1 /* 2 * mm/truncate.c - code for taking down pages from address_spaces 3 * 4 * Copyright (C) 2002, Linus Torvalds 5 * 6 * 10Sep2002 Andrew Morton 7 * Initial version. 8 */ 9 10 #include <linux/kernel.h> 11 #include <linux/backing-dev.h> 12 #include <linux/mm.h> 13 #include <linux/swap.h> 14 #include <linux/module.h> 15 #include <linux/pagemap.h> 16 #include <linux/highmem.h> 17 #include <linux/pagevec.h> 18 #include <linux/task_io_accounting_ops.h> 19 #include <linux/buffer_head.h> /* grr. try_to_release_page, 20 do_invalidatepage */ 21 #include "internal.h" 22 23 24 /** 25 * do_invalidatepage - invalidate part or all of a page 26 * @page: the page which is affected 27 * @offset: the index of the truncation point 28 * 29 * do_invalidatepage() is called when all or part of the page has become 30 * invalidated by a truncate operation. 31 * 32 * do_invalidatepage() does not have to release all buffers, but it must 33 * ensure that no dirty buffer is left outside @offset and that no I/O 34 * is underway against any of the blocks which are outside the truncation 35 * point. Because the caller is about to free (and possibly reuse) those 36 * blocks on-disk. 37 */ 38 void do_invalidatepage(struct page *page, unsigned long offset) 39 { 40 void (*invalidatepage)(struct page *, unsigned long); 41 invalidatepage = page->mapping->a_ops->invalidatepage; 42 #ifdef CONFIG_BLOCK 43 if (!invalidatepage) 44 invalidatepage = block_invalidatepage; 45 #endif 46 if (invalidatepage) 47 (*invalidatepage)(page, offset); 48 } 49 50 static inline void truncate_partial_page(struct page *page, unsigned partial) 51 { 52 zero_user_segment(page, partial, PAGE_CACHE_SIZE); 53 if (page_has_private(page)) 54 do_invalidatepage(page, partial); 55 } 56 57 /* 58 * This cancels just the dirty bit on the kernel page itself, it 59 * does NOT actually remove dirty bits on any mmap's that may be 60 * around. It also leaves the page tagged dirty, so any sync 61 * activity will still find it on the dirty lists, and in particular, 62 * clear_page_dirty_for_io() will still look at the dirty bits in 63 * the VM. 64 * 65 * Doing this should *normally* only ever be done when a page 66 * is truncated, and is not actually mapped anywhere at all. However, 67 * fs/buffer.c does this when it notices that somebody has cleaned 68 * out all the buffers on a page without actually doing it through 69 * the VM. Can you say "ext3 is horribly ugly"? Tought you could. 70 */ 71 void cancel_dirty_page(struct page *page, unsigned int account_size) 72 { 73 if (TestClearPageDirty(page)) { 74 struct address_space *mapping = page->mapping; 75 if (mapping && mapping_cap_account_dirty(mapping)) { 76 dec_zone_page_state(page, NR_FILE_DIRTY); 77 dec_bdi_stat(mapping->backing_dev_info, 78 BDI_RECLAIMABLE); 79 if (account_size) 80 task_io_account_cancelled_write(account_size); 81 } 82 } 83 } 84 EXPORT_SYMBOL(cancel_dirty_page); 85 86 /* 87 * If truncate cannot remove the fs-private metadata from the page, the page 88 * becomes orphaned. It will be left on the LRU and may even be mapped into 89 * user pagetables if we're racing with filemap_fault(). 90 * 91 * We need to bale out if page->mapping is no longer equal to the original 92 * mapping. This happens a) when the VM reclaimed the page while we waited on 93 * its lock, b) when a concurrent invalidate_mapping_pages got there first and 94 * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space. 