buffer.c 89.6 KB
Newer Older
L
Linus Torvalds 已提交
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
/*
 *  linux/fs/buffer.c
 *
 *  Copyright (C) 1991, 1992, 2002  Linus Torvalds
 */

/*
 * Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95
 *
 * Removed a lot of unnecessary code and simplified things now that
 * the buffer cache isn't our primary cache - Andrew Tridgell 12/96
 *
 * Speed up hash, lru, and free list operations.  Use gfp() for allocating
 * hash table, use SLAB cache for buffer heads. SMP threading.  -DaveM
 *
 * Added 32k buffer block sizes - these are required older ARM systems. - RMK
 *
 * async buffer flushing, 1999 Andrea Arcangeli <andrea@suse.de>
 */

#include <linux/kernel.h>
#include <linux/syscalls.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/percpu.h>
#include <linux/slab.h>
27
#include <linux/capability.h>
L
Linus Torvalds 已提交
28 29 30 31
#include <linux/blkdev.h>
#include <linux/file.h>
#include <linux/quotaops.h>
#include <linux/highmem.h>
32
#include <linux/export.h>
33
#include <linux/backing-dev.h>
L
Linus Torvalds 已提交
34 35 36 37
#include <linux/writeback.h>
#include <linux/hash.h>
#include <linux/suspend.h>
#include <linux/buffer_head.h>
38
#include <linux/task_io_accounting_ops.h>
L
Linus Torvalds 已提交
39 40 41 42 43
#include <linux/bio.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/bitops.h>
#include <linux/mpage.h>
I
Ingo Molnar 已提交
44
#include <linux/bit_spinlock.h>
45
#include <trace/events/block.h>
L
Linus Torvalds 已提交
46 47

static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
48 49 50
static int submit_bh_wbc(int rw, struct buffer_head *bh,
			 unsigned long bio_flags,
			 struct writeback_control *wbc);
L
Linus Torvalds 已提交
51 52 53

#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)

54
void init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private)
L
Linus Torvalds 已提交
55 56 57 58
{
	bh->b_end_io = handler;
	bh->b_private = private;
}
59
EXPORT_SYMBOL(init_buffer);
L
Linus Torvalds 已提交
60

61 62
inline void touch_buffer(struct buffer_head *bh)
{
63
	trace_block_touch_buffer(bh);
64 65 66 67
	mark_page_accessed(bh->b_page);
}
EXPORT_SYMBOL(touch_buffer);

68
void __lock_buffer(struct buffer_head *bh)
L
Linus Torvalds 已提交
69
{
70
	wait_on_bit_lock_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
L
Linus Torvalds 已提交
71 72 73
}
EXPORT_SYMBOL(__lock_buffer);

74
void unlock_buffer(struct buffer_head *bh)
L
Linus Torvalds 已提交
75
{
N
Nick Piggin 已提交
76
	clear_bit_unlock(BH_Lock, &bh->b_state);
77
	smp_mb__after_atomic();
L
Linus Torvalds 已提交
78 79
	wake_up_bit(&bh->b_state, BH_Lock);
}
80
EXPORT_SYMBOL(unlock_buffer);
L
Linus Torvalds 已提交
81

82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115
/*
 * Returns if the page has dirty or writeback buffers. If all the buffers
 * are unlocked and clean then the PageDirty information is stale. If
 * any of the pages are locked, it is assumed they are locked for IO.
 */
void buffer_check_dirty_writeback(struct page *page,
				     bool *dirty, bool *writeback)
{
	struct buffer_head *head, *bh;
	*dirty = false;
	*writeback = false;

	BUG_ON(!PageLocked(page));

	if (!page_has_buffers(page))
		return;

	if (PageWriteback(page))
		*writeback = true;

	head = page_buffers(page);
	bh = head;
	do {
		if (buffer_locked(bh))
			*writeback = true;

		if (buffer_dirty(bh))
			*dirty = true;

		bh = bh->b_this_page;
	} while (bh != head);
}
EXPORT_SYMBOL(buffer_check_dirty_writeback);

L
Linus Torvalds 已提交
116 117 118 119 120 121 122
/*
 * Block until a buffer comes unlocked.  This doesn't stop it
 * from becoming locked again - you have to lock it yourself
 * if you want to preserve its state.
 */
void __wait_on_buffer(struct buffer_head * bh)
{
123
	wait_on_bit_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
L
Linus Torvalds 已提交
124
}
125
EXPORT_SYMBOL(__wait_on_buffer);
L
Linus Torvalds 已提交
126 127 128 129 130

static void
__clear_page_buffers(struct page *page)
{
	ClearPagePrivate(page);
H
Hugh Dickins 已提交
131
	set_page_private(page, 0);
L
Linus Torvalds 已提交
132 133 134
	page_cache_release(page);
}

135
static void buffer_io_error(struct buffer_head *bh, char *msg)
L
Linus Torvalds 已提交
136 137
{
	char b[BDEVNAME_SIZE];
138 139 140 141

	if (!test_bit(BH_Quiet, &bh->b_state))
		printk_ratelimited(KERN_ERR
			"Buffer I/O error on dev %s, logical block %llu%s\n",
L
Linus Torvalds 已提交
142
			bdevname(bh->b_bdev, b),
143
			(unsigned long long)bh->b_blocknr, msg);
L
Linus Torvalds 已提交
144 145 146
}

/*
147 148 149 150 151 152
 * End-of-IO handler helper function which does not touch the bh after
 * unlocking it.
 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
 * a race there is benign: unlock_buffer() only use the bh's address for
 * hashing after unlocking the buffer, so it doesn't actually touch the bh
 * itself.
L
Linus Torvalds 已提交
153
 */
154
static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
L
Linus Torvalds 已提交
155 156 157 158 159 160 161 162
{
	if (uptodate) {
		set_buffer_uptodate(bh);
	} else {
		/* This happens, due to failed READA attempts. */
		clear_buffer_uptodate(bh);
	}
	unlock_buffer(bh);
163 164 165 166 167 168 169 170 171
}

/*
 * Default synchronous end-of-IO handler..  Just mark it up-to-date and
 * unlock the buffer. This is what ll_rw_block uses too.
 */
void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
{
	__end_buffer_read_notouch(bh, uptodate);
L
Linus Torvalds 已提交
172 173
	put_bh(bh);
}
174
EXPORT_SYMBOL(end_buffer_read_sync);
L
Linus Torvalds 已提交
175 176 177 178 179 180

void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
{
	if (uptodate) {
		set_buffer_uptodate(bh);
	} else {
181
		buffer_io_error(bh, ", lost sync page write");
L
Linus Torvalds 已提交
182 183 184 185 186 187
		set_buffer_write_io_error(bh);
		clear_buffer_uptodate(bh);
	}
	unlock_buffer(bh);
	put_bh(bh);
}
188
EXPORT_SYMBOL(end_buffer_write_sync);
L
Linus Torvalds 已提交
189 190 191 192 193 194 195 196 197 198 199 200 201

/*
 * Various filesystems appear to want __find_get_block to be non-blocking.
 * But it's the page lock which protects the buffers.  To get around this,
 * we get exclusion from try_to_free_buffers with the blockdev mapping's
 * private_lock.
 *
 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention
 * may be quite high.  This code could TryLock the page, and if that
 * succeeds, there is no need to take private_lock. (But if
 * private_lock is contended then so is mapping->tree_lock).
 */
static struct buffer_head *
202
__find_get_block_slow(struct block_device *bdev, sector_t block)
L
Linus Torvalds 已提交
203 204 205 206 207 208 209 210 211 212 213
{
	struct inode *bd_inode = bdev->bd_inode;
	struct address_space *bd_mapping = bd_inode->i_mapping;
	struct buffer_head *ret = NULL;
	pgoff_t index;
	struct buffer_head *bh;
	struct buffer_head *head;
	struct page *page;
	int all_mapped = 1;

	index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits);
214
	page = find_get_page_flags(bd_mapping, index, FGP_ACCESSED);
L
Linus Torvalds 已提交
215 216 217 218 219 220 221 222 223
	if (!page)
		goto out;

	spin_lock(&bd_mapping->private_lock);
	if (!page_has_buffers(page))
		goto out_unlock;
	head = page_buffers(page);
	bh = head;
	do {
224 225 226
		if (!buffer_mapped(bh))
			all_mapped = 0;
		else if (bh->b_blocknr == block) {
L
Linus Torvalds 已提交
227 228 229 230 231 232 233 234 235 236 237 238 239
			ret = bh;
			get_bh(bh);
			goto out_unlock;
		}
		bh = bh->b_this_page;
	} while (bh != head);

	/* we might be here because some of the buffers on this page are
	 * not mapped.  This is due to various races between
	 * file io on the block device and getblk.  It gets dealt with
	 * elsewhere, don't buffer_error if we had some unmapped buffers
	 */
	if (all_mapped) {
240 241
		char b[BDEVNAME_SIZE];

L
Linus Torvalds 已提交
242 243
		printk("__find_get_block_slow() failed. "
			"block=%llu, b_blocknr=%llu\n",
244 245 246 247
			(unsigned long long)block,
			(unsigned long long)bh->b_blocknr);
		printk("b_state=0x%08lx, b_size=%zu\n",
			bh->b_state, bh->b_size);
248 249
		printk("device %s blocksize: %d\n", bdevname(bdev, b),
			1 << bd_inode->i_blkbits);
L
Linus Torvalds 已提交
250 251 252 253 254 255 256 257 258
	}
out_unlock:
	spin_unlock(&bd_mapping->private_lock);
	page_cache_release(page);
out:
	return ret;
}

/*
259
 * Kick the writeback threads then try to free up some ZONE_NORMAL memory.
L
Linus Torvalds 已提交
260 261 262
 */
static void free_more_memory(void)
{
263
	struct zone *zone;
264
	int nid;
L
Linus Torvalds 已提交
265

266
	wakeup_flusher_threads(1024, WB_REASON_FREE_MORE_MEM);
L
Linus Torvalds 已提交
267 268
	yield();

269
	for_each_online_node(nid) {
270 271 272 273
		(void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS),
						gfp_zone(GFP_NOFS), NULL,
						&zone);
		if (zone)
274
			try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0,
275
						GFP_NOFS, NULL);
L
Linus Torvalds 已提交
276 277 278 279 280 281 282 283 284 285
	}
}

/*
 * I/O completion handler for block_read_full_page() - pages
 * which come unlocked at the end of I/O.
 */
static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
{
	unsigned long flags;
286
	struct buffer_head *first;
L
Linus Torvalds 已提交
287 288 289 290 291 292 293 294 295 296 297
	struct buffer_head *tmp;
	struct page *page;
	int page_uptodate = 1;

	BUG_ON(!buffer_async_read(bh));

	page = bh->b_page;
	if (uptodate) {
		set_buffer_uptodate(bh);
	} else {
		clear_buffer_uptodate(bh);
298
		buffer_io_error(bh, ", async page read");
L
Linus Torvalds 已提交
299 300 301 302 303 304 305 306
		SetPageError(page);
	}

	/*
	 * Be _very_ careful from here on. Bad things can happen if
	 * two buffer heads end IO at almost the same time and both
	 * decide that the page is now completely done.
	 */
307 308 309
	first = page_buffers(page);
	local_irq_save(flags);
	bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
L
Linus Torvalds 已提交
310 311 312 313 314 315 316 317 318 319 320 321
	clear_buffer_async_read(bh);
	unlock_buffer(bh);
	tmp = bh;
	do {
		if (!buffer_uptodate(tmp))
			page_uptodate = 0;
		if (buffer_async_read(tmp)) {
			BUG_ON(!buffer_locked(tmp));
			goto still_busy;
		}
		tmp = tmp->b_this_page;
	} while (tmp != bh);
322 323
	bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
	local_irq_restore(flags);
L
Linus Torvalds 已提交
324 325 326 327 328 329 330 331 332 333 334

	/*
	 * If none of the buffers had errors and they are all
	 * uptodate then we can set the page uptodate.
	 */
	if (page_uptodate && !PageError(page))
		SetPageUptodate(page);
	unlock_page(page);
	return;

still_busy:
335 336
	bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
	local_irq_restore(flags);
L
Linus Torvalds 已提交
337 338 339 340 341 342 343
	return;
}

/*
 * Completion handler for block_write_full_page() - pages which are unlocked
 * during I/O, and which have PageWriteback cleared upon I/O completion.
 */
344
void end_buffer_async_write(struct buffer_head *bh, int uptodate)
L
Linus Torvalds 已提交
345 346
{
	unsigned long flags;
347
	struct buffer_head *first;
L
Linus Torvalds 已提交
348 349 350 351 352 353 354 355 356
	struct buffer_head *tmp;
	struct page *page;

	BUG_ON(!buffer_async_write(bh));

	page = bh->b_page;
	if (uptodate) {
		set_buffer_uptodate(bh);
	} else {
357
		buffer_io_error(bh, ", lost async page write");
L
Linus Torvalds 已提交
358
		set_bit(AS_EIO, &page->mapping->flags);
359
		set_buffer_write_io_error(bh);
L
Linus Torvalds 已提交
360 361 362 363
		clear_buffer_uptodate(bh);
		SetPageError(page);
	}

364 365 366 367
	first = page_buffers(page);
	local_irq_save(flags);
	bit_spin_lock(BH_Uptodate_Lock, &first->b_state);

L
Linus Torvalds 已提交
368 369 370 371 372 373 374 375 376 377
	clear_buffer_async_write(bh);
	unlock_buffer(bh);
	tmp = bh->b_this_page;
	while (tmp != bh) {
		if (buffer_async_write(tmp)) {
			BUG_ON(!buffer_locked(tmp));
			goto still_busy;
		}
		tmp = tmp->b_this_page;
	}
378 379
	bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
	local_irq_restore(flags);
L
Linus Torvalds 已提交
380 381 382 383
	end_page_writeback(page);
	return;

still_busy:
384 385
	bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
	local_irq_restore(flags);
L
Linus Torvalds 已提交
386 387
	return;
}
388
EXPORT_SYMBOL(end_buffer_async_write);
L
Linus Torvalds 已提交
389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416

/*
 * If a page's buffers are under async readin (end_buffer_async_read
 * completion) then there is a possibility that another thread of
 * control could lock one of the buffers after it has completed
 * but while some of the other buffers have not completed.  This
 * locked buffer would confuse end_buffer_async_read() into not unlocking
 * the page.  So the absence of BH_Async_Read tells end_buffer_async_read()
 * that this buffer is not under async I/O.
 *
 * The page comes unlocked when it has no locked buffer_async buffers
 * left.
 *
 * PageLocked prevents anyone starting new async I/O reads any of
 * the buffers.
 *
 * PageWriteback is used to prevent simultaneous writeout of the same
 * page.
 *
 * PageLocked prevents anyone from starting writeback of a page which is
 * under read I/O (PageWriteback is only ever set against a locked page).
 */
static void mark_buffer_async_read(struct buffer_head *bh)
{
	bh->b_end_io = end_buffer_async_read;
	set_buffer_async_read(bh);
}

417 418
static void mark_buffer_async_write_endio(struct buffer_head *bh,
					  bh_end_io_t *handler)
L
Linus Torvalds 已提交
419
{
420
	bh->b_end_io = handler;
L
Linus Torvalds 已提交
421 422
	set_buffer_async_write(bh);
}
423 424 425 426 427

void mark_buffer_async_write(struct buffer_head *bh)
{
	mark_buffer_async_write_endio(bh, end_buffer_async_write);
}
L
Linus Torvalds 已提交
428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482
EXPORT_SYMBOL(mark_buffer_async_write);


