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v6.13.7
   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 *  linux/fs/buffer.c
   4 *
   5 *  Copyright (C) 1991, 1992, 2002  Linus Torvalds
   6 */
   7
   8/*
   9 * Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95
  10 *
  11 * Removed a lot of unnecessary code and simplified things now that
  12 * the buffer cache isn't our primary cache - Andrew Tridgell 12/96
  13 *
  14 * Speed up hash, lru, and free list operations.  Use gfp() for allocating
  15 * hash table, use SLAB cache for buffer heads. SMP threading.  -DaveM
  16 *
  17 * Added 32k buffer block sizes - these are required older ARM systems. - RMK
  18 *
  19 * async buffer flushing, 1999 Andrea Arcangeli <andrea@suse.de>
  20 */
  21
  22#include <linux/kernel.h>
  23#include <linux/sched/signal.h>
  24#include <linux/syscalls.h>
  25#include <linux/fs.h>
  26#include <linux/iomap.h>
  27#include <linux/mm.h>
  28#include <linux/percpu.h>
  29#include <linux/slab.h>
  30#include <linux/capability.h>
  31#include <linux/blkdev.h>
  32#include <linux/file.h>
  33#include <linux/quotaops.h>
  34#include <linux/highmem.h>
  35#include <linux/export.h>
  36#include <linux/backing-dev.h>
  37#include <linux/writeback.h>
  38#include <linux/hash.h>
  39#include <linux/suspend.h>
  40#include <linux/buffer_head.h>
  41#include <linux/task_io_accounting_ops.h>
  42#include <linux/bio.h>
 
  43#include <linux/cpu.h>
  44#include <linux/bitops.h>
  45#include <linux/mpage.h>
  46#include <linux/bit_spinlock.h>
  47#include <linux/pagevec.h>
  48#include <linux/sched/mm.h>
  49#include <trace/events/block.h>
  50#include <linux/fscrypt.h>
  51#include <linux/fsverity.h>
  52#include <linux/sched/isolation.h>
  53
  54#include "internal.h"
  55
  56static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
  57static void submit_bh_wbc(blk_opf_t opf, struct buffer_head *bh,
  58			  enum rw_hint hint, struct writeback_control *wbc);
  59
  60#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
  61
  62inline void touch_buffer(struct buffer_head *bh)
  63{
  64	trace_block_touch_buffer(bh);
  65	folio_mark_accessed(bh->b_folio);
  66}
  67EXPORT_SYMBOL(touch_buffer);
  68
  69void __lock_buffer(struct buffer_head *bh)
  70{
  71	wait_on_bit_lock_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
  72}
  73EXPORT_SYMBOL(__lock_buffer);
  74
  75void unlock_buffer(struct buffer_head *bh)
  76{
  77	clear_bit_unlock(BH_Lock, &bh->b_state);
  78	smp_mb__after_atomic();
  79	wake_up_bit(&bh->b_state, BH_Lock);
  80}
  81EXPORT_SYMBOL(unlock_buffer);
  82
  83/*
  84 * Returns if the folio has dirty or writeback buffers. If all the buffers
  85 * are unlocked and clean then the folio_test_dirty information is stale. If
  86 * any of the buffers are locked, it is assumed they are locked for IO.
  87 */
  88void buffer_check_dirty_writeback(struct folio *folio,
  89				     bool *dirty, bool *writeback)
  90{
  91	struct buffer_head *head, *bh;
  92	*dirty = false;
  93	*writeback = false;
  94
  95	BUG_ON(!folio_test_locked(folio));
  96
  97	head = folio_buffers(folio);
  98	if (!head)
  99		return;
 100
 101	if (folio_test_writeback(folio))
 102		*writeback = true;
 103
 
 104	bh = head;
 105	do {
 106		if (buffer_locked(bh))
 107			*writeback = true;
 108
 109		if (buffer_dirty(bh))
 110			*dirty = true;
 111
 112		bh = bh->b_this_page;
 113	} while (bh != head);
 114}
 
 115
 116/*
 117 * Block until a buffer comes unlocked.  This doesn't stop it
 118 * from becoming locked again - you have to lock it yourself
 119 * if you want to preserve its state.
 120 */
 121void __wait_on_buffer(struct buffer_head * bh)
 122{
 123	wait_on_bit_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
 124}
 125EXPORT_SYMBOL(__wait_on_buffer);
 126
 
 
 
 
 
 
 
