truncate.c revision fc0ecff698165ae8e178efa086e0dd1f385206b1
1/* 2 * mm/truncate.c - code for taking down pages from address_spaces 3 * 4 * Copyright (C) 2002, Linus Torvalds 5 * 6 * 10Sep2002 akpm@zip.com.au 7 * Initial version. 8 */ 9 10#include <linux/kernel.h> 11#include <linux/mm.h> 12#include <linux/swap.h> 13#include <linux/module.h> 14#include <linux/pagemap.h> 15#include <linux/pagevec.h> 16#include <linux/task_io_accounting_ops.h> 17#include <linux/buffer_head.h> /* grr. try_to_release_page, 18 do_invalidatepage */ 19 20 21/** 22 * do_invalidatepage - invalidate part of all of a page 23 * @page: the page which is affected 24 * @offset: the index of the truncation point 25 * 26 * do_invalidatepage() is called when all or part of the page has become 27 * invalidated by a truncate operation. 28 * 29 * do_invalidatepage() does not have to release all buffers, but it must 30 * ensure that no dirty buffer is left outside @offset and that no I/O 31 * is underway against any of the blocks which are outside the truncation 32 * point. Because the caller is about to free (and possibly reuse) those 33 * blocks on-disk. 34 */ 35void do_invalidatepage(struct page *page, unsigned long offset) 36{ 37 void (*invalidatepage)(struct page *, unsigned long); 38 invalidatepage = page->mapping->a_ops->invalidatepage; 39#ifdef CONFIG_BLOCK 40 if (!invalidatepage) 41 invalidatepage = block_invalidatepage; 42#endif 43 if (invalidatepage) 44 (*invalidatepage)(page, offset); 45} 46 47static inline void truncate_partial_page(struct page *page, unsigned partial) 48{ 49 memclear_highpage_flush(page, partial, PAGE_CACHE_SIZE-partial); 50 if (PagePrivate(page)) 51 do_invalidatepage(page, partial); 52} 53 54/* 55 * This cancels just the dirty bit on the kernel page itself, it 56 * does NOT actually remove dirty bits on any mmap's that may be 57 * around. It also leaves the page tagged dirty, so any sync 58 * activity will still find it on the dirty lists, and in particular, 59 * clear_page_dirty_for_io() will still look at the dirty bits in 60 * the VM. 61 * 62 * Doing this should *normally* only ever be done when a page 63 * is truncated, and is not actually mapped anywhere at all. However, 64 * fs/buffer.c does this when it notices that somebody has cleaned 65 * out all the buffers on a page without actually doing it through 66 * the VM. Can you say "ext3 is horribly ugly"? Tought you could. 67 */ 68void cancel_dirty_page(struct page *page, unsigned int account_size) 69{ 70 if (TestClearPageDirty(page)) { 71 struct address_space *mapping = page->mapping; 72 if (mapping && mapping_cap_account_dirty(mapping)) { 73 dec_zone_page_state(page, NR_FILE_DIRTY); 74 if (account_size) 75 task_io_account_cancelled_write(account_size); 76 } 77 } 78} 79EXPORT_SYMBOL(cancel_dirty_page); 80 81/* 82 * If truncate cannot remove the fs-private metadata from the page, the page 83 * becomes anonymous. It will be left on the LRU and may even be mapped into 84 * user pagetables if we're racing with filemap_nopage(). 85 * 86 * We need to bale out if page->mapping is no longer equal to the original 87 * mapping. This happens a) when the VM reclaimed the page while we waited on 88 * its lock, b) when a concurrent invalidate_mapping_pages got there first and 89 * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space. 90 */ 91static void 92truncate_complete_page(struct address_space *mapping, struct page *page) 93{ 94 if (page->mapping != mapping) 95 return; 96 97 cancel_dirty_page(page, PAGE_CACHE_SIZE); 98 99 if (PagePrivate(page)) 100 do_invalidatepage(page, 0); 101 102 ClearPageUptodate(page); 103 ClearPageMappedToDisk(page); 104 remove_from_page_cache(page); 105 page_cache_release(page); /* pagecache ref */ 106} 107 108/* 109 * This is for invalidate_mapping_pages(). That function can be called at 110 * any time, and is not supposed to throw away dirty pages. But pages can 111 * be marked dirty at any time too, so use remove_mapping which safely 112 * discards clean, unused pages. 113 * 114 * Returns non-zero if the page was successfully invalidated. 115 */ 116static int 117invalidate_complete_page(struct address_space *mapping, struct page *page) 118{ 119 int ret; 120 121 if (page->mapping != mapping) 122 return 0; 123 124 if (PagePrivate(page) && !try_to_release_page(page, 0)) 125 return 0; 126 127 ret = remove_mapping(mapping, page); 128 129 return ret; 130} 131 132/** 133 * truncate_inode_pages - truncate range of pages specified by start and 134 * end byte offsets 135 * @mapping: mapping to truncate 136 * @lstart: offset from which to truncate 137 * @lend: offset to which to truncate 138 * 139 * Truncate the page cache, removing the pages that are between 140 * specified offsets (and zeroing out partial page 141 * (if lstart is not page aligned)). 