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 #include <linux/bitops.h>
  15 #include <linux/hardirq.h> /* for in_interrupt() */
  16 #include <linux/hugetlb_inline.h>
  17
  18 /*
  19  * Bits in mapping->flags.  The lower __GFP_BITS_SHIFT bits are the page
  20  * allocation mode flags.
  21  */
  22 enum mapping_flags {
  23         AS_EIO          = __GFP_BITS_SHIFT + 0, /* IO error on async write */
  24         AS_ENOSPC       = __GFP_BITS_SHIFT + 1, /* ENOSPC on async write */
  25         AS_MM_ALL_LOCKS = __GFP_BITS_SHIFT + 2, /* under mm_take_all_locks() */
  26         AS_UNEVICTABLE  = __GFP_BITS_SHIFT + 3, /* e.g., ramdisk, SHM_LOCK */
  27 };
  28
  29 static inline void mapping_set_error(struct address_space *mapping, int error)
  30 {
  31         if (unlikely(error)) {
  32                 if (error == -ENOSPC)
  33                         set_bit(AS_ENOSPC, &mapping->flags);
  34                 else
  35                         set_bit(AS_EIO, &mapping->flags);
  36         }
  37 }
  38
  39 static inline void mapping_set_unevictable(struct address_space *mapping)
  40 {
  41         set_bit(AS_UNEVICTABLE, &mapping->flags);
  42 }
  43
  44 static inline void mapping_clear_unevictable(struct address_space *mapping)
  45 {
  46         clear_bit(AS_UNEVICTABLE, &mapping->flags);
  47 }
  48
  49 static inline int mapping_unevictable(struct address_space *mapping)
  50 {
  51         if (mapping)
  52                 return test_bit(AS_UNEVICTABLE, &mapping->flags);
  53         return !!mapping;
  54 }
  55
  56 static inline gfp_t mapping_gfp_mask(struct address_space * mapping)
  57 {
  58         return (__force gfp_t)mapping->flags & __GFP_BITS_MASK;
  59 }
  60
  61 /*
  62  * This is non-atomic.  Only to be used before the mapping is activated.
  63  * Probably needs a barrier...
  64  */
  65 static inline void mapping_set_gfp_mask(struct address_space *m, gfp_t mask)
  66 {
  67         m->flags = (m->flags & ~(__force unsigned long)__GFP_BITS_MASK) |
  68                                 (__force unsigned long)mask;
  69 }
  70
  71 /*
  72  * The page cache can done in larger chunks than
  73  * one page, because it allows for more efficient
  74  * throughput (it can then be mapped into user
  75  * space in smaller chunks for same flexibility).
  76  *
  77  * Or rather, it _will_ be done in larger chunks.
  78  */
  79 #define PAGE_CACHE_SHIFT        PAGE_SHIFT
  80 #define PAGE_CACHE_SIZE         PAGE_SIZE
  81 #define PAGE_CACHE_MASK         PAGE_MASK
  82 #define PAGE_CACHE_ALIGN(addr)  (((addr)+PAGE_CACHE_SIZE-1)&PAGE_CACHE_MASK)
  83
  84 #define page_cache_get(page)            get_page(page)
  85 #define page_cache_release(page)        put_page(page)
  86 void release_pages(struct page **pages, int nr, int cold);
  87
  88 /*
  89  * speculatively take a reference to a page.
  90  * If the page is free (_count == 0), then _count is untouched, and 0
  91  * is returned. Otherwise, _count is incremented by 1 and 1 is returned.
  92  *
  93  * This function must be called inside the same rcu_read_lock() section as has
  94  * been used to lookup the page in the pagecache radix-tree (or page table):
  95  * this allows allocators to use a synchronize_rcu() to stabilize _count.
  96  *
  97  * Unless an RCU grace period has passed, the count of all pages coming out
  98  * of the allocator must be considered unstable. page_count may return higher
  99  * than expected, and put_page must be able to do the right thing when the
 100  * page has been finished with, no matter what it is subsequently allocated
 101  * for (because put_page is what is used here to drop an invalid speculative
 102  * reference).
 103  *
 104  * This is the interesting part of the lockless pagecache (and lockless
 105  * get_user_pages) locking protocol, where the lookup-side (eg. find_get_page)
 106  * has the following pattern:
 107  * 1. find page in radix tree
 108  * 2. conditionally increment refcount
 109  * 3. check the page is still in pagecache (if no, goto 1)
 110  *
 111  * Remove-side that cares about stability of _count (eg. reclaim) has the
 112  * following (with tree_lock held for write):
 113  * A. atomically check refcount is correct and set it to 0 (atomic_cmpxchg)
 114  * B. remove page from pagecache
 115  * C. free the page
 116  *
 117  * There are 2 critical interleavings that matter:
 118  * - 2 runs before A: in this case, A sees elevated refcount and bails out
 119  * - A runs before 2: in this case, 2 sees zero refcount and retries;
 120  *   subsequently, B will complete and 1 will find no page, causing the
 121  *   lookup to return NULL.