 
 127static void buffer_io_error(struct buffer_head *bh, char *msg)
 128{
 129	if (!test_bit(BH_Quiet, &bh->b_state))
 130		printk_ratelimited(KERN_ERR
 131			"Buffer I/O error on dev %pg, logical block %llu%s\n",
 132			bh->b_bdev, (unsigned long long)bh->b_blocknr, msg);
 133}
 134
 135/*
 136 * End-of-IO handler helper function which does not touch the bh after
 137 * unlocking it.
 138 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
 139 * a race there is benign: unlock_buffer() only use the bh's address for
 140 * hashing after unlocking the buffer, so it doesn't actually touch the bh
 141 * itself.
 142 */
 143static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
 144{
 145	if (uptodate) {
 146		set_buffer_uptodate(bh);
 147	} else {
 148		/* This happens, due to failed read-ahead attempts. */
 149		clear_buffer_uptodate(bh);
 150	}
 151	unlock_buffer(bh);
 152}
 153
 154/*
 155 * Default synchronous end-of-IO handler..  Just mark it up-to-date and
 156 * unlock the buffer.
 157 */
 158void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
 159{
 160	__end_buffer_read_notouch(bh, uptodate);
 161	put_bh(bh);
 162}
 163EXPORT_SYMBOL(end_buffer_read_sync);
 164
 165void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
 166{
 167	if (uptodate) {
 168		set_buffer_uptodate(bh);
 169	} else {
 170		buffer_io_error(bh, ", lost sync page write");
 171		mark_buffer_write_io_error(bh);
 172		clear_buffer_uptodate(bh);
 173	}
 174	unlock_buffer(bh);
 175	put_bh(bh);
 176}
 177EXPORT_SYMBOL(end_buffer_write_sync);
 178
 179/*
 180 * Various filesystems appear to want __find_get_block to be non-blocking.
 181 * But it's the page lock which protects the buffers.  To get around this,
 182 * we get exclusion from try_to_free_buffers with the blockdev mapping's
 183 * i_private_lock.
 184 *
 185 * Hack idea: for the blockdev mapping, i_private_lock contention
 186 * may be quite high.  This code could TryLock the page, and if that
 187 * succeeds, there is no need to take i_private_lock.
 188 */
 189static struct buffer_head *
 190__find_get_block_slow(struct block_device *bdev, sector_t block)
 191{
 192	struct address_space *bd_mapping = bdev->bd_mapping;
 193	const int blkbits = bd_mapping->host->i_blkbits;
 194	struct buffer_head *ret = NULL;
 195	pgoff_t index;
 196	struct buffer_head *bh;
 197	struct buffer_head *head;
 198	struct folio *folio;
 199	int all_mapped = 1;
 200	static DEFINE_RATELIMIT_STATE(last_warned, HZ, 1);
 201
 202	index = ((loff_t)block << blkbits) / PAGE_SIZE;
 203	folio = __filemap_get_folio(bd_mapping, index, FGP_ACCESSED, 0);
 204	if (IS_ERR(folio))
 205		goto out;
 206
 207	spin_lock(&bd_mapping->i_private_lock);
 208	head = folio_buffers(folio);
 209	if (!head)
 210		goto out_unlock;
 
 211	bh = head;
 212	do {
 213		if (!buffer_mapped(bh))
 214			all_mapped = 0;
 215		else if (bh->b_blocknr == block) {
 216			ret = bh;
 217			get_bh(bh);
 218			goto out_unlock;
 219		}
 220		bh = bh->b_this_page;
 221	} while (bh != head);
 222
 223	/* we might be here because some of the buffers on this page are
 224	 * not mapped.  This is due to various races between
 225	 * file io on the block device and getblk.  It gets dealt with
 226	 * elsewhere, don't buffer_error if we had some unmapped buffers
 227	 */
 228	ratelimit_set_flags(&last_warned, RATELIMIT_MSG_ON_RELEASE);
 229	if (all_mapped && __ratelimit(&last_warned)) {
 230		printk("__find_get_block_slow() failed. block=%llu, "
 231		       "b_blocknr=%llu, b_state=0x%08lx, b_size=%zu, "
 232		       "device %pg blocksize: %d\n",
 233		       (unsigned long long)block,
 234		       (unsigned long long)bh->b_blocknr,
 235		       bh->b_state, bh->b_size, bdev,
 236		       1 << blkbits);
 237	}
 238out_unlock:
 239	spin_unlock(&bd_mapping->i_private_lock);
 240	folio_put(folio);
 241out:
 242	return ret;
 243}
 244
 
 
 
