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 fastcall __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 fastcall unlock_buffer(struct buffer_head *bh) 78 { 79 smp_mb__before_clear_bit(); 80 clear_buffer_locked(bh); 81 smp_mb__after_clear_bit(); 82 wake_up_bit(&bh->b_state, BH_Lock); 83 } 84 85 /* 86 * Block until a buffer comes unlocked. This doesn't stop it 87 * from becoming locked again - you have to lock it yourself 88 * if you want to preserve its state. 89 */ 90 void __wait_on_buffer(struct buffer_head * bh) 91 { 92 wait_on_bit(&bh->b_state, BH_Lock, sync_buffer, TASK_UNINTERRUPTIBLE); 93 } 94 95 static void 96 __clear_page_buffers(struct page *page) 97 { 98 ClearPagePrivate(page); 99 set_page_private(page, 0); 100 page_cache_release(page); 101 } 102 103 static void buffer_io_error(struct buffer_head *bh) 104 { 105 char b[BDEVNAME_SIZE]; 106 107 printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n", 108 bdevname(bh->b_bdev, b), 109 (unsigned long long)bh->b_blocknr); 110 } 111 112 /* 113 * End-of-IO handler helper function which does not touch the bh after 114 * unlocking it. 115 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but 116 * a race there is benign: unlock_buffer() only use the bh's address for 117 * hashing after unlocking the buffer, so it doesn't actually touch the bh 118 * itself. 119 */ 120 static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate) 121 { 122 if (uptodate) { 123 set_buffer_uptodate(bh); 124 } else { 125 /* This happens, due to failed READA attempts. */ 126 clear_buffer_uptodate(bh); 127 } 128 unlock_buffer(bh); 129 } 130 131 /* 132 * Default synchronous end-of-IO handler.. Just mark it up-to-date and 133 * unlock the buffer. This is what ll_rw_block uses too. 134 */ 135 void end_buffer_read_sync(struct buffer_head *bh, int uptodate) 136 { 137 __end_buffer_read_notouch(bh, uptodate); 138 put_bh(bh); 139 } 140 141 void end_buffer_write_sync(struct buffer_head *bh, int uptodate) 142 { 143 char b[BDEVNAME_SIZE]; 144 145 if (uptodate) { 146 set_buffer_uptodate(bh); 147 } else { 148 if (!buffer_eopnotsupp(bh) && printk_ratelimit()) { 149 buffer_io_error(bh); 150 printk(KERN_WARNING "lost page write due to " 151 "I/O error on %s\n", 152 bdevname(bh->b_bdev, b)); 153 } 154 set_buffer_write_io_error(bh); 155 clear_buffer_uptodate(bh); 156 } 157 unlock_buffer(bh); 158 put_bh(bh); 159 } 160 161 /* 162 * Write out and wait upon all the dirty data associated with a block 163 * device via its mapping. Does not take the superblock lock. 164 */ 165 int sync_blockdev(struct block_device *bdev) 166 { 167 int ret = 0; 168 169 if (bdev) 170 ret = filemap_write_and_wait(bdev->bd_inode->i_mapping); 171 return ret; 172 } 173 EXPORT_SYMBOL(sync_blockdev); 174 175 /* 176 * Write out and wait upon all dirty data associated with this 177 * device. Filesystem data as well as the underlying block 178 * device. Takes the superblock lock. 179 */ 180 int fsync_bdev(struct block_device *bdev) 181 { 182 struct super_block *sb = get_super(bdev); 183 if (sb) { 184 int res = fsync_super(sb); 185 drop_super(sb); 186 return res; 187 } 188 return sync_blockdev(bdev); 189 } 190 191 /** 192 * freeze_bdev -- lock a filesystem and force it into a consistent state 193 * @bdev: blockdevice to lock 194 * 195 * This takes the block device bd_mount_sem to make sure no new mounts 196 * happen on bdev until thaw_bdev() is called. 197 * If a superblock is found on this device, we take the s_umount semaphore 198 * on it to make sure nobody unmounts until the snapshot creation is done. 199 */ 200 struct super_block *freeze_bdev(struct block_device *bdev) 201 { 202 struct super_block *sb; 203 204 down(&bdev->bd_mount_sem); 205 sb = get_super(bdev); 206 if (sb && !(sb->s_flags & MS_RDONLY)) { 207 sb->s_frozen = SB_FREEZE_WRITE; 208 smp_wmb(); 209 210 __fsync_super(sb); 211 212 sb->s_frozen = SB_FREEZE_TRANS; 213 smp_wmb(); 214 215 sync_blockdev(sb->s_bdev); 216 217 if (sb->s_op->write_super_lockfs) 218 sb->s_op->write_super_lockfs(sb); 219 } 220 221 sync_blockdev(bdev); 222 return sb; /* thaw_bdev releases s->s_umount and bd_mount_sem */ 223 } 224 EXPORT_SYMBOL(freeze_bdev); 225 226 /** 227 * thaw_bdev -- unlock filesystem 228 * @bdev: blockdevice to unlock 229 * @sb: associated superblock 230 * 231 * Unlocks the filesystem and marks it writeable again after freeze_bdev(). 232 */ 233 void thaw_bdev(struct block_device *bdev, struct super_block *sb) 234 { 235 if (sb) { 236 BUG_ON(sb->s_bdev != bdev); 237 238 if (sb->s_op->unlockfs) 239 sb->s_op->unlockfs(sb); 240 sb->s_frozen = SB_UNFROZEN; 241 smp_wmb(); 242 wake_up(&sb->s_wait_unfrozen); 243 drop_super(sb); 244 } 245 246 up(&bdev->bd_mount_sem); 247 } 248 EXPORT_SYMBOL(thaw_bdev); 249 250 /* 251 * Various filesystems appear to want __find_get_block to be non-blocking. 252 * But it's the page lock which protects the buffers. To get around this, 253 * we get exclusion from try_to_free_buffers with the blockdev mapping's 254 * private_lock. 255 * 256 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention 257 * may be quite high. This code could TryLock the page, and if that 258 * succeeds, there is no need to take private_lock. (But if 259 * private_lock is contended then so is mapping->tree_lock). 260 */ 261 static struct buffer_head * 262 __find_get_block_slow(struct block_device *bdev, sector_t block) 263 { 264 struct inode *bd_inode = bdev->bd_inode; 265 struct address_space *bd_mapping = bd_inode->i_mapping; 266 struct buffer_head *ret = NULL; 267 pgoff_t index; 268 struct buffer_head *bh; 269 struct buffer_head *head; 270 struct page *page; 271 int all_mapped = 1; 272 273 index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits); 274 page = find_get_page(bd_mapping, index); 275 if (!page) 276 goto out; 277 278 spin_lock(&bd_mapping->private_lock); 279 if (!page_has_buffers(page)) 280 goto out_unlock; 281 head = page_buffers(page); 282 bh = head; 283 do { 284 if (bh->b_blocknr == block) { 285 ret = bh; 286 get_bh(bh); 287 goto out_unlock; 288 } 289 if (!buffer_mapped(bh)) 290 all_mapped = 0; 291 bh = bh->b_this_page; 292 } while (bh != head); 293 294 /* we might be here because some of the buffers on this page are 295 * not mapped. This is due to various races between 296 * file io on the block device and getblk. It gets dealt with 297 * elsewhere, don't buffer_error if we had some unmapped buffers 298 */ 299 if (all_mapped) { 300 printk("__find_get_block_slow() failed. " 301 "block=%llu, b_blocknr=%llu\n", 302 (unsigned long long)block, 303 (unsigned long long)bh->b_blocknr); 304 printk("b_state=0x%08lx, b_size=%zu\n", 305 bh->b_state, bh->b_size); 306 printk("device blocksize: %d\n", 1 << bd_inode->i_blkbits); 307 } 308 out_unlock: 309 spin_unlock(&bd_mapping->private_lock); 310 page_cache_release(page); 311 out: 312 return ret; 313 } 314 315 /* If invalidate_buffers() will trash dirty buffers, it means some kind 316 of fs corruption is going on. Trashing dirty data always imply losing 317 information that was supposed to be just stored on the physical layer 318 by the user. 319 320 Thus invalidate_buffers in general usage is not allwowed to trash 321 dirty buffers. For example ioctl(FLSBLKBUF) expects dirty data to 322 be preserved. These buffers are simply skipped. 323 324 We also skip buffers which are still in use. For example this can 325 happen if a userspace program is reading the block device. 326 327 NOTE: In the case where the user removed a removable-media-disk even if 328 there's still dirty data not synced on disk (due a bug in the device driver 329 or due an error of the user), by not destroying the dirty buffers we could 330 generate corruption also on the next media inserted, thus a parameter is 331 necessary to handle this case in the most safe way possible (trying 332 to not corrupt also the new disk inserted with the data belonging to 333 the old now corrupted disk). Also for the ramdisk the natural thing 334 to do in order to release the ramdisk memory is to destroy dirty buffers. 335 336 These are two special cases. Normal usage imply the device driver 337 to issue a sync on the device (without waiting I/O completion) and 338 then an invalidate_buffers call that doesn't trash dirty buffers. 339 340 For handling cache coherency with the blkdev pagecache the 'update' case 341 is been introduced. It is needed to re-read from disk any pinned 342 buffer. NOTE: re-reading from disk is destructive so we can do it only 343 when we assume nobody is changing the buffercache under our I/O and when 344 we think the disk contains more recent information than the buffercache. 345 The update == 1 pass marks the buffers we need to update, the update == 2 346 pass does the actual I/O. */ 347 void invalidate_bdev(struct block_device *bdev) 348 { 349 struct address_space *mapping = bdev->bd_inode->i_mapping; 350 351 if (mapping->nrpages == 0) 352 return; 353 354 invalidate_bh_lrus(); 355 invalidate_mapping_pages(mapping, 0, -1); 356 } 357 358 /* 359 * Kick pdflush then try to free up some ZONE_NORMAL memory. 360 */ 361 static void free_more_memory(void) 362 { 363 struct zone **zones; 364 pg_data_t *pgdat; 365 366 wakeup_pdflush(1024); 367 yield(); 368 369 for_each_online_pgdat(pgdat) { 370 zones = pgdat->node_zonelists[gfp_zone(GFP_NOFS)].zones; 371 if (*zones) 372 try_to_free_pages(zones, 0, GFP_NOFS); 373 } 374 } 375 376 /* 377 * I/O completion handler for block_read_full_page() - pages 378 * which come unlocked at the end of I/O. 379 */ 380 static void end_buffer_async_read(struct buffer_head *bh, int uptodate) 381 { 382 unsigned long flags; 383 struct buffer_head *first; 384 struct buffer_head *tmp; 385 struct page *page; 386 int page_uptodate = 1; 387 388 BUG_ON(!buffer_async_read(bh)); 389 390 page = bh->b_page; 391 if (uptodate) { 392 set_buffer_uptodate(bh); 393 } else { 394 clear_buffer_uptodate(bh); 395 if (printk_ratelimit()) 396 buffer_io_error(bh); 397 SetPageError(page); 398 } 399 400 /* 401 * Be _very_ careful from here on. Bad things can happen if 402 * two buffer heads end IO at almost the same time and both 403 * decide that the page is now completely done. 404 */ 405 first = page_buffers(page); 406 local_irq_save(flags); 407 bit_spin_lock(BH_Uptodate_Lock, &first->b_state); 408 clear_buffer_async_read(bh); 409 unlock_buffer(bh); 410 tmp = bh; 411 do { 412 if (!buffer_uptodate(tmp)) 413 page_uptodate = 0; 414 if (buffer_async_read(tmp)) { 415 BUG_ON(!buffer_locked(tmp)); 416 goto still_busy; 417 } 418 tmp = tmp->b_this_page; 419 } while (tmp != bh); 420 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); 421 local_irq_restore(flags); 422 423 /* 424 * If none of the buffers had errors and they are all 425 * uptodate then we can set the page uptodate. 426 */ 427 if (page_uptodate && !PageError(page)) 428 SetPageUptodate(page); 429 unlock_page(page); 430 return; 431 432 still_busy: 433 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); 434 local_irq_restore(flags); 435 return; 436 } 437 438 /* 439 * Completion handler for block_write_full_page() - pages which are unlocked 440 * during I/O, and which have PageWriteback cleared upon I/O completion. 