/*
 * fs/buffer.c contains helper functions for buffer-backed address space's
 * fsync functions.  A common requirement for buffer-based filesystems is
 * that certain data from the backing blockdev needs to be written out for
 * a successful fsync().  For example, ext2 indirect blocks need to be
 * written back and waited upon before fsync() returns.
 *
 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
 * management of a list of dependent buffers at ->i_mapping->private_list.
 *
 * Locking is a little subtle: try_to_free_buffers() will remove buffers
 * from their controlling inode's queue when they are being freed.  But
 * try_to_free_buffers() will be operating against the *blockdev* mapping
 * at the time, not against the S_ISREG file which depends on those buffers.
 * So the locking for private_list is via the private_lock in the address_space
 * which backs the buffers.  Which is different from the address_space 
 * against which the buffers are listed.  So for a particular address_space,
 * mapping->private_lock does *not* protect mapping->private_list!  In fact,
 * mapping->private_list will always be protected by the backing blockdev's
 * ->private_lock.
 *
 * Which introduces a requirement: all buffers on an address_space's
 * ->private_list must be from the same address_space: the blockdev's.
 *
 * address_spaces which do not place buffers at ->private_list via these
 * utility functions are free to use private_lock and private_list for
 * whatever they want.  The only requirement is that list_empty(private_list)
 * be true at clear_inode() time.
 *
 * FIXME: clear_inode should not call invalidate_inode_buffers().  The
 * filesystems should do that.  invalidate_inode_buffers() should just go
 * BUG_ON(!list_empty).
 *
 * FIXME: mark_buffer_dirty_inode() is a data-plane operation.  It should
 * take an address_space, not an inode.  And it should be called
 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
 * queued up.
 *
 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
 * list if it is already on a list.  Because if the buffer is on a list,
 * it *must* already be on the right one.  If not, the filesystem is being
 * silly.  This will save a ton of locking.  But first we have to ensure
 * that buffers are taken *off* the old inode's list when they are freed
 * (presumably in truncate).  That requires careful auditing of all
 * filesystems (do it inside bforget()).  It could also be done by bringing
 * b_inode back.
 */

/*
 * The buffer's backing address_space's private_lock must be held
 */
483
static void __remove_assoc_queue(struct buffer_head *bh)
L
Linus Torvalds 已提交
484 485
{
	list_del_init(&bh->b_assoc_buffers);
486 487 488 489
	WARN_ON(!bh->b_assoc_map);
	if (buffer_write_io_error(bh))
		set_bit(AS_EIO, &bh->b_assoc_map->flags);
	bh->b_assoc_map = NULL;
L
Linus Torvalds 已提交
490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531
}

int inode_has_buffers(struct inode *inode)
{
	return !list_empty(&inode->i_data.private_list);
}

/*
 * osync is designed to support O_SYNC io.  It waits synchronously for
 * all already-submitted IO to complete, but does not queue any new
 * writes to the disk.
 *
 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
 * you dirty the buffers, and then use osync_inode_buffers to wait for
 * completion.  Any other dirty buffers which are not yet queued for
 * write will not be flushed to disk by the osync.
 */
static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
{
	struct buffer_head *bh;
	struct list_head *p;
	int err = 0;

	spin_lock(lock);
repeat:
	list_for_each_prev(p, list) {
		bh = BH_ENTRY(p);
		if (buffer_locked(bh)) {
			get_bh(bh);
			spin_unlock(lock);
			wait_on_buffer(bh);
			if (!buffer_uptodate(bh))
				err = -EIO;
			brelse(bh);
			spin_lock(lock);
			goto repeat;
		}
	}
	spin_unlock(lock);
	return err;
}

A
Al Viro 已提交
532
static void do_thaw_one(struct super_block *sb, void *unused)
533 534
{
	char b[BDEVNAME_SIZE];
A
Al Viro 已提交
535 536 537 538
	while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb))
		printk(KERN_WARNING "Emergency Thaw on %s\n",
		       bdevname(sb->s_bdev, b));
}
539

A
Al Viro 已提交
540 541 542
static void do_thaw_all(struct work_struct *work)
{
	iterate_supers(do_thaw_one, NULL);
543
	kfree(work);
544 545 546 547 548 549 550 551 552 553
	printk(KERN_WARNING "Emergency Thaw complete\n");
}

/**
 * emergency_thaw_all -- forcibly thaw every frozen filesystem
 *
 * Used for emergency unfreeze of all filesystems via SysRq
 */
void emergency_thaw_all(void)
{
554 555 556 557 558 559 560
	struct work_struct *work;

	work = kmalloc(sizeof(*work), GFP_ATOMIC);
	if (work) {
		INIT_WORK(work, do_thaw_all);
		schedule_work(work);
	}
561 562
}

L
Linus Torvalds 已提交
563
/**
564
 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
565
 * @mapping: the mapping which wants those buffers written
L
Linus Torvalds 已提交
566 567 568 569
 *
 * Starts I/O against the buffers at mapping->private_list, and waits upon
 * that I/O.
 *
570 571 572
 * Basically, this is a convenience function for fsync().
 * @mapping is a file or directory which needs those buffers to be written for
 * a successful fsync().
L
Linus Torvalds 已提交
573 574 575
 */
int sync_mapping_buffers(struct address_space *mapping)
{
576
	struct address_space *buffer_mapping = mapping->private_data;
L
Linus Torvalds 已提交
577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608

	if (buffer_mapping == NULL || list_empty(&mapping->private_list))
		return 0;

	return fsync_buffers_list(&buffer_mapping->private_lock,
					&mapping->private_list);
}
EXPORT_SYMBOL(sync_mapping_buffers);

/*
 * Called when we've recently written block `bblock', and it is known that
 * `bblock' was for a buffer_boundary() buffer.  This means that the block at
 * `bblock + 1' is probably a dirty indirect block.  Hunt it down and, if it's
 * dirty, schedule it for IO.  So that indirects merge nicely with their data.
 */
void write_boundary_block(struct block_device *bdev,
			sector_t bblock, unsigned blocksize)
{
	struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
	if (bh) {
		if (buffer_dirty(bh))
			ll_rw_block(WRITE, 1, &bh);
		put_bh(bh);
	}
}

void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
{
	struct address_space *mapping = inode->i_mapping;
	struct address_space *buffer_mapping = bh->b_page->mapping;

	mark_buffer_dirty(bh);
609 610
	if (!mapping->private_data) {
		mapping->private_data = buffer_mapping;
L
Linus Torvalds 已提交
611
	} else {
612
		BUG_ON(mapping->private_data != buffer_mapping);
L
Linus Torvalds 已提交
613
	}
614
	if (!bh->b_assoc_map) {
L
Linus Torvalds 已提交
615 616 617
		spin_lock(&buffer_mapping->private_lock);
		list_move_tail(&bh->b_assoc_buffers,
				&mapping->private_list);
618
		bh->b_assoc_map = mapping;
L
Linus Torvalds 已提交
619 620 621 622 623
		spin_unlock(&buffer_mapping->private_lock);
	}
}
EXPORT_SYMBOL(mark_buffer_dirty_inode);

624 625 626 627 628 629
/*
 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
 * dirty.
 *
 * If warn is true, then emit a warning if the page is not uptodate and has
 * not been truncated.
630 631
 *
 * The caller must hold mem_cgroup_begin_page_stat() lock.
632
 */
633 634
static void __set_page_dirty(struct page *page, struct address_space *mapping,
			     struct mem_cgroup *memcg, int warn)
635
{
636 637 638
	unsigned long flags;

	spin_lock_irqsave(&mapping->tree_lock, flags);
639 640
	if (page->mapping) {	/* Race with truncate? */
		WARN_ON_ONCE(warn && !PageUptodate(page));
641
		account_page_dirtied(page, mapping, memcg);
642 643 644
		radix_tree_tag_set(&mapping->page_tree,
				page_index(page), PAGECACHE_TAG_DIRTY);
	}
645
	spin_unlock_irqrestore(&mapping->tree_lock, flags);
646 647
}

L
Linus Torvalds 已提交
648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674
/*
 * Add a page to the dirty page list.
 *
 * It is a sad fact of life that this function is called from several places
 * deeply under spinlocking.  It may not sleep.
 *
 * If the page has buffers, the uptodate buffers are set dirty, to preserve
 * dirty-state coherency between the page and the buffers.  It the page does
 * not have buffers then when they are later attached they will all be set
 * dirty.
 *
 * The buffers are dirtied before the page is dirtied.  There's a small race
 * window in which a writepage caller may see the page cleanness but not the
 * buffer dirtiness.  That's fine.  If this code were to set the page dirty
 * before the buffers, a concurrent writepage caller could clear the page dirty
 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
 * page on the dirty page list.
 *
 * We use private_lock to lock against try_to_free_buffers while using the
 * page's buffer list.  Also use this to protect against clean buffers being
 * added to the page after it was set dirty.
 *
 * FIXME: may need to call ->reservepage here as well.  That's rather up to the
 * address_space though.
 */
int __set_page_dirty_buffers(struct page *page)
{
675
	int newly_dirty;
676
	struct mem_cgroup *memcg;
677
	struct address_space *mapping = page_mapping(page);
678 679 680

	if (unlikely(!mapping))
		return !TestSetPageDirty(page);
L
Linus Torvalds 已提交
681 682 683 684 685 686 687 688 689 690 691

	spin_lock(&mapping->private_lock);
	if (page_has_buffers(page)) {
		struct buffer_head *head = page_buffers(page);
		struct buffer_head *bh = head;

		do {
			set_buffer_dirty(bh);
			bh = bh->b_this_page;
		} while (bh != head);
	}
692 693 694 695 696
	/*
	 * Use mem_group_begin_page_stat() to keep PageDirty synchronized with
	 * per-memcg dirty page counters.
	 */
	memcg = mem_cgroup_begin_page_stat(page);
697
	newly_dirty = !TestSetPageDirty(page);
L
Linus Torvalds 已提交
698 699
	spin_unlock(&mapping->private_lock);

700
	if (newly_dirty)
701 702 703 704 705 706 707
		__set_page_dirty(page, mapping, memcg, 1);

	mem_cgroup_end_page_stat(memcg);

	if (newly_dirty)
		__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);

708
	return newly_dirty;
L
Linus Torvalds 已提交
709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734
}
EXPORT_SYMBOL(__set_page_dirty_buffers);

/*
 * Write out and wait upon a list of buffers.
 *
 * We have conflicting pressures: we want to make sure that all
 * initially dirty buffers get waited on, but that any subsequently
 * dirtied buffers don't.  After all, we don't want fsync to last
 * forever if somebody is actively writing to the file.
 *
 * Do this in two main stages: first we copy dirty buffers to a
 * temporary inode list, queueing the writes as we go.  Then we clean
 * up, waiting for those writes to complete.
 * 
 * During this second stage, any subsequent updates to the file may end
 * up refiling the buffer on the original inode's dirty list again, so
 * there is a chance we will end up with a buffer queued for write but
 * not yet completed on that list.  So, as a final cleanup we go through
 * the osync code to catch these locked, dirty buffers without requeuing
 * any newly dirty buffers for write.
 */
static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
{
	struct buffer_head *bh;
	struct list_head tmp;
J
Jens Axboe 已提交
735
	struct address_space *mapping;
L
Linus Torvalds 已提交
736
	int err = 0, err2;
J
Jens Axboe 已提交
737
	struct blk_plug plug;
L
Linus Torvalds 已提交
738 739

	INIT_LIST_HEAD(&tmp);
J
Jens Axboe 已提交
740
	blk_start_plug(&plug);
L
Linus Torvalds 已提交
741 742 743 744

	spin_lock(lock);
	while (!list_empty(list)) {
		bh = BH_ENTRY(list->next);
745
		mapping = bh->b_assoc_map;
746
		__remove_assoc_queue(bh);
747 748 749
		/* Avoid race with mark_buffer_dirty_inode() which does
		 * a lockless check and we rely on seeing the dirty bit */
		smp_mb();
L
Linus Torvalds 已提交
750 751
		if (buffer_dirty(bh) || buffer_locked(bh)) {
			list_add(&bh->b_assoc_buffers, &tmp);
752
			bh->b_assoc_map = mapping;
L
Linus Torvalds 已提交
753 754 755 756 757
			if (buffer_dirty(bh)) {
				get_bh(bh);
				spin_unlock(lock);
				/*
				 * Ensure any pending I/O completes so that
C
Christoph Hellwig 已提交
758 759 760 761
				 * write_dirty_buffer() actually writes the
				 * current contents - it is a noop if I/O is
				 * still in flight on potentially older
				 * contents.
L
Linus Torvalds 已提交
762
				 */
J
Jens Axboe 已提交
763
				write_dirty_buffer(bh, WRITE_SYNC);
764 765 766 767 768 769 770

				/*
				 * Kick off IO for the previous mapping. Note
				 * that we will not run the very last mapping,
				 * wait_on_buffer() will do that for us
				 * through sync_buffer().
				 */
L
Linus Torvalds 已提交
771 772 773 774 775 776
				brelse(bh);
				spin_lock(lock);
			}
		}
	}

J
Jens Axboe 已提交
777 778 779 780
	spin_unlock(lock);
	blk_finish_plug(&plug);
	spin_lock(lock);

L
Linus Torvalds 已提交
781 782 783
	while (!list_empty(&tmp)) {
		bh = BH_ENTRY(tmp.prev);
		get_bh(bh);
784 785 786 787 788 789 790
		mapping = bh->b_assoc_map;
		__remove_assoc_queue(bh);
		/* Avoid race with mark_buffer_dirty_inode() which does
		 * a lockless check and we rely on seeing the dirty bit */
		smp_mb();
		if (buffer_dirty(bh)) {
			list_add(&bh->b_assoc_buffers,
791
				 &mapping->private_list);
792 793
			bh->b_assoc_map = mapping;
		}
L
Linus Torvalds 已提交
794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823
		spin_unlock(lock);
		wait_on_buffer(bh);
		if (!buffer_uptodate(bh))
			err = -EIO;
		brelse(bh);
		spin_lock(lock);
	}
	
	spin_unlock(lock);
	err2 = osync_buffers_list(lock, list);
	if (err)
		return err;
	else
		return err2;
}

/*
 * Invalidate any and all dirty buffers on a given inode.  We are
 * probably unmounting the fs, but that doesn't mean we have already
 * done a sync().  Just drop the buffers from the inode list.
 *
 * NOTE: we take the inode's blockdev's mapping's private_lock.  Which
 * assumes that all the buffers are against the blockdev.  Not true
 * for reiserfs.
 */
void invalidate_inode_buffers(struct inode *inode)
{
	if (inode_has_buffers(inode)) {
		struct address_space *mapping = &inode->i_data;
		struct list_head *list = &mapping->private_list;
824
		struct address_space *buffer_mapping = mapping->private_data;
L
Linus Torvalds 已提交
825 826 827 828 829 830 831

		spin_lock(&buffer_mapping->private_lock);
		while (!list_empty(list))
			__remove_assoc_queue(BH_ENTRY(list->next));
		spin_unlock(&buffer_mapping->private_lock);
	}
}
J
Jan Kara 已提交
832
EXPORT_SYMBOL(invalidate_inode_buffers);
L
Linus Torvalds 已提交
833 834 835 836 837 838 839 840 841 842 843 844 845 846

/*
 * Remove any clean buffers from the inode's buffer list.  This is called
 * when we're trying to free the inode itself.  Those buffers can pin it.
 *
 * Returns true if all buffers were removed.
 */
int remove_inode_buffers(struct inode *inode)
{
	int ret = 1;

	if (inode_has_buffers(inode)) {
		struct address_space *mapping = &inode->i_data;
		struct list_head *list = &mapping->private_list;
847
		struct address_space *buffer_mapping = mapping->private_data;
L
Linus Torvalds 已提交
848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941

		spin_lock(&buffer_mapping->private_lock);
		while (!list_empty(list)) {
			struct buffer_head *bh = BH_ENTRY(list->next);
			if (buffer_dirty(bh)) {
				ret = 0;
				break;
			}
			__remove_assoc_queue(bh);
		}
		spin_unlock(&buffer_mapping->private_lock);
	}
	return ret;
}

/*
 * Create the appropriate buffers when given a page for data area and
 * the size of each buffer.. Use the bh->b_this_page linked list to
 * follow the buffers created.  Return NULL if unable to create more
 * buffers.
 *
 * The retry flag is used to differentiate async IO (paging, swapping)
 * which may not fail from ordinary buffer allocations.
 */
struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
		int retry)
{
	struct buffer_head *bh, *head;
	long offset;

try_again:
	head = NULL;
	offset = PAGE_SIZE;
	while ((offset -= size) >= 0) {
		bh = alloc_buffer_head(GFP_NOFS);
		if (!bh)
			goto no_grow;

		bh->b_this_page = head;
		bh->b_blocknr = -1;
		head = bh;

		bh->b_size = size;

		/* Link the buffer to its page */
		set_bh_page(bh, page, offset);
	}
	return head;
/*
 * In case anything failed, we just free everything we got.
 */
no_grow:
	if (head) {
		do {
			bh = head;
			head = head->b_this_page;
			free_buffer_head(bh);
		} while (head);
	}