 
 245static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
 246{
 247	unsigned long flags;
 248	struct buffer_head *first;
 249	struct buffer_head *tmp;
 250	struct folio *folio;
 251	int folio_uptodate = 1;
 252
 253	BUG_ON(!buffer_async_read(bh));
 254
 255	folio = bh->b_folio;
 256	if (uptodate) {
 257		set_buffer_uptodate(bh);
 258	} else {
 259		clear_buffer_uptodate(bh);
 260		buffer_io_error(bh, ", async page read");
 
 261	}
 262
 263	/*
 264	 * Be _very_ careful from here on. Bad things can happen if
 265	 * two buffer heads end IO at almost the same time and both
 266	 * decide that the page is now completely done.
 267	 */
 268	first = folio_buffers(folio);
 269	spin_lock_irqsave(&first->b_uptodate_lock, flags);
 
 270	clear_buffer_async_read(bh);
 271	unlock_buffer(bh);
 272	tmp = bh;
 273	do {
 274		if (!buffer_uptodate(tmp))
 275			folio_uptodate = 0;
 276		if (buffer_async_read(tmp)) {
 277			BUG_ON(!buffer_locked(tmp));
 278			goto still_busy;
 279		}
 280		tmp = tmp->b_this_page;
 281	} while (tmp != bh);
 282	spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
 
 283
 284	folio_end_read(folio, folio_uptodate);
 
 
 
 
 
 
 285	return;
 286
 287still_busy:
 288	spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
 
 289	return;
 290}
 291
 292struct postprocess_bh_ctx {
 293	struct work_struct work;
 294	struct buffer_head *bh;
 295};
 296
 297static void verify_bh(struct work_struct *work)
 298{
 299	struct postprocess_bh_ctx *ctx =
 300		container_of(work, struct postprocess_bh_ctx, work);
 301	struct buffer_head *bh = ctx->bh;
 302	bool valid;
 303
 304	valid = fsverity_verify_blocks(bh->b_folio, bh->b_size, bh_offset(bh));
 305	end_buffer_async_read(bh, valid);
 306	kfree(ctx);
 307}
 308
 309static bool need_fsverity(struct buffer_head *bh)
 310{
 311	struct folio *folio = bh->b_folio;
 312	struct inode *inode = folio->mapping->host;
 313
 314	return fsverity_active(inode) &&
 315		/* needed by ext4 */
 316		folio->index < DIV_ROUND_UP(inode->i_size, PAGE_SIZE);
 317}
 318
 319static void decrypt_bh(struct work_struct *work)
 320{
 321	struct postprocess_bh_ctx *ctx =
 322		container_of(work, struct postprocess_bh_ctx, work);
 323	struct buffer_head *bh = ctx->bh;
 324	int err;
 325
 326	err = fscrypt_decrypt_pagecache_blocks(bh->b_folio, bh->b_size,
 327					       bh_offset(bh));
 328	if (err == 0 && need_fsverity(bh)) {
 329		/*
 330		 * We use different work queues for decryption and for verity
 331		 * because verity may require reading metadata pages that need
 332		 * decryption, and we shouldn't recurse to the same workqueue.
 333		 */
 334		INIT_WORK(&ctx->work, verify_bh);
 335		fsverity_enqueue_verify_work(&ctx->work);
 336		return;
 337	}
 338	end_buffer_async_read(bh, err == 0);
 339	kfree(ctx);
 340}
 341
 342/*
 343 * I/O completion handler for block_read_full_folio() - pages
 344 * which come unlocked at the end of I/O.
 345 */
 346static void end_buffer_async_read_io(struct buffer_head *bh, int uptodate)
 347{
 348	struct inode *inode = bh->b_folio->mapping->host;
 349	bool decrypt = fscrypt_inode_uses_fs_layer_crypto(inode);
 350	bool verify = need_fsverity(bh);
 351
 352	/* Decrypt (with fscrypt) and/or verify (with fsverity) if needed. */
 353	if (uptodate && (decrypt || verify)) {
 354		struct postprocess_bh_ctx *ctx =
 355			kmalloc(sizeof(*ctx), GFP_ATOMIC);
 356
 357		if (ctx) {
 358			ctx->bh = bh;
 359			if (decrypt) {
 360				INIT_WORK(&ctx->work, decrypt_bh);
 361				fscrypt_enqueue_decrypt_work(&ctx->work);
 362			} else {
 363				INIT_WORK(&ctx->work, verify_bh);
 364				fsverity_enqueue_verify_work(&ctx->work);
 365			}
 366			return;
 367		}
 368		uptodate = 0;
 369	}
 370	end_buffer_async_read(bh, uptodate);
 371}
 372
 373/*
 374 * Completion handler for block_write_full_folio() - folios which are unlocked
 375 * during I/O, and which have the writeback flag cleared upon I/O completion.
 376 */
 377static void end_buffer_async_write(struct buffer_head *bh, int uptodate)
 378{
 379	unsigned long flags;
 380	struct buffer_head *first;
 381	struct buffer_head *tmp;
 382	struct folio *folio;
 383
 384	BUG_ON(!buffer_async_write(bh));
 385
 386	folio = bh->b_folio;
 387	if (uptodate) {
 388		set_buffer_uptodate(bh);
 389	} else {
 390		buffer_io_error(bh, ", lost async page write");
 391		mark_buffer_write_io_error(bh);
 392		clear_buffer_uptodate(bh);
 