441 */ 442 static void end_buffer_async_write(struct buffer_head *bh, int uptodate) 443 { 444 char b[BDEVNAME_SIZE]; 445 unsigned long flags; 446 struct buffer_head *first; 447 struct buffer_head *tmp; 448 struct page *page; 449 450 BUG_ON(!buffer_async_write(bh)); 451 452 page = bh->b_page; 453 if (uptodate) { 454 set_buffer_uptodate(bh); 455 } else { 456 if (printk_ratelimit()) { 457 buffer_io_error(bh); 458 printk(KERN_WARNING "lost page write due to " 459 "I/O error on %s\n", 460 bdevname(bh->b_bdev, b)); 461 } 462 set_bit(AS_EIO, &page->mapping->flags); 463 set_buffer_write_io_error(bh); 464 clear_buffer_uptodate(bh); 465 SetPageError(page); 466 } 467 468 first = page_buffers(page); 469 local_irq_save(flags); 470 bit_spin_lock(BH_Uptodate_Lock, &first->b_state); 471 472 clear_buffer_async_write(bh); 473 unlock_buffer(bh); 474 tmp = bh->b_this_page; 475 while (tmp != bh) { 476 if (buffer_async_write(tmp)) { 477 BUG_ON(!buffer_locked(tmp)); 478 goto still_busy; 479 } 480 tmp = tmp->b_this_page; 481 } 482 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); 483 local_irq_restore(flags); 484 end_page_writeback(page); 485 return; 486 487 still_busy: 488 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); 489 local_irq_restore(flags); 490 return; 491 } 492 493 /* 494 * If a page's buffers are under async readin (end_buffer_async_read 495 * completion) then there is a possibility that another thread of 496 * control could lock one of the buffers after it has completed 497 * but while some of the other buffers have not completed. This 498 * locked buffer would confuse end_buffer_async_read() into not unlocking 499 * the page. So the absence of BH_Async_Read tells end_buffer_async_read() 500 * that this buffer is not under async I/O. 501 * 502 * The page comes unlocked when it has no locked buffer_async buffers 503 * left. 504 * 505 * PageLocked prevents anyone starting new async I/O reads any of 506 * the buffers. 507 * 508 * PageWriteback is used to prevent simultaneous writeout of the same 509 * page. 510 * 511 * PageLocked prevents anyone from starting writeback of a page which is 512 * under read I/O (PageWriteback is only ever set against a locked page). 513 */ 514 static void mark_buffer_async_read(struct buffer_head *bh) 515 { 516 bh->b_end_io = end_buffer_async_read; 517 set_buffer_async_read(bh); 518 } 519 520 void mark_buffer_async_write(struct buffer_head *bh) 521 { 522 bh->b_end_io = end_buffer_async_write; 523 set_buffer_async_write(bh); 524 } 525 EXPORT_SYMBOL(mark_buffer_async_write); 526 527 528 /* 529 * fs/buffer.c contains helper functions for buffer-backed address space's 530 * fsync functions. A common requirement for buffer-based filesystems is 531 * that certain data from the backing blockdev needs to be written out for 532 * a successful fsync(). For example, ext2 indirect blocks need to be 533 * written back and waited upon before fsync() returns. 534 * 535 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(), 536 * inode_has_buffers() and invalidate_inode_buffers() are provided for the 537 * management of a list of dependent buffers at ->i_mapping->private_list. 538 * 539 * Locking is a little subtle: try_to_free_buffers() will remove buffers 540 * from their controlling inode's queue when they are being freed. But 541 * try_to_free_buffers() will be operating against the *blockdev* mapping 542 * at the time, not against the S_ISREG file which depends on those buffers. 543 * So the locking for private_list is via the private_lock in the address_space 544 * which backs the buffers. Which is different from the address_space 545 * against which the buffers are listed. So for a particular address_space, 546 * mapping->private_lock does *not* protect mapping->private_list! In fact, 547 * mapping->private_list will always be protected by the backing blockdev's 548 * ->private_lock. 549 * 550 * Which introduces a requirement: all buffers on an address_space's 551 * ->private_list must be from the same address_space: the blockdev's. 552 * 553 * address_spaces which do not place buffers at ->private_list via these 554 * utility functions are free to use private_lock and private_list for 555 * whatever they want. The only requirement is that list_empty(private_list) 556 * be true at clear_inode() time. 557 * 558 * FIXME: clear_inode should not call invalidate_inode_buffers(). The 559 * filesystems should do that. invalidate_inode_buffers() should just go 560 * BUG_ON(!list_empty). 561 * 562 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should 563 * take an address_space, not an inode. And it should be called 564 * mark_buffer_dirty_fsync() to clearly define why those buffers are being 565 * queued up. 566 * 567 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the 568 * list if it is already on a list. Because if the buffer is on a list, 569 * it *must* already be on the right one. If not, the filesystem is being 570 * silly. This will save a ton of locking. But first we have to ensure 571 * that buffers are taken *off* the old inode's list when they are freed 572 * (presumably in truncate). That requires careful auditing of all 573 * filesystems (do it inside bforget()). It could also be done by bringing 574 * b_inode back. 575 */ 576 577 /* 578 * The buffer's backing address_space's private_lock must be held 579 */ 580 static inline void __remove_assoc_queue(struct buffer_head *bh) 581 { 582 list_del_init(&bh->b_assoc_buffers); 583 WARN_ON(!bh->b_assoc_map); 584 if (buffer_write_io_error(bh)) 585 set_bit(AS_EIO, &bh->b_assoc_map->flags); 586 bh->b_assoc_map = NULL; 587 } 588 589 int inode_has_buffers(struct inode *inode) 590 { 591 return !list_empty(&inode->i_data.private_list); 592 } 593 594 /* 595 * osync is designed to support O_SYNC io. It waits synchronously for 596 * all already-submitted IO to complete, but does not queue any new 597 * writes to the disk. 598 * 599 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as 600 * you dirty the buffers, and then use osync_inode_buffers to wait for 601 * completion. Any other dirty buffers which are not yet queued for 602 * write will not be flushed to disk by the osync. 603 */ 604 static int osync_buffers_list(spinlock_t *lock, struct list_head *list) 605 { 606 struct buffer_head *bh; 607 struct list_head *p; 608 int err = 0; 609 610 spin_lock(lock); 611 repeat: 612 list_for_each_prev(p, list) { 613 bh = BH_ENTRY(p); 614 if (buffer_locked(bh)) { 615 get_bh(bh); 616 spin_unlock(lock); 617 wait_on_buffer(bh); 618 if (!buffer_uptodate(bh)) 619 err = -EIO; 620 brelse(bh); 621 spin_lock(lock); 622 goto repeat; 623 } 624 } 625 spin_unlock(lock); 626 return err; 627 } 628 629 /** 630 * sync_mapping_buffers - write out and wait upon a mapping's "associated" 631 * buffers 632 * @mapping: the mapping which wants those buffers written 633 * 634 * Starts I/O against the buffers at mapping->private_list, and waits upon 635 * that I/O. 636 * 637 * Basically, this is a convenience function for fsync(). 638 * @mapping is a file or directory which needs those buffers to be written for 639 * a successful fsync(). 640 */ 641 int sync_mapping_buffers(struct address_space *mapping) 642 { 643 struct address_space *buffer_mapping = mapping->assoc_mapping; 644 645 if (buffer_mapping == NULL || list_empty(&mapping->private_list)) 646 return 0; 647 648 return fsync_buffers_list(&buffer_mapping->private_lock, 649 &mapping->private_list); 650 } 651 EXPORT_SYMBOL(sync_mapping_buffers); 652 653 /* 654 * Called when we've recently written block `bblock', and it is known that 655 * `bblock' was for a buffer_boundary() buffer. This means that the block at 656 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's 657 * dirty, schedule it for IO. So that indirects merge nicely with their data. 658 */ 659 void write_boundary_block(struct block_device *bdev, 660 sector_t bblock, unsigned blocksize) 661 { 662 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize); 663 if (bh) { 664 if (buffer_dirty(bh)) 665 ll_rw_block(WRITE, 1, &bh); 666 put_bh(bh); 667 } 668 } 669 670 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode) 671 { 672 struct address_space *mapping = inode->i_mapping; 673 struct address_space *buffer_mapping = bh->b_page->mapping; 674 675 mark_buffer_dirty(bh); 676 if (!mapping->assoc_mapping) { 677 mapping->assoc_mapping = buffer_mapping; 678 } else { 679 BUG_ON(mapping->assoc_mapping != buffer_mapping); 680 } 681 if (list_empty(&bh->b_assoc_buffers)) { 682 spin_lock(&buffer_mapping->private_lock); 683 list_move_tail(&bh->b_assoc_buffers, 684 &mapping->private_list); 685 bh->b_assoc_map = mapping; 686 spin_unlock(&buffer_mapping->private_lock); 687 } 688 } 689 EXPORT_SYMBOL(mark_buffer_dirty_inode); 690 691 /* 692 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode 693 * dirty. 694 * 695 * If warn is true, then emit a warning if the page is not uptodate and has 696 * not been truncated. 697 */ 698 static int __set_page_dirty(struct page *page, 699 struct address_space *mapping, int warn) 700 { 701 if (unlikely(!mapping)) 702 return !TestSetPageDirty(page); 703 704 if (TestSetPageDirty(page)) 705 return 0; 706 707 write_lock_irq(&mapping->tree_lock); 708 if (page->mapping) { /* Race with truncate? */ 709 WARN_ON_ONCE(warn && !PageUptodate(page)); 710 711 if (mapping_cap_account_dirty(mapping)) { 712 __inc_zone_page_state(page, NR_FILE_DIRTY); 713 __inc_bdi_stat(mapping->backing_dev_info, 714 BDI_RECLAIMABLE); 715 task_io_account_write(PAGE_CACHE_SIZE); 716 } 717 radix_tree_tag_set(&mapping->page_tree, 718 page_index(page), PAGECACHE_TAG_DIRTY); 719 } 720 write_unlock_irq(&mapping->tree_lock); 721 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); 722 723 return 1; 724 } 725 726 /* 727 * Add a page to the dirty page list. 728 * 729 * It is a sad fact of life that this function is called from several places 730 * deeply under spinlocking. It may not sleep. 731 * 732 * If the page has buffers, the uptodate buffers are set dirty, to preserve 733 * dirty-state coherency between the page and the buffers. It the page does 734 * not have buffers then when they are later attached they will all be set 735 * dirty. 736 * 737 * The buffers are dirtied before the page is dirtied. There's a small race 738 * window in which a writepage caller may see the page cleanness but not the 739 * buffer dirtiness. That's fine. If this code were to set the page dirty 740 * before the buffers, a concurrent writepage caller could clear the page dirty 741 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean 742 * page on the dirty page list. 743 * 744 * We use private_lock to lock against try_to_free_buffers while using the 745 * page's buffer list. Also use this to protect against clean buffers being 746 * added to the page after it was set dirty. 747 * 748 * FIXME: may need to call ->reservepage here as well. That's rather up to the 749 * address_space though. 750 */ 751 int __set_page_dirty_buffers(struct page *page) 752 { 753 struct address_space *mapping = page_mapping(page); 754 755 if (unlikely(!mapping)) 756 return !TestSetPageDirty(page); 757 758 spin_lock(&mapping->private_lock); 759 if (page_has_buffers(page)) { 760 struct buffer_head *head = page_buffers(page); 761 struct buffer_head *bh = head; 762 763 do { 764 set_buffer_dirty(bh); 765 bh = bh->b_this_page; 766 } while (bh != head); 767 } 768 spin_unlock(&mapping->private_lock); 769 770 return __set_page_dirty(page, mapping, 1); 771 } 772 EXPORT_SYMBOL(__set_page_dirty_buffers); 773 774 /* 775 * Write out and wait upon a list of buffers. 776 * 777 * We have conflicting pressures: we want to make sure that all 778 * initially dirty buffers get waited on, but that any subsequently 779 * dirtied buffers don't. After all, we don't want fsync to last 780 * forever if somebody is actively writing to the file. 781 * 782 * Do this in two main stages: first we copy dirty buffers to a 783 * temporary inode list, queueing the writes as we go. Then we clean 784 * up, waiting for those writes to complete. 785 * 786 * During this second stage, any subsequent updates to the file may end 787 * up refiling the buffer on the original inode's dirty list again, so 788 * there is a chance we will end up with a buffer queued for write but 789 * not yet completed on that list. So, as a final cleanup we go through 790 * the osync code to catch these locked, dirty buffers without requeuing 791 * any newly dirty buffers for write. 