95 */ 96 static int 97 truncate_complete_page(struct address_space *mapping, struct page *page) 98 { 99 if (page->mapping != mapping) 100 return -EIO; 101 102 if (page_has_private(page)) 103 do_invalidatepage(page, 0); 104 105 cancel_dirty_page(page, PAGE_CACHE_SIZE); 106 107 clear_page_mlock(page); 108 remove_from_page_cache(page); 109 ClearPageMappedToDisk(page); 110 page_cache_release(page); /* pagecache ref */ 111 return 0; 112 } 113 114 /* 115 * This is for invalidate_mapping_pages(). That function can be called at 116 * any time, and is not supposed to throw away dirty pages. But pages can 117 * be marked dirty at any time too, so use remove_mapping which safely 118 * discards clean, unused pages. 119 * 120 * Returns non-zero if the page was successfully invalidated. 121 */ 122 static int 123 invalidate_complete_page(struct address_space *mapping, struct page *page) 124 { 125 int ret; 126 127 if (page->mapping != mapping) 128 return 0; 129 130 if (page_has_private(page) && !try_to_release_page(page, 0)) 131 return 0; 132 133 clear_page_mlock(page); 134 ret = remove_mapping(mapping, page); 135 136 return ret; 137 } 138 139 int truncate_inode_page(struct address_space *mapping, struct page *page) 140 { 141 if (page_mapped(page)) { 142 unmap_mapping_range(mapping, 143 (loff_t)page->index << PAGE_CACHE_SHIFT, 144 PAGE_CACHE_SIZE, 0); 145 } 146 return truncate_complete_page(mapping, page); 147 } 148 149 /* 150 * Used to get rid of pages on hardware memory corruption. 151 */ 152 int generic_error_remove_page(struct address_space *mapping, struct page *page) 153 { 154 if (!mapping) 155 return -EINVAL; 156 /* 157 * Only punch for normal data pages for now. 158 * Handling other types like directories would need more auditing. 159 */ 160 if (!S_ISREG(mapping->host->i_mode)) 161 return -EIO; 162 return truncate_inode_page(mapping, page); 163 } 164 EXPORT_SYMBOL(generic_error_remove_page); 165 166 /* 167 * Safely invalidate one page from its pagecache mapping. 168 * It only drops clean, unused pages. The page must be locked. 169 * 170 * Returns 1 if the page is successfully invalidated, otherwise 0. 171 */ 172 int invalidate_inode_page(struct page *page) 173 { 174 struct address_space *mapping = page_mapping(page); 175 if (!mapping) 176 return 0; 177 if (PageDirty(page) || PageWriteback(page)) 178 return 0; 179 if (page_mapped(page)) 180 return 0; 181 return invalidate_complete_page(mapping, page); 182 } 183 184 /** 185 * truncate_inode_pages - truncate range of pages specified by start & end byte offsets 186 * @mapping: mapping to truncate 187 * @lstart: offset from which to truncate 188 * @lend: offset to which to truncate 189 * 190 * Truncate the page cache, removing the pages that are between 191 * specified offsets (and zeroing out partial page 192 * (if lstart is not page aligned)). 193 * 194 * Truncate takes two passes - the first pass is nonblocking. It will not 195 * block on page locks and it will not block on writeback. The second pass 196 * will wait. This is to prevent as much IO as possible in the affected region. 197 * The first pass will remove most pages, so the search cost of the second pass 198 * is low. 199 * 200 * When looking at page->index outside the page lock we need to be careful to 201 * copy it into a local to avoid races (it could change at any time). 202 * 203 * We pass down the cache-hot hint to the page freeing code. Even if the 204 * mapping is large, it is probably the case that the final pages are the most 205 * recently touched, and freeing happens in ascending file offset order. 