 122  *
 123  * It is possible that between 1 and 2, the page is removed then the exact same
 124  * page is inserted into the same position in pagecache. That's OK: the
 125  * old find_get_page using tree_lock could equally have run before or after
 126  * such a re-insertion, depending on order that locks are granted.
 127  *
 128  * Lookups racing against pagecache insertion isn't a big problem: either 1
 129  * will find the page or it will not. Likewise, the old find_get_page could run
 130  * either before the insertion or afterwards, depending on timing.
 131  */
 132 static inline int page_cache_get_speculative(struct page *page)
 133 {
 134         VM_BUG_ON(in_interrupt());
 135
 136 #if !defined(CONFIG_SMP) && defined(CONFIG_TREE_RCU)
 137 # ifdef CONFIG_PREEMPT
 138         VM_BUG_ON(!in_atomic());
 139 # endif
 140         /*
 141          * Preempt must be disabled here - we rely on rcu_read_lock doing
 142          * this for us.
 143          *
 144          * Pagecache won't be truncated from interrupt context, so if we have
 145          * found a page in the radix tree here, we have pinned its refcount by
 146          * disabling preempt, and hence no need for the "speculative get" that
 147          * SMP requires.
 148          */
 149         VM_BUG_ON(page_count(page) == 0);
 150         atomic_inc(&page->_count);
 151
 152 #else
 153         if (unlikely(!get_page_unless_zero(page))) {
 154                 /*
 155                  * Either the page has been freed, or will be freed.
 156                  * In either case, retry here and the caller should
 157                  * do the right thing (see comments above).
 158                  */
 159                 return 0;
 160         }
 161 #endif
 162         VM_BUG_ON(PageTail(page));
 163
 164         return 1;
 165 }
 166
 167 /*
 168  * Same as above, but add instead of inc (could just be merged)
 169  */
 170 static inline int page_cache_add_speculative(struct page *page, int count)
 171 {
 172         VM_BUG_ON(in_interrupt());
 173
 174 #if !defined(CONFIG_SMP) && defined(CONFIG_TREE_RCU)
 175 # ifdef CONFIG_PREEMPT
 176         VM_BUG_ON(!in_atomic());
 177 # endif
 178         VM_BUG_ON(page_count(page) == 0);
 179         atomic_add(count, &page->_count);
 180
 181 #else
 182         if (unlikely(!atomic_add_unless(&page->_count, count, 0)))
 183                 return 0;
 184 #endif
 185         VM_BUG_ON(PageCompound(page) && page != compound_head(page));
 186
 187         return 1;
 188 }
 189
 190 static inline int page_freeze_refs(struct page *page, int count)
 191 {
 192         return likely(atomic_cmpxchg(&page->_count, count, 0) == count);
 193 }
 194
 195 static inline void page_unfreeze_refs(struct page *page, int count)
 196 {
 197         VM_BUG_ON(page_count(page) != 0);
 198         VM_BUG_ON(count == 0);
 199
 200         atomic_set(&page->_count, count);
 201 }
 202
 203 #ifdef CONFIG_NUMA
 204 extern struct page *__page_cache_alloc(gfp_t gfp);
 205 #else
 206 static inline struct page *__page_cache_alloc(gfp_t gfp)
 207 {
 208         return alloc_pages(gfp, 0);
 209 }
 210 #endif
 211
 212 static inline struct page *page_cache_alloc(struct address_space *x)
 213 {
 214         return __page_cache_alloc(mapping_gfp_mask(x));
 215 }
 216
 217 static inline struct page *page_cache_alloc_cold(struct address_space *x)
 218 {
 219         return __page_cache_alloc(mapping_gfp_mask(x)|__GFP_COLD);
 220 }
 221
 222 static inline struct page *page_cache_alloc_readahead(struct address_space *x)
 223 {
 224         return __page_cache_alloc(mapping_gfp_mask(x) |
 225                                   __GFP_COLD | __GFP_NORETRY | __GFP_NOWARN);
 226 }
 227
 228 typedef int filler_t(void *, struct page *);
 229
 230 extern struct page * find_get_page(struct address_space *mapping,
 231                                 pgoff_t index);
 232 extern struct page * find_lock_page(struct address_space *mapping,
 233                                 pgoff_t index);
 234 extern struct page * find_or_create_page(struct address_space *mapping,
 235                                 pgoff_t index, gfp_t gfp_mask);
 236 unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
 237                         unsigned int nr_pages, struct page **pages);
 238 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t start,
 239                                unsigned int nr_pages, struct page **pages);
 240 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
 241                         int tag, unsigned int nr_pages, struct page **pages);
 242
 243 struct page *grab_cache_page_write_begin(struct address_space *mapping,
 244                         pgoff_t index, unsigned flags);
 245
 246 /*
 247  * Returns locked page at given index in given cache, creating it if needed.