792 */ 793 static int fsync_buffers_list(spinlock_t *lock, struct list_head *list) 794 { 795 struct buffer_head *bh; 796 struct list_head tmp; 797 int err = 0, err2; 798 799 INIT_LIST_HEAD(&tmp); 800 801 spin_lock(lock); 802 while (!list_empty(list)) { 803 bh = BH_ENTRY(list->next); 804 __remove_assoc_queue(bh); 805 if (buffer_dirty(bh) || buffer_locked(bh)) { 806 list_add(&bh->b_assoc_buffers, &tmp); 807 if (buffer_dirty(bh)) { 808 get_bh(bh); 809 spin_unlock(lock); 810 /* 811 * Ensure any pending I/O completes so that 812 * ll_rw_block() actually writes the current 813 * contents - it is a noop if I/O is still in 814 * flight on potentially older contents. 815 */ 816 ll_rw_block(SWRITE, 1, &bh); 817 brelse(bh); 818 spin_lock(lock); 819 } 820 } 821 } 822 823 while (!list_empty(&tmp)) { 824 bh = BH_ENTRY(tmp.prev); 825 list_del_init(&bh->b_assoc_buffers); 826 get_bh(bh); 827 spin_unlock(lock); 828 wait_on_buffer(bh); 829 if (!buffer_uptodate(bh)) 830 err = -EIO; 831 brelse(bh); 832 spin_lock(lock); 833 } 834 835 spin_unlock(lock); 836 err2 = osync_buffers_list(lock, list); 837 if (err) 838 return err; 839 else 840 return err2; 841 } 842 843 /* 844 * Invalidate any and all dirty buffers on a given inode. We are 845 * probably unmounting the fs, but that doesn't mean we have already 846 * done a sync(). Just drop the buffers from the inode list. 847 * 848 * NOTE: we take the inode's blockdev's mapping's private_lock. Which 849 * assumes that all the buffers are against the blockdev. Not true 850 * for reiserfs. 851 */ 852 void invalidate_inode_buffers(struct inode *inode) 853 { 854 if (inode_has_buffers(inode)) { 855 struct address_space *mapping = &inode->i_data; 856 struct list_head *list = &mapping->private_list; 857 struct address_space *buffer_mapping = mapping->assoc_mapping; 858 859 spin_lock(&buffer_mapping->private_lock); 860 while (!list_empty(list)) 861 __remove_assoc_queue(BH_ENTRY(list->next)); 862 spin_unlock(&buffer_mapping->private_lock); 863 } 864 } 865 866 /* 867 * Remove any clean buffers from the inode's buffer list. This is called 868 * when we're trying to free the inode itself. Those buffers can pin it. 869 * 870 * Returns true if all buffers were removed. 871 */ 872 int remove_inode_buffers(struct inode *inode) 873 { 874 int ret = 1; 875 876 if (inode_has_buffers(inode)) { 877 struct address_space *mapping = &inode->i_data; 878 struct list_head *list = &mapping->private_list; 879 struct address_space *buffer_mapping = mapping->assoc_mapping; 880 881 spin_lock(&buffer_mapping->private_lock); 882 while (!list_empty(list)) { 883 struct buffer_head *bh = BH_ENTRY(list->next); 884 if (buffer_dirty(bh)) { 885 ret = 0; 886 break; 887 } 888 __remove_assoc_queue(bh); 889 } 890 spin_unlock(&buffer_mapping->private_lock); 891 } 892 return ret; 893 } 894 895 /* 896 * Create the appropriate buffers when given a page for data area and 897 * the size of each buffer.. Use the bh->b_this_page linked list to 898 * follow the buffers created. Return NULL if unable to create more 899 * buffers. 900 * 901 * The retry flag is used to differentiate async IO (paging, swapping) 902 * which may not fail from ordinary buffer allocations. 903 */ 904 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, 905 int retry) 906 { 907 struct buffer_head *bh, *head; 908 long offset; 909 910 try_again: 911 head = NULL; 912 offset = PAGE_SIZE; 913 while ((offset -= size) >= 0) { 914 bh = alloc_buffer_head(GFP_NOFS); 915 if (!bh) 916 goto no_grow; 917 918 bh->b_bdev = NULL; 919 bh->b_this_page = head; 920 bh->b_blocknr = -1; 921 head = bh; 922 923 bh->b_state = 0; 924 atomic_set(&bh->b_count, 0); 925 bh->b_private = NULL; 926 bh->b_size = size; 927 928 /* Link the buffer to its page */ 929 set_bh_page(bh, page, offset); 930 931 init_buffer(bh, NULL, NULL); 932 } 933 return head; 934 /* 935 * In case anything failed, we just free everything we got. 936 */ 937 no_grow: 938 if (head) { 939 do { 940 bh = head; 941 head = head->b_this_page; 942 free_buffer_head(bh); 943 } while (head); 944 } 945 946 /* 947 * Return failure for non-async IO requests. Async IO requests 948 * are not allowed to fail, so we have to wait until buffer heads 949 * become available. But we don't want tasks sleeping with 950 * partially complete buffers, so all were released above. 951 */ 952 if (!retry) 953 return NULL; 954 955 /* We're _really_ low on memory. Now we just 956 * wait for old buffer heads to become free due to 957 * finishing IO. Since this is an async request and 958 * the reserve list is empty, we're sure there are 959 * async buffer heads in use. 960 */ 961 free_more_memory(); 962 goto try_again; 963 } 964 EXPORT_SYMBOL_GPL(alloc_page_buffers); 965 966 static inline void 967 link_dev_buffers(struct page *page, struct buffer_head *head) 968 { 969 struct buffer_head *bh, *tail; 970 971 bh = head; 972 do { 973 tail = bh; 974 bh = bh->b_this_page; 975 } while (bh); 976 tail->b_this_page = head; 977 attach_page_buffers(page, head); 978 } 979 980 /* 981 * Initialise the state of a blockdev page's buffers. 982 */ 983 static void 984 init_page_buffers(struct page *page, struct block_device *bdev, 985 sector_t block, int size) 986 { 987 struct buffer_head *head = page_buffers(page); 988 struct buffer_head *bh = head; 989 int uptodate = PageUptodate(page); 990 991 do { 992 if (!buffer_mapped(bh)) { 993 init_buffer(bh, NULL, NULL); 994 bh->b_bdev = bdev; 995 bh->b_blocknr = block; 996 if (uptodate) 997 set_buffer_uptodate(bh); 998 set_buffer_mapped(bh); 999 } 1000 block++; 1001 bh = bh->b_this_page; 1002 } while (bh != head); 1003 } 1004 1005 /* 1006 * Create the page-cache page that contains the requested block. 1007 * 1008 * This is user purely for blockdev mappings. 1009 */ 1010 static struct page * 1011 grow_dev_page(struct block_device *bdev, sector_t block, 1012 pgoff_t index, int size) 1013 { 1014 struct inode *inode = bdev->bd_inode; 1015 struct page *page; 1016 struct buffer_head *bh; 1017 1018 page = find_or_create_page(inode->i_mapping, index, 1019 (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE); 1020 if (!page) 1021 return NULL; 1022 1023 BUG_ON(!PageLocked(page)); 1024 1025 if (page_has_buffers(page)) { 1026 bh = page_buffers(page); 1027 if (bh->b_size == size) { 1028 init_page_buffers(page, bdev, block, size); 1029 return page; 1030 } 1031 if (!try_to_free_buffers(page)) 1032 goto failed; 1033 } 1034 1035 /* 1036 * Allocate some buffers for this page 1037 */ 1038 bh = alloc_page_buffers(page, size, 0); 1039 if (!bh) 1040 goto failed; 1041 1042 /* 1043 * Link the page to the buffers and initialise them. Take the 1044 * lock to be atomic wrt __find_get_block(), which does not 1045 * run under the page lock. 1046 */ 1047 spin_lock(&inode->i_mapping->private_lock); 1048 link_dev_buffers(page, bh); 1049 init_page_buffers(page, bdev, block, size); 1050 spin_unlock(&inode->i_mapping->private_lock); 1051 return page; 1052 1053 failed: 1054 BUG(); 1055 unlock_page(page); 1056 page_cache_release(page); 1057 return NULL; 1058 } 1059 1060 /* 1061 * Create buffers for the specified block device block's page. If 1062 * that page was dirty, the buffers are set dirty also. 1063 */ 1064 static int 1065 grow_buffers(struct block_device *bdev, sector_t block, int size) 1066 { 1067 struct page *page; 1068 pgoff_t index; 1069 int sizebits; 1070 1071 sizebits = -1; 1072 do { 1073 sizebits++; 1074 } while ((size << sizebits) < PAGE_SIZE); 1075 1076 index = block >> sizebits; 1077 1078 /* 1079 * Check for a block which wants to lie outside our maximum possible 1080 * pagecache index. (this comparison is done using sector_t types). 1081 */ 1082 if (unlikely(index != block >> sizebits)) { 1083 char b[BDEVNAME_SIZE]; 1084 1085 printk(KERN_ERR "%s: requested out-of-range block %llu for " 1086 "device %s\n", 1087 __FUNCTION__, (unsigned long long)block, 1088 bdevname(bdev, b)); 1089 return -EIO; 1090 } 1091 block = index << sizebits; 1092 /* Create a page with the proper size buffers.. */ 1093 page = grow_dev_page(bdev, block, index, size); 1094 if (!page) 1095 return 0; 1096 unlock_page(page); 1097 page_cache_release(page); 1098 return 1; 1099 } 1100 1101 static struct buffer_head * 1102 __getblk_slow(struct block_device *bdev, sector_t block, int size) 1103 { 1104 /* Size must be multiple of hard sectorsize */ 1105 if (unlikely(size & (bdev_hardsect_size(bdev)-1) || 1106 (size < 512 || size > PAGE_SIZE))) { 1107 printk(KERN_ERR "getblk(): invalid block size %d requested\n", 1108 size); 1109 printk(KERN_ERR "hardsect size: %d\n", 1110 bdev_hardsect_size(bdev)); 1111 1112 dump_stack(); 1113 return NULL; 1114 } 1115 1116 for (;;) { 1117 struct buffer_head * bh; 1118 int ret; 1119 1120 bh = __find_get_block(bdev, block, size); 1121 if (bh) 1122 return bh; 1123 1124 ret = grow_buffers(bdev, block, size); 1125 if (ret < 0) 1126 return NULL; 1127 if (ret == 0) 1128 free_more_memory(); 1129 } 1130 } 1131 1132 /* 1133 * The relationship between dirty buffers and dirty pages: 1134 * 1135 * Whenever a page has any dirty buffers, the page's dirty bit is set, and 1136 * the page is tagged dirty in its radix tree. 1137 * 1138 * At all times, the dirtiness of the buffers represents the dirtiness of 1139 * subsections of the page. If the page has buffers, the page dirty bit is 1140 * merely a hint about the true dirty state. 1141 * 1142 * When a page is set dirty in its entirety, all its buffers are marked dirty 1143 * (if the page has buffers). 1144 * 1145 * When a buffer is marked dirty, its page is dirtied, but the page's other 1146 * buffers are not. 1147 * 1148 * Also. When blockdev buffers are explicitly read with bread(), they 1149 * individually become uptodate. But their backing page remains not 1150 * uptodate - even if all of its buffers are uptodate. A subsequent 1151 * block_read_full_page() against that page will discover all the uptodate 1152 * buffers, will set the page uptodate and will perform no I/O. 1153 */ 1154 1155 /** 1156 * mark_buffer_dirty - mark a buffer_head as needing writeout 1157 * @bh: the buffer_head to mark dirty 1158 * 1159 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its 1160 * backing page dirty, then tag the page as dirty in its address_space's radix 1161 * tree and then attach the address_space's inode to its superblock's dirty 1162 * inode list. 1163 * 1164 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock, 1165 * mapping->tree_lock and the global inode_lock. 1166 */ 1167 void fastcall mark_buffer_dirty(struct buffer_head *bh) 1168 { 1169 WARN_ON_ONCE(!buffer_uptodate(bh)); 1170 if (!buffer_dirty(bh) && !test_set_buffer_dirty(bh)) 1171 __set_page_dirty(bh->b_page, page_mapping(bh->b_page), 0); 1172 } 1173 1174 /* 1175 * Decrement a buffer_head's reference count. If all buffers against a page 1176 * have zero reference count, are clean and unlocked, and if the page is clean 1177 * and unlocked then try_to_free_buffers() may strip the buffers from the page 1178 * in preparation for freeing it (sometimes, rarely, buffers are removed from 1179 * a page but it ends up not being freed, and buffers may later be reattached). 1180 */ 1181 void __brelse(struct buffer_head * buf) 1182 { 1183 if (atomic_read(&buf->b_count)) { 1184 put_bh(buf); 1185 return; 1186 } 1187 printk(KERN_ERR "VFS: brelse: Trying to free free buffer\n"); 1188 WARN_ON(1); 1189 } 1190 1191 /* 1192 * bforget() is like brelse(), except it discards any 1193 * potentially dirty data. 1194 */ 1195 void __bforget(struct buffer_head *bh) 1196 { 1197 clear_buffer_dirty(bh); 1198 if (!list_empty(&bh->b_assoc_buffers)) { 1199 struct address_space *buffer_mapping = bh->b_page->mapping; 1200 1201 spin_lock(&buffer_mapping->private_lock); 1202 list_del_init(&bh->b_assoc_buffers); 1203 bh->b_assoc_map = NULL; 1204 spin_unlock(&buffer_mapping->private_lock); 1205 } 1206 __brelse(bh); 1207 } 1208 1209 static struct buffer_head *__bread_slow(struct buffer_head *bh) 1210 { 1211 lock_buffer(bh); 1212 if (buffer_uptodate(bh)) { 1213 unlock_buffer(bh); 1214 return bh; 1215 } else { 1216 get_bh(bh); 1217 bh->b_end_io = end_buffer_read_sync; 1218 submit_bh(READ, bh); 1219 wait_on_buffer(bh); 1220 if (buffer_uptodate(bh)) 1221 return bh; 1222 } 1223 brelse(bh); 1224 return NULL; 1225 } 1226 1227 /* 1228 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block(). 