1 /* 2 * linux/fs/buffer.c 3 * 4 * Copyright (C) 1991, 1992, 2002 Linus Torvalds 5 */ 6 7 /* 8 * Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95 9 * 10 * Removed a lot of unnecessary code and simplified things now that 11 * the buffer cache isn't our primary cache - Andrew Tridgell 12/96 12 * 13 * Speed up hash, lru, and free list operations. Use gfp() for allocating 14 * hash table, use SLAB cache for buffer heads. SMP threading. -DaveM 15 * 16 * Added 32k buffer block sizes - these are required older ARM systems. - RMK 17 * 18 * async buffer flushing, 1999 Andrea Arcangeli <andrea@suse.de> 19 */ 20 21 #include <linux/kernel.h> 22 #include <linux/syscalls.h> 23 #include <linux/fs.h> 24 #include <linux/mm.h> 25 #include <linux/percpu.h> 26 #include <linux/slab.h> 27 #include <linux/capability.h> 28 #include <linux/blkdev.h> 29 #include <linux/file.h> 30 #include <linux/quotaops.h> 31 #include <linux/highmem.h> 32 #include <linux/export.h> 33 #include <linux/writeback.h> 34 #include <linux/hash.h> 35 #include <linux/suspend.h> 36 #include <linux/buffer_head.h> 37 #include <linux/task_io_accounting_ops.h> 38 #include <linux/bio.h> 39 #include <linux/notifier.h> 40 #include <linux/cpu.h> 41 #include <linux/bitops.h> 42 #include <linux/mpage.h> 43 #include <linux/bit_spinlock.h> 44 #include <trace/events/block.h> 45 46 static int fsync_buffers_list(spinlock_t *lock, struct list_head *list); 47 48 #define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers) 49 50 void init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private) 51 { 52 bh->b_end_io = handler; 53 bh->b_private = private; 54 } 55 EXPORT_SYMBOL(init_buffer); 56 57 inline void touch_buffer(struct buffer_head *bh) 58 { 59 trace_block_touch_buffer(bh); 60 mark_page_accessed(bh->b_page); 61 } 62 EXPORT_SYMBOL(touch_buffer); 63 64 static int sleep_on_buffer(void *word) 65 { 66 io_schedule(); 67 return 0; 68 } 69 70 void __lock_buffer(struct buffer_head *bh) 71 { 72 wait_on_bit_lock(&bh->b_state, BH_Lock, sleep_on_buffer, 73 TASK_UNINTERRUPTIBLE); 74 } 75 EXPORT_SYMBOL(__lock_buffer); 76 77 void unlock_buffer(struct buffer_head *bh) 78 { 79 clear_bit_unlock(BH_Lock, &bh->b_state); 80 smp_mb__after_clear_bit(); 81 wake_up_bit(&bh->b_state, BH_Lock); 82 } 83 EXPORT_SYMBOL(unlock_buffer); 84 85 /* 86 * Returns if the page has dirty or writeback buffers. If all the buffers 87 * are unlocked and clean then the PageDirty information is stale. If 88 * any of the pages are locked, it is assumed they are locked for IO. 89 */ 90 void buffer_check_dirty_writeback(struct page *page, 91 bool *dirty, bool *writeback) 92 { 93 struct buffer_head *head, *bh; 94 *dirty = false; 95 *writeback = false; 96 97 BUG_ON(!PageLocked(page)); 98 99 if (!page_has_buffers(page)) 100 return; 101 102 if (PageWriteback(page)) 103 *writeback = true; 104 105 head = page_buffers(page); 106 bh = head; 107 do { 108 if (buffer_locked(bh)) 109 *writeback = true; 110 111 if (buffer_dirty(bh)) 112 *dirty = true; 113 114 bh = bh->b_this_page; 115 } while (bh != head); 116 } 117 EXPORT_SYMBOL(buffer_check_dirty_writeback); 118 119 /* 120 * Block until a buffer comes unlocked. This doesn't stop it 121 * from becoming locked again - you have to lock it yourself 122 * if you want to preserve its state. 123 */ 124 void __wait_on_buffer(struct buffer_head * bh) 125 { 126 wait_on_bit(&bh->b_state, BH_Lock, sleep_on_buffer, TASK_UNINTERRUPTIBLE); 127 } 128 EXPORT_SYMBOL(__wait_on_buffer); 129 130 static void 131 __clear_page_buffers(struct page *page) 132 { 133 ClearPagePrivate(page); 134 set_page_private(page, 0); 135 page_cache_release(page); 136 } 137 138 139 static int quiet_error(struct buffer_head *bh) 140 { 141 if (!test_bit(BH_Quiet, &bh->b_state) && printk_ratelimit()) 142 return 0; 143 return 1; 144 } 145 146 147 static void buffer_io_error(struct buffer_head *bh) 148 { 149 char b[BDEVNAME_SIZE]; 150 printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n", 151 bdevname(bh->b_bdev, b), 152 (unsigned long long)bh->b_blocknr); 153 } 154 155 /* 156 * End-of-IO handler helper function which does not touch the bh after 157 * unlocking it. 158 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but 159 * a race there is benign: unlock_buffer() only use the bh's address for 160 * hashing after unlocking the buffer, so it doesn't actually touch the bh 161 * itself. 162 */ 163 static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate) 164 { 165 if (uptodate) { 166 set_buffer_uptodate(bh); 167 } else { 168 /* This happens, due to failed READA attempts. */ 169 clear_buffer_uptodate(bh); 170 } 171 unlock_buffer(bh); 172 } 173 174 /* 175 * Default synchronous end-of-IO handler.. Just mark it up-to-date and 176 * unlock the buffer. This is what ll_rw_block uses too. 177 */ 178 void end_buffer_read_sync(struct buffer_head *bh, int uptodate) 179 { 180 __end_buffer_read_notouch(bh, uptodate); 181 put_bh(bh); 182 } 183 EXPORT_SYMBOL(end_buffer_read_sync); 184 185 void end_buffer_write_sync(struct buffer_head *bh, int uptodate) 186 { 187 char b[BDEVNAME_SIZE]; 188 189 if (uptodate) { 190 set_buffer_uptodate(bh); 191 } else { 192 if (!quiet_error(bh)) { 193 buffer_io_error(bh); 194 printk(KERN_WARNING "lost page write due to " 195 "I/O error on %s\n", 196 bdevname(bh->b_bdev, b)); 197 } 198 set_buffer_write_io_error(bh); 199 clear_buffer_uptodate(bh); 200 } 201 unlock_buffer(bh); 202 put_bh(bh); 203 } 204 EXPORT_SYMBOL(end_buffer_write_sync); 205 206 /* 207 * Various filesystems appear to want __find_get_block to be non-blocking. 208 * But it's the page lock which protects the buffers. To get around this, 209 * we get exclusion from try_to_free_buffers with the blockdev mapping's 210 * private_lock. 211 * 212 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention 213 * may be quite high. This code could TryLock the page, and if that 214 * succeeds, there is no need to take private_lock. (But if 215 * private_lock is contended then so is mapping->tree_lock). 216 */ 217 static struct buffer_head * 218 __find_get_block_slow(struct block_device *bdev, sector_t block) 219 { 220 struct inode *bd_inode = bdev->bd_inode; 221 struct address_space *bd_mapping = bd_inode->i_mapping; 222 struct buffer_head *ret = NULL; 223 pgoff_t index; 224 struct buffer_head *bh; 225 struct buffer_head *head; 226 struct page *page; 227 int all_mapped = 1; 228 229 index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits); 230 page = find_get_page(bd_mapping, index); 231 if (!page) 232 goto out; 233 234 spin_lock(&bd_mapping->private_lock); 235 if (!page_has_buffers(page)) 236 goto out_unlock; 237 head = page_buffers(page); 238 bh = head; 239 do { 240 if (!buffer_mapped(bh)) 241 all_mapped = 0; 242 else if (bh->b_blocknr == block) { 243 ret = bh; 244 get_bh(bh); 245 goto out_unlock; 246 } 247 bh = bh->b_this_page; 248 } while (bh != head); 249 250 /* we might be here because some of the buffers on this page are 251 * not mapped. This is due to various races between 252 * file io on the block device and getblk. It gets dealt with 253 * elsewhere, don't buffer_error if we had some unmapped buffers 254 */ 255 if (all_mapped) { 256 char b[BDEVNAME_SIZE]; 257 258 printk("__find_get_block_slow() failed. " 259 "block=%llu, b_blocknr=%llu\n", 260 (unsigned long long)block, 261 (unsigned long long)bh->b_blocknr); 262 printk("b_state=0x%08lx, b_size=%zu\n", 263 bh->b_state, bh->b_size); 264 printk("device %s blocksize: %d\n", bdevname(bdev, b), 265 1 << bd_inode->i_blkbits); 266 } 267 out_unlock: 268 spin_unlock(&bd_mapping->private_lock); 269 page_cache_release(page); 270 out: 271 return ret; 272 } 273 274 /* 275 * Kick the writeback threads then try to free up some ZONE_NORMAL memory. 276 */ 277 static void free_more_memory(void) 278 { 279 struct zone *zone; 280 int nid; 281 282 wakeup_flusher_threads(1024, WB_REASON_FREE_MORE_MEM); 283 yield(); 284 285 for_each_online_node(nid) { 286 (void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS), 287 gfp_zone(GFP_NOFS), NULL, 288 &zone); 289 if (zone) 290 try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0, 291 GFP_NOFS, NULL); 292 } 293 } 294 295 /* 296 * I/O completion handler for block_read_full_page() - pages 297 * which come unlocked at the end of I/O. 298 */ 299 static void end_buffer_async_read(struct buffer_head *bh, int uptodate) 300 { 301 unsigned long flags; 302 struct buffer_head *first; 303 struct buffer_head *tmp; 304 struct page *page; 305 int page_uptodate = 1; 306 307 BUG_ON(!buffer_async_read(bh)); 308 309 page = bh->b_page; 310 if (uptodate) { 311 set_buffer_uptodate(bh); 312 } else { 313 clear_buffer_uptodate(bh); 314 if (!quiet_error(bh)) 315 buffer_io_error(bh); 316 SetPageError(page); 317 } 318 319 /* 320 * Be _very_ careful from here on. Bad things can happen if 321 * two buffer heads end IO at almost the same time and both 322 * decide that the page is now completely done. 323 */ 324 first = page_buffers(page); 325 local_irq_save(flags); 326 bit_spin_lock(BH_Uptodate_Lock, &first->b_state); 327 clear_buffer_async_read(bh); 328 unlock_buffer(bh); 329 tmp = bh; 330 do { 331 if (!buffer_uptodate(tmp)) 332 page_uptodate = 0; 333 if (buffer_async_read(tmp)) { 334 BUG_ON(!buffer_locked(tmp)); 335 goto still_busy; 336 } 337 tmp = tmp->b_this_page; 338 } while (tmp != bh); 339 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); 340 local_irq_restore(flags); 341 342 /* 343 * If none of the buffers had errors and they are all 344 * uptodate then we can set the page uptodate. 345 */ 346 if (page_uptodate && !PageError(page)) 347 SetPageUptodate(page); 348 unlock_page(page); 349 return; 350 351 still_busy: 352 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); 353 local_irq_restore(flags); 354 return; 355 } 356 357 /* 358 * Completion handler for block_write_full_page() - pages which are unlocked 359 * during I/O, and which have PageWriteback cleared upon I/O completion. 360 */ 361 void end_buffer_async_write(struct buffer_head *bh, int uptodate) 362 { 363 char b[BDEVNAME_SIZE]; 364 unsigned long flags; 365 struct buffer_head *first; 366 struct buffer_head *tmp; 367 struct page *page; 368 369 BUG_ON(!buffer_async_write(bh)); 370 371 page = bh->b_page; 372 if (uptodate) { 373 set_buffer_uptodate(bh); 374 } else { 375 if (!quiet_error(bh)) { 376 buffer_io_error(bh); 377 printk(KERN_WARNING "lost page write due to " 378 "I/O error on %s\n", 379 bdevname(bh->b_bdev, b)); 380 } 381 set_bit(AS_EIO, &page->mapping->flags); 382 set_buffer_write_io_error(bh); 383 clear_buffer_uptodate(bh); 384 SetPageError(page); 385 } 386 387 first = page_buffers(page); 388 local_irq_save(flags); 389 bit_spin_lock(BH_Uptodate_Lock, &first->b_state); 390 391 clear_buffer_async_write(bh); 392 unlock_buffer(bh); 393 tmp = bh->b_this_page; 394 while (tmp != bh) { 395 if (buffer_async_write(tmp)) { 396 BUG_ON(!buffer_locked(tmp)); 397 goto still_busy; 398 } 399 tmp = tmp->b_this_page; 400 } 401 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); 402 local_irq_restore(flags); 403 end_page_writeback(page); 404 return; 405 406 still_busy: 407 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); 408 local_irq_restore(flags); 409 return; 410 } 411 EXPORT_SYMBOL(end_buffer_async_write); 412 413 /* 414 * If a page's buffers are under async readin (end_buffer_async_read 415 * completion) then there is a possibility that another thread of 416 * control could lock one of the buffers after it has completed 417 * but while some of the other buffers have not completed. This 418 * locked buffer would confuse end_buffer_async_read() into not unlocking 419 * the page. So the absence of BH_Async_Read tells end_buffer_async_read() 420 * that this buffer is not under async I/O. 421 * 422 * The page comes unlocked when it has no locked buffer_async buffers 423 * left. 424 * 425 * PageLocked prevents anyone starting new async I/O reads any of 426 * the buffers. 427 * 428 * PageWriteback is used to prevent simultaneous writeout of the same 429 * page. 430 * 431 * PageLocked prevents anyone from starting writeback of a page which is 432 * under read I/O (PageWriteback is only ever set against a locked page). 433 */ 434 static void mark_buffer_async_read(struct buffer_head *bh) 435 { 436 bh->b_end_io = end_buffer_async_read; 437 set_buffer_async_read(bh); 438 } 439 440 static void mark_buffer_async_write_endio(struct buffer_head *bh, 441 bh_end_io_t *handler) 442 { 443 bh->b_end_io = handler; 444 set_buffer_async_write(bh); 445 } 446 447 void mark_buffer_async_write(struct buffer_head *bh) 448 { 449 mark_buffer_async_write_endio(bh, end_buffer_async_write); 450 } 451 EXPORT_SYMBOL(mark_buffer_async_write); 452 453 454 /* 455 * fs/buffer.c contains helper functions for buffer-backed address space's 456 * fsync functions. A common requirement for buffer-based filesystems is 457 * that certain data from the backing blockdev needs to be written out for 458 * a successful fsync(). For example, ext2 indirect blocks need to be 459 * written back and waited upon before fsync() returns. 