 393	}
 394
 395	first = folio_buffers(folio);
 396	spin_lock_irqsave(&first->b_uptodate_lock, flags);
 
 397
 398	clear_buffer_async_write(bh);
 399	unlock_buffer(bh);
 400	tmp = bh->b_this_page;
 401	while (tmp != bh) {
 402		if (buffer_async_write(tmp)) {
 403			BUG_ON(!buffer_locked(tmp));
 404			goto still_busy;
 405		}
 406		tmp = tmp->b_this_page;
 407	}
 408	spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
 409	folio_end_writeback(folio);
 
 410	return;
 411
 412still_busy:
 413	spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
 
 414	return;
 415}
 
 416
 417/*
 418 * If a page's buffers are under async readin (end_buffer_async_read
 419 * completion) then there is a possibility that another thread of
 420 * control could lock one of the buffers after it has completed
 421 * but while some of the other buffers have not completed.  This
 422 * locked buffer would confuse end_buffer_async_read() into not unlocking
 423 * the page.  So the absence of BH_Async_Read tells end_buffer_async_read()
 424 * that this buffer is not under async I/O.
 425 *
 426 * The page comes unlocked when it has no locked buffer_async buffers
 427 * left.
 428 *
 429 * PageLocked prevents anyone starting new async I/O reads any of
 430 * the buffers.
 431 *
 432 * PageWriteback is used to prevent simultaneous writeout of the same
 433 * page.
 434 *
 435 * PageLocked prevents anyone from starting writeback of a page which is
 436 * under read I/O (PageWriteback is only ever set against a locked page).
 437 */
 438static void mark_buffer_async_read(struct buffer_head *bh)
 439{
 440	bh->b_end_io = end_buffer_async_read_io;
 441	set_buffer_async_read(bh);
 442}
 443
 444static void mark_buffer_async_write_endio(struct buffer_head *bh,
 445					  bh_end_io_t *handler)
 446{
 447	bh->b_end_io = handler;
 448	set_buffer_async_write(bh);
 449}
 450
 451void mark_buffer_async_write(struct buffer_head *bh)
 452{
 453	mark_buffer_async_write_endio(bh, end_buffer_async_write);
 454}
 455EXPORT_SYMBOL(mark_buffer_async_write);
 456
 457
 458/*
 459 * fs/buffer.c contains helper functions for buffer-backed address space's
 460 * fsync functions.  A common requirement for buffer-based filesystems is
 461 * that certain data from the backing blockdev needs to be written out for
 462 * a successful fsync().  For example, ext2 indirect blocks need to be
 463 * written back and waited upon before fsync() returns.
 464 *
 465 * The functions mark_buffer_dirty_inode(), fsync_inode_buffers(),
 466 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
 467 * management of a list of dependent buffers at ->i_mapping->i_private_list.
 468 *
 469 * Locking is a little subtle: try_to_free_buffers() will remove buffers
 470 * from their controlling inode's queue when they are being freed.  But
 471 * try_to_free_buffers() will be operating against the *blockdev* mapping
 472 * at the time, not against the S_ISREG file which depends on those buffers.
 473 * So the locking for i_private_list is via the i_private_lock in the address_space
 474 * which backs the buffers.  Which is different from the address_space 