	/*
	 * Return failure for non-async IO requests.  Async IO requests
	 * are not allowed to fail, so we have to wait until buffer heads
	 * become available.  But we don't want tasks sleeping with 
	 * partially complete buffers, so all were released above.
	 */
	if (!retry)
		return NULL;

	/* We're _really_ low on memory. Now we just
	 * wait for old buffer heads to become free due to
	 * finishing IO.  Since this is an async request and
	 * the reserve list is empty, we're sure there are 
	 * async buffer heads in use.
	 */
	free_more_memory();
	goto try_again;
}
EXPORT_SYMBOL_GPL(alloc_page_buffers);

static inline void
link_dev_buffers(struct page *page, struct buffer_head *head)
{
	struct buffer_head *bh, *tail;

	bh = head;
	do {
		tail = bh;
		bh = bh->b_this_page;
	} while (bh);
	tail->b_this_page = head;
	attach_page_buffers(page, head);
}

942 943 944 945 946 947 948 949 950 951 952 953
static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
{
	sector_t retval = ~((sector_t)0);
	loff_t sz = i_size_read(bdev->bd_inode);

	if (sz) {
		unsigned int sizebits = blksize_bits(size);
		retval = (sz >> sizebits);
	}
	return retval;
}

L
Linus Torvalds 已提交
954 955 956
/*
 * Initialise the state of a blockdev page's buffers.
 */ 
957
static sector_t
L
Linus Torvalds 已提交
958 959 960 961 962 963
init_page_buffers(struct page *page, struct block_device *bdev,
			sector_t block, int size)
{
	struct buffer_head *head = page_buffers(page);
	struct buffer_head *bh = head;
	int uptodate = PageUptodate(page);
964
	sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode), size);
L
Linus Torvalds 已提交
965 966 967 968 969 970 971 972

	do {
		if (!buffer_mapped(bh)) {
			init_buffer(bh, NULL, NULL);
			bh->b_bdev = bdev;
			bh->b_blocknr = block;
			if (uptodate)
				set_buffer_uptodate(bh);
973 974
			if (block < end_block)
				set_buffer_mapped(bh);
L
Linus Torvalds 已提交
975 976 977 978
		}
		block++;
		bh = bh->b_this_page;
	} while (bh != head);
979 980 981 982 983

	/*
	 * Caller needs to validate requested block against end of device.
	 */
	return end_block;
L
Linus Torvalds 已提交
984 985 986 987 988
}

/*
 * Create the page-cache page that contains the requested block.
 *
989
 * This is used purely for blockdev mappings.
L
Linus Torvalds 已提交
990
 */
991
static int
L
Linus Torvalds 已提交
992
grow_dev_page(struct block_device *bdev, sector_t block,
993
	      pgoff_t index, int size, int sizebits, gfp_t gfp)
L
Linus Torvalds 已提交
994 995 996 997
{
	struct inode *inode = bdev->bd_inode;
	struct page *page;
	struct buffer_head *bh;
998 999
	sector_t end_block;
	int ret = 0;		/* Will call free_more_memory() */
1000
	gfp_t gfp_mask;
L
Linus Torvalds 已提交
1001

1002 1003
	gfp_mask = (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS) | gfp;

1004 1005 1006 1007 1008 1009 1010 1011 1012
	/*
	 * XXX: __getblk_slow() can not really deal with failure and
	 * will endlessly loop on improvised global reclaim.  Prefer
	 * looping in the allocator rather than here, at least that
	 * code knows what it's doing.
	 */
	gfp_mask |= __GFP_NOFAIL;

	page = find_or_create_page(inode->i_mapping, index, gfp_mask);
L
Linus Torvalds 已提交
1013
	if (!page)
1014
		return ret;
L
Linus Torvalds 已提交
1015

1016
	BUG_ON(!PageLocked(page));
L
Linus Torvalds 已提交
1017 1018 1019 1020

	if (page_has_buffers(page)) {
		bh = page_buffers(page);
		if (bh->b_size == size) {
1021
			end_block = init_page_buffers(page, bdev,
1022 1023
						(sector_t)index << sizebits,
						size);
1024
			goto done;
L
Linus Torvalds 已提交
1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043
		}
		if (!try_to_free_buffers(page))
			goto failed;
	}

	/*
	 * Allocate some buffers for this page
	 */
	bh = alloc_page_buffers(page, size, 0);
	if (!bh)
		goto failed;

	/*
	 * Link the page to the buffers and initialise them.  Take the
	 * lock to be atomic wrt __find_get_block(), which does not
	 * run under the page lock.
	 */
	spin_lock(&inode->i_mapping->private_lock);
	link_dev_buffers(page, bh);
1044 1045
	end_block = init_page_buffers(page, bdev, (sector_t)index << sizebits,
			size);
L
Linus Torvalds 已提交
1046
	spin_unlock(&inode->i_mapping->private_lock);
1047 1048
done:
	ret = (block < end_block) ? 1 : -ENXIO;
L
Linus Torvalds 已提交
1049 1050 1051
failed:
	unlock_page(page);
	page_cache_release(page);
1052
	return ret;
L
Linus Torvalds 已提交
1053 1054 1055 1056 1057 1058
}

/*
 * Create buffers for the specified block device block's page.  If
 * that page was dirty, the buffers are set dirty also.
 */
1059
static int
1060
grow_buffers(struct block_device *bdev, sector_t block, int size, gfp_t gfp)
L
Linus Torvalds 已提交
1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071
{
	pgoff_t index;
	int sizebits;

	sizebits = -1;
	do {
		sizebits++;
	} while ((size << sizebits) < PAGE_SIZE);

	index = block >> sizebits;

1072 1073 1074 1075 1076 1077 1078 1079 1080
	/*
	 * Check for a block which wants to lie outside our maximum possible
	 * pagecache index.  (this comparison is done using sector_t types).
	 */
	if (unlikely(index != block >> sizebits)) {
		char b[BDEVNAME_SIZE];

		printk(KERN_ERR "%s: requested out-of-range block %llu for "
			"device %s\n",
1081
			__func__, (unsigned long long)block,
1082 1083 1084
			bdevname(bdev, b));
		return -EIO;
	}
1085

L
Linus Torvalds 已提交
1086
	/* Create a page with the proper size buffers.. */
1087
	return grow_dev_page(bdev, block, index, size, sizebits, gfp);
L
Linus Torvalds 已提交
1088 1089
}

1090 1091 1092
struct buffer_head *
__getblk_slow(struct block_device *bdev, sector_t block,
	     unsigned size, gfp_t gfp)
L
Linus Torvalds 已提交
1093 1094
{
	/* Size must be multiple of hard sectorsize */
1095
	if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
L
Linus Torvalds 已提交
1096 1097 1098
			(size < 512 || size > PAGE_SIZE))) {
		printk(KERN_ERR "getblk(): invalid block size %d requested\n",
					size);
1099 1100
		printk(KERN_ERR "logical block size: %d\n",
					bdev_logical_block_size(bdev));
L
Linus Torvalds 已提交
1101 1102 1103 1104 1105

		dump_stack();
		return NULL;
	}

1106 1107 1108
	for (;;) {
		struct buffer_head *bh;
		int ret;
L
Linus Torvalds 已提交
1109 1110 1111 1112

		bh = __find_get_block(bdev, block, size);
		if (bh)
			return bh;
1113

1114
		ret = grow_buffers(bdev, block, size, gfp);
1115 1116 1117 1118
		if (ret < 0)
			return NULL;
		if (ret == 0)
			free_more_memory();
L
Linus Torvalds 已提交
1119 1120
	}
}
1121
EXPORT_SYMBOL(__getblk_slow);
L
Linus Torvalds 已提交
1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147

/*
 * The relationship between dirty buffers and dirty pages:
 *
 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
 * the page is tagged dirty in its radix tree.
 *
 * At all times, the dirtiness of the buffers represents the dirtiness of
 * subsections of the page.  If the page has buffers, the page dirty bit is
 * merely a hint about the true dirty state.
 *
 * When a page is set dirty in its entirety, all its buffers are marked dirty
 * (if the page has buffers).
 *
 * When a buffer is marked dirty, its page is dirtied, but the page's other
 * buffers are not.
 *
 * Also.  When blockdev buffers are explicitly read with bread(), they
 * individually become uptodate.  But their backing page remains not
 * uptodate - even if all of its buffers are uptodate.  A subsequent
 * block_read_full_page() against that page will discover all the uptodate
 * buffers, will set the page uptodate and will perform no I/O.
 */

/**
 * mark_buffer_dirty - mark a buffer_head as needing writeout
1148
 * @bh: the buffer_head to mark dirty
L
Linus Torvalds 已提交
1149 1150 1151 1152 1153 1154 1155
 *
 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
 * backing page dirty, then tag the page as dirty in its address_space's radix
 * tree and then attach the address_space's inode to its superblock's dirty
 * inode list.
 *
 * mark_buffer_dirty() is atomic.  It takes bh->b_page->mapping->private_lock,
1156
 * mapping->tree_lock and mapping->host->i_lock.
L
Linus Torvalds 已提交
1157
 */
1158
void mark_buffer_dirty(struct buffer_head *bh)
L
Linus Torvalds 已提交
1159
{
1160
	WARN_ON_ONCE(!buffer_uptodate(bh));
1161

1162 1163
	trace_block_dirty_buffer(bh);

1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175
	/*
	 * Very *carefully* optimize the it-is-already-dirty case.
	 *
	 * Don't let the final "is it dirty" escape to before we
	 * perhaps modified the buffer.
	 */
	if (buffer_dirty(bh)) {
		smp_mb();
		if (buffer_dirty(bh))
			return;
	}

1176 1177
	if (!test_set_buffer_dirty(bh)) {
		struct page *page = bh->b_page;
1178 1179 1180 1181
		struct address_space *mapping = NULL;
		struct mem_cgroup *memcg;

		memcg = mem_cgroup_begin_page_stat(page);
1182
		if (!TestSetPageDirty(page)) {
1183
			mapping = page_mapping(page);
1184
			if (mapping)
1185
				__set_page_dirty(page, mapping, memcg, 0);
1186
		}
1187 1188 1189
		mem_cgroup_end_page_stat(memcg);
		if (mapping)
			__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
1190
	}
L
Linus Torvalds 已提交
1191
}
1192
EXPORT_SYMBOL(mark_buffer_dirty);
L
Linus Torvalds 已提交
1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206

/*
 * Decrement a buffer_head's reference count.  If all buffers against a page
 * have zero reference count, are clean and unlocked, and if the page is clean
 * and unlocked then try_to_free_buffers() may strip the buffers from the page
 * in preparation for freeing it (sometimes, rarely, buffers are removed from
 * a page but it ends up not being freed, and buffers may later be reattached).
 */
void __brelse(struct buffer_head * buf)
{
	if (atomic_read(&buf->b_count)) {
		put_bh(buf);
		return;
	}
A
Arjan van de Ven 已提交
1207
	WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
L
Linus Torvalds 已提交
1208
}
1209
EXPORT_SYMBOL(__brelse);
L
Linus Torvalds 已提交
1210 1211 1212 1213 1214 1215 1216 1217

/*
 * bforget() is like brelse(), except it discards any
 * potentially dirty data.
 */
void __bforget(struct buffer_head *bh)
{
	clear_buffer_dirty(bh);
1218
	if (bh->b_assoc_map) {
L
Linus Torvalds 已提交
1219 1220 1221 1222
		struct address_space *buffer_mapping = bh->b_page->mapping;

		spin_lock(&buffer_mapping->private_lock);
		list_del_init(&bh->b_assoc_buffers);
1223
		bh->b_assoc_map = NULL;
L
Linus Torvalds 已提交
1224 1225 1226 1227
		spin_unlock(&buffer_mapping->private_lock);
	}
	__brelse(bh);
}
1228
EXPORT_SYMBOL(__bforget);
L
Linus Torvalds 已提交
1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261

static struct buffer_head *__bread_slow(struct buffer_head *bh)
{
	lock_buffer(bh);
	if (buffer_uptodate(bh)) {
		unlock_buffer(bh);
		return bh;
	} else {
		get_bh(bh);
		bh->b_end_io = end_buffer_read_sync;
		submit_bh(READ, bh);
		wait_on_buffer(bh);
		if (buffer_uptodate(bh))
			return bh;
	}
	brelse(bh);
	return NULL;
}

/*
 * Per-cpu buffer LRU implementation.  To reduce the cost of __find_get_block().
 * The bhs[] array is sorted - newest buffer is at bhs[0].  Buffers have their
 * refcount elevated by one when they're in an LRU.  A buffer can only appear
 * once in a particular CPU's LRU.  A single buffer can be present in multiple
 * CPU's LRUs at the same time.
 *
 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
 * sb_find_get_block().
 *
 * The LRUs themselves only need locking against invalidate_bh_lrus.  We use
 * a local interrupt disable for that.
 */

1262
#define BH_LRU_SIZE	16
L
Linus Torvalds 已提交
1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293

struct bh_lru {
	struct buffer_head *bhs[BH_LRU_SIZE];
};

static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};

#ifdef CONFIG_SMP
#define bh_lru_lock()	local_irq_disable()
#define bh_lru_unlock()	local_irq_enable()
#else
#define bh_lru_lock()	preempt_disable()
#define bh_lru_unlock()	preempt_enable()
#endif

static inline void check_irqs_on(void)
{
#ifdef irqs_disabled
	BUG_ON(irqs_disabled());
#endif
}

/*
 * The LRU management algorithm is dopey-but-simple.  Sorry.
 */
static void bh_lru_install(struct buffer_head *bh)
{
	struct buffer_head *evictee = NULL;

	check_irqs_on();
	bh_lru_lock();
1294
	if (__this_cpu_read(bh_lrus.bhs[0]) != bh) {
L
Linus Torvalds 已提交
1295 1296 1297 1298 1299 1300 1301
		struct buffer_head *bhs[BH_LRU_SIZE];
		int in;
		int out = 0;

		get_bh(bh);
		bhs[out++] = bh;
		for (in = 0; in < BH_LRU_SIZE; in++) {
1302 1303
			struct buffer_head *bh2 =
				__this_cpu_read(bh_lrus.bhs[in]);
L
Linus Torvalds 已提交
1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317

			if (bh2 == bh) {
				__brelse(bh2);
			} else {
				if (out >= BH_LRU_SIZE) {
					BUG_ON(evictee != NULL);
					evictee = bh2;
				} else {
					bhs[out++] = bh2;
				}
			}
		}
		while (out < BH_LRU_SIZE)
			bhs[out++] = NULL;
1318
		memcpy(this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs));
L
Linus Torvalds 已提交
1319 1320 1321 1322 1323 1324 1325 1326 1327 1328
	}
	bh_lru_unlock();

	if (evictee)
		__brelse(evictee);
}

/*
 * Look up the bh in this cpu's LRU.  If it's there, move it to the head.
 */
1329
static struct buffer_head *
1330
lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
L
Linus Torvalds 已提交
1331 1332
{
	struct buffer_head *ret = NULL;
1333
	unsigned int i;
L
Linus Torvalds 已提交
1334 1335 1336 1337

	check_irqs_on();
	bh_lru_lock();
	for (i = 0; i < BH_LRU_SIZE; i++) {
1338
		struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
L
Linus Torvalds 已提交
1339

1340 1341
		if (bh && bh->b_blocknr == block && bh->b_bdev == bdev &&
		    bh->b_size == size) {
L
Linus Torvalds 已提交
1342 1343
			if (i) {
				while (i) {
1344 1345
					__this_cpu_write(bh_lrus.bhs[i],
						__this_cpu_read(bh_lrus.bhs[i - 1]));
L
Linus Torvalds 已提交
1346 1347
					i--;
				}
1348
				__this_cpu_write(bh_lrus.bhs[0], bh);
L
Linus Torvalds 已提交
1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364
			}
			get_bh(bh);
			ret = bh;
			break;
		}
	}
	bh_lru_unlock();
	return ret;
}