460 * 461 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(), 462 * inode_has_buffers() and invalidate_inode_buffers() are provided for the 463 * management of a list of dependent buffers at ->i_mapping->private_list. 464 * 465 * Locking is a little subtle: try_to_free_buffers() will remove buffers 466 * from their controlling inode's queue when they are being freed. But 467 * try_to_free_buffers() will be operating against the *blockdev* mapping 468 * at the time, not against the S_ISREG file which depends on those buffers. 469 * So the locking for private_list is via the private_lock in the address_space 470 * which backs the buffers. Which is different from the address_space 471 * against which the buffers are listed. So for a particular address_space, 472 * mapping->private_lock does *not* protect mapping->private_list! In fact, 473 * mapping->private_list will always be protected by the backing blockdev's 474 * ->private_lock. 475 * 476 * Which introduces a requirement: all buffers on an address_space's 477 * ->private_list must be from the same address_space: the blockdev's. 478 * 479 * address_spaces which do not place buffers at ->private_list via these 480 * utility functions are free to use private_lock and private_list for 481 * whatever they want. The only requirement is that list_empty(private_list) 482 * be true at clear_inode() time. 483 * 484 * FIXME: clear_inode should not call invalidate_inode_buffers(). The 485 * filesystems should do that. invalidate_inode_buffers() should just go 486 * BUG_ON(!list_empty). 487 * 488 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should 489 * take an address_space, not an inode. And it should be called 490 * mark_buffer_dirty_fsync() to clearly define why those buffers are being 491 * queued up. 492 * 493 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the 494 * list if it is already on a list. Because if the buffer is on a list, 495 * it *must* already be on the right one. If not, the filesystem is being 496 * silly. This will save a ton of locking. But first we have to ensure 497 * that buffers are taken *off* the old inode's list when they are freed 498 * (presumably in truncate). That requires careful auditing of all 499 * filesystems (do it inside bforget()). It could also be done by bringing 500 * b_inode back. 501 */ 502 503 /* 504 * The buffer's backing address_space's private_lock must be held 505 */ 506 static void __remove_assoc_queue(struct buffer_head *bh) 507 { 508 list_del_init(&bh->b_assoc_buffers); 509 WARN_ON(!bh->b_assoc_map); 510 if (buffer_write_io_error(bh)) 511 set_bit(AS_EIO, &bh->b_assoc_map->flags); 512 bh->b_assoc_map = NULL; 513 } 514 515 int inode_has_buffers(struct inode *inode) 516 { 517 return !list_empty(&inode->i_data.private_list); 518 } 519 520 /* 521 * osync is designed to support O_SYNC io. It waits synchronously for 522 * all already-submitted IO to complete, but does not queue any new 523 * writes to the disk. 524 * 525 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as 526 * you dirty the buffers, and then use osync_inode_buffers to wait for 527 * completion. Any other dirty buffers which are not yet queued for 528 * write will not be flushed to disk by the osync. 529 */ 530 static int osync_buffers_list(spinlock_t *lock, struct list_head *list) 531 { 532 struct buffer_head *bh; 533 struct list_head *p; 534 int err = 0; 535 536 spin_lock(lock); 537 repeat: 538 list_for_each_prev(p, list) { 539 bh = BH_ENTRY(p); 540 if (buffer_locked(bh)) { 541 get_bh(bh); 542 spin_unlock(lock); 543 wait_on_buffer(bh); 544 if (!buffer_uptodate(bh)) 545 err = -EIO; 546 brelse(bh); 547 spin_lock(lock); 548 goto repeat; 549 } 550 } 551 spin_unlock(lock); 552 return err; 553 } 554 555 static void do_thaw_one(struct super_block *sb, void *unused) 556 { 557 char b[BDEVNAME_SIZE]; 558 while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb)) 559 printk(KERN_WARNING "Emergency Thaw on %s\n", 560 bdevname(sb->s_bdev, b)); 561 } 562 563 static void do_thaw_all(struct work_struct *work) 564 { 565 iterate_supers(do_thaw_one, NULL); 566 kfree(work); 567 printk(KERN_WARNING "Emergency Thaw complete\n"); 568 } 569 570 /** 571 * emergency_thaw_all -- forcibly thaw every frozen filesystem 572 * 573 * Used for emergency unfreeze of all filesystems via SysRq 574 */ 575 void emergency_thaw_all(void) 576 { 577 struct work_struct *work; 578 579 work = kmalloc(sizeof(*work), GFP_ATOMIC); 580 if (work) { 581 INIT_WORK(work, do_thaw_all); 582 schedule_work(work); 583 } 584 } 585 586 /** 587 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers 588 * @mapping: the mapping which wants those buffers written 589 * 590 * Starts I/O against the buffers at mapping->private_list, and waits upon 591 * that I/O. 592 * 593 * Basically, this is a convenience function for fsync(). 594 * @mapping is a file or directory which needs those buffers to be written for 595 * a successful fsync(). 596 */ 597 int sync_mapping_buffers(struct address_space *mapping) 598 { 599 struct address_space *buffer_mapping = mapping->private_data; 600 601 if (buffer_mapping == NULL || list_empty(&mapping->private_list)) 602 return 0; 603 604 return fsync_buffers_list(&buffer_mapping->private_lock, 605 &mapping->private_list); 606 } 607 EXPORT_SYMBOL(sync_mapping_buffers); 608 609 /* 610 * Called when we've recently written block `bblock', and it is known that 611 * `bblock' was for a buffer_boundary() buffer. This means that the block at 612 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's 613 * dirty, schedule it for IO. So that indirects merge nicely with their data. 614 */ 615 void write_boundary_block(struct block_device *bdev, 616 sector_t bblock, unsigned blocksize) 617 { 618 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize); 619 if (bh) { 620 if (buffer_dirty(bh)) 621 ll_rw_block(WRITE, 1, &bh); 622 put_bh(bh); 623 } 624 } 625 626 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode) 627 { 628 struct address_space *mapping = inode->i_mapping; 629 struct address_space *buffer_mapping = bh->b_page->mapping; 630 631 mark_buffer_dirty(bh); 632 if (!mapping->private_data) { 633 mapping->private_data = buffer_mapping; 634 } else { 635 BUG_ON(mapping->private_data != buffer_mapping); 636 } 637 if (!bh->b_assoc_map) { 638 spin_lock(&buffer_mapping->private_lock); 639 list_move_tail(&bh->b_assoc_buffers, 640 &mapping->private_list); 641 bh->b_assoc_map = mapping; 642 spin_unlock(&buffer_mapping->private_lock); 643 } 644 } 645 EXPORT_SYMBOL(mark_buffer_dirty_inode); 646 647 /* 648 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode 649 * dirty. 650 * 651 * If warn is true, then emit a warning if the page is not uptodate and has 652 * not been truncated. 653 */ 654 static void __set_page_dirty(struct page *page, 655 struct address_space *mapping, int warn) 656 { 657 spin_lock_irq(&mapping->tree_lock); 658 if (page->mapping) { /* Race with truncate? */ 659 WARN_ON_ONCE(warn && !PageUptodate(page)); 660 account_page_dirtied(page, mapping); 661 radix_tree_tag_set(&mapping->page_tree, 662 page_index(page), PAGECACHE_TAG_DIRTY); 663 } 664 spin_unlock_irq(&mapping->tree_lock); 665 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); 666 } 667 668 /* 669 * Add a page to the dirty page list. 670 * 671 * It is a sad fact of life that this function is called from several places 672 * deeply under spinlocking. It may not sleep. 673 * 674 * If the page has buffers, the uptodate buffers are set dirty, to preserve 675 * dirty-state coherency between the page and the buffers. It the page does 676 * not have buffers then when they are later attached they will all be set 677 * dirty. 678 * 679 * The buffers are dirtied before the page is dirtied. There's a small race 680 * window in which a writepage caller may see the page cleanness but not the 681 * buffer dirtiness. That's fine. If this code were to set the page dirty 682 * before the buffers, a concurrent writepage caller could clear the page dirty 683 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean 684 * page on the dirty page list. 685 * 686 * We use private_lock to lock against try_to_free_buffers while using the 687 * page's buffer list. Also use this to protect against clean buffers being 688 * added to the page after it was set dirty. 689 * 690 * FIXME: may need to call ->reservepage here as well. That's rather up to the 691 * address_space though. 692 */ 693 int __set_page_dirty_buffers(struct page *page) 694 { 695 int newly_dirty; 696 struct address_space *mapping = page_mapping(page); 697 698 if (unlikely(!mapping)) 699 return !TestSetPageDirty(page); 700 701 spin_lock(&mapping->private_lock); 702 if (page_has_buffers(page)) { 703 struct buffer_head *head = page_buffers(page); 704 struct buffer_head *bh = head; 705 706 do { 707 set_buffer_dirty(bh); 708 bh = bh->b_this_page; 709 } while (bh != head); 710 } 711 newly_dirty = !TestSetPageDirty(page); 712 spin_unlock(&mapping->private_lock); 713 714 if (newly_dirty) 715 __set_page_dirty(page, mapping, 1); 716 return newly_dirty; 717 } 718 EXPORT_SYMBOL(__set_page_dirty_buffers); 719 720 /* 721 * Write out and wait upon a list of buffers. 722 * 723 * We have conflicting pressures: we want to make sure that all 724 * initially dirty buffers get waited on, but that any subsequently 725 * dirtied buffers don't. After all, we don't want fsync to last 726 * forever if somebody is actively writing to the file. 727 * 728 * Do this in two main stages: first we copy dirty buffers to a 729 * temporary inode list, queueing the writes as we go. Then we clean 730 * up, waiting for those writes to complete. 731 * 732 * During this second stage, any subsequent updates to the file may end 733 * up refiling the buffer on the original inode's dirty list again, so 734 * there is a chance we will end up with a buffer queued for write but 735 * not yet completed on that list. So, as a final cleanup we go through 736 * the osync code to catch these locked, dirty buffers without requeuing 737 * any newly dirty buffers for write. 738 */ 739 static int fsync_buffers_list(spinlock_t *lock, struct list_head *list) 740 { 741 struct buffer_head *bh; 742 struct list_head tmp; 743 struct address_space *mapping; 744 int err = 0, err2; 745 struct blk_plug plug; 746 747 INIT_LIST_HEAD(&tmp); 748 blk_start_plug(&plug); 749 750 spin_lock(lock); 751 while (!list_empty(list)) { 752 bh = BH_ENTRY(list->next); 753 mapping = bh->b_assoc_map; 754 __remove_assoc_queue(bh); 755 /* Avoid race with mark_buffer_dirty_inode() which does 756 * a lockless check and we rely on seeing the dirty bit */ 757 smp_mb(); 758 if (buffer_dirty(bh) || buffer_locked(bh)) { 759 list_add(&bh->b_assoc_buffers, &tmp); 760 bh->b_assoc_map = mapping; 761 if (buffer_dirty(bh)) { 762 get_bh(bh); 763 spin_unlock(lock); 764 /* 765 * Ensure any pending I/O completes so that 766 * write_dirty_buffer() actually writes the 767 * current contents - it is a noop if I/O is 768 * still in flight on potentially older 769 * contents. 770 */ 771 write_dirty_buffer(bh, WRITE_SYNC); 772 773 /* 774 * Kick off IO for the previous mapping. Note 775 * that we will not run the very last mapping, 776 * wait_on_buffer() will do that for us 777 * through sync_buffer(). 778 */ 779 brelse(bh); 780 spin_lock(lock); 781 } 782 } 783 } 784 785 spin_unlock(lock); 786 blk_finish_plug(&plug); 787 spin_lock(lock); 788 789 while (!list_empty(&tmp)) { 790 bh = BH_ENTRY(tmp.prev); 791 get_bh(bh); 792 mapping = bh->b_assoc_map; 793 __remove_assoc_queue(bh); 794 /* Avoid race with mark_buffer_dirty_inode() which does 795 * a lockless check and we rely on seeing the dirty bit */ 796 smp_mb(); 797 if (buffer_dirty(bh)) { 798 list_add(&bh->b_assoc_buffers, 799 &mapping->private_list); 800 bh->b_assoc_map = mapping; 801 } 802 spin_unlock(lock); 803 wait_on_buffer(bh); 804 if (!buffer_uptodate(bh)) 805 err = -EIO; 806 brelse(bh); 807 spin_lock(lock); 808 } 809 810 spin_unlock(lock); 811 err2 = osync_buffers_list(lock, list); 812 if (err) 813 return err; 814 else 815 return err2; 816 } 817 818 /* 819 * Invalidate any and all dirty buffers on a given inode. We are 820 * probably unmounting the fs, but that doesn't mean we have already 821 * done a sync(). Just drop the buffers from the inode list. 822 * 823 * NOTE: we take the inode's blockdev's mapping's private_lock. Which 824 * assumes that all the buffers are against the blockdev. Not true 825 * for reiserfs. 