Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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/config.h> |
| 22 | #include <linux/kernel.h> |
| 23 | #include <linux/syscalls.h> |
| 24 | #include <linux/fs.h> |
| 25 | #include <linux/mm.h> |
| 26 | #include <linux/percpu.h> |
| 27 | #include <linux/slab.h> |
| 28 | #include <linux/smp_lock.h> |
| 29 | #include <linux/blkdev.h> |
| 30 | #include <linux/file.h> |
| 31 | #include <linux/quotaops.h> |
| 32 | #include <linux/highmem.h> |
| 33 | #include <linux/module.h> |
| 34 | #include <linux/writeback.h> |
| 35 | #include <linux/hash.h> |
| 36 | #include <linux/suspend.h> |
| 37 | #include <linux/buffer_head.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 | |
| 44 | static int fsync_buffers_list(spinlock_t *lock, struct list_head *list); |
| 45 | static void invalidate_bh_lrus(void); |
| 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 | clear_buffer_locked(bh); |
| 80 | smp_mb__after_clear_bit(); |
| 81 | wake_up_bit(&bh->b_state, BH_Lock); |
| 82 | } |
| 83 | |
| 84 | /* |
| 85 | * Block until a buffer comes unlocked. This doesn't stop it |
| 86 | * from becoming locked again - you have to lock it yourself |
| 87 | * if you want to preserve its state. |
| 88 | */ |
| 89 | void __wait_on_buffer(struct buffer_head * bh) |
| 90 | { |
| 91 | wait_on_bit(&bh->b_state, BH_Lock, sync_buffer, TASK_UNINTERRUPTIBLE); |
| 92 | } |
| 93 | |
| 94 | static void |
| 95 | __clear_page_buffers(struct page *page) |
| 96 | { |
| 97 | ClearPagePrivate(page); |
| 98 | page->private = 0; |
| 99 | page_cache_release(page); |
| 100 | } |
| 101 | |
| 102 | static void buffer_io_error(struct buffer_head *bh) |
| 103 | { |
| 104 | char b[BDEVNAME_SIZE]; |
| 105 | |
| 106 | printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n", |
| 107 | bdevname(bh->b_bdev, b), |
| 108 | (unsigned long long)bh->b_blocknr); |
| 109 | } |
| 110 | |
| 111 | /* |
| 112 | * Default synchronous end-of-IO handler.. Just mark it up-to-date and |
| 113 | * unlock the buffer. This is what ll_rw_block uses too. |
| 114 | */ |
| 115 | void end_buffer_read_sync(struct buffer_head *bh, int uptodate) |
| 116 | { |
| 117 | if (uptodate) { |
| 118 | set_buffer_uptodate(bh); |
| 119 | } else { |
| 120 | /* This happens, due to failed READA attempts. */ |
| 121 | clear_buffer_uptodate(bh); |
| 122 | } |
| 123 | unlock_buffer(bh); |
| 124 | put_bh(bh); |
| 125 | } |
| 126 | |
| 127 | void end_buffer_write_sync(struct buffer_head *bh, int uptodate) |
| 128 | { |
| 129 | char b[BDEVNAME_SIZE]; |
| 130 | |
| 131 | if (uptodate) { |
| 132 | set_buffer_uptodate(bh); |
| 133 | } else { |
| 134 | if (!buffer_eopnotsupp(bh) && printk_ratelimit()) { |
| 135 | buffer_io_error(bh); |
| 136 | printk(KERN_WARNING "lost page write due to " |
| 137 | "I/O error on %s\n", |
| 138 | bdevname(bh->b_bdev, b)); |
| 139 | } |
| 140 | set_buffer_write_io_error(bh); |
| 141 | clear_buffer_uptodate(bh); |
| 142 | } |
| 143 | unlock_buffer(bh); |
| 144 | put_bh(bh); |
| 145 | } |
| 146 | |
| 147 | /* |
| 148 | * Write out and wait upon all the dirty data associated with a block |
| 149 | * device via its mapping. Does not take the superblock lock. |
| 150 | */ |
| 151 | int sync_blockdev(struct block_device *bdev) |
| 152 | { |
| 153 | int ret = 0; |
| 154 | |
| 155 | if (bdev) { |
| 156 | int err; |
| 157 | |
| 158 | ret = filemap_fdatawrite(bdev->bd_inode->i_mapping); |
| 159 | err = filemap_fdatawait(bdev->bd_inode->i_mapping); |
| 160 | if (!ret) |
| 161 | ret = err; |
| 162 | } |
| 163 | return ret; |
| 164 | } |
| 165 | EXPORT_SYMBOL(sync_blockdev); |
| 166 | |
| 167 | /* |
| 168 | * Write out and wait upon all dirty data associated with this |
| 169 | * superblock. Filesystem data as well as the underlying block |
| 170 | * device. Takes the superblock lock. |
| 171 | */ |
| 172 | int fsync_super(struct super_block *sb) |
| 173 | { |
| 174 | sync_inodes_sb(sb, 0); |
| 175 | DQUOT_SYNC(sb); |
| 176 | lock_super(sb); |
| 177 | if (sb->s_dirt && sb->s_op->write_super) |
| 178 | sb->s_op->write_super(sb); |
| 179 | unlock_super(sb); |
| 180 | if (sb->s_op->sync_fs) |
| 181 | sb->s_op->sync_fs(sb, 1); |
| 182 | sync_blockdev(sb->s_bdev); |
| 183 | sync_inodes_sb(sb, 1); |
| 184 | |
| 185 | return sync_blockdev(sb->s_bdev); |
| 186 | } |
| 187 | |
| 188 | /* |
| 189 | * Write out and wait upon all dirty data associated with this |
| 190 | * device. Filesystem data as well as the underlying block |
| 191 | * device. Takes the superblock lock. |
| 192 | */ |
| 193 | int fsync_bdev(struct block_device *bdev) |
| 194 | { |
| 195 | struct super_block *sb = get_super(bdev); |
| 196 | if (sb) { |
| 197 | int res = fsync_super(sb); |
| 198 | drop_super(sb); |
| 199 | return res; |
| 200 | } |
| 201 | return sync_blockdev(bdev); |
| 202 | } |
| 203 | |
| 204 | /** |
| 205 | * freeze_bdev -- lock a filesystem and force it into a consistent state |
| 206 | * @bdev: blockdevice to lock |
| 207 | * |
| 208 | * This takes the block device bd_mount_sem to make sure no new mounts |
| 209 | * happen on bdev until thaw_bdev() is called. |
| 210 | * If a superblock is found on this device, we take the s_umount semaphore |
| 211 | * on it to make sure nobody unmounts until the snapshot creation is done. |
| 212 | */ |
| 213 | struct super_block *freeze_bdev(struct block_device *bdev) |
| 214 | { |
| 215 | struct super_block *sb; |
| 216 | |
| 217 | down(&bdev->bd_mount_sem); |
| 218 | sb = get_super(bdev); |
| 219 | if (sb && !(sb->s_flags & MS_RDONLY)) { |
| 220 | sb->s_frozen = SB_FREEZE_WRITE; |
akpm@osdl.org | d59dd46 | 2005-05-01 08:58:47 -0700 | [diff] [blame] | 221 | smp_wmb(); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 222 | |
| 223 | sync_inodes_sb(sb, 0); |
| 224 | DQUOT_SYNC(sb); |
| 225 | |
| 226 | lock_super(sb); |
| 227 | if (sb->s_dirt && sb->s_op->write_super) |
| 228 | sb->s_op->write_super(sb); |
| 229 | unlock_super(sb); |
| 230 | |
| 231 | if (sb->s_op->sync_fs) |
| 232 | sb->s_op->sync_fs(sb, 1); |
| 233 | |
| 234 | sync_blockdev(sb->s_bdev); |
| 235 | sync_inodes_sb(sb, 1); |
| 236 | |
| 237 | sb->s_frozen = SB_FREEZE_TRANS; |
akpm@osdl.org | d59dd46 | 2005-05-01 08:58:47 -0700 | [diff] [blame] | 238 | smp_wmb(); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 239 | |
| 240 | sync_blockdev(sb->s_bdev); |
| 241 | |
| 242 | if (sb->s_op->write_super_lockfs) |
| 243 | sb->s_op->write_super_lockfs(sb); |
| 244 | } |
| 245 | |
| 246 | sync_blockdev(bdev); |
| 247 | return sb; /* thaw_bdev releases s->s_umount and bd_mount_sem */ |
| 248 | } |
| 249 | EXPORT_SYMBOL(freeze_bdev); |
| 250 | |
| 251 | /** |
| 252 | * thaw_bdev -- unlock filesystem |
| 253 | * @bdev: blockdevice to unlock |
| 254 | * @sb: associated superblock |
| 255 | * |
| 256 | * Unlocks the filesystem and marks it writeable again after freeze_bdev(). |
| 257 | */ |
| 258 | void thaw_bdev(struct block_device *bdev, struct super_block *sb) |
| 259 | { |
| 260 | if (sb) { |
| 261 | BUG_ON(sb->s_bdev != bdev); |
| 262 | |
| 263 | if (sb->s_op->unlockfs) |
| 264 | sb->s_op->unlockfs(sb); |
| 265 | sb->s_frozen = SB_UNFROZEN; |
akpm@osdl.org | d59dd46 | 2005-05-01 08:58:47 -0700 | [diff] [blame] | 266 | smp_wmb(); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 267 | wake_up(&sb->s_wait_unfrozen); |
| 268 | drop_super(sb); |
| 269 | } |
| 270 | |
| 271 | up(&bdev->bd_mount_sem); |
| 272 | } |
| 273 | EXPORT_SYMBOL(thaw_bdev); |
| 274 | |
| 275 | /* |
| 276 | * sync everything. Start out by waking pdflush, because that writes back |
| 277 | * all queues in parallel. |
| 278 | */ |
| 279 | static void do_sync(unsigned long wait) |
| 280 | { |
| 281 | wakeup_bdflush(0); |
| 282 | sync_inodes(0); /* All mappings, inodes and their blockdevs */ |
| 283 | DQUOT_SYNC(NULL); |
| 284 | sync_supers(); /* Write the superblocks */ |
| 285 | sync_filesystems(0); /* Start syncing the filesystems */ |
| 286 | sync_filesystems(wait); /* Waitingly sync the filesystems */ |
| 287 | sync_inodes(wait); /* Mappings, inodes and blockdevs, again. */ |
| 288 | if (!wait) |
| 289 | printk("Emergency Sync complete\n"); |
| 290 | if (unlikely(laptop_mode)) |
| 291 | laptop_sync_completion(); |
| 292 | } |
| 293 | |
| 294 | asmlinkage long sys_sync(void) |
| 295 | { |
| 296 | do_sync(1); |
| 297 | return 0; |
| 298 | } |
| 299 | |
| 300 | void emergency_sync(void) |
| 301 | { |
| 302 | pdflush_operation(do_sync, 0); |
| 303 | } |
| 304 | |
| 305 | /* |
| 306 | * Generic function to fsync a file. |
| 307 | * |
| 308 | * filp may be NULL if called via the msync of a vma. |
| 309 | */ |
| 310 | |
| 311 | int file_fsync(struct file *filp, struct dentry *dentry, int datasync) |
| 312 | { |
| 313 | struct inode * inode = dentry->d_inode; |
| 314 | struct super_block * sb; |
| 315 | int ret, err; |
| 316 | |
| 317 | /* sync the inode to buffers */ |
| 318 | ret = write_inode_now(inode, 0); |
| 319 | |
| 320 | /* sync the superblock to buffers */ |
| 321 | sb = inode->i_sb; |
| 322 | lock_super(sb); |
| 323 | if (sb->s_op->write_super) |
| 324 | sb->s_op->write_super(sb); |
| 325 | unlock_super(sb); |
| 326 | |
| 327 | /* .. finally sync the buffers to disk */ |
| 328 | err = sync_blockdev(sb->s_bdev); |
| 329 | if (!ret) |
| 330 | ret = err; |
| 331 | return ret; |
| 332 | } |
| 333 | |
| 334 | asmlinkage long sys_fsync(unsigned int fd) |
| 335 | { |
| 336 | struct file * file; |
| 337 | struct address_space *mapping; |
| 338 | int ret, err; |
| 339 | |
| 340 | ret = -EBADF; |
| 341 | file = fget(fd); |
| 342 | if (!file) |
| 343 | goto out; |
| 344 | |
| 345 | mapping = file->f_mapping; |
| 346 | |
| 347 | ret = -EINVAL; |
| 348 | if (!file->f_op || !file->f_op->fsync) { |
| 349 | /* Why? We can still call filemap_fdatawrite */ |
| 350 | goto out_putf; |
| 351 | } |
| 352 | |
| 353 | current->flags |= PF_SYNCWRITE; |
| 354 | ret = filemap_fdatawrite(mapping); |
| 355 | |
| 356 | /* |
| 357 | * We need to protect against concurrent writers, |
| 358 | * which could cause livelocks in fsync_buffers_list |
| 359 | */ |
| 360 | down(&mapping->host->i_sem); |
| 361 | err = file->f_op->fsync(file, file->f_dentry, 0); |
| 362 | if (!ret) |
| 363 | ret = err; |
| 364 | up(&mapping->host->i_sem); |
| 365 | err = filemap_fdatawait(mapping); |
| 366 | if (!ret) |
| 367 | ret = err; |
| 368 | current->flags &= ~PF_SYNCWRITE; |
| 369 | |
| 370 | out_putf: |
| 371 | fput(file); |
| 372 | out: |
| 373 | return ret; |
| 374 | } |
| 375 | |
| 376 | asmlinkage long sys_fdatasync(unsigned int fd) |
| 377 | { |
| 378 | struct file * file; |
| 379 | struct address_space *mapping; |
| 380 | int ret, err; |
| 381 | |
| 382 | ret = -EBADF; |
| 383 | file = fget(fd); |
| 384 | if (!file) |
| 385 | goto out; |
| 386 | |
| 387 | ret = -EINVAL; |
| 388 | if (!file->f_op || !file->f_op->fsync) |
| 389 | goto out_putf; |
| 390 | |
| 391 | mapping = file->f_mapping; |
| 392 | |
| 393 | current->flags |= PF_SYNCWRITE; |
| 394 | ret = filemap_fdatawrite(mapping); |
| 395 | down(&mapping->host->i_sem); |
| 396 | err = file->f_op->fsync(file, file->f_dentry, 1); |
| 397 | if (!ret) |
| 398 | ret = err; |
| 399 | up(&mapping->host->i_sem); |
| 400 | err = filemap_fdatawait(mapping); |
| 401 | if (!ret) |
| 402 | ret = err; |
| 403 | current->flags &= ~PF_SYNCWRITE; |
| 404 | |
| 405 | out_putf: |
| 406 | fput(file); |
| 407 | out: |
| 408 | return ret; |
| 409 | } |
| 410 | |
| 411 | /* |
| 412 | * Various filesystems appear to want __find_get_block to be non-blocking. |
| 413 | * But it's the page lock which protects the buffers. To get around this, |
| 414 | * we get exclusion from try_to_free_buffers with the blockdev mapping's |
| 415 | * private_lock. |
| 416 | * |
| 417 | * Hack idea: for the blockdev mapping, i_bufferlist_lock contention |
| 418 | * may be quite high. This code could TryLock the page, and if that |
| 419 | * succeeds, there is no need to take private_lock. (But if |
| 420 | * private_lock is contended then so is mapping->tree_lock). |
| 421 | */ |
| 422 | static struct buffer_head * |
| 423 | __find_get_block_slow(struct block_device *bdev, sector_t block, int unused) |
| 424 | { |
| 425 | struct inode *bd_inode = bdev->bd_inode; |
| 426 | struct address_space *bd_mapping = bd_inode->i_mapping; |
| 427 | struct buffer_head *ret = NULL; |
| 428 | pgoff_t index; |
| 429 | struct buffer_head *bh; |
| 430 | struct buffer_head *head; |
| 431 | struct page *page; |
| 432 | int all_mapped = 1; |
| 433 | |
| 434 | index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits); |
| 435 | page = find_get_page(bd_mapping, index); |
| 436 | if (!page) |
| 437 | goto out; |
| 438 | |
| 439 | spin_lock(&bd_mapping->private_lock); |
| 440 | if (!page_has_buffers(page)) |
| 441 | goto out_unlock; |
| 442 | head = page_buffers(page); |
| 443 | bh = head; |
| 444 | do { |
| 445 | if (bh->b_blocknr == block) { |
| 446 | ret = bh; |
| 447 | get_bh(bh); |
| 448 | goto out_unlock; |
| 449 | } |
| 450 | if (!buffer_mapped(bh)) |
| 451 | all_mapped = 0; |
| 452 | bh = bh->b_this_page; |
| 453 | } while (bh != head); |
| 454 | |
| 455 | /* we might be here because some of the buffers on this page are |
| 456 | * not mapped. This is due to various races between |
| 457 | * file io on the block device and getblk. It gets dealt with |
| 458 | * elsewhere, don't buffer_error if we had some unmapped buffers |
| 459 | */ |
| 460 | if (all_mapped) { |
| 461 | printk("__find_get_block_slow() failed. " |
| 462 | "block=%llu, b_blocknr=%llu\n", |
| 463 | (unsigned long long)block, (unsigned long long)bh->b_blocknr); |
| 464 | printk("b_state=0x%08lx, b_size=%u\n", bh->b_state, bh->b_size); |
| 465 | printk("device blocksize: %d\n", 1 << bd_inode->i_blkbits); |
| 466 | } |
| 467 | out_unlock: |
| 468 | spin_unlock(&bd_mapping->private_lock); |
| 469 | page_cache_release(page); |
| 470 | out: |
| 471 | return ret; |
| 472 | } |
| 473 | |
| 474 | /* If invalidate_buffers() will trash dirty buffers, it means some kind |
| 475 | of fs corruption is going on. Trashing dirty data always imply losing |
