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 static inline struct page *page_cache_alloc(struct address_space *x)
  55 {
  56         return alloc_pages(mapping_gfp_mask(x), 0);
  57 }
  58
  59 static inline struct page *page_cache_alloc_cold(struct address_space *x)
  60 {
  61         return alloc_pages(mapping_gfp_mask(x)|__GFP_COLD, 0);
  62 }
  63
  64 typedef int filler_t(void *, struct page *);
  65
  66 extern struct page * find_get_page(struct address_space *mapping,
  67                                 unsigned long index);
  68 extern struct page * find_lock_page(struct address_space *mapping,
  69                                 unsigned long index);
  70 extern struct page * find_trylock_page(struct address_space *mapping,
  71                                 unsigned long index);
  72 extern struct page * find_or_create_page(struct address_space *mapping,
  73                                 unsigned long index, gfp_t gfp_mask);
  74 unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
  75                         unsigned int nr_pages, struct page **pages);
  76 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
  77                         int tag, unsigned int nr_pages, struct page **pages);
  78
  79 /*
  80  * Returns locked page at given index in given cache, creating it if needed.
  81  */
  82 static inline struct page *grab_cache_page(struct address_space *mapping, unsigned long index)
  83 {
  84         return find_or_create_page(mapping, index, mapping_gfp_mask(mapping));
  85 }
  86
  87 extern struct page * grab_cache_page_nowait(struct address_space *mapping,
  88                                 unsigned long index);
  89 extern struct page * read_cache_page(struct address_space *mapping,
  90                                 unsigned long index, filler_t *filler,
  91                                 void *data);
  92 extern int read_cache_pages(struct address_space *mapping,
  93                 struct list_head *pages, filler_t *filler, void *data);
  94
  95 int add_to_page_cache(struct page *page, struct address_space *mapping,
  96                                 unsigned long index, gfp_t gfp_mask);
  97 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
  98                                 unsigned long index, gfp_t gfp_mask);
  99 extern void remove_from_page_cache(struct page *page);
 100 extern void __remove_from_page_cache(struct page *page);
 101
 102 extern atomic_t nr_pagecache;
 103
 104 #ifdef CONFIG_SMP
 105
 106 #define PAGECACHE_ACCT_THRESHOLD        max(16, NR_CPUS * 2)
 107 DECLARE_PER_CPU(long, nr_pagecache_local);
 108
 109 /*
 110  * pagecache_acct implements approximate accounting for pagecache.
 111  * vm_enough_memory() do not need high accuracy. Writers will keep
 112  * an offset in their per-cpu arena and will spill that into the
 113  * global count whenever the absolute value of the local count
 114  * exceeds the counter's threshold.
 115  *
 116  * MUST be protected from preemption.
 117  * current protection is mapping->page_lock.
 118  */
 119 static inline void pagecache_acct(int count)
 120 {
 121         long *local;
 122
 123         local = &__get_cpu_var(nr_pagecache_local);
 124         *local += count;
 125         if (*local > PAGECACHE_ACCT_THRESHOLD || *local < -PAGECACHE_ACCT_THRESHOLD) {
 126                 atomic_add(*local, &nr_pagecache);
 127                 *local = 0;
 128         }
 129 }
 130
 131 #else
 132
 133 static inline void pagecache_acct(int count)
 134 {
 135         atomic_add(count, &nr_pagecache);
 136 }
 137 #endif
 138
 139 static inline unsigned long get_page_cache_size(void)
 140 {
 141         int ret = atomic_read(&nr_pagecache);
 142         if (unlikely(ret < 0))
 143                 ret = 0;
 144         return ret;
 145 }
 146
 147 /*
 148  * Return byte-offset into filesystem object for page.
 149  */
 150 static inline loff_t page_offset(struct page *page)
 151 {
 152         return ((loff_t)page->index) << PAGE_CACHE_SHIFT;
 153 }
 154
 155 static inline pgoff_t linear_page_index(struct vm_area_struct *vma,
 156                                         unsigned long address)
 157 {
 158         pgoff_t pgoff = (address - vma->vm_start) >> PAGE_SHIFT;
 159         pgoff += vma->vm_pgoff;
 160         return pgoff >> (PAGE_CACHE_SHIFT - PAGE_SHIFT);
 161 }
 162
 163 extern void FASTCALL(__lock_page(struct page *page));
 164 extern void FASTCALL(unlock_page(struct page *page));
 165
 166 static inline void lock_page(struct page *page)
 167 {
 168         might_sleep();
 169         if (TestSetPageLocked(page))
 170                 __lock_page(page);
 171 }
 172
 173 /*
 174  * This is exported only for wait_on_page_locked/wait_on_page_writeback.
 175  * Never use this directly!
 176  */
 177 extern void FASTCALL(wait_on_page_bit(struct page *page, int bit_nr));
 178
 179 /*
 180  * Wait for a page to be unlocked.
 181  *
 182  * This must be called with the caller "holding" the page,
 183  * ie with increased "page->count" so that the page won't
 184  * go away during the wait..
 185  */
 186 static inline void wait_on_page_locked(struct page *page)
 187 {
 188         if (PageLocked(page))
 189                 wait_on_page_bit(page, PG_locked);
 190 }
 191
 192 /*
 193  * Wait for a page to complete writeback
 194  */
 195 static inline void wait_on_page_writeback(struct page *page)
 196 {
 197         if (PageWriteback(page))
 198                 wait_on_page_bit(page, PG_writeback);
 199 }
 200
 201 extern void end_page_writeback(struct page *page);
 202
 203 /*
 204  * Fault a userspace page into pagetables.  Return non-zero on a fault.
 205  *
 206  * This assumes that two userspace pages are always sufficient.  That's
 207  * not true if PAGE_CACHE_SIZE > PAGE_SIZE.
 208  */
 209 static inline int fault_in_pages_writeable(char __user *uaddr, int size)
 210 {
 211         int ret;
 212
 213         /*
 214          * Writing zeroes into userspace here is OK, because we know that if
 215          * the zero gets there, we'll be overwriting it.
 216          */
 217         ret = __put_user(0, uaddr);
 218         if (ret == 0) {
 219                 char __user *end = uaddr + size - 1;
 220
 221                 /*
 222                  * If the page was already mapped, this will get a cache miss
 223                  * for sure, so try to avoid doing it.
 224                  */
 225                 if (((unsigned long)uaddr & PAGE_MASK) !=
 226                                 ((unsigned long)end & PAGE_MASK))
 227                         ret = __put_user(0, end);
 228         }
 229         return ret;
 230 }
 231
 232 static inline void fault_in_pages_readable(const char __user *uaddr, int size)
 233 {
 234         volatile char c;
 235         int ret;
 236
 237         ret = __get_user(c, uaddr);
 238         if (ret == 0) {
 239                 const char __user *end = uaddr + size - 1;
 240
 241                 if (((unsigned long)uaddr & PAGE_MASK) !=
 242                                 ((unsigned long)end & PAGE_MASK))
 243                         __get_user(c, end);
 244         }
 245 }
 246
 247 #endif /* _LINUX_PAGEMAP_H */