826 */ 827 void invalidate_inode_buffers(struct inode *inode) 828 { 829 if (inode_has_buffers(inode)) { 830 struct address_space *mapping = &inode->i_data; 831 struct list_head *list = &mapping->private_list; 832 struct address_space *buffer_mapping = mapping->private_data; 833 834 spin_lock(&buffer_mapping->private_lock); 835 while (!list_empty(list)) 836 __remove_assoc_queue(BH_ENTRY(list->next)); 837 spin_unlock(&buffer_mapping->private_lock); 838 } 839 } 840 EXPORT_SYMBOL(invalidate_inode_buffers); 841 842 /* 843 * Remove any clean buffers from the inode's buffer list. This is called 844 * when we're trying to free the inode itself. Those buffers can pin it. 845 * 846 * Returns true if all buffers were removed. 847 */ 848 int remove_inode_buffers(struct inode *inode) 849 { 850 int ret = 1; 851 852 if (inode_has_buffers(inode)) { 853 struct address_space *mapping = &inode->i_data; 854 struct list_head *list = &mapping->private_list; 855 struct address_space *buffer_mapping = mapping->private_data; 856 857 spin_lock(&buffer_mapping->private_lock); 858 while (!list_empty(list)) { 859 struct buffer_head *bh = BH_ENTRY(list->next); 860 if (buffer_dirty(bh)) { 861 ret = 0; 862 break; 863 } 864 __remove_assoc_queue(bh); 865 } 866 spin_unlock(&buffer_mapping->private_lock); 867 } 868 return ret; 869 } 870 871 /* 872 * Create the appropriate buffers when given a page for data area and 873 * the size of each buffer.. Use the bh->b_this_page linked list to 874 * follow the buffers created. Return NULL if unable to create more 875 * buffers. 876 * 877 * The retry flag is used to differentiate async IO (paging, swapping) 878 * which may not fail from ordinary buffer allocations. 879 */ 880 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, 881 int retry) 882 { 883 struct buffer_head *bh, *head; 884 long offset; 885 886 try_again: 887 head = NULL; 888 offset = PAGE_SIZE; 889 while ((offset -= size) >= 0) { 890 bh = alloc_buffer_head(GFP_NOFS); 891 if (!bh) 892 goto no_grow; 893 894 bh->b_this_page = head; 895 bh->b_blocknr = -1; 896 head = bh; 897 898 bh->b_size = size; 899 900 /* Link the buffer to its page */ 901 set_bh_page(bh, page, offset); 902 } 903 return head; 904 /* 905 * In case anything failed, we just free everything we got. 906 */ 907 no_grow: 908 if (head) { 909 do { 910 bh = head; 911 head = head->b_this_page; 912 free_buffer_head(bh); 913 } while (head); 914 } 915 916 /* 917 * Return failure for non-async IO requests. Async IO requests 918 * are not allowed to fail, so we have to wait until buffer heads 919 * become available. But we don't want tasks sleeping with 920 * partially complete buffers, so all were released above. 921 */ 922 if (!retry) 923 return NULL; 924 925 /* We're _really_ low on memory. Now we just 926 * wait for old buffer heads to become free due to 927 * finishing IO. Since this is an async request and 928 * the reserve list is empty, we're sure there are 929 * async buffer heads in use. 930 */ 931 free_more_memory(); 932 goto try_again; 933 } 934 EXPORT_SYMBOL_GPL(alloc_page_buffers); 935 936 static inline void 937 link_dev_buffers(struct page *page, struct buffer_head *head) 938 { 939 struct buffer_head *bh, *tail; 940 941 bh = head; 942 do { 943 tail = bh; 944 bh = bh->b_this_page; 945 } while (bh); 946 tail->b_this_page = head; 947 attach_page_buffers(page, head); 948 } 949 950 static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size) 951 { 952 sector_t retval = ~((sector_t)0); 953 loff_t sz = i_size_read(bdev->bd_inode); 954 955 if (sz) { 956 unsigned int sizebits = blksize_bits(size); 957 retval = (sz >> sizebits); 958 } 959 return retval; 960 } 961 962 /* 963 * Initialise the state of a blockdev page's buffers. 964 */ 965 static sector_t 966 init_page_buffers(struct page *page, struct block_device *bdev, 967 sector_t block, int size) 968 { 969 struct buffer_head *head = page_buffers(page); 970 struct buffer_head *bh = head; 971 int uptodate = PageUptodate(page); 972 sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode), size); 973 974 do { 975 if (!buffer_mapped(bh)) { 976 init_buffer(bh, NULL, NULL); 977 bh->b_bdev = bdev; 978 bh->b_blocknr = block; 979 if (uptodate) 980 set_buffer_uptodate(bh); 981 if (block < end_block) 982 set_buffer_mapped(bh); 983 } 984 block++; 985 bh = bh->b_this_page; 986 } while (bh != head); 987 988 /* 989 * Caller needs to validate requested block against end of device. 990 */ 991 return end_block; 992 } 993 994 /* 995 * Create the page-cache page that contains the requested block. 996 * 997 * This is used purely for blockdev mappings. 998 */ 999 static int 1000 grow_dev_page(struct block_device *bdev, sector_t block, 1001 pgoff_t index, int size, int sizebits) 1002 { 1003 struct inode *inode = bdev->bd_inode; 1004 struct page *page; 1005 struct buffer_head *bh; 1006 sector_t end_block; 1007 int ret = 0; /* Will call free_more_memory() */ 1008 1009 page = find_or_create_page(inode->i_mapping, index, 1010 (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE); 1011 if (!page) 1012 return ret; 1013 1014 BUG_ON(!PageLocked(page)); 1015 1016 if (page_has_buffers(page)) { 1017 bh = page_buffers(page); 1018 if (bh->b_size == size) { 1019 end_block = init_page_buffers(page, bdev, 1020 index << sizebits, size); 1021 goto done; 1022 } 1023 if (!try_to_free_buffers(page)) 1024 goto failed; 1025 } 1026 1027 /* 1028 * Allocate some buffers for this page 1029 */ 1030 bh = alloc_page_buffers(page, size, 0); 1031 if (!bh) 1032 goto failed; 1033 1034 /* 1035 * Link the page to the buffers and initialise them. Take the 1036 * lock to be atomic wrt __find_get_block(), which does not 1037 * run under the page lock. 1038 */ 1039 spin_lock(&inode->i_mapping->private_lock); 1040 link_dev_buffers(page, bh); 1041 end_block = init_page_buffers(page, bdev, index << sizebits, size); 1042 spin_unlock(&inode->i_mapping->private_lock); 1043 done: 1044 ret = (block < end_block) ? 1 : -ENXIO; 1045 failed: 1046 unlock_page(page); 1047 page_cache_release(page); 1048 return ret; 1049 } 1050 1051 /* 1052 * Create buffers for the specified block device block's page. If 1053 * that page was dirty, the buffers are set dirty also. 1054 */ 1055 static int 1056 grow_buffers(struct block_device *bdev, sector_t block, int size) 1057 { 1058 pgoff_t index; 1059 int sizebits; 1060 1061 sizebits = -1; 1062 do { 1063 sizebits++; 1064 } while ((size << sizebits) < PAGE_SIZE); 1065 1066 index = block >> sizebits; 1067 1068 /* 1069 * Check for a block which wants to lie outside our maximum possible 1070 * pagecache index. (this comparison is done using sector_t types). 1071 */ 1072 if (unlikely(index != block >> sizebits)) { 1073 char b[BDEVNAME_SIZE]; 1074 1075 printk(KERN_ERR "%s: requested out-of-range block %llu for " 1076 "device %s\n", 1077 __func__, (unsigned long long)block, 1078 bdevname(bdev, b)); 1079 return -EIO; 1080 } 1081 1082 /* Create a page with the proper size buffers.. */ 1083 return grow_dev_page(bdev, block, index, size, sizebits); 1084 } 1085 1086 static struct buffer_head * 1087 __getblk_slow(struct block_device *bdev, sector_t block, int size) 1088 { 1089 /* Size must be multiple of hard sectorsize */ 1090 if (unlikely(size & (bdev_logical_block_size(bdev)-1) || 1091 (size < 512 || size > PAGE_SIZE))) { 1092 printk(KERN_ERR "getblk(): invalid block size %d requested\n", 1093 size); 1094 printk(KERN_ERR "logical block size: %d\n", 1095 bdev_logical_block_size(bdev)); 1096 1097 dump_stack(); 1098 return NULL; 1099 } 1100 1101 for (;;) { 1102 struct buffer_head *bh; 1103 int ret; 1104 1105 bh = __find_get_block(bdev, block, size); 1106 if (bh) 1107 return bh; 1108 1109 ret = grow_buffers(bdev, block, size); 1110 if (ret < 0) 1111 return NULL; 1112 if (ret == 0) 1113 free_more_memory(); 1114 } 1115 } 1116 1117 /* 1118 * The relationship between dirty buffers and dirty pages: 1119 * 1120 * Whenever a page has any dirty buffers, the page's dirty bit is set, and 1121 * the page is tagged dirty in its radix tree. 1122 * 1123 * At all times, the dirtiness of the buffers represents the dirtiness of 1124 * subsections of the page. If the page has buffers, the page dirty bit is 1125 * merely a hint about the true dirty state. 1126 * 1127 * When a page is set dirty in its entirety, all its buffers are marked dirty 1128 * (if the page has buffers). 1129 * 1130 * When a buffer is marked dirty, its page is dirtied, but the page's other 1131 * buffers are not. 1132 * 1133 * Also. When blockdev buffers are explicitly read with bread(), they 1134 * individually become uptodate. But their backing page remains not 1135 * uptodate - even if all of its buffers are uptodate. A subsequent 1136 * block_read_full_page() against that page will discover all the uptodate 1137 * buffers, will set the page uptodate and will perform no I/O. 1138 */ 1139 1140 /** 1141 * mark_buffer_dirty - mark a buffer_head as needing writeout 1142 * @bh: the buffer_head to mark dirty 1143 * 1144 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its 1145 * backing page dirty, then tag the page as dirty in its address_space's radix 1146 * tree and then attach the address_space's inode to its superblock's dirty 1147 * inode list. 1148 * 1149 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock, 1150 * mapping->tree_lock and mapping->host->i_lock. 1151 */ 1152 void mark_buffer_dirty(struct buffer_head *bh) 1153 { 1154 WARN_ON_ONCE(!buffer_uptodate(bh)); 1155 1156 trace_block_dirty_buffer(bh); 1157 1158 /* 1159 * Very *carefully* optimize the it-is-already-dirty case. 1160 * 1161 * Don't let the final "is it dirty" escape to before we 1162 * perhaps modified the buffer. 1163 */ 1164 if (buffer_dirty(bh)) { 1165 smp_mb(); 1166 if (buffer_dirty(bh)) 1167 return; 1168 } 1169 1170 if (!test_set_buffer_dirty(bh)) { 1171 struct page *page = bh->b_page; 1172 if (!TestSetPageDirty(page)) { 1173 struct address_space *mapping = page_mapping(page); 1174 if (mapping) 1175 __set_page_dirty(page, mapping, 0); 1176 } 1177 } 1178 } 1179 EXPORT_SYMBOL(mark_buffer_dirty); 1180 1181 /* 1182 * Decrement a buffer_head's reference count. If all buffers against a page 1183 * have zero reference count, are clean and unlocked, and if the page is clean 1184 * and unlocked then try_to_free_buffers() may strip the buffers from the page 1185 * in preparation for freeing it (sometimes, rarely, buffers are removed from 1186 * a page but it ends up not being freed, and buffers may later be reattached). 1187 */ 1188 void __brelse(struct buffer_head * buf) 1189 { 1190 if (atomic_read(&buf->b_count)) { 1191 put_bh(buf); 1192 return; 1193 } 1194 WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n"); 1195 } 1196 EXPORT_SYMBOL(__brelse); 1197 1198 /* 1199 * bforget() is like brelse(), except it discards any 1200 * potentially dirty data. 1201 */ 1202 void __bforget(struct buffer_head *bh) 1203 { 1204 clear_buffer_dirty(bh); 1205 if (bh->b_assoc_map) { 1206 struct address_space *buffer_mapping = bh->b_page->mapping; 1207 1208 spin_lock(&buffer_mapping->private_lock); 1209 list_del_init(&bh->b_assoc_buffers); 1210 bh->b_assoc_map = NULL; 1211 spin_unlock(&buffer_mapping->private_lock); 1212 } 1213 __brelse(bh); 1214 } 1215 EXPORT_SYMBOL(__bforget); 1216 1217 static struct buffer_head *__bread_slow(struct buffer_head *bh) 1218 { 1219 lock_buffer(bh); 1220 if (buffer_uptodate(bh)) { 1221 unlock_buffer(bh); 1222 return bh; 1223 } else { 1224 get_bh(bh); 1225 bh->b_end_io = end_buffer_read_sync; 1226 submit_bh(READ, bh); 1227 wait_on_buffer(bh); 1228 if (buffer_uptodate(bh)) 1229 return bh; 1230 } 1231 brelse(bh); 1232 return NULL; 1233 } 1234 1235 /* 1236 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block(). 1237 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their 1238 * refcount elevated by one when they're in an LRU. A buffer can only appear 1239 * once in a particular CPU's LRU. A single buffer can be present in multiple 1240 * CPU's LRUs at the same time. 1241 * 1242 * This is a transparent caching front-end to sb_bread(), sb_getblk() and 1243 * sb_find_get_block(). 