| 476 | information that was supposed to be just stored on the physical layer |
| 477 | by the user. |
| 478 | |
| 479 | Thus invalidate_buffers in general usage is not allwowed to trash |
| 480 | dirty buffers. For example ioctl(FLSBLKBUF) expects dirty data to |
| 481 | be preserved. These buffers are simply skipped. |
| 482 | |
| 483 | We also skip buffers which are still in use. For example this can |
| 484 | happen if a userspace program is reading the block device. |
| 485 | |
| 486 | NOTE: In the case where the user removed a removable-media-disk even if |
| 487 | there's still dirty data not synced on disk (due a bug in the device driver |
| 488 | or due an error of the user), by not destroying the dirty buffers we could |
| 489 | generate corruption also on the next media inserted, thus a parameter is |
| 490 | necessary to handle this case in the most safe way possible (trying |
| 491 | to not corrupt also the new disk inserted with the data belonging to |
| 492 | the old now corrupted disk). Also for the ramdisk the natural thing |
| 493 | to do in order to release the ramdisk memory is to destroy dirty buffers. |
| 494 | |
| 495 | These are two special cases. Normal usage imply the device driver |
| 496 | to issue a sync on the device (without waiting I/O completion) and |
| 497 | then an invalidate_buffers call that doesn't trash dirty buffers. |
| 498 | |
| 499 | For handling cache coherency with the blkdev pagecache the 'update' case |
| 500 | is been introduced. It is needed to re-read from disk any pinned |
| 501 | buffer. NOTE: re-reading from disk is destructive so we can do it only |
| 502 | when we assume nobody is changing the buffercache under our I/O and when |
| 503 | we think the disk contains more recent information than the buffercache. |
| 504 | The update == 1 pass marks the buffers we need to update, the update == 2 |
| 505 | pass does the actual I/O. */ |
| 506 | void invalidate_bdev(struct block_device *bdev, int destroy_dirty_buffers) |
| 507 | { |
| 508 | invalidate_bh_lrus(); |
| 509 | /* |
| 510 | * FIXME: what about destroy_dirty_buffers? |
| 511 | * We really want to use invalidate_inode_pages2() for |
| 512 | * that, but not until that's cleaned up. |
| 513 | */ |
| 514 | invalidate_inode_pages(bdev->bd_inode->i_mapping); |
| 515 | } |
| 516 | |
| 517 | /* |
| 518 | * Kick pdflush then try to free up some ZONE_NORMAL memory. |
| 519 | */ |
| 520 | static void free_more_memory(void) |
| 521 | { |
| 522 | struct zone **zones; |
| 523 | pg_data_t *pgdat; |
| 524 | |
| 525 | wakeup_bdflush(1024); |
| 526 | yield(); |
| 527 | |
| 528 | for_each_pgdat(pgdat) { |
| 529 | zones = pgdat->node_zonelists[GFP_NOFS&GFP_ZONEMASK].zones; |
| 530 | if (*zones) |
Darren Hart | 1ad539b | 2005-06-21 17:14:53 -0700 | [diff] [blame] | 531 | try_to_free_pages(zones, GFP_NOFS); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 532 | } |
| 533 | } |
| 534 | |
| 535 | /* |
| 536 | * I/O completion handler for block_read_full_page() - pages |
| 537 | * which come unlocked at the end of I/O. |
| 538 | */ |
| 539 | static void end_buffer_async_read(struct buffer_head *bh, int uptodate) |
| 540 | { |
| 541 | static DEFINE_SPINLOCK(page_uptodate_lock); |
| 542 | unsigned long flags; |
| 543 | struct buffer_head *tmp; |
| 544 | struct page *page; |
| 545 | int page_uptodate = 1; |
| 546 | |
| 547 | BUG_ON(!buffer_async_read(bh)); |
| 548 | |
| 549 | page = bh->b_page; |
| 550 | if (uptodate) { |
| 551 | set_buffer_uptodate(bh); |
| 552 | } else { |
| 553 | clear_buffer_uptodate(bh); |
| 554 | if (printk_ratelimit()) |
| 555 | buffer_io_error(bh); |
| 556 | SetPageError(page); |
| 557 | } |
| 558 | |
| 559 | /* |
| 560 | * Be _very_ careful from here on. Bad things can happen if |
| 561 | * two buffer heads end IO at almost the same time and both |
| 562 | * decide that the page is now completely done. |
| 563 | */ |
| 564 | spin_lock_irqsave(&page_uptodate_lock, flags); |
| 565 | clear_buffer_async_read(bh); |
| 566 | unlock_buffer(bh); |
| 567 | tmp = bh; |
| 568 | do { |
| 569 | if (!buffer_uptodate(tmp)) |
| 570 | page_uptodate = 0; |
| 571 | if (buffer_async_read(tmp)) { |
| 572 | BUG_ON(!buffer_locked(tmp)); |
| 573 | goto still_busy; |
| 574 | } |
| 575 | tmp = tmp->b_this_page; |
| 576 | } while (tmp != bh); |
| 577 | spin_unlock_irqrestore(&page_uptodate_lock, flags); |
| 578 | |
| 579 | /* |
| 580 | * If none of the buffers had errors and they are all |
| 581 | * uptodate then we can set the page uptodate. |
| 582 | */ |
| 583 | if (page_uptodate && !PageError(page)) |
| 584 | SetPageUptodate(page); |
| 585 | unlock_page(page); |
| 586 | return; |
| 587 | |
| 588 | still_busy: |
| 589 | spin_unlock_irqrestore(&page_uptodate_lock, flags); |
| 590 | return; |
| 591 | } |
| 592 | |
| 593 | /* |
| 594 | * Completion handler for block_write_full_page() - pages which are unlocked |
| 595 | * during I/O, and which have PageWriteback cleared upon I/O completion. |
| 596 | */ |
| 597 | void end_buffer_async_write(struct buffer_head *bh, int uptodate) |
| 598 | { |
| 599 | char b[BDEVNAME_SIZE]; |
| 600 | static DEFINE_SPINLOCK(page_uptodate_lock); |
| 601 | unsigned long flags; |
| 602 | struct buffer_head *tmp; |
| 603 | struct page *page; |
| 604 | |
| 605 | BUG_ON(!buffer_async_write(bh)); |
| 606 | |
| 607 | page = bh->b_page; |
| 608 | if (uptodate) { |
| 609 | set_buffer_uptodate(bh); |
| 610 | } else { |
| 611 | if (printk_ratelimit()) { |
| 612 | buffer_io_error(bh); |
| 613 | printk(KERN_WARNING "lost page write due to " |
| 614 | "I/O error on %s\n", |
| 615 | bdevname(bh->b_bdev, b)); |
| 616 | } |
| 617 | set_bit(AS_EIO, &page->mapping->flags); |
| 618 | clear_buffer_uptodate(bh); |
| 619 | SetPageError(page); |
| 620 | } |
| 621 | |
| 622 | spin_lock_irqsave(&page_uptodate_lock, flags); |
| 623 | clear_buffer_async_write(bh); |
| 624 | unlock_buffer(bh); |
| 625 | tmp = bh->b_this_page; |
| 626 | while (tmp != bh) { |
| 627 | if (buffer_async_write(tmp)) { |
| 628 | BUG_ON(!buffer_locked(tmp)); |
| 629 | goto still_busy; |
| 630 | } |
| 631 | tmp = tmp->b_this_page; |
| 632 | } |
| 633 | spin_unlock_irqrestore(&page_uptodate_lock, flags); |
| 634 | end_page_writeback(page); |
| 635 | return; |
| 636 | |
| 637 | still_busy: |
| 638 | spin_unlock_irqrestore(&page_uptodate_lock, flags); |
| 639 | return; |
| 640 | } |
| 641 | |
| 642 | /* |
| 643 | * If a page's buffers are under async readin (end_buffer_async_read |
| 644 | * completion) then there is a possibility that another thread of |
| 645 | * control could lock one of the buffers after it has completed |
| 646 | * but while some of the other buffers have not completed. This |
| 647 | * locked buffer would confuse end_buffer_async_read() into not unlocking |
| 648 | * the page. So the absence of BH_Async_Read tells end_buffer_async_read() |
| 649 | * that this buffer is not under async I/O. |
| 650 | * |
| 651 | * The page comes unlocked when it has no locked buffer_async buffers |
| 652 | * left. |
| 653 | * |
| 654 | * PageLocked prevents anyone starting new async I/O reads any of |
| 655 | * the buffers. |
| 656 | * |
| 657 | * PageWriteback is used to prevent simultaneous writeout of the same |
| 658 | * page. |
| 659 | * |
| 660 | * PageLocked prevents anyone from starting writeback of a page which is |
| 661 | * under read I/O (PageWriteback is only ever set against a locked page). |
| 662 | */ |
| 663 | static void mark_buffer_async_read(struct buffer_head *bh) |
| 664 | { |
| 665 | bh->b_end_io = end_buffer_async_read; |
| 666 | set_buffer_async_read(bh); |
| 667 | } |
| 668 | |
| 669 | void mark_buffer_async_write(struct buffer_head *bh) |
| 670 | { |
| 671 | bh->b_end_io = end_buffer_async_write; |
| 672 | set_buffer_async_write(bh); |
| 673 | } |
| 674 | EXPORT_SYMBOL(mark_buffer_async_write); |
| 675 | |
| 676 | |
| 677 | /* |
| 678 | * fs/buffer.c contains helper functions for buffer-backed address space's |
| 679 | * fsync functions. A common requirement for buffer-based filesystems is |
| 680 | * that certain data from the backing blockdev needs to be written out for |
| 681 | * a successful fsync(). For example, ext2 indirect blocks need to be |
| 682 | * written back and waited upon before fsync() returns. |
| 683 | * |
| 684 | * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(), |
| 685 | * inode_has_buffers() and invalidate_inode_buffers() are provided for the |
| 686 | * management of a list of dependent buffers at ->i_mapping->private_list. |
| 687 | * |
| 688 | * Locking is a little subtle: try_to_free_buffers() will remove buffers |
| 689 | * from their controlling inode's queue when they are being freed. But |
| 690 | * try_to_free_buffers() will be operating against the *blockdev* mapping |
| 691 | * at the time, not against the S_ISREG file which depends on those buffers. |
| 692 | * So the locking for private_list is via the private_lock in the address_space |
| 693 | * which backs the buffers. Which is different from the address_space |
| 694 | * against which the buffers are listed. So for a particular address_space, |
| 695 | * mapping->private_lock does *not* protect mapping->private_list! In fact, |
| 696 | * mapping->private_list will always be protected by the backing blockdev's |
| 697 | * ->private_lock. |
| 698 | * |
| 699 | * Which introduces a requirement: all buffers on an address_space's |
| 700 | * ->private_list must be from the same address_space: the blockdev's. |
| 701 | * |
| 702 | * address_spaces which do not place buffers at ->private_list via these |
| 703 | * utility functions are free to use private_lock and private_list for |
| 704 | * whatever they want. The only requirement is that list_empty(private_list) |
| 705 | * be true at clear_inode() time. |
| 706 | * |
| 707 | * FIXME: clear_inode should not call invalidate_inode_buffers(). The |
| 708 | * filesystems should do that. invalidate_inode_buffers() should just go |
| 709 | * BUG_ON(!list_empty). |
| 710 | * |
| 711 | * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should |
| 712 | * take an address_space, not an inode. And it should be called |
| 713 | * mark_buffer_dirty_fsync() to clearly define why those buffers are being |
| 714 | * queued up. |
| 715 | * |
| 716 | * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the |
| 717 | * list if it is already on a list. Because if the buffer is on a list, |
| 718 | * it *must* already be on the right one. If not, the filesystem is being |
| 719 | * silly. This will save a ton of locking. But first we have to ensure |
| 720 | * that buffers are taken *off* the old inode's list when they are freed |
| 721 | * (presumably in truncate). That requires careful auditing of all |
| 722 | * filesystems (do it inside bforget()). It could also be done by bringing |
| 723 | * b_inode back. |
| 724 | */ |
| 725 | |
| 726 | /* |
| 727 | * The buffer's backing address_space's private_lock must be held |
| 728 | */ |
| 729 | static inline void __remove_assoc_queue(struct buffer_head *bh) |
| 730 | { |
| 731 | list_del_init(&bh->b_assoc_buffers); |
| 732 | } |
| 733 | |
| 734 | int inode_has_buffers(struct inode *inode) |
| 735 | { |
| 736 | return !list_empty(&inode->i_data.private_list); |
| 737 | } |
| 738 | |
| 739 | /* |
| 740 | * osync is designed to support O_SYNC io. It waits synchronously for |
| 741 | * all already-submitted IO to complete, but does not queue any new |
| 742 | * writes to the disk. |
| 743 | * |
| 744 | * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as |
| 745 | * you dirty the buffers, and then use osync_inode_buffers to wait for |
| 746 | * completion. Any other dirty buffers which are not yet queued for |
| 747 | * write will not be flushed to disk by the osync. |
| 748 | */ |
| 749 | static int osync_buffers_list(spinlock_t *lock, struct list_head *list) |
| 750 | { |
| 751 | struct buffer_head *bh; |
| 752 | struct list_head *p; |
| 753 | int err = 0; |
| 754 | |
| 755 | spin_lock(lock); |
| 756 | repeat: |
| 757 | list_for_each_prev(p, list) { |
| 758 | bh = BH_ENTRY(p); |
| 759 | if (buffer_locked(bh)) { |
| 760 | get_bh(bh); |
| 761 | spin_unlock(lock); |
| 762 | wait_on_buffer(bh); |
| 763 | if (!buffer_uptodate(bh)) |
| 764 | err = -EIO; |
| 765 | brelse(bh); |
| 766 | spin_lock(lock); |
| 767 | goto repeat; |
| 768 | } |
| 769 | } |
| 770 | spin_unlock(lock); |
| 771 | return err; |
| 772 | } |
| 773 | |
| 774 | /** |
| 775 | * sync_mapping_buffers - write out and wait upon a mapping's "associated" |
| 776 | * buffers |
Martin Waitz | 67be2dd | 2005-05-01 08:59:26 -0700 | [diff] [blame] | 777 | * @mapping: the mapping which wants those buffers written |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 778 | * |
| 779 | * Starts I/O against the buffers at mapping->private_list, and waits upon |
| 780 | * that I/O. |
| 781 | * |
Martin Waitz | 67be2dd | 2005-05-01 08:59:26 -0700 | [diff] [blame] | 782 | * Basically, this is a convenience function for fsync(). |
| 783 | * @mapping is a file or directory which needs those buffers to be written for |
| 784 | * a successful fsync(). |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 785 | */ |
| 786 | int sync_mapping_buffers(struct address_space *mapping) |
| 787 | { |
| 788 | struct address_space *buffer_mapping = mapping->assoc_mapping; |
| 789 | |
| 790 | if (buffer_mapping == NULL || list_empty(&mapping->private_list)) |
| 791 | return 0; |
| 792 | |
| 793 | return fsync_buffers_list(&buffer_mapping->private_lock, |
| 794 | &mapping->private_list); |
| 795 | } |
| 796 | EXPORT_SYMBOL(sync_mapping_buffers); |
| 797 | |
| 798 | /* |
| 799 | * Called when we've recently written block `bblock', and it is known that |
| 800 | * `bblock' was for a buffer_boundary() buffer. This means that the block at |
| 801 | * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's |
| 802 | * dirty, schedule it for IO. So that indirects merge nicely with their data. |
| 803 | */ |
| 804 | void write_boundary_block(struct block_device *bdev, |
| 805 | sector_t bblock, unsigned blocksize) |
