption.
 124  * current protection is mapping->page_lock.
 125  */
 126 static inline void pagecache_acct(int count)
 127 {
 128         long *local;
 129
 130         local = &__get_cpu_var(nr_pagecache_local);
 131         *local += count;
 132         if (*local > PAGECACHE_ACCT_THRESHOLD || *local < -PAGECACHE_ACCT_THRESHOLD) {
 133                 atomic_add(*local, &nr_pagecache);
 134                 *local = 0;
 135         }
 136 }
 137
 138 #else
 139
 140 static inline void pagecache_acct(int count)
 141 {
 142         atomic_add(count, &nr_pagecache);
 143 }
 144 #endif
 145
 146 static inline unsigned long get_page_cache_size(void)
 147 {
 148         int ret = atomic_read(&nr_pagecache);
 149         if (unlikely(ret < 0))
 150                 ret = 0;
 151         return ret;
 152 }
 153
 154 /*
 155  * Return byte-offset into filesystem object for page.
 156  */
 157 static inline loff_t page_offset(struct page *page)
 158 {
 159         return ((loff_t)page->index) << PAGE_CACHE_SHIFT;
 160 }
 161
 162 static inline pgoff_t linear_page_index(struct vm_area_struct *vma,
 163                                         unsigned long address)
 164 {
 165         pgoff_t pgoff = (address - vma->vm_start) >> PAGE_SHIFT;
 166         pgoff += vma->vm_pgoff;
 167         return pgoff >> (PAGE_CACHE_SHIFT - PAGE_SHIFT);
 168 }
 169
 170 extern void FASTCALL(__lock_page(struct page *page));
 171 extern void FASTCALL(unlock_page(struct page *page));
 172
 173 static inline void lock_page(struct page *page)
 174 {
 175         might_sleep();
 176         if (TestSetPageLocked(page))
 177                 __lock_page(page);
 178 }
 179
 180 /*
 181  * This is exported only for wait_on_page_locked/wait_on_page_writeback.
 182  * Never use this directly!
 183  */
 184 extern void FASTCALL(wait_on_page_bit(struct page *page, int bit_nr));
 185
 186 /*
 187  * Wait for a page to be unlocked.
 188  *
 189  * This must be called with the caller "holding" the page,
 190  * ie with increased "page->count" so that the page won't
 191  * go away during the wait..
 192  */
 193 static inline void wait_on_page_locked(struct page *page)
 194 {
 195         if (PageLocked(page))
 196                 wait_on_page_bit(page, PG_locked);
 197 }
 198
 199 /*
 200  * Wait for a page to complete writeback
 201  */
 202 static inline void wait_on_page_writeback(struct page *page)
 203 {
 204         if (PageWriteback(page))
 205                 wait_on_page_bit(page, PG_writeback);
 206 }
 207
 208 extern void end_page_writeback(struct page *page);
 209
 210 /*
 211  * Fault a userspace page into pagetables.  Return non-zero on a fault.
 212  *
 213  * This assumes that two userspace pages are always sufficient.  That's
 214  * not true if PAGE_CACHE_SIZE > PAGE_SIZE.
 215  */
 216 static inline int fault_in_pages_writeable(char __user *uaddr, int size)
 217 {
 218         int ret;
 219
 220         /*
 221          * Writing zeroes into userspace here is OK, because we know that if
 222          * the zero gets there, we'll be overwriting it.
 223          */
 224         ret = __put_user(0, uaddr);
 225         if (ret == 0) {
 226                 char __user *end = uaddr + size - 1;
 227
 228                 /*
 229                  * If the page was already mapped, this will get a cache miss
 230                  * for sure, so try to avoid doing it.
 231                  */
 232                 if (((unsigned long)uaddr & PAGE_MASK) !=
 233                                 ((unsigned long)end & PAGE_MASK))
 234                         ret = __put_user(0, end);
 235         }
 236         return ret;
 237 }
 238
 239 static inline void fault_in_pages_readable(const char __user *uaddr, int size)
 240 {
 241         volatile char c;
 242         int ret;
 243
 244         ret = __get_user(c, uaddr);
 245         if (ret == 0) {
 246                 const char __user *end = uaddr + size - 1;
 247
 248                 if (((unsigned long)uaddr & PAGE_MASK) !=
 249                                 ((unsigned long)end & PAGE_MASK))
 250                         __get_user(c, end);
 251         }
 252 }
 253
 254 #endif /* _LINUX_PAGEMAP_H */