/*
 * Perform a pagecache lookup for the matching buffer.  If it's there, refresh
 * it in the LRU and mark it as accessed.  If it is not present then return
 * NULL
 */
struct buffer_head *
1365
__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
L
Linus Torvalds 已提交
1366 1367 1368 1369
{
	struct buffer_head *bh = lookup_bh_lru(bdev, block, size);

	if (bh == NULL) {
1370
		/* __find_get_block_slow will mark the page accessed */
1371
		bh = __find_get_block_slow(bdev, block);
L
Linus Torvalds 已提交
1372 1373
		if (bh)
			bh_lru_install(bh);
1374
	} else
L
Linus Torvalds 已提交
1375
		touch_buffer(bh);
1376

L
Linus Torvalds 已提交
1377 1378 1379 1380 1381
	return bh;
}
EXPORT_SYMBOL(__find_get_block);

/*
1382
 * __getblk_gfp() will locate (and, if necessary, create) the buffer_head
L
Linus Torvalds 已提交
1383 1384 1385
 * which corresponds to the passed block_device, block and size. The
 * returned buffer has its reference count incremented.
 *
1386 1387
 * __getblk_gfp() will lock up the machine if grow_dev_page's
 * try_to_free_buffers() attempt is failing.  FIXME, perhaps?
L
Linus Torvalds 已提交
1388 1389
 */
struct buffer_head *
1390 1391
__getblk_gfp(struct block_device *bdev, sector_t block,
	     unsigned size, gfp_t gfp)
L
Linus Torvalds 已提交
1392 1393 1394 1395 1396
{
	struct buffer_head *bh = __find_get_block(bdev, block, size);

	might_sleep();
	if (bh == NULL)
1397
		bh = __getblk_slow(bdev, block, size, gfp);
L
Linus Torvalds 已提交
1398 1399
	return bh;
}
1400
EXPORT_SYMBOL(__getblk_gfp);
L
Linus Torvalds 已提交
1401 1402 1403 1404

/*
 * Do async read-ahead on a buffer..
 */
1405
void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
L
Linus Torvalds 已提交
1406 1407
{
	struct buffer_head *bh = __getblk(bdev, block, size);
A
Andrew Morton 已提交
1408 1409 1410 1411
	if (likely(bh)) {
		ll_rw_block(READA, 1, &bh);
		brelse(bh);
	}
L
Linus Torvalds 已提交
1412 1413 1414 1415
}
EXPORT_SYMBOL(__breadahead);

/**
1416
 *  __bread_gfp() - reads a specified block and returns the bh
1417
 *  @bdev: the block_device to read from
L
Linus Torvalds 已提交
1418 1419
 *  @block: number of block
 *  @size: size (in bytes) to read
1420 1421
 *  @gfp: page allocation flag
 *
L
Linus Torvalds 已提交
1422
 *  Reads a specified block, and returns buffer head that contains it.
1423 1424
 *  The page cache can be allocated from non-movable area
 *  not to prevent page migration if you set gfp to zero.
L
Linus Torvalds 已提交
1425 1426 1427
 *  It returns NULL if the block was unreadable.
 */
struct buffer_head *
1428 1429
__bread_gfp(struct block_device *bdev, sector_t block,
		   unsigned size, gfp_t gfp)
L
Linus Torvalds 已提交
1430
{
1431
	struct buffer_head *bh = __getblk_gfp(bdev, block, size, gfp);
L
Linus Torvalds 已提交
1432

A
Andrew Morton 已提交
1433
	if (likely(bh) && !buffer_uptodate(bh))
L
Linus Torvalds 已提交
1434 1435 1436
		bh = __bread_slow(bh);
	return bh;
}
1437
EXPORT_SYMBOL(__bread_gfp);
L
Linus Torvalds 已提交
1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454

/*
 * invalidate_bh_lrus() is called rarely - but not only at unmount.
 * This doesn't race because it runs in each cpu either in irq
 * or with preempt disabled.
 */
static void invalidate_bh_lru(void *arg)
{
	struct bh_lru *b = &get_cpu_var(bh_lrus);
	int i;

	for (i = 0; i < BH_LRU_SIZE; i++) {
		brelse(b->bhs[i]);
		b->bhs[i] = NULL;
	}
	put_cpu_var(bh_lrus);
}
1455 1456 1457 1458 1459

static bool has_bh_in_lru(int cpu, void *dummy)
{
	struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
	int i;
L
Linus Torvalds 已提交
1460
	
1461 1462 1463 1464 1465 1466 1467 1468
	for (i = 0; i < BH_LRU_SIZE; i++) {
		if (b->bhs[i])
			return 1;
	}

	return 0;
}

P
Peter Zijlstra 已提交
1469
void invalidate_bh_lrus(void)
L
Linus Torvalds 已提交
1470
{
1471
	on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL);
L
Linus Torvalds 已提交
1472
}
N
Nick Piggin 已提交
1473
EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
L
Linus Torvalds 已提交
1474 1475 1476 1477 1478

void set_bh_page(struct buffer_head *bh,
		struct page *page, unsigned long offset)
{
	bh->b_page = page;
1479
	BUG_ON(offset >= PAGE_SIZE);
L
Linus Torvalds 已提交
1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492
	if (PageHighMem(page))
		/*
		 * This catches illegal uses and preserves the offset:
		 */
		bh->b_data = (char *)(0 + offset);
	else
		bh->b_data = page_address(page) + offset;
}
EXPORT_SYMBOL(set_bh_page);

/*
 * Called when truncating a buffer on a page completely.
 */
1493 1494 1495 1496 1497 1498

/* Bits that are cleared during an invalidate */
#define BUFFER_FLAGS_DISCARD \
	(1 << BH_Mapped | 1 << BH_New | 1 << BH_Req | \
	 1 << BH_Delay | 1 << BH_Unwritten)

1499
static void discard_buffer(struct buffer_head * bh)
L
Linus Torvalds 已提交
1500
{
1501 1502
	unsigned long b_state, b_state_old;

L
Linus Torvalds 已提交
1503 1504 1505
	lock_buffer(bh);
	clear_buffer_dirty(bh);
	bh->b_bdev = NULL;
1506 1507 1508 1509 1510 1511 1512 1513
	b_state = bh->b_state;
	for (;;) {
		b_state_old = cmpxchg(&bh->b_state, b_state,
				      (b_state & ~BUFFER_FLAGS_DISCARD));
		if (b_state_old == b_state)
			break;
		b_state = b_state_old;
	}
L
Linus Torvalds 已提交
1514 1515 1516 1517
	unlock_buffer(bh);
}

/**
1518
 * block_invalidatepage - invalidate part or all of a buffer-backed page
L
Linus Torvalds 已提交
1519 1520
 *
 * @page: the page which is affected
1521 1522
 * @offset: start of the range to invalidate
 * @length: length of the range to invalidate
L
Linus Torvalds 已提交
1523 1524
 *
 * block_invalidatepage() is called when all or part of the page has become
1525
 * invalidated by a truncate operation.
L
Linus Torvalds 已提交
1526 1527 1528 1529 1530 1531 1532
 *
 * block_invalidatepage() does not have to release all buffers, but it must
 * ensure that no dirty buffer is left outside @offset and that no I/O
 * is underway against any of the blocks which are outside the truncation
 * point.  Because the caller is about to free (and possibly reuse) those
 * blocks on-disk.
 */
1533 1534
void block_invalidatepage(struct page *page, unsigned int offset,
			  unsigned int length)
L
Linus Torvalds 已提交
1535 1536 1537
{
	struct buffer_head *head, *bh, *next;
	unsigned int curr_off = 0;
1538
	unsigned int stop = length + offset;
L
Linus Torvalds 已提交
1539 1540 1541 1542 1543

	BUG_ON(!PageLocked(page));
	if (!page_has_buffers(page))
		goto out;

1544 1545 1546 1547 1548
	/*
	 * Check for overflow
	 */
	BUG_ON(stop > PAGE_CACHE_SIZE || stop < length);

L
Linus Torvalds 已提交
1549 1550 1551 1552 1553 1554
	head = page_buffers(page);
	bh = head;
	do {
		unsigned int next_off = curr_off + bh->b_size;
		next = bh->b_this_page;

1555 1556 1557 1558 1559 1560
		/*
		 * Are we still fully in range ?
		 */
		if (next_off > stop)
			goto out;

L
Linus Torvalds 已提交
1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575
		/*
		 * is this block fully invalidated?
		 */
		if (offset <= curr_off)
			discard_buffer(bh);
		curr_off = next_off;
		bh = next;
	} while (bh != head);

	/*
	 * We release buffers only if the entire page is being invalidated.
	 * The get_block cached value has been unconditionally invalidated,
	 * so real IO is not possible anymore.
	 */
	if (offset == 0)
1576
		try_to_release_page(page, 0);
L
Linus Torvalds 已提交
1577
out:
1578
	return;
L
Linus Torvalds 已提交
1579 1580 1581
}
EXPORT_SYMBOL(block_invalidatepage);

1582

L
Linus Torvalds 已提交
1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639
/*
 * We attach and possibly dirty the buffers atomically wrt
 * __set_page_dirty_buffers() via private_lock.  try_to_free_buffers
 * is already excluded via the page lock.
 */
void create_empty_buffers(struct page *page,
			unsigned long blocksize, unsigned long b_state)
{
	struct buffer_head *bh, *head, *tail;

	head = alloc_page_buffers(page, blocksize, 1);
	bh = head;
	do {
		bh->b_state |= b_state;
		tail = bh;
		bh = bh->b_this_page;
	} while (bh);
	tail->b_this_page = head;

	spin_lock(&page->mapping->private_lock);
	if (PageUptodate(page) || PageDirty(page)) {
		bh = head;
		do {
			if (PageDirty(page))
				set_buffer_dirty(bh);
			if (PageUptodate(page))
				set_buffer_uptodate(bh);
			bh = bh->b_this_page;
		} while (bh != head);
	}
	attach_page_buffers(page, head);
	spin_unlock(&page->mapping->private_lock);
}
EXPORT_SYMBOL(create_empty_buffers);

/*
 * We are taking a block for data and we don't want any output from any
 * buffer-cache aliases starting from return from that function and
 * until the moment when something will explicitly mark the buffer
 * dirty (hopefully that will not happen until we will free that block ;-)
 * We don't even need to mark it not-uptodate - nobody can expect
 * anything from a newly allocated buffer anyway. We used to used
 * unmap_buffer() for such invalidation, but that was wrong. We definitely
 * don't want to mark the alias unmapped, for example - it would confuse
 * anyone who might pick it with bread() afterwards...
 *
 * Also..  Note that bforget() doesn't lock the buffer.  So there can
 * be writeout I/O going on against recently-freed buffers.  We don't
 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
 * only if we really need to.  That happens here.
 */
void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
{
	struct buffer_head *old_bh;

	might_sleep();

1640
	old_bh = __find_get_block_slow(bdev, block);
L
Linus Torvalds 已提交
1641 1642 1643 1644 1645 1646 1647 1648 1649
	if (old_bh) {
		clear_buffer_dirty(old_bh);
		wait_on_buffer(old_bh);
		clear_buffer_req(old_bh);
		__brelse(old_bh);
	}
}
EXPORT_SYMBOL(unmap_underlying_metadata);

1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671
/*
 * Size is a power-of-two in the range 512..PAGE_SIZE,
 * and the case we care about most is PAGE_SIZE.
 *
 * So this *could* possibly be written with those
 * constraints in mind (relevant mostly if some
 * architecture has a slow bit-scan instruction)
 */
static inline int block_size_bits(unsigned int blocksize)
{
	return ilog2(blocksize);
}

static struct buffer_head *create_page_buffers(struct page *page, struct inode *inode, unsigned int b_state)
{
	BUG_ON(!PageLocked(page));

	if (!page_has_buffers(page))
		create_empty_buffers(page, 1 << ACCESS_ONCE(inode->i_blkbits), b_state);
	return page_buffers(page);
}

L
Linus Torvalds 已提交
1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695
/*
 * NOTE! All mapped/uptodate combinations are valid:
 *
 *	Mapped	Uptodate	Meaning
 *
 *	No	No		"unknown" - must do get_block()
 *	No	Yes		"hole" - zero-filled
 *	Yes	No		"allocated" - allocated on disk, not read in
 *	Yes	Yes		"valid" - allocated and up-to-date in memory.
 *
 * "Dirty" is valid only with the last case (mapped+uptodate).
 */

/*
 * While block_write_full_page is writing back the dirty buffers under
 * the page lock, whoever dirtied the buffers may decide to clean them
 * again at any time.  We handle that by only looking at the buffer
 * state inside lock_buffer().
 *
 * If block_write_full_page() is called for regular writeback
 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
 * locked buffer.   This only can happen if someone has written the buffer
 * directly, with submit_bh().  At the address_space level PageWriteback
 * prevents this contention from occurring.
1696 1697
 *
 * If block_write_full_page() is called with wbc->sync_mode ==
J
Jens Axboe 已提交
1698 1699
 * WB_SYNC_ALL, the writes are posted using WRITE_SYNC; this
 * causes the writes to be flagged as synchronous writes.
L
Linus Torvalds 已提交
1700 1701
 */
static int __block_write_full_page(struct inode *inode, struct page *page,
1702 1703
			get_block_t *get_block, struct writeback_control *wbc,
			bh_end_io_t *handler)
L
Linus Torvalds 已提交
1704 1705 1706 1707
{
	int err;
	sector_t block;
	sector_t last_block;
1708
	struct buffer_head *bh, *head;
1709
	unsigned int blocksize, bbits;
L
Linus Torvalds 已提交
1710
	int nr_underway = 0;
1711
	int write_op = (wbc->sync_mode == WB_SYNC_ALL ? WRITE_SYNC : WRITE);
L
Linus Torvalds 已提交
1712

1713
	head = create_page_buffers(page, inode,
L
Linus Torvalds 已提交
1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726
					(1 << BH_Dirty)|(1 << BH_Uptodate));

	/*
	 * Be very careful.  We have no exclusion from __set_page_dirty_buffers
	 * here, and the (potentially unmapped) buffers may become dirty at
	 * any time.  If a buffer becomes dirty here after we've inspected it
	 * then we just miss that fact, and the page stays dirty.
	 *
	 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
	 * handle that here by just cleaning them.
	 */

	bh = head;
1727 1728 1729 1730 1731
	blocksize = bh->b_size;
	bbits = block_size_bits(blocksize);

	block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
	last_block = (i_size_read(inode) - 1) >> bbits;
L
Linus Torvalds 已提交
1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748

	/*
	 * Get all the dirty buffers mapped to disk addresses and
	 * handle any aliases from the underlying blockdev's mapping.
	 */
	do {
		if (block > last_block) {
			/*
			 * mapped buffers outside i_size will occur, because
			 * this page can be outside i_size when there is a
			 * truncate in progress.
			 */
			/*
			 * The buffer was zeroed by block_write_full_page()
			 */
			clear_buffer_dirty(bh);
			set_buffer_uptodate(bh);
1749 1750
		} else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
			   buffer_dirty(bh)) {
1751
			WARN_ON(bh->b_size != blocksize);
L
Linus Torvalds 已提交
1752 1753 1754
			err = get_block(inode, block, bh, 1);
			if (err)
				goto recover;
1755
			clear_buffer_delay(bh);
L
Linus Torvalds 已提交
1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772
			if (buffer_new(bh)) {
				/* blockdev mappings never come here */
				clear_buffer_new(bh);
				unmap_underlying_metadata(bh->b_bdev,
							bh->b_blocknr);
			}
		}
		bh = bh->b_this_page;
		block++;
	} while (bh != head);

	do {
		if (!buffer_mapped(bh))
			continue;
		/*
		 * If it's a fully non-blocking write attempt and we cannot
		 * lock the buffer then redirty the page.  Note that this can
1773 1774 1775
		 * potentially cause a busy-wait loop from writeback threads
		 * and kswapd activity, but those code paths have their own
		 * higher-level throttling.
L
Linus Torvalds 已提交
1776
		 */
1777
		if (wbc->sync_mode != WB_SYNC_NONE) {
L
Linus Torvalds 已提交
1778
			lock_buffer(bh);
N
Nick Piggin 已提交
1779
		} else if (!trylock_buffer(bh)) {
L
Linus Torvalds 已提交
1780 1781 1782 1783
			redirty_page_for_writepage(wbc, page);
			continue;
		}
		if (test_clear_buffer_dirty(bh)) {
1784
			mark_buffer_async_write_endio(bh, handler);
L
Linus Torvalds 已提交
1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799
		} else {
			unlock_buffer(bh);
		}
	} while ((bh = bh->b_this_page) != head);