| 806 | { |
| 807 | struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize); |
| 808 | if (bh) { |
| 809 | if (buffer_dirty(bh)) |
| 810 | ll_rw_block(WRITE, 1, &bh); |
| 811 | put_bh(bh); |
| 812 | } |
| 813 | } |
| 814 | |
| 815 | void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode) |
| 816 | { |
| 817 | struct address_space *mapping = inode->i_mapping; |
| 818 | struct address_space *buffer_mapping = bh->b_page->mapping; |
| 819 | |
| 820 | mark_buffer_dirty(bh); |
| 821 | if (!mapping->assoc_mapping) { |
| 822 | mapping->assoc_mapping = buffer_mapping; |
| 823 | } else { |
| 824 | if (mapping->assoc_mapping != buffer_mapping) |
| 825 | BUG(); |
| 826 | } |
| 827 | if (list_empty(&bh->b_assoc_buffers)) { |
| 828 | spin_lock(&buffer_mapping->private_lock); |
| 829 | list_move_tail(&bh->b_assoc_buffers, |
| 830 | &mapping->private_list); |
| 831 | spin_unlock(&buffer_mapping->private_lock); |
| 832 | } |
| 833 | } |
| 834 | EXPORT_SYMBOL(mark_buffer_dirty_inode); |
| 835 | |
| 836 | /* |
| 837 | * Add a page to the dirty page list. |
| 838 | * |
| 839 | * It is a sad fact of life that this function is called from several places |
| 840 | * deeply under spinlocking. It may not sleep. |
| 841 | * |
| 842 | * If the page has buffers, the uptodate buffers are set dirty, to preserve |
| 843 | * dirty-state coherency between the page and the buffers. It the page does |
| 844 | * not have buffers then when they are later attached they will all be set |
| 845 | * dirty. |
| 846 | * |
| 847 | * The buffers are dirtied before the page is dirtied. There's a small race |
| 848 | * window in which a writepage caller may see the page cleanness but not the |
| 849 | * buffer dirtiness. That's fine. If this code were to set the page dirty |
| 850 | * before the buffers, a concurrent writepage caller could clear the page dirty |
| 851 | * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean |
| 852 | * page on the dirty page list. |
| 853 | * |
| 854 | * We use private_lock to lock against try_to_free_buffers while using the |
| 855 | * page's buffer list. Also use this to protect against clean buffers being |
| 856 | * added to the page after it was set dirty. |
| 857 | * |
| 858 | * FIXME: may need to call ->reservepage here as well. That's rather up to the |
| 859 | * address_space though. |
| 860 | */ |
| 861 | int __set_page_dirty_buffers(struct page *page) |
| 862 | { |
| 863 | struct address_space * const mapping = page->mapping; |
| 864 | |
| 865 | spin_lock(&mapping->private_lock); |
| 866 | if (page_has_buffers(page)) { |
| 867 | struct buffer_head *head = page_buffers(page); |
| 868 | struct buffer_head *bh = head; |
| 869 | |
| 870 | do { |
| 871 | set_buffer_dirty(bh); |
| 872 | bh = bh->b_this_page; |
| 873 | } while (bh != head); |
| 874 | } |
| 875 | spin_unlock(&mapping->private_lock); |
| 876 | |
| 877 | if (!TestSetPageDirty(page)) { |
| 878 | write_lock_irq(&mapping->tree_lock); |
| 879 | if (page->mapping) { /* Race with truncate? */ |
| 880 | if (mapping_cap_account_dirty(mapping)) |
| 881 | inc_page_state(nr_dirty); |
| 882 | radix_tree_tag_set(&mapping->page_tree, |
| 883 | page_index(page), |
| 884 | PAGECACHE_TAG_DIRTY); |
| 885 | } |
| 886 | write_unlock_irq(&mapping->tree_lock); |
| 887 | __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); |
| 888 | } |
| 889 | |
| 890 | return 0; |
| 891 | } |
| 892 | EXPORT_SYMBOL(__set_page_dirty_buffers); |
| 893 | |
| 894 | /* |
| 895 | * Write out and wait upon a list of buffers. |
| 896 | * |
| 897 | * We have conflicting pressures: we want to make sure that all |
| 898 | * initially dirty buffers get waited on, but that any subsequently |
| 899 | * dirtied buffers don't. After all, we don't want fsync to last |
| 900 | * forever if somebody is actively writing to the file. |
| 901 | * |
| 902 | * Do this in two main stages: first we copy dirty buffers to a |
| 903 | * temporary inode list, queueing the writes as we go. Then we clean |
| 904 | * up, waiting for those writes to complete. |
| 905 | * |
| 906 | * During this second stage, any subsequent updates to the file may end |
| 907 | * up refiling the buffer on the original inode's dirty list again, so |
| 908 | * there is a chance we will end up with a buffer queued for write but |
| 909 | * not yet completed on that list. So, as a final cleanup we go through |
| 910 | * the osync code to catch these locked, dirty buffers without requeuing |
| 911 | * any newly dirty buffers for write. |
| 912 | */ |
| 913 | static int fsync_buffers_list(spinlock_t *lock, struct list_head *list) |
| 914 | { |
| 915 | struct buffer_head *bh; |
| 916 | struct list_head tmp; |
| 917 | int err = 0, err2; |
| 918 | |
| 919 | INIT_LIST_HEAD(&tmp); |
| 920 | |
| 921 | spin_lock(lock); |
| 922 | while (!list_empty(list)) { |
| 923 | bh = BH_ENTRY(list->next); |
| 924 | list_del_init(&bh->b_assoc_buffers); |
| 925 | if (buffer_dirty(bh) || buffer_locked(bh)) { |
| 926 | list_add(&bh->b_assoc_buffers, &tmp); |
| 927 | if (buffer_dirty(bh)) { |
| 928 | get_bh(bh); |
| 929 | spin_unlock(lock); |
| 930 | /* |
| 931 | * Ensure any pending I/O completes so that |
| 932 | * ll_rw_block() actually writes the current |
| 933 | * contents - it is a noop if I/O is still in |
| 934 | * flight on potentially older contents. |
| 935 | */ |
| 936 | wait_on_buffer(bh); |
| 937 | ll_rw_block(WRITE, 1, &bh); |
| 938 | brelse(bh); |
| 939 | spin_lock(lock); |
| 940 | } |
| 941 | } |
| 942 | } |
| 943 | |
| 944 | while (!list_empty(&tmp)) { |
| 945 | bh = BH_ENTRY(tmp.prev); |
| 946 | __remove_assoc_queue(bh); |
| 947 | get_bh(bh); |
| 948 | spin_unlock(lock); |
| 949 | wait_on_buffer(bh); |
| 950 | if (!buffer_uptodate(bh)) |
| 951 | err = -EIO; |
| 952 | brelse(bh); |
| 953 | spin_lock(lock); |
| 954 | } |
| 955 | |
| 956 | spin_unlock(lock); |
| 957 | err2 = osync_buffers_list(lock, list); |
| 958 | if (err) |
| 959 | return err; |
| 960 | else |
| 961 | return err2; |
| 962 | } |
| 963 | |
| 964 | /* |
| 965 | * Invalidate any and all dirty buffers on a given inode. We are |
| 966 | * probably unmounting the fs, but that doesn't mean we have already |
| 967 | * done a sync(). Just drop the buffers from the inode list. |
| 968 | * |
| 969 | * NOTE: we take the inode's blockdev's mapping's private_lock. Which |
| 970 | * assumes that all the buffers are against the blockdev. Not true |
| 971 | * for reiserfs. |
| 972 | */ |
| 973 | void invalidate_inode_buffers(struct inode *inode) |
| 974 | { |
| 975 | if (inode_has_buffers(inode)) { |
| 976 | struct address_space *mapping = &inode->i_data; |
| 977 | struct list_head *list = &mapping->private_list; |
| 978 | struct address_space *buffer_mapping = mapping->assoc_mapping; |
| 979 | |
| 980 | spin_lock(&buffer_mapping->private_lock); |
| 981 | while (!list_empty(list)) |
| 982 | __remove_assoc_queue(BH_ENTRY(list->next)); |
| 983 | spin_unlock(&buffer_mapping->private_lock); |
| 984 | } |
| 985 | } |
| 986 | |
| 987 | /* |
| 988 | * Remove any clean buffers from the inode's buffer list. This is called |
| 989 | * when we're trying to free the inode itself. Those buffers can pin it. |
| 990 | * |
| 991 | * Returns true if all buffers were removed. |
| 992 | */ |
| 993 | int remove_inode_buffers(struct inode *inode) |
| 994 | { |
| 995 | int ret = 1; |
| 996 | |
| 997 | if (inode_has_buffers(inode)) { |
| 998 | struct address_space *mapping = &inode->i_data; |
| 999 | struct list_head *list = &mapping->private_list; |
| 1000 | struct address_space *buffer_mapping = mapping->assoc_mapping; |
| 1001 | |
| 1002 | spin_lock(&buffer_mapping->private_lock); |
| 1003 | while (!list_empty(list)) { |
| 1004 | struct buffer_head *bh = BH_ENTRY(list->next); |
| 1005 | if (buffer_dirty(bh)) { |
| 1006 | ret = 0; |
| 1007 | break; |
| 1008 | } |
| 1009 | __remove_assoc_queue(bh); |
| 1010 | } |
| 1011 | spin_unlock(&buffer_mapping->private_lock); |
| 1012 | } |
| 1013 | return ret; |
| 1014 | } |
| 1015 | |
| 1016 | /* |
| 1017 | * Create the appropriate buffers when given a page for data area and |
| 1018 | * the size of each buffer.. Use the bh->b_this_page linked list to |
| 1019 | * follow the buffers created. Return NULL if unable to create more |
| 1020 | * buffers. |
| 1021 | * |
| 1022 | * The retry flag is used to differentiate async IO (paging, swapping) |
| 1023 | * which may not fail from ordinary buffer allocations. |
| 1024 | */ |
| 1025 | struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, |
| 1026 | int retry) |
| 1027 | { |
| 1028 | struct buffer_head *bh, *head; |
| 1029 | long offset; |
| 1030 | |
| 1031 | try_again: |
| 1032 | head = NULL; |
| 1033 | offset = PAGE_SIZE; |
| 1034 | while ((offset -= size) >= 0) { |
| 1035 | bh = alloc_buffer_head(GFP_NOFS); |
| 1036 | if (!bh) |
| 1037 | goto no_grow; |
| 1038 | |
| 1039 | bh->b_bdev = NULL; |
| 1040 | bh->b_this_page = head; |
| 1041 | bh->b_blocknr = -1; |
| 1042 | head = bh; |
| 1043 | |
| 1044 | bh->b_state = 0; |
| 1045 | atomic_set(&bh->b_count, 0); |
| 1046 | bh->b_size = size; |
| 1047 | |
| 1048 | /* Link the buffer to its page */ |
| 1049 | set_bh_page(bh, page, offset); |
| 1050 | |
| 1051 | bh->b_end_io = NULL; |
| 1052 | } |
| 1053 | return head; |
| 1054 | /* |
| 1055 | * In case anything failed, we just free everything we got. |
| 1056 | */ |
| 1057 | no_grow: |
| 1058 | if (head) { |
| 1059 | do { |
| 1060 | bh = head; |
| 1061 | head = head->b_this_page; |
| 1062 | free_buffer_head(bh); |
| 1063 | } while (head); |
| 1064 | } |
| 1065 | |
| 1066 | /* |
| 1067 | * Return failure for non-async IO requests. Async IO requests |
| 1068 | * are not allowed to fail, so we have to wait until buffer heads |
| 1069 | * become available. But we don't want tasks sleeping with |
| 1070 | * partially complete buffers, so all were released above. |
| 1071 | */ |
| 1072 | if (!retry) |
| 1073 | return NULL; |
| 1074 | |
| 1075 | /* We're _really_ low on memory. Now we just |
| 1076 | * wait for old buffer heads to become free due to |
| 1077 | * finishing IO. Since this is an async request and |
| 1078 | * the reserve list is empty, we're sure there are |
| 1079 | * async buffer heads in use. |
| 1080 | */ |
| 1081 | free_more_memory(); |
| 1082 | goto try_again; |
| 1083 | } |
| 1084 | EXPORT_SYMBOL_GPL(alloc_page_buffers); |
| 1085 | |
| 1086 | static inline void |
| 1087 | link_dev_buffers(struct page *page, struct buffer_head *head) |
| 1088 | { |
| 1089 | struct buffer_head *bh, *tail; |
| 1090 | |
| 1091 | bh = head; |
| 1092 | do { |
| 1093 | tail = bh; |
| 1094 | bh = bh->b_this_page; |
| 1095 | } while (bh); |
| 1096 | tail->b_this_page = head; |
| 1097 | attach_page_buffers(page, head); |
| 1098 | } |
| 1099 | |
| 1100 | /* |
| 1101 | * Initialise the state of a blockdev page's buffers. |
| 1102 | */ |
| 1103 | static void |
| 1104 | init_page_buffers(struct page *page, struct block_device *bdev, |
| 1105 | sector_t block, int size) |
| 1106 | { |
| 1107 | struct buffer_head *head = page_buffers(page); |
| 1108 | struct buffer_head *bh = head; |
| 1109 | int uptodate = PageUptodate(page); |
| 1110 | |
| 1111 | do { |
| 1112 | if (!buffer_mapped(bh)) { |
| 1113 | init_buffer(bh, NULL, NULL); |
| 1114 | bh->b_bdev = bdev; |
| 1115 | bh->b_blocknr = block; |
| 1116 | if (uptodate) |
| 1117 | set_buffer_uptodate(bh); |
| 1118 | set_buffer_mapped(bh); |
| 1119 | } |
| 1120 | block++; |
| 1121 | bh = bh->b_this_page; |
| 1122 | } while (bh != head); |
| 1123 | } |
| 1124 | |
| 1125 | /* |
| 1126 | * Create the page-cache page that contains the requested block. |
| 1127 | * |
| 1128 | * This is user purely for blockdev mappings. |
| 1129 | */ |
| 1130 | static struct page * |
| 1131 | grow_dev_page(struct block_device *bdev, sector_t block, |
| 1132 | pgoff_t index, int size) |
| 1133 | { |
| 1134 | struct inode *inode = bdev->bd_inode; |
| 1135 | struct page *page; |
| 1136 | struct buffer_head *bh; |
| 1137 | |
| 1138 | page = find_or_create_page(inode->i_mapping, index, GFP_NOFS); |
| 1139 | if (!page) |
| 1140 | return NULL; |
| 1141 | |
| 1142 | if (!PageLocked(page)) |
| 1143 | BUG(); |
| 1144 | |
| 1145 | if (page_has_buffers(page)) { |
| 1146 | bh = page_buffers(page); |
| 1147 | if (bh->b_size == size) { |
| 1148 | init_page_buffers(page, bdev, block, size); |
| 1149 | return page; |
| 1150 | } |
| 1151 | if (!try_to_free_buffers(page)) |
| 1152 | goto failed; |
| 1153 | } |
| 1154 | |
| 1155 | /* |
| 1156 | * Allocate some buffers for this page |
| 1157 | */ |
| 1158 | bh = alloc_page_buffers(page, size, 0); |
| 1159 | if (!bh) |
| 1160 | goto failed; |
| 1161 | |
| 1162 | /* |
| 1163 | * Link the page to the buffers and initialise them. Take the |
| 1164 | * lock to be atomic wrt __find_get_block(), which does not |
| 1165 | * run under the page lock. |
| 1166 | */ |
| 1167 | spin_lock(&inode->i_mapping->private_lock); |
| 1168 | link_dev_buffers(page, bh); |
| 1169 | init_page_buffers(page, bdev, block, size); |
| 1170 | spin_unlock(&inode->i_mapping->private_lock); |
| 1171 | return page; |
| 1172 | |
| 1173 | failed: |
| 1174 | BUG(); |
| 1175 | unlock_page(page); |
| 1176 | page_cache_release(page); |
| 1177 | return NULL; |
| 1178 | } |
| 1179 | |
| 1180 | /* |
| 1181 | * Create buffers for the specified block device block's page. If |
| 1182 | * that page was dirty, the buffers are set dirty also. |
| 1183 | * |
| 1184 | * Except that's a bug. Attaching dirty buffers to a dirty |
| 1185 | * blockdev's page can result in filesystem corruption, because |
| 1186 | * some of those buffers may be aliases of filesystem data. |
| 1187 | * grow_dev_page() will go BUG() if this happens. |
| 1188 | */ |
| 1189 | static inline int |
| 1190 | grow_buffers(struct block_device *bdev, sector_t block, int size) |
| 1191 | { |
| 1192 | struct page *page; |
| 1193 | pgoff_t index; |
| 1194 | int sizebits; |
| 1195 | |
| 1196 | sizebits = -1; |
| 1197 | do { |
| 1198 | sizebits++; |
| 1199 | } while ((size << sizebits) < PAGE_SIZE); |
| 1200 | |
| 1201 | index = block >> sizebits; |
