| 1 | /* |
| 2 | * linux/fs/buffer.c |
| 3 | * |
| 4 | * Copyright (C) 1991, 1992, 2002 Linus Torvalds |
| 5 | */ |
| 6 | |
| 7 | /* |
| 8 | * Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95 |
| 9 | * |
| 10 | * Removed a lot of unnecessary code and simplified things now that |
| 11 | * the buffer cache isn't our primary cache - Andrew Tridgell 12/96 |
| 12 | * |
| 13 | * Speed up hash, lru, and free list operations. Use gfp() for allocating |
| 14 | * hash table, use SLAB cache for buffer heads. SMP threading. -DaveM |
| 15 | * |
| 16 | * Added 32k buffer block sizes - these are required older ARM systems. - RMK |
| 17 | * |
| 18 | * async buffer flushing, 1999 Andrea Arcangeli <andrea@suse.de> |
| 19 | */ |
| 20 | |
| 21 | #include <linux/kernel.h> |
| 22 | #include <linux/syscalls.h> |
| 23 | #include <linux/fs.h> |
| 24 | #include <linux/mm.h> |
| 25 | #include <linux/percpu.h> |
| 26 | #include <linux/slab.h> |
| 27 | #include <linux/capability.h> |
| 28 | #include <linux/blkdev.h> |
| 29 | #include <linux/file.h> |
| 30 | #include <linux/quotaops.h> |
| 31 | #include <linux/highmem.h> |
| 32 | #include <linux/export.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 | #include <trace/events/block.h> |
| 45 | |
| 46 | static int fsync_buffers_list(spinlock_t *lock, struct list_head *list); |
| 47 | |
| 48 | #define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers) |
| 49 | |
| 50 | void init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private) |
| 51 | { |
| 52 | bh->b_end_io = handler; |
| 53 | bh->b_private = private; |
| 54 | } |
| 55 | EXPORT_SYMBOL(init_buffer); |
| 56 | |
| 57 | inline void touch_buffer(struct buffer_head *bh) |
| 58 | { |
| 59 | trace_block_touch_buffer(bh); |
| 60 | mark_page_accessed(bh->b_page); |
| 61 | } |
| 62 | EXPORT_SYMBOL(touch_buffer); |
| 63 | |
| 64 | void __lock_buffer(struct buffer_head *bh) |
| 65 | { |
| 66 | wait_on_bit_lock_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE); |
| 67 | } |
| 68 | EXPORT_SYMBOL(__lock_buffer); |
| 69 | |
| 70 | void unlock_buffer(struct buffer_head *bh) |
| 71 | { |
| 72 | clear_bit_unlock(BH_Lock, &bh->b_state); |
| 73 | smp_mb__after_atomic(); |
| 74 | wake_up_bit(&bh->b_state, BH_Lock); |
| 75 | } |
| 76 | EXPORT_SYMBOL(unlock_buffer); |
| 77 | |
| 78 | /* |
| 79 | * Returns if the page has dirty or writeback buffers. If all the buffers |
| 80 | * are unlocked and clean then the PageDirty information is stale. If |
| 81 | * any of the pages are locked, it is assumed they are locked for IO. |
| 82 | */ |
| 83 | void buffer_check_dirty_writeback(struct page *page, |
| 84 | bool *dirty, bool *writeback) |
| 85 | { |
| 86 | struct buffer_head *head, *bh; |
| 87 | *dirty = false; |
| 88 | *writeback = false; |
| 89 | |
| 90 | BUG_ON(!PageLocked(page)); |
| 91 | |
| 92 | if (!page_has_buffers(page)) |
| 93 | return; |
| 94 | |
| 95 | if (PageWriteback(page)) |
| 96 | *writeback = true; |
| 97 | |
| 98 | head = page_buffers(page); |
| 99 | bh = head; |
| 100 | do { |
| 101 | if (buffer_locked(bh)) |
| 102 | *writeback = true; |
| 103 | |
| 104 | if (buffer_dirty(bh)) |
| 105 | *dirty = true; |
| 106 | |
| 107 | bh = bh->b_this_page; |
| 108 | } while (bh != head); |
| 109 | } |
| 110 | EXPORT_SYMBOL(buffer_check_dirty_writeback); |
| 111 | |
| 112 | /* |
| 113 | * Block until a buffer comes unlocked. This doesn't stop it |
| 114 | * from becoming locked again - you have to lock it yourself |
| 115 | * if you want to preserve its state. |
| 116 | */ |
| 117 | void __wait_on_buffer(struct buffer_head * bh) |
| 118 | { |
| 119 | wait_on_bit_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE); |
| 120 | } |
| 121 | EXPORT_SYMBOL(__wait_on_buffer); |
| 122 | |
| 123 | static void |
| 124 | __clear_page_buffers(struct page *page) |
| 125 | { |
| 126 | ClearPagePrivate(page); |
| 127 | set_page_private(page, 0); |
| 128 | page_cache_release(page); |
| 129 | } |
| 130 | |
| 131 | static void buffer_io_error(struct buffer_head *bh, char *msg) |
| 132 | { |
| 133 | char b[BDEVNAME_SIZE]; |
| 134 | |
| 135 | if (!test_bit(BH_Quiet, &bh->b_state)) |
| 136 | printk_ratelimited(KERN_ERR |
| 137 | "Buffer I/O error on dev %s, logical block %llu%s\n", |
| 138 | bdevname(bh->b_bdev, b), |
| 139 | (unsigned long long)bh->b_blocknr, msg); |
| 140 | } |
| 141 | |
| 142 | /* |
| 143 | * End-of-IO handler helper function which does not touch the bh after |
| 144 | * unlocking it. |
| 145 | * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but |
| 146 | * a race there is benign: unlock_buffer() only use the bh's address for |
| 147 | * hashing after unlocking the buffer, so it doesn't actually touch the bh |
| 148 | * itself. |
| 149 | */ |
| 150 | static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate) |
| 151 | { |
| 152 | if (uptodate) { |
| 153 | set_buffer_uptodate(bh); |
| 154 | } else { |
| 155 | /* This happens, due to failed READA attempts. */ |
| 156 | clear_buffer_uptodate(bh); |
| 157 | } |
| 158 | unlock_buffer(bh); |
| 159 | } |
| 160 | |
| 161 | /* |
| 162 | * Default synchronous end-of-IO handler.. Just mark it up-to-date and |
| 163 | * unlock the buffer. This is what ll_rw_block uses too. |
| 164 | */ |
| 165 | void end_buffer_read_sync(struct buffer_head *bh, int uptodate) |
| 166 | { |
| 167 | __end_buffer_read_notouch(bh, uptodate); |
| 168 | put_bh(bh); |
| 169 | } |
| 170 | EXPORT_SYMBOL(end_buffer_read_sync); |
| 171 | |
| 172 | void end_buffer_write_sync(struct buffer_head *bh, int uptodate) |
| 173 | { |
| 174 | if (uptodate) { |
| 175 | set_buffer_uptodate(bh); |
| 176 | } else { |
| 177 | buffer_io_error(bh, ", lost sync page write"); |
| 178 | set_buffer_write_io_error(bh); |
| 179 | clear_buffer_uptodate(bh); |
| 180 | } |
| 181 | unlock_buffer(bh); |
| 182 | put_bh(bh); |
| 183 | } |
| 184 | EXPORT_SYMBOL(end_buffer_write_sync); |
| 185 | |
| 186 | /* |
| 187 | * Various filesystems appear to want __find_get_block to be non-blocking. |
| 188 | * But it's the page lock which protects the buffers. To get around this, |
| 189 | * we get exclusion from try_to_free_buffers with the blockdev mapping's |
| 190 | * private_lock. |
| 191 | * |
| 192 | * Hack idea: for the blockdev mapping, i_bufferlist_lock contention |
| 193 | * may be quite high. This code could TryLock the page, and if that |
| 194 | * succeeds, there is no need to take private_lock. (But if |
| 195 | * private_lock is contended then so is mapping->tree_lock). |
| 196 | */ |
| 197 | static struct buffer_head * |
| 198 | __find_get_block_slow(struct block_device *bdev, sector_t block) |
| 199 | { |
| 200 | struct inode *bd_inode = bdev->bd_inode; |
| 201 | struct address_space *bd_mapping = bd_inode->i_mapping; |
| 202 | struct buffer_head *ret = NULL; |
| 203 | pgoff_t index; |
| 204 | struct buffer_head *bh; |
| 205 | struct buffer_head *head; |
| 206 | struct page *page; |
| 207 | int all_mapped = 1; |
| 208 | |
| 209 | index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits); |
| 210 | page = find_get_page_flags(bd_mapping, index, FGP_ACCESSED); |
| 211 | if (!page) |
| 212 | goto out; |
| 213 | |
| 214 | spin_lock(&bd_mapping->private_lock); |
| 215 | if (!page_has_buffers(page)) |
| 216 | goto out_unlock; |
| 217 | head = page_buffers(page); |
| 218 | bh = head; |
| 219 | do { |
| 220 | if (!buffer_mapped(bh)) |
| 221 | all_mapped = 0; |
| 222 | else if (bh->b_blocknr == block) { |
| 223 | ret = bh; |
| 224 | get_bh(bh); |
| 225 | goto out_unlock; |
| 226 | } |
| 227 | bh = bh->b_this_page; |
| 228 | } while (bh != head); |
| 229 | |
| 230 | /* we might be here because some of the buffers on this page are |
| 231 | * not mapped. This is due to various races between |
| 232 | * file io on the block device and getblk. It gets dealt with |
| 233 | * elsewhere, don't buffer_error if we had some unmapped buffers |
| 234 | */ |
| 235 | if (all_mapped) { |
| 236 | char b[BDEVNAME_SIZE]; |
| 237 | |
| 238 | printk("__find_get_block_slow() failed. " |
| 239 | "block=%llu, b_blocknr=%llu\n", |
| 240 | (unsigned long long)block, |
| 241 | (unsigned long long)bh->b_blocknr); |
| 242 | printk("b_state=0x%08lx, b_size=%zu\n", |
| 243 | bh->b_state, bh->b_size); |
| 244 | printk("device %s blocksize: %d\n", bdevname(bdev, b), |
| 245 | 1 << bd_inode->i_blkbits); |
| 246 | } |
| 247 | out_unlock: |
| 248 | spin_unlock(&bd_mapping->private_lock); |
| 249 | page_cache_release(page); |
| 250 | out: |
| 251 | return ret; |
| 252 | } |
| 253 | |
| 254 | /* |
| 255 | * Kick the writeback threads then try to free up some ZONE_NORMAL memory. |
| 256 | */ |
| 257 | static void free_more_memory(void) |
| 258 | { |
| 259 | struct zone *zone; |
| 260 | int nid; |
| 261 | |
| 262 | wakeup_flusher_threads(1024, WB_REASON_FREE_MORE_MEM); |
| 263 | yield(); |
| 264 | |
| 265 | for_each_online_node(nid) { |
| 266 | (void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS), |
| 267 | gfp_zone(GFP_NOFS), NULL, |
| 268 | &zone); |
| 269 | if (zone) |
| 270 | try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0, |
| 271 | GFP_NOFS, NULL); |
| 272 | } |
| 273 | } |
| 274 | |
| 275 | /* |
| 276 | * I/O completion handler for block_read_full_page() - pages |
| 277 | * which come unlocked at the end of I/O. |
| 278 | */ |
| 279 | static void end_buffer_async_read(struct buffer_head *bh, int uptodate) |
| 280 | { |
| 281 | unsigned long flags; |
| 282 | struct buffer_head *first; |
| 283 | struct buffer_head *tmp; |
| 284 | struct page *page; |
| 285 | int page_uptodate = 1; |
| 286 | |
| 287 | BUG_ON(!buffer_async_read(bh)); |
| 288 | |
| 289 | page = bh->b_page; |
| 290 | if (uptodate) { |
| 291 | set_buffer_uptodate(bh); |
| 292 | } else { |
| 293 | clear_buffer_uptodate(bh); |
| 294 | buffer_io_error(bh, ", async page read"); |
| 295 | SetPageError(page); |
| 296 | } |
| 297 | |
| 298 | /* |
| 299 | * Be _very_ careful from here on. Bad things can happen if |
| 300 | * two buffer heads end IO at almost the same time and both |
| 301 | * decide that the page is now completely done. |
| 302 | */ |
| 303 | first = page_buffers(page); |
| 304 | local_irq_save(flags); |
| 305 | bit_spin_lock(BH_Uptodate_Lock, &first->b_state); |
| 306 | clear_buffer_async_read(bh); |
| 307 | unlock_buffer(bh); |
| 308 | tmp = bh; |
| 309 | do { |
| 310 | if (!buffer_uptodate(tmp)) |
| 311 | page_uptodate = 0; |
| 312 | if (buffer_async_read(tmp)) { |
| 313 | BUG_ON(!buffer_locked(tmp)); |
| 314 | goto still_busy; |
| 315 | } |
| 316 | tmp = tmp->b_this_page; |
| 317 | } while (tmp != bh); |
| 318 | bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); |
| 319 | local_irq_restore(flags); |
| 320 | |
| 321 | /* |
| 322 | * If none of the buffers had errors and they are all |
| 323 | * uptodate then we can set the page uptodate. |
| 324 | */ |
| 325 | if (page_uptodate && !PageError(page)) |
| 326 | SetPageUptodate(page); |
| 327 | unlock_page(page); |
| 328 | return; |
| 329 | |
| 330 | still_busy: |
| 331 | bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); |
| 332 | local_irq_restore(flags); |
| 333 | return; |
| 334 | } |
| 335 | |
| 336 | /* |
| 337 | * Completion handler for block_write_full_page() - pages which are unlocked |
| 338 | * during I/O, and which have PageWriteback cleared upon I/O completion. |
| 339 | */ |
| 340 | void end_buffer_async_write(struct buffer_head *bh, int uptodate) |
| 341 | { |
| 342 | unsigned long flags; |
| 343 | struct buffer_head *first; |
| 344 | struct buffer_head *tmp; |
| 345 | struct page *page; |
| 346 | |
| 347 | BUG_ON(!buffer_async_write(bh)); |
| 348 | |
| 349 | page = bh->b_page; |
| 350 | if (uptodate) { |
| 351 | set_buffer_uptodate(bh); |
| 352 | } else { |
| 353 | buffer_io_error(bh, ", lost async page write"); |
| 354 | set_bit(AS_EIO, &page->mapping->flags); |
| 355 | set_buffer_write_io_error(bh); |
| 356 | clear_buffer_uptodate(bh); |
| 357 | SetPageError(page); |
| 358 | } |
| 359 | |
| 360 | first = page_buffers(page); |
| 361 | local_irq_save(flags); |
| 362 | bit_spin_lock(BH_Uptodate_Lock, &first->b_state); |
| 363 | |
| 364 | clear_buffer_async_write(bh); |
| 365 | unlock_buffer(bh); |
| 366 | tmp = bh->b_this_page; |
| 367 | while (tmp != bh) { |
| 368 | if (buffer_async_write(tmp)) { |
| 369 | BUG_ON(!buffer_locked(tmp)); |
| 370 | goto still_busy; |
| 371 | } |
| 372 | tmp = tmp->b_this_page; |
| 373 | } |
| 374 | bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); |
| 375 | local_irq_restore(flags); |
| 376 | end_page_writeback(page); |
| 377 | return; |
| 378 | |
| 379 | still_busy: |
| 380 | bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); |
| 381 | local_irq_restore(flags); |
| 382 | return; |
| 383 | } |
| 384 | EXPORT_SYMBOL(end_buffer_async_write); |
| 385 | |
| 386 | /* |
| 387 | * If a page's buffers are under async readin (end_buffer_async_read |
| 388 | * completion) then there is a possibility that another thread of |
| 389 | * control could lock one of the buffers after it has completed |
| 390 | * but while some of the other buffers have not completed. This |
| 391 | * locked buffer would confuse end_buffer_async_read() into not unlocking |
| 392 | * the page. So the absence of BH_Async_Read tells end_buffer_async_read() |
| 393 | * that this buffer is not under async I/O. |
| 394 | * |
| 395 | * The page comes unlocked when it has no locked buffer_async buffers |
| 396 | * left. |
| 397 | * |
| 398 | * PageLocked prevents anyone starting new async I/O reads any of |
| 399 | * the buffers. |
| 400 | * |
| 401 | * PageWriteback is used to prevent simultaneous writeout of the same |
| 402 | * page. |
| 403 | * |
| 404 | * PageLocked prevents anyone from starting writeback of a page which is |
| 405 | * under read I/O (PageWriteback is only ever set against a locked page). |
| 406 | */ |
| 407 | static void mark_buffer_async_read(struct buffer_head *bh) |
| 408 | { |
| 409 | bh->b_end_io = end_buffer_async_read; |
| 410 | set_buffer_async_read(bh); |
| 411 | } |
| 412 | |
| 413 | static void mark_buffer_async_write_endio(struct buffer_head *bh, |
| 414 | bh_end_io_t *handler) |
| 415 | { |
| 416 | bh->b_end_io = handler; |
| 417 | set_buffer_async_write(bh); |
| 418 | } |
| 419 | |
| 420 | void mark_buffer_async_write(struct buffer_head *bh) |
| 421 | { |
| 422 | mark_buffer_async_write_endio(bh, end_buffer_async_write); |
| 423 | } |
| 424 | EXPORT_SYMBOL(mark_buffer_async_write); |
| 425 | |
| 426 | |
| 427 | /* |
| 428 | * fs/buffer.c contains helper functions for buffer-backed address space's |
| 429 | * fsync functions. A common requirement for buffer-based filesystems is |
| 430 | * that certain data from the backing blockdev needs to be written out for |
| 431 | * a successful fsync(). For example, ext2 indirect blocks need to be |
| 432 | * written back and waited upon before fsync() returns. |
| 433 | * |
| 434 | * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(), |
| 435 | * inode_has_buffers() and invalidate_inode_buffers() are provided for the |
| 436 | * management of a list of dependent buffers at ->i_mapping->private_list. |
| 437 | * |
| 438 | * Locking is a little subtle: try_to_free_buffers() will remove buffers |
| 439 | * from their controlling inode's queue when they are being freed. But |
