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