1244 * 1245 * The LRUs themselves only need locking against invalidate_bh_lrus. We use 1246 * a local interrupt disable for that. 1247 */ 1248 1249 #define BH_LRU_SIZE 8 1250 1251 struct bh_lru { 1252 struct buffer_head *bhs[BH_LRU_SIZE]; 1253 }; 1254 1255 static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }}; 1256 1257 #ifdef CONFIG_SMP 1258 #define bh_lru_lock() local_irq_disable() 1259 #define bh_lru_unlock() local_irq_enable() 1260 #else 1261 #define bh_lru_lock() preempt_disable() 1262 #define bh_lru_unlock() preempt_enable() 1263 #endif 1264 1265 static inline void check_irqs_on(void) 1266 { 1267 #ifdef irqs_disabled 1268 BUG_ON(irqs_disabled()); 1269 #endif 1270 } 1271 1272 /* 1273 * The LRU management algorithm is dopey-but-simple. Sorry. 1274 */ 1275 static void bh_lru_install(struct buffer_head *bh) 1276 { 1277 struct buffer_head *evictee = NULL; 1278 1279 check_irqs_on(); 1280 bh_lru_lock(); 1281 if (__this_cpu_read(bh_lrus.bhs[0]) != bh) { 1282 struct buffer_head *bhs[BH_LRU_SIZE]; 1283 int in; 1284 int out = 0; 1285 1286 get_bh(bh); 1287 bhs[out++] = bh; 1288 for (in = 0; in < BH_LRU_SIZE; in++) { 1289 struct buffer_head *bh2 = 1290 __this_cpu_read(bh_lrus.bhs[in]); 1291 1292 if (bh2 == bh) { 1293 __brelse(bh2); 1294 } else { 1295 if (out >= BH_LRU_SIZE) { 1296 BUG_ON(evictee != NULL); 1297 evictee = bh2; 1298 } else { 1299 bhs[out++] = bh2; 1300 } 1301 } 1302 } 1303 while (out < BH_LRU_SIZE) 1304 bhs[out++] = NULL; 1305 memcpy(__this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs)); 1306 } 1307 bh_lru_unlock(); 1308 1309 if (evictee) 1310 __brelse(evictee); 1311 } 1312 1313 /* 1314 * Look up the bh in this cpu's LRU. If it's there, move it to the head. 1315 */ 1316 static struct buffer_head * 1317 lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size) 1318 { 1319 struct buffer_head *ret = NULL; 1320 unsigned int i; 1321 1322 check_irqs_on(); 1323 bh_lru_lock(); 1324 for (i = 0; i < BH_LRU_SIZE; i++) { 1325 struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]); 1326 1327 if (bh && bh->b_bdev == bdev && 1328 bh->b_blocknr == block && bh->b_size == size) { 1329 if (i) { 1330 while (i) { 1331 __this_cpu_write(bh_lrus.bhs[i], 1332 __this_cpu_read(bh_lrus.bhs[i - 1])); 1333 i--; 1334 } 1335 __this_cpu_write(bh_lrus.bhs[0], bh); 1336 } 1337 get_bh(bh); 1338 ret = bh; 1339 break; 1340 } 1341 } 1342 bh_lru_unlock(); 1343 return ret; 1344 } 1345 1346 /* 1347 * Perform a pagecache lookup for the matching buffer. If it's there, refresh 1348 * it in the LRU and mark it as accessed. If it is not present then return 1349 * NULL 1350 */ 1351 struct buffer_head * 1352 __find_get_block(struct block_device *bdev, sector_t block, unsigned size) 1353 { 1354 struct buffer_head *bh = lookup_bh_lru(bdev, block, size); 1355 1356 if (bh == NULL) { 1357 bh = __find_get_block_slow(bdev, block); 1358 if (bh) 1359 bh_lru_install(bh); 1360 } 1361 if (bh) 1362 touch_buffer(bh); 1363 return bh; 1364 } 1365 EXPORT_SYMBOL(__find_get_block); 1366 1367 /* 1368 * __getblk will locate (and, if necessary, create) the buffer_head 1369 * which corresponds to the passed block_device, block and size. The 1370 * returned buffer has its reference count incremented. 1371 * 1372 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers() 1373 * attempt is failing. FIXME, perhaps? 1374 */ 1375 struct buffer_head * 1376 __getblk(struct block_device *bdev, sector_t block, unsigned size) 1377 { 1378 struct buffer_head *bh = __find_get_block(bdev, block, size); 1379 1380 might_sleep(); 1381 if (bh == NULL) 1382 bh = __getblk_slow(bdev, block, size); 1383 return bh; 1384 } 1385 EXPORT_SYMBOL(__getblk); 1386 1387 /* 1388 * Do async read-ahead on a buffer.. 1389 */ 1390 void __breadahead(struct block_device *bdev, sector_t block, unsigned size) 1391 { 1392 struct buffer_head *bh = __getblk(bdev, block, size); 1393 if (likely(bh)) { 1394 ll_rw_block(READA, 1, &bh); 1395 brelse(bh); 1396 } 1397 } 1398 EXPORT_SYMBOL(__breadahead); 1399 1400 /** 1401 * __bread() - reads a specified block and returns the bh 1402 * @bdev: the block_device to read from 1403 * @block: number of block 1404 * @size: size (in bytes) to read 1405 * 1406 * Reads a specified block, and returns buffer head that contains it. 1407 * It returns NULL if the block was unreadable. 1408 */ 1409 struct buffer_head * 1410 __bread(struct block_device *bdev, sector_t block, unsigned size) 1411 { 1412 struct buffer_head *bh = __getblk(bdev, block, size); 1413 1414 if (likely(bh) && !buffer_uptodate(bh)) 1415 bh = __bread_slow(bh); 1416 return bh; 1417 } 1418 EXPORT_SYMBOL(__bread); 1419 1420 /* 1421 * invalidate_bh_lrus() is called rarely - but not only at unmount. 1422 * This doesn't race because it runs in each cpu either in irq 1423 * or with preempt disabled. 1424 */ 1425 static void invalidate_bh_lru(void *arg) 1426 { 1427 struct bh_lru *b = &get_cpu_var(bh_lrus); 1428 int i; 1429 1430 for (i = 0; i < BH_LRU_SIZE; i++) { 1431 brelse(b->bhs[i]); 1432 b->bhs[i] = NULL; 1433 } 1434 put_cpu_var(bh_lrus); 1435 } 1436 1437 static bool has_bh_in_lru(int cpu, void *dummy) 1438 { 1439 struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu); 1440 int i; 1441 1442 for (i = 0; i < BH_LRU_SIZE; i++) { 1443 if (b->bhs[i]) 1444 return 1; 1445 } 1446 1447 return 0; 1448 } 1449 1450 void invalidate_bh_lrus(void) 1451 { 1452 on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL); 1453 } 1454 EXPORT_SYMBOL_GPL(invalidate_bh_lrus); 1455 1456 void set_bh_page(struct buffer_head *bh, 1457 struct page *page, unsigned long offset) 1458 { 1459 bh->b_page = page; 1460 BUG_ON(offset >= PAGE_SIZE); 1461 if (PageHighMem(page)) 1462 /* 1463 * This catches illegal uses and preserves the offset: 1464 */ 1465 bh->b_data = (char *)(0 + offset); 1466 else 1467 bh->b_data = page_address(page) + offset; 1468 } 1469 EXPORT_SYMBOL(set_bh_page); 1470 1471 /* 1472 * Called when truncating a buffer on a page completely. 1473 */ 1474 static void discard_buffer(struct buffer_head * bh) 1475 { 1476 lock_buffer(bh); 1477 clear_buffer_dirty(bh); 1478 bh->b_bdev = NULL; 1479 clear_buffer_mapped(bh); 1480 clear_buffer_req(bh); 1481 clear_buffer_new(bh); 1482 clear_buffer_delay(bh); 1483 clear_buffer_unwritten(bh); 1484 unlock_buffer(bh); 1485 } 1486 1487 /** 1488 * block_invalidatepage - invalidate part or all of a buffer-backed page 1489 * 1490 * @page: the page which is affected 1491 * @offset: start of the range to invalidate 1492 * @length: length of the range to invalidate 1493 * 1494 * block_invalidatepage() is called when all or part of the page has become 1495 * invalidated by a truncate operation. 1496 * 1497 * block_invalidatepage() does not have to release all buffers, but it must 1498 * ensure that no dirty buffer is left outside @offset and that no I/O 1499 * is underway against any of the blocks which are outside the truncation 1500 * point. Because the caller is about to free (and possibly reuse) those 1501 * blocks on-disk. 1502 */ 1503 void block_invalidatepage(struct page *page, unsigned int offset, 1504 unsigned int length) 1505 { 1506 struct buffer_head *head, *bh, *next; 1507 unsigned int curr_off = 0; 1508 unsigned int stop = length + offset; 1509 1510 BUG_ON(!PageLocked(page)); 1511 if (!page_has_buffers(page)) 1512 goto out; 1513 1514 /* 1515 * Check for overflow 1516 */ 1517 BUG_ON(stop > PAGE_CACHE_SIZE || stop < length); 1518 1519 head = page_buffers(page); 1520 bh = head; 1521 do { 1522 unsigned int next_off = curr_off + bh->b_size; 1523 next = bh->b_this_page; 1524 1525 /* 1526 * Are we still fully in range ? 1527 */ 1528 if (next_off > stop) 1529 goto out; 1530 1531 /* 1532 * is this block fully invalidated? 1533 */ 1534 if (offset <= curr_off) 1535 discard_buffer(bh); 1536 curr_off = next_off; 1537 bh = next; 1538 } while (bh != head); 1539 1540 /* 1541 * We release buffers only if the entire page is being invalidated. 1542 * The get_block cached value has been unconditionally invalidated, 1543 * so real IO is not possible anymore. 1544 */ 1545 if (offset == 0) 1546 try_to_release_page(page, 0); 1547 out: 1548 return; 1549 } 1550 EXPORT_SYMBOL(block_invalidatepage); 1551 1552 1553 /* 1554 * We attach and possibly dirty the buffers atomically wrt 1555 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers 1556 * is already excluded via the page lock. 1557 */ 1558 void create_empty_buffers(struct page *page, 1559 unsigned long blocksize, unsigned long b_state) 1560 { 1561 struct buffer_head *bh, *head, *tail; 1562 1563 head = alloc_page_buffers(page, blocksize, 1); 1564 bh = head; 1565 do { 1566 bh->b_state |= b_state; 1567 tail = bh; 1568 bh = bh->b_this_page; 1569 } while (bh); 1570 tail->b_this_page = head; 1571 1572 spin_lock(&page->mapping->private_lock); 1573 if (PageUptodate(page) || PageDirty(page)) { 1574 bh = head; 1575 do { 1576 if (PageDirty(page)) 1577 set_buffer_dirty(bh); 1578 if (PageUptodate(page)) 1579 set_buffer_uptodate(bh); 1580 bh = bh->b_this_page; 1581 } while (bh != head); 1582 } 1583 attach_page_buffers(page, head); 1584 spin_unlock(&page->mapping->private_lock); 1585 } 1586 EXPORT_SYMBOL(create_empty_buffers); 1587 1588 /* 1589 * We are taking a block for data and we don't want any output from any 1590 * buffer-cache aliases starting from return from that function and 1591 * until the moment when something will explicitly mark the buffer 1592 * dirty (hopefully that will not happen until we will free that block ;-) 1593 * We don't even need to mark it not-uptodate - nobody can expect 1594 * anything from a newly allocated buffer anyway. We used to used 1595 * unmap_buffer() for such invalidation, but that was wrong. We definitely 1596 * don't want to mark the alias unmapped, for example - it would confuse 1597 * anyone who might pick it with bread() afterwards... 1598 * 1599 * Also.. Note that bforget() doesn't lock the buffer. So there can 1600 * be writeout I/O going on against recently-freed buffers. We don't 1601 * wait on that I/O in bforget() - it's more efficient to wait on the I/O 1602 * only if we really need to. That happens here. 1603 */ 1604 void unmap_underlying_metadata(struct block_device *bdev, sector_t block) 1605 { 1606 struct buffer_head *old_bh; 1607 1608 might_sleep(); 1609 1610 old_bh = __find_get_block_slow(bdev, block); 1611 if (old_bh) { 1612 clear_buffer_dirty(old_bh); 1613 wait_on_buffer(old_bh); 1614 clear_buffer_req(old_bh); 1615 __brelse(old_bh); 1616 } 1617 } 1618 EXPORT_SYMBOL(unmap_underlying_metadata); 1619 1620 /* 1621 * Size is a power-of-two in the range 512..PAGE_SIZE, 1622 * and the case we care about most is PAGE_SIZE. 1623 * 1624 * So this *could* possibly be written with those 1625 * constraints in mind (relevant mostly if some 1626 * architecture has a slow bit-scan instruction) 1627 */ 1628 static inline int block_size_bits(unsigned int blocksize) 1629 { 1630 return ilog2(blocksize); 1631 } 1632 1633 static struct buffer_head *create_page_buffers(struct page *page, struct inode *inode, unsigned int b_state) 1634 { 1635 BUG_ON(!PageLocked(page)); 1636 1637 if (!page_has_buffers(page)) 1638 create_empty_buffers(page, 1 << ACCESS_ONCE(inode->i_blkbits), b_state); 1639 return page_buffers(page); 1640 } 1641 1642 /* 1643 * NOTE! All mapped/uptodate combinations are valid: 1644 * 1645 * Mapped Uptodate Meaning 1646 * 1647 * No No "unknown" - must do get_block() 1648 * No Yes "hole" - zero-filled 1649 * Yes No "allocated" - allocated on disk, not read in 1650 * Yes Yes "valid" - allocated and up-to-date in memory. 1651 * 1652 * "Dirty" is valid only with the last case (mapped+uptodate). 1653 */ 1654 1655 /* 1656 * While block_write_full_page is writing back the dirty buffers under 1657 * the page lock, whoever dirtied the buffers may decide to clean them 1658 * again at any time. We handle that by only looking at the buffer 1659 * state inside lock_buffer(). 1660 * 1661 * If block_write_full_page() is called for regular writeback 1662 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a 1663 * locked buffer. This only can happen if someone has written the buffer 1664 * directly, with submit_bh(). At the address_space level PageWriteback 1665 * prevents this contention from occurring. 1666 * 1667 * If block_write_full_page() is called with wbc->sync_mode == 1668 * WB_SYNC_ALL, the writes are posted using WRITE_SYNC; this 1669 * causes the writes to be flagged as synchronous writes. 1670 */ 1671 static int __block_write_full_page(struct inode *inode, struct page *page, 1672 get_block_t *get_block, struct writeback_control *wbc, 1673 bh_end_io_t *handler) 1674 { 1675 int err; 1676 sector_t block; 1677 sector_t last_block; 1678 struct buffer_head *bh, *head; 1679 unsigned int blocksize, bbits; 1680 int nr_underway = 0; 1681 int write_op = (wbc->sync_mode == WB_SYNC_ALL ? 1682 WRITE_SYNC : WRITE); 1683 1684 head = create_page_buffers(page, inode, 1685 (1 << BH_Dirty)|(1 << BH_Uptodate)); 1686 1687 /* 1688 * Be very careful. We have no exclusion from __set_page_dirty_buffers 1689 * here, and the (potentially unmapped) buffers may become dirty at 1690 * any time. If a buffer becomes dirty here after we've inspected it 1691 * then we just miss that fact, and the page stays dirty. 