| 1202 | block = index << sizebits; |
| 1203 | |
| 1204 | /* Create a page with the proper size buffers.. */ |
| 1205 | page = grow_dev_page(bdev, block, index, size); |
| 1206 | if (!page) |
| 1207 | return 0; |
| 1208 | unlock_page(page); |
| 1209 | page_cache_release(page); |
| 1210 | return 1; |
| 1211 | } |
| 1212 | |
Adrian Bunk | 75c96f8 | 2005-05-05 16:16:09 -0700 | [diff] [blame] | 1213 | static struct buffer_head * |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1214 | __getblk_slow(struct block_device *bdev, sector_t block, int size) |
| 1215 | { |
| 1216 | /* Size must be multiple of hard sectorsize */ |
| 1217 | if (unlikely(size & (bdev_hardsect_size(bdev)-1) || |
| 1218 | (size < 512 || size > PAGE_SIZE))) { |
| 1219 | printk(KERN_ERR "getblk(): invalid block size %d requested\n", |
| 1220 | size); |
| 1221 | printk(KERN_ERR "hardsect size: %d\n", |
| 1222 | bdev_hardsect_size(bdev)); |
| 1223 | |
| 1224 | dump_stack(); |
| 1225 | return NULL; |
| 1226 | } |
| 1227 | |
| 1228 | for (;;) { |
| 1229 | struct buffer_head * bh; |
| 1230 | |
| 1231 | bh = __find_get_block(bdev, block, size); |
| 1232 | if (bh) |
| 1233 | return bh; |
| 1234 | |
| 1235 | if (!grow_buffers(bdev, block, size)) |
| 1236 | free_more_memory(); |
| 1237 | } |
| 1238 | } |
| 1239 | |
| 1240 | /* |
| 1241 | * The relationship between dirty buffers and dirty pages: |
| 1242 | * |
| 1243 | * Whenever a page has any dirty buffers, the page's dirty bit is set, and |
| 1244 | * the page is tagged dirty in its radix tree. |
| 1245 | * |
| 1246 | * At all times, the dirtiness of the buffers represents the dirtiness of |
| 1247 | * subsections of the page. If the page has buffers, the page dirty bit is |
| 1248 | * merely a hint about the true dirty state. |
| 1249 | * |
| 1250 | * When a page is set dirty in its entirety, all its buffers are marked dirty |
| 1251 | * (if the page has buffers). |
| 1252 | * |
| 1253 | * When a buffer is marked dirty, its page is dirtied, but the page's other |
| 1254 | * buffers are not. |
| 1255 | * |
| 1256 | * Also. When blockdev buffers are explicitly read with bread(), they |
| 1257 | * individually become uptodate. But their backing page remains not |
| 1258 | * uptodate - even if all of its buffers are uptodate. A subsequent |
| 1259 | * block_read_full_page() against that page will discover all the uptodate |
| 1260 | * buffers, will set the page uptodate and will perform no I/O. |
| 1261 | */ |
| 1262 | |
| 1263 | /** |
| 1264 | * mark_buffer_dirty - mark a buffer_head as needing writeout |
Martin Waitz | 67be2dd | 2005-05-01 08:59:26 -0700 | [diff] [blame] | 1265 | * @bh: the buffer_head to mark dirty |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1266 | * |
| 1267 | * mark_buffer_dirty() will set the dirty bit against the buffer, then set its |
| 1268 | * backing page dirty, then tag the page as dirty in its address_space's radix |
| 1269 | * tree and then attach the address_space's inode to its superblock's dirty |
| 1270 | * inode list. |
| 1271 | * |
| 1272 | * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock, |
| 1273 | * mapping->tree_lock and the global inode_lock. |
| 1274 | */ |
| 1275 | void fastcall mark_buffer_dirty(struct buffer_head *bh) |
| 1276 | { |
| 1277 | if (!buffer_dirty(bh) && !test_set_buffer_dirty(bh)) |
| 1278 | __set_page_dirty_nobuffers(bh->b_page); |
| 1279 | } |
| 1280 | |
| 1281 | /* |
| 1282 | * Decrement a buffer_head's reference count. If all buffers against a page |
| 1283 | * have zero reference count, are clean and unlocked, and if the page is clean |
| 1284 | * and unlocked then try_to_free_buffers() may strip the buffers from the page |
| 1285 | * in preparation for freeing it (sometimes, rarely, buffers are removed from |
| 1286 | * a page but it ends up not being freed, and buffers may later be reattached). |
| 1287 | */ |
| 1288 | void __brelse(struct buffer_head * buf) |
| 1289 | { |
| 1290 | if (atomic_read(&buf->b_count)) { |
| 1291 | put_bh(buf); |
| 1292 | return; |
| 1293 | } |
| 1294 | printk(KERN_ERR "VFS: brelse: Trying to free free buffer\n"); |
| 1295 | WARN_ON(1); |
| 1296 | } |
| 1297 | |
| 1298 | /* |
| 1299 | * bforget() is like brelse(), except it discards any |
| 1300 | * potentially dirty data. |
| 1301 | */ |
| 1302 | void __bforget(struct buffer_head *bh) |
| 1303 | { |
| 1304 | clear_buffer_dirty(bh); |
| 1305 | if (!list_empty(&bh->b_assoc_buffers)) { |
| 1306 | struct address_space *buffer_mapping = bh->b_page->mapping; |
| 1307 | |
| 1308 | spin_lock(&buffer_mapping->private_lock); |
| 1309 | list_del_init(&bh->b_assoc_buffers); |
| 1310 | spin_unlock(&buffer_mapping->private_lock); |
| 1311 | } |
| 1312 | __brelse(bh); |
| 1313 | } |
| 1314 | |
| 1315 | static struct buffer_head *__bread_slow(struct buffer_head *bh) |
| 1316 | { |
| 1317 | lock_buffer(bh); |
| 1318 | if (buffer_uptodate(bh)) { |
| 1319 | unlock_buffer(bh); |
| 1320 | return bh; |
| 1321 | } else { |
| 1322 | get_bh(bh); |
| 1323 | bh->b_end_io = end_buffer_read_sync; |
| 1324 | submit_bh(READ, bh); |
| 1325 | wait_on_buffer(bh); |
| 1326 | if (buffer_uptodate(bh)) |
| 1327 | return bh; |
| 1328 | } |
| 1329 | brelse(bh); |
| 1330 | return NULL; |
| 1331 | } |
| 1332 | |
| 1333 | /* |
| 1334 | * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block(). |
| 1335 | * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their |
| 1336 | * refcount elevated by one when they're in an LRU. A buffer can only appear |
| 1337 | * once in a particular CPU's LRU. A single buffer can be present in multiple |
| 1338 | * CPU's LRUs at the same time. |
| 1339 | * |
| 1340 | * This is a transparent caching front-end to sb_bread(), sb_getblk() and |
| 1341 | * sb_find_get_block(). |
| 1342 | * |
| 1343 | * The LRUs themselves only need locking against invalidate_bh_lrus. We use |
| 1344 | * a local interrupt disable for that. |
| 1345 | */ |
| 1346 | |
| 1347 | #define BH_LRU_SIZE 8 |
| 1348 | |
| 1349 | struct bh_lru { |
| 1350 | struct buffer_head *bhs[BH_LRU_SIZE]; |
| 1351 | }; |
| 1352 | |
| 1353 | static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }}; |
| 1354 | |
| 1355 | #ifdef CONFIG_SMP |
| 1356 | #define bh_lru_lock() local_irq_disable() |
| 1357 | #define bh_lru_unlock() local_irq_enable() |
| 1358 | #else |
| 1359 | #define bh_lru_lock() preempt_disable() |
| 1360 | #define bh_lru_unlock() preempt_enable() |
| 1361 | #endif |
| 1362 | |
| 1363 | static inline void check_irqs_on(void) |
| 1364 | { |
| 1365 | #ifdef irqs_disabled |
| 1366 | BUG_ON(irqs_disabled()); |
| 1367 | #endif |
| 1368 | } |
| 1369 | |
| 1370 | /* |
| 1371 | * The LRU management algorithm is dopey-but-simple. Sorry. |
| 1372 | */ |
| 1373 | static void bh_lru_install(struct buffer_head *bh) |
| 1374 | { |
| 1375 | struct buffer_head *evictee = NULL; |
| 1376 | struct bh_lru *lru; |
| 1377 | |
| 1378 | check_irqs_on(); |
| 1379 | bh_lru_lock(); |
| 1380 | lru = &__get_cpu_var(bh_lrus); |
| 1381 | if (lru->bhs[0] != bh) { |
| 1382 | struct buffer_head *bhs[BH_LRU_SIZE]; |
| 1383 | int in; |
| 1384 | int out = 0; |
| 1385 | |
| 1386 | get_bh(bh); |
| 1387 | bhs[out++] = bh; |
| 1388 | for (in = 0; in < BH_LRU_SIZE; in++) { |
| 1389 | struct buffer_head *bh2 = lru->bhs[in]; |
| 1390 | |
| 1391 | if (bh2 == bh) { |
| 1392 | __brelse(bh2); |
| 1393 | } else { |
| 1394 | if (out >= BH_LRU_SIZE) { |
| 1395 | BUG_ON(evictee != NULL); |
| 1396 | evictee = bh2; |
| 1397 | } else { |
| 1398 | bhs[out++] = bh2; |
| 1399 | } |
| 1400 | } |
| 1401 | } |
| 1402 | while (out < BH_LRU_SIZE) |
| 1403 | bhs[out++] = NULL; |
| 1404 | memcpy(lru->bhs, bhs, sizeof(bhs)); |
| 1405 | } |
| 1406 | bh_lru_unlock(); |
| 1407 | |
| 1408 | if (evictee) |
| 1409 | __brelse(evictee); |
| 1410 | } |
| 1411 | |
| 1412 | /* |
| 1413 | * Look up the bh in this cpu's LRU. If it's there, move it to the head. |
| 1414 | */ |
| 1415 | static inline struct buffer_head * |
| 1416 | lookup_bh_lru(struct block_device *bdev, sector_t block, int size) |
| 1417 | { |
| 1418 | struct buffer_head *ret = NULL; |
| 1419 | struct bh_lru *lru; |
| 1420 | int i; |
| 1421 | |
| 1422 | check_irqs_on(); |
| 1423 | bh_lru_lock(); |
| 1424 | lru = &__get_cpu_var(bh_lrus); |
| 1425 | for (i = 0; i < BH_LRU_SIZE; i++) { |
| 1426 | struct buffer_head *bh = lru->bhs[i]; |
| 1427 | |
| 1428 | if (bh && bh->b_bdev == bdev && |
| 1429 | bh->b_blocknr == block && bh->b_size == size) { |
| 1430 | if (i) { |
| 1431 | while (i) { |
| 1432 | lru->bhs[i] = lru->bhs[i - 1]; |
| 1433 | i--; |
| 1434 | } |
| 1435 | lru->bhs[0] = bh; |
| 1436 | } |
| 1437 | get_bh(bh); |
| 1438 | ret = bh; |
| 1439 | break; |
| 1440 | } |
| 1441 | } |
| 1442 | bh_lru_unlock(); |
| 1443 | return ret; |
| 1444 | } |
| 1445 | |
| 1446 | /* |
| 1447 | * Perform a pagecache lookup for the matching buffer. If it's there, refresh |
| 1448 | * it in the LRU and mark it as accessed. If it is not present then return |
| 1449 | * NULL |
| 1450 | */ |
| 1451 | struct buffer_head * |
| 1452 | __find_get_block(struct block_device *bdev, sector_t block, int size) |
| 1453 | { |
| 1454 | struct buffer_head *bh = lookup_bh_lru(bdev, block, size); |
| 1455 | |
| 1456 | if (bh == NULL) { |
| 1457 | bh = __find_get_block_slow(bdev, block, size); |
| 1458 | if (bh) |
| 1459 | bh_lru_install(bh); |
| 1460 | } |
| 1461 | if (bh) |
| 1462 | touch_buffer(bh); |
| 1463 | return bh; |
| 1464 | } |
| 1465 | EXPORT_SYMBOL(__find_get_block); |
| 1466 | |
| 1467 | /* |
| 1468 | * __getblk will locate (and, if necessary, create) the buffer_head |
| 1469 | * which corresponds to the passed block_device, block and size. The |
| 1470 | * returned buffer has its reference count incremented. |
| 1471 | * |
| 1472 | * __getblk() cannot fail - it just keeps trying. If you pass it an |
| 1473 | * illegal block number, __getblk() will happily return a buffer_head |
| 1474 | * which represents the non-existent block. Very weird. |
| 1475 | * |
| 1476 | * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers() |
| 1477 | * attempt is failing. FIXME, perhaps? |
| 1478 | */ |
| 1479 | struct buffer_head * |
| 1480 | __getblk(struct block_device *bdev, sector_t block, int size) |
| 1481 | { |
| 1482 | struct buffer_head *bh = __find_get_block(bdev, block, size); |
| 1483 | |
| 1484 | might_sleep(); |
| 1485 | if (bh == NULL) |
| 1486 | bh = __getblk_slow(bdev, block, size); |
| 1487 | return bh; |
| 1488 | } |
| 1489 | EXPORT_SYMBOL(__getblk); |
| 1490 | |
| 1491 | /* |
| 1492 | * Do async read-ahead on a buffer.. |
| 1493 | */ |
| 1494 | void __breadahead(struct block_device *bdev, sector_t block, int size) |
| 1495 | { |
| 1496 | struct buffer_head *bh = __getblk(bdev, block, size); |
| 1497 | ll_rw_block(READA, 1, &bh); |
| 1498 | brelse(bh); |
| 1499 | } |
| 1500 | EXPORT_SYMBOL(__breadahead); |
| 1501 | |
| 1502 | /** |
| 1503 | * __bread() - reads a specified block and returns the bh |
Martin Waitz | 67be2dd | 2005-05-01 08:59:26 -0700 | [diff] [blame] | 1504 | * @bdev: the block_device to read from |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1505 | * @block: number of block |
| 1506 | * @size: size (in bytes) to read |
| 1507 | * |
| 1508 | * Reads a specified block, and returns buffer head that contains it. |
| 1509 | * It returns NULL if the block was unreadable. |
| 1510 | */ |
| 1511 | struct buffer_head * |
| 1512 | __bread(struct block_device *bdev, sector_t block, int size) |
| 1513 | { |
| 1514 | struct buffer_head *bh = __getblk(bdev, block, size); |
| 1515 | |
| 1516 | if (!buffer_uptodate(bh)) |
| 1517 | bh = __bread_slow(bh); |
| 1518 | return bh; |
| 1519 | } |
| 1520 | EXPORT_SYMBOL(__bread); |
| 1521 | |
| 1522 | /* |
| 1523 | * invalidate_bh_lrus() is called rarely - but not only at unmount. |
| 1524 | * This doesn't race because it runs in each cpu either in irq |
| 1525 | * or with preempt disabled. |
| 1526 | */ |
| 1527 | static void invalidate_bh_lru(void *arg) |
| 1528 | { |
| 1529 | struct bh_lru *b = &get_cpu_var(bh_lrus); |
| 1530 | int i; |
| 1531 | |
| 1532 | for (i = 0; i < BH_LRU_SIZE; i++) { |
| 1533 | brelse(b->bhs[i]); |
| 1534 | b->bhs[i] = NULL; |
| 1535 | } |
| 1536 | put_cpu_var(bh_lrus); |
| 1537 | } |
| 1538 | |
| 1539 | static void invalidate_bh_lrus(void) |
| 1540 | { |
| 1541 | on_each_cpu(invalidate_bh_lru, NULL, 1, 1); |
| 1542 | } |
| 1543 | |
| 1544 | void set_bh_page(struct buffer_head *bh, |
| 1545 | struct page *page, unsigned long offset) |
| 1546 | { |
| 1547 | bh->b_page = page; |
| 1548 | if (offset >= PAGE_SIZE) |
| 1549 | BUG(); |
| 1550 | if (PageHighMem(page)) |
| 1551 | /* |
| 1552 | * This catches illegal uses and preserves the offset: |
| 1553 | */ |
| 1554 | bh->b_data = (char *)(0 + offset); |
| 1555 | else |
| 1556 | bh->b_data = page_address(page) + offset; |
| 1557 | } |
| 1558 | EXPORT_SYMBOL(set_bh_page); |
| 1559 | |
| 1560 | /* |
| 1561 | * Called when truncating a buffer on a page completely. |
| 1562 | */ |
| 1563 | static inline void discard_buffer(struct buffer_head * bh) |
| 1564 | { |
| 1565 | lock_buffer(bh); |
| 1566 | clear_buffer_dirty(bh); |
| 1567 | bh->b_bdev = NULL; |
| 1568 | clear_buffer_mapped(bh); |
| 1569 | clear_buffer_req(bh); |
| 1570 | clear_buffer_new(bh); |
| 1571 | clear_buffer_delay(bh); |
| 1572 | unlock_buffer(bh); |
| 1573 | } |
| 1574 | |
| 1575 | /** |
| 1576 | * try_to_release_page() - release old fs-specific metadata on a page |
| 1577 | * |
| 1578 | * @page: the page which the kernel is trying to free |
| 1579 | * @gfp_mask: memory allocation flags (and I/O mode) |
| 1580 | * |
| 1581 | * The address_space is to try to release any data against the page |
| 1582 | * (presumably at page->private). If the release was successful, return `1'. |
| 1583 | * Otherwise return zero. |
| 1584 | * |
| 1585 | * The @gfp_mask argument specifies whether I/O may be performed to release |
| 1586 | * this page (__GFP_IO), and whether the call may block (__GFP_WAIT). |
| 1587 | * |
| 1588 | * NOTE: @gfp_mask may go away, and this function may become non-blocking. |
