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/module.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 45 static int fsync_buffers_list(spinlock_t *lock, struct list_head *list); 46 47 #define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers) 48 49 inline void 50 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 static int sync_buffer(void *word) 58 { 59 struct block_device *bd; 60 struct buffer_head *bh 61 = container_of(word, struct buffer_head, b_state); 62 63 smp_mb(); 64 bd = bh->b_bdev; 65 if (bd) 66 blk_run_address_space(bd->bd_inode->i_mapping); 67 io_schedule(); 68 return 0; 69 } 70 71 void __lock_buffer(struct buffer_head *bh) 72 { 73 wait_on_bit_lock(&bh->b_state, BH_Lock, sync_buffer, 74 TASK_UNINTERRUPTIBLE); 75 } 76 EXPORT_SYMBOL(__lock_buffer); 77 78 void unlock_buffer(struct buffer_head *bh) 79 { 80 clear_bit_unlock(BH_Lock, &bh->b_state); 81 smp_mb__after_clear_bit(); 82 wake_up_bit(&bh->b_state, BH_Lock); 83 } 84 EXPORT_SYMBOL(unlock_buffer); 85 86 /* 87 * Block until a buffer comes unlocked. This doesn't stop it 88 * from becoming locked again - you have to lock it yourself 89 * if you want to preserve its state. 90 */ 91 void __wait_on_buffer(struct buffer_head * bh) 92 { 93 wait_on_bit(&bh->b_state, BH_Lock, sync_buffer, TASK_UNINTERRUPTIBLE); 94 } 95 EXPORT_SYMBOL(__wait_on_buffer); 96 97 static void 98 __clear_page_buffers(struct page *page) 99 { 100 ClearPagePrivate(page); 101 set_page_private(page, 0); 102 page_cache_release(page); 103 } 104 105 106 static int quiet_error(struct buffer_head *bh) 107 { 108 if (!test_bit(BH_Quiet, &bh->b_state) && printk_ratelimit()) 109 return 0; 110 return 1; 111 } 112 113 114 static void buffer_io_error(struct buffer_head *bh) 115 { 116 char b[BDEVNAME_SIZE]; 117 printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n", 118 bdevname(bh->b_bdev, b), 119 (unsigned long long)bh->b_blocknr); 120 } 121 122 /* 123 * End-of-IO handler helper function which does not touch the bh after 124 * unlocking it. 125 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but 126 * a race there is benign: unlock_buffer() only use the bh's address for 127 * hashing after unlocking the buffer, so it doesn't actually touch the bh 128 * itself. 129 */ 130 static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate) 131 { 132 if (uptodate) { 133 set_buffer_uptodate(bh); 134 } else { 135 /* This happens, due to failed READA attempts. */ 136 clear_buffer_uptodate(bh); 137 } 138 unlock_buffer(bh); 139 } 140 141 /* 142 * Default synchronous end-of-IO handler.. Just mark it up-to-date and 143 * unlock the buffer. This is what ll_rw_block uses too. 144 */ 145 void end_buffer_read_sync(struct buffer_head *bh, int uptodate) 146 { 147 __end_buffer_read_notouch(bh, uptodate); 148 put_bh(bh); 149 } 150 EXPORT_SYMBOL(end_buffer_read_sync); 151 152 void end_buffer_write_sync(struct buffer_head *bh, int uptodate) 153 { 154 char b[BDEVNAME_SIZE]; 155 156 if (uptodate) { 157 set_buffer_uptodate(bh); 158 } else { 159 if (!buffer_eopnotsupp(bh) && !quiet_error(bh)) { 160 buffer_io_error(bh); 161 printk(KERN_WARNING "lost page write due to " 162 "I/O error on %s\n", 163 bdevname(bh->b_bdev, b)); 164 } 165 set_buffer_write_io_error(bh); 166 clear_buffer_uptodate(bh); 167 } 168 unlock_buffer(bh); 169 put_bh(bh); 170 } 171 EXPORT_SYMBOL(end_buffer_write_sync); 172 173 /* 174 * Various filesystems appear to want __find_get_block to be non-blocking. 175 * But it's the page lock which protects the buffers. To get around this, 176 * we get exclusion from try_to_free_buffers with the blockdev mapping's 177 * private_lock. 178 * 179 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention 180 * may be quite high. This code could TryLock the page, and if that 181 * succeeds, there is no need to take private_lock. (But if 182 * private_lock is contended then so is mapping->tree_lock). 183 */ 184 static struct buffer_head * 185 __find_get_block_slow(struct block_device *bdev, sector_t block) 186 { 187 struct inode *bd_inode = bdev->bd_inode; 188 struct address_space *bd_mapping = bd_inode->i_mapping; 189 struct buffer_head *ret = NULL; 190 pgoff_t index; 191 struct buffer_head *bh; 192 struct buffer_head *head; 193 struct page *page; 194 int all_mapped = 1; 195 196 index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits); 197 page = find_get_page(bd_mapping, index); 198 if (!page) 199 goto out; 200 201 spin_lock(&bd_mapping->private_lock); 202 if (!page_has_buffers(page)) 203 goto out_unlock; 204 head = page_buffers(page); 205 bh = head; 206 do { 207 if (!buffer_mapped(bh)) 208 all_mapped = 0; 209 else if (bh->b_blocknr == block) { 210 ret = bh; 211 get_bh(bh); 212 goto out_unlock; 213 } 214 bh = bh->b_this_page; 215 } while (bh != head); 216 217 /* we might be here because some of the buffers on this page are 218 * not mapped. This is due to various races between 219 * file io on the block device and getblk. It gets dealt with 220 * elsewhere, don't buffer_error if we had some unmapped buffers 221 */ 222 if (all_mapped) { 223 printk("__find_get_block_slow() failed. " 224 "block=%llu, b_blocknr=%llu\n", 225 (unsigned long long)block, 226 (unsigned long long)bh->b_blocknr); 227 printk("b_state=0x%08lx, b_size=%zu\n", 228 bh->b_state, bh->b_size); 229 printk("device blocksize: %d\n", 1 << bd_inode->i_blkbits); 230 } 231 out_unlock: 232 spin_unlock(&bd_mapping->private_lock); 233 page_cache_release(page); 234 out: 235 return ret; 236 } 237 238 /* If invalidate_buffers() will trash dirty buffers, it means some kind 239 of fs corruption is going on. Trashing dirty data always imply losing 240 information that was supposed to be just stored on the physical layer 241 by the user. 242 243 Thus invalidate_buffers in general usage is not allwowed to trash 244 dirty buffers. For example ioctl(FLSBLKBUF) expects dirty data to 245 be preserved. These buffers are simply skipped. 246 247 We also skip buffers which are still in use. For example this can 248 happen if a userspace program is reading the block device. 249 250 NOTE: In the case where the user removed a removable-media-disk even if 251 there's still dirty data not synced on disk (due a bug in the device driver 252 or due an error of the user), by not destroying the dirty buffers we could 253 generate corruption also on the next media inserted, thus a parameter is 254 necessary to handle this case in the most safe way possible (trying 255 to not corrupt also the new disk inserted with the data belonging to 256 the old now corrupted disk). Also for the ramdisk the natural thing 257 to do in order to release the ramdisk memory is to destroy dirty buffers. 258 259 These are two special cases. Normal usage imply the device driver 260 to issue a sync on the device (without waiting I/O completion) and 261 then an invalidate_buffers call that doesn't trash dirty buffers. 262 263 For handling cache coherency with the blkdev pagecache the 'update' case 264 is been introduced. It is needed to re-read from disk any pinned 265 buffer. NOTE: re-reading from disk is destructive so we can do it only 266 when we assume nobody is changing the buffercache under our I/O and when 267 we think the disk contains more recent information than the buffercache. 268 The update == 1 pass marks the buffers we need to update, the update == 2 269 pass does the actual I/O. */ 270 void invalidate_bdev(struct block_device *bdev) 271 { 272 struct address_space *mapping = bdev->bd_inode->i_mapping; 273 274 if (mapping->nrpages == 0) 275 return; 276 277 invalidate_bh_lrus(); 278 lru_add_drain_all(); /* make sure all lru add caches are flushed */ 279 invalidate_mapping_pages(mapping, 0, -1); 280 } 281 EXPORT_SYMBOL(invalidate_bdev); 282 283 /* 284 * Kick the writeback threads then try to free up some ZONE_NORMAL memory. 285 */ 286 static void free_more_memory(void) 287 { 288 struct zone *zone; 289 int nid; 290 291 wakeup_flusher_threads(1024); 292 yield(); 293 294 for_each_online_node(nid) { 295 (void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS), 296 gfp_zone(GFP_NOFS), NULL, 297 &zone); 298 if (zone) 299 try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0, 300 GFP_NOFS, NULL); 301 } 302 } 303 304 /* 305 * I/O completion handler for block_read_full_page() - pages 306 * which come unlocked at the end of I/O. 307 */ 308 static void end_buffer_async_read(struct buffer_head *bh, int uptodate) 309 { 310 unsigned long flags; 311 struct buffer_head *first; 312 struct buffer_head *tmp; 313 struct page *page; 314 int page_uptodate = 1; 315 316 BUG_ON(!buffer_async_read(bh)); 317 318 page = bh->b_page; 319 if (uptodate) { 320 set_buffer_uptodate(bh); 321 } else { 322 clear_buffer_uptodate(bh); 323 if (!quiet_error(bh)) 324 buffer_io_error(bh); 325 SetPageError(page); 326 } 327 328 /* 329 * Be _very_ careful from here on. Bad things can happen if 330 * two buffer heads end IO at almost the same time and both 331 * decide that the page is now completely done. 332 */ 333 first = page_buffers(page); 334 local_irq_save(flags); 335 bit_spin_lock(BH_Uptodate_Lock, &first->b_state); 336 clear_buffer_async_read(bh); 337 unlock_buffer(bh); 338 tmp = bh; 339 do { 340 if (!buffer_uptodate(tmp)) 341 page_uptodate = 0; 342 if (buffer_async_read(tmp)) { 343 BUG_ON(!buffer_locked(tmp)); 344 goto still_busy; 345 } 346 tmp = tmp->b_this_page; 347 } while (tmp != bh); 348 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); 349 local_irq_restore(flags); 350 351 /* 352 * If none of the buffers had errors and they are all 353 * uptodate then we can set the page uptodate. 354 */ 355 if (page_uptodate && !PageError(page)) 356 SetPageUptodate(page); 357 unlock_page(page); 358 return; 359 360 still_busy: 361 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); 362 local_irq_restore(flags); 363 return; 364 } 365 366 /* 367 * Completion handler for block_write_full_page() - pages which are unlocked 368 * during I/O, and which have PageWriteback cleared upon I/O completion. 369 */ 370 void end_buffer_async_write(struct buffer_head *bh, int uptodate) 371 { 372 char b[BDEVNAME_SIZE]; 373 unsigned long flags; 374 struct buffer_head *first; 375 struct buffer_head *tmp; 376 struct page *page; 377 378 BUG_ON(!buffer_async_write(bh)); 379 380 page = bh->b_page; 381 if (uptodate) { 382 set_buffer_uptodate(bh); 383 } else { 384 if (!quiet_error(bh)) { 385 buffer_io_error(bh); 386 printk(KERN_WARNING "lost page write due to " 387 "I/O error on %s\n", 388 bdevname(bh->b_bdev, b)); 389 } 390 set_bit(AS_EIO, &page->mapping->flags); 391 set_buffer_write_io_error(bh); 392 clear_buffer_uptodate(bh); 393 SetPageError(page); 394 } 395 396 first = page_buffers(page); 397 local_irq_save(flags); 398 bit_spin_lock(BH_Uptodate_Lock, &first->b_state); 399 400 clear_buffer_async_write(bh); 401 unlock_buffer(bh); 402 tmp = bh->b_this_page; 403 while (tmp != bh) { 404 if (buffer_async_write(tmp)) { 405 BUG_ON(!buffer_locked(tmp)); 406 goto still_busy; 407 } 408 tmp = tmp->b_this_page; 409 } 410 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); 411 local_irq_restore(flags); 412 end_page_writeback(page); 413 return; 414 415 still_busy: 416 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); 417 local_irq_restore(flags); 418 return; 419 } 420 EXPORT_SYMBOL(end_buffer_async_write); 421 422 /* 423 * If a page's buffers are under async readin (end_buffer_async_read 424 * completion) then there is a possibility that another thread of 425 * control could lock one of the buffers after it has completed 426 * but while some of the other buffers have not completed. This 427 * locked buffer would confuse end_buffer_async_read() into not unlocking 428 * the page. So the absence of BH_Async_Read tells end_buffer_async_read() 429 * that this buffer is not under async I/O. 430 * 431 * The page comes unlocked when it has no locked buffer_async buffers 432 * left. 433 * 434 * PageLocked prevents anyone starting new async I/O reads any of 435 * the buffers. 436 * 437 * PageWriteback is used to prevent simultaneous writeout of the same 438 * page. 439 * 440 * PageLocked prevents anyone from starting writeback of a page which is 441 * under read I/O (PageWriteback is only ever set against a locked page). 442 */ 443 static void mark_buffer_async_read(struct buffer_head *bh) 444 { 445 bh->b_end_io = end_buffer_async_read; 446 set_buffer_async_read(bh); 447 } 448 449 static void mark_buffer_async_write_endio(struct buffer_head *bh, 450 bh_end_io_t *handler) 451 { 452 bh->b_end_io = handler; 453 set_buffer_async_write(bh); 454 } 455 456 void mark_buffer_async_write(struct buffer_head *bh) 457 { 458 mark_buffer_async_write_endio(bh, end_buffer_async_write); 459 } 460 EXPORT_SYMBOL(mark_buffer_async_write); 461 462 463 /* 464 * fs/buffer.c contains helper functions for buffer-backed address space's 465 * fsync functions. A common requirement for buffer-based filesystems is 466 * that certain data from the backing blockdev needs to be written out for 467 * a successful fsync(). For example, ext2 indirect blocks need to be 468 * written back and waited upon before fsync() returns. 