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