| 440 | * try_to_free_buffers() will be operating against the *blockdev* mapping |
| 441 | * at the time, not against the S_ISREG file which depends on those buffers. |
| 442 | * So the locking for private_list is via the private_lock in the address_space |
| 443 | * which backs the buffers. Which is different from the address_space |
| 444 | * against which the buffers are listed. So for a particular address_space, |
| 445 | * mapping->private_lock does *not* protect mapping->private_list! In fact, |
| 446 | * mapping->private_list will always be protected by the backing blockdev's |
| 447 | * ->private_lock. |
| 448 | * |
| 449 | * Which introduces a requirement: all buffers on an address_space's |
| 450 | * ->private_list must be from the same address_space: the blockdev's. |
| 451 | * |
| 452 | * address_spaces which do not place buffers at ->private_list via these |
| 453 | * utility functions are free to use private_lock and private_list for |
| 454 | * whatever they want. The only requirement is that list_empty(private_list) |
| 455 | * be true at clear_inode() time. |
| 456 | * |
| 457 | * FIXME: clear_inode should not call invalidate_inode_buffers(). The |
| 458 | * filesystems should do that. invalidate_inode_buffers() should just go |
| 459 | * BUG_ON(!list_empty). |
| 460 | * |
| 461 | * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should |
| 462 | * take an address_space, not an inode. And it should be called |
| 463 | * mark_buffer_dirty_fsync() to clearly define why those buffers are being |
| 464 | * queued up. |
| 465 | * |
| 466 | * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the |
| 467 | * list if it is already on a list. Because if the buffer is on a list, |
| 468 | * it *must* already be on the right one. If not, the filesystem is being |
| 469 | * silly. This will save a ton of locking. But first we have to ensure |
| 470 | * that buffers are taken *off* the old inode's list when they are freed |
| 471 | * (presumably in truncate). That requires careful auditing of all |
| 472 | * filesystems (do it inside bforget()). It could also be done by bringing |
| 473 | * b_inode back. |
| 474 | */ |
| 475 | |
| 476 | /* |
| 477 | * The buffer's backing address_space's private_lock must be held |
| 478 | */ |
| 479 | static void __remove_assoc_queue(struct buffer_head *bh) |
| 480 | { |
| 481 | list_del_init(&bh->b_assoc_buffers); |
| 482 | WARN_ON(!bh->b_assoc_map); |
| 483 | if (buffer_write_io_error(bh)) |
| 484 | set_bit(AS_EIO, &bh->b_assoc_map->flags); |
| 485 | bh->b_assoc_map = NULL; |
| 486 | } |
| 487 | |
| 488 | int inode_has_buffers(struct inode *inode) |
| 489 | { |
| 490 | return !list_empty(&inode->i_data.private_list); |
| 491 | } |
| 492 | |
| 493 | /* |
| 494 | * osync is designed to support O_SYNC io. It waits synchronously for |
| 495 | * all already-submitted IO to complete, but does not queue any new |
| 496 | * writes to the disk. |
| 497 | * |
| 498 | * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as |
| 499 | * you dirty the buffers, and then use osync_inode_buffers to wait for |
| 500 | * completion. Any other dirty buffers which are not yet queued for |
| 501 | * write will not be flushed to disk by the osync. |
| 502 | */ |
| 503 | static int osync_buffers_list(spinlock_t *lock, struct list_head *list) |
| 504 | { |
| 505 | struct buffer_head *bh; |
| 506 | struct list_head *p; |
| 507 | int err = 0; |
| 508 | |
| 509 | spin_lock(lock); |
| 510 | repeat: |
| 511 | list_for_each_prev(p, list) { |
| 512 | bh = BH_ENTRY(p); |
| 513 | if (buffer_locked(bh)) { |
| 514 | get_bh(bh); |
| 515 | spin_unlock(lock); |
| 516 | wait_on_buffer(bh); |
| 517 | if (!buffer_uptodate(bh)) |
| 518 | err = -EIO; |
| 519 | brelse(bh); |
| 520 | spin_lock(lock); |
| 521 | goto repeat; |
| 522 | } |
| 523 | } |
| 524 | spin_unlock(lock); |
| 525 | return err; |
| 526 | } |
| 527 | |
| 528 | static void do_thaw_one(struct super_block *sb, void *unused) |
| 529 | { |
| 530 | char b[BDEVNAME_SIZE]; |
| 531 | while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb)) |
| 532 | printk(KERN_WARNING "Emergency Thaw on %s\n", |
| 533 | bdevname(sb->s_bdev, b)); |
| 534 | } |
| 535 | |
| 536 | static void do_thaw_all(struct work_struct *work) |
| 537 | { |
| 538 | iterate_supers(do_thaw_one, NULL); |
| 539 | kfree(work); |
| 540 | printk(KERN_WARNING "Emergency Thaw complete\n"); |
| 541 | } |
| 542 | |
| 543 | /** |
| 544 | * emergency_thaw_all -- forcibly thaw every frozen filesystem |
| 545 | * |
| 546 | * Used for emergency unfreeze of all filesystems via SysRq |
| 547 | */ |
| 548 | void emergency_thaw_all(void) |
| 549 | { |
| 550 | struct work_struct *work; |
| 551 | |
| 552 | work = kmalloc(sizeof(*work), GFP_ATOMIC); |
| 553 | if (work) { |
| 554 | INIT_WORK(work, do_thaw_all); |
| 555 | schedule_work(work); |
| 556 | } |
| 557 | } |
| 558 | |
| 559 | /** |
| 560 | * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers |
| 561 | * @mapping: the mapping which wants those buffers written |
| 562 | * |
| 563 | * Starts I/O against the buffers at mapping->private_list, and waits upon |
| 564 | * that I/O. |
| 565 | * |
| 566 | * Basically, this is a convenience function for fsync(). |
| 567 | * @mapping is a file or directory which needs those buffers to be written for |
| 568 | * a successful fsync(). |
| 569 | */ |
| 570 | int sync_mapping_buffers(struct address_space *mapping) |
| 571 | { |
| 572 | struct address_space *buffer_mapping = mapping->private_data; |
| 573 | |
| 574 | if (buffer_mapping == NULL || list_empty(&mapping->private_list)) |
| 575 | return 0; |
| 576 | |
| 577 | return fsync_buffers_list(&buffer_mapping->private_lock, |
| 578 | &mapping->private_list); |
| 579 | } |
| 580 | EXPORT_SYMBOL(sync_mapping_buffers); |
| 581 | |
| 582 | /* |
| 583 | * Called when we've recently written block `bblock', and it is known that |
| 584 | * `bblock' was for a buffer_boundary() buffer. This means that the block at |
| 585 | * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's |
| 586 | * dirty, schedule it for IO. So that indirects merge nicely with their data. |
| 587 | */ |
| 588 | void write_boundary_block(struct block_device *bdev, |
| 589 | sector_t bblock, unsigned blocksize) |
| 590 | { |
| 591 | struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize); |
| 592 | if (bh) { |
| 593 | if (buffer_dirty(bh)) |
| 594 | ll_rw_block(WRITE, 1, &bh); |
| 595 | put_bh(bh); |
| 596 | } |
| 597 | } |
| 598 | |
| 599 | void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode) |
| 600 | { |
| 601 | struct address_space *mapping = inode->i_mapping; |
| 602 | struct address_space *buffer_mapping = bh->b_page->mapping; |
| 603 | |
| 604 | mark_buffer_dirty(bh); |
| 605 | if (!mapping->private_data) { |
| 606 | mapping->private_data = buffer_mapping; |
| 607 | } else { |
| 608 | BUG_ON(mapping->private_data != buffer_mapping); |
| 609 | } |
| 610 | if (!bh->b_assoc_map) { |
| 611 | spin_lock(&buffer_mapping->private_lock); |
| 612 | list_move_tail(&bh->b_assoc_buffers, |
| 613 | &mapping->private_list); |
| 614 | bh->b_assoc_map = mapping; |
| 615 | spin_unlock(&buffer_mapping->private_lock); |
| 616 | } |
| 617 | } |
| 618 | EXPORT_SYMBOL(mark_buffer_dirty_inode); |
| 619 | |
| 620 | /* |
| 621 | * Mark the page dirty, and set it dirty in the radix tree, and mark the inode |
| 622 | * dirty. |
| 623 | * |
| 624 | * If warn is true, then emit a warning if the page is not uptodate and has |
| 625 | * not been truncated. |
| 626 | */ |
| 627 | static void __set_page_dirty(struct page *page, |
| 628 | struct address_space *mapping, int warn) |
| 629 | { |
| 630 | unsigned long flags; |
| 631 | |
| 632 | spin_lock_irqsave(&mapping->tree_lock, flags); |
| 633 | if (page->mapping) { /* Race with truncate? */ |
| 634 | WARN_ON_ONCE(warn && !PageUptodate(page)); |
| 635 | account_page_dirtied(page, mapping); |
| 636 | radix_tree_tag_set(&mapping->page_tree, |
| 637 | page_index(page), PAGECACHE_TAG_DIRTY); |
| 638 | } |
| 639 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
| 640 | __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); |
| 641 | } |
| 642 | |
| 643 | /* |
| 644 | * Add a page to the dirty page list. |
| 645 | * |
| 646 | * It is a sad fact of life that this function is called from several places |
| 647 | * deeply under spinlocking. It may not sleep. |
| 648 | * |
| 649 | * If the page has buffers, the uptodate buffers are set dirty, to preserve |
| 650 | * dirty-state coherency between the page and the buffers. It the page does |
| 651 | * not have buffers then when they are later attached they will all be set |
| 652 | * dirty. |
| 653 | * |
| 654 | * The buffers are dirtied before the page is dirtied. There's a small race |
| 655 | * window in which a writepage caller may see the page cleanness but not the |
| 656 | * buffer dirtiness. That's fine. If this code were to set the page dirty |
| 657 | * before the buffers, a concurrent writepage caller could clear the page dirty |
| 658 | * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean |
| 659 | * page on the dirty page list. |
| 660 | * |
| 661 | * We use private_lock to lock against try_to_free_buffers while using the |
| 662 | * page's buffer list. Also use this to protect against clean buffers being |
| 663 | * added to the page after it was set dirty. |
| 664 | * |
| 665 | * FIXME: may need to call ->reservepage here as well. That's rather up to the |
| 666 | * address_space though. |
| 667 | */ |
| 668 | int __set_page_dirty_buffers(struct page *page) |
| 669 | { |
| 670 | int newly_dirty; |
| 671 | struct address_space *mapping = page_mapping(page); |
| 672 | |
| 673 | if (unlikely(!mapping)) |
| 674 | return !TestSetPageDirty(page); |
| 675 | |
| 676 | spin_lock(&mapping->private_lock); |
| 677 | if (page_has_buffers(page)) { |
| 678 | struct buffer_head *head = page_buffers(page); |
| 679 | struct buffer_head *bh = head; |
| 680 | |
| 681 | do { |
| 682 | set_buffer_dirty(bh); |
| 683 | bh = bh->b_this_page; |
| 684 | } while (bh != head); |
| 685 | } |
| 686 | newly_dirty = !TestSetPageDirty(page); |
| 687 | spin_unlock(&mapping->private_lock); |
| 688 | |
| 689 | if (newly_dirty) |
| 690 | __set_page_dirty(page, mapping, 1); |
| 691 | return newly_dirty; |
| 692 | } |
| 693 | EXPORT_SYMBOL(__set_page_dirty_buffers); |
| 694 | |
| 695 | /* |
| 696 | * Write out and wait upon a list of buffers. |
| 697 | * |
| 698 | * We have conflicting pressures: we want to make sure that all |
| 699 | * initially dirty buffers get waited on, but that any subsequently |
| 700 | * dirtied buffers don't. After all, we don't want fsync to last |
| 701 | * forever if somebody is actively writing to the file. |
| 702 | * |
| 703 | * Do this in two main stages: first we copy dirty buffers to a |
| 704 | * temporary inode list, queueing the writes as we go. Then we clean |
| 705 | * up, waiting for those writes to complete. |
| 706 | * |
| 707 | * During this second stage, any subsequent updates to the file may end |
| 708 | * up refiling the buffer on the original inode's dirty list again, so |
| 709 | * there is a chance we will end up with a buffer queued for write but |
| 710 | * not yet completed on that list. So, as a final cleanup we go through |
| 711 | * the osync code to catch these locked, dirty buffers without requeuing |
| 712 | * any newly dirty buffers for write. |
| 713 | */ |
| 714 | static int fsync_buffers_list(spinlock_t *lock, struct list_head *list) |
| 715 | { |
| 716 | struct buffer_head *bh; |
| 717 | struct list_head tmp; |
| 718 | struct address_space *mapping; |
| 719 | int err = 0, err2; |
| 720 | struct blk_plug plug; |
| 721 | |
| 722 | INIT_LIST_HEAD(&tmp); |
| 723 | blk_start_plug(&plug); |
| 724 | |
| 725 | spin_lock(lock); |
| 726 | while (!list_empty(list)) { |
| 727 | bh = BH_ENTRY(list->next); |
| 728 | mapping = bh->b_assoc_map; |
| 729 | __remove_assoc_queue(bh); |
| 730 | /* Avoid race with mark_buffer_dirty_inode() which does |
| 731 | * a lockless check and we rely on seeing the dirty bit */ |
| 732 | smp_mb(); |
| 733 | if (buffer_dirty(bh) || buffer_locked(bh)) { |
| 734 | list_add(&bh->b_assoc_buffers, &tmp); |
| 735 | bh->b_assoc_map = mapping; |
| 736 | if (buffer_dirty(bh)) { |
| 737 | get_bh(bh); |
| 738 | spin_unlock(lock); |
| 739 | /* |
| 740 | * Ensure any pending I/O completes so that |
| 741 | * write_dirty_buffer() actually writes the |
| 742 | * current contents - it is a noop if I/O is |
| 743 | * still in flight on potentially older |
| 744 | * contents. |
| 745 | */ |
| 746 | write_dirty_buffer(bh, WRITE_SYNC); |
| 747 | |
| 748 | /* |
| 749 | * Kick off IO for the previous mapping. Note |
| 750 | * that we will not run the very last mapping, |
| 751 | * wait_on_buffer() will do that for us |
| 752 | * through sync_buffer(). |
| 753 | */ |
| 754 | brelse(bh); |
| 755 | spin_lock(lock); |
| 756 | } |
| 757 | } |
| 758 | } |
| 759 | |
| 760 | spin_unlock(lock); |
| 761 | blk_finish_plug(&plug); |
| 762 | spin_lock(lock); |
| 763 | |
| 764 | while (!list_empty(&tmp)) { |
| 765 | bh = BH_ENTRY(tmp.prev); |
| 766 | get_bh(bh); |
| 767 | mapping = bh->b_assoc_map; |
| 768 | __remove_assoc_queue(bh); |
| 769 | /* Avoid race with mark_buffer_dirty_inode() which does |
| 770 | * a lockless check and we rely on seeing the dirty bit */ |
| 771 | smp_mb(); |
| 772 | if (buffer_dirty(bh)) { |
| 773 | list_add(&bh->b_assoc_buffers, |
| 774 | &mapping->private_list); |
| 775 | bh->b_assoc_map = mapping; |
| 776 | } |
| 777 | spin_unlock(lock); |
| 778 | wait_on_buffer(bh); |
| 779 | if (!buffer_uptodate(bh)) |
| 780 | err = -EIO; |
| 781 | brelse(bh); |
| 782 | spin_lock(lock); |
| 783 | } |
| 784 | |
| 785 | spin_unlock(lock); |
| 786 | err2 = osync_buffers_list(lock, list); |
| 787 | if (err) |
| 788 | return err; |
| 789 | else |
| 790 | return err2; |
| 791 | } |
| 792 | |
| 793 | /* |
| 794 | * Invalidate any and all dirty buffers on a given inode. We are |
| 795 | * probably unmounting the fs, but that doesn't mean we have already |
| 796 | * done a sync(). Just drop the buffers from the inode list. |
| 797 | * |
| 798 | * NOTE: we take the inode's blockdev's mapping's private_lock. Which |
| 799 | * assumes that all the buffers are against the blockdev. Not true |
| 800 | * for reiserfs. |
| 801 | */ |
| 802 | void invalidate_inode_buffers(struct inode *inode) |
| 803 | { |
| 804 | if (inode_has_buffers(inode)) { |
| 805 | struct address_space *mapping = &inode->i_data; |
| 806 | struct list_head *list = &mapping->private_list; |
| 807 | struct address_space *buffer_mapping = mapping->private_data; |
| 808 | |
| 809 | spin_lock(&buffer_mapping->private_lock); |
| 810 | while (!list_empty(list)) |
| 811 | __remove_assoc_queue(BH_ENTRY(list->next)); |
| 812 | spin_unlock(&buffer_mapping->private_lock); |
| 813 | } |
| 814 | } |
| 815 | EXPORT_SYMBOL(invalidate_inode_buffers); |
| 816 | |
| 817 | /* |
| 818 | * Remove any clean buffers from the inode's buffer list. This is called |
| 819 | * when we're trying to free the inode itself. Those buffers can pin it. |
| 820 | * |
| 821 | * Returns true if all buffers were removed. |
| 822 | */ |
| 823 | int remove_inode_buffers(struct inode *inode) |