469 * 470 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(), 471 * inode_has_buffers() and invalidate_inode_buffers() are provided for the 472 * management of a list of dependent buffers at ->i_mapping->private_list. 473 * 474 * Locking is a little subtle: try_to_free_buffers() will remove buffers 475 * from their controlling inode's queue when they are being freed. But 476 * try_to_free_buffers() will be operating against the *blockdev* mapping 477 * at the time, not against the S_ISREG file which depends on those buffers. 478 * So the locking for private_list is via the private_lock in the address_space 479 * which backs the buffers. Which is different from the address_space 480 * against which the buffers are listed. So for a particular address_space, 481 * mapping->private_lock does *not* protect mapping->private_list! In fact, 482 * mapping->private_list will always be protected by the backing blockdev's 483 * ->private_lock. 484 * 485 * Which introduces a requirement: all buffers on an address_space's 486 * ->private_list must be from the same address_space: the blockdev's. 487 * 488 * address_spaces which do not place buffers at ->private_list via these 489 * utility functions are free to use private_lock and private_list for 490 * whatever they want. The only requirement is that list_empty(private_list) 491 * be true at clear_inode() time. 492 * 493 * FIXME: clear_inode should not call invalidate_inode_buffers(). The 494 * filesystems should do that. invalidate_inode_buffers() should just go 495 * BUG_ON(!list_empty). 496 * 497 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should 498 * take an address_space, not an inode. And it should be called 499 * mark_buffer_dirty_fsync() to clearly define why those buffers are being 500 * queued up. 501 * 502 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the 503 * list if it is already on a list. Because if the buffer is on a list, 504 * it *must* already be on the right one. If not, the filesystem is being 505 * silly. This will save a ton of locking. But first we have to ensure 506 * that buffers are taken *off* the old inode's list when they are freed 507 * (presumably in truncate). That requires careful auditing of all 508 * filesystems (do it inside bforget()). It could also be done by bringing 509 * b_inode back. 510 */ 511 512 /* 513 * The buffer's backing address_space's private_lock must be held 514 */ 515 static void __remove_assoc_queue(struct buffer_head *bh) 516 { 517 list_del_init(&bh->b_assoc_buffers); 518 WARN_ON(!bh->b_assoc_map); 519 if (buffer_write_io_error(bh)) 520 set_bit(AS_EIO, &bh->b_assoc_map->flags); 521 bh->b_assoc_map = NULL; 522 } 523 524 int inode_has_buffers(struct inode *inode) 525 { 526 return !list_empty(&inode->i_data.private_list); 527 } 528 529 /* 530 * osync is designed to support O_SYNC io. It waits synchronously for 531 * all already-submitted IO to complete, but does not queue any new 532 * writes to the disk. 533 * 534 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as 535 * you dirty the buffers, and then use osync_inode_buffers to wait for 536 * completion. Any other dirty buffers which are not yet queued for 537 * write will not be flushed to disk by the osync. 538 */ 539 static int osync_buffers_list(spinlock_t *lock, struct list_head *list) 540 { 541 struct buffer_head *bh; 542 struct list_head *p; 543 int err = 0; 544 545 spin_lock(lock); 546 repeat: 547 list_for_each_prev(p, list) { 548 bh = BH_ENTRY(p); 549 if (buffer_locked(bh)) { 550 get_bh(bh); 551 spin_unlock(lock); 552 wait_on_buffer(bh); 553 if (!buffer_uptodate(bh)) 554 err = -EIO; 555 brelse(bh); 556 spin_lock(lock); 557 goto repeat; 558 } 559 } 560 spin_unlock(lock); 561 return err; 562 } 563 564 static void do_thaw_one(struct super_block *sb, void *unused) 565 { 566 char b[BDEVNAME_SIZE]; 567 while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb)) 568 printk(KERN_WARNING "Emergency Thaw on %s\n", 569 bdevname(sb->s_bdev, b)); 570 } 571 572 static void do_thaw_all(struct work_struct *work) 573 { 574 iterate_supers(do_thaw_one, NULL); 575 kfree(work); 576 printk(KERN_WARNING "Emergency Thaw complete\n"); 577 } 578 579 /** 580 * emergency_thaw_all -- forcibly thaw every frozen filesystem 581 * 582 * Used for emergency unfreeze of all filesystems via SysRq 583 */ 584 void emergency_thaw_all(void) 585 { 586 struct work_struct *work; 587 588 work = kmalloc(sizeof(*work), GFP_ATOMIC); 589 if (work) { 590 INIT_WORK(work, do_thaw_all); 591 schedule_work(work); 592 } 593 } 594 595 /** 596 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers 597 * @mapping: the mapping which wants those buffers written 598 * 599 * Starts I/O against the buffers at mapping->private_list, and waits upon 600 * that I/O. 601 * 602 * Basically, this is a convenience function for fsync(). 603 * @mapping is a file or directory which needs those buffers to be written for 604 * a successful fsync(). 605 */ 606 int sync_mapping_buffers(struct address_space *mapping) 607 { 608 struct address_space *buffer_mapping = mapping->assoc_mapping; 609 610 if (buffer_mapping == NULL || list_empty(&mapping->private_list)) 611 return 0; 612 613 return fsync_buffers_list(&buffer_mapping->private_lock, 614 &mapping->private_list); 615 } 616 EXPORT_SYMBOL(sync_mapping_buffers); 617 618 /* 619 * Called when we've recently written block `bblock', and it is known that 620 * `bblock' was for a buffer_boundary() buffer. This means that the block at 621 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's 622 * dirty, schedule it for IO. So that indirects merge nicely with their data. 623 */ 624 void write_boundary_block(struct block_device *bdev, 625 sector_t bblock, unsigned blocksize) 626 { 627 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize); 628 if (bh) { 629 if (buffer_dirty(bh)) 630 ll_rw_block(WRITE, 1, &bh); 631 put_bh(bh); 632 } 633 } 634 635 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode) 636 { 637 struct address_space *mapping = inode->i_mapping; 638 struct address_space *buffer_mapping = bh->b_page->mapping; 639 640 mark_buffer_dirty(bh); 641 if (!mapping->assoc_mapping) { 642 mapping->assoc_mapping = buffer_mapping; 643 } else { 644 BUG_ON(mapping->assoc_mapping != buffer_mapping); 645 } 646 if (!bh->b_assoc_map) { 647 spin_lock(&buffer_mapping->private_lock); 648 list_move_tail(&bh->b_assoc_buffers, 649 &mapping->private_list); 650 bh->b_assoc_map = mapping; 651 spin_unlock(&buffer_mapping->private_lock); 652 } 653 } 654 EXPORT_SYMBOL(mark_buffer_dirty_inode); 655 656 /* 657 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode 658 * dirty. 659 * 660 * If warn is true, then emit a warning if the page is not uptodate and has 661 * not been truncated. 662 */ 663 static void __set_page_dirty(struct page *page, 664 struct address_space *mapping, int warn) 665 { 666 spin_lock_irq(&mapping->tree_lock); 667 if (page->mapping) { /* Race with truncate? */ 668 WARN_ON_ONCE(warn && !PageUptodate(page)); 669 account_page_dirtied(page, mapping); 670 radix_tree_tag_set(&mapping->page_tree, 671 page_index(page), PAGECACHE_TAG_DIRTY); 672 } 673 spin_unlock_irq(&mapping->tree_lock); 674 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); 675 } 676 677 /* 678 * Add a page to the dirty page list. 679 * 680 * It is a sad fact of life that this function is called from several places 681 * deeply under spinlocking. It may not sleep. 682 * 683 * If the page has buffers, the uptodate buffers are set dirty, to preserve 684 * dirty-state coherency between the page and the buffers. It the page does 685 * not have buffers then when they are later attached they will all be set 686 * dirty. 687 * 688 * The buffers are dirtied before the page is dirtied. There's a small race 689 * window in which a writepage caller may see the page cleanness but not the 690 * buffer dirtiness. That's fine. If this code were to set the page dirty 691 * before the buffers, a concurrent writepage caller could clear the page dirty 692 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean 693 * page on the dirty page list. 694 * 695 * We use private_lock to lock against try_to_free_buffers while using the 696 * page's buffer list. Also use this to protect against clean buffers being 697 * added to the page after it was set dirty. 698 * 699 * FIXME: may need to call ->reservepage here as well. That's rather up to the 700 * address_space though. 701 */ 702 int __set_page_dirty_buffers(struct page *page) 703 { 704 int newly_dirty; 705 struct address_space *mapping = page_mapping(page); 706 707 if (unlikely(!mapping)) 708 return !TestSetPageDirty(page); 709 710 spin_lock(&mapping->private_lock); 711 if (page_has_buffers(page)) { 712 struct buffer_head *head = page_buffers(page); 713 struct buffer_head *bh = head; 714 715 do { 716 set_buffer_dirty(bh); 717 bh = bh->b_this_page; 718 } while (bh != head); 719 } 720 newly_dirty = !TestSetPageDirty(page); 721 spin_unlock(&mapping->private_lock); 722 723 if (newly_dirty) 724 __set_page_dirty(page, mapping, 1); 725 return newly_dirty; 726 } 727 EXPORT_SYMBOL(__set_page_dirty_buffers); 728 729 /* 730 * Write out and wait upon a list of buffers. 731 * 732 * We have conflicting pressures: we want to make sure that all 733 * initially dirty buffers get waited on, but that any subsequently 734 * dirtied buffers don't. After all, we don't want fsync to last 735 * forever if somebody is actively writing to the file. 736 * 737 * Do this in two main stages: first we copy dirty buffers to a 738 * temporary inode list, queueing the writes as we go. Then we clean 739 * up, waiting for those writes to complete. 740 * 741 * During this second stage, any subsequent updates to the file may end 742 * up refiling the buffer on the original inode's dirty list again, so 743 * there is a chance we will end up with a buffer queued for write but 744 * not yet completed on that list. So, as a final cleanup we go through 745 * the osync code to catch these locked, dirty buffers without requeuing 746 * any newly dirty buffers for write. 747 */ 748 static int fsync_buffers_list(spinlock_t *lock, struct list_head *list) 749 { 750 struct buffer_head *bh; 751 struct list_head tmp; 752 struct address_space *mapping, *prev_mapping = NULL; 753 int err = 0, err2; 754 755 INIT_LIST_HEAD(&tmp); 756 757 spin_lock(lock); 758 while (!list_empty(list)) { 759 bh = BH_ENTRY(list->next); 760 mapping = bh->b_assoc_map; 761 __remove_assoc_queue(bh); 762 /* Avoid race with mark_buffer_dirty_inode() which does 763 * a lockless check and we rely on seeing the dirty bit */ 764 smp_mb(); 765 if (buffer_dirty(bh) || buffer_locked(bh)) { 766 list_add(&bh->b_assoc_buffers, &tmp); 767 bh->b_assoc_map = mapping; 768 if (buffer_dirty(bh)) { 769 get_bh(bh); 770 spin_unlock(lock); 771 /* 772 * Ensure any pending I/O completes so that 773 * ll_rw_block() actually writes the current 774 * contents - it is a noop if I/O is still in 775 * flight on potentially older contents. 776 */ 777 ll_rw_block(SWRITE_SYNC_PLUG, 1, &bh); 778 779 /* 780 * Kick off IO for the previous mapping. Note 781 * that we will not run the very last mapping, 782 * wait_on_buffer() will do that for us 783 * through sync_buffer(). 784 */ 785 if (prev_mapping && prev_mapping != mapping) 786 blk_run_address_space(prev_mapping); 787 prev_mapping = mapping; 788 789 brelse(bh); 790 spin_lock(lock); 791 } 792 } 793 } 794 795 while (!list_empty(&tmp)) { 796 bh = BH_ENTRY(tmp.prev); 797 get_bh(bh); 798 mapping = bh->b_assoc_map; 799 __remove_assoc_queue(bh); 800 /* Avoid race with mark_buffer_dirty_inode() which does 801 * a lockless check and we rely on seeing the dirty bit */ 802 smp_mb(); 803 if (buffer_dirty(bh)) { 804 list_add(&bh->b_assoc_buffers, 805 &mapping->private_list); 806 bh->b_assoc_map = mapping; 807 } 808 spin_unlock(lock); 809 wait_on_buffer(bh); 810 if (!buffer_uptodate(bh)) 811 err = -EIO; 812 brelse(bh); 813 spin_lock(lock); 814 } 815 816 spin_unlock(lock); 817 err2 = osync_buffers_list(lock, list); 818 if (err) 819 return err; 820 else 821 return err2; 822 } 823 824 /* 825 * Invalidate any and all dirty buffers on a given inode. We are 826 * probably unmounting the fs, but that doesn't mean we have already 827 * done a sync(). Just drop the buffers from the inode list. 828 * 829 * NOTE: we take the inode's blockdev's mapping's private_lock. Which 830 * assumes that all the buffers are against the blockdev. Not true 831 * for reiserfs. 