206 */ 207 void truncate_inode_pages_range(struct address_space *mapping, 208 loff_t lstart, loff_t lend) 209 { 210 const pgoff_t start = (lstart + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT; 211 pgoff_t end; 212 const unsigned partial = lstart & (PAGE_CACHE_SIZE - 1); 213 struct pagevec pvec; 214 pgoff_t next; 215 int i; 216 217 if (mapping->nrpages == 0) 218 return; 219 220 BUG_ON((lend & (PAGE_CACHE_SIZE - 1)) != (PAGE_CACHE_SIZE - 1)); 221 end = (lend >> PAGE_CACHE_SHIFT); 222 223 pagevec_init(&pvec, 0); 224 next = start; 225 while (next <= end && 226 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { 227 for (i = 0; i < pagevec_count(&pvec); i++) { 228 struct page *page = pvec.pages[i]; 229 pgoff_t page_index = page->index; 230 231 if (page_index > end) { 232 next = page_index; 233 break; 234 } 235 236 if (page_index > next) 237 next = page_index; 238 next++; 239 if (!trylock_page(page)) 240 continue; 241 if (PageWriteback(page)) { 242 unlock_page(page); 243 continue; 244 } 245 truncate_inode_page(mapping, page); 246 unlock_page(page); 247 } 248 pagevec_release(&pvec); 249 cond_resched(); 250 } 251 252 if (partial) { 253 struct page *page = find_lock_page(mapping, start - 1); 254 if (page) { 255 wait_on_page_writeback(page); 256 truncate_partial_page(page, partial); 257 unlock_page(page); 258 page_cache_release(page); 259 } 260 } 261 262 next = start; 263 for ( ; ; ) { 264 cond_resched(); 265 if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { 266 if (next == start) 267 break; 268 next = start; 269 continue; 270 } 271 if (pvec.pages[0]->index > end) { 272 pagevec_release(&pvec); 273 break; 274 } 275 mem_cgroup_uncharge_start(); 276 for (i = 0; i < pagevec_count(&pvec); i++) { 277 struct page *page = pvec.pages[i]; 278 279 if (page->index > end) 280 break; 281 lock_page(page); 282 wait_on_page_writeback(page); 283 truncate_inode_page(mapping, page); 284 if (page->index > next) 285 next = page->index; 286 next++; 287 unlock_page(page); 288 } 289 pagevec_release(&pvec); 290 mem_cgroup_uncharge_end(); 291 } 292 } 293 EXPORT_SYMBOL(truncate_inode_pages_range); 294 295 /** 296 * truncate_inode_pages - truncate *all* the pages from an offset 297 * @mapping: mapping to truncate 298 * @lstart: offset from which to truncate 299 * 300 * Called under (and serialised by) inode->i_mutex. 301 */ 302 void truncate_inode_pages(struct address_space *mapping, loff_t lstart) 303 { 304 truncate_inode_pages_range(mapping, lstart, (loff_t)-1); 305 } 306 EXPORT_SYMBOL(truncate_inode_pages); 307 308 /** 309 * invalidate_mapping_pages - Invalidate all the unlocked pages of one inode 310 * @mapping: the address_space which holds the pages to invalidate 311 * @start: the offset 'from' which to invalidate 312 * @end: the offset 'to' which to invalidate (inclusive) 313 * 314 * This function only removes the unlocked pages, if you want to 315 * remove all the pages of one inode, you must call truncate_inode_pages. 316 * 317 * invalidate_mapping_pages() will not block on IO activity. It will not 318 * invalidate pages which are dirty, locked, under writeback or mapped into 319 * pagetables. 