1692 * 1693 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers; 1694 * handle that here by just cleaning them. 1695 */ 1696 1697 bh = head; 1698 blocksize = bh->b_size; 1699 bbits = block_size_bits(blocksize); 1700 1701 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits); 1702 last_block = (i_size_read(inode) - 1) >> bbits; 1703 1704 /* 1705 * Get all the dirty buffers mapped to disk addresses and 1706 * handle any aliases from the underlying blockdev's mapping. 1707 */ 1708 do { 1709 if (block > last_block) { 1710 /* 1711 * mapped buffers outside i_size will occur, because 1712 * this page can be outside i_size when there is a 1713 * truncate in progress. 1714 */ 1715 /* 1716 * The buffer was zeroed by block_write_full_page() 1717 */ 1718 clear_buffer_dirty(bh); 1719 set_buffer_uptodate(bh); 1720 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) && 1721 buffer_dirty(bh)) { 1722 WARN_ON(bh->b_size != blocksize); 1723 err = get_block(inode, block, bh, 1); 1724 if (err) 1725 goto recover; 1726 clear_buffer_delay(bh); 1727 if (buffer_new(bh)) { 1728 /* blockdev mappings never come here */ 1729 clear_buffer_new(bh); 1730 unmap_underlying_metadata(bh->b_bdev, 1731 bh->b_blocknr); 1732 } 1733 } 1734 bh = bh->b_this_page; 1735 block++; 1736 } while (bh != head); 1737 1738 do { 1739 if (!buffer_mapped(bh)) 1740 continue; 1741 /* 1742 * If it's a fully non-blocking write attempt and we cannot 1743 * lock the buffer then redirty the page. Note that this can 1744 * potentially cause a busy-wait loop from writeback threads 1745 * and kswapd activity, but those code paths have their own 1746 * higher-level throttling. 1747 */ 1748 if (wbc->sync_mode != WB_SYNC_NONE) { 1749 lock_buffer(bh); 1750 } else if (!trylock_buffer(bh)) { 1751 redirty_page_for_writepage(wbc, page); 1752 continue; 1753 } 1754 if (test_clear_buffer_dirty(bh)) { 1755 mark_buffer_async_write_endio(bh, handler); 1756 } else { 1757 unlock_buffer(bh); 1758 } 1759 } while ((bh = bh->b_this_page) != head); 1760 1761 /* 1762 * The page and its buffers are protected by PageWriteback(), so we can 1763 * drop the bh refcounts early. 1764 */ 1765 BUG_ON(PageWriteback(page)); 1766 set_page_writeback(page); 1767 1768 do { 1769 struct buffer_head *next = bh->b_this_page; 1770 if (buffer_async_write(bh)) { 1771 submit_bh(write_op, bh); 1772 nr_underway++; 1773 } 1774 bh = next; 1775 } while (bh != head); 1776 unlock_page(page); 1777 1778 err = 0; 1779 done: 1780 if (nr_underway == 0) { 1781 /* 1782 * The page was marked dirty, but the buffers were 1783 * clean. Someone wrote them back by hand with 1784 * ll_rw_block/submit_bh. A rare case. 1785 */ 1786 end_page_writeback(page); 1787 1788 /* 1789 * The page and buffer_heads can be released at any time from 1790 * here on. 1791 */ 1792 } 1793 return err; 1794 1795 recover: 1796 /* 1797 * ENOSPC, or some other error. We may already have added some 1798 * blocks to the file, so we need to write these out to avoid 1799 * exposing stale data. 1800 * The page is currently locked and not marked for writeback 1801 */ 1802 bh = head; 1803 /* Recovery: lock and submit the mapped buffers */ 1804 do { 1805 if (buffer_mapped(bh) && buffer_dirty(bh) && 1806 !buffer_delay(bh)) { 1807 lock_buffer(bh); 1808 mark_buffer_async_write_endio(bh, handler); 1809 } else { 1810 /* 1811 * The buffer may have been set dirty during 1812 * attachment to a dirty page. 1813 */ 1814 clear_buffer_dirty(bh); 1815 } 1816 } while ((bh = bh->b_this_page) != head); 1817 SetPageError(page); 1818 BUG_ON(PageWriteback(page)); 1819 mapping_set_error(page->mapping, err); 1820 set_page_writeback(page); 1821 do { 1822 struct buffer_head *next = bh->b_this_page; 1823 if (buffer_async_write(bh)) { 1824 clear_buffer_dirty(bh); 1825 submit_bh(write_op, bh); 1826 nr_underway++; 1827 } 1828 bh = next; 1829 } while (bh != head); 1830 unlock_page(page); 1831 goto done; 1832 } 1833 1834 /* 1835 * If a page has any new buffers, zero them out here, and mark them uptodate 1836 * and dirty so they'll be written out (in order to prevent uninitialised 1837 * block data from leaking). And clear the new bit. 1838 */ 1839 void page_zero_new_buffers(struct page *page, unsigned from, unsigned to) 1840 { 1841 unsigned int block_start, block_end; 1842 struct buffer_head *head, *bh; 1843 1844 BUG_ON(!PageLocked(page)); 1845 if (!page_has_buffers(page)) 1846 return; 1847 1848 bh = head = page_buffers(page); 1849 block_start = 0; 1850 do { 1851 block_end = block_start + bh->b_size; 1852 1853 if (buffer_new(bh)) { 1854 if (block_end > from && block_start < to) { 1855 if (!PageUptodate(page)) { 1856 unsigned start, size; 1857 1858 start = max(from, block_start); 1859 size = min(to, block_end) - start; 1860 1861 zero_user(page, start, size); 1862 set_buffer_uptodate(bh); 1863 } 1864 1865 clear_buffer_new(bh); 1866 mark_buffer_dirty(bh); 1867 } 1868 } 1869 1870 block_start = block_end; 1871 bh = bh->b_this_page; 1872 } while (bh != head); 1873 } 1874 EXPORT_SYMBOL(page_zero_new_buffers); 1875 1876 int __block_write_begin(struct page *page, loff_t pos, unsigned len, 1877 get_block_t *get_block) 1878 { 1879 unsigned from = pos & (PAGE_CACHE_SIZE - 1); 1880 unsigned to = from + len; 1881 struct inode *inode = page->mapping->host; 1882 unsigned block_start, block_end; 1883 sector_t block; 1884 int err = 0; 1885 unsigned blocksize, bbits; 1886 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait; 1887 1888 BUG_ON(!PageLocked(page)); 1889 BUG_ON(from > PAGE_CACHE_SIZE); 1890 BUG_ON(to > PAGE_CACHE_SIZE); 1891 BUG_ON(from > to); 1892 1893 head = create_page_buffers(page, inode, 0); 1894 blocksize = head->b_size; 1895 bbits = block_size_bits(blocksize); 1896 1897 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits); 1898 1899 for(bh = head, block_start = 0; bh != head || !block_start; 1900 block++, block_start=block_end, bh = bh->b_this_page) { 1901 block_end = block_start + blocksize; 1902 if (block_end <= from || block_start >= to) { 1903 if (PageUptodate(page)) { 1904 if (!buffer_uptodate(bh)) 1905 set_buffer_uptodate(bh); 1906 } 1907 continue; 1908 } 1909 if (buffer_new(bh)) 1910 clear_buffer_new(bh); 1911 if (!buffer_mapped(bh)) { 1912 WARN_ON(bh->b_size != blocksize); 1913 err = get_block(inode, block, bh, 1); 1914 if (err) 1915 break; 1916 if (buffer_new(bh)) { 1917 unmap_underlying_metadata(bh->b_bdev, 1918 bh->b_blocknr); 1919 if (PageUptodate(page)) { 1920 clear_buffer_new(bh); 1921 set_buffer_uptodate(bh); 1922 mark_buffer_dirty(bh); 1923 continue; 1924 } 1925 if (block_end > to || block_start < from) 1926 zero_user_segments(page, 1927 to, block_end, 1928 block_start, from); 1929 continue; 1930 } 1931 } 1932 if (PageUptodate(page)) { 1933 if (!buffer_uptodate(bh)) 1934 set_buffer_uptodate(bh); 1935 continue; 1936 } 1937 if (!buffer_uptodate(bh) && !buffer_delay(bh) && 1938 !buffer_unwritten(bh) && 1939 (block_start < from || block_end > to)) { 1940 ll_rw_block(READ, 1, &bh); 1941 *wait_bh++=bh; 1942 } 1943 } 1944 /* 1945 * If we issued read requests - let them complete. 1946 */ 1947 while(wait_bh > wait) { 1948 wait_on_buffer(*--wait_bh); 1949 if (!buffer_uptodate(*wait_bh)) 1950 err = -EIO; 1951 } 1952 if (unlikely(err)) 1953 page_zero_new_buffers(page, from, to); 1954 return err; 1955 } 1956 EXPORT_SYMBOL(__block_write_begin); 1957 1958 static int __block_commit_write(struct inode *inode, struct page *page, 1959 unsigned from, unsigned to) 1960 { 1961 unsigned block_start, block_end; 1962 int partial = 0; 1963 unsigned blocksize; 1964 struct buffer_head *bh, *head; 1965 1966 bh = head = page_buffers(page); 1967 blocksize = bh->b_size; 1968 1969 block_start = 0; 1970 do { 1971 block_end = block_start + blocksize; 1972 if (block_end <= from || block_start >= to) { 1973 if (!buffer_uptodate(bh)) 1974 partial = 1; 1975 } else { 1976 set_buffer_uptodate(bh); 1977 mark_buffer_dirty(bh); 1978 } 1979 clear_buffer_new(bh); 1980 1981 block_start = block_end; 1982 bh = bh->b_this_page; 1983 } while (bh != head); 1984 1985 /* 1986 * If this is a partial write which happened to make all buffers 1987 * uptodate then we can optimize away a bogus readpage() for 1988 * the next read(). Here we 'discover' whether the page went 1989 * uptodate as a result of this (potentially partial) write. 1990 */ 1991 if (!partial) 1992 SetPageUptodate(page); 1993 return 0; 1994 } 1995 1996 /* 1997 * block_write_begin takes care of the basic task of block allocation and 1998 * bringing partial write blocks uptodate first. 1999 * 2000 * The filesystem needs to handle block truncation upon failure. 2001 */ 2002 int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len, 2003 unsigned flags, struct page **pagep, get_block_t *get_block) 2004 { 2005 pgoff_t index = pos >> PAGE_CACHE_SHIFT; 2006 struct page *page; 2007 int status; 2008 2009 page = grab_cache_page_write_begin(mapping, index, flags); 2010 if (!page) 2011 return -ENOMEM; 2012 2013 status = __block_write_begin(page, pos, len, get_block); 2014 if (unlikely(status)) { 2015 unlock_page(page); 2016 page_cache_release(page); 2017 page = NULL; 2018 } 2019 2020 *pagep = page; 2021 return status; 2022 } 2023 EXPORT_SYMBOL(block_write_begin); 2024 2025 int block_write_end(struct file *file, struct address_space *mapping, 2026 loff_t pos, unsigned len, unsigned copied, 2027 struct page *page, void *fsdata) 2028 { 2029 struct inode *inode = mapping->host; 2030 unsigned start; 2031 2032 start = pos & (PAGE_CACHE_SIZE - 1); 2033 2034 if (unlikely(copied < len)) { 2035 /* 2036 * The buffers that were written will now be uptodate, so we 2037 * don't have to worry about a readpage reading them and 2038 * overwriting a partial write. However if we have encountered 2039 * a short write and only partially written into a buffer, it 2040 * will not be marked uptodate, so a readpage might come in and 2041 * destroy our partial write. 2042 * 2043 * Do the simplest thing, and just treat any short write to a 2044 * non uptodate page as a zero-length write, and force the 2045 * caller to redo the whole thing. 2046 */ 2047 if (!PageUptodate(page)) 2048 copied = 0; 2049 2050 page_zero_new_buffers(page, start+copied, start+len); 2051 } 2052 flush_dcache_page(page); 2053 2054 /* This could be a short (even 0-length) commit */ 2055 __block_commit_write(inode, page, start, start+copied); 2056 2057 return copied; 2058 } 2059 EXPORT_SYMBOL(block_write_end); 2060 2061 int generic_write_end(struct file *file, struct address_space *mapping, 2062 loff_t pos, unsigned len, unsigned copied, 2063 struct page *page, void *fsdata) 2064 { 2065 struct inode *inode = mapping->host; 2066 int i_size_changed = 0; 2067 2068 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata); 2069 2070 /* 2071 * No need to use i_size_read() here, the i_size 2072 * cannot change under us because we hold i_mutex. 2073 * 2074 * But it's important to update i_size while still holding page lock: 2075 * page writeout could otherwise come in and zero beyond i_size. 2076 */ 2077 if (pos+copied > inode->i_size) { 2078 i_size_write(inode, pos+copied); 2079 i_size_changed = 1; 2080 } 2081 2082 unlock_page(page); 2083 page_cache_release(page); 2084 2085 /* 2086 * Don't mark the inode dirty under page lock. First, it unnecessarily 2087 * makes the holding time of page lock longer. Second, it forces lock 2088 * ordering of page lock and transaction start for journaling 2089 * filesystems. 2090 */ 2091 if (i_size_changed) 2092 mark_inode_dirty(inode); 2093 2094 return copied; 2095 } 2096 EXPORT_SYMBOL(generic_write_end); 2097 2098 /* 2099 * block_is_partially_uptodate checks whether buffers within a page are 2100 * uptodate or not. 2101 * 2102 * Returns true if all buffers which correspond to a file portion 2103 * we want to read are uptodate. 2104 */ 2105 int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc, 2106 unsigned long from) 2107 { 2108 unsigned block_start, block_end, blocksize; 2109 unsigned to; 2110 struct buffer_head *bh, *head; 2111 int ret = 1; 2112 2113 if (!page_has_buffers(page)) 2114 return 0; 2115 2116 head = page_buffers(page); 2117 blocksize = head->b_size; 2118 to = min_t(unsigned, PAGE_CACHE_SIZE - from, desc->count); 2119 to = from + to; 2120 if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize) 2121 return 0; 2122 2123 bh = head; 2124 block_start = 0; 2125 do { 2126 block_end = block_start + blocksize; 2127 if (block_end > from && block_start < to) { 2128 if (!buffer_uptodate(bh)) { 2129 ret = 0; 2130 break; 2131 } 2132 if (block_end >= to) 2133 break; 2134 } 2135 block_start = block_end; 2136 bh = bh->b_this_page; 2137 } while (bh != head); 2138 2139 return ret; 2140 } 2141 EXPORT_SYMBOL(block_is_partially_uptodate); 2142 2143 /* 2144 * Generic "read page" function for block devices that have the normal 2145 * get_block functionality. This is most of the block device filesystems. 