	/*
	 * The page and its buffers are protected by PageWriteback(), so we can
	 * drop the bh refcounts early.
	 */
	BUG_ON(PageWriteback(page));
	set_page_writeback(page);

	do {
		struct buffer_head *next = bh->b_this_page;
		if (buffer_async_write(bh)) {
1800
			submit_bh_wbc(write_op, bh, 0, wbc);
L
Linus Torvalds 已提交
1801 1802 1803 1804
			nr_underway++;
		}
		bh = next;
	} while (bh != head);
1805
	unlock_page(page);
L
Linus Torvalds 已提交
1806 1807 1808 1809 1810 1811 1812 1813 1814 1815

	err = 0;
done:
	if (nr_underway == 0) {
		/*
		 * The page was marked dirty, but the buffers were
		 * clean.  Someone wrote them back by hand with
		 * ll_rw_block/submit_bh.  A rare case.
		 */
		end_page_writeback(page);
1816

L
Linus Torvalds 已提交
1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833
		/*
		 * The page and buffer_heads can be released at any time from
		 * here on.
		 */
	}
	return err;

recover:
	/*
	 * ENOSPC, or some other error.  We may already have added some
	 * blocks to the file, so we need to write these out to avoid
	 * exposing stale data.
	 * The page is currently locked and not marked for writeback
	 */
	bh = head;
	/* Recovery: lock and submit the mapped buffers */
	do {
1834 1835
		if (buffer_mapped(bh) && buffer_dirty(bh) &&
		    !buffer_delay(bh)) {
L
Linus Torvalds 已提交
1836
			lock_buffer(bh);
1837
			mark_buffer_async_write_endio(bh, handler);
L
Linus Torvalds 已提交
1838 1839 1840 1841 1842 1843 1844 1845 1846 1847
		} else {
			/*
			 * The buffer may have been set dirty during
			 * attachment to a dirty page.
			 */
			clear_buffer_dirty(bh);
		}
	} while ((bh = bh->b_this_page) != head);
	SetPageError(page);
	BUG_ON(PageWriteback(page));
1848
	mapping_set_error(page->mapping, err);
L
Linus Torvalds 已提交
1849 1850 1851 1852 1853
	set_page_writeback(page);
	do {
		struct buffer_head *next = bh->b_this_page;
		if (buffer_async_write(bh)) {
			clear_buffer_dirty(bh);
1854
			submit_bh_wbc(write_op, bh, 0, wbc);
L
Linus Torvalds 已提交
1855 1856 1857 1858
			nr_underway++;
		}
		bh = next;
	} while (bh != head);
1859
	unlock_page(page);
L
Linus Torvalds 已提交
1860 1861 1862
	goto done;
}

1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889
/*
 * If a page has any new buffers, zero them out here, and mark them uptodate
 * and dirty so they'll be written out (in order to prevent uninitialised
 * block data from leaking). And clear the new bit.
 */
void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
{
	unsigned int block_start, block_end;
	struct buffer_head *head, *bh;

	BUG_ON(!PageLocked(page));
	if (!page_has_buffers(page))
		return;

	bh = head = page_buffers(page);
	block_start = 0;
	do {
		block_end = block_start + bh->b_size;

		if (buffer_new(bh)) {
			if (block_end > from && block_start < to) {
				if (!PageUptodate(page)) {
					unsigned start, size;

					start = max(from, block_start);
					size = min(to, block_end) - start;

1890
					zero_user(page, start, size);
1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904
					set_buffer_uptodate(bh);
				}

				clear_buffer_new(bh);
				mark_buffer_dirty(bh);
			}
		}

		block_start = block_end;
		bh = bh->b_this_page;
	} while (bh != head);
}
EXPORT_SYMBOL(page_zero_new_buffers);

C
Christoph Hellwig 已提交
1905
int __block_write_begin(struct page *page, loff_t pos, unsigned len,
1906
		get_block_t *get_block)
L
Linus Torvalds 已提交
1907
{
C
Christoph Hellwig 已提交
1908 1909
	unsigned from = pos & (PAGE_CACHE_SIZE - 1);
	unsigned to = from + len;
1910
	struct inode *inode = page->mapping->host;
L
Linus Torvalds 已提交
1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921
	unsigned block_start, block_end;
	sector_t block;
	int err = 0;
	unsigned blocksize, bbits;
	struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;

	BUG_ON(!PageLocked(page));
	BUG_ON(from > PAGE_CACHE_SIZE);
	BUG_ON(to > PAGE_CACHE_SIZE);
	BUG_ON(from > to);

1922 1923 1924
	head = create_page_buffers(page, inode, 0);
	blocksize = head->b_size;
	bbits = block_size_bits(blocksize);
L
Linus Torvalds 已提交
1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940

	block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);

	for(bh = head, block_start = 0; bh != head || !block_start;
	    block++, block_start=block_end, bh = bh->b_this_page) {
		block_end = block_start + blocksize;
		if (block_end <= from || block_start >= to) {
			if (PageUptodate(page)) {
				if (!buffer_uptodate(bh))
					set_buffer_uptodate(bh);
			}
			continue;
		}
		if (buffer_new(bh))
			clear_buffer_new(bh);
		if (!buffer_mapped(bh)) {
1941
			WARN_ON(bh->b_size != blocksize);
L
Linus Torvalds 已提交
1942 1943
			err = get_block(inode, block, bh, 1);
			if (err)
1944
				break;
L
Linus Torvalds 已提交
1945 1946 1947 1948
			if (buffer_new(bh)) {
				unmap_underlying_metadata(bh->b_bdev,
							bh->b_blocknr);
				if (PageUptodate(page)) {
N
Nick Piggin 已提交
1949
					clear_buffer_new(bh);
L
Linus Torvalds 已提交
1950
					set_buffer_uptodate(bh);
N
Nick Piggin 已提交
1951
					mark_buffer_dirty(bh);
L
Linus Torvalds 已提交
1952 1953
					continue;
				}
1954 1955 1956 1957
				if (block_end > to || block_start < from)
					zero_user_segments(page,
						to, block_end,
						block_start, from);
L
Linus Torvalds 已提交
1958 1959 1960 1961 1962 1963 1964 1965 1966
				continue;
			}
		}
		if (PageUptodate(page)) {
			if (!buffer_uptodate(bh))
				set_buffer_uptodate(bh);
			continue; 
		}
		if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
1967
		    !buffer_unwritten(bh) &&
L
Linus Torvalds 已提交
1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978
		     (block_start < from || block_end > to)) {
			ll_rw_block(READ, 1, &bh);
			*wait_bh++=bh;
		}
	}
	/*
	 * If we issued read requests - let them complete.
	 */
	while(wait_bh > wait) {
		wait_on_buffer(*--wait_bh);
		if (!buffer_uptodate(*wait_bh))
1979
			err = -EIO;
L
Linus Torvalds 已提交
1980
	}
1981
	if (unlikely(err))
1982
		page_zero_new_buffers(page, from, to);
L
Linus Torvalds 已提交
1983 1984
	return err;
}
C
Christoph Hellwig 已提交
1985
EXPORT_SYMBOL(__block_write_begin);
L
Linus Torvalds 已提交
1986 1987 1988 1989 1990 1991 1992 1993 1994

static int __block_commit_write(struct inode *inode, struct page *page,
		unsigned from, unsigned to)
{
	unsigned block_start, block_end;
	int partial = 0;
	unsigned blocksize;
	struct buffer_head *bh, *head;

1995 1996
	bh = head = page_buffers(page);
	blocksize = bh->b_size;
L
Linus Torvalds 已提交
1997

1998 1999
	block_start = 0;
	do {
L
Linus Torvalds 已提交
2000 2001 2002 2003 2004 2005 2006 2007
		block_end = block_start + blocksize;
		if (block_end <= from || block_start >= to) {
			if (!buffer_uptodate(bh))
				partial = 1;
		} else {
			set_buffer_uptodate(bh);
			mark_buffer_dirty(bh);
		}
2008
		clear_buffer_new(bh);
2009 2010 2011 2012

		block_start = block_end;
		bh = bh->b_this_page;
	} while (bh != head);
L
Linus Torvalds 已提交
2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024

	/*
	 * If this is a partial write which happened to make all buffers
	 * uptodate then we can optimize away a bogus readpage() for
	 * the next read(). Here we 'discover' whether the page went
	 * uptodate as a result of this (potentially partial) write.
	 */
	if (!partial)
		SetPageUptodate(page);
	return 0;
}

2025
/*
2026 2027 2028
 * block_write_begin takes care of the basic task of block allocation and
 * bringing partial write blocks uptodate first.
 *
2029
 * The filesystem needs to handle block truncation upon failure.
2030
 */
2031 2032
int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
		unsigned flags, struct page **pagep, get_block_t *get_block)
2033
{
2034
	pgoff_t index = pos >> PAGE_CACHE_SHIFT;
2035
	struct page *page;
2036
	int status;
2037

2038 2039 2040
	page = grab_cache_page_write_begin(mapping, index, flags);
	if (!page)
		return -ENOMEM;
2041

2042
	status = __block_write_begin(page, pos, len, get_block);
2043
	if (unlikely(status)) {
2044 2045 2046
		unlock_page(page);
		page_cache_release(page);
		page = NULL;
2047 2048
	}

2049
	*pagep = page;
2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094
	return status;
}
EXPORT_SYMBOL(block_write_begin);

int block_write_end(struct file *file, struct address_space *mapping,
			loff_t pos, unsigned len, unsigned copied,
			struct page *page, void *fsdata)
{
	struct inode *inode = mapping->host;
	unsigned start;

	start = pos & (PAGE_CACHE_SIZE - 1);

	if (unlikely(copied < len)) {
		/*
		 * The buffers that were written will now be uptodate, so we
		 * don't have to worry about a readpage reading them and
		 * overwriting a partial write. However if we have encountered
		 * a short write and only partially written into a buffer, it
		 * will not be marked uptodate, so a readpage might come in and
		 * destroy our partial write.
		 *
		 * Do the simplest thing, and just treat any short write to a
		 * non uptodate page as a zero-length write, and force the
		 * caller to redo the whole thing.
		 */
		if (!PageUptodate(page))
			copied = 0;

		page_zero_new_buffers(page, start+copied, start+len);
	}
	flush_dcache_page(page);

	/* This could be a short (even 0-length) commit */
	__block_commit_write(inode, page, start, start+copied);

	return copied;
}
EXPORT_SYMBOL(block_write_end);

int generic_write_end(struct file *file, struct address_space *mapping,
			loff_t pos, unsigned len, unsigned copied,
			struct page *page, void *fsdata)
{
	struct inode *inode = mapping->host;
2095
	loff_t old_size = inode->i_size;
2096
	int i_size_changed = 0;
2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108

	copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);

	/*
	 * No need to use i_size_read() here, the i_size
	 * cannot change under us because we hold i_mutex.
	 *
	 * But it's important to update i_size while still holding page lock:
	 * page writeout could otherwise come in and zero beyond i_size.
	 */
	if (pos+copied > inode->i_size) {
		i_size_write(inode, pos+copied);
2109
		i_size_changed = 1;
2110 2111 2112 2113 2114
	}

	unlock_page(page);
	page_cache_release(page);

2115 2116
	if (old_size < pos)
		pagecache_isize_extended(inode, old_size, pos);
2117 2118 2119 2120 2121 2122 2123 2124 2125
	/*
	 * Don't mark the inode dirty under page lock. First, it unnecessarily
	 * makes the holding time of page lock longer. Second, it forces lock
	 * ordering of page lock and transaction start for journaling
	 * filesystems.
	 */
	if (i_size_changed)
		mark_inode_dirty(inode);

2126 2127 2128 2129
	return copied;
}
EXPORT_SYMBOL(generic_write_end);

2130 2131 2132 2133 2134 2135 2136
/*
 * block_is_partially_uptodate checks whether buffers within a page are
 * uptodate or not.
 *
 * Returns true if all buffers which correspond to a file portion
 * we want to read are uptodate.
 */
2137 2138
int block_is_partially_uptodate(struct page *page, unsigned long from,
					unsigned long count)
2139 2140 2141 2142 2143 2144 2145 2146 2147
{
	unsigned block_start, block_end, blocksize;
	unsigned to;
	struct buffer_head *bh, *head;
	int ret = 1;

	if (!page_has_buffers(page))
		return 0;

2148 2149
	head = page_buffers(page);
	blocksize = head->b_size;
2150
	to = min_t(unsigned, PAGE_CACHE_SIZE - from, count);
2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174
	to = from + to;
	if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize)
		return 0;

	bh = head;
	block_start = 0;
	do {
		block_end = block_start + blocksize;
		if (block_end > from && block_start < to) {
			if (!buffer_uptodate(bh)) {
				ret = 0;
				break;
			}
			if (block_end >= to)
				break;
		}
		block_start = block_end;
		bh = bh->b_this_page;
	} while (bh != head);

	return ret;
}
EXPORT_SYMBOL(block_is_partially_uptodate);

L
Linus Torvalds 已提交
2175 2176 2177 2178 2179 2180 2181 2182 2183 2184 2185 2186
/*
 * Generic "read page" function for block devices that have the normal
 * get_block functionality. This is most of the block device filesystems.
 * Reads the page asynchronously --- the unlock_buffer() and
 * set/clear_buffer_uptodate() functions propagate buffer state into the
 * page struct once IO has completed.
 */
int block_read_full_page(struct page *page, get_block_t *get_block)
{
	struct inode *inode = page->mapping->host;
	sector_t iblock, lblock;
	struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2187
	unsigned int blocksize, bbits;
L
Linus Torvalds 已提交
2188 2189 2190
	int nr, i;
	int fully_mapped = 1;

2191 2192 2193
	head = create_page_buffers(page, inode, 0);
	blocksize = head->b_size;
	bbits = block_size_bits(blocksize);
L
Linus Torvalds 已提交
2194

2195 2196
	iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
	lblock = (i_size_read(inode)+blocksize-1) >> bbits;
L
Linus Torvalds 已提交
2197 2198 2199 2200 2201 2202 2203 2204 2205
	bh = head;
	nr = 0;
	i = 0;

	do {
		if (buffer_uptodate(bh))
			continue;

		if (!buffer_mapped(bh)) {
2206 2207
			int err = 0;

L
Linus Torvalds 已提交
2208 2209
			fully_mapped = 0;
			if (iblock < lblock) {
2210
				WARN_ON(bh->b_size != blocksize);
2211 2212
				err = get_block(inode, iblock, bh, 0);
				if (err)
L
Linus Torvalds 已提交
2213 2214 2215
					SetPageError(page);
			}
			if (!buffer_mapped(bh)) {
2216
				zero_user(page, i * blocksize, blocksize);
2217 2218
				if (!err)
					set_buffer_uptodate(bh);
L
Linus Torvalds 已提交
2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265
				continue;
			}
			/*
			 * get_block() might have updated the buffer
			 * synchronously
			 */
			if (buffer_uptodate(bh))
				continue;
		}
		arr[nr++] = bh;
	} while (i++, iblock++, (bh = bh->b_this_page) != head);

	if (fully_mapped)
		SetPageMappedToDisk(page);

	if (!nr) {
		/*
		 * All buffers are uptodate - we can set the page uptodate
		 * as well. But not if get_block() returned an error.
		 */
		if (!PageError(page))
			SetPageUptodate(page);
		unlock_page(page);
		return 0;
	}

	/* Stage two: lock the buffers */
	for (i = 0; i < nr; i++) {
		bh = arr[i];
		lock_buffer(bh);
		mark_buffer_async_read(bh);
	}

	/*
	 * Stage 3: start the IO.  Check for uptodateness
	 * inside the buffer lock in case another process reading
	 * the underlying blockdev brought it uptodate (the sct fix).
	 */
	for (i = 0; i < nr; i++) {
		bh = arr[i];
		if (buffer_uptodate(bh))
			end_buffer_async_read(bh, 1);
		else
			submit_bh(READ, bh);
	}
	return 0;
}
2266
EXPORT_SYMBOL(block_read_full_page);
L
Linus Torvalds 已提交
2267 2268

