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