1229 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their 1230 * refcount elevated by one when they're in an LRU. A buffer can only appear 1231 * once in a particular CPU's LRU. A single buffer can be present in multiple 1232 * CPU's LRUs at the same time. 1233 * 1234 * This is a transparent caching front-end to sb_bread(), sb_getblk() and 1235 * sb_find_get_block(). 1236 * 1237 * The LRUs themselves only need locking against invalidate_bh_lrus. We use 1238 * a local interrupt disable for that. 1239 */ 1240 1241 #define BH_LRU_SIZE 8 1242 1243 struct bh_lru { 1244 struct buffer_head *bhs[BH_LRU_SIZE]; 1245 }; 1246 1247 static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }}; 1248 1249 #ifdef CONFIG_SMP 1250 #define bh_lru_lock() local_irq_disable() 1251 #define bh_lru_unlock() local_irq_enable() 1252 #else 1253 #define bh_lru_lock() preempt_disable() 1254 #define bh_lru_unlock() preempt_enable() 1255 #endif 1256 1257 static inline void check_irqs_on(void) 1258 { 1259 #ifdef irqs_disabled 1260 BUG_ON(irqs_disabled()); 1261 #endif 1262 } 1263 1264 /* 1265 * The LRU management algorithm is dopey-but-simple. Sorry. 1266 */ 1267 static void bh_lru_install(struct buffer_head *bh) 1268 { 1269 struct buffer_head *evictee = NULL; 1270 struct bh_lru *lru; 1271 1272 check_irqs_on(); 1273 bh_lru_lock(); 1274 lru = &__get_cpu_var(bh_lrus); 1275 if (lru->bhs[0] != bh) { 1276 struct buffer_head *bhs[BH_LRU_SIZE]; 1277 int in; 1278 int out = 0; 1279 1280 get_bh(bh); 1281 bhs[out++] = bh; 1282 for (in = 0; in < BH_LRU_SIZE; in++) { 1283 struct buffer_head *bh2 = lru->bhs[in]; 1284 1285 if (bh2 == bh) { 1286 __brelse(bh2); 1287 } else { 1288 if (out >= BH_LRU_SIZE) { 1289 BUG_ON(evictee != NULL); 1290 evictee = bh2; 1291 } else { 1292 bhs[out++] = bh2; 1293 } 1294 } 1295 } 1296 while (out < BH_LRU_SIZE) 1297 bhs[out++] = NULL; 1298 memcpy(lru->bhs, bhs, sizeof(bhs)); 1299 } 1300 bh_lru_unlock(); 1301 1302 if (evictee) 1303 __brelse(evictee); 1304 } 1305 1306 /* 1307 * Look up the bh in this cpu's LRU. If it's there, move it to the head. 1308 */ 1309 static struct buffer_head * 1310 lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size) 1311 { 1312 struct buffer_head *ret = NULL; 1313 struct bh_lru *lru; 1314 unsigned int i; 1315 1316 check_irqs_on(); 1317 bh_lru_lock(); 1318 lru = &__get_cpu_var(bh_lrus); 1319 for (i = 0; i < BH_LRU_SIZE; i++) { 1320 struct buffer_head *bh = lru->bhs[i]; 1321 1322 if (bh && bh->b_bdev == bdev && 1323 bh->b_blocknr == block && bh->b_size == size) { 1324 if (i) { 1325 while (i) { 1326 lru->bhs[i] = lru->bhs[i - 1]; 1327 i--; 1328 } 1329 lru->bhs[0] = bh; 1330 } 1331 get_bh(bh); 1332 ret = bh; 1333 break; 1334 } 1335 } 1336 bh_lru_unlock(); 1337 return ret; 1338 } 1339 1340 /* 1341 * Perform a pagecache lookup for the matching buffer. If it's there, refresh 1342 * it in the LRU and mark it as accessed. If it is not present then return 1343 * NULL 1344 */ 1345 struct buffer_head * 1346 __find_get_block(struct block_device *bdev, sector_t block, unsigned size) 1347 { 1348 struct buffer_head *bh = lookup_bh_lru(bdev, block, size); 1349 1350 if (bh == NULL) { 1351 bh = __find_get_block_slow(bdev, block); 1352 if (bh) 1353 bh_lru_install(bh); 1354 } 1355 if (bh) 1356 touch_buffer(bh); 1357 return bh; 1358 } 1359 EXPORT_SYMBOL(__find_get_block); 1360 1361 /* 1362 * __getblk will locate (and, if necessary, create) the buffer_head 1363 * which corresponds to the passed block_device, block and size. The 1364 * returned buffer has its reference count incremented. 1365 * 1366 * __getblk() cannot fail - it just keeps trying. If you pass it an 1367 * illegal block number, __getblk() will happily return a buffer_head 1368 * which represents the non-existent block. Very weird. 1369 * 1370 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers() 1371 * attempt is failing. FIXME, perhaps? 1372 */ 1373 struct buffer_head * 1374 __getblk(struct block_device *bdev, sector_t block, unsigned size) 1375 { 1376 struct buffer_head *bh = __find_get_block(bdev, block, size); 1377 1378 might_sleep(); 1379 if (bh == NULL) 1380 bh = __getblk_slow(bdev, block, size); 1381 return bh; 1382 } 1383 EXPORT_SYMBOL(__getblk); 1384 1385 /* 1386 * Do async read-ahead on a buffer.. 1387 */ 1388 void __breadahead(struct block_device *bdev, sector_t block, unsigned size) 1389 { 1390 struct buffer_head *bh = __getblk(bdev, block, size); 1391 if (likely(bh)) { 1392 ll_rw_block(READA, 1, &bh); 1393 brelse(bh); 1394 } 1395 } 1396 EXPORT_SYMBOL(__breadahead); 1397 1398 /** 1399 * __bread() - reads a specified block and returns the bh 1400 * @bdev: the block_device to read from 1401 * @block: number of block 1402 * @size: size (in bytes) to read 1403 * 1404 * Reads a specified block, and returns buffer head that contains it. 1405 * It returns NULL if the block was unreadable. 1406 */ 1407 struct buffer_head * 1408 __bread(struct block_device *bdev, sector_t block, unsigned size) 1409 { 1410 struct buffer_head *bh = __getblk(bdev, block, size); 1411 1412 if (likely(bh) && !buffer_uptodate(bh)) 1413 bh = __bread_slow(bh); 1414 return bh; 1415 } 1416 EXPORT_SYMBOL(__bread); 1417 1418 /* 1419 * invalidate_bh_lrus() is called rarely - but not only at unmount. 1420 * This doesn't race because it runs in each cpu either in irq 1421 * or with preempt disabled. 1422 */ 1423 static void invalidate_bh_lru(void *arg) 1424 { 1425 struct bh_lru *b = &get_cpu_var(bh_lrus); 1426 int i; 1427 1428 for (i = 0; i < BH_LRU_SIZE; i++) { 1429 brelse(b->bhs[i]); 1430 b->bhs[i] = NULL; 1431 } 1432 put_cpu_var(bh_lrus); 1433 } 1434 1435 void invalidate_bh_lrus(void) 1436 { 1437 on_each_cpu(invalidate_bh_lru, NULL, 1, 1); 1438 } 1439 1440 void set_bh_page(struct buffer_head *bh, 1441 struct page *page, unsigned long offset) 1442 { 1443 bh->b_page = page; 1444 BUG_ON(offset >= PAGE_SIZE); 1445 if (PageHighMem(page)) 1446 /* 1447 * This catches illegal uses and preserves the offset: 1448 */ 1449 bh->b_data = (char *)(0 + offset); 1450 else 1451 bh->b_data = page_address(page) + offset; 1452 } 1453 EXPORT_SYMBOL(set_bh_page); 1454 1455 /* 1456 * Called when truncating a buffer on a page completely. 1457 */ 1458 static void discard_buffer(struct buffer_head * bh) 1459 { 1460 lock_buffer(bh); 1461 clear_buffer_dirty(bh); 1462 bh->b_bdev = NULL; 1463 clear_buffer_mapped(bh); 1464 clear_buffer_req(bh); 1465 clear_buffer_new(bh); 1466 clear_buffer_delay(bh); 1467 clear_buffer_unwritten(bh); 1468 unlock_buffer(bh); 1469 } 1470 1471 /** 1472 * block_invalidatepage - invalidate part of all of a buffer-backed page 1473 * 1474 * @page: the page which is affected 1475 * @offset: the index of the truncation point 1476 * 1477 * block_invalidatepage() is called when all or part of the page has become 1478 * invalidatedby a truncate operation. 1479 * 1480 * block_invalidatepage() does not have to release all buffers, but it must 1481 * ensure that no dirty buffer is left outside @offset and that no I/O 1482 * is underway against any of the blocks which are outside the truncation 1483 * point. Because the caller is about to free (and possibly reuse) those 1484 * blocks on-disk. 1485 */ 1486 void block_invalidatepage(struct page *page, unsigned long offset) 1487 { 1488 struct buffer_head *head, *bh, *next; 1489 unsigned int curr_off = 0; 1490 1491 BUG_ON(!PageLocked(page)); 1492 if (!page_has_buffers(page)) 1493 goto out; 1494 1495 head = page_buffers(page); 1496 bh = head; 1497 do { 1498 unsigned int next_off = curr_off + bh->b_size; 1499 next = bh->b_this_page; 1500 1501 /* 1502 * is this block fully invalidated? 1503 */ 1504 if (offset <= curr_off) 1505 discard_buffer(bh); 1506 curr_off = next_off; 1507 bh = next; 1508 } while (bh != head); 1509 1510 /* 1511 * We release buffers only if the entire page is being invalidated. 1512 * The get_block cached value has been unconditionally invalidated, 1513 * so real IO is not possible anymore. 1514 */ 1515 if (offset == 0) 1516 try_to_release_page(page, 0); 1517 out: 1518 return; 1519 } 1520 EXPORT_SYMBOL(block_invalidatepage); 1521 1522 /* 1523 * We attach and possibly dirty the buffers atomically wrt 1524 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers 1525 * is already excluded via the page lock. 1526 */ 1527 void create_empty_buffers(struct page *page, 1528 unsigned long blocksize, unsigned long b_state) 1529 { 1530 struct buffer_head *bh, *head, *tail; 1531 1532 head = alloc_page_buffers(page, blocksize, 1); 1533 bh = head; 1534 do { 1535 bh->b_state |= b_state; 1536 tail = bh; 1537 bh = bh->b_this_page; 1538 } while (bh); 1539 tail->b_this_page = head; 1540 1541 spin_lock(&page->mapping->private_lock); 1542 if (PageUptodate(page) || PageDirty(page)) { 1543 bh = head; 1544 do { 1545 if (PageDirty(page)) 1546 set_buffer_dirty(bh); 1547 if (PageUptodate(page)) 1548 set_buffer_uptodate(bh); 1549 bh = bh->b_this_page; 1550 } while (bh != head); 1551 } 1552 attach_page_buffers(page, head); 1553 spin_unlock(&page->mapping->private_lock); 1554 } 1555 EXPORT_SYMBOL(create_empty_buffers); 1556 1557 /* 1558 * We are taking a block for data and we don't want any output from any 1559 * buffer-cache aliases starting from return from that function and 1560 * until the moment when something will explicitly mark the buffer 1561 * dirty (hopefully that will not happen until we will free that block ;-) 1562 * We don't even need to mark it not-uptodate - nobody can expect 1563 * anything from a newly allocated buffer anyway. We used to used 1564 * unmap_buffer() for such invalidation, but that was wrong. We definitely 1565 * don't want to mark the alias unmapped, for example - it would confuse 1566 * anyone who might pick it with bread() afterwards... 1567 * 1568 * Also.. Note that bforget() doesn't lock the buffer. So there can 1569 * be writeout I/O going on against recently-freed buffers. We don't 1570 * wait on that I/O in bforget() - it's more efficient to wait on the I/O 1571 * only if we really need to. That happens here. 1572 */ 1573 void unmap_underlying_metadata(struct block_device *bdev, sector_t block) 1574 { 1575 struct buffer_head *old_bh; 1576 1577 might_sleep(); 1578 1579 old_bh = __find_get_block_slow(bdev, block); 1580 if (old_bh) { 1581 clear_buffer_dirty(old_bh); 1582 wait_on_buffer(old_bh); 1583 clear_buffer_req(old_bh); 1584 __brelse(old_bh); 1585 } 1586 } 1587 EXPORT_SYMBOL(unmap_underlying_metadata); 1588 1589 /* 1590 * NOTE! All mapped/uptodate combinations are valid: 1591 * 1592 * Mapped Uptodate Meaning 1593 * 1594 * No No "unknown" - must do get_block() 1595 * No Yes "hole" - zero-filled 1596 * Yes No "allocated" - allocated on disk, not read in 1597 * Yes Yes "valid" - allocated and up-to-date in memory. 1598 * 1599 * "Dirty" is valid only with the last case (mapped+uptodate). 1600 */ 1601 1602 /* 1603 * While block_write_full_page is writing back the dirty buffers under 1604 * the page lock, whoever dirtied the buffers may decide to clean them 1605 * again at any time. We handle that by only looking at the buffer 1606 * state inside lock_buffer(). 1607 * 1608 * If block_write_full_page() is called for regular writeback 1609 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a 1610 * locked buffer. This only can happen if someone has written the buffer 1611 * directly, with submit_bh(). At the address_space level PageWriteback 1612 * prevents this contention from occurring. 