2146 * Reads the page asynchronously --- the unlock_buffer() and 2147 * set/clear_buffer_uptodate() functions propagate buffer state into the 2148 * page struct once IO has completed. 2149 */ 2150 int block_read_full_page(struct page *page, get_block_t *get_block) 2151 { 2152 struct inode *inode = page->mapping->host; 2153 sector_t iblock, lblock; 2154 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE]; 2155 unsigned int blocksize, bbits; 2156 int nr, i; 2157 int fully_mapped = 1; 2158 2159 head = create_page_buffers(page, inode, 0); 2160 blocksize = head->b_size; 2161 bbits = block_size_bits(blocksize); 2162 2163 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits); 2164 lblock = (i_size_read(inode)+blocksize-1) >> bbits; 2165 bh = head; 2166 nr = 0; 2167 i = 0; 2168 2169 do { 2170 if (buffer_uptodate(bh)) 2171 continue; 2172 2173 if (!buffer_mapped(bh)) { 2174 int err = 0; 2175 2176 fully_mapped = 0; 2177 if (iblock < lblock) { 2178 WARN_ON(bh->b_size != blocksize); 2179 err = get_block(inode, iblock, bh, 0); 2180 if (err) 2181 SetPageError(page); 2182 } 2183 if (!buffer_mapped(bh)) { 2184 zero_user(page, i * blocksize, blocksize); 2185 if (!err) 2186 set_buffer_uptodate(bh); 2187 continue; 2188 } 2189 /* 2190 * get_block() might have updated the buffer 2191 * synchronously 2192 */ 2193 if (buffer_uptodate(bh)) 2194 continue; 2195 } 2196 arr[nr++] = bh; 2197 } while (i++, iblock++, (bh = bh->b_this_page) != head); 2198 2199 if (fully_mapped) 2200 SetPageMappedToDisk(page); 2201 2202 if (!nr) { 2203 /* 2204 * All buffers are uptodate - we can set the page uptodate 2205 * as well. But not if get_block() returned an error. 2206 */ 2207 if (!PageError(page)) 2208 SetPageUptodate(page); 2209 unlock_page(page); 2210 return 0; 2211 } 2212 2213 /* Stage two: lock the buffers */ 2214 for (i = 0; i < nr; i++) { 2215 bh = arr[i]; 2216 lock_buffer(bh); 2217 mark_buffer_async_read(bh); 2218 } 2219 2220 /* 2221 * Stage 3: start the IO. Check for uptodateness 2222 * inside the buffer lock in case another process reading 2223 * the underlying blockdev brought it uptodate (the sct fix). 2224 */ 2225 for (i = 0; i < nr; i++) { 2226 bh = arr[i]; 2227 if (buffer_uptodate(bh)) 2228 end_buffer_async_read(bh, 1); 2229 else 2230 submit_bh(READ, bh); 2231 } 2232 return 0; 2233 } 2234 EXPORT_SYMBOL(block_read_full_page); 2235 2236 /* utility function for filesystems that need to do work on expanding 2237 * truncates. Uses filesystem pagecache writes to allow the filesystem to 2238 * deal with the hole. 2239 */ 2240 int generic_cont_expand_simple(struct inode *inode, loff_t size) 2241 { 2242 struct address_space *mapping = inode->i_mapping; 2243 struct page *page; 2244 void *fsdata; 2245 int err; 2246 2247 err = inode_newsize_ok(inode, size); 2248 if (err) 2249 goto out; 2250 2251 err = pagecache_write_begin(NULL, mapping, size, 0, 2252 AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND, 2253 &page, &fsdata); 2254 if (err) 2255 goto out; 2256 2257 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata); 2258 BUG_ON(err > 0); 2259 2260 out: 2261 return err; 2262 } 2263 EXPORT_SYMBOL(generic_cont_expand_simple); 2264 2265 static int cont_expand_zero(struct file *file, struct address_space *mapping, 2266 loff_t pos, loff_t *bytes) 2267 { 2268 struct inode *inode = mapping->host; 2269 unsigned blocksize = 1 << inode->i_blkbits; 2270 struct page *page; 2271 void *fsdata; 2272 pgoff_t index, curidx; 2273 loff_t curpos; 2274 unsigned zerofrom, offset, len; 2275 int err = 0; 2276 2277 index = pos >> PAGE_CACHE_SHIFT; 2278 offset = pos & ~PAGE_CACHE_MASK; 2279 2280 while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) { 2281 zerofrom = curpos & ~PAGE_CACHE_MASK; 2282 if (zerofrom & (blocksize-1)) { 2283 *bytes |= (blocksize-1); 2284 (*bytes)++; 2285 } 2286 len = PAGE_CACHE_SIZE - zerofrom; 2287 2288 err = pagecache_write_begin(file, mapping, curpos, len, 2289 AOP_FLAG_UNINTERRUPTIBLE, 2290 &page, &fsdata); 2291 if (err) 2292 goto out; 2293 zero_user(page, zerofrom, len); 2294 err = pagecache_write_end(file, mapping, curpos, len, len, 2295 page, fsdata); 2296 if (err < 0) 2297 goto out; 2298 BUG_ON(err != len); 2299 err = 0; 2300 2301 balance_dirty_pages_ratelimited(mapping); 2302 } 2303 2304 /* page covers the boundary, find the boundary offset */ 2305 if (index == curidx) { 2306 zerofrom = curpos & ~PAGE_CACHE_MASK; 2307 /* if we will expand the thing last block will be filled */ 2308 if (offset <= zerofrom) { 2309 goto out; 2310 } 2311 if (zerofrom & (blocksize-1)) { 2312 *bytes |= (blocksize-1); 2313 (*bytes)++; 2314 } 2315 len = offset - zerofrom; 2316 2317 err = pagecache_write_begin(file, mapping, curpos, len, 2318 AOP_FLAG_UNINTERRUPTIBLE, 2319 &page, &fsdata); 2320 if (err) 2321 goto out; 2322 zero_user(page, zerofrom, len); 2323 err = pagecache_write_end(file, mapping, curpos, len, len, 2324 page, fsdata); 2325 if (err < 0) 2326 goto out; 2327 BUG_ON(err != len); 2328 err = 0; 2329 } 2330 out: 2331 return err; 2332 } 2333 2334 /* 2335 * For moronic filesystems that do not allow holes in file. 2336 * We may have to extend the file. 2337 */ 2338 int cont_write_begin(struct file *file, struct address_space *mapping, 2339 loff_t pos, unsigned len, unsigned flags, 2340 struct page **pagep, void **fsdata, 2341 get_block_t *get_block, loff_t *bytes) 2342 { 2343 struct inode *inode = mapping->host; 2344 unsigned blocksize = 1 << inode->i_blkbits; 2345 unsigned zerofrom; 2346 int err; 2347 2348 err = cont_expand_zero(file, mapping, pos, bytes); 2349 if (err) 2350 return err; 2351 2352 zerofrom = *bytes & ~PAGE_CACHE_MASK; 2353 if (pos+len > *bytes && zerofrom & (blocksize-1)) { 2354 *bytes |= (blocksize-1); 2355 (*bytes)++; 2356 } 2357 2358 return block_write_begin(mapping, pos, len, flags, pagep, get_block); 2359 } 2360 EXPORT_SYMBOL(cont_write_begin); 2361 2362 int block_commit_write(struct page *page, unsigned from, unsigned to) 2363 { 2364 struct inode *inode = page->mapping->host; 2365 __block_commit_write(inode,page,from,to); 2366 return 0; 2367 } 2368 EXPORT_SYMBOL(block_commit_write); 2369 2370 /* 2371 * block_page_mkwrite() is not allowed to change the file size as it gets 2372 * called from a page fault handler when a page is first dirtied. Hence we must 2373 * be careful to check for EOF conditions here. We set the page up correctly 2374 * for a written page which means we get ENOSPC checking when writing into 2375 * holes and correct delalloc and unwritten extent mapping on filesystems that 2376 * support these features. 2377 * 2378 * We are not allowed to take the i_mutex here so we have to play games to 2379 * protect against truncate races as the page could now be beyond EOF. Because 2380 * truncate writes the inode size before removing pages, once we have the 2381 * page lock we can determine safely if the page is beyond EOF. If it is not 2382 * beyond EOF, then the page is guaranteed safe against truncation until we 2383 * unlock the page. 2384 * 2385 * Direct callers of this function should protect against filesystem freezing 2386 * using sb_start_write() - sb_end_write() functions. 2387 */ 2388 int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, 2389 get_block_t get_block) 2390 { 2391 struct page *page = vmf->page; 2392 struct inode *inode = file_inode(vma->vm_file); 2393 unsigned long end; 2394 loff_t size; 2395 int ret; 2396 2397 lock_page(page); 2398 size = i_size_read(inode); 2399 if ((page->mapping != inode->i_mapping) || 2400 (page_offset(page) > size)) { 2401 /* We overload EFAULT to mean page got truncated */ 2402 ret = -EFAULT; 2403 goto out_unlock; 2404 } 2405 2406 /* page is wholly or partially inside EOF */ 2407 if (((page->index + 1) << PAGE_CACHE_SHIFT) > size) 2408 end = size & ~PAGE_CACHE_MASK; 2409 else 2410 end = PAGE_CACHE_SIZE; 2411 2412 ret = __block_write_begin(page, 0, end, get_block); 2413 if (!ret) 2414 ret = block_commit_write(page, 0, end); 2415 2416 if (unlikely(ret < 0)) 2417 goto out_unlock; 2418 set_page_dirty(page); 2419 wait_for_stable_page(page); 2420 return 0; 2421 out_unlock: 2422 unlock_page(page); 2423 return ret; 2424 } 2425 EXPORT_SYMBOL(__block_page_mkwrite); 2426 2427 int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, 2428 get_block_t get_block) 2429 { 2430 int ret; 2431 struct super_block *sb = file_inode(vma->vm_file)->i_sb; 2432 2433 sb_start_pagefault(sb); 2434 2435 /* 2436 * Update file times before taking page lock. We may end up failing the 2437 * fault so this update may be superfluous but who really cares... 2438 */ 2439 file_update_time(vma->vm_file); 2440 2441 ret = __block_page_mkwrite(vma, vmf, get_block); 2442 sb_end_pagefault(sb); 2443 return block_page_mkwrite_return(ret); 2444 } 2445 EXPORT_SYMBOL(block_page_mkwrite); 2446 2447 /* 2448 * nobh_write_begin()'s prereads are special: the buffer_heads are freed 2449 * immediately, while under the page lock. So it needs a special end_io 2450 * handler which does not touch the bh after unlocking it. 2451 */ 2452 static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate) 2453 { 2454 __end_buffer_read_notouch(bh, uptodate); 2455 } 2456 2457 /* 2458 * Attach the singly-linked list of buffers created by nobh_write_begin, to 2459 * the page (converting it to circular linked list and taking care of page 2460 * dirty races). 2461 */ 2462 static void attach_nobh_buffers(struct page *page, struct buffer_head *head) 2463 { 2464 struct buffer_head *bh; 2465 2466 BUG_ON(!PageLocked(page)); 2467 2468 spin_lock(&page->mapping->private_lock); 2469 bh = head; 2470 do { 2471 if (PageDirty(page)) 2472 set_buffer_dirty(bh); 2473 if (!bh->b_this_page) 2474 bh->b_this_page = head; 2475 bh = bh->b_this_page; 2476 } while (bh != head); 2477 attach_page_buffers(page, head); 2478 spin_unlock(&page->mapping->private_lock); 2479 } 2480 2481 /* 2482 * On entry, the page is fully not uptodate. 2483 * On exit the page is fully uptodate in the areas outside (from,to) 2484 * The filesystem needs to handle block truncation upon failure. 2485 */ 2486 int nobh_write_begin(struct address_space *mapping, 2487 loff_t pos, unsigned len, unsigned flags, 2488 struct page **pagep, void **fsdata, 2489 get_block_t *get_block) 2490 { 2491 struct inode *inode = mapping->host; 2492 const unsigned blkbits = inode->i_blkbits; 2493 const unsigned blocksize = 1 << blkbits; 2494 struct buffer_head *head, *bh; 2495 struct page *page; 2496 pgoff_t index; 2497 unsigned from, to; 2498 unsigned block_in_page; 2499 unsigned block_start, block_end; 2500 sector_t block_in_file; 2501 int nr_reads = 0; 2502 int ret = 0; 2503 int is_mapped_to_disk = 1; 2504 2505 index = pos >> PAGE_CACHE_SHIFT; 2506 from = pos & (PAGE_CACHE_SIZE - 1); 2507 to = from + len; 2508 2509 page = grab_cache_page_write_begin(mapping, index, flags); 2510 if (!page) 2511 return -ENOMEM; 2512 *pagep = page; 2513 *fsdata = NULL; 2514 2515 if (page_has_buffers(page)) { 2516 ret = __block_write_begin(page, pos, len, get_block); 2517 if (unlikely(ret)) 2518 goto out_release; 2519 return ret; 2520 } 2521 2522 if (PageMappedToDisk(page)) 2523 return 0; 2524 2525 /* 2526 * Allocate buffers so that we can keep track of state, and potentially 2527 * attach them to the page if an error occurs. In the common case of 2528 * no error, they will just be freed again without ever being attached 2529 * to the page (which is all OK, because we're under the page lock). 