/* utility function for filesystems that need to do work on expanding
N
Nick Piggin 已提交
2269
 * truncates.  Uses filesystem pagecache writes to allow the filesystem to
L
Linus Torvalds 已提交
2270 2271
 * deal with the hole.  
 */
N
Nick Piggin 已提交
2272
int generic_cont_expand_simple(struct inode *inode, loff_t size)
L
Linus Torvalds 已提交
2273 2274 2275
{
	struct address_space *mapping = inode->i_mapping;
	struct page *page;
N
Nick Piggin 已提交
2276
	void *fsdata;
L
Linus Torvalds 已提交
2277 2278
	int err;

N
npiggin@suse.de 已提交
2279 2280
	err = inode_newsize_ok(inode, size);
	if (err)
L
Linus Torvalds 已提交
2281 2282
		goto out;

N
Nick Piggin 已提交
2283 2284 2285 2286
	err = pagecache_write_begin(NULL, mapping, size, 0,
				AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND,
				&page, &fsdata);
	if (err)
2287 2288
		goto out;

N
Nick Piggin 已提交
2289 2290
	err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
	BUG_ON(err > 0);
2291

L
Linus Torvalds 已提交
2292 2293 2294
out:
	return err;
}
2295
EXPORT_SYMBOL(generic_cont_expand_simple);
L
Linus Torvalds 已提交
2296

2297 2298
static int cont_expand_zero(struct file *file, struct address_space *mapping,
			    loff_t pos, loff_t *bytes)
L
Linus Torvalds 已提交
2299 2300 2301
{
	struct inode *inode = mapping->host;
	unsigned blocksize = 1 << inode->i_blkbits;
N
Nick Piggin 已提交
2302 2303 2304 2305 2306 2307
	struct page *page;
	void *fsdata;
	pgoff_t index, curidx;
	loff_t curpos;
	unsigned zerofrom, offset, len;
	int err = 0;
L
Linus Torvalds 已提交
2308

N
Nick Piggin 已提交
2309 2310 2311 2312 2313
	index = pos >> PAGE_CACHE_SHIFT;
	offset = pos & ~PAGE_CACHE_MASK;

	while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) {
		zerofrom = curpos & ~PAGE_CACHE_MASK;
L
Linus Torvalds 已提交
2314 2315 2316 2317
		if (zerofrom & (blocksize-1)) {
			*bytes |= (blocksize-1);
			(*bytes)++;
		}
N
Nick Piggin 已提交
2318
		len = PAGE_CACHE_SIZE - zerofrom;
L
Linus Torvalds 已提交
2319

N
Nick Piggin 已提交
2320 2321 2322 2323 2324
		err = pagecache_write_begin(file, mapping, curpos, len,
						AOP_FLAG_UNINTERRUPTIBLE,
						&page, &fsdata);
		if (err)
			goto out;
2325
		zero_user(page, zerofrom, len);
N
Nick Piggin 已提交
2326 2327 2328 2329 2330 2331
		err = pagecache_write_end(file, mapping, curpos, len, len,
						page, fsdata);
		if (err < 0)
			goto out;
		BUG_ON(err != len);
		err = 0;
2332 2333

		balance_dirty_pages_ratelimited(mapping);
2334 2335 2336 2337 2338

		if (unlikely(fatal_signal_pending(current))) {
			err = -EINTR;
			goto out;
		}
N
Nick Piggin 已提交
2339
	}
L
Linus Torvalds 已提交
2340

N
Nick Piggin 已提交
2341 2342 2343
	/* page covers the boundary, find the boundary offset */
	if (index == curidx) {
		zerofrom = curpos & ~PAGE_CACHE_MASK;
L
Linus Torvalds 已提交
2344
		/* if we will expand the thing last block will be filled */
N
Nick Piggin 已提交
2345 2346 2347 2348
		if (offset <= zerofrom) {
			goto out;
		}
		if (zerofrom & (blocksize-1)) {
L
Linus Torvalds 已提交
2349 2350 2351
			*bytes |= (blocksize-1);
			(*bytes)++;
		}
N
Nick Piggin 已提交
2352
		len = offset - zerofrom;
L
Linus Torvalds 已提交
2353

N
Nick Piggin 已提交
2354 2355 2356 2357 2358
		err = pagecache_write_begin(file, mapping, curpos, len,
						AOP_FLAG_UNINTERRUPTIBLE,
						&page, &fsdata);
		if (err)
			goto out;
2359
		zero_user(page, zerofrom, len);
N
Nick Piggin 已提交
2360 2361 2362 2363 2364 2365
		err = pagecache_write_end(file, mapping, curpos, len, len,
						page, fsdata);
		if (err < 0)
			goto out;
		BUG_ON(err != len);
		err = 0;
L
Linus Torvalds 已提交
2366
	}
N
Nick Piggin 已提交
2367 2368 2369 2370 2371 2372 2373 2374
out:
	return err;
}

/*
 * For moronic filesystems that do not allow holes in file.
 * We may have to extend the file.
 */
2375
int cont_write_begin(struct file *file, struct address_space *mapping,
N
Nick Piggin 已提交
2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386
			loff_t pos, unsigned len, unsigned flags,
			struct page **pagep, void **fsdata,
			get_block_t *get_block, loff_t *bytes)
{
	struct inode *inode = mapping->host;
	unsigned blocksize = 1 << inode->i_blkbits;
	unsigned zerofrom;
	int err;

	err = cont_expand_zero(file, mapping, pos, bytes);
	if (err)
2387
		return err;
N
Nick Piggin 已提交
2388 2389 2390 2391 2392

	zerofrom = *bytes & ~PAGE_CACHE_MASK;
	if (pos+len > *bytes && zerofrom & (blocksize-1)) {
		*bytes |= (blocksize-1);
		(*bytes)++;
L
Linus Torvalds 已提交
2393 2394
	}

2395
	return block_write_begin(mapping, pos, len, flags, pagep, get_block);
L
Linus Torvalds 已提交
2396
}
2397
EXPORT_SYMBOL(cont_write_begin);
L
Linus Torvalds 已提交
2398 2399 2400 2401 2402 2403 2404

int block_commit_write(struct page *page, unsigned from, unsigned to)
{
	struct inode *inode = page->mapping->host;
	__block_commit_write(inode,page,from,to);
	return 0;
}
2405
EXPORT_SYMBOL(block_commit_write);
L
Linus Torvalds 已提交
2406

2407 2408 2409 2410 2411 2412 2413 2414 2415 2416
/*
 * block_page_mkwrite() is not allowed to change the file size as it gets
 * called from a page fault handler when a page is first dirtied. Hence we must
 * be careful to check for EOF conditions here. We set the page up correctly
 * for a written page which means we get ENOSPC checking when writing into
 * holes and correct delalloc and unwritten extent mapping on filesystems that
 * support these features.
 *
 * We are not allowed to take the i_mutex here so we have to play games to
 * protect against truncate races as the page could now be beyond EOF.  Because
2417
 * truncate writes the inode size before removing pages, once we have the
2418 2419 2420
 * page lock we can determine safely if the page is beyond EOF. If it is not
 * beyond EOF, then the page is guaranteed safe against truncation until we
 * unlock the page.
2421
 *
2422 2423
 * Direct callers of this function should protect against filesystem freezing
 * using sb_start_write() - sb_end_write() functions.
2424
 */
2425 2426
int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
			 get_block_t get_block)
2427
{
2428
	struct page *page = vmf->page;
A
Al Viro 已提交
2429
	struct inode *inode = file_inode(vma->vm_file);
2430 2431
	unsigned long end;
	loff_t size;
2432
	int ret;
2433 2434 2435 2436

	lock_page(page);
	size = i_size_read(inode);
	if ((page->mapping != inode->i_mapping) ||
N
Nick Piggin 已提交
2437
	    (page_offset(page) > size)) {
2438 2439 2440
		/* We overload EFAULT to mean page got truncated */
		ret = -EFAULT;
		goto out_unlock;
2441 2442 2443 2444 2445 2446 2447 2448
	}

	/* page is wholly or partially inside EOF */
	if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
		end = size & ~PAGE_CACHE_MASK;
	else
		end = PAGE_CACHE_SIZE;

C
Christoph Hellwig 已提交
2449
	ret = __block_write_begin(page, 0, end, get_block);
2450 2451 2452
	if (!ret)
		ret = block_commit_write(page, 0, end);

2453 2454
	if (unlikely(ret < 0))
		goto out_unlock;
2455
	set_page_dirty(page);
2456
	wait_for_stable_page(page);
2457 2458 2459
	return 0;
out_unlock:
	unlock_page(page);
2460
	return ret;
2461 2462 2463 2464 2465 2466
}
EXPORT_SYMBOL(__block_page_mkwrite);

int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
		   get_block_t get_block)
{
2467
	int ret;
A
Al Viro 已提交
2468
	struct super_block *sb = file_inode(vma->vm_file)->i_sb;
2469

2470
	sb_start_pagefault(sb);
2471 2472 2473 2474 2475 2476 2477

	/*
	 * Update file times before taking page lock. We may end up failing the
	 * fault so this update may be superfluous but who really cares...
	 */
	file_update_time(vma->vm_file);

2478
	ret = __block_page_mkwrite(vma, vmf, get_block);
2479
	sb_end_pagefault(sb);
2480
	return block_page_mkwrite_return(ret);
2481
}
2482
EXPORT_SYMBOL(block_page_mkwrite);
L
Linus Torvalds 已提交
2483 2484

/*
N
Nick Piggin 已提交
2485
 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
L
Linus Torvalds 已提交
2486 2487 2488 2489 2490
 * immediately, while under the page lock.  So it needs a special end_io
 * handler which does not touch the bh after unlocking it.
 */
static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
{
2491
	__end_buffer_read_notouch(bh, uptodate);
L
Linus Torvalds 已提交
2492 2493
}

N
Nick Piggin 已提交
2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517
/*
 * Attach the singly-linked list of buffers created by nobh_write_begin, to
 * the page (converting it to circular linked list and taking care of page
 * dirty races).
 */
static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
{
	struct buffer_head *bh;

	BUG_ON(!PageLocked(page));

	spin_lock(&page->mapping->private_lock);
	bh = head;
	do {
		if (PageDirty(page))
			set_buffer_dirty(bh);
		if (!bh->b_this_page)
			bh->b_this_page = head;
		bh = bh->b_this_page;
	} while (bh != head);
	attach_page_buffers(page, head);
	spin_unlock(&page->mapping->private_lock);
}

L
Linus Torvalds 已提交
2518
/*
2519 2520
 * On entry, the page is fully not uptodate.
 * On exit the page is fully uptodate in the areas outside (from,to)
2521
 * The filesystem needs to handle block truncation upon failure.
L
Linus Torvalds 已提交
2522
 */
2523
int nobh_write_begin(struct address_space *mapping,
N
Nick Piggin 已提交
2524 2525
			loff_t pos, unsigned len, unsigned flags,
			struct page **pagep, void **fsdata,
L
Linus Torvalds 已提交
2526 2527
			get_block_t *get_block)
{
N
Nick Piggin 已提交
2528
	struct inode *inode = mapping->host;
L
Linus Torvalds 已提交
2529 2530
	const unsigned blkbits = inode->i_blkbits;
	const unsigned blocksize = 1 << blkbits;
N
Nick Piggin 已提交
2531
	struct buffer_head *head, *bh;
N
Nick Piggin 已提交
2532 2533 2534
	struct page *page;
	pgoff_t index;
	unsigned from, to;
L
Linus Torvalds 已提交
2535
	unsigned block_in_page;
N
Nick Piggin 已提交
2536
	unsigned block_start, block_end;
L
Linus Torvalds 已提交
2537 2538 2539 2540 2541
	sector_t block_in_file;
	int nr_reads = 0;
	int ret = 0;
	int is_mapped_to_disk = 1;

N
Nick Piggin 已提交
2542 2543 2544 2545
	index = pos >> PAGE_CACHE_SHIFT;
	from = pos & (PAGE_CACHE_SIZE - 1);
	to = from + len;

2546
	page = grab_cache_page_write_begin(mapping, index, flags);
N
Nick Piggin 已提交
2547 2548 2549 2550 2551 2552
	if (!page)
		return -ENOMEM;
	*pagep = page;
	*fsdata = NULL;

	if (page_has_buffers(page)) {
2553 2554 2555 2556
		ret = __block_write_begin(page, pos, len, get_block);
		if (unlikely(ret))
			goto out_release;
		return ret;
N
Nick Piggin 已提交
2557
	}
N
Nick Piggin 已提交
2558

L
Linus Torvalds 已提交
2559 2560 2561
	if (PageMappedToDisk(page))
		return 0;

N
Nick Piggin 已提交
2562 2563 2564 2565 2566 2567 2568 2569 2570 2571
	/*
	 * Allocate buffers so that we can keep track of state, and potentially
	 * attach them to the page if an error occurs. In the common case of
	 * no error, they will just be freed again without ever being attached
	 * to the page (which is all OK, because we're under the page lock).
	 *
	 * Be careful: the buffer linked list is a NULL terminated one, rather
	 * than the circular one we're used to.
	 */
	head = alloc_page_buffers(page, blocksize, 0);
N
Nick Piggin 已提交
2572 2573 2574 2575
	if (!head) {
		ret = -ENOMEM;
		goto out_release;
	}
N
Nick Piggin 已提交
2576

L
Linus Torvalds 已提交
2577 2578 2579 2580 2581 2582 2583
	block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);

	/*
	 * We loop across all blocks in the page, whether or not they are
	 * part of the affected region.  This is so we can discover if the
	 * page is fully mapped-to-disk.
	 */
N
Nick Piggin 已提交
2584
	for (block_start = 0, block_in_page = 0, bh = head;
L
Linus Torvalds 已提交
2585
		  block_start < PAGE_CACHE_SIZE;
N
Nick Piggin 已提交
2586
		  block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
L
Linus Torvalds 已提交
2587 2588
		int create;

N
Nick Piggin 已提交
2589 2590
		block_end = block_start + blocksize;
		bh->b_state = 0;
L
Linus Torvalds 已提交
2591 2592 2593 2594
		create = 1;
		if (block_start >= to)
			create = 0;
		ret = get_block(inode, block_in_file + block_in_page,
N
Nick Piggin 已提交
2595
					bh, create);
L
Linus Torvalds 已提交
2596 2597
		if (ret)
			goto failed;
N
Nick Piggin 已提交
2598
		if (!buffer_mapped(bh))
L
Linus Torvalds 已提交
2599
			is_mapped_to_disk = 0;
N
Nick Piggin 已提交
2600 2601 2602 2603
		if (buffer_new(bh))
			unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
		if (PageUptodate(page)) {
			set_buffer_uptodate(bh);
L
Linus Torvalds 已提交
2604
			continue;
N
Nick Piggin 已提交
2605 2606
		}
		if (buffer_new(bh) || !buffer_mapped(bh)) {
2607 2608
			zero_user_segments(page, block_start, from,
							to, block_end);
L
Linus Torvalds 已提交
2609 2610
			continue;
		}
N
Nick Piggin 已提交
2611
		if (buffer_uptodate(bh))
L
Linus Torvalds 已提交
2612 2613
			continue;	/* reiserfs does this */
		if (block_start < from || block_end > to) {
N
Nick Piggin 已提交
2614 2615 2616 2617
			lock_buffer(bh);
			bh->b_end_io = end_buffer_read_nobh;
			submit_bh(READ, bh);
			nr_reads++;
L
Linus Torvalds 已提交
2618 2619 2620 2621 2622 2623 2624 2625 2626
		}
	}

	if (nr_reads) {
		/*
		 * The page is locked, so these buffers are protected from
		 * any VM or truncate activity.  Hence we don't need to care
		 * for the buffer_head refcounts.
		 */
N
Nick Piggin 已提交
2627
		for (bh = head; bh; bh = bh->b_this_page) {
L
Linus Torvalds 已提交
2628 2629 2630 2631 2632 2633 2634 2635 2636 2637 2638
			wait_on_buffer(bh);
			if (!buffer_uptodate(bh))
				ret = -EIO;
		}
		if (ret)
			goto failed;
	}

	if (is_mapped_to_disk)
		SetPageMappedToDisk(page);

N
Nick Piggin 已提交
2639
	*fsdata = head; /* to be released by nobh_write_end */
N
Nick Piggin 已提交
2640