832 */ 833 void invalidate_inode_buffers(struct inode *inode) 834 { 835 if (inode_has_buffers(inode)) { 836 struct address_space *mapping = &inode->i_data; 837 struct list_head *list = &mapping->private_list; 838 struct address_space *buffer_mapping = mapping->assoc_mapping; 839 840 spin_lock(&buffer_mapping->private_lock); 841 while (!list_empty(list)) 842 __remove_assoc_queue(BH_ENTRY(list->next)); 843 spin_unlock(&buffer_mapping->private_lock); 844 } 845 } 846 EXPORT_SYMBOL(invalidate_inode_buffers); 847 848 /* 849 * Remove any clean buffers from the inode's buffer list. This is called 850 * when we're trying to free the inode itself. Those buffers can pin it. 851 * 852 * Returns true if all buffers were removed. 853 */ 854 int remove_inode_buffers(struct inode *inode) 855 { 856 int ret = 1; 857 858 if (inode_has_buffers(inode)) { 859 struct address_space *mapping = &inode->i_data; 860 struct list_head *list = &mapping->private_list; 861 struct address_space *buffer_mapping = mapping->assoc_mapping; 862 863 spin_lock(&buffer_mapping->private_lock); 864 while (!list_empty(list)) { 865 struct buffer_head *bh = BH_ENTRY(list->next); 866 if (buffer_dirty(bh)) { 867 ret = 0; 868 break; 869 } 870 __remove_assoc_queue(bh); 871 } 872 spin_unlock(&buffer_mapping->private_lock); 873 } 874 return ret; 875 } 876 877 /* 878 * Create the appropriate buffers when given a page for data area and 879 * the size of each buffer.. Use the bh->b_this_page linked list to 880 * follow the buffers created. Return NULL if unable to create more 881 * buffers. 882 * 883 * The retry flag is used to differentiate async IO (paging, swapping) 884 * which may not fail from ordinary buffer allocations. 885 */ 886 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, 887 int retry) 888 { 889 struct buffer_head *bh, *head; 890 long offset; 891 892 try_again: 893 head = NULL; 894 offset = PAGE_SIZE; 895 while ((offset -= size) >= 0) { 896 bh = alloc_buffer_head(GFP_NOFS); 897 if (!bh) 898 goto no_grow; 899 900 bh->b_bdev = NULL; 901 bh->b_this_page = head; 902 bh->b_blocknr = -1; 903 head = bh; 904 905 bh->b_state = 0; 906 atomic_set(&bh->b_count, 0); 907 bh->b_private = NULL; 908 bh->b_size = size; 909 910 /* Link the buffer to its page */ 911 set_bh_page(bh, page, offset); 912 913 init_buffer(bh, NULL, NULL); 914 } 915 return head; 916 /* 917 * In case anything failed, we just free everything we got. 918 */ 919 no_grow: 920 if (head) { 921 do { 922 bh = head; 923 head = head->b_this_page; 924 free_buffer_head(bh); 925 } while (head); 926 } 927 928 /* 929 * Return failure for non-async IO requests. Async IO requests 930 * are not allowed to fail, so we have to wait until buffer heads 931 * become available. But we don't want tasks sleeping with 932 * partially complete buffers, so all were released above. 933 */ 934 if (!retry) 935 return NULL; 936 937 /* We're _really_ low on memory. Now we just 938 * wait for old buffer heads to become free due to 939 * finishing IO. Since this is an async request and 940 * the reserve list is empty, we're sure there are 941 * async buffer heads in use. 942 */ 943 free_more_memory(); 944 goto try_again; 945 } 946 EXPORT_SYMBOL_GPL(alloc_page_buffers); 947 948 static inline void 949 link_dev_buffers(struct page *page, struct buffer_head *head) 950 { 951 struct buffer_head *bh, *tail; 952 953 bh = head; 954 do { 955 tail = bh; 956 bh = bh->b_this_page; 957 } while (bh); 958 tail->b_this_page = head; 959 attach_page_buffers(page, head); 960 } 961 962 /* 963 * Initialise the state of a blockdev page's buffers. 964 */ 965 static void 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); 972 973 do { 974 if (!buffer_mapped(bh)) { 975 init_buffer(bh, NULL, NULL); 976 bh->b_bdev = bdev; 977 bh->b_blocknr = block; 978 if (uptodate) 979 set_buffer_uptodate(bh); 980 set_buffer_mapped(bh); 981 } 982 block++; 983 bh = bh->b_this_page; 984 } while (bh != head); 985 } 986 987 /* 988 * Create the page-cache page that contains the requested block. 989 * 990 * This is user purely for blockdev mappings. 991 */ 992 static struct page * 993 grow_dev_page(struct block_device *bdev, sector_t block, 994 pgoff_t index, int size) 995 { 996 struct inode *inode = bdev->bd_inode; 997 struct page *page; 998 struct buffer_head *bh; 999 1000 page = find_or_create_page(inode->i_mapping, index, 1001 (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE); 1002 if (!page) 1003 return NULL; 1004 1005 BUG_ON(!PageLocked(page)); 1006 1007 if (page_has_buffers(page)) { 1008 bh = page_buffers(page); 1009 if (bh->b_size == size) { 1010 init_page_buffers(page, bdev, block, size); 1011 return page; 1012 } 1013 if (!try_to_free_buffers(page)) 1014 goto failed; 1015 } 1016 1017 /* 1018 * Allocate some buffers for this page 1019 */ 1020 bh = alloc_page_buffers(page, size, 0); 1021 if (!bh) 1022 goto failed; 1023 1024 /* 1025 * Link the page to the buffers and initialise them. Take the 1026 * lock to be atomic wrt __find_get_block(), which does not 1027 * run under the page lock. 1028 */ 1029 spin_lock(&inode->i_mapping->private_lock); 1030 link_dev_buffers(page, bh); 1031 init_page_buffers(page, bdev, block, size); 1032 spin_unlock(&inode->i_mapping->private_lock); 1033 return page; 1034 1035 failed: 1036 BUG(); 1037 unlock_page(page); 1038 page_cache_release(page); 1039 return NULL; 1040 } 1041 1042 /* 1043 * Create buffers for the specified block device block's page. If 1044 * that page was dirty, the buffers are set dirty also. 1045 */ 1046 static int 1047 grow_buffers(struct block_device *bdev, sector_t block, int size) 1048 { 1049 struct page *page; 1050 pgoff_t index; 1051 int sizebits; 1052 1053 sizebits = -1; 1054 do { 1055 sizebits++; 1056 } while ((size << sizebits) < PAGE_SIZE); 1057 1058 index = block >> sizebits; 1059 1060 /* 1061 * Check for a block which wants to lie outside our maximum possible 1062 * pagecache index. (this comparison is done using sector_t types). 1063 */ 1064 if (unlikely(index != block >> sizebits)) { 1065 char b[BDEVNAME_SIZE]; 1066 1067 printk(KERN_ERR "%s: requested out-of-range block %llu for " 1068 "device %s\n", 1069 __func__, (unsigned long long)block, 1070 bdevname(bdev, b)); 1071 return -EIO; 1072 } 1073 block = index << sizebits; 1074 /* Create a page with the proper size buffers.. */ 1075 page = grow_dev_page(bdev, block, index, size); 1076 if (!page) 1077 return 0; 1078 unlock_page(page); 1079 page_cache_release(page); 1080 return 1; 1081 } 1082 1083 static struct buffer_head * 1084 __getblk_slow(struct block_device *bdev, sector_t block, int size) 1085 { 1086 /* Size must be multiple of hard sectorsize */ 1087 if (unlikely(size & (bdev_logical_block_size(bdev)-1) || 1088 (size < 512 || size > PAGE_SIZE))) { 1089 printk(KERN_ERR "getblk(): invalid block size %d requested\n", 1090 size); 1091 printk(KERN_ERR "logical block size: %d\n", 1092 bdev_logical_block_size(bdev)); 1093 1094 dump_stack(); 1095 return NULL; 1096 } 1097 1098 for (;;) { 1099 struct buffer_head * bh; 1100 int ret; 1101 1102 bh = __find_get_block(bdev, block, size); 1103 if (bh) 1104 return bh; 1105 1106 ret = grow_buffers(bdev, block, size); 1107 if (ret < 0) 1108 return NULL; 1109 if (ret == 0) 1110 free_more_memory(); 1111 } 1112 } 1113 1114 /* 1115 * The relationship between dirty buffers and dirty pages: 1116 * 1117 * Whenever a page has any dirty buffers, the page's dirty bit is set, and 1118 * the page is tagged dirty in its radix tree. 1119 * 1120 * At all times, the dirtiness of the buffers represents the dirtiness of 1121 * subsections of the page. If the page has buffers, the page dirty bit is 1122 * merely a hint about the true dirty state. 1123 * 1124 * When a page is set dirty in its entirety, all its buffers are marked dirty 1125 * (if the page has buffers). 1126 * 1127 * When a buffer is marked dirty, its page is dirtied, but the page's other 1128 * buffers are not. 1129 * 1130 * Also. When blockdev buffers are explicitly read with bread(), they 1131 * individually become uptodate. But their backing page remains not 1132 * uptodate - even if all of its buffers are uptodate. A subsequent 1133 * block_read_full_page() against that page will discover all the uptodate 1134 * buffers, will set the page uptodate and will perform no I/O. 1135 */ 1136 1137 /** 1138 * mark_buffer_dirty - mark a buffer_head as needing writeout 1139 * @bh: the buffer_head to mark dirty 1140 * 1141 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its 1142 * backing page dirty, then tag the page as dirty in its address_space's radix 1143 * tree and then attach the address_space's inode to its superblock's dirty 1144 * inode list. 1145 * 1146 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock, 1147 * mapping->tree_lock and the global inode_lock. 1148 */ 1149 void mark_buffer_dirty(struct buffer_head *bh) 1150 { 1151 WARN_ON_ONCE(!buffer_uptodate(bh)); 1152 1153 /* 1154 * Very *carefully* optimize the it-is-already-dirty case. 1155 * 1156 * Don't let the final "is it dirty" escape to before we 1157 * perhaps modified the buffer. 1158 */ 1159 if (buffer_dirty(bh)) { 1160 smp_mb(); 1161 if (buffer_dirty(bh)) 1162 return; 1163 } 1164 1165 if (!test_set_buffer_dirty(bh)) { 1166 struct page *page = bh->b_page; 1167 if (!TestSetPageDirty(page)) { 1168 struct address_space *mapping = page_mapping(page); 1169 if (mapping) 1170 __set_page_dirty(page, mapping, 0); 1171 } 1172 } 1173 } 1174 EXPORT_SYMBOL(mark_buffer_dirty); 1175 1176 /* 1177 * Decrement a buffer_head's reference count. If all buffers against a page 1178 * have zero reference count, are clean and unlocked, and if the page is clean 1179 * and unlocked then try_to_free_buffers() may strip the buffers from the page 1180 * in preparation for freeing it (sometimes, rarely, buffers are removed from 1181 * a page but it ends up not being freed, and buffers may later be reattached). 1182 */ 1183 void __brelse(struct buffer_head * buf) 1184 { 1185 if (atomic_read(&buf->b_count)) { 1186 put_bh(buf); 1187 return; 1188 } 1189 WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n"); 1190 } 1191 EXPORT_SYMBOL(__brelse); 1192 1193 /* 1194 * bforget() is like brelse(), except it discards any 1195 * potentially dirty data. 1196 */ 1197 void __bforget(struct buffer_head *bh) 1198 { 1199 clear_buffer_dirty(bh); 1200 if (bh->b_assoc_map) { 1201 struct address_space *buffer_mapping = bh->b_page->mapping; 1202 1203 spin_lock(&buffer_mapping->private_lock); 1204 list_del_init(&bh->b_assoc_buffers); 1205 bh->b_assoc_map = NULL; 1206 spin_unlock(&buffer_mapping->private_lock); 1207 } 1208 __brelse(bh); 1209 } 1210 EXPORT_SYMBOL(__bforget); 1211 1212 static struct buffer_head *__bread_slow(struct buffer_head *bh) 1213 { 1214 lock_buffer(bh); 1215 if (buffer_uptodate(bh)) { 1216 unlock_buffer(bh); 1217 return bh; 1218 } else { 1219 get_bh(bh); 1220 bh->b_end_io = end_buffer_read_sync; 1221 submit_bh(READ, bh); 1222 wait_on_buffer(bh); 1223 if (buffer_uptodate(bh)) 1224 return bh; 1225 } 1226 brelse(bh); 1227 return NULL; 1228 } 1229 1230 /* 1231 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block(). 1232 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their 1233 * refcount elevated by one when they're in an LRU. A buffer can only appear 1234 * once in a particular CPU's LRU. A single buffer can be present in multiple 1235 * CPU's LRUs at the same time. 1236 * 1237 * This is a transparent caching front-end to sb_bread(), sb_getblk() and 1238 * sb_find_get_block(). 1239 * 1240 * The LRUs themselves only need locking against invalidate_bh_lrus. We use 1241 * a local interrupt disable for that. 1242 */ 1243 1244 #define BH_LRU_SIZE 8 1245 1246 struct bh_lru { 1247 struct buffer_head *bhs[BH_LRU_SIZE]; 1248 }; 1249 1250 static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }}; 1251 1252 #ifdef CONFIG_SMP 1253 #define bh_lru_lock() local_irq_disable() 1254 #define bh_lru_unlock() local_irq_enable() 1255 #else 1256 #define bh_lru_lock() preempt_disable() 1257 #define bh_lru_unlock() preempt_enable() 1258 #endif 1259 1260 static inline void check_irqs_on(void) 1261 { 1262 #ifdef irqs_disabled 1263 BUG_ON(irqs_disabled()); 1264 #endif 1265 } 1266 1267 /* 1268 * The LRU management algorithm is dopey-but-simple. Sorry. 