| 824 | { |
| 825 | int ret = 1; |
| 826 | |
| 827 | if (inode_has_buffers(inode)) { |
| 828 | struct address_space *mapping = &inode->i_data; |
| 829 | struct list_head *list = &mapping->private_list; |
| 830 | struct address_space *buffer_mapping = mapping->private_data; |
| 831 | |
| 832 | spin_lock(&buffer_mapping->private_lock); |
| 833 | while (!list_empty(list)) { |
| 834 | struct buffer_head *bh = BH_ENTRY(list->next); |
| 835 | if (buffer_dirty(bh)) { |
| 836 | ret = 0; |
| 837 | break; |
| 838 | } |
| 839 | __remove_assoc_queue(bh); |
| 840 | } |
| 841 | spin_unlock(&buffer_mapping->private_lock); |
| 842 | } |
| 843 | return ret; |
| 844 | } |
| 845 | |
| 846 | /* |
| 847 | * Create the appropriate buffers when given a page for data area and |
| 848 | * the size of each buffer.. Use the bh->b_this_page linked list to |
| 849 | * follow the buffers created. Return NULL if unable to create more |
| 850 | * buffers. |
| 851 | * |
| 852 | * The retry flag is used to differentiate async IO (paging, swapping) |
| 853 | * which may not fail from ordinary buffer allocations. |
| 854 | */ |
| 855 | struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, |
| 856 | int retry) |
| 857 | { |
| 858 | struct buffer_head *bh, *head; |
| 859 | long offset; |
| 860 | |
| 861 | try_again: |
| 862 | head = NULL; |
| 863 | offset = PAGE_SIZE; |
| 864 | while ((offset -= size) >= 0) { |
| 865 | bh = alloc_buffer_head(GFP_NOFS); |
| 866 | if (!bh) |
| 867 | goto no_grow; |
| 868 | |
| 869 | bh->b_this_page = head; |
| 870 | bh->b_blocknr = -1; |
| 871 | head = bh; |
| 872 | |
| 873 | bh->b_size = size; |
| 874 | |
| 875 | /* Link the buffer to its page */ |
| 876 | set_bh_page(bh, page, offset); |
| 877 | } |
| 878 | return head; |
| 879 | /* |
| 880 | * In case anything failed, we just free everything we got. |
| 881 | */ |
| 882 | no_grow: |
| 883 | if (head) { |
| 884 | do { |
| 885 | bh = head; |
| 886 | head = head->b_this_page; |
| 887 | free_buffer_head(bh); |
| 888 | } while (head); |
| 889 | } |
| 890 | |
| 891 | /* |
| 892 | * Return failure for non-async IO requests. Async IO requests |
| 893 | * are not allowed to fail, so we have to wait until buffer heads |
| 894 | * become available. But we don't want tasks sleeping with |
| 895 | * partially complete buffers, so all were released above. |
| 896 | */ |
| 897 | if (!retry) |
| 898 | return NULL; |
| 899 | |
| 900 | /* We're _really_ low on memory. Now we just |
| 901 | * wait for old buffer heads to become free due to |
| 902 | * finishing IO. Since this is an async request and |
| 903 | * the reserve list is empty, we're sure there are |
| 904 | * async buffer heads in use. |
| 905 | */ |
| 906 | free_more_memory(); |
| 907 | goto try_again; |
| 908 | } |
| 909 | EXPORT_SYMBOL_GPL(alloc_page_buffers); |
| 910 | |
| 911 | static inline void |
| 912 | link_dev_buffers(struct page *page, struct buffer_head *head) |
| 913 | { |
| 914 | struct buffer_head *bh, *tail; |
| 915 | |
| 916 | bh = head; |
| 917 | do { |
| 918 | tail = bh; |
| 919 | bh = bh->b_this_page; |
| 920 | } while (bh); |
| 921 | tail->b_this_page = head; |
| 922 | attach_page_buffers(page, head); |
| 923 | } |
| 924 | |
| 925 | static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size) |
| 926 | { |
| 927 | sector_t retval = ~((sector_t)0); |
| 928 | loff_t sz = i_size_read(bdev->bd_inode); |
| 929 | |
| 930 | if (sz) { |
| 931 | unsigned int sizebits = blksize_bits(size); |
| 932 | retval = (sz >> sizebits); |
| 933 | } |
| 934 | return retval; |
| 935 | } |
| 936 | |
| 937 | /* |
| 938 | * Initialise the state of a blockdev page's buffers. |
| 939 | */ |
| 940 | static sector_t |
| 941 | init_page_buffers(struct page *page, struct block_device *bdev, |
| 942 | sector_t block, int size) |
| 943 | { |
| 944 | struct buffer_head *head = page_buffers(page); |
| 945 | struct buffer_head *bh = head; |
| 946 | int uptodate = PageUptodate(page); |
| 947 | sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode), size); |
| 948 | |
| 949 | do { |
| 950 | if (!buffer_mapped(bh)) { |
| 951 | init_buffer(bh, NULL, NULL); |
| 952 | bh->b_bdev = bdev; |
| 953 | bh->b_blocknr = block; |
| 954 | if (uptodate) |
| 955 | set_buffer_uptodate(bh); |
| 956 | if (block < end_block) |
| 957 | set_buffer_mapped(bh); |
| 958 | } |
| 959 | block++; |
| 960 | bh = bh->b_this_page; |
| 961 | } while (bh != head); |
| 962 | |
| 963 | /* |
| 964 | * Caller needs to validate requested block against end of device. |
| 965 | */ |
| 966 | return end_block; |
| 967 | } |
| 968 | |
| 969 | /* |
| 970 | * Create the page-cache page that contains the requested block. |
| 971 | * |
| 972 | * This is used purely for blockdev mappings. |
| 973 | */ |
| 974 | static int |
| 975 | grow_dev_page(struct block_device *bdev, sector_t block, |
| 976 | pgoff_t index, int size, int sizebits, gfp_t gfp) |
| 977 | { |
| 978 | struct inode *inode = bdev->bd_inode; |
| 979 | struct page *page; |
| 980 | struct buffer_head *bh; |
| 981 | sector_t end_block; |
| 982 | int ret = 0; /* Will call free_more_memory() */ |
| 983 | gfp_t gfp_mask; |
| 984 | |
| 985 | gfp_mask = (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS) | gfp; |
| 986 | |
| 987 | /* |
| 988 | * XXX: __getblk_slow() can not really deal with failure and |
| 989 | * will endlessly loop on improvised global reclaim. Prefer |
| 990 | * looping in the allocator rather than here, at least that |
| 991 | * code knows what it's doing. |
| 992 | */ |
| 993 | gfp_mask |= __GFP_NOFAIL; |
| 994 | |
| 995 | page = find_or_create_page(inode->i_mapping, index, gfp_mask); |
| 996 | if (!page) |
| 997 | return ret; |
| 998 | |
| 999 | BUG_ON(!PageLocked(page)); |
| 1000 | |
| 1001 | if (page_has_buffers(page)) { |
| 1002 | bh = page_buffers(page); |
| 1003 | if (bh->b_size == size) { |
| 1004 | end_block = init_page_buffers(page, bdev, |
| 1005 | (sector_t)index << sizebits, |
| 1006 | size); |
| 1007 | goto done; |
| 1008 | } |
| 1009 | if (!try_to_free_buffers(page)) |
| 1010 | goto failed; |
| 1011 | } |
| 1012 | |
| 1013 | /* |
| 1014 | * Allocate some buffers for this page |
| 1015 | */ |
| 1016 | bh = alloc_page_buffers(page, size, 0); |
| 1017 | if (!bh) |
| 1018 | goto failed; |
| 1019 | |
| 1020 | /* |
| 1021 | * Link the page to the buffers and initialise them. Take the |
| 1022 | * lock to be atomic wrt __find_get_block(), which does not |
| 1023 | * run under the page lock. |
| 1024 | */ |
| 1025 | spin_lock(&inode->i_mapping->private_lock); |
| 1026 | link_dev_buffers(page, bh); |
| 1027 | end_block = init_page_buffers(page, bdev, (sector_t)index << sizebits, |
| 1028 | size); |
| 1029 | spin_unlock(&inode->i_mapping->private_lock); |
| 1030 | done: |
| 1031 | ret = (block < end_block) ? 1 : -ENXIO; |
| 1032 | failed: |
| 1033 | unlock_page(page); |
| 1034 | page_cache_release(page); |
| 1035 | return ret; |
| 1036 | } |
| 1037 | |
| 1038 | /* |
| 1039 | * Create buffers for the specified block device block's page. If |
| 1040 | * that page was dirty, the buffers are set dirty also. |
| 1041 | */ |
| 1042 | static int |
| 1043 | grow_buffers(struct block_device *bdev, sector_t block, int size, gfp_t gfp) |
| 1044 | { |
| 1045 | pgoff_t index; |
| 1046 | int sizebits; |
| 1047 | |
| 1048 | sizebits = -1; |
| 1049 | do { |
| 1050 | sizebits++; |
| 1051 | } while ((size << sizebits) < PAGE_SIZE); |
| 1052 | |
| 1053 | index = block >> sizebits; |
| 1054 | |
| 1055 | /* |
| 1056 | * Check for a block which wants to lie outside our maximum possible |
| 1057 | * pagecache index. (this comparison is done using sector_t types). |
| 1058 | */ |
| 1059 | if (unlikely(index != block >> sizebits)) { |
| 1060 | char b[BDEVNAME_SIZE]; |
| 1061 | |
| 1062 | printk(KERN_ERR "%s: requested out-of-range block %llu for " |
| 1063 | "device %s\n", |
| 1064 | __func__, (unsigned long long)block, |
| 1065 | bdevname(bdev, b)); |
| 1066 | return -EIO; |
| 1067 | } |
| 1068 | |
| 1069 | /* Create a page with the proper size buffers.. */ |
| 1070 | return grow_dev_page(bdev, block, index, size, sizebits, gfp); |
| 1071 | } |
| 1072 | |
| 1073 | struct buffer_head * |
| 1074 | __getblk_slow(struct block_device *bdev, sector_t block, |
| 1075 | unsigned size, gfp_t gfp) |
| 1076 | { |
| 1077 | /* Size must be multiple of hard sectorsize */ |
| 1078 | if (unlikely(size & (bdev_logical_block_size(bdev)-1) || |
| 1079 | (size < 512 || size > PAGE_SIZE))) { |
| 1080 | printk(KERN_ERR "getblk(): invalid block size %d requested\n", |
| 1081 | size); |
| 1082 | printk(KERN_ERR "logical block size: %d\n", |
| 1083 | bdev_logical_block_size(bdev)); |
| 1084 | |
| 1085 | dump_stack(); |
| 1086 | return NULL; |
| 1087 | } |
| 1088 | |
| 1089 | for (;;) { |
| 1090 | struct buffer_head *bh; |
| 1091 | int ret; |
| 1092 | |
| 1093 | bh = __find_get_block(bdev, block, size); |
| 1094 | if (bh) |
| 1095 | return bh; |
| 1096 | |
| 1097 | ret = grow_buffers(bdev, block, size, gfp); |
| 1098 | if (ret < 0) |
| 1099 | return NULL; |
| 1100 | if (ret == 0) |
| 1101 | free_more_memory(); |
| 1102 | } |
| 1103 | } |
| 1104 | EXPORT_SYMBOL(__getblk_slow); |
| 1105 | |
| 1106 | /* |
| 1107 | * The relationship between dirty buffers and dirty pages: |
| 1108 | * |
| 1109 | * Whenever a page has any dirty buffers, the page's dirty bit is set, and |
| 1110 | * the page is tagged dirty in its radix tree. |
| 1111 | * |
| 1112 | * At all times, the dirtiness of the buffers represents the dirtiness of |
| 1113 | * subsections of the page. If the page has buffers, the page dirty bit is |
| 1114 | * merely a hint about the true dirty state. |
| 1115 | * |
| 1116 | * When a page is set dirty in its entirety, all its buffers are marked dirty |
| 1117 | * (if the page has buffers). |
| 1118 | * |
| 1119 | * When a buffer is marked dirty, its page is dirtied, but the page's other |
| 1120 | * buffers are not. |
| 1121 | * |
| 1122 | * Also. When blockdev buffers are explicitly read with bread(), they |
| 1123 | * individually become uptodate. But their backing page remains not |
| 1124 | * uptodate - even if all of its buffers are uptodate. A subsequent |
| 1125 | * block_read_full_page() against that page will discover all the uptodate |
| 1126 | * buffers, will set the page uptodate and will perform no I/O. |
| 1127 | */ |
| 1128 | |
| 1129 | /** |
| 1130 | * mark_buffer_dirty - mark a buffer_head as needing writeout |
| 1131 | * @bh: the buffer_head to mark dirty |
| 1132 | * |
| 1133 | * mark_buffer_dirty() will set the dirty bit against the buffer, then set its |
| 1134 | * backing page dirty, then tag the page as dirty in its address_space's radix |
| 1135 | * tree and then attach the address_space's inode to its superblock's dirty |
| 1136 | * inode list. |
| 1137 | * |
| 1138 | * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock, |
| 1139 | * mapping->tree_lock and mapping->host->i_lock. |
| 1140 | */ |
| 1141 | void mark_buffer_dirty(struct buffer_head *bh) |
| 1142 | { |
| 1143 | WARN_ON_ONCE(!buffer_uptodate(bh)); |
| 1144 | |
| 1145 | trace_block_dirty_buffer(bh); |
| 1146 | |
| 1147 | /* |
| 1148 | * Very *carefully* optimize the it-is-already-dirty case. |
| 1149 | * |
| 1150 | * Don't let the final "is it dirty" escape to before we |
| 1151 | * perhaps modified the buffer. |
| 1152 | */ |
| 1153 | if (buffer_dirty(bh)) { |
| 1154 | smp_mb(); |
| 1155 | if (buffer_dirty(bh)) |
| 1156 | return; |
| 1157 | } |
| 1158 | |
| 1159 | if (!test_set_buffer_dirty(bh)) { |
| 1160 | struct page *page = bh->b_page; |
| 1161 | if (!TestSetPageDirty(page)) { |
| 1162 | struct address_space *mapping = page_mapping(page); |
| 1163 | if (mapping) |
| 1164 | __set_page_dirty(page, mapping, 0); |
| 1165 | } |
| 1166 | } |
| 1167 | } |
| 1168 | EXPORT_SYMBOL(mark_buffer_dirty); |
| 1169 | |
| 1170 | /* |
| 1171 | * Decrement a buffer_head's reference count. If all buffers against a page |
| 1172 | * have zero reference count, are clean and unlocked, and if the page is clean |
| 1173 | * and unlocked then try_to_free_buffers() may strip the buffers from the page |
| 1174 | * in preparation for freeing it (sometimes, rarely, buffers are removed from |
| 1175 | * a page but it ends up not being freed, and buffers may later be reattached). |
| 1176 | */ |
| 1177 | void __brelse(struct buffer_head * buf) |
| 1178 | { |
| 1179 | if (atomic_read(&buf->b_count)) { |
| 1180 | put_bh(buf); |
| 1181 | return; |
| 1182 | } |
| 1183 | WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n"); |
| 1184 | } |
| 1185 | EXPORT_SYMBOL(__brelse); |
| 1186 | |
| 1187 | /* |
| 1188 | * bforget() is like brelse(), except it discards any |
| 1189 | * potentially dirty data. |
| 1190 | */ |
| 1191 | void __bforget(struct buffer_head *bh) |
| 1192 | { |
| 1193 | clear_buffer_dirty(bh); |
| 1194 | if (bh->b_assoc_map) { |
| 1195 | struct address_space *buffer_mapping = bh->b_page->mapping; |
| 1196 | |
| 1197 | spin_lock(&buffer_mapping->private_lock); |
| 1198 | list_del_init(&bh->b_assoc_buffers); |
| 1199 | bh->b_assoc_map = NULL; |
| 1200 | spin_unlock(&buffer_mapping->private_lock); |
| 1201 | } |
| 1202 | __brelse(bh); |
| 1203 | } |
| 1204 | EXPORT_SYMBOL(__bforget); |
| 1205 | |
| 1206 | static struct buffer_head *__bread_slow(struct buffer_head *bh) |
| 1207 | { |
| 1208 | lock_buffer(bh); |
| 1209 | if (buffer_uptodate(bh)) { |
| 1210 | unlock_buffer(bh); |
| 1211 | return bh; |
| 1212 | } else { |
| 1213 | get_bh(bh); |
| 1214 | bh->b_end_io = end_buffer_read_sync; |
| 1215 | submit_bh(READ, bh); |
| 1216 | wait_on_buffer(bh); |
| 1217 | if (buffer_uptodate(bh)) |
| 1218 | return bh; |
| 1219 | } |
| 1220 | brelse(bh); |
| 1221 | return NULL; |
| 1222 | } |
| 1223 | |
| 1224 | /* |
| 1225 | * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block(). |
| 1226 | * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their |
| 1227 | * refcount elevated by one when they're in an LRU. A buffer can only appear |
| 1228 | * once in a particular CPU's LRU. A single buffer can be present in multiple |
| 1229 | * CPU's LRUs at the same time. |
| 1230 | * |
| 1231 | * This is a transparent caching front-end to sb_bread(), sb_getblk() and |
| 1232 | * sb_find_get_block(). |
| 1233 | * |
| 1234 | * The LRUs themselves only need locking against invalidate_bh_lrus. We use |
| 1235 | * a local interrupt disable for that. |
| 1236 | */ |
| 1237 | |
| 1238 | #define BH_LRU_SIZE 16 |
| 1239 | |
| 1240 | struct bh_lru { |
| 1241 | struct buffer_head *bhs[BH_LRU_SIZE]; |
| 1242 | }; |
| 1243 | |
| 1244 | static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }}; |
| 1245 | |
| 1246 | #ifdef CONFIG_SMP |
| 1247 | #define bh_lru_lock() local_irq_disable() |
| 1248 | #define bh_lru_unlock() local_irq_enable() |
| 1249 | #else |
| 1250 | #define bh_lru_lock() preempt_disable() |
| 1251 | #define bh_lru_unlock() preempt_enable() |
| 1252 | #endif |
| 1253 | |
| 1254 | static inline void check_irqs_on(void) |
| 1255 | { |
| 1256 | #ifdef irqs_disabled |
| 1257 | BUG_ON(irqs_disabled()); |
| 1258 | #endif |
| 1259 | } |
| 1260 | |
| 1261 | /* |
| 1262 | * The LRU management algorithm is dopey-but-simple. Sorry. |
| 1263 | */ |
| 1264 | static void bh_lru_install(struct buffer_head *bh) |