| 1589 | */ |
| 1590 | int try_to_release_page(struct page *page, int gfp_mask) |
| 1591 | { |
| 1592 | struct address_space * const mapping = page->mapping; |
| 1593 | |
| 1594 | BUG_ON(!PageLocked(page)); |
| 1595 | if (PageWriteback(page)) |
| 1596 | return 0; |
| 1597 | |
| 1598 | if (mapping && mapping->a_ops->releasepage) |
| 1599 | return mapping->a_ops->releasepage(page, gfp_mask); |
| 1600 | return try_to_free_buffers(page); |
| 1601 | } |
| 1602 | EXPORT_SYMBOL(try_to_release_page); |
| 1603 | |
| 1604 | /** |
| 1605 | * block_invalidatepage - invalidate part of all of a buffer-backed page |
| 1606 | * |
| 1607 | * @page: the page which is affected |
| 1608 | * @offset: the index of the truncation point |
| 1609 | * |
| 1610 | * block_invalidatepage() is called when all or part of the page has become |
| 1611 | * invalidatedby a truncate operation. |
| 1612 | * |
| 1613 | * block_invalidatepage() does not have to release all buffers, but it must |
| 1614 | * ensure that no dirty buffer is left outside @offset and that no I/O |
| 1615 | * is underway against any of the blocks which are outside the truncation |
| 1616 | * point. Because the caller is about to free (and possibly reuse) those |
| 1617 | * blocks on-disk. |
| 1618 | */ |
| 1619 | int block_invalidatepage(struct page *page, unsigned long offset) |
| 1620 | { |
| 1621 | struct buffer_head *head, *bh, *next; |
| 1622 | unsigned int curr_off = 0; |
| 1623 | int ret = 1; |
| 1624 | |
| 1625 | BUG_ON(!PageLocked(page)); |
| 1626 | if (!page_has_buffers(page)) |
| 1627 | goto out; |
| 1628 | |
| 1629 | head = page_buffers(page); |
| 1630 | bh = head; |
| 1631 | do { |
| 1632 | unsigned int next_off = curr_off + bh->b_size; |
| 1633 | next = bh->b_this_page; |
| 1634 | |
| 1635 | /* |
| 1636 | * is this block fully invalidated? |
| 1637 | */ |
| 1638 | if (offset <= curr_off) |
| 1639 | discard_buffer(bh); |
| 1640 | curr_off = next_off; |
| 1641 | bh = next; |
| 1642 | } while (bh != head); |
| 1643 | |
| 1644 | /* |
| 1645 | * We release buffers only if the entire page is being invalidated. |
| 1646 | * The get_block cached value has been unconditionally invalidated, |
| 1647 | * so real IO is not possible anymore. |
| 1648 | */ |
| 1649 | if (offset == 0) |
| 1650 | ret = try_to_release_page(page, 0); |
| 1651 | out: |
| 1652 | return ret; |
| 1653 | } |
| 1654 | EXPORT_SYMBOL(block_invalidatepage); |
| 1655 | |
| 1656 | /* |
| 1657 | * We attach and possibly dirty the buffers atomically wrt |
| 1658 | * __set_page_dirty_buffers() via private_lock. try_to_free_buffers |
| 1659 | * is already excluded via the page lock. |
| 1660 | */ |
| 1661 | void create_empty_buffers(struct page *page, |
| 1662 | unsigned long blocksize, unsigned long b_state) |
| 1663 | { |
| 1664 | struct buffer_head *bh, *head, *tail; |
| 1665 | |
| 1666 | head = alloc_page_buffers(page, blocksize, 1); |
| 1667 | bh = head; |
| 1668 | do { |
| 1669 | bh->b_state |= b_state; |
| 1670 | tail = bh; |
| 1671 | bh = bh->b_this_page; |
| 1672 | } while (bh); |
| 1673 | tail->b_this_page = head; |
| 1674 | |
| 1675 | spin_lock(&page->mapping->private_lock); |
| 1676 | if (PageUptodate(page) || PageDirty(page)) { |
| 1677 | bh = head; |
| 1678 | do { |
| 1679 | if (PageDirty(page)) |
| 1680 | set_buffer_dirty(bh); |
| 1681 | if (PageUptodate(page)) |
| 1682 | set_buffer_uptodate(bh); |
| 1683 | bh = bh->b_this_page; |
| 1684 | } while (bh != head); |
| 1685 | } |
| 1686 | attach_page_buffers(page, head); |
| 1687 | spin_unlock(&page->mapping->private_lock); |
| 1688 | } |
| 1689 | EXPORT_SYMBOL(create_empty_buffers); |
| 1690 | |
| 1691 | /* |
| 1692 | * We are taking a block for data and we don't want any output from any |
| 1693 | * buffer-cache aliases starting from return from that function and |
| 1694 | * until the moment when something will explicitly mark the buffer |
| 1695 | * dirty (hopefully that will not happen until we will free that block ;-) |
| 1696 | * We don't even need to mark it not-uptodate - nobody can expect |
| 1697 | * anything from a newly allocated buffer anyway. We used to used |
| 1698 | * unmap_buffer() for such invalidation, but that was wrong. We definitely |
| 1699 | * don't want to mark the alias unmapped, for example - it would confuse |
| 1700 | * anyone who might pick it with bread() afterwards... |
| 1701 | * |
| 1702 | * Also.. Note that bforget() doesn't lock the buffer. So there can |
| 1703 | * be writeout I/O going on against recently-freed buffers. We don't |
| 1704 | * wait on that I/O in bforget() - it's more efficient to wait on the I/O |
| 1705 | * only if we really need to. That happens here. |
| 1706 | */ |
| 1707 | void unmap_underlying_metadata(struct block_device *bdev, sector_t block) |
| 1708 | { |
| 1709 | struct buffer_head *old_bh; |
| 1710 | |
| 1711 | might_sleep(); |
| 1712 | |
| 1713 | old_bh = __find_get_block_slow(bdev, block, 0); |
| 1714 | if (old_bh) { |
| 1715 | clear_buffer_dirty(old_bh); |
| 1716 | wait_on_buffer(old_bh); |
| 1717 | clear_buffer_req(old_bh); |
| 1718 | __brelse(old_bh); |
| 1719 | } |
| 1720 | } |
| 1721 | EXPORT_SYMBOL(unmap_underlying_metadata); |
| 1722 | |
| 1723 | /* |
| 1724 | * NOTE! All mapped/uptodate combinations are valid: |
| 1725 | * |
| 1726 | * Mapped Uptodate Meaning |
| 1727 | * |
| 1728 | * No No "unknown" - must do get_block() |
| 1729 | * No Yes "hole" - zero-filled |
| 1730 | * Yes No "allocated" - allocated on disk, not read in |
| 1731 | * Yes Yes "valid" - allocated and up-to-date in memory. |
| 1732 | * |
| 1733 | * "Dirty" is valid only with the last case (mapped+uptodate). |
| 1734 | */ |
| 1735 | |
| 1736 | /* |
| 1737 | * While block_write_full_page is writing back the dirty buffers under |
| 1738 | * the page lock, whoever dirtied the buffers may decide to clean them |
| 1739 | * again at any time. We handle that by only looking at the buffer |
| 1740 | * state inside lock_buffer(). |
| 1741 | * |
| 1742 | * If block_write_full_page() is called for regular writeback |
| 1743 | * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a |
| 1744 | * locked buffer. This only can happen if someone has written the buffer |
| 1745 | * directly, with submit_bh(). At the address_space level PageWriteback |
| 1746 | * prevents this contention from occurring. |
| 1747 | */ |
| 1748 | static int __block_write_full_page(struct inode *inode, struct page *page, |
| 1749 | get_block_t *get_block, struct writeback_control *wbc) |
| 1750 | { |
| 1751 | int err; |
| 1752 | sector_t block; |
| 1753 | sector_t last_block; |
Andrew Morton | f0fbd5f | 2005-05-05 16:15:48 -0700 | [diff] [blame] | 1754 | struct buffer_head *bh, *head; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1755 | int nr_underway = 0; |
| 1756 | |
| 1757 | BUG_ON(!PageLocked(page)); |
| 1758 | |
| 1759 | last_block = (i_size_read(inode) - 1) >> inode->i_blkbits; |
| 1760 | |
| 1761 | if (!page_has_buffers(page)) { |
| 1762 | create_empty_buffers(page, 1 << inode->i_blkbits, |
| 1763 | (1 << BH_Dirty)|(1 << BH_Uptodate)); |
| 1764 | } |
| 1765 | |
| 1766 | /* |
| 1767 | * Be very careful. We have no exclusion from __set_page_dirty_buffers |
| 1768 | * here, and the (potentially unmapped) buffers may become dirty at |
| 1769 | * any time. If a buffer becomes dirty here after we've inspected it |
| 1770 | * then we just miss that fact, and the page stays dirty. |
| 1771 | * |
| 1772 | * Buffers outside i_size may be dirtied by __set_page_dirty_buffers; |
| 1773 | * handle that here by just cleaning them. |
| 1774 | */ |
| 1775 | |
| 1776 | block = page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits); |
| 1777 | head = page_buffers(page); |
| 1778 | bh = head; |
| 1779 | |
| 1780 | /* |
| 1781 | * Get all the dirty buffers mapped to disk addresses and |
| 1782 | * handle any aliases from the underlying blockdev's mapping. |
| 1783 | */ |
| 1784 | do { |
| 1785 | if (block > last_block) { |
| 1786 | /* |
| 1787 | * mapped buffers outside i_size will occur, because |
| 1788 | * this page can be outside i_size when there is a |
| 1789 | * truncate in progress. |
| 1790 | */ |
| 1791 | /* |
| 1792 | * The buffer was zeroed by block_write_full_page() |
| 1793 | */ |
| 1794 | clear_buffer_dirty(bh); |
| 1795 | set_buffer_uptodate(bh); |
| 1796 | } else if (!buffer_mapped(bh) && buffer_dirty(bh)) { |
| 1797 | err = get_block(inode, block, bh, 1); |
| 1798 | if (err) |
| 1799 | goto recover; |
| 1800 | if (buffer_new(bh)) { |
| 1801 | /* blockdev mappings never come here */ |
| 1802 | clear_buffer_new(bh); |
| 1803 | unmap_underlying_metadata(bh->b_bdev, |
| 1804 | bh->b_blocknr); |
| 1805 | } |
| 1806 | } |
| 1807 | bh = bh->b_this_page; |
| 1808 | block++; |
| 1809 | } while (bh != head); |
| 1810 | |
| 1811 | do { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1812 | if (!buffer_mapped(bh)) |
| 1813 | continue; |
| 1814 | /* |
| 1815 | * If it's a fully non-blocking write attempt and we cannot |
| 1816 | * lock the buffer then redirty the page. Note that this can |
| 1817 | * potentially cause a busy-wait loop from pdflush and kswapd |
| 1818 | * activity, but those code paths have their own higher-level |
| 1819 | * throttling. |
| 1820 | */ |
| 1821 | if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) { |
| 1822 | lock_buffer(bh); |
| 1823 | } else if (test_set_buffer_locked(bh)) { |
| 1824 | redirty_page_for_writepage(wbc, page); |
| 1825 | continue; |
| 1826 | } |
| 1827 | if (test_clear_buffer_dirty(bh)) { |
| 1828 | mark_buffer_async_write(bh); |
| 1829 | } else { |
| 1830 | unlock_buffer(bh); |
| 1831 | } |
| 1832 | } while ((bh = bh->b_this_page) != head); |
| 1833 | |
| 1834 | /* |
| 1835 | * The page and its buffers are protected by PageWriteback(), so we can |
| 1836 | * drop the bh refcounts early. |
| 1837 | */ |
| 1838 | BUG_ON(PageWriteback(page)); |
| 1839 | set_page_writeback(page); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1840 | |
| 1841 | do { |
| 1842 | struct buffer_head *next = bh->b_this_page; |
| 1843 | if (buffer_async_write(bh)) { |
| 1844 | submit_bh(WRITE, bh); |
| 1845 | nr_underway++; |
| 1846 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1847 | bh = next; |
| 1848 | } while (bh != head); |
Andrew Morton | 05937ba | 2005-05-05 16:15:47 -0700 | [diff] [blame] | 1849 | unlock_page(page); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1850 | |
| 1851 | err = 0; |
| 1852 | done: |
| 1853 | if (nr_underway == 0) { |
| 1854 | /* |
| 1855 | * The page was marked dirty, but the buffers were |
| 1856 | * clean. Someone wrote them back by hand with |
| 1857 | * ll_rw_block/submit_bh. A rare case. |
| 1858 | */ |
| 1859 | int uptodate = 1; |
| 1860 | do { |
| 1861 | if (!buffer_uptodate(bh)) { |
| 1862 | uptodate = 0; |
| 1863 | break; |
| 1864 | } |
| 1865 | bh = bh->b_this_page; |
| 1866 | } while (bh != head); |
| 1867 | if (uptodate) |
| 1868 | SetPageUptodate(page); |
| 1869 | end_page_writeback(page); |
| 1870 | /* |
| 1871 | * The page and buffer_heads can be released at any time from |
| 1872 | * here on. |
| 1873 | */ |
| 1874 | wbc->pages_skipped++; /* We didn't write this page */ |
| 1875 | } |
| 1876 | return err; |
| 1877 | |
| 1878 | recover: |
| 1879 | /* |
| 1880 | * ENOSPC, or some other error. We may already have added some |
| 1881 | * blocks to the file, so we need to write these out to avoid |
| 1882 | * exposing stale data. |
| 1883 | * The page is currently locked and not marked for writeback |
| 1884 | */ |
| 1885 | bh = head; |
| 1886 | /* Recovery: lock and submit the mapped buffers */ |
| 1887 | do { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1888 | if (buffer_mapped(bh) && buffer_dirty(bh)) { |
| 1889 | lock_buffer(bh); |
| 1890 | mark_buffer_async_write(bh); |
| 1891 | } else { |
| 1892 | /* |
| 1893 | * The buffer may have been set dirty during |
| 1894 | * attachment to a dirty page. |
| 1895 | */ |
| 1896 | clear_buffer_dirty(bh); |
| 1897 | } |
| 1898 | } while ((bh = bh->b_this_page) != head); |
| 1899 | SetPageError(page); |
| 1900 | BUG_ON(PageWriteback(page)); |
| 1901 | set_page_writeback(page); |
| 1902 | unlock_page(page); |
| 1903 | do { |
| 1904 | struct buffer_head *next = bh->b_this_page; |
| 1905 | if (buffer_async_write(bh)) { |
| 1906 | clear_buffer_dirty(bh); |
| 1907 | submit_bh(WRITE, bh); |
| 1908 | nr_underway++; |
| 1909 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1910 | bh = next; |
| 1911 | } while (bh != head); |
| 1912 | goto done; |
| 1913 | } |
| 1914 | |
| 1915 | static int __block_prepare_write(struct inode *inode, struct page *page, |
| 1916 | unsigned from, unsigned to, get_block_t *get_block) |
| 1917 | { |
| 1918 | unsigned block_start, block_end; |
| 1919 | sector_t block; |
| 1920 | int err = 0; |
| 1921 | unsigned blocksize, bbits; |
| 1922 | struct buffer_head *bh, *head, *wait[2], **wait_bh=wait; |
| 1923 | |
| 1924 | BUG_ON(!PageLocked(page)); |
| 1925 | BUG_ON(from > PAGE_CACHE_SIZE); |
| 1926 | BUG_ON(to > PAGE_CACHE_SIZE); |
| 1927 | BUG_ON(from > to); |
| 1928 | |
| 1929 | blocksize = 1 << inode->i_blkbits; |
| 1930 | if (!page_has_buffers(page)) |
| 1931 | create_empty_buffers(page, blocksize, 0); |
| 1932 | head = page_buffers(page); |
| 1933 | |
| 1934 | bbits = inode->i_blkbits; |
| 1935 | block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits); |
| 1936 | |
| 1937 | for(bh = head, block_start = 0; bh != head || !block_start; |
| 1938 | block++, block_start=block_end, bh = bh->b_this_page) { |
| 1939 | block_end = block_start + blocksize; |
| 1940 | if (block_end <= from || block_start >= to) { |
| 1941 | if (PageUptodate(page)) { |
| 1942 | if (!buffer_uptodate(bh)) |
| 1943 | set_buffer_uptodate(bh); |
| 1944 | } |
| 1945 | continue; |
| 1946 | } |
| 1947 | if (buffer_new(bh)) |
| 1948 | clear_buffer_new(bh); |
| 1949 | if (!buffer_mapped(bh)) { |
| 1950 | err = get_block(inode, block, bh, 1); |
| 1951 | if (err) |
Nick Piggin | f3ddbdc | 2005-05-05 16:15:45 -0700 | [diff] [blame] | 1952 | break; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1953 | if (buffer_new(bh)) { |