142 * 143 * Truncate takes two passes - the first pass is nonblocking. It will not 144 * block on page locks and it will not block on writeback. The second pass 145 * will wait. This is to prevent as much IO as possible in the affected region. 146 * The first pass will remove most pages, so the search cost of the second pass 147 * is low. 148 * 149 * When looking at page->index outside the page lock we need to be careful to 150 * copy it into a local to avoid races (it could change at any time). 151 * 152 * We pass down the cache-hot hint to the page freeing code. Even if the 153 * mapping is large, it is probably the case that the final pages are the most 154 * recently touched, and freeing happens in ascending file offset order. 155 */ 156void truncate_inode_pages_range(struct address_space *mapping, 157 loff_t lstart, loff_t lend) 158{ 159 const pgoff_t start = (lstart + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT; 160 pgoff_t end; 161 const unsigned partial = lstart & (PAGE_CACHE_SIZE - 1); 162 struct pagevec pvec; 163 pgoff_t next; 164 int i; 165 166 if (mapping->nrpages == 0) 167 return; 168 169 BUG_ON((lend & (PAGE_CACHE_SIZE - 1)) != (PAGE_CACHE_SIZE - 1)); 170 end = (lend >> PAGE_CACHE_SHIFT); 171 172 pagevec_init(&pvec, 0); 173 next = start; 174 while (next <= end && 175 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { 176 for (i = 0; i < pagevec_count(&pvec); i++) { 177 struct page *page = pvec.pages[i]; 178 pgoff_t page_index = page->index; 179 180 if (page_index > end) { 181 next = page_index; 182 break; 183 } 184 185 if (page_index > next) 186 next = page_index; 187 next++; 188 if (TestSetPageLocked(page)) 189 continue; 190 if (PageWriteback(page)) { 191 unlock_page(page); 192 continue; 193 } 194 truncate_complete_page(mapping, page); 195 unlock_page(page); 196 } 197 pagevec_release(&pvec); 198 cond_resched(); 199 } 200 201 if (partial) { 202 struct page *page = find_lock_page(mapping, start - 1); 203 if (page) { 204 wait_on_page_writeback(page); 205 truncate_partial_page(page, partial); 206 unlock_page(page); 207 page_cache_release(page); 208 } 209 } 210 211 next = start; 212 for ( ; ; ) { 213 cond_resched(); 214 if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { 215 if (next == start) 216 break; 217 next = start; 218 continue; 219 } 220 if (pvec.pages[0]->index > end) { 221 pagevec_release(&pvec); 222 break; 223 } 224 for (i = 0; i < pagevec_count(&pvec); i++) { 225 struct page *page = pvec.pages[i]; 226 227 if (page->index > end) 228 break; 229 lock_page(page); 230 wait_on_page_writeback(page); 231 if (page->index > next) 232 next = page->index; 233 next++; 234 truncate_complete_page(mapping, page); 235 unlock_page(page); 236 } 237 pagevec_release(&pvec); 238 } 239} 240EXPORT_SYMBOL(truncate_inode_pages_range); 241 242/** 243 * truncate_inode_pages - truncate *all* the pages from an offset 244 * @mapping: mapping to truncate 245 * @lstart: offset from which to truncate 246 * 247 * Called under (and serialised by) inode->i_mutex. 248 */ 249void truncate_inode_pages(struct address_space *mapping, loff_t lstart) 250{ 251 truncate_inode_pages_range(mapping, lstart, (loff_t)-1); 252} 253EXPORT_SYMBOL(truncate_inode_pages); 254 255/** 256 * invalidate_mapping_pages - Invalidate all the unlocked pages of one inode 257 * @mapping: the address_space which holds the pages to invalidate 258 * @start: the offset 'from' which to invalidate 259 * @end: the offset 'to' which to invalidate (inclusive) 260 * 261 * This function only removes the unlocked pages, if you want to 262 * remove all the pages of one inode, you must call truncate_inode_pages. 263 * 264 * invalidate_mapping_pages() will not block on IO activity. It will not 265 * invalidate pages which are dirty, locked, under writeback or mapped into 266 * pagetables. 