L
Linus Torvalds 已提交
2641 2642 2643
	return 0;

failed:
N
Nick Piggin 已提交
2644
	BUG_ON(!ret);
L
Linus Torvalds 已提交
2645
	/*
N
Nick Piggin 已提交
2646 2647 2648 2649 2650
	 * Error recovery is a bit difficult. We need to zero out blocks that
	 * were newly allocated, and dirty them to ensure they get written out.
	 * Buffers need to be attached to the page at this point, otherwise
	 * the handling of potential IO errors during writeout would be hard
	 * (could try doing synchronous writeout, but what if that fails too?)
L
Linus Torvalds 已提交
2651
	 */
N
Nick Piggin 已提交
2652 2653
	attach_nobh_buffers(page, head);
	page_zero_new_buffers(page, from, to);
N
Nick Piggin 已提交
2654

N
Nick Piggin 已提交
2655 2656 2657 2658
out_release:
	unlock_page(page);
	page_cache_release(page);
	*pagep = NULL;
N
Nick Piggin 已提交
2659

2660 2661
	return ret;
}
N
Nick Piggin 已提交
2662
EXPORT_SYMBOL(nobh_write_begin);
L
Linus Torvalds 已提交
2663

N
Nick Piggin 已提交
2664 2665 2666
int nobh_write_end(struct file *file, struct address_space *mapping,
			loff_t pos, unsigned len, unsigned copied,
			struct page *page, void *fsdata)
L
Linus Torvalds 已提交
2667 2668
{
	struct inode *inode = page->mapping->host;
N
Nick Piggin 已提交
2669
	struct buffer_head *head = fsdata;
N
Nick Piggin 已提交
2670
	struct buffer_head *bh;
2671
	BUG_ON(fsdata != NULL && page_has_buffers(page));
L
Linus Torvalds 已提交
2672

2673
	if (unlikely(copied < len) && head)
2674 2675 2676 2677
		attach_nobh_buffers(page, head);
	if (page_has_buffers(page))
		return generic_write_end(file, mapping, pos, len,
					copied, page, fsdata);
N
Nick Piggin 已提交
2678

N
Nick Piggin 已提交
2679
	SetPageUptodate(page);
L
Linus Torvalds 已提交
2680
	set_page_dirty(page);
N
Nick Piggin 已提交
2681 2682
	if (pos+copied > inode->i_size) {
		i_size_write(inode, pos+copied);
L
Linus Torvalds 已提交
2683 2684
		mark_inode_dirty(inode);
	}
N
Nick Piggin 已提交
2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695

	unlock_page(page);
	page_cache_release(page);

	while (head) {
		bh = head;
		head = head->b_this_page;
		free_buffer_head(bh);
	}

	return copied;
L
Linus Torvalds 已提交
2696
}
N
Nick Piggin 已提交
2697
EXPORT_SYMBOL(nobh_write_end);
L
Linus Torvalds 已提交
2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713 2714 2715 2716 2717 2718 2719 2720 2721 2722 2723 2724 2725 2726 2727 2728 2729 2730 2731 2732 2733 2734 2735 2736 2737 2738 2739 2740

/*
 * nobh_writepage() - based on block_full_write_page() except
 * that it tries to operate without attaching bufferheads to
 * the page.
 */
int nobh_writepage(struct page *page, get_block_t *get_block,
			struct writeback_control *wbc)
{
	struct inode * const inode = page->mapping->host;
	loff_t i_size = i_size_read(inode);
	const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
	unsigned offset;
	int ret;

	/* Is the page fully inside i_size? */
	if (page->index < end_index)
		goto out;

	/* Is the page fully outside i_size? (truncate in progress) */
	offset = i_size & (PAGE_CACHE_SIZE-1);
	if (page->index >= end_index+1 || !offset) {
		/*
		 * The page may have dirty, unmapped buffers.  For example,
		 * they may have been added in ext3_writepage().  Make them
		 * freeable here, so the page does not leak.
		 */
#if 0
		/* Not really sure about this  - do we need this ? */
		if (page->mapping->a_ops->invalidatepage)
			page->mapping->a_ops->invalidatepage(page, offset);
#endif
		unlock_page(page);
		return 0; /* don't care */
	}

	/*
	 * The page straddles i_size.  It must be zeroed out on each and every
	 * writepage invocation because it may be mmapped.  "A file is mapped
	 * in multiples of the page size.  For a file that is not a multiple of
	 * the  page size, the remaining memory is zeroed when mapped, and
	 * writes to that region are not written out to the file."
	 */
2741
	zero_user_segment(page, offset, PAGE_CACHE_SIZE);
L
Linus Torvalds 已提交
2742 2743 2744
out:
	ret = mpage_writepage(page, get_block, wbc);
	if (ret == -EAGAIN)
2745 2746
		ret = __block_write_full_page(inode, page, get_block, wbc,
					      end_buffer_async_write);
L
Linus Torvalds 已提交
2747 2748 2749 2750
	return ret;
}
EXPORT_SYMBOL(nobh_writepage);

N
Nick Piggin 已提交
2751 2752
int nobh_truncate_page(struct address_space *mapping,
			loff_t from, get_block_t *get_block)
L
Linus Torvalds 已提交
2753 2754 2755
{
	pgoff_t index = from >> PAGE_CACHE_SHIFT;
	unsigned offset = from & (PAGE_CACHE_SIZE-1);
N
Nick Piggin 已提交
2756 2757 2758 2759
	unsigned blocksize;
	sector_t iblock;
	unsigned length, pos;
	struct inode *inode = mapping->host;
L
Linus Torvalds 已提交
2760
	struct page *page;
N
Nick Piggin 已提交
2761 2762
	struct buffer_head map_bh;
	int err;
L
Linus Torvalds 已提交
2763

N
Nick Piggin 已提交
2764 2765 2766 2767 2768 2769 2770 2771 2772
	blocksize = 1 << inode->i_blkbits;
	length = offset & (blocksize - 1);

	/* Block boundary? Nothing to do */
	if (!length)
		return 0;

	length = blocksize - length;
	iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
L
Linus Torvalds 已提交
2773 2774

	page = grab_cache_page(mapping, index);
N
Nick Piggin 已提交
2775
	err = -ENOMEM;
L
Linus Torvalds 已提交
2776 2777 2778
	if (!page)
		goto out;

N
Nick Piggin 已提交
2779 2780 2781 2782 2783 2784 2785 2786 2787 2788 2789 2790 2791 2792
	if (page_has_buffers(page)) {
has_buffers:
		unlock_page(page);
		page_cache_release(page);
		return block_truncate_page(mapping, from, get_block);
	}

	/* Find the buffer that contains "offset" */
	pos = blocksize;
	while (offset >= pos) {
		iblock++;
		pos += blocksize;
	}

2793 2794
	map_bh.b_size = blocksize;
	map_bh.b_state = 0;
N
Nick Piggin 已提交
2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809 2810 2811 2812 2813 2814 2815
	err = get_block(inode, iblock, &map_bh, 0);
	if (err)
		goto unlock;
	/* unmapped? It's a hole - nothing to do */
	if (!buffer_mapped(&map_bh))
		goto unlock;

	/* Ok, it's mapped. Make sure it's up-to-date */
	if (!PageUptodate(page)) {
		err = mapping->a_ops->readpage(NULL, page);
		if (err) {
			page_cache_release(page);
			goto out;
		}
		lock_page(page);
		if (!PageUptodate(page)) {
			err = -EIO;
			goto unlock;
		}
		if (page_has_buffers(page))
			goto has_buffers;
L
Linus Torvalds 已提交
2816
	}
2817
	zero_user(page, offset, length);
N
Nick Piggin 已提交
2818 2819 2820 2821
	set_page_dirty(page);
	err = 0;

unlock:
L
Linus Torvalds 已提交
2822 2823 2824
	unlock_page(page);
	page_cache_release(page);
out:
N
Nick Piggin 已提交
2825
	return err;
L
Linus Torvalds 已提交
2826 2827 2828 2829 2830 2831 2832 2833 2834
}
EXPORT_SYMBOL(nobh_truncate_page);

int block_truncate_page(struct address_space *mapping,
			loff_t from, get_block_t *get_block)
{
	pgoff_t index = from >> PAGE_CACHE_SHIFT;
	unsigned offset = from & (PAGE_CACHE_SIZE-1);
	unsigned blocksize;
2835
	sector_t iblock;
L
Linus Torvalds 已提交
2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849
	unsigned length, pos;
	struct inode *inode = mapping->host;
	struct page *page;
	struct buffer_head *bh;
	int err;

	blocksize = 1 << inode->i_blkbits;
	length = offset & (blocksize - 1);

	/* Block boundary? Nothing to do */
	if (!length)
		return 0;

	length = blocksize - length;
2850
	iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
L
Linus Torvalds 已提交
2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870
	
	page = grab_cache_page(mapping, index);
	err = -ENOMEM;
	if (!page)
		goto out;

	if (!page_has_buffers(page))
		create_empty_buffers(page, blocksize, 0);

	/* Find the buffer that contains "offset" */
	bh = page_buffers(page);
	pos = blocksize;
	while (offset >= pos) {
		bh = bh->b_this_page;
		iblock++;
		pos += blocksize;
	}

	err = 0;
	if (!buffer_mapped(bh)) {
2871
		WARN_ON(bh->b_size != blocksize);
L
Linus Torvalds 已提交
2872 2873 2874 2875 2876 2877 2878 2879 2880 2881 2882 2883
		err = get_block(inode, iblock, bh, 0);
		if (err)
			goto unlock;
		/* unmapped? It's a hole - nothing to do */
		if (!buffer_mapped(bh))
			goto unlock;
	}

	/* Ok, it's mapped. Make sure it's up-to-date */
	if (PageUptodate(page))
		set_buffer_uptodate(bh);

2884
	if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
L
Linus Torvalds 已提交
2885 2886 2887 2888 2889 2890 2891 2892
		err = -EIO;
		ll_rw_block(READ, 1, &bh);
		wait_on_buffer(bh);
		/* Uhhuh. Read error. Complain and punt. */
		if (!buffer_uptodate(bh))
			goto unlock;
	}

2893
	zero_user(page, offset, length);
L
Linus Torvalds 已提交
2894 2895 2896 2897 2898 2899 2900 2901 2902
	mark_buffer_dirty(bh);
	err = 0;

unlock:
	unlock_page(page);
	page_cache_release(page);
out:
	return err;
}
2903
EXPORT_SYMBOL(block_truncate_page);
L
Linus Torvalds 已提交
2904 2905 2906 2907

/*
 * The generic ->writepage function for buffer-backed address_spaces
 */
2908 2909
int block_write_full_page(struct page *page, get_block_t *get_block,
			struct writeback_control *wbc)
L
Linus Torvalds 已提交
2910 2911 2912 2913 2914 2915 2916 2917
{
	struct inode * const inode = page->mapping->host;
	loff_t i_size = i_size_read(inode);
	const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
	unsigned offset;

	/* Is the page fully inside i_size? */
	if (page->index < end_index)
2918
		return __block_write_full_page(inode, page, get_block, wbc,
2919
					       end_buffer_async_write);
L
Linus Torvalds 已提交
2920 2921 2922 2923 2924 2925 2926 2927 2928

	/* Is the page fully outside i_size? (truncate in progress) */
	offset = i_size & (PAGE_CACHE_SIZE-1);
	if (page->index >= end_index+1 || !offset) {
		/*
		 * The page may have dirty, unmapped buffers.  For example,
		 * they may have been added in ext3_writepage().  Make them
		 * freeable here, so the page does not leak.
		 */
2929
		do_invalidatepage(page, 0, PAGE_CACHE_SIZE);
L
Linus Torvalds 已提交
2930 2931 2932 2933 2934 2935
		unlock_page(page);
		return 0; /* don't care */
	}

	/*
	 * The page straddles i_size.  It must be zeroed out on each and every
2936
	 * writepage invocation because it may be mmapped.  "A file is mapped
L
Linus Torvalds 已提交
2937 2938 2939 2940
	 * in multiples of the page size.  For a file that is not a multiple of
	 * the  page size, the remaining memory is zeroed when mapped, and
	 * writes to that region are not written out to the file."
	 */
2941
	zero_user_segment(page, offset, PAGE_CACHE_SIZE);
2942 2943
	return __block_write_full_page(inode, page, get_block, wbc,
							end_buffer_async_write);
2944
}
2945
EXPORT_SYMBOL(block_write_full_page);
2946

L
Linus Torvalds 已提交
2947 2948 2949 2950 2951 2952 2953
sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
			    get_block_t *get_block)
{
	struct buffer_head tmp;
	struct inode *inode = mapping->host;
	tmp.b_state = 0;
	tmp.b_blocknr = 0;
2954
	tmp.b_size = 1 << inode->i_blkbits;
L
Linus Torvalds 已提交
2955 2956 2957
	get_block(inode, block, &tmp, 0);
	return tmp.b_blocknr;
}
2958
EXPORT_SYMBOL(generic_block_bmap);
L
Linus Torvalds 已提交
2959

2960
static void end_bio_bh_io_sync(struct bio *bio, int err)
L
Linus Torvalds 已提交
2961 2962 2963
{
	struct buffer_head *bh = bio->bi_private;

2964 2965 2966
	if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags)))
		set_bit(BH_Quiet, &bh->b_state);

L
Linus Torvalds 已提交
2967 2968 2969 2970
	bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
	bio_put(bio);
}

2971 2972
/*
 * This allows us to do IO even on the odd last sectors
2973
 * of a device, even if the block size is some multiple
2974 2975 2976 2977 2978 2979 2980 2981 2982
 * of the physical sector size.
 *
 * We'll just truncate the bio to the size of the device,
 * and clear the end of the buffer head manually.
 *
 * Truly out-of-range accesses will turn into actual IO
 * errors, this only handles the "we need to be able to
 * do IO at the final sector" case.
 */
2983
void guard_bio_eod(int rw, struct bio *bio)
2984 2985
{
	sector_t maxsector;
2986 2987
	struct bio_vec *bvec = &bio->bi_io_vec[bio->bi_vcnt - 1];
	unsigned truncated_bytes;
2988 2989 2990 2991 2992 2993 2994 2995 2996 2997

	maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9;
	if (!maxsector)
		return;

	/*
	 * If the *whole* IO is past the end of the device,
	 * let it through, and the IO layer will turn it into
	 * an EIO.
	 */
2998
	if (unlikely(bio->bi_iter.bi_sector >= maxsector))
2999 3000
		return;

3001
	maxsector -= bio->bi_iter.bi_sector;
3002
	if (likely((bio->bi_iter.bi_size >> 9) <= maxsector))
3003 3004
		return;

3005 3006
	/* Uhhuh. We've got a bio that straddles the device size! */
	truncated_bytes = bio->bi_iter.bi_size - (maxsector << 9);
3007 3008

	/* Truncate the bio.. */
3009 3010
	bio->bi_iter.bi_size -= truncated_bytes;
	bvec->bv_len -= truncated_bytes;
3011 3012

	/* ..and clear the end of the buffer for reads */
3013
	if ((rw & RW_MASK) == READ) {
3014 3015
		zero_user(bvec->bv_page, bvec->bv_offset + bvec->bv_len,
				truncated_bytes);
3016 3017 3018
	}
}

3019 3020
static int submit_bh_wbc(int rw, struct buffer_head *bh,
			 unsigned long bio_flags, struct writeback_control *wbc)
L
Linus Torvalds 已提交
3021 3022 3023 3024 3025 3026
{
	struct bio *bio;

	BUG_ON(!buffer_locked(bh));
	BUG_ON(!buffer_mapped(bh));
	BUG_ON(!bh->b_end_io);
3027 3028
	BUG_ON(buffer_delay(bh));
	BUG_ON(buffer_unwritten(bh));
L
Linus Torvalds 已提交
3029 3030

	/*
3031
	 * Only clear out a write error when rewriting
L
Linus Torvalds 已提交
3032
	 */
3033
	if (test_set_buffer_req(bh) && (rw & WRITE))
L
Linus Torvalds 已提交
3034 3035 3036 3037 3038 3039 3040 3041
		clear_buffer_write_io_error(bh);

	/*
	 * from here on down, it's all bio -- do the initial mapping,
	 * submit_bio -> generic_make_request may further map this bio around
	 */
	bio = bio_alloc(GFP_NOIO, 1);

3042
	if (wbc) {
3043
		wbc_init_bio(wbc, bio);
3044 3045
		wbc_account_io(wbc, bh->b_page, bh->b_size);
	}
3046