320 */ 321 unsigned long invalidate_mapping_pages(struct address_space *mapping, 322 pgoff_t start, pgoff_t end) 323 { 324 struct pagevec pvec; 325 pgoff_t next = start; 326 unsigned long ret = 0; 327 int i; 328 329 pagevec_init(&pvec, 0); 330 while (next <= end && 331 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { 332 mem_cgroup_uncharge_start(); 333 for (i = 0; i < pagevec_count(&pvec); i++) { 334 struct page *page = pvec.pages[i]; 335 pgoff_t index; 336 int lock_failed; 337 338 lock_failed = !trylock_page(page); 339 340 /* 341 * We really shouldn't be looking at the ->index of an 342 * unlocked page. But we're not allowed to lock these 343 * pages. So we rely upon nobody altering the ->index 344 * of this (pinned-by-us) page. 345 */ 346 index = page->index; 347 if (index > next) 348 next = index; 349 next++; 350 if (lock_failed) 351 continue; 352 353 ret += invalidate_inode_page(page); 354 355 unlock_page(page); 356 if (next > end) 357 break; 358 } 359 pagevec_release(&pvec); 360 mem_cgroup_uncharge_end(); 361 cond_resched(); 362 } 363 return ret; 364 } 365 EXPORT_SYMBOL(invalidate_mapping_pages); 366 367 /* 368 * This is like invalidate_complete_page(), except it ignores the page's 369 * refcount. We do this because invalidate_inode_pages2() needs stronger 370 * invalidation guarantees, and cannot afford to leave pages behind because 371 * shrink_page_list() has a temp ref on them, or because they're transiently 372 * sitting in the lru_cache_add() pagevecs. 373 */ 374 static int 375 invalidate_complete_page2(struct address_space *mapping, struct page *page) 376 { 377 if (page->mapping != mapping) 378 return 0; 379 380 if (page_has_private(page) && !try_to_release_page(page, GFP_KERNEL)) 381 return 0; 382 383 spin_lock_irq(&mapping->tree_lock); 384 if (PageDirty(page)) 385 goto failed; 386 387 clear_page_mlock(page); 388 BUG_ON(page_has_private(page)); 389 __remove_from_page_cache(page); 390 spin_unlock_irq(&mapping->tree_lock); 391 mem_cgroup_uncharge_cache_page(page); 392 page_cache_release(page); /* pagecache ref */ 393 return 1; 394 failed: 395 spin_unlock_irq(&mapping->tree_lock); 396 return 0; 397 } 398 399 static int do_launder_page(struct address_space *mapping, struct page *page) 400 { 401 if (!PageDirty(page)) 402 return 0; 403 if (page->mapping != mapping || mapping->a_ops->launder_page == NULL) 404 return 0; 405 return mapping->a_ops->launder_page(page); 406 } 407 408 /** 409 * invalidate_inode_pages2_range - remove range of pages from an address_space 410 * @mapping: the address_space 411 * @start: the page offset 'from' which to invalidate 412 * @end: the page offset 'to' which to invalidate (inclusive) 413 * 414 * Any pages which are found to be mapped into pagetables are unmapped prior to 415 * invalidation. 416 * 417 * Returns -EBUSY if any pages could not be invalidated. 418 */ 419 int invalidate_inode_pages2_range(struct address_space *mapping, 420 pgoff_t start, pgoff_t end) 421 { 422 struct pagevec pvec; 423 pgoff_t next; 424 int i; 425 int ret = 0; 426 int ret2 = 0; 427 int did_range_unmap = 0; 428 int wrapped = 0; 429 430 pagevec_init(&pvec, 0); 431 next = start; 432 while (next <= end && !wrapped && 433 pagevec_lookup(&pvec, mapping, next, 434 min(end - next, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) { 435 mem_cgroup_uncharge_start(); 436 for (i = 0; i < pagevec_count(&pvec); i++) { 437 struct page *page = pvec.pages[i]; 438 pgoff_t page_index; 439 440 lock_page(page); 441 if (page->mapping != mapping) { 442 unlock_page(page); 443 continue; 444 } 445 page_index = page->index; 446 next = page_index + 1; 447 if (next == 0) 448 wrapped = 1; 449 if (page_index > end) { 450 unlock_page(page); 451 break; 452 } 453 wait_on_page_writeback(page); 454 if (page_mapped(page)) { 455 if (!did_range_unmap) { 