1613 */ 1614 static int __block_write_full_page(struct inode *inode, struct page *page, 1615 get_block_t *get_block, struct writeback_control *wbc) 1616 { 1617 int err; 1618 sector_t block; 1619 sector_t last_block; 1620 struct buffer_head *bh, *head; 1621 const unsigned blocksize = 1 << inode->i_blkbits; 1622 int nr_underway = 0; 1623 1624 BUG_ON(!PageLocked(page)); 1625 1626 last_block = (i_size_read(inode) - 1) >> inode->i_blkbits; 1627 1628 if (!page_has_buffers(page)) { 1629 create_empty_buffers(page, blocksize, 1630 (1 << BH_Dirty)|(1 << BH_Uptodate)); 1631 } 1632 1633 /* 1634 * Be very careful. We have no exclusion from __set_page_dirty_buffers 1635 * here, and the (potentially unmapped) buffers may become dirty at 1636 * any time. If a buffer becomes dirty here after we've inspected it 1637 * then we just miss that fact, and the page stays dirty. 1638 * 1639 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers; 1640 * handle that here by just cleaning them. 1641 */ 1642 1643 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits); 1644 head = page_buffers(page); 1645 bh = head; 1646 1647 /* 1648 * Get all the dirty buffers mapped to disk addresses and 1649 * handle any aliases from the underlying blockdev's mapping. 1650 */ 1651 do { 1652 if (block > last_block) { 1653 /* 1654 * mapped buffers outside i_size will occur, because 1655 * this page can be outside i_size when there is a 1656 * truncate in progress. 1657 */ 1658 /* 1659 * The buffer was zeroed by block_write_full_page() 1660 */ 1661 clear_buffer_dirty(bh); 1662 set_buffer_uptodate(bh); 1663 } else if (!buffer_mapped(bh) && buffer_dirty(bh)) { 1664 WARN_ON(bh->b_size != blocksize); 1665 err = get_block(inode, block, bh, 1); 1666 if (err) 1667 goto recover; 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 (test_set_buffer_locked(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, 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 lock_buffer(bh); 1748 mark_buffer_async_write(bh); 1749 } else { 1750 /* 1751 * The buffer may have been set dirty during 1752 * attachment to a dirty page. 1753 */ 1754 clear_buffer_dirty(bh); 1755 } 1756 } while ((bh = bh->b_this_page) != head); 1757 SetPageError(page); 1758 BUG_ON(PageWriteback(page)); 1759 mapping_set_error(page->mapping, err); 1760 set_page_writeback(page); 1761 do { 1762 struct buffer_head *next = bh->b_this_page; 1763 if (buffer_async_write(bh)) { 1764 clear_buffer_dirty(bh); 1765 submit_bh(WRITE, bh); 1766 nr_underway++; 1767 } 1768 bh = next; 1769 } while (bh != head); 1770 unlock_page(page); 1771 goto done; 1772 } 1773 1774 /* 1775 * If a page has any new buffers, zero them out here, and mark them uptodate 1776 * and dirty so they'll be written out (in order to prevent uninitialised 1777 * block data from leaking). And clear the new bit. 1778 */ 1779 void page_zero_new_buffers(struct page *page, unsigned from, unsigned to) 1780 { 1781 unsigned int block_start, block_end; 1782 struct buffer_head *head, *bh; 1783 1784 BUG_ON(!PageLocked(page)); 1785 if (!page_has_buffers(page)) 1786 return; 1787 1788 bh = head = page_buffers(page); 1789 block_start = 0; 1790 do { 1791 block_end = block_start + bh->b_size; 1792 1793 if (buffer_new(bh)) { 1794 if (block_end > from && block_start < to) { 1795 if (!PageUptodate(page)) { 1796 unsigned start, size; 1797 1798 start = max(from, block_start); 1799 size = min(to, block_end) - start; 1800 1801 zero_user_page(page, start, size, KM_USER0); 1802 set_buffer_uptodate(bh); 1803 } 1804 1805 clear_buffer_new(bh); 1806 mark_buffer_dirty(bh); 1807 } 1808 } 1809 1810 block_start = block_end; 1811 bh = bh->b_this_page; 1812 } while (bh != head); 1813 } 1814 EXPORT_SYMBOL(page_zero_new_buffers); 1815 1816 static int __block_prepare_write(struct inode *inode, struct page *page, 1817 unsigned from, unsigned to, get_block_t *get_block) 1818 { 1819 unsigned block_start, block_end; 1820 sector_t block; 1821 int err = 0; 1822 unsigned blocksize, bbits; 1823 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait; 1824 1825 BUG_ON(!PageLocked(page)); 1826 BUG_ON(from > PAGE_CACHE_SIZE); 1827 BUG_ON(to > PAGE_CACHE_SIZE); 1828 BUG_ON(from > to); 1829 1830 blocksize = 1 << inode->i_blkbits; 1831 if (!page_has_buffers(page)) 1832 create_empty_buffers(page, blocksize, 0); 1833 head = page_buffers(page); 1834 1835 bbits = inode->i_blkbits; 1836 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits); 1837 1838 for(bh = head, block_start = 0; bh != head || !block_start; 1839 block++, block_start=block_end, bh = bh->b_this_page) { 1840 block_end = block_start + blocksize; 1841 if (block_end <= from || block_start >= to) { 1842 if (PageUptodate(page)) { 1843 if (!buffer_uptodate(bh)) 1844 set_buffer_uptodate(bh); 1845 } 1846 continue; 1847 } 1848 if (buffer_new(bh)) 1849 clear_buffer_new(bh); 1850 if (!buffer_mapped(bh)) { 1851 WARN_ON(bh->b_size != blocksize); 1852 err = get_block(inode, block, bh, 1); 1853 if (err) 1854 break; 1855 if (buffer_new(bh)) { 1856 unmap_underlying_metadata(bh->b_bdev, 1857 bh->b_blocknr); 1858 if (PageUptodate(page)) { 1859 clear_buffer_new(bh); 1860 set_buffer_uptodate(bh); 1861 mark_buffer_dirty(bh); 1862 continue; 1863 } 1864 if (block_end > to || block_start < from) { 1865 void *kaddr; 1866 1867 kaddr = kmap_atomic(page, KM_USER0); 1868 if (block_end > to) 1869 memset(kaddr+to, 0, 1870 block_end-to); 1871 if (block_start < from) 1872 memset(kaddr+block_start, 1873 0, from-block_start); 1874 flush_dcache_page(page); 1875 kunmap_atomic(kaddr, KM_USER0); 1876 } 1877 continue; 1878 } 1879 } 1880 if (PageUptodate(page)) { 1881 if (!buffer_uptodate(bh)) 1882 set_buffer_uptodate(bh); 1883 continue; 1884 } 1885 if (!buffer_uptodate(bh) && !buffer_delay(bh) && 1886 !buffer_unwritten(bh) && 1887 (block_start < from || block_end > to)) { 1888 ll_rw_block(READ, 1, &bh); 1889 *wait_bh++=bh; 1890 } 1891 } 1892 /* 1893 * If we issued read requests - let them complete. 1894 */ 1895 while(wait_bh > wait) { 1896 wait_on_buffer(*--wait_bh); 1897 if (!buffer_uptodate(*wait_bh)) 1898 err = -EIO; 1899 } 1900 if (unlikely(err)) 1901 page_zero_new_buffers(page, from, to); 1902 return err; 1903 } 1904 1905 static int __block_commit_write(struct inode *inode, struct page *page, 1906 unsigned from, unsigned to) 1907 { 1908 unsigned block_start, block_end; 1909 int partial = 0; 1910 unsigned blocksize; 1911 struct buffer_head *bh, *head; 1912 1913 blocksize = 1 << inode->i_blkbits; 1914 1915 for(bh = head = page_buffers(page), block_start = 0; 1916 bh != head || !block_start; 1917 block_start=block_end, bh = bh->b_this_page) { 1918 block_end = block_start + blocksize; 1919 if (block_end <= from || block_start >= to) { 1920 if (!buffer_uptodate(bh)) 1921 partial = 1; 1922 } else { 1923 set_buffer_uptodate(bh); 1924 mark_buffer_dirty(bh); 1925 } 1926 clear_buffer_new(bh); 1927 } 1928 1929 /* 1930 * If this is a partial write which happened to make all buffers 1931 * uptodate then we can optimize away a bogus readpage() for 1932 * the next read(). Here we 'discover' whether the page went 1933 * uptodate as a result of this (potentially partial) write. 1934 */ 1935 if (!partial) 1936 SetPageUptodate(page); 1937 return 0; 1938 } 1939 1940 /* 1941 * block_write_begin takes care of the basic task of block allocation and 1942 * bringing partial write blocks uptodate first. 1943 * 1944 * If *pagep is not NULL, then block_write_begin uses the locked page 1945 * at *pagep rather than allocating its own. In this case, the page will 1946 * not be unlocked or deallocated on failure. 1947 */ 1948 int block_write_begin(struct file *file, struct address_space *mapping, 1949 loff_t pos, unsigned len, unsigned flags, 1950 struct page **pagep, void **fsdata, 1951 get_block_t *get_block) 1952 { 1953 struct inode *inode = mapping->host; 1954 int status = 0; 1955 struct page *page; 1956 pgoff_t index; 1957 unsigned start, end; 1958 int ownpage = 0; 1959 1960 index = pos >> PAGE_CACHE_SHIFT; 1961 start = pos & (PAGE_CACHE_SIZE - 1); 1962 end = start + len; 1963 1964 page = *pagep; 1965 if (page == NULL) { 1966 ownpage = 1; 1967 page = __grab_cache_page(mapping, index); 1968 if (!page) { 1969 status = -ENOMEM; 1970 goto out; 1971 } 1972 *pagep = page; 1973 } else 1974 BUG_ON(!PageLocked(page)); 1975 1976 status = __block_prepare_write(inode, page, start, end, get_block); 1977 if (unlikely(status)) { 1978 ClearPageUptodate(page); 1979 1980 if (ownpage) { 1981 unlock_page(page); 1982 page_cache_release(page); 1983 *pagep = NULL; 1984 1985 /* 1986 * prepare_write() may have instantiated a few blocks 1987 * outside i_size. Trim these off again. Don't need 1988 * i_size_read because we hold i_mutex. 1989 */ 1990 if (pos + len > inode->i_size) 1991 vmtruncate(inode, inode->i_size); 1992 } 1993 goto out; 1994 } 1995 1996 out: 1997 return status; 1998 } 1999 EXPORT_SYMBOL(block_write_begin); 2000 2001 int block_write_end(struct file *file, struct address_space *mapping, 2002 loff_t pos, unsigned len, unsigned copied, 2003 struct page *page, void *fsdata) 2004 { 2005 struct inode *inode = mapping->host; 2006 unsigned start; 2007 2008 start = pos & (PAGE_CACHE_SIZE - 1); 2009 2010 if (unlikely(copied < len)) { 2011 /* 2012 * The buffers that were written will now be uptodate, so we 2013 * don't have to worry about a readpage reading them and 2014 * overwriting a partial write. However if we have encountered 2015 * a short write and only partially written into a buffer, it 2016 * will not be marked uptodate, so a readpage might come in and 2017 * destroy our partial write. 2018 * 2019 * Do the simplest thing, and just treat any short write to a 2020 * non uptodate page as a zero-length write, and force the 2021 * caller to redo the whole thing. 2022 */ 2023 if (!PageUptodate(page)) 2024 copied = 0; 2025 2026 page_zero_new_buffers(page, start+copied, start+len); 2027 } 2028 flush_dcache_page(page); 2029 2030 /* This could be a short (even 0-length) commit */ 2031 __block_commit_write(inode, page, start, start+copied); 2032 2033 return copied; 2034 } 2035 EXPORT_SYMBOL(block_write_end); 2036 2037 int generic_write_end(struct file *file, struct address_space *mapping, 2038 loff_t pos, unsigned len, unsigned copied, 2039 struct page *page, void *fsdata) 2040 { 2041 struct inode *inode = mapping->host; 2042 2043 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata); 2044 2045 /* 2046 * No need to use i_size_read() here, the i_size 2047 * cannot change under us because we hold i_mutex. 2048 * 2049 * But it's important to update i_size while still holding page lock: 2050 * page writeout could otherwise come in and zero beyond i_size. 2051 */ 2052 if (pos+copied > inode->i_size) { 2053 i_size_write(inode, pos+copied); 2054 mark_inode_dirty(inode); 2055 } 2056 2057 unlock_page(page); 2058 page_cache_release(page); 2059 2060 return copied; 2061 } 2062 EXPORT_SYMBOL(generic_write_end); 2063 2064 /* 2065 * Generic "read page" function for block devices that have the normal 2066 * get_block functionality. This is most of the block device filesystems. 2067 * Reads the page asynchronously --- the unlock_buffer() and 2068 * set/clear_buffer_uptodate() functions propagate buffer state into the 2069 * page struct once IO has completed. 