 248  */
 249 static inline struct page *grab_cache_page(struct address_space *mapping,
 250                                                                 pgoff_t index)
 251 {
 252         return find_or_create_page(mapping, index, mapping_gfp_mask(mapping));
 253 }
 254
 255 extern struct page * grab_cache_page_nowait(struct address_space *mapping,
 256                                 pgoff_t index);
 257 extern struct page * read_cache_page_async(struct address_space *mapping,
 258                                 pgoff_t index, filler_t *filler,
 259                                 void *data);
 260 extern struct page * read_cache_page(struct address_space *mapping,
 261                                 pgoff_t index, filler_t *filler,
 262                                 void *data);
 263 extern struct page * read_cache_page_gfp(struct address_space *mapping,
 264                                 pgoff_t index, gfp_t gfp_mask);
 265 extern int read_cache_pages(struct address_space *mapping,
 266                 struct list_head *pages, filler_t *filler, void *data);
 267
 268 static inline struct page *read_mapping_page_async(
 269                                                 struct address_space *mapping,
 270                                                      pgoff_t index, void *data)
 271 {
 272         filler_t *filler = (filler_t *)mapping->a_ops->readpage;
 273         return read_cache_page_async(mapping, index, filler, data);
 274 }
 275
 276 static inline struct page *read_mapping_page(struct address_space *mapping,
 277                                              pgoff_t index, void *data)
 278 {
 279         filler_t *filler = (filler_t *)mapping->a_ops->readpage;
 280         return read_cache_page(mapping, index, filler, data);
 281 }
 282
 283 /*
 284  * Return byte-offset into filesystem object for page.
 285  */
 286 static inline loff_t page_offset(struct page *page)
 287 {
 288         return ((loff_t)page->index) << PAGE_CACHE_SHIFT;
 289 }
 290
 291 extern pgoff_t linear_hugepage_index(struct vm_area_struct *vma,
 292                                      unsigned long address);
 293
 294 static inline pgoff_t linear_page_index(struct vm_area_struct *vma,
 295                                         unsigned long address)
 296 {
 297         pgoff_t pgoff;
 298         if (unlikely(is_vm_hugetlb_page(vma)))
 299                 return linear_hugepage_index(vma, address);
 300         pgoff = (address - vma->vm_start) >> PAGE_SHIFT;
 301         pgoff += vma->vm_pgoff;
 302         return pgoff >> (PAGE_CACHE_SHIFT - PAGE_SHIFT);
 303 }
 304
 305 extern void __lock_page(struct page *page);
 306 extern int __lock_page_killable(struct page *page);
 307 extern int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
 308                                 unsigned int flags);
 309 extern void unlock_page(struct page *page);
 310
 311 static inline void __set_page_locked(struct page *page)
 312 {
 313         __set_bit(PG_locked, &page->flags);
 314 }
 315
 316 static inline void __clear_page_locked(struct page *page)
 317 {
 318         __clear_bit(PG_locked, &page->flags);
 319 }
 320
 321 static inline int trylock_page(struct page *page)
 322 {
 323         return (likely(!test_and_set_bit_lock(PG_locked, &page->flags)));
 324 }
 325
 326 /*
 327  * lock_page may only be called if we have the page's inode pinned.
 328  */
 329 static inline void lock_page(struct page *page)
 330 {
 331         might_sleep();
 332         if (!trylock_page(page))
 333                 __lock_page(page);
 334 }
 335
 336 /*
 337  * lock_page_killable is like lock_page but can be interrupted by fatal
 338  * signals.  It returns 0 if it locked the page and -EINTR if it was
 339  * killed while waiting.
 340  */
 341 static inline int lock_page_killable(struct page *page)
 342 {
 343         might_sleep();
 344         if (!trylock_page(page))
 345                 return __lock_page_killable(page);
 346         return 0;
 347 }
 348
 349 /*
 350  * lock_page_or_retry - Lock the page, unless this would block and the
 351  * caller indicated that it can handle a retry.