| 1265 | { |
| 1266 | struct buffer_head *evictee = NULL; |
| 1267 | |
| 1268 | check_irqs_on(); |
| 1269 | bh_lru_lock(); |
| 1270 | if (__this_cpu_read(bh_lrus.bhs[0]) != bh) { |
| 1271 | struct buffer_head *bhs[BH_LRU_SIZE]; |
| 1272 | int in; |
| 1273 | int out = 0; |
| 1274 | |
| 1275 | get_bh(bh); |
| 1276 | bhs[out++] = bh; |
| 1277 | for (in = 0; in < BH_LRU_SIZE; in++) { |
| 1278 | struct buffer_head *bh2 = |
| 1279 | __this_cpu_read(bh_lrus.bhs[in]); |
| 1280 | |
| 1281 | if (bh2 == bh) { |
| 1282 | __brelse(bh2); |
| 1283 | } else { |
| 1284 | if (out >= BH_LRU_SIZE) { |
| 1285 | BUG_ON(evictee != NULL); |
| 1286 | evictee = bh2; |
| 1287 | } else { |
| 1288 | bhs[out++] = bh2; |
| 1289 | } |
| 1290 | } |
| 1291 | } |
| 1292 | while (out < BH_LRU_SIZE) |
| 1293 | bhs[out++] = NULL; |
| 1294 | memcpy(this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs)); |
| 1295 | } |
| 1296 | bh_lru_unlock(); |
| 1297 | |
| 1298 | if (evictee) |
| 1299 | __brelse(evictee); |
| 1300 | } |
| 1301 | |
| 1302 | /* |
| 1303 | * Look up the bh in this cpu's LRU. If it's there, move it to the head. |
| 1304 | */ |
| 1305 | static struct buffer_head * |
| 1306 | lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size) |
| 1307 | { |
| 1308 | struct buffer_head *ret = NULL; |
| 1309 | unsigned int i; |
| 1310 | |
| 1311 | check_irqs_on(); |
| 1312 | bh_lru_lock(); |
| 1313 | for (i = 0; i < BH_LRU_SIZE; i++) { |
| 1314 | struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]); |
| 1315 | |
| 1316 | if (bh && bh->b_blocknr == block && bh->b_bdev == bdev && |
| 1317 | bh->b_size == size) { |
| 1318 | if (i) { |
| 1319 | while (i) { |
| 1320 | __this_cpu_write(bh_lrus.bhs[i], |
| 1321 | __this_cpu_read(bh_lrus.bhs[i - 1])); |
| 1322 | i--; |
| 1323 | } |
| 1324 | __this_cpu_write(bh_lrus.bhs[0], bh); |
| 1325 | } |
| 1326 | get_bh(bh); |
| 1327 | ret = bh; |
| 1328 | break; |
| 1329 | } |
| 1330 | } |
| 1331 | bh_lru_unlock(); |
| 1332 | return ret; |
| 1333 | } |
| 1334 | |
| 1335 | /* |
| 1336 | * Perform a pagecache lookup for the matching buffer. If it's there, refresh |
| 1337 | * it in the LRU and mark it as accessed. If it is not present then return |
| 1338 | * NULL |
| 1339 | */ |
| 1340 | struct buffer_head * |
| 1341 | __find_get_block(struct block_device *bdev, sector_t block, unsigned size) |
| 1342 | { |
| 1343 | struct buffer_head *bh = lookup_bh_lru(bdev, block, size); |
| 1344 | |
| 1345 | if (bh == NULL) { |
| 1346 | /* __find_get_block_slow will mark the page accessed */ |
| 1347 | bh = __find_get_block_slow(bdev, block); |
| 1348 | if (bh) |
| 1349 | bh_lru_install(bh); |
| 1350 | } else |
| 1351 | touch_buffer(bh); |
| 1352 | |
| 1353 | return bh; |
| 1354 | } |
| 1355 | EXPORT_SYMBOL(__find_get_block); |
| 1356 | |
| 1357 | /* |
| 1358 | * __getblk_gfp() will locate (and, if necessary, create) the buffer_head |
| 1359 | * which corresponds to the passed block_device, block and size. The |
| 1360 | * returned buffer has its reference count incremented. |
| 1361 | * |
| 1362 | * __getblk_gfp() will lock up the machine if grow_dev_page's |
| 1363 | * try_to_free_buffers() attempt is failing. FIXME, perhaps? |
| 1364 | */ |
| 1365 | struct buffer_head * |
| 1366 | __getblk_gfp(struct block_device *bdev, sector_t block, |
| 1367 | unsigned size, gfp_t gfp) |
| 1368 | { |
| 1369 | struct buffer_head *bh = __find_get_block(bdev, block, size); |
| 1370 | |
| 1371 | might_sleep(); |
| 1372 | if (bh == NULL) |
| 1373 | bh = __getblk_slow(bdev, block, size, gfp); |
| 1374 | return bh; |
| 1375 | } |
| 1376 | EXPORT_SYMBOL(__getblk_gfp); |
| 1377 | |
| 1378 | /* |
| 1379 | * Do async read-ahead on a buffer.. |
| 1380 | */ |
| 1381 | void __breadahead(struct block_device *bdev, sector_t block, unsigned size) |
| 1382 | { |
| 1383 | struct buffer_head *bh = __getblk(bdev, block, size); |
| 1384 | if (likely(bh)) { |
| 1385 | ll_rw_block(READA, 1, &bh); |
| 1386 | brelse(bh); |
| 1387 | } |
| 1388 | } |
| 1389 | EXPORT_SYMBOL(__breadahead); |
| 1390 | |
| 1391 | /** |
| 1392 | * __bread_gfp() - reads a specified block and returns the bh |
| 1393 | * @bdev: the block_device to read from |
| 1394 | * @block: number of block |
| 1395 | * @size: size (in bytes) to read |
| 1396 | * @gfp: page allocation flag |
| 1397 | * |
| 1398 | * Reads a specified block, and returns buffer head that contains it. |
| 1399 | * The page cache can be allocated from non-movable area |
| 1400 | * not to prevent page migration if you set gfp to zero. |
| 1401 | * It returns NULL if the block was unreadable. |
| 1402 | */ |
| 1403 | struct buffer_head * |
| 1404 | __bread_gfp(struct block_device *bdev, sector_t block, |
| 1405 | unsigned size, gfp_t gfp) |
| 1406 | { |
| 1407 | struct buffer_head *bh = __getblk_gfp(bdev, block, size, gfp); |
| 1408 | |
| 1409 | if (likely(bh) && !buffer_uptodate(bh)) |
| 1410 | bh = __bread_slow(bh); |
| 1411 | return bh; |
| 1412 | } |
| 1413 | EXPORT_SYMBOL(__bread_gfp); |
| 1414 | |
| 1415 | /* |
| 1416 | * invalidate_bh_lrus() is called rarely - but not only at unmount. |
| 1417 | * This doesn't race because it runs in each cpu either in irq |
| 1418 | * or with preempt disabled. |
| 1419 | */ |
| 1420 | static void invalidate_bh_lru(void *arg) |
| 1421 | { |
| 1422 | struct bh_lru *b = &get_cpu_var(bh_lrus); |
| 1423 | int i; |
| 1424 | |
| 1425 | for (i = 0; i < BH_LRU_SIZE; i++) { |
| 1426 | brelse(b->bhs[i]); |
| 1427 | b->bhs[i] = NULL; |
| 1428 | } |
| 1429 | put_cpu_var(bh_lrus); |
| 1430 | } |
| 1431 | |
| 1432 | static bool has_bh_in_lru(int cpu, void *dummy) |
| 1433 | { |
| 1434 | struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu); |
| 1435 | int i; |
| 1436 | |
| 1437 | for (i = 0; i < BH_LRU_SIZE; i++) { |
| 1438 | if (b->bhs[i]) |
| 1439 | return 1; |
| 1440 | } |
| 1441 | |
| 1442 | return 0; |
| 1443 | } |
| 1444 | |
| 1445 | void invalidate_bh_lrus(void) |
| 1446 | { |
| 1447 | on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL); |
| 1448 | } |
| 1449 | EXPORT_SYMBOL_GPL(invalidate_bh_lrus); |
| 1450 | |
| 1451 | void set_bh_page(struct buffer_head *bh, |
| 1452 | struct page *page, unsigned long offset) |
| 1453 | { |
| 1454 | bh->b_page = page; |
| 1455 | BUG_ON(offset >= PAGE_SIZE); |
| 1456 | if (PageHighMem(page)) |
| 1457 | /* |
| 1458 | * This catches illegal uses and preserves the offset: |
| 1459 | */ |
| 1460 | bh->b_data = (char *)(0 + offset); |
| 1461 | else |
| 1462 | bh->b_data = page_address(page) + offset; |
| 1463 | } |
| 1464 | EXPORT_SYMBOL(set_bh_page); |
| 1465 | |
| 1466 | /* |
| 1467 | * Called when truncating a buffer on a page completely. |
| 1468 | */ |
| 1469 | |
| 1470 | /* Bits that are cleared during an invalidate */ |
| 1471 | #define BUFFER_FLAGS_DISCARD \ |
| 1472 | (1 << BH_Mapped | 1 << BH_New | 1 << BH_Req | \ |
| 1473 | 1 << BH_Delay | 1 << BH_Unwritten) |
| 1474 | |
| 1475 | static void discard_buffer(struct buffer_head * bh) |
| 1476 | { |
| 1477 | unsigned long b_state, b_state_old; |
| 1478 | |
| 1479 | lock_buffer(bh); |
| 1480 | clear_buffer_dirty(bh); |
| 1481 | bh->b_bdev = NULL; |
| 1482 | b_state = bh->b_state; |
| 1483 | for (;;) { |
| 1484 | b_state_old = cmpxchg(&bh->b_state, b_state, |
| 1485 | (b_state & ~BUFFER_FLAGS_DISCARD)); |
| 1486 | if (b_state_old == b_state) |
| 1487 | break; |
| 1488 | b_state = b_state_old; |
| 1489 | } |
| 1490 | unlock_buffer(bh); |
| 1491 | } |
| 1492 | |
| 1493 | /** |
| 1494 | * block_invalidatepage - invalidate part or all of a buffer-backed page |
| 1495 | * |
| 1496 | * @page: the page which is affected |
| 1497 | * @offset: start of the range to invalidate |
| 1498 | * @length: length of the range to invalidate |
| 1499 | * |
| 1500 | * block_invalidatepage() is called when all or part of the page has become |
| 1501 | * invalidated by a truncate operation. |
| 1502 | * |
| 1503 | * block_invalidatepage() does not have to release all buffers, but it must |
| 1504 | * ensure that no dirty buffer is left outside @offset and that no I/O |
| 1505 | * is underway against any of the blocks which are outside the truncation |
| 1506 | * point. Because the caller is about to free (and possibly reuse) those |
| 1507 | * blocks on-disk. |
| 1508 | */ |
| 1509 | void block_invalidatepage(struct page *page, unsigned int offset, |
| 1510 | unsigned int length) |
| 1511 | { |
| 1512 | struct buffer_head *head, *bh, *next; |
| 1513 | unsigned int curr_off = 0; |
| 1514 | unsigned int stop = length + offset; |
| 1515 | |
| 1516 | BUG_ON(!PageLocked(page)); |
| 1517 | if (!page_has_buffers(page)) |
| 1518 | goto out; |
| 1519 | |
| 1520 | /* |
| 1521 | * Check for overflow |
| 1522 | */ |
| 1523 | BUG_ON(stop > PAGE_CACHE_SIZE || stop < length); |
| 1524 | |
| 1525 | head = page_buffers(page); |
| 1526 | bh = head; |
| 1527 | do { |
| 1528 | unsigned int next_off = curr_off + bh->b_size; |
| 1529 | next = bh->b_this_page; |
| 1530 | |
| 1531 | /* |
| 1532 | * Are we still fully in range ? |
| 1533 | */ |
| 1534 | if (next_off > stop) |
| 1535 | goto out; |
| 1536 | |
| 1537 | /* |
| 1538 | * is this block fully invalidated? |
| 1539 | */ |
| 1540 | if (offset <= curr_off) |
| 1541 | discard_buffer(bh); |
| 1542 | curr_off = next_off; |
| 1543 | bh = next; |
| 1544 | } while (bh != head); |
| 1545 | |
| 1546 | /* |
| 1547 | * We release buffers only if the entire page is being invalidated. |
| 1548 | * The get_block cached value has been unconditionally invalidated, |
| 1549 | * so real IO is not possible anymore. |
| 1550 | */ |
| 1551 | if (offset == 0) |
| 1552 | try_to_release_page(page, 0); |
| 1553 | out: |
| 1554 | return; |
| 1555 | } |
| 1556 | EXPORT_SYMBOL(block_invalidatepage); |
| 1557 | |
| 1558 | |
| 1559 | /* |
| 1560 | * We attach and possibly dirty the buffers atomically wrt |
| 1561 | * __set_page_dirty_buffers() via private_lock. try_to_free_buffers |
| 1562 | * is already excluded via the page lock. |
| 1563 | */ |
| 1564 | void create_empty_buffers(struct page *page, |
| 1565 | unsigned long blocksize, unsigned long b_state) |
| 1566 | { |
| 1567 | struct buffer_head *bh, *head, *tail; |
| 1568 | |
| 1569 | head = alloc_page_buffers(page, blocksize, 1); |
| 1570 | bh = head; |
| 1571 | do { |
| 1572 | bh->b_state |= b_state; |
| 1573 | tail = bh; |
| 1574 | bh = bh->b_this_page; |
| 1575 | } while (bh); |
| 1576 | tail->b_this_page = head; |
| 1577 | |
| 1578 | spin_lock(&page->mapping->private_lock); |
| 1579 | if (PageUptodate(page) || PageDirty(page)) { |
| 1580 | bh = head; |
| 1581 | do { |
| 1582 | if (PageDirty(page)) |
| 1583 | set_buffer_dirty(bh); |
| 1584 | if (PageUptodate(page)) |
| 1585 | set_buffer_uptodate(bh); |
| 1586 | bh = bh->b_this_page; |
| 1587 | } while (bh != head); |
| 1588 | } |
| 1589 | attach_page_buffers(page, head); |
| 1590 | spin_unlock(&page->mapping->private_lock); |
| 1591 | } |
| 1592 | EXPORT_SYMBOL(create_empty_buffers); |
| 1593 | |
| 1594 | /* |
| 1595 | * We are taking a block for data and we don't want any output from any |
| 1596 | * buffer-cache aliases starting from return from that function and |
| 1597 | * until the moment when something will explicitly mark the buffer |
| 1598 | * dirty (hopefully that will not happen until we will free that block ;-) |
| 1599 | * We don't even need to mark it not-uptodate - nobody can expect |
| 1600 | * anything from a newly allocated buffer anyway. We used to used |
| 1601 | * unmap_buffer() for such invalidation, but that was wrong. We definitely |
| 1602 | * don't want to mark the alias unmapped, for example - it would confuse |
| 1603 | * anyone who might pick it with bread() afterwards... |
| 1604 | * |
| 1605 | * Also.. Note that bforget() doesn't lock the buffer. So there can |
| 1606 | * be writeout I/O going on against recently-freed buffers. We don't |
| 1607 | * wait on that I/O in bforget() - it's more efficient to wait on the I/O |
| 1608 | * only if we really need to. That happens here. |
| 1609 | */ |
| 1610 | void unmap_underlying_metadata(struct block_device *bdev, sector_t block) |
| 1611 | { |
| 1612 | struct buffer_head *old_bh; |
| 1613 | |
| 1614 | might_sleep(); |
| 1615 | |
| 1616 | old_bh = __find_get_block_slow(bdev, block); |
| 1617 | if (old_bh) { |
| 1618 | clear_buffer_dirty(old_bh); |
| 1619 | wait_on_buffer(old_bh); |
| 1620 | clear_buffer_req(old_bh); |
| 1621 | __brelse(old_bh); |
| 1622 | } |
| 1623 | } |
| 1624 | EXPORT_SYMBOL(unmap_underlying_metadata); |
| 1625 | |
| 1626 | /* |
| 1627 | * Size is a power-of-two in the range 512..PAGE_SIZE, |
| 1628 | * and the case we care about most is PAGE_SIZE. |
| 1629 | * |
| 1630 | * So this *could* possibly be written with those |
| 1631 | * constraints in mind (relevant mostly if some |
| 1632 | * architecture has a slow bit-scan instruction) |
| 1633 | */ |
| 1634 | static inline int block_size_bits(unsigned int blocksize) |
| 1635 | { |
| 1636 | return ilog2(blocksize); |
| 1637 | } |
| 1638 | |
| 1639 | static struct buffer_head *create_page_buffers(struct page *page, struct inode *inode, unsigned int b_state) |
| 1640 | { |
| 1641 | BUG_ON(!PageLocked(page)); |
| 1642 | |
| 1643 | if (!page_has_buffers(page)) |
| 1644 | create_empty_buffers(page, 1 << ACCESS_ONCE(inode->i_blkbits), b_state); |
| 1645 | return page_buffers(page); |
| 1646 | } |
| 1647 | |
| 1648 | /* |
| 1649 | * NOTE! All mapped/uptodate combinations are valid: |
| 1650 | * |
| 1651 | * Mapped Uptodate Meaning |
| 1652 | * |
| 1653 | * No No "unknown" - must do get_block() |
| 1654 | * No Yes "hole" - zero-filled |
| 1655 | * Yes No "allocated" - allocated on disk, not read in |
| 1656 | * Yes Yes "valid" - allocated and up-to-date in memory. |
| 1657 | * |
| 1658 | * "Dirty" is valid only with the last case (mapped+uptodate). |
| 1659 | */ |
| 1660 | |
| 1661 | /* |
| 1662 | * While block_write_full_page is writing back the dirty buffers under |
| 1663 | * the page lock, whoever dirtied the buffers may decide to clean them |
| 1664 | * again at any time. We handle that by only looking at the buffer |
| 1665 | * state inside lock_buffer(). |
| 1666 | * |
| 1667 | * If block_write_full_page() is called for regular writeback |
| 1668 | * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a |
| 1669 | * locked buffer. This only can happen if someone has written the buffer |
| 1670 | * directly, with submit_bh(). At the address_space level PageWriteback |
| 1671 | * prevents this contention from occurring. |
| 1672 | * |
| 1673 | * If block_write_full_page() is called with wbc->sync_mode == |
| 1674 | * WB_SYNC_ALL, the writes are posted using WRITE_SYNC; this |
| 1675 | * causes the writes to be flagged as synchronous writes. |
| 1676 | */ |
| 1677 | static int __block_write_full_page(struct inode *inode, struct page *page, |
| 1678 | get_block_t *get_block, struct writeback_control *wbc, |
| 1679 | bh_end_io_t *handler) |
| 1680 | { |
| 1681 | int err; |
| 1682 | sector_t block; |
| 1683 | sector_t last_block; |
| 1684 | struct buffer_head *bh, *head; |
| 1685 | unsigned int blocksize, bbits; |
| 1686 | int nr_underway = 0; |
| 1687 | int write_op = (wbc->sync_mode == WB_SYNC_ALL ? |
| 1688 | WRITE_SYNC : WRITE); |
| 1689 | |
| 1690 | head = create_page_buffers(page, inode, |