2070 */ 2071 int block_read_full_page(struct page *page, get_block_t *get_block) 2072 { 2073 struct inode *inode = page->mapping->host; 2074 sector_t iblock, lblock; 2075 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE]; 2076 unsigned int blocksize; 2077 int nr, i; 2078 int fully_mapped = 1; 2079 2080 BUG_ON(!PageLocked(page)); 2081 blocksize = 1 << inode->i_blkbits; 2082 if (!page_has_buffers(page)) 2083 create_empty_buffers(page, blocksize, 0); 2084 head = page_buffers(page); 2085 2086 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits); 2087 lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits; 2088 bh = head; 2089 nr = 0; 2090 i = 0; 2091 2092 do { 2093 if (buffer_uptodate(bh)) 2094 continue; 2095 2096 if (!buffer_mapped(bh)) { 2097 int err = 0; 2098 2099 fully_mapped = 0; 2100 if (iblock < lblock) { 2101 WARN_ON(bh->b_size != blocksize); 2102 err = get_block(inode, iblock, bh, 0); 2103 if (err) 2104 SetPageError(page); 2105 } 2106 if (!buffer_mapped(bh)) { 2107 zero_user_page(page, i * blocksize, blocksize, 2108 KM_USER0); 2109 if (!err) 2110 set_buffer_uptodate(bh); 2111 continue; 2112 } 2113 /* 2114 * get_block() might have updated the buffer 2115 * synchronously 2116 */ 2117 if (buffer_uptodate(bh)) 2118 continue; 2119 } 2120 arr[nr++] = bh; 2121 } while (i++, iblock++, (bh = bh->b_this_page) != head); 2122 2123 if (fully_mapped) 2124 SetPageMappedToDisk(page); 2125 2126 if (!nr) { 2127 /* 2128 * All buffers are uptodate - we can set the page uptodate 2129 * as well. But not if get_block() returned an error. 2130 */ 2131 if (!PageError(page)) 2132 SetPageUptodate(page); 2133 unlock_page(page); 2134 return 0; 2135 } 2136 2137 /* Stage two: lock the buffers */ 2138 for (i = 0; i < nr; i++) { 2139 bh = arr[i]; 2140 lock_buffer(bh); 2141 mark_buffer_async_read(bh); 2142 } 2143 2144 /* 2145 * Stage 3: start the IO. Check for uptodateness 2146 * inside the buffer lock in case another process reading 2147 * the underlying blockdev brought it uptodate (the sct fix). 2148 */ 2149 for (i = 0; i < nr; i++) { 2150 bh = arr[i]; 2151 if (buffer_uptodate(bh)) 2152 end_buffer_async_read(bh, 1); 2153 else 2154 submit_bh(READ, bh); 2155 } 2156 return 0; 2157 } 2158 2159 /* utility function for filesystems that need to do work on expanding 2160 * truncates. Uses filesystem pagecache writes to allow the filesystem to 2161 * deal with the hole. 2162 */ 2163 int generic_cont_expand_simple(struct inode *inode, loff_t size) 2164 { 2165 struct address_space *mapping = inode->i_mapping; 2166 struct page *page; 2167 void *fsdata; 2168 unsigned long limit; 2169 int err; 2170 2171 err = -EFBIG; 2172 limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur; 2173 if (limit != RLIM_INFINITY && size > (loff_t)limit) { 2174 send_sig(SIGXFSZ, current, 0); 2175 goto out; 2176 } 2177 if (size > inode->i_sb->s_maxbytes) 2178 goto out; 2179 2180 err = pagecache_write_begin(NULL, mapping, size, 0, 2181 AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND, 2182 &page, &fsdata); 2183 if (err) 2184 goto out; 2185 2186 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata); 2187 BUG_ON(err > 0); 2188 2189 out: 2190 return err; 2191 } 2192 2193 int cont_expand_zero(struct file *file, struct address_space *mapping, 2194 loff_t pos, loff_t *bytes) 2195 { 2196 struct inode *inode = mapping->host; 2197 unsigned blocksize = 1 << inode->i_blkbits; 2198 struct page *page; 2199 void *fsdata; 2200 pgoff_t index, curidx; 2201 loff_t curpos; 2202 unsigned zerofrom, offset, len; 2203 int err = 0; 2204 2205 index = pos >> PAGE_CACHE_SHIFT; 2206 offset = pos & ~PAGE_CACHE_MASK; 2207 2208 while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) { 2209 zerofrom = curpos & ~PAGE_CACHE_MASK; 2210 if (zerofrom & (blocksize-1)) { 2211 *bytes |= (blocksize-1); 2212 (*bytes)++; 2213 } 2214 len = PAGE_CACHE_SIZE - zerofrom; 2215 2216 err = pagecache_write_begin(file, mapping, curpos, len, 2217 AOP_FLAG_UNINTERRUPTIBLE, 2218 &page, &fsdata); 2219 if (err) 2220 goto out; 2221 zero_user_page(page, zerofrom, len, KM_USER0); 2222 err = pagecache_write_end(file, mapping, curpos, len, len, 2223 page, fsdata); 2224 if (err < 0) 2225 goto out; 2226 BUG_ON(err != len); 2227 err = 0; 2228 } 2229 2230 /* page covers the boundary, find the boundary offset */ 2231 if (index == curidx) { 2232 zerofrom = curpos & ~PAGE_CACHE_MASK; 2233 /* if we will expand the thing last block will be filled */ 2234 if (offset <= zerofrom) { 2235 goto out; 2236 } 2237 if (zerofrom & (blocksize-1)) { 2238 *bytes |= (blocksize-1); 2239 (*bytes)++; 2240 } 2241 len = offset - zerofrom; 2242 2243 err = pagecache_write_begin(file, mapping, curpos, len, 2244 AOP_FLAG_UNINTERRUPTIBLE, 2245 &page, &fsdata); 2246 if (err) 2247 goto out; 2248 zero_user_page(page, zerofrom, len, KM_USER0); 2249 err = pagecache_write_end(file, mapping, curpos, len, len, 2250 page, fsdata); 2251 if (err < 0) 2252 goto out; 2253 BUG_ON(err != len); 2254 err = 0; 2255 } 2256 out: 2257 return err; 2258 } 2259 2260 /* 2261 * For moronic filesystems that do not allow holes in file. 2262 * We may have to extend the file. 2263 */ 2264 int cont_write_begin(struct file *file, struct address_space *mapping, 2265 loff_t pos, unsigned len, unsigned flags, 2266 struct page **pagep, void **fsdata, 2267 get_block_t *get_block, loff_t *bytes) 2268 { 2269 struct inode *inode = mapping->host; 2270 unsigned blocksize = 1 << inode->i_blkbits; 2271 unsigned zerofrom; 2272 int err; 2273 2274 err = cont_expand_zero(file, mapping, pos, bytes); 2275 if (err) 2276 goto out; 2277 2278 zerofrom = *bytes & ~PAGE_CACHE_MASK; 2279 if (pos+len > *bytes && zerofrom & (blocksize-1)) { 2280 *bytes |= (blocksize-1); 2281 (*bytes)++; 2282 } 2283 2284 *pagep = NULL; 2285 err = block_write_begin(file, mapping, pos, len, 2286 flags, pagep, fsdata, get_block); 2287 out: 2288 return err; 2289 } 2290 2291 int block_prepare_write(struct page *page, unsigned from, unsigned to, 2292 get_block_t *get_block) 2293 { 2294 struct inode *inode = page->mapping->host; 2295 int err = __block_prepare_write(inode, page, from, to, get_block); 2296 if (err) 2297 ClearPageUptodate(page); 2298 return err; 2299 } 2300 2301 int block_commit_write(struct page *page, unsigned from, unsigned to) 2302 { 2303 struct inode *inode = page->mapping->host; 2304 __block_commit_write(inode,page,from,to); 2305 return 0; 2306 } 2307 2308 int generic_commit_write(struct file *file, struct page *page, 2309 unsigned from, unsigned to) 2310 { 2311 struct inode *inode = page->mapping->host; 2312 loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to; 2313 __block_commit_write(inode,page,from,to); 2314 /* 2315 * No need to use i_size_read() here, the i_size 2316 * cannot change under us because we hold i_mutex. 2317 */ 2318 if (pos > inode->i_size) { 2319 i_size_write(inode, pos); 2320 mark_inode_dirty(inode); 2321 } 2322 return 0; 2323 } 2324 2325 /* 2326 * block_page_mkwrite() is not allowed to change the file size as it gets 2327 * called from a page fault handler when a page is first dirtied. Hence we must 2328 * be careful to check for EOF conditions here. We set the page up correctly 2329 * for a written page which means we get ENOSPC checking when writing into 2330 * holes and correct delalloc and unwritten extent mapping on filesystems that 2331 * support these features. 2332 * 2333 * We are not allowed to take the i_mutex here so we have to play games to 2334 * protect against truncate races as the page could now be beyond EOF. Because 2335 * vmtruncate() writes the inode size before removing pages, once we have the 2336 * page lock we can determine safely if the page is beyond EOF. If it is not 2337 * beyond EOF, then the page is guaranteed safe against truncation until we 2338 * unlock the page. 2339 */ 2340 int 2341 block_page_mkwrite(struct vm_area_struct *vma, struct page *page, 2342 get_block_t get_block) 2343 { 2344 struct inode *inode = vma->vm_file->f_path.dentry->d_inode; 2345 unsigned long end; 2346 loff_t size; 2347 int ret = -EINVAL; 2348 2349 lock_page(page); 2350 size = i_size_read(inode); 2351 if ((page->mapping != inode->i_mapping) || 2352 (page_offset(page) > size)) { 2353 /* page got truncated out from underneath us */ 2354 goto out_unlock; 2355 } 2356 2357 /* page is wholly or partially inside EOF */ 2358 if (((page->index + 1) << PAGE_CACHE_SHIFT) > size) 2359 end = size & ~PAGE_CACHE_MASK; 2360 else 2361 end = PAGE_CACHE_SIZE; 2362 2363 ret = block_prepare_write(page, 0, end, get_block); 2364 if (!ret) 2365 ret = block_commit_write(page, 0, end); 2366 2367 out_unlock: 2368 unlock_page(page); 2369 return ret; 2370 } 2371 2372 /* 2373 * nobh_write_begin()'s prereads are special: the buffer_heads are freed 2374 * immediately, while under the page lock. So it needs a special end_io 2375 * handler which does not touch the bh after unlocking it. 2376 */ 2377 static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate) 2378 { 2379 __end_buffer_read_notouch(bh, uptodate); 2380 } 2381 2382 /* 2383 * Attach the singly-linked list of buffers created by nobh_write_begin, to 2384 * the page (converting it to circular linked list and taking care of page 2385 * dirty races). 2386 */ 2387 static void attach_nobh_buffers(struct page *page, struct buffer_head *head) 2388 { 2389 struct buffer_head *bh; 2390 2391 BUG_ON(!PageLocked(page)); 2392 2393 spin_lock(&page->mapping->private_lock); 2394 bh = head; 2395 do { 2396 if (PageDirty(page)) 2397 set_buffer_dirty(bh); 2398 if (!bh->b_this_page) 2399 bh->b_this_page = head; 2400 bh = bh->b_this_page; 2401 } while (bh != head); 2402 attach_page_buffers(page, head); 2403 spin_unlock(&page->mapping->private_lock); 2404 } 2405 2406 /* 2407 * On entry, the page is fully not uptodate. 2408 * On exit the page is fully uptodate in the areas outside (from,to) 2409 */ 2410 int nobh_write_begin(struct file *file, struct address_space *mapping, 2411 loff_t pos, unsigned len, unsigned flags, 2412 struct page **pagep, void **fsdata, 2413 get_block_t *get_block) 2414 { 2415 struct inode *inode = mapping->host; 2416 const unsigned blkbits = inode->i_blkbits; 2417 const unsigned blocksize = 1 << blkbits; 2418 struct buffer_head *head, *bh; 2419 struct page *page; 2420 pgoff_t index; 2421 unsigned from, to; 2422 unsigned block_in_page; 2423 unsigned block_start, block_end; 2424 sector_t block_in_file; 2425 char *kaddr; 2426 int nr_reads = 0; 2427 int ret = 0; 2428 int is_mapped_to_disk = 1; 2429 2430 index = pos >> PAGE_CACHE_SHIFT; 2431 from = pos & (PAGE_CACHE_SIZE - 1); 2432 to = from + len; 2433 2434 page = __grab_cache_page(mapping, index); 2435 if (!page) 2436 return -ENOMEM; 2437 *pagep = page; 2438 *fsdata = NULL; 2439 2440 if (page_has_buffers(page)) { 2441 unlock_page(page); 2442 page_cache_release(page); 2443 *pagep = NULL; 2444 return block_write_begin(file, mapping, pos, len, flags, pagep, 2445 fsdata, get_block); 2446 } 2447 2448 if (PageMappedToDisk(page)) 2449 return 0; 2450 2451 /* 2452 * Allocate buffers so that we can keep track of state, and potentially 2453 * attach them to the page if an error occurs. In the common case of 2454 * no error, they will just be freed again without ever being attached 2455 * to the page (which is all OK, because we're under the page lock). 2456 * 2457 * Be careful: the buffer linked list is a NULL terminated one, rather 2458 * than the circular one we're used to. 2459 */ 2460 head = alloc_page_buffers(page, blocksize, 0); 2461 if (!head) { 2462 ret = -ENOMEM; 2463 goto out_release; 2464 } 2465 2466 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits); 2467 2468 /* 2469 * We loop across all blocks in the page, whether or not they are 2470 * part of the affected region. This is so we can discover if the 2471 * page is fully mapped-to-disk. 2472 */ 2473 for (block_start = 0, block_in_page = 0, bh = head; 2474 block_start < PAGE_CACHE_SIZE; 2475 block_in_page++, block_start += blocksize, bh = bh->b_this_page) { 2476 int create; 2477 2478 block_end = block_start + blocksize; 2479 bh->b_state = 0; 2480 create = 1; 2481 if (block_start >= to) 2482 create = 0; 2483 ret = get_block(inode, block_in_file + block_in_page, 2484 bh, create); 2485 if (ret) 2486 goto failed; 2487 if (!buffer_mapped(bh)) 2488 is_mapped_to_disk = 0; 2489 if (buffer_new(bh)) 2490 unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr); 2491 if (PageUptodate(page)) { 2492 set_buffer_uptodate(bh); 2493 continue; 2494 } 2495 if (buffer_new(bh) || !buffer_mapped(bh)) { 2496 kaddr = kmap_atomic(page, KM_USER0); 2497 if (block_start < from) 2498 memset(kaddr+block_start, 0, from-block_start); 2499 if (block_end > to) 2500 memset(kaddr + to, 0, block_end - to); 2501 flush_dcache_page(page); 2502 kunmap_atomic(kaddr, KM_USER0); 2503 continue; 2504 } 2505 if (buffer_uptodate(bh)) 2506 continue; /* reiserfs does this */ 2507 if (block_start < from || block_end > to) { 2508 lock_buffer(bh); 2509 bh->b_end_io = end_buffer_read_nobh; 2510 submit_bh(READ, bh); 2511 nr_reads++; 2512 } 2513 } 2514 2515 if (nr_reads) { 2516 /* 2517 * The page is locked, so these buffers are protected from 2518 * any VM or truncate activity. Hence we don't need to care 2519 * for the buffer_head refcounts. 