3047
	bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
L
Linus Torvalds 已提交
3048 3049 3050 3051 3052 3053
	bio->bi_bdev = bh->b_bdev;
	bio->bi_io_vec[0].bv_page = bh->b_page;
	bio->bi_io_vec[0].bv_len = bh->b_size;
	bio->bi_io_vec[0].bv_offset = bh_offset(bh);

	bio->bi_vcnt = 1;
3054
	bio->bi_iter.bi_size = bh->b_size;
L
Linus Torvalds 已提交
3055 3056 3057

	bio->bi_end_io = end_bio_bh_io_sync;
	bio->bi_private = bh;
3058
	bio->bi_flags |= bio_flags;
L
Linus Torvalds 已提交
3059

3060
	/* Take care of bh's that straddle the end of the device */
3061
	guard_bio_eod(rw, bio);
3062

3063 3064 3065 3066 3067
	if (buffer_meta(bh))
		rw |= REQ_META;
	if (buffer_prio(bh))
		rw |= REQ_PRIO;

L
Linus Torvalds 已提交
3068
	submit_bio(rw, bio);
3069
	return 0;
L
Linus Torvalds 已提交
3070
}
3071 3072 3073

int _submit_bh(int rw, struct buffer_head *bh, unsigned long bio_flags)
{
3074
	return submit_bh_wbc(rw, bh, bio_flags, NULL);
3075
}
3076 3077 3078 3079
EXPORT_SYMBOL_GPL(_submit_bh);

int submit_bh(int rw, struct buffer_head *bh)
{
3080
	return submit_bh_wbc(rw, bh, 0, NULL);
3081
}
3082
EXPORT_SYMBOL(submit_bh);
L
Linus Torvalds 已提交
3083 3084 3085

/**
 * ll_rw_block: low-level access to block devices (DEPRECATED)
C
Christoph Hellwig 已提交
3086
 * @rw: whether to %READ or %WRITE or maybe %READA (readahead)
L
Linus Torvalds 已提交
3087 3088 3089
 * @nr: number of &struct buffer_heads in the array
 * @bhs: array of pointers to &struct buffer_head
 *
3090 3091
 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
 * requests an I/O operation on them, either a %READ or a %WRITE.  The third
C
Christoph Hellwig 已提交
3092 3093
 * %READA option is described in the documentation for generic_make_request()
 * which ll_rw_block() calls.
L
Linus Torvalds 已提交
3094 3095
 *
 * This function drops any buffer that it cannot get a lock on (with the
C
Christoph Hellwig 已提交
3096 3097 3098 3099 3100
 * BH_Lock state bit), any buffer that appears to be clean when doing a write
 * request, and any buffer that appears to be up-to-date when doing read
 * request.  Further it marks as clean buffers that are processed for
 * writing (the buffer cache won't assume that they are actually clean
 * until the buffer gets unlocked).
L
Linus Torvalds 已提交
3101 3102
 *
 * ll_rw_block sets b_end_io to simple completion handler that marks
3103
 * the buffer up-to-date (if appropriate), unlocks the buffer and wakes
L
Linus Torvalds 已提交
3104 3105 3106 3107 3108 3109 3110 3111 3112 3113 3114 3115
 * any waiters. 
 *
 * All of the buffers must be for the same device, and must also be a
 * multiple of the current approved size for the device.
 */
void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
{
	int i;

	for (i = 0; i < nr; i++) {
		struct buffer_head *bh = bhs[i];

C
Christoph Hellwig 已提交
3116
		if (!trylock_buffer(bh))
L
Linus Torvalds 已提交
3117
			continue;
C
Christoph Hellwig 已提交
3118
		if (rw == WRITE) {
L
Linus Torvalds 已提交
3119
			if (test_clear_buffer_dirty(bh)) {
3120
				bh->b_end_io = end_buffer_write_sync;
3121
				get_bh(bh);
C
Christoph Hellwig 已提交
3122
				submit_bh(WRITE, bh);
L
Linus Torvalds 已提交
3123 3124 3125 3126
				continue;
			}
		} else {
			if (!buffer_uptodate(bh)) {
3127
				bh->b_end_io = end_buffer_read_sync;
3128
				get_bh(bh);
L
Linus Torvalds 已提交
3129 3130 3131 3132 3133 3134 3135
				submit_bh(rw, bh);
				continue;
			}
		}
		unlock_buffer(bh);
	}
}
3136
EXPORT_SYMBOL(ll_rw_block);
L
Linus Torvalds 已提交
3137

C
Christoph Hellwig 已提交
3138 3139 3140 3141 3142 3143 3144 3145 3146 3147 3148 3149 3150
void write_dirty_buffer(struct buffer_head *bh, int rw)
{
	lock_buffer(bh);
	if (!test_clear_buffer_dirty(bh)) {
		unlock_buffer(bh);
		return;
	}
	bh->b_end_io = end_buffer_write_sync;
	get_bh(bh);
	submit_bh(rw, bh);
}
EXPORT_SYMBOL(write_dirty_buffer);

L
Linus Torvalds 已提交
3151 3152 3153 3154 3155
/*
 * For a data-integrity writeout, we need to wait upon any in-progress I/O
 * and then start new I/O and then wait upon it.  The caller must have a ref on
 * the buffer_head.
 */
C
Christoph Hellwig 已提交
3156
int __sync_dirty_buffer(struct buffer_head *bh, int rw)
L
Linus Torvalds 已提交
3157 3158 3159 3160 3161 3162 3163 3164
{
	int ret = 0;

	WARN_ON(atomic_read(&bh->b_count) < 1);
	lock_buffer(bh);
	if (test_clear_buffer_dirty(bh)) {
		get_bh(bh);
		bh->b_end_io = end_buffer_write_sync;
C
Christoph Hellwig 已提交
3165
		ret = submit_bh(rw, bh);
L
Linus Torvalds 已提交
3166 3167 3168 3169 3170 3171 3172 3173
		wait_on_buffer(bh);
		if (!ret && !buffer_uptodate(bh))
			ret = -EIO;
	} else {
		unlock_buffer(bh);
	}
	return ret;
}
C
Christoph Hellwig 已提交
3174 3175 3176 3177 3178 3179
EXPORT_SYMBOL(__sync_dirty_buffer);

int sync_dirty_buffer(struct buffer_head *bh)
{
	return __sync_dirty_buffer(bh, WRITE_SYNC);
}
3180
EXPORT_SYMBOL(sync_dirty_buffer);
L
Linus Torvalds 已提交
3181 3182 3183 3184 3185 3186 3187 3188 3189 3190 3191 3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210 3211 3212 3213 3214 3215

/*
 * try_to_free_buffers() checks if all the buffers on this particular page
 * are unused, and releases them if so.
 *
 * Exclusion against try_to_free_buffers may be obtained by either
 * locking the page or by holding its mapping's private_lock.
 *
 * If the page is dirty but all the buffers are clean then we need to
 * be sure to mark the page clean as well.  This is because the page
 * may be against a block device, and a later reattachment of buffers
 * to a dirty page will set *all* buffers dirty.  Which would corrupt
 * filesystem data on the same device.
 *
 * The same applies to regular filesystem pages: if all the buffers are
 * clean then we set the page clean and proceed.  To do that, we require
 * total exclusion from __set_page_dirty_buffers().  That is obtained with
 * private_lock.
 *
 * try_to_free_buffers() is non-blocking.
 */
static inline int buffer_busy(struct buffer_head *bh)
{
	return atomic_read(&bh->b_count) |
		(bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
}

static int
drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
{
	struct buffer_head *head = page_buffers(page);
	struct buffer_head *bh;

	bh = head;
	do {
A
akpm@osdl.org 已提交
3216
		if (buffer_write_io_error(bh) && page->mapping)
L
Linus Torvalds 已提交
3217 3218 3219 3220 3221 3222 3223 3224 3225
			set_bit(AS_EIO, &page->mapping->flags);
		if (buffer_busy(bh))
			goto failed;
		bh = bh->b_this_page;
	} while (bh != head);

	do {
		struct buffer_head *next = bh->b_this_page;

3226
		if (bh->b_assoc_map)
L
Linus Torvalds 已提交
3227 3228 3229 3230 3231 3232 3233 3234 3235 3236 3237 3238 3239 3240 3241 3242 3243
			__remove_assoc_queue(bh);
		bh = next;
	} while (bh != head);
	*buffers_to_free = head;
	__clear_page_buffers(page);
	return 1;
failed:
	return 0;
}

int try_to_free_buffers(struct page *page)
{
	struct address_space * const mapping = page->mapping;
	struct buffer_head *buffers_to_free = NULL;
	int ret = 0;

	BUG_ON(!PageLocked(page));
3244
	if (PageWriteback(page))
L
Linus Torvalds 已提交
3245 3246 3247 3248 3249 3250 3251 3252 3253
		return 0;

	if (mapping == NULL) {		/* can this still happen? */
		ret = drop_buffers(page, &buffers_to_free);
		goto out;
	}

	spin_lock(&mapping->private_lock);
	ret = drop_buffers(page, &buffers_to_free);
3254 3255 3256 3257 3258 3259 3260 3261 3262 3263

	/*
	 * If the filesystem writes its buffers by hand (eg ext3)
	 * then we can have clean buffers against a dirty page.  We
	 * clean the page here; otherwise the VM will never notice
	 * that the filesystem did any IO at all.
	 *
	 * Also, during truncate, discard_buffer will have marked all
	 * the page's buffers clean.  We discover that here and clean
	 * the page also.
3264 3265 3266 3267
	 *
	 * private_lock must be held over this entire operation in order
	 * to synchronise against __set_page_dirty_buffers and prevent the
	 * dirty bit from being lost.
3268
	 */
3269 3270
	if (ret)
		cancel_dirty_page(page);
3271
	spin_unlock(&mapping->private_lock);
L
Linus Torvalds 已提交
3272 3273 3274 3275 3276 3277 3278 3279 3280 3281 3282 3283 3284 3285 3286 3287 3288 3289 3290
out:
	if (buffers_to_free) {
		struct buffer_head *bh = buffers_to_free;

		do {
			struct buffer_head *next = bh->b_this_page;
			free_buffer_head(bh);
			bh = next;
		} while (bh != buffers_to_free);
	}
	return ret;
}
EXPORT_SYMBOL(try_to_free_buffers);

/*
 * There are no bdflush tunables left.  But distributions are
 * still running obsolete flush daemons, so we terminate them here.
 *
 * Use of bdflush() is deprecated and will be removed in a future kernel.
3291
 * The `flush-X' kernel threads fully replace bdflush daemons and this call.
L
Linus Torvalds 已提交
3292
 */
3293
SYSCALL_DEFINE2(bdflush, int, func, long, data)
L
Linus Torvalds 已提交
3294 3295 3296 3297 3298 3299 3300 3301 3302 3303 3304 3305 3306 3307 3308 3309 3310 3311 3312 3313 3314 3315
{
	static int msg_count;

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

	if (msg_count < 5) {
		msg_count++;
		printk(KERN_INFO
			"warning: process `%s' used the obsolete bdflush"
			" system call\n", current->comm);
		printk(KERN_INFO "Fix your initscripts?\n");
	}

	if (func == 1)
		do_exit(0);
	return 0;
}

/*
 * Buffer-head allocation
 */
3316
static struct kmem_cache *bh_cachep __read_mostly;
L
Linus Torvalds 已提交
3317 3318 3319 3320 3321

/*
 * Once the number of bh's in the machine exceeds this level, we start
 * stripping them in writeback.
 */
3322
static unsigned long max_buffer_heads;
L
Linus Torvalds 已提交
3323 3324 3325 3326 3327 3328 3329 3330 3331 3332 3333 3334 3335 3336 3337

int buffer_heads_over_limit;

struct bh_accounting {
	int nr;			/* Number of live bh's */
	int ratelimit;		/* Limit cacheline bouncing */
};

static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};

static void recalc_bh_state(void)
{
	int i;
	int tot = 0;

3338
	if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
L
Linus Torvalds 已提交
3339
		return;
3340
	__this_cpu_write(bh_accounting.ratelimit, 0);
3341
	for_each_online_cpu(i)
L
Linus Torvalds 已提交
3342 3343 3344
		tot += per_cpu(bh_accounting, i).nr;
	buffer_heads_over_limit = (tot > max_buffer_heads);
}
3345

A
Al Viro 已提交
3346
struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
L
Linus Torvalds 已提交
3347
{
3348
	struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
L
Linus Torvalds 已提交
3349
	if (ret) {
C
Christoph Lameter 已提交
3350
		INIT_LIST_HEAD(&ret->b_assoc_buffers);
3351 3352
		preempt_disable();
		__this_cpu_inc(bh_accounting.nr);
L
Linus Torvalds 已提交
3353
		recalc_bh_state();
3354
		preempt_enable();
L
Linus Torvalds 已提交
3355 3356 3357 3358 3359 3360 3361 3362 3363
	}
	return ret;
}
EXPORT_SYMBOL(alloc_buffer_head);

void free_buffer_head(struct buffer_head *bh)
{
	BUG_ON(!list_empty(&bh->b_assoc_buffers));
	kmem_cache_free(bh_cachep, bh);
3364 3365
	preempt_disable();
	__this_cpu_dec(bh_accounting.nr);
L
Linus Torvalds 已提交
3366
	recalc_bh_state();
3367
	preempt_enable();
L
Linus Torvalds 已提交
3368 3369 3370 3371 3372 3373 3374 3375 3376 3377 3378 3379
}
EXPORT_SYMBOL(free_buffer_head);

static void buffer_exit_cpu(int cpu)
{
	int i;
	struct bh_lru *b = &per_cpu(bh_lrus, cpu);

	for (i = 0; i < BH_LRU_SIZE; i++) {
		brelse(b->bhs[i]);
		b->bhs[i] = NULL;
	}
3380
	this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
3381
	per_cpu(bh_accounting, cpu).nr = 0;
L
Linus Torvalds 已提交
3382 3383 3384 3385 3386
}

static int buffer_cpu_notify(struct notifier_block *self,
			      unsigned long action, void *hcpu)
{
3387
	if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
L
Linus Torvalds 已提交
3388 3389 3390 3391
		buffer_exit_cpu((unsigned long)hcpu);
	return NOTIFY_OK;
}

3392
/**
3393
 * bh_uptodate_or_lock - Test whether the buffer is uptodate
3394 3395 3396 3397 3398 3399 3400 3401 3402 3403 3404 3405 3406 3407 3408 3409 3410 3411
 * @bh: struct buffer_head
 *
 * Return true if the buffer is up-to-date and false,
 * with the buffer locked, if not.
 */
int bh_uptodate_or_lock(struct buffer_head *bh)
{
	if (!buffer_uptodate(bh)) {
		lock_buffer(bh);
		if (!buffer_uptodate(bh))
			return 0;
		unlock_buffer(bh);
	}
	return 1;
}
EXPORT_SYMBOL(bh_uptodate_or_lock);

/**
3412
 * bh_submit_read - Submit a locked buffer for reading
3413 3414 3415 3416 3417 3418 3419 3420 3421 3422 3423 3424 3425 3426 3427 3428 3429 3430 3431 3432 3433 3434 3435
 * @bh: struct buffer_head
 *
 * Returns zero on success and -EIO on error.
 */
int bh_submit_read(struct buffer_head *bh)
{
	BUG_ON(!buffer_locked(bh));

	if (buffer_uptodate(bh)) {
		unlock_buffer(bh);
		return 0;
	}

	get_bh(bh);
	bh->b_end_io = end_buffer_read_sync;
	submit_bh(READ, bh);
	wait_on_buffer(bh);
	if (buffer_uptodate(bh))
		return 0;
	return -EIO;
}
EXPORT_SYMBOL(bh_submit_read);

L
Linus Torvalds 已提交
3436 3437
void __init buffer_init(void)
{
3438
	unsigned long nrpages;
L
Linus Torvalds 已提交
3439

3440 3441 3442 3443
	bh_cachep = kmem_cache_create("buffer_head",
			sizeof(struct buffer_head), 0,
				(SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
				SLAB_MEM_SPREAD),
3444
				NULL);
L
Linus Torvalds 已提交
3445 3446 3447 3448 3449 3450 3451 3452

	/*
	 * Limit the bh occupancy to 10% of ZONE_NORMAL
	 */
	nrpages = (nr_free_buffer_pages() * 10) / 100;
	max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
	hotcpu_notifier(buffer_cpu_notify, 0);
}