| 1954 | clear_buffer_new(bh); |
| 1955 | unmap_underlying_metadata(bh->b_bdev, |
| 1956 | bh->b_blocknr); |
| 1957 | if (PageUptodate(page)) { |
| 1958 | set_buffer_uptodate(bh); |
| 1959 | continue; |
| 1960 | } |
| 1961 | if (block_end > to || block_start < from) { |
| 1962 | void *kaddr; |
| 1963 | |
| 1964 | kaddr = kmap_atomic(page, KM_USER0); |
| 1965 | if (block_end > to) |
| 1966 | memset(kaddr+to, 0, |
| 1967 | block_end-to); |
| 1968 | if (block_start < from) |
| 1969 | memset(kaddr+block_start, |
| 1970 | 0, from-block_start); |
| 1971 | flush_dcache_page(page); |
| 1972 | kunmap_atomic(kaddr, KM_USER0); |
| 1973 | } |
| 1974 | continue; |
| 1975 | } |
| 1976 | } |
| 1977 | if (PageUptodate(page)) { |
| 1978 | if (!buffer_uptodate(bh)) |
| 1979 | set_buffer_uptodate(bh); |
| 1980 | continue; |
| 1981 | } |
| 1982 | if (!buffer_uptodate(bh) && !buffer_delay(bh) && |
| 1983 | (block_start < from || block_end > to)) { |
| 1984 | ll_rw_block(READ, 1, &bh); |
| 1985 | *wait_bh++=bh; |
| 1986 | } |
| 1987 | } |
| 1988 | /* |
| 1989 | * If we issued read requests - let them complete. |
| 1990 | */ |
| 1991 | while(wait_bh > wait) { |
| 1992 | wait_on_buffer(*--wait_bh); |
| 1993 | if (!buffer_uptodate(*wait_bh)) |
Nick Piggin | f3ddbdc | 2005-05-05 16:15:45 -0700 | [diff] [blame] | 1994 | err = -EIO; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1995 | } |
Nick Piggin | f3ddbdc | 2005-05-05 16:15:45 -0700 | [diff] [blame] | 1996 | if (!err) |
| 1997 | return err; |
| 1998 | |
| 1999 | /* Error case: */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2000 | /* |
| 2001 | * Zero out any newly allocated blocks to avoid exposing stale |
| 2002 | * data. If BH_New is set, we know that the block was newly |
| 2003 | * allocated in the above loop. |
| 2004 | */ |
| 2005 | bh = head; |
| 2006 | block_start = 0; |
| 2007 | do { |
| 2008 | block_end = block_start+blocksize; |
| 2009 | if (block_end <= from) |
| 2010 | goto next_bh; |
| 2011 | if (block_start >= to) |
| 2012 | break; |
| 2013 | if (buffer_new(bh)) { |
| 2014 | void *kaddr; |
| 2015 | |
| 2016 | clear_buffer_new(bh); |
| 2017 | kaddr = kmap_atomic(page, KM_USER0); |
| 2018 | memset(kaddr+block_start, 0, bh->b_size); |
| 2019 | kunmap_atomic(kaddr, KM_USER0); |
| 2020 | set_buffer_uptodate(bh); |
| 2021 | mark_buffer_dirty(bh); |
| 2022 | } |
| 2023 | next_bh: |
| 2024 | block_start = block_end; |
| 2025 | bh = bh->b_this_page; |
| 2026 | } while (bh != head); |
| 2027 | return err; |
| 2028 | } |
| 2029 | |
| 2030 | static int __block_commit_write(struct inode *inode, struct page *page, |
| 2031 | unsigned from, unsigned to) |
| 2032 | { |
| 2033 | unsigned block_start, block_end; |
| 2034 | int partial = 0; |
| 2035 | unsigned blocksize; |
| 2036 | struct buffer_head *bh, *head; |
| 2037 | |
| 2038 | blocksize = 1 << inode->i_blkbits; |
| 2039 | |
| 2040 | for(bh = head = page_buffers(page), block_start = 0; |
| 2041 | bh != head || !block_start; |
| 2042 | block_start=block_end, bh = bh->b_this_page) { |
| 2043 | block_end = block_start + blocksize; |
| 2044 | if (block_end <= from || block_start >= to) { |
| 2045 | if (!buffer_uptodate(bh)) |
| 2046 | partial = 1; |
| 2047 | } else { |
| 2048 | set_buffer_uptodate(bh); |
| 2049 | mark_buffer_dirty(bh); |
| 2050 | } |
| 2051 | } |
| 2052 | |
| 2053 | /* |
| 2054 | * If this is a partial write which happened to make all buffers |
| 2055 | * uptodate then we can optimize away a bogus readpage() for |
| 2056 | * the next read(). Here we 'discover' whether the page went |
| 2057 | * uptodate as a result of this (potentially partial) write. |
| 2058 | */ |
| 2059 | if (!partial) |
| 2060 | SetPageUptodate(page); |
| 2061 | return 0; |
| 2062 | } |
| 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 | |
Matt Mackall | cd7619d | 2005-05-01 08:59:01 -0700 | [diff] [blame] | 2080 | BUG_ON(!PageLocked(page)); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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)) { |
Andrew Morton | c64610b | 2005-05-16 21:53:49 -0700 | [diff] [blame] | 2097 | int err = 0; |
| 2098 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2099 | fully_mapped = 0; |
| 2100 | if (iblock < lblock) { |
Andrew Morton | c64610b | 2005-05-16 21:53:49 -0700 | [diff] [blame] | 2101 | err = get_block(inode, iblock, bh, 0); |
| 2102 | if (err) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2103 | SetPageError(page); |
| 2104 | } |
| 2105 | if (!buffer_mapped(bh)) { |
| 2106 | void *kaddr = kmap_atomic(page, KM_USER0); |
| 2107 | memset(kaddr + i * blocksize, 0, blocksize); |
| 2108 | flush_dcache_page(page); |
| 2109 | kunmap_atomic(kaddr, KM_USER0); |
Andrew Morton | c64610b | 2005-05-16 21:53:49 -0700 | [diff] [blame] | 2110 | if (!err) |
| 2111 | set_buffer_uptodate(bh); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2112 | continue; |
| 2113 | } |
| 2114 | /* |
| 2115 | * get_block() might have updated the buffer |
| 2116 | * synchronously |
| 2117 | */ |
| 2118 | if (buffer_uptodate(bh)) |
| 2119 | continue; |
| 2120 | } |
| 2121 | arr[nr++] = bh; |
| 2122 | } while (i++, iblock++, (bh = bh->b_this_page) != head); |
| 2123 | |
| 2124 | if (fully_mapped) |
| 2125 | SetPageMappedToDisk(page); |
| 2126 | |
| 2127 | if (!nr) { |
| 2128 | /* |
| 2129 | * All buffers are uptodate - we can set the page uptodate |
| 2130 | * as well. But not if get_block() returned an error. |
| 2131 | */ |
| 2132 | if (!PageError(page)) |
| 2133 | SetPageUptodate(page); |
| 2134 | unlock_page(page); |
| 2135 | return 0; |
| 2136 | } |
| 2137 | |
| 2138 | /* Stage two: lock the buffers */ |
| 2139 | for (i = 0; i < nr; i++) { |
| 2140 | bh = arr[i]; |
| 2141 | lock_buffer(bh); |
| 2142 | mark_buffer_async_read(bh); |
| 2143 | } |
| 2144 | |
| 2145 | /* |
| 2146 | * Stage 3: start the IO. Check for uptodateness |
| 2147 | * inside the buffer lock in case another process reading |
| 2148 | * the underlying blockdev brought it uptodate (the sct fix). |
| 2149 | */ |
| 2150 | for (i = 0; i < nr; i++) { |
| 2151 | bh = arr[i]; |
| 2152 | if (buffer_uptodate(bh)) |
| 2153 | end_buffer_async_read(bh, 1); |
| 2154 | else |
| 2155 | submit_bh(READ, bh); |
| 2156 | } |
| 2157 | return 0; |
| 2158 | } |
| 2159 | |
| 2160 | /* utility function for filesystems that need to do work on expanding |
| 2161 | * truncates. Uses prepare/commit_write to allow the filesystem to |
| 2162 | * deal with the hole. |
| 2163 | */ |
| 2164 | int generic_cont_expand(struct inode *inode, loff_t size) |
| 2165 | { |
| 2166 | struct address_space *mapping = inode->i_mapping; |
| 2167 | struct page *page; |
| 2168 | unsigned long index, offset, 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 | offset = (size & (PAGE_CACHE_SIZE-1)); /* Within page */ |
| 2181 | |
| 2182 | /* ugh. in prepare/commit_write, if from==to==start of block, we |
| 2183 | ** skip the prepare. make sure we never send an offset for the start |
| 2184 | ** of a block |
| 2185 | */ |
| 2186 | if ((offset & (inode->i_sb->s_blocksize - 1)) == 0) { |
| 2187 | offset++; |
| 2188 | } |
| 2189 | index = size >> PAGE_CACHE_SHIFT; |
| 2190 | err = -ENOMEM; |
| 2191 | page = grab_cache_page(mapping, index); |
| 2192 | if (!page) |
| 2193 | goto out; |
| 2194 | err = mapping->a_ops->prepare_write(NULL, page, offset, offset); |
| 2195 | if (!err) { |
| 2196 | err = mapping->a_ops->commit_write(NULL, page, offset, offset); |
| 2197 | } |
| 2198 | unlock_page(page); |
| 2199 | page_cache_release(page); |
| 2200 | if (err > 0) |
| 2201 | err = 0; |
| 2202 | out: |
| 2203 | return err; |
| 2204 | } |
| 2205 | |
| 2206 | /* |
| 2207 | * For moronic filesystems that do not allow holes in file. |
| 2208 | * We may have to extend the file. |
| 2209 | */ |
| 2210 | |
| 2211 | int cont_prepare_write(struct page *page, unsigned offset, |
| 2212 | unsigned to, get_block_t *get_block, loff_t *bytes) |
| 2213 | { |
| 2214 | struct address_space *mapping = page->mapping; |
| 2215 | struct inode *inode = mapping->host; |
| 2216 | struct page *new_page; |
| 2217 | pgoff_t pgpos; |
| 2218 | long status; |
| 2219 | unsigned zerofrom; |
| 2220 | unsigned blocksize = 1 << inode->i_blkbits; |
| 2221 | void *kaddr; |
| 2222 | |
| 2223 | while(page->index > (pgpos = *bytes>>PAGE_CACHE_SHIFT)) { |
| 2224 | status = -ENOMEM; |
| 2225 | new_page = grab_cache_page(mapping, pgpos); |
| 2226 | if (!new_page) |
| 2227 | goto out; |
| 2228 | /* we might sleep */ |
| 2229 | if (*bytes>>PAGE_CACHE_SHIFT != pgpos) { |
| 2230 | unlock_page(new_page); |
| 2231 | page_cache_release(new_page); |
| 2232 | continue; |
| 2233 | } |
| 2234 | zerofrom = *bytes & ~PAGE_CACHE_MASK; |
| 2235 | if (zerofrom & (blocksize-1)) { |
| 2236 | *bytes |= (blocksize-1); |
| 2237 | (*bytes)++; |
| 2238 | } |
| 2239 | status = __block_prepare_write(inode, new_page, zerofrom, |
| 2240 | PAGE_CACHE_SIZE, get_block); |
| 2241 | if (status) |
| 2242 | goto out_unmap; |
| 2243 | kaddr = kmap_atomic(new_page, KM_USER0); |
| 2244 | memset(kaddr+zerofrom, 0, PAGE_CACHE_SIZE-zerofrom); |
| 2245 | flush_dcache_page(new_page); |
| 2246 | kunmap_atomic(kaddr, KM_USER0); |
| 2247 | generic_commit_write(NULL, new_page, zerofrom, PAGE_CACHE_SIZE); |
| 2248 | unlock_page(new_page); |
| 2249 | page_cache_release(new_page); |
| 2250 | } |
| 2251 | |
| 2252 | if (page->index < pgpos) { |
| 2253 | /* completely inside the area */ |
| 2254 | zerofrom = offset; |
| 2255 | } else { |
| 2256 | /* page covers the boundary, find the boundary offset */ |
| 2257 | zerofrom = *bytes & ~PAGE_CACHE_MASK; |
| 2258 | |
| 2259 | /* if we will expand the thing last block will be filled */ |
| 2260 | if (to > zerofrom && (zerofrom & (blocksize-1))) { |
| 2261 | *bytes |= (blocksize-1); |
| 2262 | (*bytes)++; |
| 2263 | } |
| 2264 | |
| 2265 | /* starting below the boundary? Nothing to zero out */ |
| 2266 | if (offset <= zerofrom) |
| 2267 | zerofrom = offset; |
| 2268 | } |
| 2269 | status = __block_prepare_write(inode, page, zerofrom, to, get_block); |
| 2270 | if (status) |
| 2271 | goto out1; |
| 2272 | if (zerofrom < offset) { |
| 2273 | kaddr = kmap_atomic(page, KM_USER0); |
| 2274 | memset(kaddr+zerofrom, 0, offset-zerofrom); |
| 2275 | flush_dcache_page(page); |
| 2276 | kunmap_atomic(kaddr, KM_USER0); |
| 2277 | __block_commit_write(inode, page, zerofrom, offset); |
| 2278 | } |
| 2279 | return 0; |
| 2280 | out1: |
| 2281 | ClearPageUptodate(page); |
| 2282 | return status; |
| 2283 | |
| 2284 | out_unmap: |
| 2285 | ClearPageUptodate(new_page); |
| 2286 | unlock_page(new_page); |
| 2287 | page_cache_release(new_page); |
| 2288 | out: |
| 2289 | return status; |
| 2290 | } |
| 2291 | |
| 2292 | int block_prepare_write(struct page *page, unsigned from, unsigned to, |
| 2293 | get_block_t *get_block) |
| 2294 | { |
| 2295 | struct inode *inode = page->mapping->host; |
| 2296 | int err = __block_prepare_write(inode, page, from, to, get_block); |
| 2297 | if (err) |
| 2298 | ClearPageUptodate(page); |
| 2299 | return err; |
| 2300 | } |
| 2301 | |
| 2302 | int block_commit_write(struct page *page, unsigned from, unsigned to) |
| 2303 | { |
| 2304 | struct inode *inode = page->mapping->host; |
| 2305 | __block_commit_write(inode,page,from,to); |
| 2306 | return 0; |
| 2307 | } |
| 2308 | |
| 2309 | int generic_commit_write(struct file *file, struct page *page, |
| 2310 | unsigned from, unsigned to) |
| 2311 | { |
| 2312 | struct inode *inode = page->mapping->host; |
| 2313 | loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to; |
| 2314 | __block_commit_write(inode,page,from,to); |
| 2315 | /* |
| 2316 | * No need to use i_size_read() here, the i_size |
| 2317 | * cannot change under us because we hold i_sem. |
| 2318 | */ |
| 2319 | if (pos > inode->i_size) { |
| 2320 | i_size_write(inode, pos); |
| 2321 | mark_inode_dirty(inode); |
| 2322 | } |
| 2323 | return 0; |
| 2324 | } |
| 2325 | |
| 2326 | |
| 2327 | /* |
| 2328 | * nobh_prepare_write()'s prereads are special: the buffer_heads are freed |
| 2329 | * immediately, while under the page lock. So it needs a special end_io |
| 2330 | * handler which does not touch the bh after unlocking it. |
| 2331 | * |
| 2332 | * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but |
| 2333 | * a race there is benign: unlock_buffer() only use the bh's address for |
| 2334 | * hashing after unlocking the buffer, so it doesn't actually touch the bh |
| 2335 | * itself. |
| 2336 | */ |
| 2337 | static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate) |
| 2338 | { |
| 2339 | if (uptodate) { |
| 2340 | set_buffer_uptodate(bh); |
| 2341 | } else { |
| 2342 | /* This happens, due to failed READA attempts. */ |
| 2343 | clear_buffer_uptodate(bh); |
| 2344 | } |
| 2345 | unlock_buffer(bh); |
| 2346 | } |
| 2347 | |
| 2348 | /* |
| 2349 | * On entry, the page is fully not uptodate. |
| 2350 | * On exit the page is fully uptodate in the areas outside (from,to) |
| 2351 | */ |
| 2352 | int nobh_prepare_write(struct page *page, unsigned from, unsigned to, |
| 2353 | get_block_t *get_block) |
| 2354 | { |
| 2355 | struct inode *inode = page->mapping->host; |
| 2356 | const unsigned blkbits = inode->i_blkbits; |
| 2357 | const unsigned blocksize = 1 << blkbits; |
| 2358 | struct buffer_head map_bh; |
| 2359 | struct buffer_head *read_bh[MAX_BUF_PER_PAGE]; |
| 2360 | unsigned block_in_page; |
| 2361 | unsigned block_start; |
| 2362 | sector_t block_in_file; |
| 2363 | char *kaddr; |
| 2364 | int nr_reads = 0; |
| 2365 | int i; |
| 2366 | int ret = 0; |
| 2367 | int is_mapped_to_disk = 1; |
| 2368 | int dirtied_it = 0; |
| 2369 | |
| 2370 | if (PageMappedToDisk(page)) |
| 2371 | return 0; |
| 2372 | |
| 2373 | block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits); |
| 2374 | map_bh.b_page = page; |
| 2375 | |
| 2376 | /* |
| 2377 | * We loop across all blocks in the page, whether or not they are |
| 2378 | * part of the affected region. This is so we can discover if the |
| 2379 | * page is fully mapped-to-disk. |
| 2380 | */ |