2520 */ 2521 for (bh = head; bh; bh = bh->b_this_page) { 2522 wait_on_buffer(bh); 2523 if (!buffer_uptodate(bh)) 2524 ret = -EIO; 2525 } 2526 if (ret) 2527 goto failed; 2528 } 2529 2530 if (is_mapped_to_disk) 2531 SetPageMappedToDisk(page); 2532 2533 *fsdata = head; /* to be released by nobh_write_end */ 2534 2535 return 0; 2536 2537 failed: 2538 BUG_ON(!ret); 2539 /* 2540 * Error recovery is a bit difficult. We need to zero out blocks that 2541 * were newly allocated, and dirty them to ensure they get written out. 2542 * Buffers need to be attached to the page at this point, otherwise 2543 * the handling of potential IO errors during writeout would be hard 2544 * (could try doing synchronous writeout, but what if that fails too?) 2545 */ 2546 attach_nobh_buffers(page, head); 2547 page_zero_new_buffers(page, from, to); 2548 2549 out_release: 2550 unlock_page(page); 2551 page_cache_release(page); 2552 *pagep = NULL; 2553 2554 if (pos + len > inode->i_size) 2555 vmtruncate(inode, inode->i_size); 2556 2557 return ret; 2558 } 2559 EXPORT_SYMBOL(nobh_write_begin); 2560 2561 int nobh_write_end(struct file *file, struct address_space *mapping, 2562 loff_t pos, unsigned len, unsigned copied, 2563 struct page *page, void *fsdata) 2564 { 2565 struct inode *inode = page->mapping->host; 2566 struct buffer_head *head = fsdata; 2567 struct buffer_head *bh; 2568 2569 if (!PageMappedToDisk(page)) { 2570 if (unlikely(copied < len) && !page_has_buffers(page)) 2571 attach_nobh_buffers(page, head); 2572 if (page_has_buffers(page)) 2573 return generic_write_end(file, mapping, pos, len, 2574 copied, page, fsdata); 2575 } 2576 2577 SetPageUptodate(page); 2578 set_page_dirty(page); 2579 if (pos+copied > inode->i_size) { 2580 i_size_write(inode, pos+copied); 2581 mark_inode_dirty(inode); 2582 } 2583 2584 unlock_page(page); 2585 page_cache_release(page); 2586 2587 while (head) { 2588 bh = head; 2589 head = head->b_this_page; 2590 free_buffer_head(bh); 2591 } 2592 2593 return copied; 2594 } 2595 EXPORT_SYMBOL(nobh_write_end); 2596 2597 /* 2598 * nobh_writepage() - based on block_full_write_page() except 2599 * that it tries to operate without attaching bufferheads to 2600 * the page. 2601 */ 2602 int nobh_writepage(struct page *page, get_block_t *get_block, 2603 struct writeback_control *wbc) 2604 { 2605 struct inode * const inode = page->mapping->host; 2606 loff_t i_size = i_size_read(inode); 2607 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT; 2608 unsigned offset; 2609 int ret; 2610 2611 /* Is the page fully inside i_size? */ 2612 if (page->index < end_index) 2613 goto out; 2614 2615 /* Is the page fully outside i_size? (truncate in progress) */ 2616 offset = i_size & (PAGE_CACHE_SIZE-1); 2617 if (page->index >= end_index+1 || !offset) { 2618 /* 2619 * The page may have dirty, unmapped buffers. For example, 2620 * they may have been added in ext3_writepage(). Make them 2621 * freeable here, so the page does not leak. 2622 */ 2623 #if 0 2624 /* Not really sure about this - do we need this ? */ 2625 if (page->mapping->a_ops->invalidatepage) 2626 page->mapping->a_ops->invalidatepage(page, offset); 2627 #endif 2628 unlock_page(page); 2629 return 0; /* don't care */ 2630 } 2631 2632 /* 2633 * The page straddles i_size. It must be zeroed out on each and every 2634 * writepage invocation because it may be mmapped. "A file is mapped 2635 * in multiples of the page size. For a file that is not a multiple of 2636 * the page size, the remaining memory is zeroed when mapped, and 2637 * writes to that region are not written out to the file." 2638 */ 2639 zero_user_page(page, offset, PAGE_CACHE_SIZE - offset, KM_USER0); 2640 out: 2641 ret = mpage_writepage(page, get_block, wbc); 2642 if (ret == -EAGAIN) 2643 ret = __block_write_full_page(inode, page, get_block, wbc); 2644 return ret; 2645 } 2646 EXPORT_SYMBOL(nobh_writepage); 2647 2648 int nobh_truncate_page(struct address_space *mapping, 2649 loff_t from, get_block_t *get_block) 2650 { 2651 pgoff_t index = from >> PAGE_CACHE_SHIFT; 2652 unsigned offset = from & (PAGE_CACHE_SIZE-1); 2653 unsigned blocksize; 2654 sector_t iblock; 2655 unsigned length, pos; 2656 struct inode *inode = mapping->host; 2657 struct page *page; 2658 struct buffer_head map_bh; 2659 int err; 2660 2661 blocksize = 1 << inode->i_blkbits; 2662 length = offset & (blocksize - 1); 2663 2664 /* Block boundary? Nothing to do */ 2665 if (!length) 2666 return 0; 2667 2668 length = blocksize - length; 2669 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits); 2670 2671 page = grab_cache_page(mapping, index); 2672 err = -ENOMEM; 2673 if (!page) 2674 goto out; 2675 2676 if (page_has_buffers(page)) { 2677 has_buffers: 2678 unlock_page(page); 2679 page_cache_release(page); 2680 return block_truncate_page(mapping, from, get_block); 2681 } 2682 2683 /* Find the buffer that contains "offset" */ 2684 pos = blocksize; 2685 while (offset >= pos) { 2686 iblock++; 2687 pos += blocksize; 2688 } 2689 2690 err = get_block(inode, iblock, &map_bh, 0); 2691 if (err) 2692 goto unlock; 2693 /* unmapped? It's a hole - nothing to do */ 2694 if (!buffer_mapped(&map_bh)) 2695 goto unlock; 2696 2697 /* Ok, it's mapped. Make sure it's up-to-date */ 2698 if (!PageUptodate(page)) { 2699 err = mapping->a_ops->readpage(NULL, page); 2700 if (err) { 2701 page_cache_release(page); 2702 goto out; 2703 } 2704 lock_page(page); 2705 if (!PageUptodate(page)) { 2706 err = -EIO; 2707 goto unlock; 2708 } 2709 if (page_has_buffers(page)) 2710 goto has_buffers; 2711 } 2712 zero_user_page(page, offset, length, KM_USER0); 2713 set_page_dirty(page); 2714 err = 0; 2715 2716 unlock: 2717 unlock_page(page); 2718 page_cache_release(page); 2719 out: 2720 return err; 2721 } 2722 EXPORT_SYMBOL(nobh_truncate_page); 2723 2724 int block_truncate_page(struct address_space *mapping, 2725 loff_t from, get_block_t *get_block) 2726 { 2727 pgoff_t index = from >> PAGE_CACHE_SHIFT; 2728 unsigned offset = from & (PAGE_CACHE_SIZE-1); 2729 unsigned blocksize; 2730 sector_t iblock; 2731 unsigned length, pos; 2732 struct inode *inode = mapping->host; 2733 struct page *page; 2734 struct buffer_head *bh; 2735 int err; 2736 2737 blocksize = 1 << inode->i_blkbits; 2738 length = offset & (blocksize - 1); 2739 2740 /* Block boundary? Nothing to do */ 2741 if (!length) 2742 return 0; 2743 2744 length = blocksize - length; 2745 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits); 2746 2747 page = grab_cache_page(mapping, index); 2748 err = -ENOMEM; 2749 if (!page) 2750 goto out; 2751 2752 if (!page_has_buffers(page)) 2753 create_empty_buffers(page, blocksize, 0); 2754 2755 /* Find the buffer that contains "offset" */ 2756 bh = page_buffers(page); 2757 pos = blocksize; 2758 while (offset >= pos) { 2759 bh = bh->b_this_page; 2760 iblock++; 2761 pos += blocksize; 2762 } 2763 2764 err = 0; 2765 if (!buffer_mapped(bh)) { 2766 WARN_ON(bh->b_size != blocksize); 2767 err = get_block(inode, iblock, bh, 0); 2768 if (err) 2769 goto unlock; 2770 /* unmapped? It's a hole - nothing to do */ 2771 if (!buffer_mapped(bh)) 2772 goto unlock; 2773 } 2774 2775 /* Ok, it's mapped. Make sure it's up-to-date */ 2776 if (PageUptodate(page)) 2777 set_buffer_uptodate(bh); 2778 2779 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) { 2780 err = -EIO; 2781 ll_rw_block(READ, 1, &bh); 2782 wait_on_buffer(bh); 2783 /* Uhhuh. Read error. Complain and punt. */ 2784 if (!buffer_uptodate(bh)) 2785 goto unlock; 2786 } 2787 2788 zero_user_page(page, offset, length, KM_USER0); 2789 mark_buffer_dirty(bh); 2790 err = 0; 2791 2792 unlock: 2793 unlock_page(page); 2794 page_cache_release(page); 2795 out: 2796 return err; 2797 } 2798 2799 /* 2800 * The generic ->writepage function for buffer-backed address_spaces 2801 */ 2802 int block_write_full_page(struct page *page, get_block_t *get_block, 2803 struct writeback_control *wbc) 2804 { 2805 struct inode * const inode = page->mapping->host; 2806 loff_t i_size = i_size_read(inode); 2807 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT; 2808 unsigned offset; 2809 2810 /* Is the page fully inside i_size? */ 2811 if (page->index < end_index) 2812 return __block_write_full_page(inode, page, get_block, wbc); 2813 2814 /* Is the page fully outside i_size? (truncate in progress) */ 2815 offset = i_size & (PAGE_CACHE_SIZE-1); 2816 if (page->index >= end_index+1 || !offset) { 2817 /* 2818 * The page may have dirty, unmapped buffers. For example, 2819 * they may have been added in ext3_writepage(). Make them 2820 * freeable here, so the page does not leak. 2821 */ 2822 do_invalidatepage(page, 0); 2823 unlock_page(page); 2824 return 0; /* don't care */ 2825 } 2826 2827 /* 2828 * The page straddles i_size. It must be zeroed out on each and every 2829 * writepage invokation because it may be mmapped. "A file is mapped 2830 * in multiples of the page size. For a file that is not a multiple of 2831 * the page size, the remaining memory is zeroed when mapped, and 2832 * writes to that region are not written out to the file." 2833 */ 2834 zero_user_page(page, offset, PAGE_CACHE_SIZE - offset, KM_USER0); 2835 return __block_write_full_page(inode, page, get_block, wbc); 2836 } 2837 2838 sector_t generic_block_bmap(struct address_space *mapping, sector_t block, 2839 get_block_t *get_block) 2840 { 2841 struct buffer_head tmp; 2842 struct inode *inode = mapping->host; 2843 tmp.b_state = 0; 2844 tmp.b_blocknr = 0; 2845 tmp.b_size = 1 << inode->i_blkbits; 2846 get_block(inode, block, &tmp, 0); 2847 return tmp.b_blocknr; 2848 } 2849 2850 static void end_bio_bh_io_sync(struct bio *bio, int err) 2851 { 2852 struct buffer_head *bh = bio->bi_private; 2853 2854 if (err == -EOPNOTSUPP) { 2855 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags); 2856 set_bit(BH_Eopnotsupp, &bh->b_state); 2857 } 2858 2859 bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags)); 2860 bio_put(bio); 2861 } 2862 2863 int submit_bh(int rw, struct buffer_head * bh) 2864 { 2865 struct bio *bio; 2866 int ret = 0; 2867 2868 BUG_ON(!buffer_locked(bh)); 2869 BUG_ON(!buffer_mapped(bh)); 2870 BUG_ON(!bh->b_end_io); 2871 2872 if (buffer_ordered(bh) && (rw == WRITE)) 2873 rw = WRITE_BARRIER; 2874 2875 /* 2876 * Only clear out a write error when rewriting, should this 2877 * include WRITE_SYNC as well? 2878 */ 2879 if (test_set_buffer_req(bh) && (rw == WRITE || rw == WRITE_BARRIER)) 2880 clear_buffer_write_io_error(bh); 2881 2882 /* 2883 * from here on down, it's all bio -- do the initial mapping, 2884 * submit_bio -> generic_make_request may further map this bio around 2885 */ 2886 bio = bio_alloc(GFP_NOIO, 1); 2887 2888 bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9); 2889 bio->bi_bdev = bh->b_bdev; 2890 bio->bi_io_vec[0].bv_page = bh->b_page; 2891 bio->bi_io_vec[0].bv_len = bh->b_size; 2892 bio->bi_io_vec[0].bv_offset = bh_offset(bh); 2893 2894 bio->bi_vcnt = 1; 2895 bio->bi_idx = 0; 2896 bio->bi_size = bh->b_size; 2897 2898 bio->bi_end_io = end_bio_bh_io_sync; 2899 bio->bi_private = bh; 2900 2901 bio_get(bio); 2902 submit_bio(rw, bio); 2903 2904 if (bio_flagged(bio, BIO_EOPNOTSUPP)) 2905 ret = -EOPNOTSUPP; 2906 2907 bio_put(bio); 2908 return ret; 2909 } 2910 2911 /** 2912 * ll_rw_block: low-level access to block devices (DEPRECATED) 2913 * @rw: whether to %READ or %WRITE or %SWRITE or maybe %READA (readahead) 2914 * @nr: number of &struct buffer_heads in the array 2915 * @bhs: array of pointers to &struct buffer_head 2916 * 2917 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and 2918 * requests an I/O operation on them, either a %READ or a %WRITE. The third 2919 * %SWRITE is like %WRITE only we make sure that the *current* data in buffers 2920 * are sent to disk. The fourth %READA option is described in the documentation 2921 * for generic_make_request() which ll_rw_block() calls. 