1269 */ 1270 static void bh_lru_install(struct buffer_head *bh) 1271 { 1272 struct buffer_head *evictee = NULL; 1273 struct bh_lru *lru; 1274 1275 check_irqs_on(); 1276 bh_lru_lock(); 1277 lru = &__get_cpu_var(bh_lrus); 1278 if (lru->bhs[0] != bh) { 1279 struct buffer_head *bhs[BH_LRU_SIZE]; 1280 int in; 1281 int out = 0; 1282 1283 get_bh(bh); 1284 bhs[out++] = bh; 1285 for (in = 0; in < BH_LRU_SIZE; in++) { 1286 struct buffer_head *bh2 = lru->bhs[in]; 1287 1288 if (bh2 == bh) { 1289 __brelse(bh2); 1290 } else { 1291 if (out >= BH_LRU_SIZE) { 1292 BUG_ON(evictee != NULL); 1293 evictee = bh2; 1294 } else { 1295 bhs[out++] = bh2; 1296 } 1297 } 1298 } 1299 while (out < BH_LRU_SIZE) 1300 bhs[out++] = NULL; 1301 memcpy(lru->bhs, bhs, sizeof(bhs)); 1302 } 1303 bh_lru_unlock(); 1304 1305 if (evictee) 1306 __brelse(evictee); 1307 } 1308 1309 /* 1310 * Look up the bh in this cpu's LRU. If it's there, move it to the head. 1311 */ 1312 static struct buffer_head * 1313 lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size) 1314 { 1315 struct buffer_head *ret = NULL; 1316 struct bh_lru *lru; 1317 unsigned int i; 1318 1319 check_irqs_on(); 1320 bh_lru_lock(); 1321 lru = &__get_cpu_var(bh_lrus); 1322 for (i = 0; i < BH_LRU_SIZE; i++) { 1323 struct buffer_head *bh = lru->bhs[i]; 1324 1325 if (bh && bh->b_bdev == bdev && 1326 bh->b_blocknr == block && bh->b_size == size) { 1327 if (i) { 1328 while (i) { 1329 lru->bhs[i] = lru->bhs[i - 1]; 1330 i--; 1331 } 1332 lru->bhs[0] = bh; 1333 } 1334 get_bh(bh); 1335 ret = bh; 1336 break; 1337 } 1338 } 1339 bh_lru_unlock(); 1340 return ret; 1341 } 1342 1343 /* 1344 * Perform a pagecache lookup for the matching buffer. If it's there, refresh 1345 * it in the LRU and mark it as accessed. If it is not present then return 1346 * NULL 1347 */ 1348 struct buffer_head * 1349 __find_get_block(struct block_device *bdev, sector_t block, unsigned size) 1350 { 1351 struct buffer_head *bh = lookup_bh_lru(bdev, block, size); 1352 1353 if (bh == NULL) { 1354 bh = __find_get_block_slow(bdev, block); 1355 if (bh) 1356 bh_lru_install(bh); 1357 } 1358 if (bh) 1359 touch_buffer(bh); 1360 return bh; 1361 } 1362 EXPORT_SYMBOL(__find_get_block); 1363 1364 /* 1365 * __getblk will locate (and, if necessary, create) the buffer_head 1366 * which corresponds to the passed block_device, block and size. The 1367 * returned buffer has its reference count incremented. 1368 * 1369 * __getblk() cannot fail - it just keeps trying. If you pass it an 1370 * illegal block number, __getblk() will happily return a buffer_head 1371 * which represents the non-existent block. Very weird. 1372 * 1373 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers() 1374 * attempt is failing. FIXME, perhaps? 1375 */ 1376 struct buffer_head * 1377 __getblk(struct block_device *bdev, sector_t block, unsigned size) 1378 { 1379 struct buffer_head *bh = __find_get_block(bdev, block, size); 1380 1381 might_sleep(); 1382 if (bh == NULL) 1383 bh = __getblk_slow(bdev, block, size); 1384 return bh; 1385 } 1386 EXPORT_SYMBOL(__getblk); 1387 1388 /* 1389 * Do async read-ahead on a buffer.. 1390 */ 1391 void __breadahead(struct block_device *bdev, sector_t block, unsigned size) 1392 { 1393 struct buffer_head *bh = __getblk(bdev, block, size); 1394 if (likely(bh)) { 1395 ll_rw_block(READA, 1, &bh); 1396 brelse(bh); 1397 } 1398 } 1399 EXPORT_SYMBOL(__breadahead); 1400 1401 /** 1402 * __bread() - reads a specified block and returns the bh 1403 * @bdev: the block_device to read from 1404 * @block: number of block 1405 * @size: size (in bytes) to read 1406 * 1407 * Reads a specified block, and returns buffer head that contains it. 1408 * It returns NULL if the block was unreadable. 1409 */ 1410 struct buffer_head * 1411 __bread(struct block_device *bdev, sector_t block, unsigned size) 1412 { 1413 struct buffer_head *bh = __getblk(bdev, block, size); 1414 1415 if (likely(bh) && !buffer_uptodate(bh)) 1416 bh = __bread_slow(bh); 1417 return bh; 1418 } 1419 EXPORT_SYMBOL(__bread); 1420 1421 /* 1422 * invalidate_bh_lrus() is called rarely - but not only at unmount. 1423 * This doesn't race because it runs in each cpu either in irq 1424 * or with preempt disabled. 1425 */ 1426 static void invalidate_bh_lru(void *arg) 1427 { 1428 struct bh_lru *b = &get_cpu_var(bh_lrus); 1429 int i; 1430 1431 for (i = 0; i < BH_LRU_SIZE; i++) { 1432 brelse(b->bhs[i]); 1433 b->bhs[i] = NULL; 1434 } 1435 put_cpu_var(bh_lrus); 1436 } 1437 1438 void invalidate_bh_lrus(void) 1439 { 1440 on_each_cpu(invalidate_bh_lru, NULL, 1); 1441 } 1442 EXPORT_SYMBOL_GPL(invalidate_bh_lrus); 1443 1444 void set_bh_page(struct buffer_head *bh, 1445 struct page *page, unsigned long offset) 1446 { 1447 bh->b_page = page; 1448 BUG_ON(offset >= PAGE_SIZE); 1449 if (PageHighMem(page)) 1450 /* 1451 * This catches illegal uses and preserves the offset: 1452 */ 1453 bh->b_data = (char *)(0 + offset); 1454 else 1455 bh->b_data = page_address(page) + offset; 1456 } 1457 EXPORT_SYMBOL(set_bh_page); 1458 1459 /* 1460 * Called when truncating a buffer on a page completely. 1461 */ 1462 static void discard_buffer(struct buffer_head * bh) 1463 { 1464 lock_buffer(bh); 1465 clear_buffer_dirty(bh); 1466 bh->b_bdev = NULL; 1467 clear_buffer_mapped(bh); 1468 clear_buffer_req(bh); 1469 clear_buffer_new(bh); 1470 clear_buffer_delay(bh); 1471 clear_buffer_unwritten(bh); 1472 unlock_buffer(bh); 1473 } 1474 1475 /** 1476 * block_invalidatepage - invalidate part of all of a buffer-backed page 1477 * 1478 * @page: the page which is affected 1479 * @offset: the index of the truncation point 1480 * 1481 * block_invalidatepage() is called when all or part of the page has become 1482 * invalidatedby a truncate operation. 1483 * 1484 * block_invalidatepage() does not have to release all buffers, but it must 1485 * ensure that no dirty buffer is left outside @offset and that no I/O 1486 * is underway against any of the blocks which are outside the truncation 1487 * point. Because the caller is about to free (and possibly reuse) those 1488 * blocks on-disk. 1489 */ 1490 void block_invalidatepage(struct page *page, unsigned long offset) 1491 { 1492 struct buffer_head *head, *bh, *next; 1493 unsigned int curr_off = 0; 1494 1495 BUG_ON(!PageLocked(page)); 1496 if (!page_has_buffers(page)) 1497 goto out; 1498 1499 head = page_buffers(page); 1500 bh = head; 1501 do { 1502 unsigned int next_off = curr_off + bh->b_size; 1503 next = bh->b_this_page; 1504 1505 /* 1506 * is this block fully invalidated? 1507 */ 1508 if (offset <= curr_off) 1509 discard_buffer(bh); 1510 curr_off = next_off; 1511 bh = next; 1512 } while (bh != head); 1513 1514 /* 1515 * We release buffers only if the entire page is being invalidated. 1516 * The get_block cached value has been unconditionally invalidated, 1517 * so real IO is not possible anymore. 1518 */ 1519 if (offset == 0) 1520 try_to_release_page(page, 0); 1521 out: 1522 return; 1523 } 1524 EXPORT_SYMBOL(block_invalidatepage); 1525 1526 /* 1527 * We attach and possibly dirty the buffers atomically wrt 1528 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers 1529 * is already excluded via the page lock. 1530 */ 1531 void create_empty_buffers(struct page *page, 1532 unsigned long blocksize, unsigned long b_state) 1533 { 1534 struct buffer_head *bh, *head, *tail; 1535 1536 head = alloc_page_buffers(page, blocksize, 1); 1537 bh = head; 1538 do { 1539 bh->b_state |= b_state; 1540 tail = bh; 1541 bh = bh->b_this_page; 1542 } while (bh); 1543 tail->b_this_page = head; 1544 1545 spin_lock(&page->mapping->private_lock); 1546 if (PageUptodate(page) || PageDirty(page)) { 1547 bh = head; 1548 do { 1549 if (PageDirty(page)) 1550 set_buffer_dirty(bh); 1551 if (PageUptodate(page)) 1552 set_buffer_uptodate(bh); 1553 bh = bh->b_this_page; 1554 } while (bh != head); 1555 } 1556 attach_page_buffers(page, head); 1557 spin_unlock(&page->mapping->private_lock); 1558 } 1559 EXPORT_SYMBOL(create_empty_buffers); 1560 1561 /* 1562 * We are taking a block for data and we don't want any output from any 1563 * buffer-cache aliases starting from return from that function and 1564 * until the moment when something will explicitly mark the buffer 1565 * dirty (hopefully that will not happen until we will free that block ;-) 1566 * We don't even need to mark it not-uptodate - nobody can expect 1567 * anything from a newly allocated buffer anyway. We used to used 1568 * unmap_buffer() for such invalidation, but that was wrong. We definitely 1569 * don't want to mark the alias unmapped, for example - it would confuse 1570 * anyone who might pick it with bread() afterwards... 1571 * 1572 * Also.. Note that bforget() doesn't lock the buffer. So there can 1573 * be writeout I/O going on against recently-freed buffers. We don't 1574 * wait on that I/O in bforget() - it's more efficient to wait on the I/O 1575 * only if we really need to. That happens here. 1576 */ 1577 void unmap_underlying_metadata(struct block_device *bdev, sector_t block) 1578 { 1579 struct buffer_head *old_bh; 1580 1581 might_sleep(); 1582 1583 old_bh = __find_get_block_slow(bdev, block); 1584 if (old_bh) { 1585 clear_buffer_dirty(old_bh); 1586 wait_on_buffer(old_bh); 1587 clear_buffer_req(old_bh); 1588 __brelse(old_bh); 1589 } 1590 } 1591 EXPORT_SYMBOL(unmap_underlying_metadata); 1592 1593 /* 1594 * NOTE! All mapped/uptodate combinations are valid: 1595 * 1596 * Mapped Uptodate Meaning 1597 * 1598 * No No "unknown" - must do get_block() 1599 * No Yes "hole" - zero-filled 1600 * Yes No "allocated" - allocated on disk, not read in 1601 * Yes Yes "valid" - allocated and up-to-date in memory. 1602 * 1603 * "Dirty" is valid only with the last case (mapped+uptodate). 1604 */ 1605 1606 /* 1607 * While block_write_full_page is writing back the dirty buffers under 1608 * the page lock, whoever dirtied the buffers may decide to clean them 1609 * again at any time. We handle that by only looking at the buffer 1610 * state inside lock_buffer(). 1611 * 1612 * If block_write_full_page() is called for regular writeback 1613 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a 1614 * locked buffer. This only can happen if someone has written the buffer 1615 * directly, with submit_bh(). At the address_space level PageWriteback 1616 * prevents this contention from occurring. 1617 * 1618 * If block_write_full_page() is called with wbc->sync_mode == 1619 * WB_SYNC_ALL, the writes are posted using WRITE_SYNC_PLUG; this 1620 * causes the writes to be flagged as synchronous writes, but the 1621 * block device queue will NOT be unplugged, since usually many pages 1622 * will be pushed to the out before the higher-level caller actually 1623 * waits for the writes to be completed. The various wait functions, 1624 * such as wait_on_writeback_range() will ultimately call sync_page() 1625 * which will ultimately call blk_run_backing_dev(), which will end up 1626 * unplugging the device queue. 1627 */ 1628 static int __block_write_full_page(struct inode *inode, struct page *page, 1629 get_block_t *get_block, struct writeback_control *wbc, 1630 bh_end_io_t *handler) 1631 { 1632 int err; 1633 sector_t block; 1634 sector_t last_block; 1635 struct buffer_head *bh, *head; 1636 const unsigned blocksize = 1 << inode->i_blkbits; 1637 int nr_underway = 0; 1638 int write_op = (wbc->sync_mode == WB_SYNC_ALL ? 1639 WRITE_SYNC_PLUG : WRITE); 1640 1641 BUG_ON(!PageLocked(page)); 1642 1643 last_block = (i_size_read(inode) - 1) >> inode->i_blkbits; 1644 1645 if (!page_has_buffers(page)) { 1646 create_empty_buffers(page, blocksize, 1647 (1 << BH_Dirty)|(1 << BH_Uptodate)); 1648 } 1649 1650 /* 1651 * Be very careful. We have no exclusion from __set_page_dirty_buffers 1652 * here, and the (potentially unmapped) buffers may become dirty at 1653 * any time. If a buffer becomes dirty here after we've inspected it 1654 * then we just miss that fact, and the page stays dirty. 1655 * 1656 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers; 1657 * handle that here by just cleaning them. 1658 */ 1659 1660 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits); 1661 head = page_buffers(page); 1662 bh = head; 1663 1664 /* 1665 * Get all the dirty buffers mapped to disk addresses and 1666 * handle any aliases from the underlying blockdev's mapping. 1667 */ 1668 do { 1669 if (block > last_block) { 1670 /* 1671 * mapped buffers outside i_size will occur, because 1672 * this page can be outside i_size when there is a 1673 * truncate in progress. 