| 1691 | (1 << BH_Dirty)|(1 << BH_Uptodate)); |
| 1692 | |
| 1693 | /* |
| 1694 | * Be very careful. We have no exclusion from __set_page_dirty_buffers |
| 1695 | * here, and the (potentially unmapped) buffers may become dirty at |
| 1696 | * any time. If a buffer becomes dirty here after we've inspected it |
| 1697 | * then we just miss that fact, and the page stays dirty. |
| 1698 | * |
| 1699 | * Buffers outside i_size may be dirtied by __set_page_dirty_buffers; |
| 1700 | * handle that here by just cleaning them. |
| 1701 | */ |
| 1702 | |
| 1703 | bh = head; |
| 1704 | blocksize = bh->b_size; |
| 1705 | bbits = block_size_bits(blocksize); |
| 1706 | |
| 1707 | block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits); |
| 1708 | last_block = (i_size_read(inode) - 1) >> bbits; |
| 1709 | |
| 1710 | /* |
| 1711 | * Get all the dirty buffers mapped to disk addresses and |
| 1712 | * handle any aliases from the underlying blockdev's mapping. |
| 1713 | */ |
| 1714 | do { |
| 1715 | if (block > last_block) { |
| 1716 | /* |
| 1717 | * mapped buffers outside i_size will occur, because |
| 1718 | * this page can be outside i_size when there is a |
| 1719 | * truncate in progress. |
| 1720 | */ |
| 1721 | /* |
| 1722 | * The buffer was zeroed by block_write_full_page() |
| 1723 | */ |
| 1724 | clear_buffer_dirty(bh); |
| 1725 | set_buffer_uptodate(bh); |
| 1726 | } else if ((!buffer_mapped(bh) || buffer_delay(bh)) && |
| 1727 | buffer_dirty(bh)) { |
| 1728 | WARN_ON(bh->b_size != blocksize); |
| 1729 | err = get_block(inode, block, bh, 1); |
| 1730 | if (err) |
| 1731 | goto recover; |
| 1732 | clear_buffer_delay(bh); |
| 1733 | if (buffer_new(bh)) { |
| 1734 | /* blockdev mappings never come here */ |
| 1735 | clear_buffer_new(bh); |
| 1736 | unmap_underlying_metadata(bh->b_bdev, |
| 1737 | bh->b_blocknr); |
| 1738 | } |
| 1739 | } |
| 1740 | bh = bh->b_this_page; |
| 1741 | block++; |
| 1742 | } while (bh != head); |
| 1743 | |
| 1744 | do { |
| 1745 | if (!buffer_mapped(bh)) |
| 1746 | continue; |
| 1747 | /* |
| 1748 | * If it's a fully non-blocking write attempt and we cannot |
| 1749 | * lock the buffer then redirty the page. Note that this can |
| 1750 | * potentially cause a busy-wait loop from writeback threads |
| 1751 | * and kswapd activity, but those code paths have their own |
| 1752 | * higher-level throttling. |
| 1753 | */ |
| 1754 | if (wbc->sync_mode != WB_SYNC_NONE) { |
| 1755 | lock_buffer(bh); |
| 1756 | } else if (!trylock_buffer(bh)) { |
| 1757 | redirty_page_for_writepage(wbc, page); |
| 1758 | continue; |
| 1759 | } |
| 1760 | if (test_clear_buffer_dirty(bh)) { |
| 1761 | mark_buffer_async_write_endio(bh, handler); |
| 1762 | } else { |
| 1763 | unlock_buffer(bh); |
| 1764 | } |
| 1765 | } while ((bh = bh->b_this_page) != head); |
| 1766 | |
| 1767 | /* |
| 1768 | * The page and its buffers are protected by PageWriteback(), so we can |
| 1769 | * drop the bh refcounts early. |
| 1770 | */ |
| 1771 | BUG_ON(PageWriteback(page)); |
| 1772 | set_page_writeback(page); |
| 1773 | |
| 1774 | do { |
| 1775 | struct buffer_head *next = bh->b_this_page; |
| 1776 | if (buffer_async_write(bh)) { |
| 1777 | submit_bh(write_op, bh); |
| 1778 | nr_underway++; |
| 1779 | } |
| 1780 | bh = next; |
| 1781 | } while (bh != head); |
| 1782 | unlock_page(page); |
| 1783 | |
| 1784 | err = 0; |
| 1785 | done: |
| 1786 | if (nr_underway == 0) { |
| 1787 | /* |
| 1788 | * The page was marked dirty, but the buffers were |
| 1789 | * clean. Someone wrote them back by hand with |
| 1790 | * ll_rw_block/submit_bh. A rare case. |
| 1791 | */ |
| 1792 | end_page_writeback(page); |
| 1793 | |
| 1794 | /* |
| 1795 | * The page and buffer_heads can be released at any time from |
| 1796 | * here on. |
| 1797 | */ |
| 1798 | } |
| 1799 | return err; |
| 1800 | |
| 1801 | recover: |
| 1802 | /* |
| 1803 | * ENOSPC, or some other error. We may already have added some |
| 1804 | * blocks to the file, so we need to write these out to avoid |
| 1805 | * exposing stale data. |
| 1806 | * The page is currently locked and not marked for writeback |
| 1807 | */ |
| 1808 | bh = head; |
| 1809 | /* Recovery: lock and submit the mapped buffers */ |
| 1810 | do { |
| 1811 | if (buffer_mapped(bh) && buffer_dirty(bh) && |
| 1812 | !buffer_delay(bh)) { |
| 1813 | lock_buffer(bh); |
| 1814 | mark_buffer_async_write_endio(bh, handler); |
| 1815 | } else { |
| 1816 | /* |
| 1817 | * The buffer may have been set dirty during |
| 1818 | * attachment to a dirty page. |
| 1819 | */ |
| 1820 | clear_buffer_dirty(bh); |
| 1821 | } |
| 1822 | } while ((bh = bh->b_this_page) != head); |
| 1823 | SetPageError(page); |
| 1824 | BUG_ON(PageWriteback(page)); |
| 1825 | mapping_set_error(page->mapping, err); |
| 1826 | set_page_writeback(page); |
| 1827 | do { |
| 1828 | struct buffer_head *next = bh->b_this_page; |
| 1829 | if (buffer_async_write(bh)) { |
| 1830 | clear_buffer_dirty(bh); |
| 1831 | submit_bh(write_op, bh); |
| 1832 | nr_underway++; |
| 1833 | } |
| 1834 | bh = next; |
| 1835 | } while (bh != head); |
| 1836 | unlock_page(page); |
| 1837 | goto done; |
| 1838 | } |
| 1839 | |
| 1840 | /* |
| 1841 | * If a page has any new buffers, zero them out here, and mark them uptodate |
| 1842 | * and dirty so they'll be written out (in order to prevent uninitialised |
| 1843 | * block data from leaking). And clear the new bit. |
| 1844 | */ |
| 1845 | void page_zero_new_buffers(struct page *page, unsigned from, unsigned to) |
| 1846 | { |
| 1847 | unsigned int block_start, block_end; |
| 1848 | struct buffer_head *head, *bh; |
| 1849 | |
| 1850 | BUG_ON(!PageLocked(page)); |
| 1851 | if (!page_has_buffers(page)) |
| 1852 | return; |
| 1853 | |
| 1854 | bh = head = page_buffers(page); |
| 1855 | block_start = 0; |
| 1856 | do { |
| 1857 | block_end = block_start + bh->b_size; |
| 1858 | |
| 1859 | if (buffer_new(bh)) { |
| 1860 | if (block_end > from && block_start < to) { |
| 1861 | if (!PageUptodate(page)) { |
| 1862 | unsigned start, size; |
| 1863 | |
| 1864 | start = max(from, block_start); |
| 1865 | size = min(to, block_end) - start; |
| 1866 | |
| 1867 | zero_user(page, start, size); |
| 1868 | set_buffer_uptodate(bh); |
| 1869 | } |
| 1870 | |
| 1871 | clear_buffer_new(bh); |
| 1872 | mark_buffer_dirty(bh); |
| 1873 | } |
| 1874 | } |
| 1875 | |
| 1876 | block_start = block_end; |
| 1877 | bh = bh->b_this_page; |
| 1878 | } while (bh != head); |
| 1879 | } |
| 1880 | EXPORT_SYMBOL(page_zero_new_buffers); |
| 1881 | |
| 1882 | int __block_write_begin(struct page *page, loff_t pos, unsigned len, |
| 1883 | get_block_t *get_block) |
| 1884 | { |
| 1885 | unsigned from = pos & (PAGE_CACHE_SIZE - 1); |
| 1886 | unsigned to = from + len; |
| 1887 | struct inode *inode = page->mapping->host; |
| 1888 | unsigned block_start, block_end; |
| 1889 | sector_t block; |
| 1890 | int err = 0; |
| 1891 | unsigned blocksize, bbits; |
| 1892 | struct buffer_head *bh, *head, *wait[2], **wait_bh=wait; |
| 1893 | |
| 1894 | BUG_ON(!PageLocked(page)); |
| 1895 | BUG_ON(from > PAGE_CACHE_SIZE); |
| 1896 | BUG_ON(to > PAGE_CACHE_SIZE); |
| 1897 | BUG_ON(from > to); |
| 1898 | |
| 1899 | head = create_page_buffers(page, inode, 0); |
| 1900 | blocksize = head->b_size; |
| 1901 | bbits = block_size_bits(blocksize); |
| 1902 | |
| 1903 | block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits); |
| 1904 | |
| 1905 | for(bh = head, block_start = 0; bh != head || !block_start; |
| 1906 | block++, block_start=block_end, bh = bh->b_this_page) { |
| 1907 | block_end = block_start + blocksize; |
| 1908 | if (block_end <= from || block_start >= to) { |
| 1909 | if (PageUptodate(page)) { |
| 1910 | if (!buffer_uptodate(bh)) |
| 1911 | set_buffer_uptodate(bh); |
| 1912 | } |
| 1913 | continue; |
| 1914 | } |
| 1915 | if (buffer_new(bh)) |
| 1916 | clear_buffer_new(bh); |
| 1917 | if (!buffer_mapped(bh)) { |
| 1918 | WARN_ON(bh->b_size != blocksize); |
| 1919 | err = get_block(inode, block, bh, 1); |
| 1920 | if (err) |
| 1921 | break; |
| 1922 | if (buffer_new(bh)) { |
| 1923 | unmap_underlying_metadata(bh->b_bdev, |
| 1924 | bh->b_blocknr); |
| 1925 | if (PageUptodate(page)) { |
| 1926 | clear_buffer_new(bh); |
| 1927 | set_buffer_uptodate(bh); |
| 1928 | mark_buffer_dirty(bh); |
| 1929 | continue; |
| 1930 | } |
| 1931 | if (block_end > to || block_start < from) |
| 1932 | zero_user_segments(page, |
| 1933 | to, block_end, |
| 1934 | block_start, from); |
| 1935 | continue; |
| 1936 | } |
| 1937 | } |
| 1938 | if (PageUptodate(page)) { |
| 1939 | if (!buffer_uptodate(bh)) |
| 1940 | set_buffer_uptodate(bh); |
| 1941 | continue; |
| 1942 | } |
| 1943 | if (!buffer_uptodate(bh) && !buffer_delay(bh) && |
| 1944 | !buffer_unwritten(bh) && |
| 1945 | (block_start < from || block_end > to)) { |
| 1946 | ll_rw_block(READ, 1, &bh); |
| 1947 | *wait_bh++=bh; |
| 1948 | } |
| 1949 | } |
| 1950 | /* |
| 1951 | * If we issued read requests - let them complete. |
| 1952 | */ |
| 1953 | while(wait_bh > wait) { |
| 1954 | wait_on_buffer(*--wait_bh); |
| 1955 | if (!buffer_uptodate(*wait_bh)) |
| 1956 | err = -EIO; |
| 1957 | } |
| 1958 | if (unlikely(err)) |
| 1959 | page_zero_new_buffers(page, from, to); |
| 1960 | return err; |
| 1961 | } |
| 1962 | EXPORT_SYMBOL(__block_write_begin); |
| 1963 | |
| 1964 | static int __block_commit_write(struct inode *inode, struct page *page, |
| 1965 | unsigned from, unsigned to) |
| 1966 | { |
| 1967 | unsigned block_start, block_end; |
| 1968 | int partial = 0; |
| 1969 | unsigned blocksize; |
| 1970 | struct buffer_head *bh, *head; |
| 1971 | |
| 1972 | bh = head = page_buffers(page); |
| 1973 | blocksize = bh->b_size; |
| 1974 | |
| 1975 | block_start = 0; |
| 1976 | do { |
| 1977 | block_end = block_start + blocksize; |
| 1978 | if (block_end <= from || block_start >= to) { |
| 1979 | if (!buffer_uptodate(bh)) |
| 1980 | partial = 1; |
| 1981 | } else { |
| 1982 | set_buffer_uptodate(bh); |
| 1983 | mark_buffer_dirty(bh); |
| 1984 | } |
| 1985 | clear_buffer_new(bh); |
| 1986 | |
| 1987 | block_start = block_end; |
| 1988 | bh = bh->b_this_page; |
| 1989 | } while (bh != head); |
| 1990 | |
| 1991 | /* |
| 1992 | * If this is a partial write which happened to make all buffers |
| 1993 | * uptodate then we can optimize away a bogus readpage() for |
| 1994 | * the next read(). Here we 'discover' whether the page went |
| 1995 | * uptodate as a result of this (potentially partial) write. |
| 1996 | */ |
| 1997 | if (!partial) |
| 1998 | SetPageUptodate(page); |
| 1999 | return 0; |
| 2000 | } |
| 2001 | |
| 2002 | /* |
| 2003 | * block_write_begin takes care of the basic task of block allocation and |
| 2004 | * bringing partial write blocks uptodate first. |
| 2005 | * |
| 2006 | * The filesystem needs to handle block truncation upon failure. |
| 2007 | */ |
| 2008 | int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len, |
| 2009 | unsigned flags, struct page **pagep, get_block_t *get_block) |
| 2010 | { |
| 2011 | pgoff_t index = pos >> PAGE_CACHE_SHIFT; |
| 2012 | struct page *page; |
| 2013 | int status; |
| 2014 | |
| 2015 | page = grab_cache_page_write_begin(mapping, index, flags); |
| 2016 | if (!page) |
| 2017 | return -ENOMEM; |
| 2018 | |
| 2019 | status = __block_write_begin(page, pos, len, get_block); |
| 2020 | if (unlikely(status)) { |
| 2021 | unlock_page(page); |
| 2022 | page_cache_release(page); |
| 2023 | page = NULL; |
| 2024 | } |
| 2025 | |
| 2026 | *pagep = page; |
| 2027 | return status; |
| 2028 | } |
| 2029 | EXPORT_SYMBOL(block_write_begin); |
| 2030 | |
| 2031 | int block_write_end(struct file *file, struct address_space *mapping, |
| 2032 | loff_t pos, unsigned len, unsigned copied, |
| 2033 | struct page *page, void *fsdata) |
| 2034 | { |
| 2035 | struct inode *inode = mapping->host; |
| 2036 | unsigned start; |
| 2037 | |
| 2038 | start = pos & (PAGE_CACHE_SIZE - 1); |
| 2039 | |
| 2040 | if (unlikely(copied < len)) { |
| 2041 | /* |
| 2042 | * The buffers that were written will now be uptodate, so we |
| 2043 | * don't have to worry about a readpage reading them and |
| 2044 | * overwriting a partial write. However if we have encountered |
| 2045 | * a short write and only partially written into a buffer, it |
| 2046 | * will not be marked uptodate, so a readpage might come in and |
| 2047 | * destroy our partial write. |
| 2048 | * |
| 2049 | * Do the simplest thing, and just treat any short write to a |
| 2050 | * non uptodate page as a zero-length write, and force the |
| 2051 | * caller to redo the whole thing. |
| 2052 | */ |
| 2053 | if (!PageUptodate(page)) |
| 2054 | copied = 0; |
| 2055 | |
| 2056 | page_zero_new_buffers(page, start+copied, start+len); |
| 2057 | } |
| 2058 | flush_dcache_page(page); |
| 2059 | |
| 2060 | /* This could be a short (even 0-length) commit */ |
| 2061 | __block_commit_write(inode, page, start, start+copied); |
| 2062 | |
| 2063 | return copied; |
| 2064 | } |
| 2065 | EXPORT_SYMBOL(block_write_end); |
| 2066 | |
| 2067 | int generic_write_end(struct file *file, struct address_space *mapping, |
| 2068 | loff_t pos, unsigned len, unsigned copied, |
| 2069 | struct page *page, void *fsdata) |
| 2070 | { |
| 2071 | struct inode *inode = mapping->host; |
| 2072 | loff_t old_size = inode->i_size; |
| 2073 | int i_size_changed = 0; |
| 2074 | |
| 2075 | copied = block_write_end(file, mapping, pos, len, copied, page, fsdata); |
| 2076 | |
| 2077 | /* |
| 2078 | * No need to use i_size_read() here, the i_size |
| 2079 | * cannot change under us because we hold i_mutex. |
| 2080 | * |
| 2081 | * But it's important to update i_size while still holding page lock: |
| 2082 | * page writeout could otherwise come in and zero beyond i_size. |
| 2083 | */ |
| 2084 | if (pos+copied > inode->i_size) { |
| 2085 | i_size_write(inode, pos+copied); |
| 2086 | i_size_changed = 1; |
| 2087 | } |
| 2088 | |
| 2089 | unlock_page(page); |
| 2090 | page_cache_release(page); |
| 2091 | |
| 2092 | if (old_size < pos) |
| 2093 | pagecache_isize_extended(inode, old_size, pos); |
| 2094 | /* |
| 2095 | * Don't mark the inode dirty under page lock. First, it unnecessarily |
| 2096 | * makes the holding time of page lock longer. Second, it forces lock |
| 2097 | * ordering of page lock and transaction start for journaling |
| 2098 | * filesystems. |
| 2099 | */ |
| 2100 | if (i_size_changed) |
| 2101 | mark_inode_dirty(inode); |
| 2102 | |
| 2103 | return copied; |
| 2104 | } |
| 2105 | EXPORT_SYMBOL(generic_write_end); |
| 2106 | |
| 2107 | /* |
| 2108 | * block_is_partially_uptodate checks whether buffers within a page are |
| 2109 | * uptodate or not. |
| 2110 | * |
| 2111 | * Returns true if all buffers which correspond to a file portion |
| 2112 | * we want to read are uptodate. |
| 2113 | */ |
| 2114 | int block_is_partially_uptodate(struct page *page, unsigned long from, |
| 2115 | unsigned long count) |
| 2116 | { |
| 2117 | unsigned block_start, block_end, blocksize; |
| 2118 | unsigned to; |
| 2119 | struct buffer_head *bh, *head; |
| 2120 | int ret = 1; |
| 2121 | |
| 2122 | if (!page_has_buffers(page)) |
| 2123 | return 0; |
| 2124 | |
| 2125 | head = page_buffers(page); |
| 2126 | blocksize = head->b_size; |