| 2381 | for (block_start = 0, block_in_page = 0; |
| 2382 | block_start < PAGE_CACHE_SIZE; |
| 2383 | block_in_page++, block_start += blocksize) { |
| 2384 | unsigned block_end = block_start + blocksize; |
| 2385 | int create; |
| 2386 | |
| 2387 | map_bh.b_state = 0; |
| 2388 | create = 1; |
| 2389 | if (block_start >= to) |
| 2390 | create = 0; |
| 2391 | ret = get_block(inode, block_in_file + block_in_page, |
| 2392 | &map_bh, create); |
| 2393 | if (ret) |
| 2394 | goto failed; |
| 2395 | if (!buffer_mapped(&map_bh)) |
| 2396 | is_mapped_to_disk = 0; |
| 2397 | if (buffer_new(&map_bh)) |
| 2398 | unmap_underlying_metadata(map_bh.b_bdev, |
| 2399 | map_bh.b_blocknr); |
| 2400 | if (PageUptodate(page)) |
| 2401 | continue; |
| 2402 | if (buffer_new(&map_bh) || !buffer_mapped(&map_bh)) { |
| 2403 | kaddr = kmap_atomic(page, KM_USER0); |
| 2404 | if (block_start < from) { |
| 2405 | memset(kaddr+block_start, 0, from-block_start); |
| 2406 | dirtied_it = 1; |
| 2407 | } |
| 2408 | if (block_end > to) { |
| 2409 | memset(kaddr + to, 0, block_end - to); |
| 2410 | dirtied_it = 1; |
| 2411 | } |
| 2412 | flush_dcache_page(page); |
| 2413 | kunmap_atomic(kaddr, KM_USER0); |
| 2414 | continue; |
| 2415 | } |
| 2416 | if (buffer_uptodate(&map_bh)) |
| 2417 | continue; /* reiserfs does this */ |
| 2418 | if (block_start < from || block_end > to) { |
| 2419 | struct buffer_head *bh = alloc_buffer_head(GFP_NOFS); |
| 2420 | |
| 2421 | if (!bh) { |
| 2422 | ret = -ENOMEM; |
| 2423 | goto failed; |
| 2424 | } |
| 2425 | bh->b_state = map_bh.b_state; |
| 2426 | atomic_set(&bh->b_count, 0); |
| 2427 | bh->b_this_page = NULL; |
| 2428 | bh->b_page = page; |
| 2429 | bh->b_blocknr = map_bh.b_blocknr; |
| 2430 | bh->b_size = blocksize; |
| 2431 | bh->b_data = (char *)(long)block_start; |
| 2432 | bh->b_bdev = map_bh.b_bdev; |
| 2433 | bh->b_private = NULL; |
| 2434 | read_bh[nr_reads++] = bh; |
| 2435 | } |
| 2436 | } |
| 2437 | |
| 2438 | if (nr_reads) { |
| 2439 | struct buffer_head *bh; |
| 2440 | |
| 2441 | /* |
| 2442 | * The page is locked, so these buffers are protected from |
| 2443 | * any VM or truncate activity. Hence we don't need to care |
| 2444 | * for the buffer_head refcounts. |
| 2445 | */ |
| 2446 | for (i = 0; i < nr_reads; i++) { |
| 2447 | bh = read_bh[i]; |
| 2448 | lock_buffer(bh); |
| 2449 | bh->b_end_io = end_buffer_read_nobh; |
| 2450 | submit_bh(READ, bh); |
| 2451 | } |
| 2452 | for (i = 0; i < nr_reads; i++) { |
| 2453 | bh = read_bh[i]; |
| 2454 | wait_on_buffer(bh); |
| 2455 | if (!buffer_uptodate(bh)) |
| 2456 | ret = -EIO; |
| 2457 | free_buffer_head(bh); |
| 2458 | read_bh[i] = NULL; |
| 2459 | } |
| 2460 | if (ret) |
| 2461 | goto failed; |
| 2462 | } |
| 2463 | |
| 2464 | if (is_mapped_to_disk) |
| 2465 | SetPageMappedToDisk(page); |
| 2466 | SetPageUptodate(page); |
| 2467 | |
| 2468 | /* |
| 2469 | * Setting the page dirty here isn't necessary for the prepare_write |
| 2470 | * function - commit_write will do that. But if/when this function is |
| 2471 | * used within the pagefault handler to ensure that all mmapped pages |
| 2472 | * have backing space in the filesystem, we will need to dirty the page |
| 2473 | * if its contents were altered. |
| 2474 | */ |
| 2475 | if (dirtied_it) |
| 2476 | set_page_dirty(page); |
| 2477 | |
| 2478 | return 0; |
| 2479 | |
| 2480 | failed: |
| 2481 | for (i = 0; i < nr_reads; i++) { |
| 2482 | if (read_bh[i]) |
| 2483 | free_buffer_head(read_bh[i]); |
| 2484 | } |
| 2485 | |
| 2486 | /* |
| 2487 | * Error recovery is pretty slack. Clear the page and mark it dirty |
| 2488 | * so we'll later zero out any blocks which _were_ allocated. |
| 2489 | */ |
| 2490 | kaddr = kmap_atomic(page, KM_USER0); |
| 2491 | memset(kaddr, 0, PAGE_CACHE_SIZE); |
| 2492 | kunmap_atomic(kaddr, KM_USER0); |
| 2493 | SetPageUptodate(page); |
| 2494 | set_page_dirty(page); |
| 2495 | return ret; |
| 2496 | } |
| 2497 | EXPORT_SYMBOL(nobh_prepare_write); |
| 2498 | |
| 2499 | int nobh_commit_write(struct file *file, struct page *page, |
| 2500 | unsigned from, unsigned to) |
| 2501 | { |
| 2502 | struct inode *inode = page->mapping->host; |
| 2503 | loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to; |
| 2504 | |
| 2505 | set_page_dirty(page); |
| 2506 | if (pos > inode->i_size) { |
| 2507 | i_size_write(inode, pos); |
| 2508 | mark_inode_dirty(inode); |
| 2509 | } |
| 2510 | return 0; |
| 2511 | } |
| 2512 | EXPORT_SYMBOL(nobh_commit_write); |
| 2513 | |
| 2514 | /* |
| 2515 | * nobh_writepage() - based on block_full_write_page() except |
| 2516 | * that it tries to operate without attaching bufferheads to |
| 2517 | * the page. |
| 2518 | */ |
| 2519 | int nobh_writepage(struct page *page, get_block_t *get_block, |
| 2520 | struct writeback_control *wbc) |
| 2521 | { |
| 2522 | struct inode * const inode = page->mapping->host; |
| 2523 | loff_t i_size = i_size_read(inode); |
| 2524 | const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT; |
| 2525 | unsigned offset; |
| 2526 | void *kaddr; |
| 2527 | int ret; |
| 2528 | |
| 2529 | /* Is the page fully inside i_size? */ |
| 2530 | if (page->index < end_index) |
| 2531 | goto out; |
| 2532 | |
| 2533 | /* Is the page fully outside i_size? (truncate in progress) */ |
| 2534 | offset = i_size & (PAGE_CACHE_SIZE-1); |
| 2535 | if (page->index >= end_index+1 || !offset) { |
| 2536 | /* |
| 2537 | * The page may have dirty, unmapped buffers. For example, |
| 2538 | * they may have been added in ext3_writepage(). Make them |
| 2539 | * freeable here, so the page does not leak. |
| 2540 | */ |
| 2541 | #if 0 |
| 2542 | /* Not really sure about this - do we need this ? */ |
| 2543 | if (page->mapping->a_ops->invalidatepage) |
| 2544 | page->mapping->a_ops->invalidatepage(page, offset); |
| 2545 | #endif |
| 2546 | unlock_page(page); |
| 2547 | return 0; /* don't care */ |
| 2548 | } |
| 2549 | |
| 2550 | /* |
| 2551 | * The page straddles i_size. It must be zeroed out on each and every |
| 2552 | * writepage invocation because it may be mmapped. "A file is mapped |
| 2553 | * in multiples of the page size. For a file that is not a multiple of |
| 2554 | * the page size, the remaining memory is zeroed when mapped, and |
| 2555 | * writes to that region are not written out to the file." |
| 2556 | */ |
| 2557 | kaddr = kmap_atomic(page, KM_USER0); |
| 2558 | memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset); |
| 2559 | flush_dcache_page(page); |
| 2560 | kunmap_atomic(kaddr, KM_USER0); |
| 2561 | out: |
| 2562 | ret = mpage_writepage(page, get_block, wbc); |
| 2563 | if (ret == -EAGAIN) |
| 2564 | ret = __block_write_full_page(inode, page, get_block, wbc); |
| 2565 | return ret; |
| 2566 | } |
| 2567 | EXPORT_SYMBOL(nobh_writepage); |
| 2568 | |
| 2569 | /* |
| 2570 | * This function assumes that ->prepare_write() uses nobh_prepare_write(). |
| 2571 | */ |
| 2572 | int nobh_truncate_page(struct address_space *mapping, loff_t from) |
| 2573 | { |
| 2574 | struct inode *inode = mapping->host; |
| 2575 | unsigned blocksize = 1 << inode->i_blkbits; |
| 2576 | pgoff_t index = from >> PAGE_CACHE_SHIFT; |
| 2577 | unsigned offset = from & (PAGE_CACHE_SIZE-1); |
| 2578 | unsigned to; |
| 2579 | struct page *page; |
| 2580 | struct address_space_operations *a_ops = mapping->a_ops; |
| 2581 | char *kaddr; |
| 2582 | int ret = 0; |
| 2583 | |
| 2584 | if ((offset & (blocksize - 1)) == 0) |
| 2585 | goto out; |
| 2586 | |
| 2587 | ret = -ENOMEM; |
| 2588 | page = grab_cache_page(mapping, index); |
| 2589 | if (!page) |
| 2590 | goto out; |
| 2591 | |
| 2592 | to = (offset + blocksize) & ~(blocksize - 1); |
| 2593 | ret = a_ops->prepare_write(NULL, page, offset, to); |
| 2594 | if (ret == 0) { |
| 2595 | kaddr = kmap_atomic(page, KM_USER0); |
| 2596 | memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset); |
| 2597 | flush_dcache_page(page); |
| 2598 | kunmap_atomic(kaddr, KM_USER0); |
| 2599 | set_page_dirty(page); |
| 2600 | } |
| 2601 | unlock_page(page); |
| 2602 | page_cache_release(page); |
| 2603 | out: |
| 2604 | return ret; |
| 2605 | } |
| 2606 | EXPORT_SYMBOL(nobh_truncate_page); |
| 2607 | |
| 2608 | int block_truncate_page(struct address_space *mapping, |
| 2609 | loff_t from, get_block_t *get_block) |
| 2610 | { |
| 2611 | pgoff_t index = from >> PAGE_CACHE_SHIFT; |
| 2612 | unsigned offset = from & (PAGE_CACHE_SIZE-1); |
| 2613 | unsigned blocksize; |
| 2614 | pgoff_t iblock; |
| 2615 | unsigned length, pos; |
| 2616 | struct inode *inode = mapping->host; |
| 2617 | struct page *page; |
| 2618 | struct buffer_head *bh; |
| 2619 | void *kaddr; |
| 2620 | int err; |
| 2621 | |
| 2622 | blocksize = 1 << inode->i_blkbits; |
| 2623 | length = offset & (blocksize - 1); |
| 2624 | |
| 2625 | /* Block boundary? Nothing to do */ |
| 2626 | if (!length) |
| 2627 | return 0; |
| 2628 | |
| 2629 | length = blocksize - length; |
| 2630 | iblock = index << (PAGE_CACHE_SHIFT - inode->i_blkbits); |
| 2631 | |
| 2632 | page = grab_cache_page(mapping, index); |
| 2633 | err = -ENOMEM; |
| 2634 | if (!page) |
| 2635 | goto out; |
| 2636 | |
| 2637 | if (!page_has_buffers(page)) |
| 2638 | create_empty_buffers(page, blocksize, 0); |
| 2639 | |
| 2640 | /* Find the buffer that contains "offset" */ |
| 2641 | bh = page_buffers(page); |
| 2642 | pos = blocksize; |
| 2643 | while (offset >= pos) { |
| 2644 | bh = bh->b_this_page; |
| 2645 | iblock++; |
| 2646 | pos += blocksize; |
| 2647 | } |
| 2648 | |
| 2649 | err = 0; |
| 2650 | if (!buffer_mapped(bh)) { |
| 2651 | err = get_block(inode, iblock, bh, 0); |
| 2652 | if (err) |
| 2653 | goto unlock; |
| 2654 | /* unmapped? It's a hole - nothing to do */ |
| 2655 | if (!buffer_mapped(bh)) |
| 2656 | goto unlock; |
| 2657 | } |
| 2658 | |
| 2659 | /* Ok, it's mapped. Make sure it's up-to-date */ |
| 2660 | if (PageUptodate(page)) |
| 2661 | set_buffer_uptodate(bh); |
| 2662 | |
| 2663 | if (!buffer_uptodate(bh) && !buffer_delay(bh)) { |
| 2664 | err = -EIO; |
| 2665 | ll_rw_block(READ, 1, &bh); |
| 2666 | wait_on_buffer(bh); |
| 2667 | /* Uhhuh. Read error. Complain and punt. */ |
| 2668 | if (!buffer_uptodate(bh)) |
| 2669 | goto unlock; |
| 2670 | } |
| 2671 | |
| 2672 | kaddr = kmap_atomic(page, KM_USER0); |
| 2673 | memset(kaddr + offset, 0, length); |
| 2674 | flush_dcache_page(page); |
| 2675 | kunmap_atomic(kaddr, KM_USER0); |
| 2676 | |
| 2677 | mark_buffer_dirty(bh); |
| 2678 | err = 0; |
| 2679 | |
| 2680 | unlock: |
| 2681 | unlock_page(page); |
| 2682 | page_cache_release(page); |
| 2683 | out: |
| 2684 | return err; |
| 2685 | } |
| 2686 | |
| 2687 | /* |
| 2688 | * The generic ->writepage function for buffer-backed address_spaces |
| 2689 | */ |
| 2690 | int block_write_full_page(struct page *page, get_block_t *get_block, |
| 2691 | struct writeback_control *wbc) |
| 2692 | { |
| 2693 | struct inode * const inode = page->mapping->host; |
| 2694 | loff_t i_size = i_size_read(inode); |
| 2695 | const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT; |
| 2696 | unsigned offset; |
| 2697 | void *kaddr; |
| 2698 | |
| 2699 | /* Is the page fully inside i_size? */ |
| 2700 | if (page->index < end_index) |
| 2701 | return __block_write_full_page(inode, page, get_block, wbc); |
| 2702 | |
| 2703 | /* Is the page fully outside i_size? (truncate in progress) */ |
| 2704 | offset = i_size & (PAGE_CACHE_SIZE-1); |
| 2705 | if (page->index >= end_index+1 || !offset) { |
| 2706 | /* |
| 2707 | * The page may have dirty, unmapped buffers. For example, |
| 2708 | * they may have been added in ext3_writepage(). Make them |
| 2709 | * freeable here, so the page does not leak. |
| 2710 | */ |
| 2711 | block_invalidatepage(page, 0); |
| 2712 | unlock_page(page); |
| 2713 | return 0; /* don't care */ |
| 2714 | } |
| 2715 | |
| 2716 | /* |
| 2717 | * The page straddles i_size. It must be zeroed out on each and every |
| 2718 | * writepage invokation because it may be mmapped. "A file is mapped |
| 2719 | * in multiples of the page size. For a file that is not a multiple of |
| 2720 | * the page size, the remaining memory is zeroed when mapped, and |
| 2721 | * writes to that region are not written out to the file." |
| 2722 | */ |
| 2723 | kaddr = kmap_atomic(page, KM_USER0); |
| 2724 | memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset); |
| 2725 | flush_dcache_page(page); |
| 2726 | kunmap_atomic(kaddr, KM_USER0); |
| 2727 | return __block_write_full_page(inode, page, get_block, wbc); |
| 2728 | } |
| 2729 | |
| 2730 | sector_t generic_block_bmap(struct address_space *mapping, sector_t block, |
| 2731 | get_block_t *get_block) |
| 2732 | { |
| 2733 | struct buffer_head tmp; |
| 2734 | struct inode *inode = mapping->host; |
| 2735 | tmp.b_state = 0; |
| 2736 | tmp.b_blocknr = 0; |
| 2737 | get_block(inode, block, &tmp, 0); |
| 2738 | return tmp.b_blocknr; |
| 2739 | } |
| 2740 | |
| 2741 | static int end_bio_bh_io_sync(struct bio *bio, unsigned int bytes_done, int err) |
| 2742 | { |
| 2743 | struct buffer_head *bh = bio->bi_private; |
| 2744 | |
| 2745 | if (bio->bi_size) |
| 2746 | return 1; |
| 2747 | |
| 2748 | if (err == -EOPNOTSUPP) { |
| 2749 | set_bit(BIO_EOPNOTSUPP, &bio->bi_flags); |
| 2750 | set_bit(BH_Eopnotsupp, &bh->b_state); |
| 2751 | } |
| 2752 | |
| 2753 | bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags)); |
| 2754 | bio_put(bio); |
| 2755 | return 0; |
| 2756 | } |
| 2757 | |
| 2758 | int submit_bh(int rw, struct buffer_head * bh) |
| 2759 | { |
| 2760 | struct bio *bio; |
| 2761 | int ret = 0; |
| 2762 | |
| 2763 | BUG_ON(!buffer_locked(bh)); |
| 2764 | BUG_ON(!buffer_mapped(bh)); |
| 2765 | BUG_ON(!bh->b_end_io); |
| 2766 | |
| 2767 | if (buffer_ordered(bh) && (rw == WRITE)) |
| 2768 | rw = WRITE_BARRIER; |
| 2769 | |
| 2770 | /* |
| 2771 | * Only clear out a write error when rewriting, should this |
| 2772 | * include WRITE_SYNC as well? |
| 2773 | */ |
| 2774 | if (test_set_buffer_req(bh) && (rw == WRITE || rw == WRITE_BARRIER)) |
| 2775 | clear_buffer_write_io_error(bh); |
| 2776 | |
| 2777 | /* |