1674 */ 1675 /* 1676 * The buffer was zeroed by block_write_full_page() 1677 */ 1678 clear_buffer_dirty(bh); 1679 set_buffer_uptodate(bh); 1680 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) && 1681 buffer_dirty(bh)) { 1682 WARN_ON(bh->b_size != blocksize); 1683 err = get_block(inode, block, bh, 1); 1684 if (err) 1685 goto recover; 1686 clear_buffer_delay(bh); 1687 if (buffer_new(bh)) { 1688 /* blockdev mappings never come here */ 1689 clear_buffer_new(bh); 1690 unmap_underlying_metadata(bh->b_bdev, 1691 bh->b_blocknr); 1692 } 1693 } 1694 bh = bh->b_this_page; 1695 block++; 1696 } while (bh != head); 1697 1698 do { 1699 if (!buffer_mapped(bh)) 1700 continue; 1701 /* 1702 * If it's a fully non-blocking write attempt and we cannot 1703 * lock the buffer then redirty the page. Note that this can 1704 * potentially cause a busy-wait loop from writeback threads 1705 * and kswapd activity, but those code paths have their own 1706 * higher-level throttling. 1707 */ 1708 if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) { 1709 lock_buffer(bh); 1710 } else if (!trylock_buffer(bh)) { 1711 redirty_page_for_writepage(wbc, page); 1712 continue; 1713 } 1714 if (test_clear_buffer_dirty(bh)) { 1715 mark_buffer_async_write_endio(bh, handler); 1716 } else { 1717 unlock_buffer(bh); 1718 } 1719 } while ((bh = bh->b_this_page) != head); 1720 1721 /* 1722 * The page and its buffers are protected by PageWriteback(), so we can 1723 * drop the bh refcounts early. 1724 */ 1725 BUG_ON(PageWriteback(page)); 1726 set_page_writeback(page); 1727 1728 do { 1729 struct buffer_head *next = bh->b_this_page; 1730 if (buffer_async_write(bh)) { 1731 submit_bh(write_op, bh); 1732 nr_underway++; 1733 } 1734 bh = next; 1735 } while (bh != head); 1736 unlock_page(page); 1737 1738 err = 0; 1739 done: 1740 if (nr_underway == 0) { 1741 /* 1742 * The page was marked dirty, but the buffers were 1743 * clean. Someone wrote them back by hand with 1744 * ll_rw_block/submit_bh. A rare case. 1745 */ 1746 end_page_writeback(page); 1747 1748 /* 1749 * The page and buffer_heads can be released at any time from 1750 * here on. 1751 */ 1752 } 1753 return err; 1754 1755 recover: 1756 /* 1757 * ENOSPC, or some other error. We may already have added some 1758 * blocks to the file, so we need to write these out to avoid 1759 * exposing stale data. 1760 * The page is currently locked and not marked for writeback 1761 */ 1762 bh = head; 1763 /* Recovery: lock and submit the mapped buffers */ 1764 do { 1765 if (buffer_mapped(bh) && buffer_dirty(bh) && 1766 !buffer_delay(bh)) { 1767 lock_buffer(bh); 1768 mark_buffer_async_write_endio(bh, handler); 1769 } else { 1770 /* 1771 * The buffer may have been set dirty during 1772 * attachment to a dirty page. 1773 */ 1774 clear_buffer_dirty(bh); 1775 } 1776 } while ((bh = bh->b_this_page) != head); 1777 SetPageError(page); 1778 BUG_ON(PageWriteback(page)); 1779 mapping_set_error(page->mapping, err); 1780 set_page_writeback(page); 1781 do { 1782 struct buffer_head *next = bh->b_this_page; 1783 if (buffer_async_write(bh)) { 1784 clear_buffer_dirty(bh); 1785 submit_bh(write_op, bh); 1786 nr_underway++; 1787 } 1788 bh = next; 1789 } while (bh != head); 1790 unlock_page(page); 1791 goto done; 1792 } 1793 1794 /* 1795 * If a page has any new buffers, zero them out here, and mark them uptodate 1796 * and dirty so they'll be written out (in order to prevent uninitialised 1797 * block data from leaking). And clear the new bit. 1798 */ 1799 void page_zero_new_buffers(struct page *page, unsigned from, unsigned to) 1800 { 1801 unsigned int block_start, block_end; 1802 struct buffer_head *head, *bh; 1803 1804 BUG_ON(!PageLocked(page)); 1805 if (!page_has_buffers(page)) 1806 return; 1807 1808 bh = head = page_buffers(page); 1809 block_start = 0; 1810 do { 1811 block_end = block_start + bh->b_size; 1812 1813 if (buffer_new(bh)) { 1814 if (block_end > from && block_start < to) { 1815 if (!PageUptodate(page)) { 1816 unsigned start, size; 1817 1818 start = max(from, block_start); 1819 size = min(to, block_end) - start; 1820 1821 zero_user(page, start, size); 1822 set_buffer_uptodate(bh); 1823 } 1824 1825 clear_buffer_new(bh); 1826 mark_buffer_dirty(bh); 1827 } 1828 } 1829 1830 block_start = block_end; 1831 bh = bh->b_this_page; 1832 } while (bh != head); 1833 } 1834 EXPORT_SYMBOL(page_zero_new_buffers); 1835 1836 static int __block_prepare_write(struct inode *inode, struct page *page, 1837 unsigned from, unsigned to, get_block_t *get_block) 1838 { 1839 unsigned block_start, block_end; 1840 sector_t block; 1841 int err = 0; 1842 unsigned blocksize, bbits; 1843 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait; 1844 1845 BUG_ON(!PageLocked(page)); 1846 BUG_ON(from > PAGE_CACHE_SIZE); 1847 BUG_ON(to > PAGE_CACHE_SIZE); 1848 BUG_ON(from > to); 1849 1850 blocksize = 1 << inode->i_blkbits; 1851 if (!page_has_buffers(page)) 1852 create_empty_buffers(page, blocksize, 0); 1853 head = page_buffers(page); 1854 1855 bbits = inode->i_blkbits; 1856 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits); 1857 1858 for(bh = head, block_start = 0; bh != head || !block_start; 1859 block++, block_start=block_end, bh = bh->b_this_page) { 1860 block_end = block_start + blocksize; 1861 if (block_end <= from || block_start >= to) { 1862 if (PageUptodate(page)) { 1863 if (!buffer_uptodate(bh)) 1864 set_buffer_uptodate(bh); 1865 } 1866 continue; 1867 } 1868 if (buffer_new(bh)) 1869 clear_buffer_new(bh); 1870 if (!buffer_mapped(bh)) { 1871 WARN_ON(bh->b_size != blocksize); 1872 err = get_block(inode, block, bh, 1); 1873 if (err) 1874 break; 1875 if (buffer_new(bh)) { 1876 unmap_underlying_metadata(bh->b_bdev, 1877 bh->b_blocknr); 1878 if (PageUptodate(page)) { 1879 clear_buffer_new(bh); 1880 set_buffer_uptodate(bh); 1881 mark_buffer_dirty(bh); 1882 continue; 1883 } 1884 if (block_end > to || block_start < from) 1885 zero_user_segments(page, 1886 to, block_end, 1887 block_start, from); 1888 continue; 1889 } 1890 } 1891 if (PageUptodate(page)) { 1892 if (!buffer_uptodate(bh)) 1893 set_buffer_uptodate(bh); 1894 continue; 1895 } 1896 if (!buffer_uptodate(bh) && !buffer_delay(bh) && 1897 !buffer_unwritten(bh) && 1898 (block_start < from || block_end > to)) { 1899 ll_rw_block(READ, 1, &bh); 1900 *wait_bh++=bh; 1901 } 1902 } 1903 /* 1904 * If we issued read requests - let them complete. 1905 */ 1906 while(wait_bh > wait) { 1907 wait_on_buffer(*--wait_bh); 1908 if (!buffer_uptodate(*wait_bh)) 1909 err = -EIO; 1910 } 1911 if (unlikely(err)) 1912 page_zero_new_buffers(page, from, to); 1913 return err; 1914 } 1915 1916 static int __block_commit_write(struct inode *inode, struct page *page, 1917 unsigned from, unsigned to) 1918 { 1919 unsigned block_start, block_end; 1920 int partial = 0; 1921 unsigned blocksize; 1922 struct buffer_head *bh, *head; 1923 1924 blocksize = 1 << inode->i_blkbits; 1925 1926 for(bh = head = page_buffers(page), block_start = 0; 1927 bh != head || !block_start; 1928 block_start=block_end, bh = bh->b_this_page) { 1929 block_end = block_start + blocksize; 1930 if (block_end <= from || block_start >= to) { 1931 if (!buffer_uptodate(bh)) 1932 partial = 1; 1933 } else { 1934 set_buffer_uptodate(bh); 1935 mark_buffer_dirty(bh); 1936 } 1937 clear_buffer_new(bh); 1938 } 1939 1940 /* 1941 * If this is a partial write which happened to make all buffers 1942 * uptodate then we can optimize away a bogus readpage() for 1943 * the next read(). Here we 'discover' whether the page went 1944 * uptodate as a result of this (potentially partial) write. 1945 */ 1946 if (!partial) 1947 SetPageUptodate(page); 1948 return 0; 1949 } 1950 1951 /* 1952 * Filesystems implementing the new truncate sequence should use the 1953 * _newtrunc postfix variant which won't incorrectly call vmtruncate. 1954 * The filesystem needs to handle block truncation upon failure. 1955 */ 1956 int block_write_begin_newtrunc(struct file *file, struct address_space *mapping, 1957 loff_t pos, unsigned len, unsigned flags, 1958 struct page **pagep, void **fsdata, 1959 get_block_t *get_block) 1960 { 1961 struct inode *inode = mapping->host; 1962 int status = 0; 1963 struct page *page; 1964 pgoff_t index; 1965 unsigned start, end; 1966 int ownpage = 0; 1967 1968 index = pos >> PAGE_CACHE_SHIFT; 1969 start = pos & (PAGE_CACHE_SIZE - 1); 1970 end = start + len; 1971 1972 page = *pagep; 1973 if (page == NULL) { 1974 ownpage = 1; 1975 page = grab_cache_page_write_begin(mapping, index, flags); 1976 if (!page) { 1977 status = -ENOMEM; 1978 goto out; 1979 } 1980 *pagep = page; 1981 } else 1982 BUG_ON(!PageLocked(page)); 1983 1984 status = __block_prepare_write(inode, page, start, end, get_block); 1985 if (unlikely(status)) { 1986 ClearPageUptodate(page); 1987 1988 if (ownpage) { 1989 unlock_page(page); 1990 page_cache_release(page); 1991 *pagep = NULL; 1992 } 1993 } 1994 1995 out: 1996 return status; 1997 } 1998 EXPORT_SYMBOL(block_write_begin_newtrunc); 1999 2000 /* 2001 * block_write_begin takes care of the basic task of block allocation and 2002 * bringing partial write blocks uptodate first. 2003 * 2004 * If *pagep is not NULL, then block_write_begin uses the locked page 2005 * at *pagep rather than allocating its own. In this case, the page will 2006 * not be unlocked or deallocated on failure. 2007 */ 2008 int block_write_begin(struct file *file, struct address_space *mapping, 2009 loff_t pos, unsigned len, unsigned flags, 2010 struct page **pagep, void **fsdata, 2011 get_block_t *get_block) 2012 { 2013 int ret; 2014 2015 ret = block_write_begin_newtrunc(file, mapping, pos, len, flags, 2016 pagep, fsdata, get_block); 2017 2018 /* 2019 * prepare_write() may have instantiated a few blocks 2020 * outside i_size. Trim these off again. Don't need 2021 * i_size_read because we hold i_mutex. 2022 * 2023 * Filesystems which pass down their own page also cannot 2024 * call into vmtruncate here because it would lead to lock 2025 * inversion problems (*pagep is locked). This is a further 2026 * example of where the old truncate sequence is inadequate. 2027 */ 2028 if (unlikely(ret) && *pagep == NULL) { 2029 loff_t isize = mapping->host->i_size; 2030 if (pos + len > isize) 2031 vmtruncate(mapping->host, isize); 2032 } 2033 2034 return ret; 2035 } 2036 EXPORT_SYMBOL(block_write_begin); 2037 2038 int block_write_end(struct file *file, struct address_space *mapping, 2039 loff_t pos, unsigned len, unsigned copied, 2040 struct page *page, void *fsdata) 2041 { 2042 struct inode *inode = mapping->host; 2043 unsigned start; 2044 2045 start = pos & (PAGE_CACHE_SIZE - 1); 2046 2047 if (unlikely(copied < len)) { 2048 /* 2049 * The buffers that were written will now be uptodate, so we 2050 * don't have to worry about a readpage reading them and 2051 * overwriting a partial write. However if we have encountered 2052 * a short write and only partially written into a buffer, it 2053 * will not be marked uptodate, so a readpage might come in and 2054 * destroy our partial write. 2055 * 2056 * Do the simplest thing, and just treat any short write to a 2057 * non uptodate page as a zero-length write, and force the 2058 * caller to redo the whole thing. 2059 */ 2060 if (!PageUptodate(page)) 2061 copied = 0; 2062 2063 page_zero_new_buffers(page, start+copied, start+len); 2064 } 2065 flush_dcache_page(page); 2066 2067 /* This could be a short (even 0-length) commit */ 2068 __block_commit_write(inode, page, start, start+copied); 2069 2070 return copied; 2071 } 2072 EXPORT_SYMBOL(block_write_end); 2073 2074 int generic_write_end(struct file *file, struct address_space *mapping, 2075 loff_t pos, unsigned len, unsigned copied, 2076 struct page *page, void *fsdata) 2077 { 2078 struct inode *inode = mapping->host; 2079 int i_size_changed = 0; 2080 2081 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata); 2082 2083 /* 2084 * No need to use i_size_read() here, the i_size 2085 * cannot change under us because we hold i_mutex. 2086 * 2087 * But it's important to update i_size while still holding page lock: 2088 * page writeout could otherwise come in and zero beyond i_size. 2089 */ 2090 if (pos+copied > inode->i_size) { 2091 i_size_write(inode, pos+copied); 2092 i_size_changed = 1; 2093 } 2094 2095 unlock_page(page); 2096 page_cache_release(page); 2097 2098 /* 2099 * Don't mark the inode dirty under page lock. First, it unnecessarily 2100 * makes the holding time of page lock longer. Second, it forces lock 2101 * ordering of page lock and transaction start for journaling 2102 * filesystems. 2103 */ 2104 if (i_size_changed) 2105 mark_inode_dirty(inode); 2106 2107 return copied; 2108 } 2109 EXPORT_SYMBOL(generic_write_end); 2110 2111 /* 2112 * block_is_partially_uptodate checks whether buffers within a page are 2113 * uptodate or not. 2114 * 2115 * Returns true if all buffers which correspond to a file portion 2116 * we want to read are uptodate. 