 475 * against which the buffers are listed.  So for a particular address_space,
 476 * mapping->i_private_lock does *not* protect mapping->i_private_list!  In fact,
 477 * mapping->i_private_list will always be protected by the backing blockdev's
 478 * ->i_private_lock.
 479 *
 480 * Which introduces a requirement: all buffers on an address_space's
 481 * ->i_private_list must be from the same address_space: the blockdev's.
 482 *
 483 * address_spaces which do not place buffers at ->i_private_list via these
 484 * utility functions are free to use i_private_lock and i_private_list for
 485 * whatever they want.  The only requirement is that list_empty(i_private_list)
 486 * be true at clear_inode() time.
 487 *
 488 * FIXME: clear_inode should not call invalidate_inode_buffers().  The
 489 * filesystems should do that.  invalidate_inode_buffers() should just go
 490 * BUG_ON(!list_empty).
 491 *
 492 * FIXME: mark_buffer_dirty_inode() is a data-plane operation.  It should
 493 * take an address_space, not an inode.  And it should be called
 494 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
 495 * queued up.
 496 *
 497 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
 498 * list if it is already on a list.  Because if the buffer is on a list,
 499 * it *must* already be on the right one.  If not, the filesystem is being
 500 * silly.  This will save a ton of locking.  But first we have to ensure
 501 * that buffers are taken *off* the old inode's list when they are freed
 502 * (presumably in truncate).  That requires careful auditing of all
 503 * filesystems (do it inside bforget()).  It could also be done by bringing
 504 * b_inode back.
 505 */
 506
 507/*
 508 * The buffer's backing address_space's i_private_lock must be held
 509 */
 510static void __remove_assoc_queue(struct buffer_head *bh)
 511{
 512	list_del_init(&bh->b_assoc_buffers);
 513	WARN_ON(!bh->b_assoc_map);
 514	bh->b_assoc_map = NULL;
 515}
 516
 517int inode_has_buffers(struct inode *inode)
 518{
 519	return !list_empty(&inode->i_data.i_private_list);
 520}
 521
 522/*
 523 * osync is designed to support O_SYNC io.  It waits synchronously for
 524 * all already-submitted IO to complete, but does not queue any new
 525 * writes to the disk.
 526 *
 527 * To do O_SYNC writes, just queue the buffer writes with write_dirty_buffer
 528 * as you dirty the buffers, and then use osync_inode_buffers to wait for
 529 * completion.  Any other dirty buffers which are not yet queued for
 530 * write will not be flushed to disk by the osync.
 531 */
 532static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
 533{
 534	struct buffer_head *bh;
 535	struct list_head *p;
 536	int err = 0;
 537
 538	spin_lock(lock);
 539repeat:
 540	list_for_each_prev(p, list) {
 541		bh = BH_ENTRY(p);
 542		if (buffer_locked(bh)) {
 543			get_bh(bh);
 544			spin_unlock(lock);
 545			wait_on_buffer(bh);
 546			if (!buffer_uptodate(bh))
 547				err = -EIO;
 548			brelse(bh);
 549			spin_lock(lock);
 550			goto repeat;
 551		}
 552	}
 553	spin_unlock(lock);
 554	return err;
 555}
 556
 