2922 * 2923 * This function drops any buffer that it cannot get a lock on (with the 2924 * BH_Lock state bit) unless SWRITE is required, any buffer that appears to be 2925 * clean when doing a write request, and any buffer that appears to be 2926 * up-to-date when doing read request. Further it marks as clean buffers that 2927 * are processed for writing (the buffer cache won't assume that they are 2928 * actually clean until the buffer gets unlocked). 2929 * 2930 * ll_rw_block sets b_end_io to simple completion handler that marks 2931 * the buffer up-to-date (if approriate), unlocks the buffer and wakes 2932 * any waiters. 2933 * 2934 * All of the buffers must be for the same device, and must also be a 2935 * multiple of the current approved size for the device. 2936 */ 2937 void ll_rw_block(int rw, int nr, struct buffer_head *bhs[]) 2938 { 2939 int i; 2940 2941 for (i = 0; i < nr; i++) { 2942 struct buffer_head *bh = bhs[i]; 2943 2944 if (rw == SWRITE) 2945 lock_buffer(bh); 2946 else if (test_set_buffer_locked(bh)) 2947 continue; 2948 2949 if (rw == WRITE || rw == SWRITE) { 2950 if (test_clear_buffer_dirty(bh)) { 2951 bh->b_end_io = end_buffer_write_sync; 2952 get_bh(bh); 2953 submit_bh(WRITE, bh); 2954 continue; 2955 } 2956 } else { 2957 if (!buffer_uptodate(bh)) { 2958 bh->b_end_io = end_buffer_read_sync; 2959 get_bh(bh); 2960 submit_bh(rw, bh); 2961 continue; 2962 } 2963 } 2964 unlock_buffer(bh); 2965 } 2966 } 2967 2968 /* 2969 * For a data-integrity writeout, we need to wait upon any in-progress I/O 2970 * and then start new I/O and then wait upon it. The caller must have a ref on 2971 * the buffer_head. 2972 */ 2973 int sync_dirty_buffer(struct buffer_head *bh) 2974 { 2975 int ret = 0; 2976 2977 WARN_ON(atomic_read(&bh->b_count) < 1); 2978 lock_buffer(bh); 2979 if (test_clear_buffer_dirty(bh)) { 2980 get_bh(bh); 2981 bh->b_end_io = end_buffer_write_sync; 2982 ret = submit_bh(WRITE, bh); 2983 wait_on_buffer(bh); 2984 if (buffer_eopnotsupp(bh)) { 2985 clear_buffer_eopnotsupp(bh); 2986 ret = -EOPNOTSUPP; 2987 } 2988 if (!ret && !buffer_uptodate(bh)) 2989 ret = -EIO; 2990 } else { 2991 unlock_buffer(bh); 2992 } 2993 return ret; 2994 } 2995 2996 /* 2997 * try_to_free_buffers() checks if all the buffers on this particular page 2998 * are unused, and releases them if so. 2999 * 3000 * Exclusion against try_to_free_buffers may be obtained by either 3001 * locking the page or by holding its mapping's private_lock. 3002 * 3003 * If the page is dirty but all the buffers are clean then we need to 3004 * be sure to mark the page clean as well. This is because the page 3005 * may be against a block device, and a later reattachment of buffers 3006 * to a dirty page will set *all* buffers dirty. Which would corrupt 3007 * filesystem data on the same device. 3008 * 3009 * The same applies to regular filesystem pages: if all the buffers are 3010 * clean then we set the page clean and proceed. To do that, we require 3011 * total exclusion from __set_page_dirty_buffers(). That is obtained with 3012 * private_lock. 3013 * 3014 * try_to_free_buffers() is non-blocking. 3015 */ 3016 static inline int buffer_busy(struct buffer_head *bh) 3017 { 3018 return atomic_read(&bh->b_count) | 3019 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock))); 3020 } 3021 3022 static int 3023 drop_buffers(struct page *page, struct buffer_head **buffers_to_free) 3024 { 3025 struct buffer_head *head = page_buffers(page); 3026 struct buffer_head *bh; 3027 3028 bh = head; 3029 do { 3030 if (buffer_write_io_error(bh) && page->mapping) 3031 set_bit(AS_EIO, &page->mapping->flags); 3032 if (buffer_busy(bh)) 3033 goto failed; 3034 bh = bh->b_this_page; 3035 } while (bh != head); 3036 3037 do { 3038 struct buffer_head *next = bh->b_this_page; 3039 3040 if (!list_empty(&bh->b_assoc_buffers)) 3041 __remove_assoc_queue(bh); 3042 bh = next; 3043 } while (bh != head); 3044 *buffers_to_free = head; 3045 __clear_page_buffers(page); 3046 return 1; 3047 failed: 3048 return 0; 3049 } 3050 3051 int try_to_free_buffers(struct page *page) 3052 { 3053 struct address_space * const mapping = page->mapping; 3054 struct buffer_head *buffers_to_free = NULL; 3055 int ret = 0; 3056 3057 BUG_ON(!PageLocked(page)); 3058 if (PageWriteback(page)) 3059 return 0; 3060 3061 if (mapping == NULL) { /* can this still happen? */ 3062 ret = drop_buffers(page, &buffers_to_free); 3063 goto out; 3064 } 3065 3066 spin_lock(&mapping->private_lock); 3067 ret = drop_buffers(page, &buffers_to_free); 3068 3069 /* 3070 * If the filesystem writes its buffers by hand (eg ext3) 3071 * then we can have clean buffers against a dirty page. We 3072 * clean the page here; otherwise the VM will never notice 3073 * that the filesystem did any IO at all. 3074 * 3075 * Also, during truncate, discard_buffer will have marked all 3076 * the page's buffers clean. We discover that here and clean 3077 * the page also. 3078 * 3079 * private_lock must be held over this entire operation in order 3080 * to synchronise against __set_page_dirty_buffers and prevent the 3081 * dirty bit from being lost. 3082 */ 3083 if (ret) 3084 cancel_dirty_page(page, PAGE_CACHE_SIZE); 3085 spin_unlock(&mapping->private_lock); 3086 out: 3087 if (buffers_to_free) { 3088 struct buffer_head *bh = buffers_to_free; 3089 3090 do { 3091 struct buffer_head *next = bh->b_this_page; 3092 free_buffer_head(bh); 3093 bh = next; 3094 } while (bh != buffers_to_free); 3095 } 3096 return ret; 3097 } 3098 EXPORT_SYMBOL(try_to_free_buffers); 3099 3100 void block_sync_page(struct page *page) 3101 { 3102 struct address_space *mapping; 3103 3104 smp_mb(); 3105 mapping = page_mapping(page); 3106 if (mapping) 3107 blk_run_backing_dev(mapping->backing_dev_info, page); 3108 } 3109 3110 /* 3111 * There are no bdflush tunables left. But distributions are 3112 * still running obsolete flush daemons, so we terminate them here. 3113 * 3114 * Use of bdflush() is deprecated and will be removed in a future kernel. 3115 * The `pdflush' kernel threads fully replace bdflush daemons and this call. 3116 */ 3117 asmlinkage long sys_bdflush(int func, long data) 3118 { 3119 static int msg_count; 3120 3121 if (!capable(CAP_SYS_ADMIN)) 3122 return -EPERM; 3123 3124 if (msg_count < 5) { 3125 msg_count++; 3126 printk(KERN_INFO 3127 "warning: process `%s' used the obsolete bdflush" 3128 " system call\n", current->comm); 3129 printk(KERN_INFO "Fix your initscripts?\n"); 3130 } 3131 3132 if (func == 1) 3133 do_exit(0); 3134 return 0; 3135 } 3136 3137 /* 3138 * Buffer-head allocation 3139 */ 3140 static struct kmem_cache *bh_cachep; 3141 3142 /* 3143 * Once the number of bh's in the machine exceeds this level, we start 3144 * stripping them in writeback. 3145 */ 3146 static int max_buffer_heads; 3147 3148 int buffer_heads_over_limit; 3149 3150 struct bh_accounting { 3151 int nr; /* Number of live bh's */ 3152 int ratelimit; /* Limit cacheline bouncing */ 3153 }; 3154 3155 static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0}; 3156 3157 static void recalc_bh_state(void) 3158 { 3159 int i; 3160 int tot = 0; 3161 3162 if (__get_cpu_var(bh_accounting).ratelimit++ < 4096) 3163 return; 3164 __get_cpu_var(bh_accounting).ratelimit = 0; 3165 for_each_online_cpu(i) 3166 tot += per_cpu(bh_accounting, i).nr; 3167 buffer_heads_over_limit = (tot > max_buffer_heads); 3168 } 3169 3170 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags) 3171 { 3172 struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, 3173 set_migrateflags(gfp_flags, __GFP_RECLAIMABLE)); 3174 if (ret) { 3175 INIT_LIST_HEAD(&ret->b_assoc_buffers); 3176 get_cpu_var(bh_accounting).nr++; 3177 recalc_bh_state(); 3178 put_cpu_var(bh_accounting); 3179 } 3180 return ret; 3181 } 3182 EXPORT_SYMBOL(alloc_buffer_head); 3183 3184 void free_buffer_head(struct buffer_head *bh) 3185 { 3186 BUG_ON(!list_empty(&bh->b_assoc_buffers)); 3187 kmem_cache_free(bh_cachep, bh); 3188 get_cpu_var(bh_accounting).nr--; 3189 recalc_bh_state(); 3190 put_cpu_var(bh_accounting); 3191 } 3192 EXPORT_SYMBOL(free_buffer_head); 3193 3194 static void buffer_exit_cpu(int cpu) 3195 { 3196 int i; 3197 struct bh_lru *b = &per_cpu(bh_lrus, cpu); 3198 3199 for (i = 0; i < BH_LRU_SIZE; i++) { 3200 brelse(b->bhs[i]); 3201 b->bhs[i] = NULL; 3202 } 3203 get_cpu_var(bh_accounting).nr += per_cpu(bh_accounting, cpu).nr; 3204 per_cpu(bh_accounting, cpu).nr = 0; 3205 put_cpu_var(bh_accounting); 3206 } 3207 3208 static int buffer_cpu_notify(struct notifier_block *self, 3209 unsigned long action, void *hcpu) 3210 { 3211 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) 3212 buffer_exit_cpu((unsigned long)hcpu); 3213 return NOTIFY_OK; 3214 } 3215 3216 /** 3217 * bh_uptodate_or_lock: Test whether the buffer is uptodate 3218 * @bh: struct buffer_head 3219 * 3220 * Return true if the buffer is up-to-date and false, 3221 * with the buffer locked, if not. 3222 */ 3223 int bh_uptodate_or_lock(struct buffer_head *bh) 3224 { 3225 if (!buffer_uptodate(bh)) { 3226 lock_buffer(bh); 3227 if (!buffer_uptodate(bh)) 3228 return 0; 3229 unlock_buffer(bh); 3230 } 3231 return 1; 3232 } 3233 EXPORT_SYMBOL(bh_uptodate_or_lock); 3234 3235 /** 3236 * bh_submit_read: Submit a locked buffer for reading 3237 * @bh: struct buffer_head 3238 * 3239 * Returns zero on success and -EIO on error. 3240 */ 3241 int bh_submit_read(struct buffer_head *bh) 3242 { 3243 BUG_ON(!buffer_locked(bh)); 3244 3245 if (buffer_uptodate(bh)) { 3246 unlock_buffer(bh); 3247 return 0; 3248 } 3249 3250 get_bh(bh); 3251 bh->b_end_io = end_buffer_read_sync; 3252 submit_bh(READ, bh); 3253 wait_on_buffer(bh); 3254 if (buffer_uptodate(bh)) 3255 return 0; 3256 return -EIO; 3257 } 3258 EXPORT_SYMBOL(bh_submit_read); 3259 3260 void __init buffer_init(void) 3261 { 3262 int nrpages; 3263 3264 bh_cachep = KMEM_CACHE(buffer_head, 3265 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD); 3266 3267 /* 3268 * Limit the bh occupancy to 10% of ZONE_NORMAL 3269 */ 3270 nrpages = (nr_free_buffer_pages() * 10) / 100; 3271 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head)); 3272 hotcpu_notifier(buffer_cpu_notify, 0); 3273 } 3274 3275 EXPORT_SYMBOL(__bforget); 3276 EXPORT_SYMBOL(__brelse); 3277 EXPORT_SYMBOL(__wait_on_buffer); 3278 EXPORT_SYMBOL(block_commit_write); 3279 EXPORT_SYMBOL(block_prepare_write); 3280 EXPORT_SYMBOL(block_page_mkwrite); 3281 EXPORT_SYMBOL(block_read_full_page); 3282 EXPORT_SYMBOL(block_sync_page); 3283 EXPORT_SYMBOL(block_truncate_page); 3284 EXPORT_SYMBOL(block_write_full_page); 3285 EXPORT_SYMBOL(cont_write_begin); 3286 EXPORT_SYMBOL(end_buffer_read_sync); 3287 EXPORT_SYMBOL(end_buffer_write_sync); 3288 EXPORT_SYMBOL(file_fsync); 3289 EXPORT_SYMBOL(fsync_bdev); 3290 EXPORT_SYMBOL(generic_block_bmap); 3291 EXPORT_SYMBOL(generic_commit_write); 3292 EXPORT_SYMBOL(generic_cont_expand_simple); 3293 EXPORT_SYMBOL(init_buffer); 3294 EXPORT_SYMBOL(invalidate_bdev); 3295 EXPORT_SYMBOL(ll_rw_block); 3296 EXPORT_SYMBOL(mark_buffer_dirty); 3297 EXPORT_SYMBOL(submit_bh); 3298 EXPORT_SYMBOL(sync_dirty_buffer); 3299 EXPORT_SYMBOL(unlock_buffer); 3300