2530 * 2531 * Be careful: the buffer linked list is a NULL terminated one, rather 2532 * than the circular one we're used to. 2533 */ 2534 head = alloc_page_buffers(page, blocksize, 0); 2535 if (!head) { 2536 ret = -ENOMEM; 2537 goto out_release; 2538 } 2539 2540 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits); 2541 2542 /* 2543 * We loop across all blocks in the page, whether or not they are 2544 * part of the affected region. This is so we can discover if the 2545 * page is fully mapped-to-disk. 2546 */ 2547 for (block_start = 0, block_in_page = 0, bh = head; 2548 block_start < PAGE_CACHE_SIZE; 2549 block_in_page++, block_start += blocksize, bh = bh->b_this_page) { 2550 int create; 2551 2552 block_end = block_start + blocksize; 2553 bh->b_state = 0; 2554 create = 1; 2555 if (block_start >= to) 2556 create = 0; 2557 ret = get_block(inode, block_in_file + block_in_page, 2558 bh, create); 2559 if (ret) 2560 goto failed; 2561 if (!buffer_mapped(bh)) 2562 is_mapped_to_disk = 0; 2563 if (buffer_new(bh)) 2564 unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr); 2565 if (PageUptodate(page)) { 2566 set_buffer_uptodate(bh); 2567 continue; 2568 } 2569 if (buffer_new(bh) || !buffer_mapped(bh)) { 2570 zero_user_segments(page, block_start, from, 2571 to, block_end); 2572 continue; 2573 } 2574 if (buffer_uptodate(bh)) 2575 continue; /* reiserfs does this */ 2576 if (block_start < from || block_end > to) { 2577 lock_buffer(bh); 2578 bh->b_end_io = end_buffer_read_nobh; 2579 submit_bh(READ, bh); 2580 nr_reads++; 2581 } 2582 } 2583 2584 if (nr_reads) { 2585 /* 2586 * The page is locked, so these buffers are protected from 2587 * any VM or truncate activity. Hence we don't need to care 2588 * for the buffer_head refcounts. 2589 */ 2590 for (bh = head; bh; bh = bh->b_this_page) { 2591 wait_on_buffer(bh); 2592 if (!buffer_uptodate(bh)) 2593 ret = -EIO; 2594 } 2595 if (ret) 2596 goto failed; 2597 } 2598 2599 if (is_mapped_to_disk) 2600 SetPageMappedToDisk(page); 2601 2602 *fsdata = head; /* to be released by nobh_write_end */ 2603 2604 return 0; 2605 2606 failed: 2607 BUG_ON(!ret); 2608 /* 2609 * Error recovery is a bit difficult. We need to zero out blocks that 2610 * were newly allocated, and dirty them to ensure they get written out. 2611 * Buffers need to be attached to the page at this point, otherwise 2612 * the handling of potential IO errors during writeout would be hard 2613 * (could try doing synchronous writeout, but what if that fails too?) 2614 */ 2615 attach_nobh_buffers(page, head); 2616 page_zero_new_buffers(page, from, to); 2617 2618 out_release: 2619 unlock_page(page); 2620 page_cache_release(page); 2621 *pagep = NULL; 2622 2623 return ret; 2624 } 2625 EXPORT_SYMBOL(nobh_write_begin); 2626 2627 int nobh_write_end(struct file *file, struct address_space *mapping, 2628 loff_t pos, unsigned len, unsigned copied, 2629 struct page *page, void *fsdata) 2630 { 2631 struct inode *inode = page->mapping->host; 2632 struct buffer_head *head = fsdata; 2633 struct buffer_head *bh; 2634 BUG_ON(fsdata != NULL && page_has_buffers(page)); 2635 2636 if (unlikely(copied < len) && head) 2637 attach_nobh_buffers(page, head); 2638 if (page_has_buffers(page)) 2639 return generic_write_end(file, mapping, pos, len, 2640 copied, page, fsdata); 2641 2642 SetPageUptodate(page); 2643 set_page_dirty(page); 2644 if (pos+copied > inode->i_size) { 2645 i_size_write(inode, pos+copied); 2646 mark_inode_dirty(inode); 2647 } 2648 2649 unlock_page(page); 2650 page_cache_release(page); 2651 2652 while (head) { 2653 bh = head; 2654 head = head->b_this_page; 2655 free_buffer_head(bh); 2656 } 2657 2658 return copied; 2659 } 2660 EXPORT_SYMBOL(nobh_write_end); 2661 2662 /* 2663 * nobh_writepage() - based on block_full_write_page() except 2664 * that it tries to operate without attaching bufferheads to 2665 * the page. 2666 */ 2667 int nobh_writepage(struct page *page, get_block_t *get_block, 2668 struct writeback_control *wbc) 2669 { 2670 struct inode * const inode = page->mapping->host; 2671 loff_t i_size = i_size_read(inode); 2672 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT; 2673 unsigned offset; 2674 int ret; 2675 2676 /* Is the page fully inside i_size? */ 2677 if (page->index < end_index) 2678 goto out; 2679 2680 /* Is the page fully outside i_size? (truncate in progress) */ 2681 offset = i_size & (PAGE_CACHE_SIZE-1); 2682 if (page->index >= end_index+1 || !offset) { 2683 /* 2684 * The page may have dirty, unmapped buffers. For example, 2685 * they may have been added in ext3_writepage(). Make them 2686 * freeable here, so the page does not leak. 2687 */ 2688 #if 0 2689 /* Not really sure about this - do we need this ? */ 2690 if (page->mapping->a_ops->invalidatepage) 2691 page->mapping->a_ops->invalidatepage(page, offset); 2692 #endif 2693 unlock_page(page); 2694 return 0; /* don't care */ 2695 } 2696 2697 /* 2698 * The page straddles i_size. It must be zeroed out on each and every 2699 * writepage invocation because it may be mmapped. "A file is mapped 2700 * in multiples of the page size. For a file that is not a multiple of 2701 * the page size, the remaining memory is zeroed when mapped, and 2702 * writes to that region are not written out to the file." 2703 */ 2704 zero_user_segment(page, offset, PAGE_CACHE_SIZE); 2705 out: 2706 ret = mpage_writepage(page, get_block, wbc); 2707 if (ret == -EAGAIN) 2708 ret = __block_write_full_page(inode, page, get_block, wbc, 2709 end_buffer_async_write); 2710 return ret; 2711 } 2712 EXPORT_SYMBOL(nobh_writepage); 2713 2714 int nobh_truncate_page(struct address_space *mapping, 2715 loff_t from, get_block_t *get_block) 2716 { 2717 pgoff_t index = from >> PAGE_CACHE_SHIFT; 2718 unsigned offset = from & (PAGE_CACHE_SIZE-1); 2719 unsigned blocksize; 2720 sector_t iblock; 2721 unsigned length, pos; 2722 struct inode *inode = mapping->host; 2723 struct page *page; 2724 struct buffer_head map_bh; 2725 int err; 2726 2727 blocksize = 1 << inode->i_blkbits; 2728 length = offset & (blocksize - 1); 2729 2730 /* Block boundary? Nothing to do */ 2731 if (!length) 2732 return 0; 2733 2734 length = blocksize - length; 2735 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits); 2736 2737 page = grab_cache_page(mapping, index); 2738 err = -ENOMEM; 2739 if (!page) 2740 goto out; 2741 2742 if (page_has_buffers(page)) { 2743 has_buffers: 2744 unlock_page(page); 2745 page_cache_release(page); 2746 return block_truncate_page(mapping, from, get_block); 2747 } 2748 2749 /* Find the buffer that contains "offset" */ 2750 pos = blocksize; 2751 while (offset >= pos) { 2752 iblock++; 2753 pos += blocksize; 2754 } 2755 2756 map_bh.b_size = blocksize; 2757 map_bh.b_state = 0; 2758 err = get_block(inode, iblock, &map_bh, 0); 2759 if (err) 2760 goto unlock; 2761 /* unmapped? It's a hole - nothing to do */ 2762 if (!buffer_mapped(&map_bh)) 2763 goto unlock; 2764 2765 /* Ok, it's mapped. Make sure it's up-to-date */ 2766 if (!PageUptodate(page)) { 2767 err = mapping->a_ops->readpage(NULL, page); 2768 if (err) { 2769 page_cache_release(page); 2770 goto out; 2771 } 2772 lock_page(page); 2773 if (!PageUptodate(page)) { 2774 err = -EIO; 2775 goto unlock; 2776 } 2777 if (page_has_buffers(page)) 2778 goto has_buffers; 2779 } 2780 zero_user(page, offset, length); 2781 set_page_dirty(page); 2782 err = 0; 2783 2784 unlock: 2785 unlock_page(page); 2786 page_cache_release(page); 2787 out: 2788 return err; 2789 } 2790 EXPORT_SYMBOL(nobh_truncate_page); 2791 2792 int block_truncate_page(struct address_space *mapping, 2793 loff_t from, get_block_t *get_block) 2794 { 2795 pgoff_t index = from >> PAGE_CACHE_SHIFT; 2796 unsigned offset = from & (PAGE_CACHE_SIZE-1); 2797 unsigned blocksize; 2798 sector_t iblock; 2799 unsigned length, pos; 2800 struct inode *inode = mapping->host; 2801 struct page *page; 2802 struct buffer_head *bh; 2803 int err; 2804 2805 blocksize = 1 << inode->i_blkbits; 2806 length = offset & (blocksize - 1); 2807 2808 /* Block boundary? Nothing to do */ 2809 if (!length) 2810 return 0; 2811 2812 length = blocksize - length; 2813 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits); 2814 2815 page = grab_cache_page(mapping, index); 2816 err = -ENOMEM; 2817 if (!page) 2818 goto out; 2819 2820 if (!page_has_buffers(page)) 2821 create_empty_buffers(page, blocksize, 0); 2822 2823 /* Find the buffer that contains "offset" */ 2824 bh = page_buffers(page); 2825 pos = blocksize; 2826 while (offset >= pos) { 2827 bh = bh->b_this_page; 2828 iblock++; 2829 pos += blocksize; 2830 } 2831 2832 err = 0; 2833 if (!buffer_mapped(bh)) { 2834 WARN_ON(bh->b_size != blocksize); 2835 err = get_block(inode, iblock, bh, 0); 2836 if (err) 2837 goto unlock; 2838 /* unmapped? It's a hole - nothing to do */ 2839 if (!buffer_mapped(bh)) 2840 goto unlock; 2841 } 2842 2843 /* Ok, it's mapped. Make sure it's up-to-date */ 2844 if (PageUptodate(page)) 2845 set_buffer_uptodate(bh); 2846 2847 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) { 2848 err = -EIO; 2849 ll_rw_block(READ, 1, &bh); 2850 wait_on_buffer(bh); 2851 /* Uhhuh. Read error. Complain and punt. */ 2852 if (!buffer_uptodate(bh)) 2853 goto unlock; 2854 } 2855 2856 zero_user(page, offset, length); 2857 mark_buffer_dirty(bh); 2858 err = 0; 2859 2860 unlock: 2861 unlock_page(page); 2862 page_cache_release(page); 2863 out: 2864 return err; 2865 } 2866 EXPORT_SYMBOL(block_truncate_page); 2867 2868 /* 2869 * The generic ->writepage function for buffer-backed address_spaces 2870 * this form passes in the end_io handler used to finish the IO. 2871 */ 2872 int block_write_full_page_endio(struct page *page, get_block_t *get_block, 2873 struct writeback_control *wbc, bh_end_io_t *handler) 2874 { 2875 struct inode * const inode = page->mapping->host; 2876 loff_t i_size = i_size_read(inode); 2877 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT; 2878 unsigned offset; 2879 2880 /* Is the page fully inside i_size? */ 2881 if (page->index < end_index) 2882 return __block_write_full_page(inode, page, get_block, wbc, 2883 handler); 2884 2885 /* Is the page fully outside i_size? (truncate in progress) */ 2886 offset = i_size & (PAGE_CACHE_SIZE-1); 2887 if (page->index >= end_index+1 || !offset) { 2888 /* 2889 * The page may have dirty, unmapped buffers. For example, 2890 * they may have been added in ext3_writepage(). Make them 2891 * freeable here, so the page does not leak. 2892 */ 2893 do_invalidatepage(page, 0, PAGE_CACHE_SIZE); 2894 unlock_page(page); 2895 return 0; /* don't care */ 2896 } 2897 2898 /* 2899 * The page straddles i_size. It must be zeroed out on each and every 2900 * writepage invocation because it may be mmapped. "A file is mapped 2901 * in multiples of the page size. For a file that is not a multiple of 2902 * the page size, the remaining memory is zeroed when mapped, and 2903 * writes to that region are not written out to the file." 2904 */ 2905 zero_user_segment(page, offset, PAGE_CACHE_SIZE); 2906 return __block_write_full_page(inode, page, get_block, wbc, handler); 2907 } 2908 EXPORT_SYMBOL(block_write_full_page_endio); 2909 2910 /* 2911 * The generic ->writepage function for buffer-backed address_spaces 2912 */ 2913 int block_write_full_page(struct page *page, get_block_t *get_block, 2914 struct writeback_control *wbc) 2915 { 2916 return block_write_full_page_endio(page, get_block, wbc, 2917 end_buffer_async_write); 2918 } 2919 EXPORT_SYMBOL(block_write_full_page); 2920 2921 sector_t generic_block_bmap(struct address_space *mapping, sector_t block, 2922 get_block_t *get_block) 2923 { 2924 struct buffer_head tmp; 2925 struct inode *inode = mapping->host; 2926 tmp.b_state = 0; 2927 tmp.b_blocknr = 0; 2928 tmp.b_size = 1 << inode->i_blkbits; 2929 get_block(inode, block, &tmp, 0); 2930 return tmp.b_blocknr; 2931 } 2932 EXPORT_SYMBOL(generic_block_bmap); 2933 2934 static void end_bio_bh_io_sync(struct bio *bio, int err) 2935 { 2936 struct buffer_head *bh = bio->bi_private; 2937 2938 if (err == -EOPNOTSUPP) { 2939 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags); 2940 } 2941 2942 if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags))) 2943 set_bit(BH_Quiet, &bh->b_state); 2944 2945 bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags)); 2946 bio_put(bio); 2947 } 2948 2949 /* 2950 * This allows us to do IO even on the odd last sectors 2951 * of a device, even if the bh block size is some multiple 2952 * of the physical sector size. 2953 * 2954 * We'll just truncate the bio to the size of the device, 2955 * and clear the end of the buffer head manually. 