| 2127 | to = min_t(unsigned, PAGE_CACHE_SIZE - from, count); |
| 2128 | to = from + to; |
| 2129 | if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize) |
| 2130 | return 0; |
| 2131 | |
| 2132 | bh = head; |
| 2133 | block_start = 0; |
| 2134 | do { |
| 2135 | block_end = block_start + blocksize; |
| 2136 | if (block_end > from && block_start < to) { |
| 2137 | if (!buffer_uptodate(bh)) { |
| 2138 | ret = 0; |
| 2139 | break; |
| 2140 | } |
| 2141 | if (block_end >= to) |
| 2142 | break; |
| 2143 | } |
| 2144 | block_start = block_end; |
| 2145 | bh = bh->b_this_page; |
| 2146 | } while (bh != head); |
| 2147 | |
| 2148 | return ret; |
| 2149 | } |
| 2150 | EXPORT_SYMBOL(block_is_partially_uptodate); |
| 2151 | |
| 2152 | /* |
| 2153 | * Generic "read page" function for block devices that have the normal |
| 2154 | * get_block functionality. This is most of the block device filesystems. |
| 2155 | * Reads the page asynchronously --- the unlock_buffer() and |
| 2156 | * set/clear_buffer_uptodate() functions propagate buffer state into the |
| 2157 | * page struct once IO has completed. |
| 2158 | */ |
| 2159 | int block_read_full_page(struct page *page, get_block_t *get_block) |
| 2160 | { |
| 2161 | struct inode *inode = page->mapping->host; |
| 2162 | sector_t iblock, lblock; |
| 2163 | struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE]; |
| 2164 | unsigned int blocksize, bbits; |
| 2165 | int nr, i; |
| 2166 | int fully_mapped = 1; |
| 2167 | |
| 2168 | head = create_page_buffers(page, inode, 0); |
| 2169 | blocksize = head->b_size; |
| 2170 | bbits = block_size_bits(blocksize); |
| 2171 | |
| 2172 | iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits); |
| 2173 | lblock = (i_size_read(inode)+blocksize-1) >> bbits; |
| 2174 | bh = head; |
| 2175 | nr = 0; |
| 2176 | i = 0; |
| 2177 | |
| 2178 | do { |
| 2179 | if (buffer_uptodate(bh)) |
| 2180 | continue; |
| 2181 | |
| 2182 | if (!buffer_mapped(bh)) { |
| 2183 | int err = 0; |
| 2184 | |
| 2185 | fully_mapped = 0; |
| 2186 | if (iblock < lblock) { |
| 2187 | WARN_ON(bh->b_size != blocksize); |
| 2188 | err = get_block(inode, iblock, bh, 0); |
| 2189 | if (err) |
| 2190 | SetPageError(page); |
| 2191 | } |
| 2192 | if (!buffer_mapped(bh)) { |
| 2193 | zero_user(page, i * blocksize, blocksize); |
| 2194 | if (!err) |
| 2195 | set_buffer_uptodate(bh); |
| 2196 | continue; |
| 2197 | } |
| 2198 | /* |
| 2199 | * get_block() might have updated the buffer |
| 2200 | * synchronously |
| 2201 | */ |
| 2202 | if (buffer_uptodate(bh)) |
| 2203 | continue; |
| 2204 | } |
| 2205 | arr[nr++] = bh; |
| 2206 | } while (i++, iblock++, (bh = bh->b_this_page) != head); |
| 2207 | |
| 2208 | if (fully_mapped) |
| 2209 | SetPageMappedToDisk(page); |
| 2210 | |
| 2211 | if (!nr) { |
| 2212 | /* |
| 2213 | * All buffers are uptodate - we can set the page uptodate |
| 2214 | * as well. But not if get_block() returned an error. |
| 2215 | */ |
| 2216 | if (!PageError(page)) |
| 2217 | SetPageUptodate(page); |
| 2218 | unlock_page(page); |
| 2219 | return 0; |
| 2220 | } |
| 2221 | |
| 2222 | /* Stage two: lock the buffers */ |
| 2223 | for (i = 0; i < nr; i++) { |
| 2224 | bh = arr[i]; |
| 2225 | lock_buffer(bh); |
| 2226 | mark_buffer_async_read(bh); |
| 2227 | } |
| 2228 | |
| 2229 | /* |
| 2230 | * Stage 3: start the IO. Check for uptodateness |
| 2231 | * inside the buffer lock in case another process reading |
| 2232 | * the underlying blockdev brought it uptodate (the sct fix). |
| 2233 | */ |
| 2234 | for (i = 0; i < nr; i++) { |
| 2235 | bh = arr[i]; |
| 2236 | if (buffer_uptodate(bh)) |
| 2237 | end_buffer_async_read(bh, 1); |
| 2238 | else |
| 2239 | submit_bh(READ, bh); |
| 2240 | } |
| 2241 | return 0; |
| 2242 | } |
| 2243 | EXPORT_SYMBOL(block_read_full_page); |
| 2244 | |
| 2245 | /* utility function for filesystems that need to do work on expanding |
| 2246 | * truncates. Uses filesystem pagecache writes to allow the filesystem to |
| 2247 | * deal with the hole. |
| 2248 | */ |
| 2249 | int generic_cont_expand_simple(struct inode *inode, loff_t size) |
| 2250 | { |
| 2251 | struct address_space *mapping = inode->i_mapping; |
| 2252 | struct page *page; |
| 2253 | void *fsdata; |
| 2254 | int err; |
| 2255 | |
| 2256 | err = inode_newsize_ok(inode, size); |
| 2257 | if (err) |
| 2258 | goto out; |
| 2259 | |
| 2260 | err = pagecache_write_begin(NULL, mapping, size, 0, |
| 2261 | AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND, |
| 2262 | &page, &fsdata); |
| 2263 | if (err) |
| 2264 | goto out; |
| 2265 | |
| 2266 | err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata); |
| 2267 | BUG_ON(err > 0); |
| 2268 | |
| 2269 | out: |
| 2270 | return err; |
| 2271 | } |
| 2272 | EXPORT_SYMBOL(generic_cont_expand_simple); |
| 2273 | |
| 2274 | static int cont_expand_zero(struct file *file, struct address_space *mapping, |
| 2275 | loff_t pos, loff_t *bytes) |
| 2276 | { |
| 2277 | struct inode *inode = mapping->host; |
| 2278 | unsigned blocksize = 1 << inode->i_blkbits; |
| 2279 | struct page *page; |
| 2280 | void *fsdata; |
| 2281 | pgoff_t index, curidx; |
| 2282 | loff_t curpos; |
| 2283 | unsigned zerofrom, offset, len; |
| 2284 | int err = 0; |
| 2285 | |
| 2286 | index = pos >> PAGE_CACHE_SHIFT; |
| 2287 | offset = pos & ~PAGE_CACHE_MASK; |
| 2288 | |
| 2289 | while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) { |
| 2290 | zerofrom = curpos & ~PAGE_CACHE_MASK; |
| 2291 | if (zerofrom & (blocksize-1)) { |
| 2292 | *bytes |= (blocksize-1); |
| 2293 | (*bytes)++; |
| 2294 | } |
| 2295 | len = PAGE_CACHE_SIZE - zerofrom; |
| 2296 | |
| 2297 | err = pagecache_write_begin(file, mapping, curpos, len, |
| 2298 | AOP_FLAG_UNINTERRUPTIBLE, |
| 2299 | &page, &fsdata); |
| 2300 | if (err) |
| 2301 | goto out; |
| 2302 | zero_user(page, zerofrom, len); |
| 2303 | err = pagecache_write_end(file, mapping, curpos, len, len, |
| 2304 | page, fsdata); |
| 2305 | if (err < 0) |
| 2306 | goto out; |
| 2307 | BUG_ON(err != len); |
| 2308 | err = 0; |
| 2309 | |
| 2310 | balance_dirty_pages_ratelimited(mapping); |
| 2311 | |
| 2312 | if (unlikely(fatal_signal_pending(current))) { |
| 2313 | err = -EINTR; |
| 2314 | goto out; |
| 2315 | } |
| 2316 | } |
| 2317 | |
| 2318 | /* page covers the boundary, find the boundary offset */ |
| 2319 | if (index == curidx) { |
| 2320 | zerofrom = curpos & ~PAGE_CACHE_MASK; |
| 2321 | /* if we will expand the thing last block will be filled */ |
| 2322 | if (offset <= zerofrom) { |
| 2323 | goto out; |
| 2324 | } |
| 2325 | if (zerofrom & (blocksize-1)) { |
| 2326 | *bytes |= (blocksize-1); |
| 2327 | (*bytes)++; |
| 2328 | } |
| 2329 | len = offset - zerofrom; |
| 2330 | |
| 2331 | err = pagecache_write_begin(file, mapping, curpos, len, |
| 2332 | AOP_FLAG_UNINTERRUPTIBLE, |
| 2333 | &page, &fsdata); |
| 2334 | if (err) |
| 2335 | goto out; |
| 2336 | zero_user(page, zerofrom, len); |
| 2337 | err = pagecache_write_end(file, mapping, curpos, len, len, |
| 2338 | page, fsdata); |
| 2339 | if (err < 0) |
| 2340 | goto out; |
| 2341 | BUG_ON(err != len); |
| 2342 | err = 0; |
| 2343 | } |
| 2344 | out: |
| 2345 | return err; |
| 2346 | } |
| 2347 | |
| 2348 | /* |
| 2349 | * For moronic filesystems that do not allow holes in file. |
| 2350 | * We may have to extend the file. |
| 2351 | */ |
| 2352 | int cont_write_begin(struct file *file, struct address_space *mapping, |
| 2353 | loff_t pos, unsigned len, unsigned flags, |
| 2354 | struct page **pagep, void **fsdata, |
| 2355 | get_block_t *get_block, loff_t *bytes) |
| 2356 | { |
| 2357 | struct inode *inode = mapping->host; |
| 2358 | unsigned blocksize = 1 << inode->i_blkbits; |
| 2359 | unsigned zerofrom; |
| 2360 | int err; |
| 2361 | |
| 2362 | err = cont_expand_zero(file, mapping, pos, bytes); |
| 2363 | if (err) |
| 2364 | return err; |
| 2365 | |
| 2366 | zerofrom = *bytes & ~PAGE_CACHE_MASK; |
| 2367 | if (pos+len > *bytes && zerofrom & (blocksize-1)) { |
| 2368 | *bytes |= (blocksize-1); |
| 2369 | (*bytes)++; |
| 2370 | } |
| 2371 | |
| 2372 | return block_write_begin(mapping, pos, len, flags, pagep, get_block); |
| 2373 | } |
| 2374 | EXPORT_SYMBOL(cont_write_begin); |
| 2375 | |
| 2376 | int block_commit_write(struct page *page, unsigned from, unsigned to) |
| 2377 | { |
| 2378 | struct inode *inode = page->mapping->host; |
| 2379 | __block_commit_write(inode,page,from,to); |
| 2380 | return 0; |
| 2381 | } |
| 2382 | EXPORT_SYMBOL(block_commit_write); |
| 2383 | |
| 2384 | /* |
| 2385 | * block_page_mkwrite() is not allowed to change the file size as it gets |
| 2386 | * called from a page fault handler when a page is first dirtied. Hence we must |
| 2387 | * be careful to check for EOF conditions here. We set the page up correctly |
| 2388 | * for a written page which means we get ENOSPC checking when writing into |
| 2389 | * holes and correct delalloc and unwritten extent mapping on filesystems that |
| 2390 | * support these features. |
| 2391 | * |
| 2392 | * We are not allowed to take the i_mutex here so we have to play games to |
| 2393 | * protect against truncate races as the page could now be beyond EOF. Because |
| 2394 | * truncate writes the inode size before removing pages, once we have the |
| 2395 | * page lock we can determine safely if the page is beyond EOF. If it is not |
| 2396 | * beyond EOF, then the page is guaranteed safe against truncation until we |
| 2397 | * unlock the page. |
| 2398 | * |
| 2399 | * Direct callers of this function should protect against filesystem freezing |
| 2400 | * using sb_start_write() - sb_end_write() functions. |
| 2401 | */ |
| 2402 | int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, |
| 2403 | get_block_t get_block) |
| 2404 | { |
| 2405 | struct page *page = vmf->page; |
| 2406 | struct inode *inode = file_inode(vma->vm_file); |
| 2407 | unsigned long end; |
| 2408 | loff_t size; |
| 2409 | int ret; |
| 2410 | |
| 2411 | lock_page(page); |
| 2412 | size = i_size_read(inode); |
| 2413 | if ((page->mapping != inode->i_mapping) || |
| 2414 | (page_offset(page) > size)) { |
| 2415 | /* We overload EFAULT to mean page got truncated */ |
| 2416 | ret = -EFAULT; |
| 2417 | goto out_unlock; |
| 2418 | } |
| 2419 | |
| 2420 | /* page is wholly or partially inside EOF */ |
| 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_write_begin(page, 0, end, get_block); |
| 2427 | if (!ret) |
| 2428 | ret = block_commit_write(page, 0, end); |
| 2429 | |
| 2430 | if (unlikely(ret < 0)) |
| 2431 | goto out_unlock; |
| 2432 | set_page_dirty(page); |
| 2433 | wait_for_stable_page(page); |
| 2434 | return 0; |
| 2435 | out_unlock: |
| 2436 | unlock_page(page); |
| 2437 | return ret; |
| 2438 | } |
| 2439 | EXPORT_SYMBOL(__block_page_mkwrite); |
| 2440 | |
| 2441 | int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, |
| 2442 | get_block_t get_block) |
| 2443 | { |
| 2444 | int ret; |
| 2445 | struct super_block *sb = file_inode(vma->vm_file)->i_sb; |
| 2446 | |
| 2447 | sb_start_pagefault(sb); |
| 2448 | |
| 2449 | /* |
| 2450 | * Update file times before taking page lock. We may end up failing the |
| 2451 | * fault so this update may be superfluous but who really cares... |
| 2452 | */ |
| 2453 | file_update_time(vma->vm_file); |
| 2454 | |
| 2455 | ret = __block_page_mkwrite(vma, vmf, get_block); |
| 2456 | sb_end_pagefault(sb); |
| 2457 | return block_page_mkwrite_return(ret); |
| 2458 | } |
| 2459 | EXPORT_SYMBOL(block_page_mkwrite); |
| 2460 | |
| 2461 | /* |
| 2462 | * nobh_write_begin()'s prereads are special: the buffer_heads are freed |
| 2463 | * immediately, while under the page lock. So it needs a special end_io |
| 2464 | * handler which does not touch the bh after unlocking it. |
| 2465 | */ |
| 2466 | static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate) |
| 2467 | { |
| 2468 | __end_buffer_read_notouch(bh, uptodate); |
| 2469 | } |
| 2470 | |
| 2471 | /* |
| 2472 | * Attach the singly-linked list of buffers created by nobh_write_begin, to |
| 2473 | * the page (converting it to circular linked list and taking care of page |
| 2474 | * dirty races). |
| 2475 | */ |
| 2476 | static void attach_nobh_buffers(struct page *page, struct buffer_head *head) |
| 2477 | { |
| 2478 | struct buffer_head *bh; |
| 2479 | |
| 2480 | BUG_ON(!PageLocked(page)); |
| 2481 | |
| 2482 | spin_lock(&page->mapping->private_lock); |
| 2483 | bh = head; |
| 2484 | do { |
| 2485 | if (PageDirty(page)) |
| 2486 | set_buffer_dirty(bh); |
| 2487 | if (!bh->b_this_page) |
| 2488 | bh->b_this_page = head; |
| 2489 | bh = bh->b_this_page; |
| 2490 | } while (bh != head); |
| 2491 | attach_page_buffers(page, head); |
| 2492 | spin_unlock(&page->mapping->private_lock); |
| 2493 | } |
| 2494 | |
| 2495 | /* |
| 2496 | * On entry, the page is fully not uptodate. |
| 2497 | * On exit the page is fully uptodate in the areas outside (from,to) |
| 2498 | * The filesystem needs to handle block truncation upon failure. |
| 2499 | */ |
| 2500 | int nobh_write_begin(struct address_space *mapping, |
| 2501 | loff_t pos, unsigned len, unsigned flags, |
| 2502 | struct page **pagep, void **fsdata, |
| 2503 | get_block_t *get_block) |
| 2504 | { |
| 2505 | struct inode *inode = mapping->host; |
| 2506 | const unsigned blkbits = inode->i_blkbits; |
| 2507 | const unsigned blocksize = 1 << blkbits; |
| 2508 | struct buffer_head *head, *bh; |
| 2509 | struct page *page; |
| 2510 | pgoff_t index; |
| 2511 | unsigned from, to; |
| 2512 | unsigned block_in_page; |
| 2513 | unsigned block_start, block_end; |
| 2514 | sector_t block_in_file; |
| 2515 | int nr_reads = 0; |
| 2516 | int ret = 0; |
| 2517 | int is_mapped_to_disk = 1; |
| 2518 | |
| 2519 | index = pos >> PAGE_CACHE_SHIFT; |
| 2520 | from = pos & (PAGE_CACHE_SIZE - 1); |
| 2521 | to = from + len; |
| 2522 | |
| 2523 | page = grab_cache_page_write_begin(mapping, index, flags); |
| 2524 | if (!page) |
| 2525 | return -ENOMEM; |
| 2526 | *pagep = page; |
| 2527 | *fsdata = NULL; |
| 2528 | |
| 2529 | if (page_has_buffers(page)) { |
| 2530 | ret = __block_write_begin(page, pos, len, get_block); |
| 2531 | if (unlikely(ret)) |
| 2532 | goto out_release; |
| 2533 | return ret; |
| 2534 | } |
| 2535 | |
| 2536 | if (PageMappedToDisk(page)) |
| 2537 | return 0; |
| 2538 | |
| 2539 | /* |
| 2540 | * Allocate buffers so that we can keep track of state, and potentially |
| 2541 | * attach them to the page if an error occurs. In the common case of |
| 2542 | * no error, they will just be freed again without ever being attached |
| 2543 | * to the page (which is all OK, because we're under the page lock). |
| 2544 | * |
| 2545 | * Be careful: the buffer linked list is a NULL terminated one, rather |
| 2546 | * than the circular one we're used to. |
| 2547 | */ |
| 2548 | head = alloc_page_buffers(page, blocksize, 0); |
| 2549 | if (!head) { |
| 2550 | ret = -ENOMEM; |
| 2551 | goto out_release; |
| 2552 | } |
| 2553 | |
| 2554 | block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits); |
| 2555 | |
| 2556 | /* |
| 2557 | * We loop across all blocks in the page, whether or not they are |
| 2558 | * part of the affected region. This is so we can discover if the |
| 2559 | * page is fully mapped-to-disk. |