267 */ 268unsigned long invalidate_mapping_pages(struct address_space *mapping, 269 pgoff_t start, pgoff_t end) 270{ 271 struct pagevec pvec; 272 pgoff_t next = start; 273 unsigned long ret = 0; 274 int i; 275 276 pagevec_init(&pvec, 0); 277 while (next <= end && 278 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { 279 for (i = 0; i < pagevec_count(&pvec); i++) { 280 struct page *page = pvec.pages[i]; 281 pgoff_t index; 282 int lock_failed; 283 284 lock_failed = TestSetPageLocked(page); 285 286 /* 287 * We really shouldn't be looking at the ->index of an 288 * unlocked page. But we're not allowed to lock these 289 * pages. So we rely upon nobody altering the ->index 290 * of this (pinned-by-us) page. 291 */ 292 index = page->index; 293 if (index > next) 294 next = index; 295 next++; 296 if (lock_failed) 297 continue; 298 299 if (PageDirty(page) || PageWriteback(page)) 300 goto unlock; 301 if (page_mapped(page)) 302 goto unlock; 303 ret += invalidate_complete_page(mapping, page); 304unlock: 305 unlock_page(page); 306 if (next > end) 307 break; 308 } 309 pagevec_release(&pvec); 310 } 311 return ret; 312} 313EXPORT_SYMBOL(invalidate_mapping_pages); 314 315/* 316 * This is like invalidate_complete_page(), except it ignores the page's 317 * refcount. We do this because invalidate_inode_pages2() needs stronger 318 * invalidation guarantees, and cannot afford to leave pages behind because 319 * shrink_list() has a temp ref on them, or because they're transiently sitting 320 * in the lru_cache_add() pagevecs. 321 */ 322static int 323invalidate_complete_page2(struct address_space *mapping, struct page *page) 324{ 325 if (page->mapping != mapping) 326 return 0; 327 328 if (PagePrivate(page) && !try_to_release_page(page, GFP_KERNEL)) 329 return 0; 330 331 write_lock_irq(&mapping->tree_lock); 332 if (PageDirty(page)) 333 goto failed; 334 335 BUG_ON(PagePrivate(page)); 336 __remove_from_page_cache(page); 337 write_unlock_irq(&mapping->tree_lock); 338 ClearPageUptodate(page); 339 page_cache_release(page); /* pagecache ref */ 340 return 1; 341failed: 342 write_unlock_irq(&mapping->tree_lock); 343 return 0; 344} 345 346static int do_launder_page(struct address_space *mapping, struct page *page) 347{ 348 if (!PageDirty(page)) 349 return 0; 350 if (page->mapping != mapping || mapping->a_ops->launder_page == NULL) 351 return 0; 352 return mapping->a_ops->launder_page(page); 353} 354 355/** 356 * invalidate_inode_pages2_range - remove range of pages from an address_space 357 * @mapping: the address_space 358 * @start: the page offset 'from' which to invalidate 359 * @end: the page offset 'to' which to invalidate (inclusive) 360 * 361 * Any pages which are found to be mapped into pagetables are unmapped prior to 362 * invalidation. 363 * 364 * Returns -EIO if any pages could not be invalidated. 365 */ 366int invalidate_inode_pages2_range(struct address_space *mapping, 367 pgoff_t start, pgoff_t end) 368{ 369 struct pagevec pvec; 370 pgoff_t next; 371 int i; 372 int ret = 0; 373 int did_range_unmap = 0; 374 int wrapped = 0; 375 376 pagevec_init(&pvec, 0); 377 next = start; 378 while (next <= end && !ret && !wrapped && 379 pagevec_lookup(&pvec, mapping, next, 380 min(end - next, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) { 381 for (i = 0; !ret && i < pagevec_count(&pvec); i++) { 382 struct page *page = pvec.pages[i]; 383 pgoff_t page_index; 384 385 lock_page(page); 386 if (page->mapping != mapping) { 387 unlock_page(page); 388 continue; 389 } 390 page_index = page->index; 391 next = page_index + 1; 392 if (next == 0) 393 wrapped = 1; 394 if (page_index > end) { 395 unlock_page(page); 396 break; 397 } 398 wait_on_page_writeback(page); 399 while (page_mapped(page)) { 400 if (!did_range_unmap) { 401 /* 402 * Zap the rest of the file in one hit. 403 */ 404 unmap_mapping_range(mapping, 405 (loff_t)page_index<<PAGE_CACHE_SHIFT, 406 (loff_t)(end - page_index + 1) 407 << PAGE_CACHE_SHIFT, 408 0); 409 did_range_unmap = 1; 410 } else { 411 /* 412 * Just zap this page 413 */ 414 unmap_mapping_range(mapping, 415 (loff_t)page_index<<PAGE_CACHE_SHIFT, 416 PAGE_CACHE_SIZE, 0); 417 } 418 } 419 ret = do_launder_page(mapping, page); 420 if (ret == 0 && !invalidate_complete_page2(mapping, page)) 421 ret = -EIO; 422 unlock_page(page); 423 } 424 pagevec_release(&pvec); 425 cond_resched(); 426 } 427 return ret; 428} 429EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range); 430 431/** 432 * invalidate_inode_pages2 - remove all pages from an address_space 433 * @mapping: the address_space 434 * 435 * Any pages which are found to be mapped into pagetables are unmapped prior to 436 * invalidation. 437 * 438 * Returns -EIO if any pages could not be invalidated. 439 */ 440int invalidate_inode_pages2(struct address_space *mapping) 441{ 442 return invalidate_inode_pages2_range(mapping, 0, -1); 443} 444EXPORT_SYMBOL_GPL(invalidate_inode_pages2); 445