| 2778 | * from here on down, it's all bio -- do the initial mapping, |
| 2779 | * submit_bio -> generic_make_request may further map this bio around |
| 2780 | */ |
| 2781 | bio = bio_alloc(GFP_NOIO, 1); |
| 2782 | |
| 2783 | bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9); |
| 2784 | bio->bi_bdev = bh->b_bdev; |
| 2785 | bio->bi_io_vec[0].bv_page = bh->b_page; |
| 2786 | bio->bi_io_vec[0].bv_len = bh->b_size; |
| 2787 | bio->bi_io_vec[0].bv_offset = bh_offset(bh); |
| 2788 | |
| 2789 | bio->bi_vcnt = 1; |
| 2790 | bio->bi_idx = 0; |
| 2791 | bio->bi_size = bh->b_size; |
| 2792 | |
| 2793 | bio->bi_end_io = end_bio_bh_io_sync; |
| 2794 | bio->bi_private = bh; |
| 2795 | |
| 2796 | bio_get(bio); |
| 2797 | submit_bio(rw, bio); |
| 2798 | |
| 2799 | if (bio_flagged(bio, BIO_EOPNOTSUPP)) |
| 2800 | ret = -EOPNOTSUPP; |
| 2801 | |
| 2802 | bio_put(bio); |
| 2803 | return ret; |
| 2804 | } |
| 2805 | |
| 2806 | /** |
| 2807 | * ll_rw_block: low-level access to block devices (DEPRECATED) |
| 2808 | * @rw: whether to %READ or %WRITE or maybe %READA (readahead) |
| 2809 | * @nr: number of &struct buffer_heads in the array |
| 2810 | * @bhs: array of pointers to &struct buffer_head |
| 2811 | * |
| 2812 | * ll_rw_block() takes an array of pointers to &struct buffer_heads, |
| 2813 | * and requests an I/O operation on them, either a %READ or a %WRITE. |
| 2814 | * The third %READA option is described in the documentation for |
| 2815 | * generic_make_request() which ll_rw_block() calls. |
| 2816 | * |
| 2817 | * This function drops any buffer that it cannot get a lock on (with the |
| 2818 | * BH_Lock state bit), any buffer that appears to be clean when doing a |
| 2819 | * write request, and any buffer that appears to be up-to-date when doing |
| 2820 | * read request. Further it marks as clean buffers that are processed for |
| 2821 | * writing (the buffer cache won't assume that they are actually clean until |
| 2822 | * the buffer gets unlocked). |
| 2823 | * |
| 2824 | * ll_rw_block sets b_end_io to simple completion handler that marks |
| 2825 | * the buffer up-to-date (if approriate), unlocks the buffer and wakes |
| 2826 | * any waiters. |
| 2827 | * |
| 2828 | * All of the buffers must be for the same device, and must also be a |
| 2829 | * multiple of the current approved size for the device. |
| 2830 | */ |
| 2831 | void ll_rw_block(int rw, int nr, struct buffer_head *bhs[]) |
| 2832 | { |
| 2833 | int i; |
| 2834 | |
| 2835 | for (i = 0; i < nr; i++) { |
| 2836 | struct buffer_head *bh = bhs[i]; |
| 2837 | |
| 2838 | if (test_set_buffer_locked(bh)) |
| 2839 | continue; |
| 2840 | |
| 2841 | get_bh(bh); |
| 2842 | if (rw == WRITE) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2843 | if (test_clear_buffer_dirty(bh)) { |
akpm@osdl.org | 76c3073 | 2005-04-16 15:24:07 -0700 | [diff] [blame] | 2844 | bh->b_end_io = end_buffer_write_sync; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2845 | submit_bh(WRITE, bh); |
| 2846 | continue; |
| 2847 | } |
| 2848 | } else { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2849 | if (!buffer_uptodate(bh)) { |
akpm@osdl.org | 76c3073 | 2005-04-16 15:24:07 -0700 | [diff] [blame] | 2850 | bh->b_end_io = end_buffer_read_sync; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2851 | submit_bh(rw, bh); |
| 2852 | continue; |
| 2853 | } |
| 2854 | } |
| 2855 | unlock_buffer(bh); |
| 2856 | put_bh(bh); |
| 2857 | } |
| 2858 | } |
| 2859 | |
| 2860 | /* |
| 2861 | * For a data-integrity writeout, we need to wait upon any in-progress I/O |
| 2862 | * and then start new I/O and then wait upon it. The caller must have a ref on |
| 2863 | * the buffer_head. |
| 2864 | */ |
| 2865 | int sync_dirty_buffer(struct buffer_head *bh) |
| 2866 | { |
| 2867 | int ret = 0; |
| 2868 | |
| 2869 | WARN_ON(atomic_read(&bh->b_count) < 1); |
| 2870 | lock_buffer(bh); |
| 2871 | if (test_clear_buffer_dirty(bh)) { |
| 2872 | get_bh(bh); |
| 2873 | bh->b_end_io = end_buffer_write_sync; |
| 2874 | ret = submit_bh(WRITE, bh); |
| 2875 | wait_on_buffer(bh); |
| 2876 | if (buffer_eopnotsupp(bh)) { |
| 2877 | clear_buffer_eopnotsupp(bh); |
| 2878 | ret = -EOPNOTSUPP; |
| 2879 | } |
| 2880 | if (!ret && !buffer_uptodate(bh)) |
| 2881 | ret = -EIO; |
| 2882 | } else { |
| 2883 | unlock_buffer(bh); |
| 2884 | } |
| 2885 | return ret; |
| 2886 | } |
| 2887 | |
| 2888 | /* |
| 2889 | * try_to_free_buffers() checks if all the buffers on this particular page |
| 2890 | * are unused, and releases them if so. |
| 2891 | * |
| 2892 | * Exclusion against try_to_free_buffers may be obtained by either |
| 2893 | * locking the page or by holding its mapping's private_lock. |
| 2894 | * |
| 2895 | * If the page is dirty but all the buffers are clean then we need to |
| 2896 | * be sure to mark the page clean as well. This is because the page |
| 2897 | * may be against a block device, and a later reattachment of buffers |
| 2898 | * to a dirty page will set *all* buffers dirty. Which would corrupt |
| 2899 | * filesystem data on the same device. |
| 2900 | * |
| 2901 | * The same applies to regular filesystem pages: if all the buffers are |
| 2902 | * clean then we set the page clean and proceed. To do that, we require |
| 2903 | * total exclusion from __set_page_dirty_buffers(). That is obtained with |
| 2904 | * private_lock. |
| 2905 | * |
| 2906 | * try_to_free_buffers() is non-blocking. |
| 2907 | */ |
| 2908 | static inline int buffer_busy(struct buffer_head *bh) |
| 2909 | { |
| 2910 | return atomic_read(&bh->b_count) | |
| 2911 | (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock))); |
| 2912 | } |
| 2913 | |
| 2914 | static int |
| 2915 | drop_buffers(struct page *page, struct buffer_head **buffers_to_free) |
| 2916 | { |
| 2917 | struct buffer_head *head = page_buffers(page); |
| 2918 | struct buffer_head *bh; |
| 2919 | |
| 2920 | bh = head; |
| 2921 | do { |
akpm@osdl.org | de7d5a3 | 2005-05-01 08:58:39 -0700 | [diff] [blame] | 2922 | if (buffer_write_io_error(bh) && page->mapping) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2923 | set_bit(AS_EIO, &page->mapping->flags); |
| 2924 | if (buffer_busy(bh)) |
| 2925 | goto failed; |
| 2926 | bh = bh->b_this_page; |
| 2927 | } while (bh != head); |
| 2928 | |
| 2929 | do { |
| 2930 | struct buffer_head *next = bh->b_this_page; |
| 2931 | |
| 2932 | if (!list_empty(&bh->b_assoc_buffers)) |
| 2933 | __remove_assoc_queue(bh); |
| 2934 | bh = next; |
| 2935 | } while (bh != head); |
| 2936 | *buffers_to_free = head; |
| 2937 | __clear_page_buffers(page); |
| 2938 | return 1; |
| 2939 | failed: |
| 2940 | return 0; |
| 2941 | } |
| 2942 | |
| 2943 | int try_to_free_buffers(struct page *page) |
| 2944 | { |
| 2945 | struct address_space * const mapping = page->mapping; |
| 2946 | struct buffer_head *buffers_to_free = NULL; |
| 2947 | int ret = 0; |
| 2948 | |
| 2949 | BUG_ON(!PageLocked(page)); |
| 2950 | if (PageWriteback(page)) |
| 2951 | return 0; |
| 2952 | |
| 2953 | if (mapping == NULL) { /* can this still happen? */ |
| 2954 | ret = drop_buffers(page, &buffers_to_free); |
| 2955 | goto out; |
| 2956 | } |
| 2957 | |
| 2958 | spin_lock(&mapping->private_lock); |
| 2959 | ret = drop_buffers(page, &buffers_to_free); |
| 2960 | if (ret) { |
| 2961 | /* |
| 2962 | * If the filesystem writes its buffers by hand (eg ext3) |
| 2963 | * then we can have clean buffers against a dirty page. We |
| 2964 | * clean the page here; otherwise later reattachment of buffers |
| 2965 | * could encounter a non-uptodate page, which is unresolvable. |
| 2966 | * This only applies in the rare case where try_to_free_buffers |
| 2967 | * succeeds but the page is not freed. |
| 2968 | */ |
| 2969 | clear_page_dirty(page); |
| 2970 | } |
| 2971 | spin_unlock(&mapping->private_lock); |
| 2972 | out: |
| 2973 | if (buffers_to_free) { |
| 2974 | struct buffer_head *bh = buffers_to_free; |
| 2975 | |
| 2976 | do { |
| 2977 | struct buffer_head *next = bh->b_this_page; |
| 2978 | free_buffer_head(bh); |
| 2979 | bh = next; |
| 2980 | } while (bh != buffers_to_free); |
| 2981 | } |
| 2982 | return ret; |
| 2983 | } |
| 2984 | EXPORT_SYMBOL(try_to_free_buffers); |
| 2985 | |
| 2986 | int block_sync_page(struct page *page) |
| 2987 | { |
| 2988 | struct address_space *mapping; |
| 2989 | |
| 2990 | smp_mb(); |
| 2991 | mapping = page_mapping(page); |
| 2992 | if (mapping) |
| 2993 | blk_run_backing_dev(mapping->backing_dev_info, page); |
| 2994 | return 0; |
| 2995 | } |
| 2996 | |
| 2997 | /* |
| 2998 | * There are no bdflush tunables left. But distributions are |
| 2999 | * still running obsolete flush daemons, so we terminate them here. |
| 3000 | * |
| 3001 | * Use of bdflush() is deprecated and will be removed in a future kernel. |
| 3002 | * The `pdflush' kernel threads fully replace bdflush daemons and this call. |
| 3003 | */ |
| 3004 | asmlinkage long sys_bdflush(int func, long data) |
| 3005 | { |
| 3006 | static int msg_count; |
| 3007 | |
| 3008 | if (!capable(CAP_SYS_ADMIN)) |
| 3009 | return -EPERM; |
| 3010 | |
| 3011 | if (msg_count < 5) { |
| 3012 | msg_count++; |
| 3013 | printk(KERN_INFO |
| 3014 | "warning: process `%s' used the obsolete bdflush" |
| 3015 | " system call\n", current->comm); |
| 3016 | printk(KERN_INFO "Fix your initscripts?\n"); |
| 3017 | } |
| 3018 | |
| 3019 | if (func == 1) |
| 3020 | do_exit(0); |
| 3021 | return 0; |
| 3022 | } |
| 3023 | |
| 3024 | /* |
| 3025 | * Buffer-head allocation |
| 3026 | */ |
| 3027 | static kmem_cache_t *bh_cachep; |
| 3028 | |
| 3029 | /* |
| 3030 | * Once the number of bh's in the machine exceeds this level, we start |
| 3031 | * stripping them in writeback. |
| 3032 | */ |
| 3033 | static int max_buffer_heads; |
| 3034 | |
| 3035 | int buffer_heads_over_limit; |
| 3036 | |
| 3037 | struct bh_accounting { |
| 3038 | int nr; /* Number of live bh's */ |
| 3039 | int ratelimit; /* Limit cacheline bouncing */ |
| 3040 | }; |
| 3041 | |
| 3042 | static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0}; |
| 3043 | |
| 3044 | static void recalc_bh_state(void) |
| 3045 | { |
| 3046 | int i; |
| 3047 | int tot = 0; |
| 3048 | |
| 3049 | if (__get_cpu_var(bh_accounting).ratelimit++ < 4096) |
| 3050 | return; |
| 3051 | __get_cpu_var(bh_accounting).ratelimit = 0; |
| 3052 | for_each_cpu(i) |
| 3053 | tot += per_cpu(bh_accounting, i).nr; |
| 3054 | buffer_heads_over_limit = (tot > max_buffer_heads); |
| 3055 | } |
| 3056 | |
| 3057 | struct buffer_head *alloc_buffer_head(unsigned int __nocast gfp_flags) |
| 3058 | { |
| 3059 | struct buffer_head *ret = kmem_cache_alloc(bh_cachep, gfp_flags); |
| 3060 | if (ret) { |
| 3061 | preempt_disable(); |
| 3062 | __get_cpu_var(bh_accounting).nr++; |
| 3063 | recalc_bh_state(); |
| 3064 | preempt_enable(); |
| 3065 | } |
| 3066 | return ret; |
| 3067 | } |
| 3068 | EXPORT_SYMBOL(alloc_buffer_head); |
| 3069 | |
| 3070 | void free_buffer_head(struct buffer_head *bh) |
| 3071 | { |
| 3072 | BUG_ON(!list_empty(&bh->b_assoc_buffers)); |
| 3073 | kmem_cache_free(bh_cachep, bh); |
| 3074 | preempt_disable(); |
| 3075 | __get_cpu_var(bh_accounting).nr--; |
| 3076 | recalc_bh_state(); |
| 3077 | preempt_enable(); |
| 3078 | } |
| 3079 | EXPORT_SYMBOL(free_buffer_head); |
| 3080 | |
| 3081 | static void |
| 3082 | init_buffer_head(void *data, kmem_cache_t *cachep, unsigned long flags) |
| 3083 | { |
| 3084 | if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) == |
| 3085 | SLAB_CTOR_CONSTRUCTOR) { |
| 3086 | struct buffer_head * bh = (struct buffer_head *)data; |
| 3087 | |
| 3088 | memset(bh, 0, sizeof(*bh)); |
| 3089 | INIT_LIST_HEAD(&bh->b_assoc_buffers); |
| 3090 | } |
| 3091 | } |
| 3092 | |
| 3093 | #ifdef CONFIG_HOTPLUG_CPU |
| 3094 | static void buffer_exit_cpu(int cpu) |
| 3095 | { |
| 3096 | int i; |
| 3097 | struct bh_lru *b = &per_cpu(bh_lrus, cpu); |
| 3098 | |
| 3099 | for (i = 0; i < BH_LRU_SIZE; i++) { |
| 3100 | brelse(b->bhs[i]); |
| 3101 | b->bhs[i] = NULL; |
| 3102 | } |
| 3103 | } |
| 3104 | |
| 3105 | static int buffer_cpu_notify(struct notifier_block *self, |
| 3106 | unsigned long action, void *hcpu) |
| 3107 | { |
| 3108 | if (action == CPU_DEAD) |
| 3109 | buffer_exit_cpu((unsigned long)hcpu); |
| 3110 | return NOTIFY_OK; |
| 3111 | } |
| 3112 | #endif /* CONFIG_HOTPLUG_CPU */ |
| 3113 | |
| 3114 | void __init buffer_init(void) |
| 3115 | { |
| 3116 | int nrpages; |
| 3117 | |
| 3118 | bh_cachep = kmem_cache_create("buffer_head", |
| 3119 | sizeof(struct buffer_head), 0, |
Andrea Arcangeli | e422fd2 | 2005-05-05 16:15:04 -0700 | [diff] [blame] | 3120 | SLAB_RECLAIM_ACCOUNT|SLAB_PANIC, init_buffer_head, NULL); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3121 | |
| 3122 | /* |
| 3123 | * Limit the bh occupancy to 10% of ZONE_NORMAL |
| 3124 | */ |
| 3125 | nrpages = (nr_free_buffer_pages() * 10) / 100; |
| 3126 | max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head)); |
| 3127 | hotcpu_notifier(buffer_cpu_notify, 0); |
| 3128 | } |
| 3129 | |
| 3130 | EXPORT_SYMBOL(__bforget); |
| 3131 | EXPORT_SYMBOL(__brelse); |
| 3132 | EXPORT_SYMBOL(__wait_on_buffer); |
| 3133 | EXPORT_SYMBOL(block_commit_write); |
| 3134 | EXPORT_SYMBOL(block_prepare_write); |
| 3135 | EXPORT_SYMBOL(block_read_full_page); |
| 3136 | EXPORT_SYMBOL(block_sync_page); |
| 3137 | EXPORT_SYMBOL(block_truncate_page); |
| 3138 | EXPORT_SYMBOL(block_write_full_page); |
| 3139 | EXPORT_SYMBOL(cont_prepare_write); |
| 3140 | EXPORT_SYMBOL(end_buffer_async_write); |
| 3141 | EXPORT_SYMBOL(end_buffer_read_sync); |
| 3142 | EXPORT_SYMBOL(end_buffer_write_sync); |
| 3143 | EXPORT_SYMBOL(file_fsync); |
| 3144 | EXPORT_SYMBOL(fsync_bdev); |
| 3145 | EXPORT_SYMBOL(generic_block_bmap); |
| 3146 | EXPORT_SYMBOL(generic_commit_write); |
| 3147 | EXPORT_SYMBOL(generic_cont_expand); |
| 3148 | EXPORT_SYMBOL(init_buffer); |
| 3149 | EXPORT_SYMBOL(invalidate_bdev); |
| 3150 | EXPORT_SYMBOL(ll_rw_block); |
| 3151 | EXPORT_SYMBOL(mark_buffer_dirty); |
| 3152 | EXPORT_SYMBOL(submit_bh); |
| 3153 | EXPORT_SYMBOL(sync_dirty_buffer); |
| 3154 | EXPORT_SYMBOL(unlock_buffer); |