| 2560 | */ |
| 2561 | for (block_start = 0, block_in_page = 0, bh = head; |
| 2562 | block_start < PAGE_CACHE_SIZE; |
| 2563 | block_in_page++, block_start += blocksize, bh = bh->b_this_page) { |
| 2564 | int create; |
| 2565 | |
| 2566 | block_end = block_start + blocksize; |
| 2567 | bh->b_state = 0; |
| 2568 | create = 1; |
| 2569 | if (block_start >= to) |
| 2570 | create = 0; |
| 2571 | ret = get_block(inode, block_in_file + block_in_page, |
| 2572 | bh, create); |
| 2573 | if (ret) |
| 2574 | goto failed; |
| 2575 | if (!buffer_mapped(bh)) |
| 2576 | is_mapped_to_disk = 0; |
| 2577 | if (buffer_new(bh)) |
| 2578 | unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr); |
| 2579 | if (PageUptodate(page)) { |
| 2580 | set_buffer_uptodate(bh); |
| 2581 | continue; |
| 2582 | } |
| 2583 | if (buffer_new(bh) || !buffer_mapped(bh)) { |
| 2584 | zero_user_segments(page, block_start, from, |
| 2585 | to, block_end); |
| 2586 | continue; |
| 2587 | } |
| 2588 | if (buffer_uptodate(bh)) |
| 2589 | continue; /* reiserfs does this */ |
| 2590 | if (block_start < from || block_end > to) { |
| 2591 | lock_buffer(bh); |
| 2592 | bh->b_end_io = end_buffer_read_nobh; |
| 2593 | submit_bh(READ, bh); |
| 2594 | nr_reads++; |
| 2595 | } |
| 2596 | } |
| 2597 | |
| 2598 | if (nr_reads) { |
| 2599 | /* |
| 2600 | * The page is locked, so these buffers are protected from |
| 2601 | * any VM or truncate activity. Hence we don't need to care |
| 2602 | * for the buffer_head refcounts. |
| 2603 | */ |
| 2604 | for (bh = head; bh; bh = bh->b_this_page) { |
| 2605 | wait_on_buffer(bh); |
| 2606 | if (!buffer_uptodate(bh)) |
| 2607 | ret = -EIO; |
| 2608 | } |
| 2609 | if (ret) |
| 2610 | goto failed; |
| 2611 | } |
| 2612 | |
| 2613 | if (is_mapped_to_disk) |
| 2614 | SetPageMappedToDisk(page); |
| 2615 | |
| 2616 | *fsdata = head; /* to be released by nobh_write_end */ |
| 2617 | |
| 2618 | return 0; |
| 2619 | |
| 2620 | failed: |
| 2621 | BUG_ON(!ret); |
| 2622 | /* |
| 2623 | * Error recovery is a bit difficult. We need to zero out blocks that |
| 2624 | * were newly allocated, and dirty them to ensure they get written out. |
| 2625 | * Buffers need to be attached to the page at this point, otherwise |
| 2626 | * the handling of potential IO errors during writeout would be hard |
| 2627 | * (could try doing synchronous writeout, but what if that fails too?) |
| 2628 | */ |
| 2629 | attach_nobh_buffers(page, head); |
| 2630 | page_zero_new_buffers(page, from, to); |
| 2631 | |
| 2632 | out_release: |
| 2633 | unlock_page(page); |
| 2634 | page_cache_release(page); |
| 2635 | *pagep = NULL; |
| 2636 | |
| 2637 | return ret; |
| 2638 | } |
| 2639 | EXPORT_SYMBOL(nobh_write_begin); |
| 2640 | |
| 2641 | int nobh_write_end(struct file *file, struct address_space *mapping, |
| 2642 | loff_t pos, unsigned len, unsigned copied, |
| 2643 | struct page *page, void *fsdata) |
| 2644 | { |
| 2645 | struct inode *inode = page->mapping->host; |
| 2646 | struct buffer_head *head = fsdata; |
| 2647 | struct buffer_head *bh; |
| 2648 | BUG_ON(fsdata != NULL && page_has_buffers(page)); |
| 2649 | |
| 2650 | if (unlikely(copied < len) && head) |
| 2651 | attach_nobh_buffers(page, head); |
| 2652 | if (page_has_buffers(page)) |
| 2653 | return generic_write_end(file, mapping, pos, len, |
| 2654 | copied, page, fsdata); |
| 2655 | |
| 2656 | SetPageUptodate(page); |
| 2657 | set_page_dirty(page); |
| 2658 | if (pos+copied > inode->i_size) { |
| 2659 | i_size_write(inode, pos+copied); |
| 2660 | mark_inode_dirty(inode); |
| 2661 | } |
| 2662 | |
| 2663 | unlock_page(page); |
| 2664 | page_cache_release(page); |
| 2665 | |
| 2666 | while (head) { |
| 2667 | bh = head; |
| 2668 | head = head->b_this_page; |
| 2669 | free_buffer_head(bh); |
| 2670 | } |
| 2671 | |
| 2672 | return copied; |
| 2673 | } |
| 2674 | EXPORT_SYMBOL(nobh_write_end); |
| 2675 | |
| 2676 | /* |
| 2677 | * nobh_writepage() - based on block_full_write_page() except |
| 2678 | * that it tries to operate without attaching bufferheads to |
| 2679 | * the page. |
| 2680 | */ |
| 2681 | int nobh_writepage(struct page *page, get_block_t *get_block, |
| 2682 | struct writeback_control *wbc) |
| 2683 | { |
| 2684 | struct inode * const inode = page->mapping->host; |
| 2685 | loff_t i_size = i_size_read(inode); |
| 2686 | const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT; |
| 2687 | unsigned offset; |
| 2688 | int ret; |
| 2689 | |
| 2690 | /* Is the page fully inside i_size? */ |
| 2691 | if (page->index < end_index) |
| 2692 | goto out; |
| 2693 | |
| 2694 | /* Is the page fully outside i_size? (truncate in progress) */ |
| 2695 | offset = i_size & (PAGE_CACHE_SIZE-1); |
| 2696 | if (page->index >= end_index+1 || !offset) { |
| 2697 | /* |
| 2698 | * The page may have dirty, unmapped buffers. For example, |
| 2699 | * they may have been added in ext3_writepage(). Make them |
| 2700 | * freeable here, so the page does not leak. |
| 2701 | */ |
| 2702 | #if 0 |
| 2703 | /* Not really sure about this - do we need this ? */ |
| 2704 | if (page->mapping->a_ops->invalidatepage) |
| 2705 | page->mapping->a_ops->invalidatepage(page, offset); |
| 2706 | #endif |
| 2707 | unlock_page(page); |
| 2708 | return 0; /* don't care */ |
| 2709 | } |
| 2710 | |
| 2711 | /* |
| 2712 | * The page straddles i_size. It must be zeroed out on each and every |
| 2713 | * writepage invocation because it may be mmapped. "A file is mapped |
| 2714 | * in multiples of the page size. For a file that is not a multiple of |
| 2715 | * the page size, the remaining memory is zeroed when mapped, and |
| 2716 | * writes to that region are not written out to the file." |
| 2717 | */ |
| 2718 | zero_user_segment(page, offset, PAGE_CACHE_SIZE); |
| 2719 | out: |
| 2720 | ret = mpage_writepage(page, get_block, wbc); |
| 2721 | if (ret == -EAGAIN) |
| 2722 | ret = __block_write_full_page(inode, page, get_block, wbc, |
| 2723 | end_buffer_async_write); |
| 2724 | return ret; |
| 2725 | } |
| 2726 | EXPORT_SYMBOL(nobh_writepage); |
| 2727 | |
| 2728 | int nobh_truncate_page(struct address_space *mapping, |
| 2729 | loff_t from, get_block_t *get_block) |
| 2730 | { |
| 2731 | pgoff_t index = from >> PAGE_CACHE_SHIFT; |
| 2732 | unsigned offset = from & (PAGE_CACHE_SIZE-1); |
| 2733 | unsigned blocksize; |
| 2734 | sector_t iblock; |
| 2735 | unsigned length, pos; |
| 2736 | struct inode *inode = mapping->host; |
| 2737 | struct page *page; |
| 2738 | struct buffer_head map_bh; |
| 2739 | int err; |
| 2740 | |
| 2741 | blocksize = 1 << inode->i_blkbits; |
| 2742 | length = offset & (blocksize - 1); |
| 2743 | |
| 2744 | /* Block boundary? Nothing to do */ |
| 2745 | if (!length) |
| 2746 | return 0; |
| 2747 | |
| 2748 | length = blocksize - length; |
| 2749 | iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits); |
| 2750 | |
| 2751 | page = grab_cache_page(mapping, index); |
| 2752 | err = -ENOMEM; |
| 2753 | if (!page) |
| 2754 | goto out; |
| 2755 | |
| 2756 | if (page_has_buffers(page)) { |
| 2757 | has_buffers: |
| 2758 | unlock_page(page); |
| 2759 | page_cache_release(page); |
| 2760 | return block_truncate_page(mapping, from, get_block); |
| 2761 | } |
| 2762 | |
| 2763 | /* Find the buffer that contains "offset" */ |
| 2764 | pos = blocksize; |
| 2765 | while (offset >= pos) { |
| 2766 | iblock++; |
| 2767 | pos += blocksize; |
| 2768 | } |
| 2769 | |
| 2770 | map_bh.b_size = blocksize; |
| 2771 | map_bh.b_state = 0; |
| 2772 | err = get_block(inode, iblock, &map_bh, 0); |
| 2773 | if (err) |
| 2774 | goto unlock; |
| 2775 | /* unmapped? It's a hole - nothing to do */ |
| 2776 | if (!buffer_mapped(&map_bh)) |
| 2777 | goto unlock; |
| 2778 | |
| 2779 | /* Ok, it's mapped. Make sure it's up-to-date */ |
| 2780 | if (!PageUptodate(page)) { |
| 2781 | err = mapping->a_ops->readpage(NULL, page); |
| 2782 | if (err) { |
| 2783 | page_cache_release(page); |
| 2784 | goto out; |
| 2785 | } |
| 2786 | lock_page(page); |
| 2787 | if (!PageUptodate(page)) { |
| 2788 | err = -EIO; |
| 2789 | goto unlock; |
| 2790 | } |
| 2791 | if (page_has_buffers(page)) |
| 2792 | goto has_buffers; |
| 2793 | } |
| 2794 | zero_user(page, offset, length); |
| 2795 | set_page_dirty(page); |
| 2796 | err = 0; |
| 2797 | |
| 2798 | unlock: |
| 2799 | unlock_page(page); |
| 2800 | page_cache_release(page); |
| 2801 | out: |
| 2802 | return err; |
| 2803 | } |
| 2804 | EXPORT_SYMBOL(nobh_truncate_page); |
| 2805 | |
| 2806 | int block_truncate_page(struct address_space *mapping, |
| 2807 | loff_t from, get_block_t *get_block) |
| 2808 | { |
| 2809 | pgoff_t index = from >> PAGE_CACHE_SHIFT; |
| 2810 | unsigned offset = from & (PAGE_CACHE_SIZE-1); |
| 2811 | unsigned blocksize; |
| 2812 | sector_t iblock; |
| 2813 | unsigned length, pos; |
| 2814 | struct inode *inode = mapping->host; |
| 2815 | struct page *page; |
| 2816 | struct buffer_head *bh; |
| 2817 | int err; |
| 2818 | |
| 2819 | blocksize = 1 << inode->i_blkbits; |
| 2820 | length = offset & (blocksize - 1); |
| 2821 | |
| 2822 | /* Block boundary? Nothing to do */ |
| 2823 | if (!length) |
| 2824 | return 0; |
| 2825 | |
| 2826 | length = blocksize - length; |
| 2827 | iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits); |
| 2828 | |
| 2829 | page = grab_cache_page(mapping, index); |
| 2830 | err = -ENOMEM; |
| 2831 | if (!page) |
| 2832 | goto out; |
| 2833 | |
| 2834 | if (!page_has_buffers(page)) |
| 2835 | create_empty_buffers(page, blocksize, 0); |
| 2836 | |
| 2837 | /* Find the buffer that contains "offset" */ |
| 2838 | bh = page_buffers(page); |
| 2839 | pos = blocksize; |
| 2840 | while (offset >= pos) { |
| 2841 | bh = bh->b_this_page; |
| 2842 | iblock++; |
| 2843 | pos += blocksize; |
| 2844 | } |
| 2845 | |
| 2846 | err = 0; |
| 2847 | if (!buffer_mapped(bh)) { |
| 2848 | WARN_ON(bh->b_size != blocksize); |
| 2849 | err = get_block(inode, iblock, bh, 0); |
| 2850 | if (err) |
| 2851 | goto unlock; |
| 2852 | /* unmapped? It's a hole - nothing to do */ |
| 2853 | if (!buffer_mapped(bh)) |
| 2854 | goto unlock; |
| 2855 | } |
| 2856 | |
| 2857 | /* Ok, it's mapped. Make sure it's up-to-date */ |
| 2858 | if (PageUptodate(page)) |
| 2859 | set_buffer_uptodate(bh); |
| 2860 | |
| 2861 | if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) { |
| 2862 | err = -EIO; |
| 2863 | ll_rw_block(READ, 1, &bh); |
| 2864 | wait_on_buffer(bh); |
| 2865 | /* Uhhuh. Read error. Complain and punt. */ |
| 2866 | if (!buffer_uptodate(bh)) |
| 2867 | goto unlock; |
| 2868 | } |
| 2869 | |
| 2870 | zero_user(page, offset, length); |
| 2871 | mark_buffer_dirty(bh); |
| 2872 | err = 0; |
| 2873 | |
| 2874 | unlock: |
| 2875 | unlock_page(page); |
| 2876 | page_cache_release(page); |
| 2877 | out: |
| 2878 | return err; |
| 2879 | } |
| 2880 | EXPORT_SYMBOL(block_truncate_page); |
| 2881 | |
| 2882 | /* |
| 2883 | * The generic ->writepage function for buffer-backed address_spaces |
| 2884 | */ |
| 2885 | int block_write_full_page(struct page *page, get_block_t *get_block, |
| 2886 | struct writeback_control *wbc) |
| 2887 | { |
| 2888 | struct inode * const inode = page->mapping->host; |
| 2889 | loff_t i_size = i_size_read(inode); |
| 2890 | const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT; |
| 2891 | unsigned offset; |
| 2892 | |
| 2893 | /* Is the page fully inside i_size? */ |
| 2894 | if (page->index < end_index) |
| 2895 | return __block_write_full_page(inode, page, get_block, wbc, |
| 2896 | end_buffer_async_write); |
| 2897 | |
| 2898 | /* Is the page fully outside i_size? (truncate in progress) */ |
| 2899 | offset = i_size & (PAGE_CACHE_SIZE-1); |
| 2900 | if (page->index >= end_index+1 || !offset) { |
| 2901 | /* |
| 2902 | * The page may have dirty, unmapped buffers. For example, |
| 2903 | * they may have been added in ext3_writepage(). Make them |
| 2904 | * freeable here, so the page does not leak. |
| 2905 | */ |
| 2906 | do_invalidatepage(page, 0, PAGE_CACHE_SIZE); |
| 2907 | unlock_page(page); |
| 2908 | return 0; /* don't care */ |
| 2909 | } |
| 2910 | |
| 2911 | /* |
| 2912 | * The page straddles i_size. It must be zeroed out on each and every |
| 2913 | * writepage invocation because it may be mmapped. "A file is mapped |
| 2914 | * in multiples of the page size. For a file that is not a multiple of |
| 2915 | * the page size, the remaining memory is zeroed when mapped, and |
| 2916 | * writes to that region are not written out to the file." |
| 2917 | */ |
| 2918 | zero_user_segment(page, offset, PAGE_CACHE_SIZE); |
| 2919 | return __block_write_full_page(inode, page, get_block, wbc, |
| 2920 | end_buffer_async_write); |
| 2921 | } |
| 2922 | EXPORT_SYMBOL(block_write_full_page); |
| 2923 | |
| 2924 | sector_t generic_block_bmap(struct address_space *mapping, sector_t block, |
| 2925 | get_block_t *get_block) |
| 2926 | { |
| 2927 | struct buffer_head tmp; |
| 2928 | struct inode *inode = mapping->host; |
| 2929 | tmp.b_state = 0; |
| 2930 | tmp.b_blocknr = 0; |
| 2931 | tmp.b_size = 1 << inode->i_blkbits; |
| 2932 | get_block(inode, block, &tmp, 0); |
| 2933 | return tmp.b_blocknr; |
| 2934 | } |
| 2935 | EXPORT_SYMBOL(generic_block_bmap); |
| 2936 | |
| 2937 | static void end_bio_bh_io_sync(struct bio *bio, int err) |
| 2938 | { |
| 2939 | struct buffer_head *bh = bio->bi_private; |
| 2940 | |
| 2941 | if (err == -EOPNOTSUPP) { |
| 2942 | set_bit(BIO_EOPNOTSUPP, &bio->bi_flags); |
| 2943 | } |
| 2944 | |
| 2945 | if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags))) |
| 2946 | set_bit(BH_Quiet, &bh->b_state); |
| 2947 | |
| 2948 | bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags)); |
| 2949 | bio_put(bio); |
| 2950 | } |
| 2951 | |
| 2952 | /* |
| 2953 | * This allows us to do IO even on the odd last sectors |
| 2954 | * of a device, even if the block size is some multiple |
| 2955 | * of the physical sector size. |
| 2956 | * |
| 2957 | * We'll just truncate the bio to the size of the device, |
| 2958 | * and clear the end of the buffer head manually. |
| 2959 | * |
| 2960 | * Truly out-of-range accesses will turn into actual IO |
| 2961 | * errors, this only handles the "we need to be able to |
| 2962 | * do IO at the final sector" case. |
| 2963 | */ |
| 2964 | void guard_bio_eod(int rw, struct bio *bio) |
| 2965 | { |
| 2966 | sector_t maxsector; |
| 2967 | struct bio_vec *bvec = &bio->bi_io_vec[bio->bi_vcnt - 1]; |
| 2968 | unsigned truncated_bytes; |
| 2969 | |
| 2970 | maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9; |
| 2971 | if (!maxsector) |
| 2972 | return; |
| 2973 | |
| 2974 | /* |
| 2975 | * If the *whole* IO is past the end of the device, |
| 2976 | * let it through, and the IO layer will turn it into |
| 2977 | * an EIO. |
| 2978 | */ |
| 2979 | if (unlikely(bio->bi_iter.bi_sector >= maxsector)) |
| 2980 | return; |
| 2981 | |
| 2982 | maxsector -= bio->bi_iter.bi_sector; |
| 2983 | if (likely((bio->bi_iter.bi_size >> 9) <= maxsector)) |
| 2984 | return; |
| 2985 | |
| 2986 | /* Uhhuh. We've got a bio that straddles the device size! */ |
| 2987 | truncated_bytes = bio->bi_iter.bi_size - (maxsector << 9); |
| 2988 | |
| 2989 | /* Truncate the bio.. */ |
| 2990 | bio->bi_iter.bi_size -= truncated_bytes; |
| 2991 | bvec->bv_len -= truncated_bytes; |