2117 */ 2118 int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc, 2119 unsigned long from) 2120 { 2121 struct inode *inode = page->mapping->host; 2122 unsigned block_start, block_end, blocksize; 2123 unsigned to; 2124 struct buffer_head *bh, *head; 2125 int ret = 1; 2126 2127 if (!page_has_buffers(page)) 2128 return 0; 2129 2130 blocksize = 1 << inode->i_blkbits; 2131 to = min_t(unsigned, PAGE_CACHE_SIZE - from, desc->count); 2132 to = from + to; 2133 if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize) 2134 return 0; 2135 2136 head = page_buffers(page); 2137 bh = head; 2138 block_start = 0; 2139 do { 2140 block_end = block_start + blocksize; 2141 if (block_end > from && block_start < to) { 2142 if (!buffer_uptodate(bh)) { 2143 ret = 0; 2144 break; 2145 } 2146 if (block_end >= to) 2147 break; 2148 } 2149 block_start = block_end; 2150 bh = bh->b_this_page; 2151 } while (bh != head); 2152 2153 return ret; 2154 } 2155 EXPORT_SYMBOL(block_is_partially_uptodate); 2156 2157 /* 2158 * Generic "read page" function for block devices that have the normal 2159 * get_block functionality. This is most of the block device filesystems. 2160 * Reads the page asynchronously --- the unlock_buffer() and 2161 * set/clear_buffer_uptodate() functions propagate buffer state into the 2162 * page struct once IO has completed. 2163 */ 2164 int block_read_full_page(struct page *page, get_block_t *get_block) 2165 { 2166 struct inode *inode = page->mapping->host; 2167 sector_t iblock, lblock; 2168 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE]; 2169 unsigned int blocksize; 2170 int nr, i; 2171 int fully_mapped = 1; 2172 2173 BUG_ON(!PageLocked(page)); 2174 blocksize = 1 << inode->i_blkbits; 2175 if (!page_has_buffers(page)) 2176 create_empty_buffers(page, blocksize, 0); 2177 head = page_buffers(page); 2178 2179 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits); 2180 lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits; 2181 bh = head; 2182 nr = 0; 2183 i = 0; 2184 2185 do { 2186 if (buffer_uptodate(bh)) 2187 continue; 2188 2189 if (!buffer_mapped(bh)) { 2190 int err = 0; 2191 2192 fully_mapped = 0; 2193 if (iblock < lblock) { 2194 WARN_ON(bh->b_size != blocksize); 2195 err = get_block(inode, iblock, bh, 0); 2196 if (err) 2197 SetPageError(page); 2198 } 2199 if (!buffer_mapped(bh)) { 2200 zero_user(page, i * blocksize, blocksize); 2201 if (!err) 2202 set_buffer_uptodate(bh); 2203 continue; 2204 } 2205 /* 2206 * get_block() might have updated the buffer 2207 * synchronously 2208 */ 2209 if (buffer_uptodate(bh)) 2210 continue; 2211 } 2212 arr[nr++] = bh; 2213 } while (i++, iblock++, (bh = bh->b_this_page) != head); 2214 2215 if (fully_mapped) 2216 SetPageMappedToDisk(page); 2217 2218 if (!nr) { 2219 /* 2220 * All buffers are uptodate - we can set the page uptodate 2221 * as well. But not if get_block() returned an error. 2222 */ 2223 if (!PageError(page)) 2224 SetPageUptodate(page); 2225 unlock_page(page); 2226 return 0; 2227 } 2228 2229 /* Stage two: lock the buffers */ 2230 for (i = 0; i < nr; i++) { 2231 bh = arr[i]; 2232 lock_buffer(bh); 2233 mark_buffer_async_read(bh); 2234 } 2235 2236 /* 2237 * Stage 3: start the IO. Check for uptodateness 2238 * inside the buffer lock in case another process reading 2239 * the underlying blockdev brought it uptodate (the sct fix). 2240 */ 2241 for (i = 0; i < nr; i++) { 2242 bh = arr[i]; 2243 if (buffer_uptodate(bh)) 2244 end_buffer_async_read(bh, 1); 2245 else 2246 submit_bh(READ, bh); 2247 } 2248 return 0; 2249 } 2250 EXPORT_SYMBOL(block_read_full_page); 2251 2252 /* utility function for filesystems that need to do work on expanding 2253 * truncates. Uses filesystem pagecache writes to allow the filesystem to 2254 * deal with the hole. 2255 */ 2256 int generic_cont_expand_simple(struct inode *inode, loff_t size) 2257 { 2258 struct address_space *mapping = inode->i_mapping; 2259 struct page *page; 2260 void *fsdata; 2261 int err; 2262 2263 err = inode_newsize_ok(inode, size); 2264 if (err) 2265 goto out; 2266 2267 err = pagecache_write_begin(NULL, mapping, size, 0, 2268 AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND, 2269 &page, &fsdata); 2270 if (err) 2271 goto out; 2272 2273 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata); 2274 BUG_ON(err > 0); 2275 2276 out: 2277 return err; 2278 } 2279 EXPORT_SYMBOL(generic_cont_expand_simple); 2280 2281 static int cont_expand_zero(struct file *file, struct address_space *mapping, 2282 loff_t pos, loff_t *bytes) 2283 { 2284 struct inode *inode = mapping->host; 2285 unsigned blocksize = 1 << inode->i_blkbits; 2286 struct page *page; 2287 void *fsdata; 2288 pgoff_t index, curidx; 2289 loff_t curpos; 2290 unsigned zerofrom, offset, len; 2291 int err = 0; 2292 2293 index = pos >> PAGE_CACHE_SHIFT; 2294 offset = pos & ~PAGE_CACHE_MASK; 2295 2296 while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) { 2297 zerofrom = curpos & ~PAGE_CACHE_MASK; 2298 if (zerofrom & (blocksize-1)) { 2299 *bytes |= (blocksize-1); 2300 (*bytes)++; 2301 } 2302 len = PAGE_CACHE_SIZE - zerofrom; 2303 2304 err = pagecache_write_begin(file, mapping, curpos, len, 2305 AOP_FLAG_UNINTERRUPTIBLE, 2306 &page, &fsdata); 2307 if (err) 2308 goto out; 2309 zero_user(page, zerofrom, len); 2310 err = pagecache_write_end(file, mapping, curpos, len, len, 2311 page, fsdata); 2312 if (err < 0) 2313 goto out; 2314 BUG_ON(err != len); 2315 err = 0; 2316 2317 balance_dirty_pages_ratelimited(mapping); 2318 } 2319 2320 /* page covers the boundary, find the boundary offset */ 2321 if (index == curidx) { 2322 zerofrom = curpos & ~PAGE_CACHE_MASK; 2323 /* if we will expand the thing last block will be filled */ 2324 if (offset <= zerofrom) { 2325 goto out; 2326 } 2327 if (zerofrom & (blocksize-1)) { 2328 *bytes |= (blocksize-1); 2329 (*bytes)++; 2330 } 2331 len = offset - zerofrom; 2332 2333 err = pagecache_write_begin(file, mapping, curpos, len, 2334 AOP_FLAG_UNINTERRUPTIBLE, 2335 &page, &fsdata); 2336 if (err) 2337 goto out; 2338 zero_user(page, zerofrom, len); 2339 err = pagecache_write_end(file, mapping, curpos, len, len, 2340 page, fsdata); 2341 if (err < 0) 2342 goto out; 2343 BUG_ON(err != len); 2344 err = 0; 2345 } 2346 out: 2347 return err; 2348 } 2349 2350 /* 2351 * For moronic filesystems that do not allow holes in file. 2352 * We may have to extend the file. 2353 */ 2354 int cont_write_begin_newtrunc(struct file *file, struct address_space *mapping, 2355 loff_t pos, unsigned len, unsigned flags, 2356 struct page **pagep, void **fsdata, 2357 get_block_t *get_block, loff_t *bytes) 2358 { 2359 struct inode *inode = mapping->host; 2360 unsigned blocksize = 1 << inode->i_blkbits; 2361 unsigned zerofrom; 2362 int err; 2363 2364 err = cont_expand_zero(file, mapping, pos, bytes); 2365 if (err) 2366 goto out; 2367 2368 zerofrom = *bytes & ~PAGE_CACHE_MASK; 2369 if (pos+len > *bytes && zerofrom & (blocksize-1)) { 2370 *bytes |= (blocksize-1); 2371 (*bytes)++; 2372 } 2373 2374 *pagep = NULL; 2375 err = block_write_begin_newtrunc(file, mapping, pos, len, 2376 flags, pagep, fsdata, get_block); 2377 out: 2378 return err; 2379 } 2380 EXPORT_SYMBOL(cont_write_begin_newtrunc); 2381 2382 int cont_write_begin(struct file *file, struct address_space *mapping, 2383 loff_t pos, unsigned len, unsigned flags, 2384 struct page **pagep, void **fsdata, 2385 get_block_t *get_block, loff_t *bytes) 2386 { 2387 int ret; 2388 2389 ret = cont_write_begin_newtrunc(file, mapping, pos, len, flags, 2390 pagep, fsdata, get_block, bytes); 2391 if (unlikely(ret)) { 2392 loff_t isize = mapping->host->i_size; 2393 if (pos + len > isize) 2394 vmtruncate(mapping->host, isize); 2395 } 2396 2397 return ret; 2398 } 2399 EXPORT_SYMBOL(cont_write_begin); 2400 2401 int block_prepare_write(struct page *page, unsigned from, unsigned to, 2402 get_block_t *get_block) 2403 { 2404 struct inode *inode = page->mapping->host; 2405 int err = __block_prepare_write(inode, page, from, to, get_block); 2406 if (err) 2407 ClearPageUptodate(page); 2408 return err; 2409 } 2410 EXPORT_SYMBOL(block_prepare_write); 2411 2412 int block_commit_write(struct page *page, unsigned from, unsigned to) 2413 { 2414 struct inode *inode = page->mapping->host; 2415 __block_commit_write(inode,page,from,to); 2416 return 0; 2417 } 2418 EXPORT_SYMBOL(block_commit_write); 2419 2420 /* 2421 * block_page_mkwrite() is not allowed to change the file size as it gets 2422 * called from a page fault handler when a page is first dirtied. Hence we must 2423 * be careful to check for EOF conditions here. We set the page up correctly 2424 * for a written page which means we get ENOSPC checking when writing into 2425 * holes and correct delalloc and unwritten extent mapping on filesystems that 2426 * support these features. 2427 * 2428 * We are not allowed to take the i_mutex here so we have to play games to 2429 * protect against truncate races as the page could now be beyond EOF. Because 2430 * truncate writes the inode size before removing pages, once we have the 2431 * page lock we can determine safely if the page is beyond EOF. If it is not 2432 * beyond EOF, then the page is guaranteed safe against truncation until we 2433 * unlock the page. 2434 */ 2435 int 2436 block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, 2437 get_block_t get_block) 2438 { 2439 struct page *page = vmf->page; 2440 struct inode *inode = vma->vm_file->f_path.dentry->d_inode; 2441 unsigned long end; 2442 loff_t size; 2443 int ret = VM_FAULT_NOPAGE; /* make the VM retry the fault */ 2444 2445 lock_page(page); 2446 size = i_size_read(inode); 2447 if ((page->mapping != inode->i_mapping) || 2448 (page_offset(page) > size)) { 2449 /* page got truncated out from underneath us */ 2450 unlock_page(page); 2451 goto out; 2452 } 2453 2454 /* page is wholly or partially inside EOF */ 2455 if (((page->index + 1) << PAGE_CACHE_SHIFT) > size) 2456 end = size & ~PAGE_CACHE_MASK; 2457 else 2458 end = PAGE_CACHE_SIZE; 2459 2460 ret = block_prepare_write(page, 0, end, get_block); 2461 if (!ret) 2462 ret = block_commit_write(page, 0, end); 2463 2464 if (unlikely(ret)) { 2465 unlock_page(page); 2466 if (ret == -ENOMEM) 2467 ret = VM_FAULT_OOM; 2468 else /* -ENOSPC, -EIO, etc */ 2469 ret = VM_FAULT_SIGBUS; 2470 } else 2471 ret = VM_FAULT_LOCKED; 2472 2473 out: 2474 return ret; 2475 } 2476 EXPORT_SYMBOL(block_page_mkwrite); 2477 2478 /* 2479 * nobh_write_begin()'s prereads are special: the buffer_heads are freed 2480 * immediately, while under the page lock. So it needs a special end_io 2481 * handler which does not touch the bh after unlocking it. 2482 */ 2483 static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate) 2484 { 2485 __end_buffer_read_notouch(bh, uptodate); 2486 } 2487 2488 /* 2489 * Attach the singly-linked list of buffers created by nobh_write_begin, to 2490 * the page (converting it to circular linked list and taking care of page 2491 * dirty races). 2492 */ 2493 static void attach_nobh_buffers(struct page *page, struct buffer_head *head) 2494 { 2495 struct buffer_head *bh; 2496 2497 BUG_ON(!PageLocked(page)); 2498 2499 spin_lock(&page->mapping->private_lock); 2500 bh = head; 2501 do { 2502 if (PageDirty(page)) 2503 set_buffer_dirty(bh); 2504 if (!bh->b_this_page) 2505 bh->b_this_page = head; 2506 bh = bh->b_this_page; 2507 } while (bh != head); 2508 attach_page_buffers(page, head); 2509 spin_unlock(&page->mapping->private_lock); 2510 } 2511 2512 /* 2513 * Filesystems implementing the new truncate sequence should use the 2514 * _newtrunc postfix variant which won't incorrectly call vmtruncate. 2515 * The filesystem needs to handle block truncation upon failure. 2516 */ 2517 int nobh_write_begin_newtrunc(struct file *file, struct address_space *mapping, 2518 loff_t pos, unsigned len, unsigned flags, 2519 struct page **pagep, void **fsdata, 2520 get_block_t *get_block) 2521 { 2522 struct inode *inode = mapping->host; 2523 const unsigned blkbits = inode->i_blkbits; 2524 const unsigned blocksize = 1 << blkbits; 2525 struct buffer_head *head, *bh; 2526 struct page *page; 2527 pgoff_t index; 2528 unsigned from, to; 2529 unsigned block_in_page; 2530 unsigned block_start, block_end; 2531 sector_t block_in_file; 2532 int nr_reads = 0; 2533 int ret = 0; 2534 int is_mapped_to_disk = 1; 2535 2536 index = pos >> PAGE_CACHE_SHIFT; 2537 from = pos & (PAGE_CACHE_SIZE - 1); 2538 to = from + len; 2539 2540 page = grab_cache_page_write_begin(mapping, index, flags); 2541 if (!page) 2542 return -ENOMEM; 2543 *pagep = page; 2544 *fsdata = NULL; 2545 2546 if (page_has_buffers(page)) { 2547 unlock_page(page); 2548 page_cache_release(page); 2549 *pagep = NULL; 2550 return block_write_begin_newtrunc(file, mapping, pos, len, 2551 flags, pagep, fsdata, get_block); 2552 } 2553 2554 if (PageMappedToDisk(page)) 2555 return 0; 2556 2557 /* 2558 * Allocate buffers so that we can keep track of state, and potentially 2559 * attach them to the page if an error occurs. In the common case of 2560 * no error, they will just be freed again without ever being attached 2561 * to the page (which is all OK, because we're under the page lock). 