 352  */
 353 static inline int lock_page_or_retry(struct page *page, struct mm_struct *mm,
 354                                      unsigned int flags)
 355 {
 356         might_sleep();
 357         return trylock_page(page) || __lock_page_or_retry(page, mm, flags);
 358 }
 359
 360 /*
 361  * This is exported only for wait_on_page_locked/wait_on_page_writeback.
 362  * Never use this directly!
 363  */
 364 extern void wait_on_page_bit(struct page *page, int bit_nr);
 365
 366 extern int wait_on_page_bit_killable(struct page *page, int bit_nr);
 367
 368 static inline int wait_on_page_locked_killable(struct page *page)
 369 {
 370         if (PageLocked(page))
 371                 return wait_on_page_bit_killable(page, PG_locked);
 372         return 0;
 373 }
 374
 375 /*
 376  * Wait for a page to be unlocked.
 377  *
 378  * This must be called with the caller "holding" the page,
 379  * ie with increased "page->count" so that the page won't
 380  * go away during the wait..
 381  */
 382 static inline void wait_on_page_locked(struct page *page)
 383 {
 384         if (PageLocked(page))
 385                 wait_on_page_bit(page, PG_locked);
 386 }
 387
 388 /*
 389  * Wait for a page to complete writeback
 390  */
 391 static inline void wait_on_page_writeback(struct page *page)
 392 {
 393         if (PageWriteback(page))
 394                 wait_on_page_bit(page, PG_writeback);
 395 }
 396
 397 extern void end_page_writeback(struct page *page);
 398
 399 /*
 400  * Add an arbitrary waiter to a page's wait queue
 401  */
 402 extern void add_page_wait_queue(struct page *page, wait_queue_t *waiter);
 403
 404 /*
 405  * Fault a userspace page into pagetables.  Return non-zero on a fault.
 406  *
 407  * This assumes that two userspace pages are always sufficient.  That's
 408  * not true if PAGE_CACHE_SIZE > PAGE_SIZE.
 409  */
 410 static inline int fault_in_pages_writeable(char __user *uaddr, int size)
 411 {
 412         int ret;
 413
 414         if (unlikely(size == 0))
 415                 return 0;
 416
 417         /*
 418          * Writing zeroes into userspace here is OK, because we know that if
 419          * the zero gets there, we'll be overwriting it.
 420          */
 421         ret = __put_user(0, uaddr);
 422         if (ret == 0) {
 423                 char __user *end = uaddr + size - 1;
 424
 425                 /*
 426                  * If the page was already mapped, this will get a cache miss
 427                  * for sure, so try to avoid doing it.
 428                  */
 429                 if (((unsigned long)uaddr & PAGE_MASK) !=
 430                                 ((unsigned long)end & PAGE_MASK))
 431                         ret = __put_user(0, end);
 432         }
 433         return ret;
 434 }
 435
 436 static inline int fault_in_pages_readable(const char __user *uaddr, int size)
 437 {
 438         volatile char c;
 439         int ret;
 440
 441         if (unlikely(size == 0))
 442                 return 0;
 443
 444         ret = __get_user(c, uaddr);
 445         if (ret == 0) {
 446                 const char __user *end = uaddr + size - 1;
 447
 448                 if (((unsigned long)uaddr & PAGE_MASK) !=
 449                                 ((unsigned long)end & PAGE_MASK)) {
 450                         ret = __get_user(c, end);
 451                         (void)c;
 452                 }
 453         }
 454         return ret;
 455 }
 456
 457 int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
 458                                 pgoff_t index, gfp_t gfp_mask);
 459 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
 460                                 pgoff_t index, gfp_t gfp_mask);
 461 extern void delete_from_page_cache(struct page *page);
 462 extern void __delete_from_page_cache(struct page *page);
 463 int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask);
 464
 465 /*
 466  * Like add_to_page_cache_locked, but used to add newly allocated pages:
 467  * the page is new, so we can just run __set_page_locked() against it.
 468  */
 469 static inline int add_to_page_cache(struct page *page,
 470                 struct address_space *mapping, pgoff_t offset, gfp_t gfp_mask)
 471 {
 472         int error;
 473
 474         __set_page_locked(page);
 475         error = add_to_page_cache_locked(page, mapping, offset, gfp_mask);
 476         if (unlikely(error))
 477                 __clear_page_locked(page);
 478         return error;
 479 }
 480
 481 #endif /* _LINUX_PAGEMAP_H */