| 2992 | |
| 2993 | /* ..and clear the end of the buffer for reads */ |
| 2994 | if ((rw & RW_MASK) == READ) { |
| 2995 | zero_user(bvec->bv_page, bvec->bv_offset + bvec->bv_len, |
| 2996 | truncated_bytes); |
| 2997 | } |
| 2998 | } |
| 2999 | |
| 3000 | int _submit_bh(int rw, struct buffer_head *bh, unsigned long bio_flags) |
| 3001 | { |
| 3002 | struct bio *bio; |
| 3003 | int ret = 0; |
| 3004 | |
| 3005 | BUG_ON(!buffer_locked(bh)); |
| 3006 | BUG_ON(!buffer_mapped(bh)); |
| 3007 | BUG_ON(!bh->b_end_io); |
| 3008 | BUG_ON(buffer_delay(bh)); |
| 3009 | BUG_ON(buffer_unwritten(bh)); |
| 3010 | |
| 3011 | /* |
| 3012 | * Only clear out a write error when rewriting |
| 3013 | */ |
| 3014 | if (test_set_buffer_req(bh) && (rw & WRITE)) |
| 3015 | clear_buffer_write_io_error(bh); |
| 3016 | |
| 3017 | /* |
| 3018 | * from here on down, it's all bio -- do the initial mapping, |
| 3019 | * submit_bio -> generic_make_request may further map this bio around |
| 3020 | */ |
| 3021 | bio = bio_alloc(GFP_NOIO, 1); |
| 3022 | |
| 3023 | bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9); |
| 3024 | bio->bi_bdev = bh->b_bdev; |
| 3025 | bio->bi_io_vec[0].bv_page = bh->b_page; |
| 3026 | bio->bi_io_vec[0].bv_len = bh->b_size; |
| 3027 | bio->bi_io_vec[0].bv_offset = bh_offset(bh); |
| 3028 | |
| 3029 | bio->bi_vcnt = 1; |
| 3030 | bio->bi_iter.bi_size = bh->b_size; |
| 3031 | |
| 3032 | bio->bi_end_io = end_bio_bh_io_sync; |
| 3033 | bio->bi_private = bh; |
| 3034 | bio->bi_flags |= bio_flags; |
| 3035 | |
| 3036 | /* Take care of bh's that straddle the end of the device */ |
| 3037 | guard_bio_eod(rw, bio); |
| 3038 | |
| 3039 | if (buffer_meta(bh)) |
| 3040 | rw |= REQ_META; |
| 3041 | if (buffer_prio(bh)) |
| 3042 | rw |= REQ_PRIO; |
| 3043 | |
| 3044 | bio_get(bio); |
| 3045 | submit_bio(rw, bio); |
| 3046 | |
| 3047 | if (bio_flagged(bio, BIO_EOPNOTSUPP)) |
| 3048 | ret = -EOPNOTSUPP; |
| 3049 | |
| 3050 | bio_put(bio); |
| 3051 | return ret; |
| 3052 | } |
| 3053 | EXPORT_SYMBOL_GPL(_submit_bh); |
| 3054 | |
| 3055 | int submit_bh(int rw, struct buffer_head *bh) |
| 3056 | { |
| 3057 | return _submit_bh(rw, bh, 0); |
| 3058 | } |
| 3059 | EXPORT_SYMBOL(submit_bh); |
| 3060 | |
| 3061 | /** |
| 3062 | * ll_rw_block: low-level access to block devices (DEPRECATED) |
| 3063 | * @rw: whether to %READ or %WRITE or maybe %READA (readahead) |
| 3064 | * @nr: number of &struct buffer_heads in the array |
| 3065 | * @bhs: array of pointers to &struct buffer_head |
| 3066 | * |
| 3067 | * ll_rw_block() takes an array of pointers to &struct buffer_heads, and |
| 3068 | * requests an I/O operation on them, either a %READ or a %WRITE. The third |
| 3069 | * %READA option is described in the documentation for generic_make_request() |
| 3070 | * which ll_rw_block() calls. |
| 3071 | * |
| 3072 | * This function drops any buffer that it cannot get a lock on (with the |
| 3073 | * BH_Lock state bit), any buffer that appears to be clean when doing a write |
| 3074 | * request, and any buffer that appears to be up-to-date when doing read |
| 3075 | * request. Further it marks as clean buffers that are processed for |
| 3076 | * writing (the buffer cache won't assume that they are actually clean |
| 3077 | * until the buffer gets unlocked). |
| 3078 | * |
| 3079 | * ll_rw_block sets b_end_io to simple completion handler that marks |
| 3080 | * the buffer up-to-date (if appropriate), unlocks the buffer and wakes |
| 3081 | * any waiters. |
| 3082 | * |
| 3083 | * All of the buffers must be for the same device, and must also be a |
| 3084 | * multiple of the current approved size for the device. |
| 3085 | */ |
| 3086 | void ll_rw_block(int rw, int nr, struct buffer_head *bhs[]) |
| 3087 | { |
| 3088 | int i; |
| 3089 | |
| 3090 | for (i = 0; i < nr; i++) { |
| 3091 | struct buffer_head *bh = bhs[i]; |
| 3092 | |
| 3093 | if (!trylock_buffer(bh)) |
| 3094 | continue; |
| 3095 | if (rw == WRITE) { |
| 3096 | if (test_clear_buffer_dirty(bh)) { |
| 3097 | bh->b_end_io = end_buffer_write_sync; |
| 3098 | get_bh(bh); |
| 3099 | submit_bh(WRITE, bh); |
| 3100 | continue; |
| 3101 | } |
| 3102 | } else { |
| 3103 | if (!buffer_uptodate(bh)) { |
| 3104 | bh->b_end_io = end_buffer_read_sync; |
| 3105 | get_bh(bh); |
| 3106 | submit_bh(rw, bh); |
| 3107 | continue; |
| 3108 | } |
| 3109 | } |
| 3110 | unlock_buffer(bh); |
| 3111 | } |
| 3112 | } |
| 3113 | EXPORT_SYMBOL(ll_rw_block); |
| 3114 | |
| 3115 | void write_dirty_buffer(struct buffer_head *bh, int rw) |
| 3116 | { |
| 3117 | lock_buffer(bh); |
| 3118 | if (!test_clear_buffer_dirty(bh)) { |
| 3119 | unlock_buffer(bh); |
| 3120 | return; |
| 3121 | } |
| 3122 | bh->b_end_io = end_buffer_write_sync; |
| 3123 | get_bh(bh); |
| 3124 | submit_bh(rw, bh); |
| 3125 | } |
| 3126 | EXPORT_SYMBOL(write_dirty_buffer); |
| 3127 | |
| 3128 | /* |
| 3129 | * For a data-integrity writeout, we need to wait upon any in-progress I/O |
| 3130 | * and then start new I/O and then wait upon it. The caller must have a ref on |
| 3131 | * the buffer_head. |
| 3132 | */ |
| 3133 | int __sync_dirty_buffer(struct buffer_head *bh, int rw) |
| 3134 | { |
| 3135 | int ret = 0; |
| 3136 | |
| 3137 | WARN_ON(atomic_read(&bh->b_count) < 1); |
| 3138 | lock_buffer(bh); |
| 3139 | if (test_clear_buffer_dirty(bh)) { |
| 3140 | get_bh(bh); |
| 3141 | bh->b_end_io = end_buffer_write_sync; |
| 3142 | ret = submit_bh(rw, bh); |
| 3143 | wait_on_buffer(bh); |
| 3144 | if (!ret && !buffer_uptodate(bh)) |
| 3145 | ret = -EIO; |
| 3146 | } else { |
| 3147 | unlock_buffer(bh); |
| 3148 | } |
| 3149 | return ret; |
| 3150 | } |
| 3151 | EXPORT_SYMBOL(__sync_dirty_buffer); |
| 3152 | |
| 3153 | int sync_dirty_buffer(struct buffer_head *bh) |
| 3154 | { |
| 3155 | return __sync_dirty_buffer(bh, WRITE_SYNC); |
| 3156 | } |
| 3157 | EXPORT_SYMBOL(sync_dirty_buffer); |
| 3158 | |
| 3159 | /* |
| 3160 | * try_to_free_buffers() checks if all the buffers on this particular page |
| 3161 | * are unused, and releases them if so. |
| 3162 | * |
| 3163 | * Exclusion against try_to_free_buffers may be obtained by either |
| 3164 | * locking the page or by holding its mapping's private_lock. |
| 3165 | * |
| 3166 | * If the page is dirty but all the buffers are clean then we need to |
| 3167 | * be sure to mark the page clean as well. This is because the page |
| 3168 | * may be against a block device, and a later reattachment of buffers |
| 3169 | * to a dirty page will set *all* buffers dirty. Which would corrupt |
| 3170 | * filesystem data on the same device. |
| 3171 | * |
| 3172 | * The same applies to regular filesystem pages: if all the buffers are |
| 3173 | * clean then we set the page clean and proceed. To do that, we require |
| 3174 | * total exclusion from __set_page_dirty_buffers(). That is obtained with |
| 3175 | * private_lock. |
| 3176 | * |
| 3177 | * try_to_free_buffers() is non-blocking. |
| 3178 | */ |
| 3179 | static inline int buffer_busy(struct buffer_head *bh) |
| 3180 | { |
| 3181 | return atomic_read(&bh->b_count) | |
| 3182 | (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock))); |
| 3183 | } |
| 3184 | |
| 3185 | static int |
| 3186 | drop_buffers(struct page *page, struct buffer_head **buffers_to_free) |
| 3187 | { |
| 3188 | struct buffer_head *head = page_buffers(page); |
| 3189 | struct buffer_head *bh; |
| 3190 | |
| 3191 | bh = head; |
| 3192 | do { |
| 3193 | if (buffer_write_io_error(bh) && page->mapping) |
| 3194 | set_bit(AS_EIO, &page->mapping->flags); |
| 3195 | if (buffer_busy(bh)) |
| 3196 | goto failed; |
| 3197 | bh = bh->b_this_page; |
| 3198 | } while (bh != head); |
| 3199 | |
| 3200 | do { |
| 3201 | struct buffer_head *next = bh->b_this_page; |
| 3202 | |
| 3203 | if (bh->b_assoc_map) |
| 3204 | __remove_assoc_queue(bh); |
| 3205 | bh = next; |
| 3206 | } while (bh != head); |
| 3207 | *buffers_to_free = head; |
| 3208 | __clear_page_buffers(page); |
| 3209 | return 1; |
| 3210 | failed: |
| 3211 | return 0; |
| 3212 | } |
| 3213 | |
| 3214 | int try_to_free_buffers(struct page *page) |
| 3215 | { |
| 3216 | struct address_space * const mapping = page->mapping; |
| 3217 | struct buffer_head *buffers_to_free = NULL; |
| 3218 | int ret = 0; |
| 3219 | |
| 3220 | BUG_ON(!PageLocked(page)); |
| 3221 | if (PageWriteback(page)) |
| 3222 | return 0; |
| 3223 | |
| 3224 | if (mapping == NULL) { /* can this still happen? */ |
| 3225 | ret = drop_buffers(page, &buffers_to_free); |
| 3226 | goto out; |
| 3227 | } |
| 3228 | |
| 3229 | spin_lock(&mapping->private_lock); |
| 3230 | ret = drop_buffers(page, &buffers_to_free); |
| 3231 | |
| 3232 | /* |
| 3233 | * If the filesystem writes its buffers by hand (eg ext3) |
| 3234 | * then we can have clean buffers against a dirty page. We |
| 3235 | * clean the page here; otherwise the VM will never notice |
| 3236 | * that the filesystem did any IO at all. |
| 3237 | * |
| 3238 | * Also, during truncate, discard_buffer will have marked all |
| 3239 | * the page's buffers clean. We discover that here and clean |
| 3240 | * the page also. |
| 3241 | * |
| 3242 | * private_lock must be held over this entire operation in order |
| 3243 | * to synchronise against __set_page_dirty_buffers and prevent the |
| 3244 | * dirty bit from being lost. |
| 3245 | */ |
| 3246 | if (ret) |
| 3247 | cancel_dirty_page(page, PAGE_CACHE_SIZE); |
| 3248 | spin_unlock(&mapping->private_lock); |
| 3249 | out: |
| 3250 | if (buffers_to_free) { |
| 3251 | struct buffer_head *bh = buffers_to_free; |
| 3252 | |
| 3253 | do { |
| 3254 | struct buffer_head *next = bh->b_this_page; |
| 3255 | free_buffer_head(bh); |
| 3256 | bh = next; |
| 3257 | } while (bh != buffers_to_free); |
| 3258 | } |
| 3259 | return ret; |
| 3260 | } |
| 3261 | EXPORT_SYMBOL(try_to_free_buffers); |
| 3262 | |
| 3263 | /* |
| 3264 | * There are no bdflush tunables left. But distributions are |
| 3265 | * still running obsolete flush daemons, so we terminate them here. |
| 3266 | * |
| 3267 | * Use of bdflush() is deprecated and will be removed in a future kernel. |
| 3268 | * The `flush-X' kernel threads fully replace bdflush daemons and this call. |
| 3269 | */ |
| 3270 | SYSCALL_DEFINE2(bdflush, int, func, long, data) |
| 3271 | { |
| 3272 | static int msg_count; |
| 3273 | |
| 3274 | if (!capable(CAP_SYS_ADMIN)) |
| 3275 | return -EPERM; |
| 3276 | |
| 3277 | if (msg_count < 5) { |
| 3278 | msg_count++; |
| 3279 | printk(KERN_INFO |
| 3280 | "warning: process `%s' used the obsolete bdflush" |
| 3281 | " system call\n", current->comm); |
| 3282 | printk(KERN_INFO "Fix your initscripts?\n"); |
| 3283 | } |
| 3284 | |
| 3285 | if (func == 1) |
| 3286 | do_exit(0); |
| 3287 | return 0; |
| 3288 | } |
| 3289 | |
| 3290 | /* |
| 3291 | * Buffer-head allocation |
| 3292 | */ |
| 3293 | static struct kmem_cache *bh_cachep __read_mostly; |
| 3294 | |
| 3295 | /* |
| 3296 | * Once the number of bh's in the machine exceeds this level, we start |
| 3297 | * stripping them in writeback. |
| 3298 | */ |
| 3299 | static unsigned long max_buffer_heads; |
| 3300 | |
| 3301 | int buffer_heads_over_limit; |
| 3302 | |
| 3303 | struct bh_accounting { |
| 3304 | int nr; /* Number of live bh's */ |
| 3305 | int ratelimit; /* Limit cacheline bouncing */ |
| 3306 | }; |
| 3307 | |
| 3308 | static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0}; |
| 3309 | |
| 3310 | static void recalc_bh_state(void) |
| 3311 | { |
| 3312 | int i; |
| 3313 | int tot = 0; |
| 3314 | |
| 3315 | if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096) |
| 3316 | return; |
| 3317 | __this_cpu_write(bh_accounting.ratelimit, 0); |
| 3318 | for_each_online_cpu(i) |
| 3319 | tot += per_cpu(bh_accounting, i).nr; |
| 3320 | buffer_heads_over_limit = (tot > max_buffer_heads); |
| 3321 | } |
| 3322 | |
| 3323 | struct buffer_head *alloc_buffer_head(gfp_t gfp_flags) |
| 3324 | { |
| 3325 | struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags); |
| 3326 | if (ret) { |
| 3327 | INIT_LIST_HEAD(&ret->b_assoc_buffers); |
| 3328 | preempt_disable(); |
| 3329 | __this_cpu_inc(bh_accounting.nr); |
| 3330 | recalc_bh_state(); |
| 3331 | preempt_enable(); |
| 3332 | } |
| 3333 | return ret; |
| 3334 | } |
| 3335 | EXPORT_SYMBOL(alloc_buffer_head); |
| 3336 | |
| 3337 | void free_buffer_head(struct buffer_head *bh) |
| 3338 | { |
| 3339 | BUG_ON(!list_empty(&bh->b_assoc_buffers)); |
| 3340 | kmem_cache_free(bh_cachep, bh); |
| 3341 | preempt_disable(); |
| 3342 | __this_cpu_dec(bh_accounting.nr); |
| 3343 | recalc_bh_state(); |
| 3344 | preempt_enable(); |
| 3345 | } |
| 3346 | EXPORT_SYMBOL(free_buffer_head); |
| 3347 | |
| 3348 | static void buffer_exit_cpu(int cpu) |
| 3349 | { |
| 3350 | int i; |
| 3351 | struct bh_lru *b = &per_cpu(bh_lrus, cpu); |
| 3352 | |
| 3353 | for (i = 0; i < BH_LRU_SIZE; i++) { |
| 3354 | brelse(b->bhs[i]); |
| 3355 | b->bhs[i] = NULL; |
| 3356 | } |
| 3357 | this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr); |
| 3358 | per_cpu(bh_accounting, cpu).nr = 0; |
| 3359 | } |
| 3360 | |
| 3361 | static int buffer_cpu_notify(struct notifier_block *self, |
| 3362 | unsigned long action, void *hcpu) |
| 3363 | { |
| 3364 | if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) |
| 3365 | buffer_exit_cpu((unsigned long)hcpu); |
| 3366 | return NOTIFY_OK; |
| 3367 | } |
| 3368 | |
| 3369 | /** |
| 3370 | * bh_uptodate_or_lock - Test whether the buffer is uptodate |
| 3371 | * @bh: struct buffer_head |
| 3372 | * |
| 3373 | * Return true if the buffer is up-to-date and false, |
| 3374 | * with the buffer locked, if not. |
| 3375 | */ |
| 3376 | int bh_uptodate_or_lock(struct buffer_head *bh) |
| 3377 | { |
| 3378 | if (!buffer_uptodate(bh)) { |
| 3379 | lock_buffer(bh); |
| 3380 | if (!buffer_uptodate(bh)) |
| 3381 | return 0; |
| 3382 | unlock_buffer(bh); |
| 3383 | } |
| 3384 | return 1; |
| 3385 | } |
| 3386 | EXPORT_SYMBOL(bh_uptodate_or_lock); |
| 3387 | |
| 3388 | /** |
| 3389 | * bh_submit_read - Submit a locked buffer for reading |
| 3390 | * @bh: struct buffer_head |
| 3391 | * |
| 3392 | * Returns zero on success and -EIO on error. |
| 3393 | */ |
| 3394 | int bh_submit_read(struct buffer_head *bh) |
| 3395 | { |
| 3396 | BUG_ON(!buffer_locked(bh)); |
| 3397 | |
| 3398 | if (buffer_uptodate(bh)) { |
| 3399 | unlock_buffer(bh); |
| 3400 | return 0; |
| 3401 | } |
| 3402 | |
| 3403 | get_bh(bh); |
| 3404 | bh->b_end_io = end_buffer_read_sync; |
| 3405 | submit_bh(READ, bh); |
| 3406 | wait_on_buffer(bh); |
| 3407 | if (buffer_uptodate(bh)) |
| 3408 | return 0; |
| 3409 | return -EIO; |
| 3410 | } |
| 3411 | EXPORT_SYMBOL(bh_submit_read); |
| 3412 | |
| 3413 | void __init buffer_init(void) |
| 3414 | { |
| 3415 | unsigned long nrpages; |
| 3416 | |
| 3417 | bh_cachep = kmem_cache_create("buffer_head", |
| 3418 | sizeof(struct buffer_head), 0, |
| 3419 | (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC| |
| 3420 | SLAB_MEM_SPREAD), |
| 3421 | NULL); |
| 3422 | |
| 3423 | /* |
| 3424 | * Limit the bh occupancy to 10% of ZONE_NORMAL |
| 3425 | */ |
| 3426 | nrpages = (nr_free_buffer_pages() * 10) / 100; |
| 3427 | max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head)); |
| 3428 | hotcpu_notifier(buffer_cpu_notify, 0); |
| 3429 | } |