456 /* 457 * Zap the rest of the file in one hit. 458 */ 459 unmap_mapping_range(mapping, 460 (loff_t)page_index<<PAGE_CACHE_SHIFT, 461 (loff_t)(end - page_index + 1) 462 << PAGE_CACHE_SHIFT, 463 0); 464 did_range_unmap = 1; 465 } else { 466 /* 467 * Just zap this page 468 */ 469 unmap_mapping_range(mapping, 470 (loff_t)page_index<<PAGE_CACHE_SHIFT, 471 PAGE_CACHE_SIZE, 0); 472 } 473 } 474 BUG_ON(page_mapped(page)); 475 ret2 = do_launder_page(mapping, page); 476 if (ret2 == 0) { 477 if (!invalidate_complete_page2(mapping, page)) 478 ret2 = -EBUSY; 479 } 480 if (ret2 < 0) 481 ret = ret2; 482 unlock_page(page); 483 } 484 pagevec_release(&pvec); 485 mem_cgroup_uncharge_end(); 486 cond_resched(); 487 } 488 return ret; 489 } 490 EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range); 491 492 /** 493 * invalidate_inode_pages2 - remove all pages from an address_space 494 * @mapping: the address_space 495 * 496 * Any pages which are found to be mapped into pagetables are unmapped prior to 497 * invalidation. 498 * 499 * Returns -EBUSY if any pages could not be invalidated. 500 */ 501 int invalidate_inode_pages2(struct address_space *mapping) 502 { 503 return invalidate_inode_pages2_range(mapping, 0, -1); 504 } 505 EXPORT_SYMBOL_GPL(invalidate_inode_pages2); 506 507 /** 508 * truncate_pagecache - unmap and remove pagecache that has been truncated 509 * @inode: inode 510 * @old: old file offset 511 * @new: new file offset 512 * 513 * inode's new i_size must already be written before truncate_pagecache 514 * is called. 515 * 516 * This function should typically be called before the filesystem 517 * releases resources associated with the freed range (eg. deallocates 518 * blocks). This way, pagecache will always stay logically coherent 519 * with on-disk format, and the filesystem would not have to deal with 520 * situations such as writepage being called for a page that has already 521 * had its underlying blocks deallocated. 522 */ 523 void truncate_pagecache(struct inode *inode, loff_t old, loff_t new) 524 { 525 struct address_space *mapping = inode->i_mapping; 526 527 /* 528 * unmap_mapping_range is called twice, first simply for 529 * efficiency so that truncate_inode_pages does fewer 530 * single-page unmaps. However after this first call, and 531 * before truncate_inode_pages finishes, it is possible for 532 * private pages to be COWed, which remain after 533 * truncate_inode_pages finishes, hence the second 534 * unmap_mapping_range call must be made for correctness. 535 */ 536 unmap_mapping_range(mapping, new + PAGE_SIZE - 1, 0, 1); 537 truncate_inode_pages(mapping, new); 538 unmap_mapping_range(mapping, new + PAGE_SIZE - 1, 0, 1); 539 } 540 EXPORT_SYMBOL(truncate_pagecache); 541 542 /** 543 * vmtruncate - unmap mappings "freed" by truncate() syscall 544 * @inode: inode of the file used 545 * @offset: file offset to start truncating 546 * 547 * NOTE! We have to be ready to update the memory sharing 548 * between the file and the memory map for a potential last 549 * incomplete page. Ugly, but necessary. 550 */ 551 int vmtruncate(struct inode *inode, loff_t offset) 552 { 553 loff_t oldsize; 554 int error; 555 556 error = inode_newsize_ok(inode, offset); 557 if (error) 558 return error; 559 oldsize = inode->i_size; 560 i_size_write(inode, offset); 561 truncate_pagecache(inode, oldsize, offset); 562 if (inode->i_op->truncate) 563 inode->i_op->truncate(inode); 564 565 return error; 566 } 567 EXPORT_SYMBOL(vmtruncate); 568