2562 * 2563 * Be careful: the buffer linked list is a NULL terminated one, rather 2564 * than the circular one we're used to. 2565 */ 2566 head = alloc_page_buffers(page, blocksize, 0); 2567 if (!head) { 2568 ret = -ENOMEM; 2569 goto out_release; 2570 } 2571 2572 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits); 2573 2574 /* 2575 * We loop across all blocks in the page, whether or not they are 2576 * part of the affected region. This is so we can discover if the 2577 * page is fully mapped-to-disk. 2578 */ 2579 for (block_start = 0, block_in_page = 0, bh = head; 2580 block_start < PAGE_CACHE_SIZE; 2581 block_in_page++, block_start += blocksize, bh = bh->b_this_page) { 2582 int create; 2583 2584 block_end = block_start + blocksize; 2585 bh->b_state = 0; 2586 create = 1; 2587 if (block_start >= to) 2588 create = 0; 2589 ret = get_block(inode, block_in_file + block_in_page, 2590 bh, create); 2591 if (ret) 2592 goto failed; 2593 if (!buffer_mapped(bh)) 2594 is_mapped_to_disk = 0; 2595 if (buffer_new(bh)) 2596 unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr); 2597 if (PageUptodate(page)) { 2598 set_buffer_uptodate(bh); 2599 continue; 2600 } 2601 if (buffer_new(bh) || !buffer_mapped(bh)) { 2602 zero_user_segments(page, block_start, from, 2603 to, block_end); 2604 continue; 2605 } 2606 if (buffer_uptodate(bh)) 2607 continue; /* reiserfs does this */ 2608 if (block_start < from || block_end > to) { 2609 lock_buffer(bh); 2610 bh->b_end_io = end_buffer_read_nobh; 2611 submit_bh(READ, bh); 2612 nr_reads++; 2613 } 2614 } 2615 2616 if (nr_reads) { 2617 /* 2618 * The page is locked, so these buffers are protected from 2619 * any VM or truncate activity. Hence we don't need to care 2620 * for the buffer_head refcounts. 2621 */ 2622 for (bh = head; bh; bh = bh->b_this_page) { 2623 wait_on_buffer(bh); 2624 if (!buffer_uptodate(bh)) 2625 ret = -EIO; 2626 } 2627 if (ret) 2628 goto failed; 2629 } 2630 2631 if (is_mapped_to_disk) 2632 SetPageMappedToDisk(page); 2633 2634 *fsdata = head; /* to be released by nobh_write_end */ 2635 2636 return 0; 2637 2638 failed: 2639 BUG_ON(!ret); 2640 /* 2641 * Error recovery is a bit difficult. We need to zero out blocks that 2642 * were newly allocated, and dirty them to ensure they get written out. 2643 * Buffers need to be attached to the page at this point, otherwise 2644 * the handling of potential IO errors during writeout would be hard 2645 * (could try doing synchronous writeout, but what if that fails too?) 2646 */ 2647 attach_nobh_buffers(page, head); 2648 page_zero_new_buffers(page, from, to); 2649 2650 out_release: 2651 unlock_page(page); 2652 page_cache_release(page); 2653 *pagep = NULL; 2654 2655 return ret; 2656 } 2657 EXPORT_SYMBOL(nobh_write_begin_newtrunc); 2658 2659 /* 2660 * On entry, the page is fully not uptodate. 2661 * On exit the page is fully uptodate in the areas outside (from,to) 2662 */ 2663 int nobh_write_begin(struct file *file, struct address_space *mapping, 2664 loff_t pos, unsigned len, unsigned flags, 2665 struct page **pagep, void **fsdata, 2666 get_block_t *get_block) 2667 { 2668 int ret; 2669 2670 ret = nobh_write_begin_newtrunc(file, mapping, pos, len, flags, 2671 pagep, fsdata, get_block); 2672 2673 /* 2674 * prepare_write() may have instantiated a few blocks 2675 * outside i_size. Trim these off again. Don't need 2676 * i_size_read because we hold i_mutex. 2677 */ 2678 if (unlikely(ret)) { 2679 loff_t isize = mapping->host->i_size; 2680 if (pos + len > isize) 2681 vmtruncate(mapping->host, isize); 2682 } 2683 2684 return ret; 2685 } 2686 EXPORT_SYMBOL(nobh_write_begin); 2687 2688 int nobh_write_end(struct file *file, struct address_space *mapping, 2689 loff_t pos, unsigned len, unsigned copied, 2690 struct page *page, void *fsdata) 2691 { 2692 struct inode *inode = page->mapping->host; 2693 struct buffer_head *head = fsdata; 2694 struct buffer_head *bh; 2695 BUG_ON(fsdata != NULL && page_has_buffers(page)); 2696 2697 if (unlikely(copied < len) && head) 2698 attach_nobh_buffers(page, head); 2699 if (page_has_buffers(page)) 2700 return generic_write_end(file, mapping, pos, len, 2701 copied, page, fsdata); 2702 2703 SetPageUptodate(page); 2704 set_page_dirty(page); 2705 if (pos+copied > inode->i_size) { 2706 i_size_write(inode, pos+copied); 2707 mark_inode_dirty(inode); 2708 } 2709 2710 unlock_page(page); 2711 page_cache_release(page); 2712 2713 while (head) { 2714 bh = head; 2715 head = head->b_this_page; 2716 free_buffer_head(bh); 2717 } 2718 2719 return copied; 2720 } 2721 EXPORT_SYMBOL(nobh_write_end); 2722 2723 /* 2724 * nobh_writepage() - based on block_full_write_page() except 2725 * that it tries to operate without attaching bufferheads to 2726 * the page. 2727 */ 2728 int nobh_writepage(struct page *page, get_block_t *get_block, 2729 struct writeback_control *wbc) 2730 { 2731 struct inode * const inode = page->mapping->host; 2732 loff_t i_size = i_size_read(inode); 2733 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT; 2734 unsigned offset; 2735 int ret; 2736 2737 /* Is the page fully inside i_size? */ 2738 if (page->index < end_index) 2739 goto out; 2740 2741 /* Is the page fully outside i_size? (truncate in progress) */ 2742 offset = i_size & (PAGE_CACHE_SIZE-1); 2743 if (page->index >= end_index+1 || !offset) { 2744 /* 2745 * The page may have dirty, unmapped buffers. For example, 2746 * they may have been added in ext3_writepage(). Make them 2747 * freeable here, so the page does not leak. 2748 */ 2749 #if 0 2750 /* Not really sure about this - do we need this ? */ 2751 if (page->mapping->a_ops->invalidatepage) 2752 page->mapping->a_ops->invalidatepage(page, offset); 2753 #endif 2754 unlock_page(page); 2755 return 0; /* don't care */ 2756 } 2757 2758 /* 2759 * The page straddles i_size. It must be zeroed out on each and every 2760 * writepage invocation because it may be mmapped. "A file is mapped 2761 * in multiples of the page size. For a file that is not a multiple of 2762 * the page size, the remaining memory is zeroed when mapped, and 2763 * writes to that region are not written out to the file." 2764 */ 2765 zero_user_segment(page, offset, PAGE_CACHE_SIZE); 2766 out: 2767 ret = mpage_writepage(page, get_block, wbc); 2768 if (ret == -EAGAIN) 2769 ret = __block_write_full_page(inode, page, get_block, wbc, 2770 end_buffer_async_write); 2771 return ret; 2772 } 2773 EXPORT_SYMBOL(nobh_writepage); 2774 2775 int nobh_truncate_page(struct address_space *mapping, 2776 loff_t from, get_block_t *get_block) 2777 { 2778 pgoff_t index = from >> PAGE_CACHE_SHIFT; 2779 unsigned offset = from & (PAGE_CACHE_SIZE-1); 2780 unsigned blocksize; 2781 sector_t iblock; 2782 unsigned length, pos; 2783 struct inode *inode = mapping->host; 2784 struct page *page; 2785 struct buffer_head map_bh; 2786 int err; 2787 2788 blocksize = 1 << inode->i_blkbits; 2789 length = offset & (blocksize - 1); 2790 2791 /* Block boundary? Nothing to do */ 2792 if (!length) 2793 return 0; 2794 2795 length = blocksize - length; 2796 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits); 2797 2798 page = grab_cache_page(mapping, index); 2799 err = -ENOMEM; 2800 if (!page) 2801 goto out; 2802 2803 if (page_has_buffers(page)) { 2804 has_buffers: 2805 unlock_page(page); 2806 page_cache_release(page); 2807 return block_truncate_page(mapping, from, get_block); 2808 } 2809 2810 /* Find the buffer that contains "offset" */ 2811 pos = blocksize; 2812 while (offset >= pos) { 2813 iblock++; 2814 pos += blocksize; 2815 } 2816 2817 map_bh.b_size = blocksize; 2818 map_bh.b_state = 0; 2819 err = get_block(inode, iblock, &map_bh, 0); 2820 if (err) 2821 goto unlock; 2822 /* unmapped? It's a hole - nothing to do */ 2823 if (!buffer_mapped(&map_bh)) 2824 goto unlock; 2825 2826 /* Ok, it's mapped. Make sure it's up-to-date */ 2827 if (!PageUptodate(page)) { 2828 err = mapping->a_ops->readpage(NULL, page); 2829 if (err) { 2830 page_cache_release(page); 2831 goto out; 2832 } 2833 lock_page(page); 2834 if (!PageUptodate(page)) { 2835 err = -EIO; 2836 goto unlock; 2837 } 2838 if (page_has_buffers(page)) 2839 goto has_buffers; 2840 } 2841 zero_user(page, offset, length); 2842 set_page_dirty(page); 2843 err = 0; 2844 2845 unlock: 2846 unlock_page(page); 2847 page_cache_release(page); 2848 out: 2849 return err; 2850 } 2851 EXPORT_SYMBOL(nobh_truncate_page); 2852 2853 int block_truncate_page(struct address_space *mapping, 2854 loff_t from, get_block_t *get_block) 2855 { 2856 pgoff_t index = from >> PAGE_CACHE_SHIFT; 2857 unsigned offset = from & (PAGE_CACHE_SIZE-1); 2858 unsigned blocksize; 2859 sector_t iblock; 2860 unsigned length, pos; 2861 struct inode *inode = mapping->host; 2862 struct page *page; 2863 struct buffer_head *bh; 2864 int err; 2865 2866 blocksize = 1 << inode->i_blkbits; 2867 length = offset & (blocksize - 1); 2868 2869 /* Block boundary? Nothing to do */ 2870 if (!length) 2871 return 0; 2872 2873 length = blocksize - length; 2874 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits); 2875 2876 page = grab_cache_page(mapping, index); 2877 err = -ENOMEM; 2878 if (!page) 2879 goto out; 2880 2881 if (!page_has_buffers(page)) 2882 create_empty_buffers(page, blocksize, 0); 2883 2884 /* Find the buffer that contains "offset" */ 2885 bh = page_buffers(page); 2886 pos = blocksize; 2887 while (offset >= pos) { 2888 bh = bh->b_this_page; 2889 iblock++; 2890 pos += blocksize; 2891 } 2892 2893 err = 0; 2894 if (!buffer_mapped(bh)) { 2895 WARN_ON(bh->b_size != blocksize); 2896 err = get_block(inode, iblock, bh, 0); 2897 if (err) 2898 goto unlock; 2899 /* unmapped? It's a hole - nothing to do */ 2900 if (!buffer_mapped(bh)) 2901 goto unlock; 2902 } 2903 2904 /* Ok, it's mapped. Make sure it's up-to-date */ 2905 if (PageUptodate(page)) 2906 set_buffer_uptodate(bh); 2907 2908 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) { 2909 err = -EIO; 2910 ll_rw_block(READ, 1, &bh); 2911 wait_on_buffer(bh); 2912 /* Uhhuh. Read error. Complain and punt. */ 2913 if (!buffer_uptodate(bh)) 2914 goto unlock; 2915 } 2916 2917 zero_user(page, offset, length); 2918 mark_buffer_dirty(bh); 2919 err = 0; 2920 2921 unlock: 2922 unlock_page(page); 2923 page_cache_release(page); 2924 out: 2925 return err; 2926 } 2927 EXPORT_SYMBOL(block_truncate_page); 2928 2929 /* 2930 * The generic ->writepage function for buffer-backed address_spaces 2931 * this form passes in the end_io handler used to finish the IO. 2932 */ 2933 int block_write_full_page_endio(struct page *page, get_block_t *get_block, 2934 struct writeback_control *wbc, bh_end_io_t *handler) 2935 { 2936 struct inode * const inode = page->mapping->host; 2937 loff_t i_size = i_size_read(inode); 2938 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT; 2939 unsigned offset; 2940 2941 /* Is the page fully inside i_size? */ 2942 if (page->index < end_index) 2943 return __block_write_full_page(inode, page, get_block, wbc, 2944 handler); 2945 2946 /* Is the page fully outside i_size? (truncate in progress) */ 2947 offset = i_size & (PAGE_CACHE_SIZE-1); 2948 if (page->index >= end_index+1 || !offset) { 2949 /* 2950 * The page may have dirty, unmapped buffers. For example, 2951 * they may have been added in ext3_writepage(). Make them 2952 * freeable here, so the page does not leak. 2953 */ 2954 do_invalidatepage(page, 0); 2955 unlock_page(page); 2956 return 0; /* don't care */ 2957 } 2958 2959 /* 2960 * The page straddles i_size. It must be zeroed out on each and every 2961 * writepage invocation because it may be mmapped. "A file is mapped 2962 * in multiples of the page size. For a file that is not a multiple of 2963 * the page size, the remaining memory is zeroed when mapped, and 2964 * writes to that region are not written out to the file." 2965 */ 2966 zero_user_segment(page, offset, PAGE_CACHE_SIZE); 2967 return __block_write_full_page(inode, page, get_block, wbc, handler); 2968 } 2969 EXPORT_SYMBOL(block_write_full_page_endio); 2970 2971 /* 2972 * The generic ->writepage function for buffer-backed address_spaces 2973 */ 2974 int block_write_full_page(struct page *page, get_block_t *get_block, 2975 struct writeback_control *wbc) 2976 { 2977 return block_write_full_page_endio(page, get_block, wbc, 2978 end_buffer_async_write); 2979 } 2980 EXPORT_SYMBOL(block_write_full_page); 2981 2982 sector_t generic_block_bmap(struct address_space *mapping, sector_t block, 2983 get_block_t *get_block) 2984 { 2985 struct buffer_head tmp; 2986 struct inode *inode = mapping->host; 2987 tmp.b_state = 0; 2988 tmp.b_blocknr = 0; 2989 tmp.b_size = 1 << inode->i_blkbits; 2990 get_block(inode, block, &tmp, 0); 2991 return tmp.b_blocknr; 2992 } 2993 EXPORT_SYMBOL(generic_block_bmap); 2994 2995 static void end_bio_bh_io_sync(struct bio *bio, int err) 2996 { 2997 struct buffer_head *bh = bio->bi_private; 2998 2999 if (err == -EOPNOTSUPP) { 3000 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags); 3001 set_bit(BH_Eopnotsupp, &bh->b_state); 3002 } 3003 3004 if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags))) 3005 set_bit(BH_Quiet, &bh->b_state); 3006 3007 bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags)); 3008 bio_put(bio); 3009 } 3010 3011 int submit_bh(int rw, struct buffer_head * bh) 3012 { 3013 struct bio *bio; 3014 int ret = 0; 3015 3016 BUG_ON(!buffer_locked(bh)); 3017 BUG_ON(!buffer_mapped(bh)); 3018 BUG_ON(!bh->b_end_io); 3019 BUG_ON(buffer_delay(bh)); 3020 BUG_ON(buffer_unwritten(bh)); 3021 3022 /* 3023 * Mask in barrier bit for a write (could be either a WRITE or a 3024 * WRITE_SYNC 3025 */ 3026 if (buffer_ordered(bh) && (rw & WRITE)) 3027 rw |= WRITE_BARRIER; 3028 3029 /* 3030 * Only clear out a write error when rewriting 3031 */ 3032 if (test_set_buffer_req(bh) && (rw & WRITE)) 3033 clear_buffer_write_io_error(bh); 3034 3035 /* 3036 * from here on down, it's all bio -- do the initial mapping, 3037 * submit_bio -> generic_make_request may further map this bio around 3038 */ 3039 bio = bio_alloc(GFP_NOIO, 1); 3040 3041 bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9); 3042 bio->bi_bdev = bh->b_bdev; 3043 bio->bi_io_vec[0].bv_page = bh->b_page; 3044 bio->bi_io_vec[0].bv_len = bh->b_size; 3045 bio->bi_io_vec[0].bv_offset = bh_offset(bh); 3046 3047 bio->bi_vcnt = 1; 3048 bio->bi_idx = 0; 3049 bio->bi_size = bh->b_size; 3050 3051 bio->bi_end_io = end_bio_bh_io_sync; 3052 bio->bi_private = bh; 3053 3054 bio_get(bio); 3055 submit_bio(rw, bio); 3056 3057 if (bio_flagged(bio, BIO_EOPNOTSUPP)) 3058 ret = -EOPNOTSUPP; 3059 3060 bio_put(bio); 3061 return ret; 3062 } 3063 EXPORT_SYMBOL(submit_bh); 3064 3065 /** 3066 * ll_rw_block: low-level access to block devices (DEPRECATED) 3067 * @rw: whether to %READ or %WRITE or %SWRITE or maybe %READA (readahead) 3068 * @nr: number of &struct buffer_heads in the array 3069 * @bhs: array of pointers to &struct buffer_head 3070 * 3071 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and 3072 * requests an I/O operation on them, either a %READ or a %WRITE. The third 3073 * %SWRITE is like %WRITE only we make sure that the *current* data in buffers 3074 * are sent to disk. The fourth %READA option is described in the documentation 3075 * for generic_make_request() which ll_rw_block() calls. 3076 * 3077 * This function drops any buffer that it cannot get a lock on (with the 3078 * BH_Lock state bit) unless SWRITE is required, any buffer that appears to be 3079 * clean when doing a write request, and any buffer that appears to be 3080 * up-to-date when doing read request. Further it marks as clean buffers that 3081 * are processed for writing (the buffer cache won't assume that they are 3082 * actually clean until the buffer gets unlocked). 3083 * 3084 * ll_rw_block sets b_end_io to simple completion handler that marks 3085 * the buffer up-to-date (if approriate), unlocks the buffer and wakes 3086 * any waiters. 3087 * 3088 * All of the buffers must be for the same device, and must also be a 3089 * multiple of the current approved size for the device. 3090 */ 3091 void ll_rw_block(int rw, int nr, struct buffer_head *bhs[]) 3092 { 3093 int i; 3094 3095 for (i = 0; i < nr; i++) { 3096 struct buffer_head *bh = bhs[i]; 3097 3098 if (rw == SWRITE || rw == SWRITE_SYNC || rw == SWRITE_SYNC_PLUG) 3099 lock_buffer(bh); 3100 else if (!trylock_buffer(bh)) 3101 continue; 3102 3103 if (rw == WRITE || rw == SWRITE || rw == SWRITE_SYNC || 3104 rw == SWRITE_SYNC_PLUG) { 3105 if (test_clear_buffer_dirty(bh)) { 3106 bh->b_end_io = end_buffer_write_sync; 3107 get_bh(bh); 3108 if (rw == SWRITE_SYNC) 3109 submit_bh(WRITE_SYNC, bh); 3110 else 3111 submit_bh(WRITE, bh); 3112 continue; 3113 } 3114 } else { 3115 if (!buffer_uptodate(bh)) { 3116 bh->b_end_io = end_buffer_read_sync; 3117 get_bh(bh); 3118 submit_bh(rw, bh); 3119 continue; 3120 } 3121 } 3122 unlock_buffer(bh); 3123 } 3124 } 3125 EXPORT_SYMBOL(ll_rw_block); 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) 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(WRITE_SYNC, bh); 3142 wait_on_buffer(bh); 3143 if (buffer_eopnotsupp(bh)) { 3144 clear_buffer_eopnotsupp(bh); 3145 ret = -EOPNOTSUPP; 3146 } 3147 if (!ret && !buffer_uptodate(bh)) 3148 ret = -EIO; 3149 } else { 3150 unlock_buffer(bh); 3151 } 3152 return ret; 3153 } 3154 EXPORT_SYMBOL(sync_dirty_buffer); 3155 3156 /* 3157 * try_to_free_buffers() checks if all the buffers on this particular page 3158 * are unused, and releases them if so. 3159 * 3160 * Exclusion against try_to_free_buffers may be obtained by either 3161 * locking the page or by holding its mapping's private_lock. 3162 * 3163 * If the page is dirty but all the buffers are clean then we need to 3164 * be sure to mark the page clean as well. This is because the page 3165 * may be against a block device, and a later reattachment of buffers 3166 * to a dirty page will set *all* buffers dirty. Which would corrupt 3167 * filesystem data on the same device. 3168 * 3169 * The same applies to regular filesystem pages: if all the buffers are 3170 * clean then we set the page clean and proceed. To do that, we require 3171 * total exclusion from __set_page_dirty_buffers(). That is obtained with 3172 * private_lock. 3173 * 3174 * try_to_free_buffers() is non-blocking. 3175 */ 3176 static inline int buffer_busy(struct buffer_head *bh) 3177 { 3178 return atomic_read(&bh->b_count) | 3179 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock))); 3180 } 3181 3182 static int 3183 drop_buffers(struct page *page, struct buffer_head **buffers_to_free) 3184 { 3185 struct buffer_head *head = page_buffers(page); 3186 struct buffer_head *bh; 3187 3188 bh = head; 3189 do { 3190 if (buffer_write_io_error(bh) && page->mapping) 3191 set_bit(AS_EIO, &page->mapping->flags); 3192 if (buffer_busy(bh)) 3193 goto failed; 3194 bh = bh->b_this_page; 3195 } while (bh != head); 3196 3197 do { 3198 struct buffer_head *next = bh->b_this_page; 3199 3200 if (bh->b_assoc_map) 3201 __remove_assoc_queue(bh); 3202 bh = next; 3203 } while (bh != head); 3204 *buffers_to_free = head; 3205 __clear_page_buffers(page); 3206 return 1; 3207 failed: 3208 return 0; 3209 } 3210 3211 int try_to_free_buffers(struct page *page) 3212 { 3213 struct address_space * const mapping = page->mapping; 3214 struct buffer_head *buffers_to_free = NULL; 3215 int ret = 0; 3216 3217 BUG_ON(!PageLocked(page)); 3218 if (PageWriteback(page)) 3219 return 0; 3220 3221 if (mapping == NULL) { /* can this still happen? */ 3222 ret = drop_buffers(page, &buffers_to_free); 3223 goto out; 3224 } 3225 3226 spin_lock(&mapping->private_lock); 3227 ret = drop_buffers(page, &buffers_to_free); 3228 3229 /* 3230 * If the filesystem writes its buffers by hand (eg ext3) 3231 * then we can have clean buffers against a dirty page. We 3232 * clean the page here; otherwise the VM will never notice 3233 * that the filesystem did any IO at all. 3234 * 3235 * Also, during truncate, discard_buffer will have marked all 3236 * the page's buffers clean. We discover that here and clean 3237 * the page also. 3238 * 3239 * private_lock must be held over this entire operation in order 3240 * to synchronise against __set_page_dirty_buffers and prevent the 3241 * dirty bit from being lost. 3242 */ 3243 if (ret) 3244 cancel_dirty_page(page, PAGE_CACHE_SIZE); 3245 spin_unlock(&mapping->private_lock); 3246 out: 3247 if (buffers_to_free) { 3248 struct buffer_head *bh = buffers_to_free; 3249 3250 do { 3251 struct buffer_head *next = bh->b_this_page; 3252 free_buffer_head(bh); 3253 bh = next; 3254 } while (bh != buffers_to_free); 3255 } 3256 return ret; 3257 } 3258 EXPORT_SYMBOL(try_to_free_buffers); 3259 3260 void block_sync_page(struct page *page) 3261 { 3262 struct address_space *mapping; 3263 3264 smp_mb(); 3265 mapping = page_mapping(page); 3266 if (mapping) 3267 blk_run_backing_dev(mapping->backing_dev_info, page); 3268 } 3269 EXPORT_SYMBOL(block_sync_page); 3270 3271 /* 3272 * There are no bdflush tunables left. But distributions are 3273 * still running obsolete flush daemons, so we terminate them here. 3274 * 3275 * Use of bdflush() is deprecated and will be removed in a future kernel. 3276 * The `flush-X' kernel threads fully replace bdflush daemons and this call. 3277 */ 3278 SYSCALL_DEFINE2(bdflush, int, func, long, data) 3279 { 3280 static int msg_count; 3281 3282 if (!capable(CAP_SYS_ADMIN)) 3283 return -EPERM; 3284 3285 if (msg_count < 5) { 3286 msg_count++; 3287 printk(KERN_INFO 3288 "warning: process `%s' used the obsolete bdflush" 3289 " system call\n", current->comm); 3290 printk(KERN_INFO "Fix your initscripts?\n"); 3291 } 3292 3293 if (func == 1) 3294 do_exit(0); 3295 return 0; 3296 } 3297 3298 /* 3299 * Buffer-head allocation 3300 */ 3301 static struct kmem_cache *bh_cachep; 3302 3303 /* 3304 * Once the number of bh's in the machine exceeds this level, we start 3305 * stripping them in writeback. 3306 */ 3307 static int max_buffer_heads; 3308 3309 int buffer_heads_over_limit; 3310 3311 struct bh_accounting { 3312 int nr; /* Number of live bh's */ 3313 int ratelimit; /* Limit cacheline bouncing */ 3314 }; 3315 3316 static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0}; 3317 3318 static void recalc_bh_state(void) 3319 { 3320 int i; 3321 int tot = 0; 3322 3323 if (__get_cpu_var(bh_accounting).ratelimit++ < 4096) 3324 return; 3325 __get_cpu_var(bh_accounting).ratelimit = 0; 3326 for_each_online_cpu(i) 3327 tot += per_cpu(bh_accounting, i).nr; 3328 buffer_heads_over_limit = (tot > max_buffer_heads); 3329 } 3330 3331 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags) 3332 { 3333 struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags); 3334 if (ret) { 3335 INIT_LIST_HEAD(&ret->b_assoc_buffers); 3336 get_cpu_var(bh_accounting).nr++; 3337 recalc_bh_state(); 3338 put_cpu_var(bh_accounting); 3339 } 3340 return ret; 3341 } 3342 EXPORT_SYMBOL(alloc_buffer_head); 3343 3344 void free_buffer_head(struct buffer_head *bh) 3345 { 3346 BUG_ON(!list_empty(&bh->b_assoc_buffers)); 3347 kmem_cache_free(bh_cachep, bh); 3348 get_cpu_var(bh_accounting).nr--; 3349 recalc_bh_state(); 3350 put_cpu_var(bh_accounting); 3351 } 3352 EXPORT_SYMBOL(free_buffer_head); 3353 3354 static void buffer_exit_cpu(int cpu) 3355 { 3356 int i; 3357 struct bh_lru *b = &per_cpu(bh_lrus, cpu); 3358 3359 for (i = 0; i < BH_LRU_SIZE; i++) { 3360 brelse(b->bhs[i]); 3361 b->bhs[i] = NULL; 3362 } 3363 get_cpu_var(bh_accounting).nr += per_cpu(bh_accounting, cpu).nr; 3364 per_cpu(bh_accounting, cpu).nr = 0; 3365 put_cpu_var(bh_accounting); 3366 } 3367 3368 static int buffer_cpu_notify(struct notifier_block *self, 3369 unsigned long action, void *hcpu) 3370 { 3371 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) 3372 buffer_exit_cpu((unsigned long)hcpu); 3373 return NOTIFY_OK; 3374 } 3375 3376 /** 3377 * bh_uptodate_or_lock - Test whether the buffer is uptodate 3378 * @bh: struct buffer_head 3379 * 3380 * Return true if the buffer is up-to-date and false, 3381 * with the buffer locked, if not. 3382 */ 3383 int bh_uptodate_or_lock(struct buffer_head *bh) 3384 { 3385 if (!buffer_uptodate(bh)) { 3386 lock_buffer(bh); 3387 if (!buffer_uptodate(bh)) 3388 return 0; 3389 unlock_buffer(bh); 3390 } 3391 return 1; 3392 } 3393 EXPORT_SYMBOL(bh_uptodate_or_lock); 3394 3395 /** 3396 * bh_submit_read - Submit a locked buffer for reading 3397 * @bh: struct buffer_head 3398 * 3399 * Returns zero on success and -EIO on error. 3400 */ 3401 int bh_submit_read(struct buffer_head *bh) 3402 { 3403 BUG_ON(!buffer_locked(bh)); 3404 3405 if (buffer_uptodate(bh)) { 3406 unlock_buffer(bh); 3407 return 0; 3408 } 3409 3410 get_bh(bh); 3411 bh->b_end_io = end_buffer_read_sync; 3412 submit_bh(READ, bh); 3413 wait_on_buffer(bh); 3414 if (buffer_uptodate(bh)) 3415 return 0; 3416 return -EIO; 3417 } 3418 EXPORT_SYMBOL(bh_submit_read); 3419 3420 void __init buffer_init(void) 3421 { 3422 int nrpages; 3423 3424 bh_cachep = kmem_cache_create("buffer_head", 3425 sizeof(struct buffer_head), 0, 3426 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC| 3427 SLAB_MEM_SPREAD), 3428 NULL); 3429 3430 /* 3431 * Limit the bh occupancy to 10% of ZONE_NORMAL 3432 */ 3433 nrpages = (nr_free_buffer_pages() * 10) / 100; 3434 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head)); 3435 hotcpu_notifier(buffer_cpu_notify, 0); 3436 } 3437