2956 * 2957 * Truly out-of-range accesses will turn into actual IO 2958 * errors, this only handles the "we need to be able to 2959 * do IO at the final sector" case. 2960 */ 2961 static void guard_bh_eod(int rw, struct bio *bio, struct buffer_head *bh) 2962 { 2963 sector_t maxsector; 2964 unsigned bytes; 2965 2966 maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9; 2967 if (!maxsector) 2968 return; 2969 2970 /* 2971 * If the *whole* IO is past the end of the device, 2972 * let it through, and the IO layer will turn it into 2973 * an EIO. 2974 */ 2975 if (unlikely(bio->bi_sector >= maxsector)) 2976 return; 2977 2978 maxsector -= bio->bi_sector; 2979 bytes = bio->bi_size; 2980 if (likely((bytes >> 9) <= maxsector)) 2981 return; 2982 2983 /* Uhhuh. We've got a bh that straddles the device size! */ 2984 bytes = maxsector << 9; 2985 2986 /* Truncate the bio.. */ 2987 bio->bi_size = bytes; 2988 bio->bi_io_vec[0].bv_len = bytes; 2989 2990 /* ..and clear the end of the buffer for reads */ 2991 if ((rw & RW_MASK) == READ) { 2992 void *kaddr = kmap_atomic(bh->b_page); 2993 memset(kaddr + bh_offset(bh) + bytes, 0, bh->b_size - bytes); 2994 kunmap_atomic(kaddr); 2995 flush_dcache_page(bh->b_page); 2996 } 2997 } 2998 2999 int _submit_bh(int rw, struct buffer_head *bh, unsigned long bio_flags) 3000 { 3001 struct bio *bio; 3002 int ret = 0; 3003 3004 BUG_ON(!buffer_locked(bh)); 3005 BUG_ON(!buffer_mapped(bh)); 3006 BUG_ON(!bh->b_end_io); 3007 BUG_ON(buffer_delay(bh)); 3008 BUG_ON(buffer_unwritten(bh)); 3009 3010 /* 3011 * Only clear out a write error when rewriting 3012 */ 3013 if (test_set_buffer_req(bh) && (rw & WRITE)) 3014 clear_buffer_write_io_error(bh); 3015 3016 /* 3017 * from here on down, it's all bio -- do the initial mapping, 3018 * submit_bio -> generic_make_request may further map this bio around 3019 */ 3020 bio = bio_alloc(GFP_NOIO, 1); 3021 3022 bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9); 3023 bio->bi_bdev = bh->b_bdev; 3024 bio->bi_io_vec[0].bv_page = bh->b_page; 3025 bio->bi_io_vec[0].bv_len = bh->b_size; 3026 bio->bi_io_vec[0].bv_offset = bh_offset(bh); 3027 3028 bio->bi_vcnt = 1; 3029 bio->bi_size = bh->b_size; 3030 3031 bio->bi_end_io = end_bio_bh_io_sync; 3032 bio->bi_private = bh; 3033 bio->bi_flags |= bio_flags; 3034 3035 /* Take care of bh's that straddle the end of the device */ 3036 guard_bh_eod(rw, bio, bh); 3037 3038 if (buffer_meta(bh)) 3039 rw |= REQ_META; 3040 if (buffer_prio(bh)) 3041 rw |= REQ_PRIO; 3042 3043 bio_get(bio); 3044 submit_bio(rw, bio); 3045 3046 if (bio_flagged(bio, BIO_EOPNOTSUPP)) 3047 ret = -EOPNOTSUPP; 3048 3049 bio_put(bio); 3050 return ret; 3051 } 3052 EXPORT_SYMBOL_GPL(_submit_bh); 3053 3054 int submit_bh(int rw, struct buffer_head *bh) 3055 { 3056 return _submit_bh(rw, bh, 0); 3057 } 3058 EXPORT_SYMBOL(submit_bh); 3059 3060 /** 3061 * ll_rw_block: low-level access to block devices (DEPRECATED) 3062 * @rw: whether to %READ or %WRITE or maybe %READA (readahead) 3063 * @nr: number of &struct buffer_heads in the array 3064 * @bhs: array of pointers to &struct buffer_head 3065 * 3066 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and 3067 * requests an I/O operation on them, either a %READ or a %WRITE. The third 3068 * %READA option is described in the documentation for generic_make_request() 3069 * which ll_rw_block() calls. 3070 * 3071 * This function drops any buffer that it cannot get a lock on (with the 3072 * BH_Lock state bit), any buffer that appears to be clean when doing a write 3073 * request, and any buffer that appears to be up-to-date when doing read 3074 * request. Further it marks as clean buffers that are processed for 3075 * writing (the buffer cache won't assume that they are actually clean 3076 * until the buffer gets unlocked). 3077 * 3078 * ll_rw_block sets b_end_io to simple completion handler that marks 3079 * the buffer up-to-date (if approriate), unlocks the buffer and wakes 3080 * any waiters. 3081 * 3082 * All of the buffers must be for the same device, and must also be a 3083 * multiple of the current approved size for the device. 3084 */ 3085 void ll_rw_block(int rw, int nr, struct buffer_head *bhs[]) 3086 { 3087 int i; 3088 3089 for (i = 0; i < nr; i++) { 3090 struct buffer_head *bh = bhs[i]; 3091 3092 if (!trylock_buffer(bh)) 3093 continue; 3094 if (rw == WRITE) { 3095 if (test_clear_buffer_dirty(bh)) { 3096 bh->b_end_io = end_buffer_write_sync; 3097 get_bh(bh); 3098 submit_bh(WRITE, bh); 3099 continue; 3100 } 3101 } else { 3102 if (!buffer_uptodate(bh)) { 3103 bh->b_end_io = end_buffer_read_sync; 3104 get_bh(bh); 3105 submit_bh(rw, bh); 3106 continue; 3107 } 3108 } 3109 unlock_buffer(bh); 3110 } 3111 } 3112 EXPORT_SYMBOL(ll_rw_block); 3113 3114 void write_dirty_buffer(struct buffer_head *bh, int rw) 3115 { 3116 lock_buffer(bh); 3117 if (!test_clear_buffer_dirty(bh)) { 3118 unlock_buffer(bh); 3119 return; 3120 } 3121 bh->b_end_io = end_buffer_write_sync; 3122 get_bh(bh); 3123 submit_bh(rw, bh); 3124 } 3125 EXPORT_SYMBOL(write_dirty_buffer); 3126 3127 /* 3128 * For a data-integrity writeout, we need to wait upon any in-progress I/O 3129 * and then start new I/O and then wait upon it. The caller must have a ref on 3130 * the buffer_head. 3131 */ 3132 int __sync_dirty_buffer(struct buffer_head *bh, int rw) 3133 { 3134 int ret = 0; 3135 3136 WARN_ON(atomic_read(&bh->b_count) < 1); 3137 lock_buffer(bh); 3138 if (test_clear_buffer_dirty(bh)) { 3139 get_bh(bh); 3140 bh->b_end_io = end_buffer_write_sync; 3141 ret = submit_bh(rw, bh); 3142 wait_on_buffer(bh); 3143 if (!ret && !buffer_uptodate(bh)) 3144 ret = -EIO; 3145 } else { 3146 unlock_buffer(bh); 3147 } 3148 return ret; 3149 } 3150 EXPORT_SYMBOL(__sync_dirty_buffer); 3151 3152 int sync_dirty_buffer(struct buffer_head *bh) 3153 { 3154 return __sync_dirty_buffer(bh, WRITE_SYNC); 3155 } 3156 EXPORT_SYMBOL(sync_dirty_buffer); 3157 3158 /* 3159 * try_to_free_buffers() checks if all the buffers on this particular page 3160 * are unused, and releases them if so. 3161 * 3162 * Exclusion against try_to_free_buffers may be obtained by either 3163 * locking the page or by holding its mapping's private_lock. 3164 * 3165 * If the page is dirty but all the buffers are clean then we need to 3166 * be sure to mark the page clean as well. This is because the page 3167 * may be against a block device, and a later reattachment of buffers 3168 * to a dirty page will set *all* buffers dirty. Which would corrupt 3169 * filesystem data on the same device. 3170 * 3171 * The same applies to regular filesystem pages: if all the buffers are 3172 * clean then we set the page clean and proceed. To do that, we require 3173 * total exclusion from __set_page_dirty_buffers(). That is obtained with 3174 * private_lock. 3175 * 3176 * try_to_free_buffers() is non-blocking. 3177 */ 3178 static inline int buffer_busy(struct buffer_head *bh) 3179 { 3180 return atomic_read(&bh->b_count) | 3181 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock))); 3182 } 3183 3184 static int 3185 drop_buffers(struct page *page, struct buffer_head **buffers_to_free) 3186 { 3187 struct buffer_head *head = page_buffers(page); 3188 struct buffer_head *bh; 3189 3190 bh = head; 3191 do { 3192 if (buffer_write_io_error(bh) && page->mapping) 3193 set_bit(AS_EIO, &page->mapping->flags); 3194 if (buffer_busy(bh)) 3195 goto failed; 3196 bh = bh->b_this_page; 3197 } while (bh != head); 3198 3199 do { 3200 struct buffer_head *next = bh->b_this_page; 3201 3202 if (bh->b_assoc_map) 3203 __remove_assoc_queue(bh); 3204 bh = next; 3205 } while (bh != head); 3206 *buffers_to_free = head; 3207 __clear_page_buffers(page); 3208 return 1; 3209 failed: 3210 return 0; 3211 } 3212 3213 int try_to_free_buffers(struct page *page) 3214 { 3215 struct address_space * const mapping = page->mapping; 3216 struct buffer_head *buffers_to_free = NULL; 3217 int ret = 0; 3218 3219 BUG_ON(!PageLocked(page)); 3220 if (PageWriteback(page)) 3221 return 0; 3222 3223 if (mapping == NULL) { /* can this still happen? */ 3224 ret = drop_buffers(page, &buffers_to_free); 3225 goto out; 3226 } 3227 3228 spin_lock(&mapping->private_lock); 3229 ret = drop_buffers(page, &buffers_to_free); 3230 3231 /* 3232 * If the filesystem writes its buffers by hand (eg ext3) 3233 * then we can have clean buffers against a dirty page. We 3234 * clean the page here; otherwise the VM will never notice 3235 * that the filesystem did any IO at all. 3236 * 3237 * Also, during truncate, discard_buffer will have marked all 3238 * the page's buffers clean. We discover that here and clean 3239 * the page also. 3240 * 3241 * private_lock must be held over this entire operation in order 3242 * to synchronise against __set_page_dirty_buffers and prevent the 3243 * dirty bit from being lost. 3244 */ 3245 if (ret) 3246 cancel_dirty_page(page, PAGE_CACHE_SIZE); 3247 spin_unlock(&mapping->private_lock); 3248 out: 3249 if (buffers_to_free) { 3250 struct buffer_head *bh = buffers_to_free; 3251 3252 do { 3253 struct buffer_head *next = bh->b_this_page; 3254 free_buffer_head(bh); 3255 bh = next; 3256 } while (bh != buffers_to_free); 3257 } 3258 return ret; 3259 } 3260 EXPORT_SYMBOL(try_to_free_buffers); 3261 3262 /* 3263 * There are no bdflush tunables left. But distributions are 3264 * still running obsolete flush daemons, so we terminate them here. 3265 * 3266 * Use of bdflush() is deprecated and will be removed in a future kernel. 3267 * The `flush-X' kernel threads fully replace bdflush daemons and this call. 3268 */ 3269 SYSCALL_DEFINE2(bdflush, int, func, long, data) 3270 { 3271 static int msg_count; 3272 3273 if (!capable(CAP_SYS_ADMIN)) 3274 return -EPERM; 3275 3276 if (msg_count < 5) { 3277 msg_count++; 3278 printk(KERN_INFO 3279 "warning: process `%s' used the obsolete bdflush" 3280 " system call\n", current->comm); 3281 printk(KERN_INFO "Fix your initscripts?\n"); 3282 } 3283 3284 if (func == 1) 3285 do_exit(0); 3286 return 0; 3287 } 3288 3289 /* 3290 * Buffer-head allocation 3291 */ 3292 static struct kmem_cache *bh_cachep __read_mostly; 3293 3294 /* 3295 * Once the number of bh's in the machine exceeds this level, we start 3296 * stripping them in writeback. 3297 */ 3298 static unsigned long max_buffer_heads; 3299 3300 int buffer_heads_over_limit; 3301 3302 struct bh_accounting { 3303 int nr; /* Number of live bh's */ 3304 int ratelimit; /* Limit cacheline bouncing */ 3305 }; 3306 3307 static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0}; 3308 3309 static void recalc_bh_state(void) 3310 { 3311 int i; 3312 int tot = 0; 3313 3314 if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096) 3315 return; 3316 __this_cpu_write(bh_accounting.ratelimit, 0); 3317 for_each_online_cpu(i) 3318 tot += per_cpu(bh_accounting, i).nr; 3319 buffer_heads_over_limit = (tot > max_buffer_heads); 3320 } 3321 3322 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags) 3323 { 3324 struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags); 3325 if (ret) { 3326 INIT_LIST_HEAD(&ret->b_assoc_buffers); 3327 preempt_disable(); 3328 __this_cpu_inc(bh_accounting.nr); 3329 recalc_bh_state(); 3330 preempt_enable(); 3331 } 3332 return ret; 3333 } 3334 EXPORT_SYMBOL(alloc_buffer_head); 3335 3336 void free_buffer_head(struct buffer_head *bh) 3337 { 3338 BUG_ON(!list_empty(&bh->b_assoc_buffers)); 3339 kmem_cache_free(bh_cachep, bh); 3340 preempt_disable(); 3341 __this_cpu_dec(bh_accounting.nr); 3342 recalc_bh_state(); 3343 preempt_enable(); 3344 } 3345 EXPORT_SYMBOL(free_buffer_head); 3346 3347 static void buffer_exit_cpu(int cpu) 3348 { 3349 int i; 3350 struct bh_lru *b = &per_cpu(bh_lrus, cpu); 3351 3352 for (i = 0; i < BH_LRU_SIZE; i++) { 3353 brelse(b->bhs[i]); 3354 b->bhs[i] = NULL; 3355 } 3356 this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr); 3357 per_cpu(bh_accounting, cpu).nr = 0; 3358 } 3359 3360 static int buffer_cpu_notify(struct notifier_block *self, 3361 unsigned long action, void *hcpu) 3362 { 3363 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) 3364 buffer_exit_cpu((unsigned long)hcpu); 3365 return NOTIFY_OK; 3366 } 3367 3368 /** 3369 * bh_uptodate_or_lock - Test whether the buffer is uptodate 3370 * @bh: struct buffer_head 3371 * 3372 * Return true if the buffer is up-to-date and false, 3373 * with the buffer locked, if not. 3374 */ 3375 int bh_uptodate_or_lock(struct buffer_head *bh) 3376 { 3377 if (!buffer_uptodate(bh)) { 3378 lock_buffer(bh); 3379 if (!buffer_uptodate(bh)) 3380 return 0; 3381 unlock_buffer(bh); 3382 } 3383 return 1; 3384 } 3385 EXPORT_SYMBOL(bh_uptodate_or_lock); 3386 3387 /** 3388 * bh_submit_read - Submit a locked buffer for reading 3389 * @bh: struct buffer_head 3390 * 3391 * Returns zero on success and -EIO on error. 3392 */ 3393 int bh_submit_read(struct buffer_head *bh) 3394 { 3395 BUG_ON(!buffer_locked(bh)); 3396 3397 if (buffer_uptodate(bh)) { 3398 unlock_buffer(bh); 3399 return 0; 3400 } 3401 3402 get_bh(bh); 3403 bh->b_end_io = end_buffer_read_sync; 3404 submit_bh(READ, bh); 3405 wait_on_buffer(bh); 3406 if (buffer_uptodate(bh)) 3407 return 0; 3408 return -EIO; 3409 } 3410 EXPORT_SYMBOL(bh_submit_read); 3411 3412 void __init buffer_init(void) 3413 { 3414 unsigned long nrpages; 3415 3416 bh_cachep = kmem_cache_create("buffer_head", 3417 sizeof(struct buffer_head), 0, 3418 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC| 3419 SLAB_MEM_SPREAD), 3420 NULL); 3421 3422 /* 3423 * Limit the bh occupancy to 10% of ZONE_NORMAL 3424 */ 3425 nrpages = (nr_free_buffer_pages() * 10) / 100; 3426 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head)); 3427 hotcpu_notifier(buffer_cpu_notify, 0); 3428 } 3429