 
 
 
 
 
 557/**
 558 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
 559 * @mapping: the mapping which wants those buffers written
 560 *
 561 * Starts I/O against the buffers at mapping->i_private_list, and waits upon
 562 * that I/O.
 563 *
 564 * Basically, this is a convenience function for fsync().
 565 * @mapping is a file or directory which needs those buffers to be written for
 566 * a successful fsync().
 567 */
 568int sync_mapping_buffers(struct address_space *mapping)
 569{
 570	struct address_space *buffer_mapping = mapping->i_private_data;
 571
 572	if (buffer_mapping == NULL || list_empty(&mapping->i_private_list))
 573		return 0;
 574
 575	return fsync_buffers_list(&buffer_mapping->i_private_lock,
 576					&mapping->i_private_list);
 577}
 578EXPORT_SYMBOL(sync_mapping_buffers);
 579
 580/**
 581 * generic_buffers_fsync_noflush - generic buffer fsync implementation
 582 * for simple filesystems with no inode lock
 583 *
 584 * @file:	file to synchronize
 585 * @start:	start offset in bytes
 586 * @end:	end offset in bytes (inclusive)
 587 * @datasync:	only synchronize essential metadata if true
 588 *
 589 * This is a generic implementation of the fsync method for simple
 590 * filesystems which track all non-inode metadata in the buffers list
 591 * hanging off the address_space structure.
 592 */
 593int generic_buffers_fsync_noflush(struct file *file, loff_t start, loff_t end,
 594				  bool datasync)
 595{
 596	struct inode *inode = file->f_mapping->host;
 597	int err;
 598	int ret;
 599
 600	err = file_write_and_wait_range(file, start, end);
 601	if (err)
 602		return err;
 603
 604	ret = sync_mapping_buffers(inode->i_mapping);
 605	if (!(inode->i_state & I_DIRTY_ALL))
 606		goto out;
 607	if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
 608		goto out;
 609
 610	err = sync_inode_metadata(inode, 1);
 611	if (ret == 0)
 612		ret = err;
 613
 614out:
 615	/* check and advance again to catch errors after syncing out buffers */
 616	err = file_check_and_advance_wb_err(file);
 617	if (ret == 0)
 618		ret = err;
 619	return ret;
 620}
 621EXPORT_SYMBOL(generic_buffers_fsync_noflush);
 622
 623/**
 624 * generic_buffers_fsync - generic buffer fsync implementation
 625 * for simple filesystems with no inode lock
 626 *
 627 * @file:	file to synchronize
 628 * @start:	start offset in bytes
 629 * @end:	end offset in bytes (inclusive)
 630 * @datasync:	only synchronize essential metadata if true
 631 *
 632 * This is a generic implementation of the fsync method for simple
 633 * filesystems which track all non-inode metadata in the buffers list
 634 * hanging off the address_space structure. This also makes sure that
 635 * a device cache flush operation is called at the end.
 636 */
 637int generic_buffers_fsync(struct file *file, loff_t start, loff_t end,
 638			  bool datasync)
 639{
 640	struct inode *inode = file->f_mapping->host;
 641	int ret;
 642
 643	ret = generic_buffers_fsync_noflush(file, start, end, datasync);
 644	if (!ret)
 645		ret = blkdev_issue_flush(inode->i_sb->s_bdev);
 646	return ret;
 647}
 648EXPORT_SYMBOL(generic_buffers_fsync);
 649
 650/*
 651 * Called when we've recently written block `bblock', and it is known that
 652 * `bblock' was for a buffer_boundary() buffer.  This means that the block at
 653 * `bblock + 1' is probably a dirty indirect block.  Hunt it down and, if it's
 654 * dirty, schedule it for IO.  So that indirects merge nicely with their data.
 655 */
 656void write_boundary_block(struct block_device *bdev,
 657			sector_t bblock, unsigned blocksize)
 658{
 659	struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
 660	if (bh) {
 661		if (buffer_dirty(bh))
 662			write_dirty_buffer(bh, 0);
 663		put_bh(bh);
 664	}
 665}
 666
 667void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
 668{
 669	struct address_space *mapping = inode->i_mapping;
 670	struct address_space *buffer_mapping = bh->b_folio->mapping;
 671
 672	mark_buffer_dirty(bh);
 673	if (!mapping->i_private_data) {
 674		mapping->i_private_data = buffer_mapping;
 675	} else {
 676		BUG_ON(mapping->i_private_data != buffer_mapping);
 677	}
 678	if (!bh->b_assoc_map) {
 679		spin_lock(&buffer_mapping->i_private_lock);
 680		list_move_tail(&bh->b_assoc_buffers,
 681				&mapping->i_private_list);
 682		bh->b_assoc_map = mapping;
 683		spin_unlock(&buffer_mapping->i_private_lock);
 684	}
 685}
 686EXPORT_SYMBOL(mark_buffer_dirty_inode);
 687
 688/**
 689 * block_dirty_folio - Mark a folio as dirty.
 690 * @mapping: The address space containing this folio.
 691 * @folio: The folio to mark dirty.
 692 *
 693 * Filesystems which use buffer_heads can use this function as their
 694 * ->dirty_folio implementation.  Some filesystems need to do a little
 695 * work before calling this function.  Filesystems which do not use
 696 * buffer_heads should call filemap_dirty_folio() instead.
 697 *
 698 * If the folio has buffers, the uptodate buffers are set dirty, to
 699 * preserve dirty-state coherency between the folio and the buffers.
 700 * Buffers added to a dirty folio are created dirty.
 701 *
 702 * The buffers are dirtied before the folio is dirtied.  There's a small
 703 * race window in which writeback may see the folio cleanness but not the
 704 * buffer dirtiness.  That's fine.  If this code were to set the folio
 705 * dirty before the buffers, writeback could clear the folio dirty flag,
 706 * see a bunch of clean buffers and we'd end up with dirty buffers/clean
 707 * folio on the dirty folio list.
 708 *
 709 * We use i_private_lock to lock against try_to_free_buffers() while
 710 * using the folio's buffer list.  This also prevents clean buffers
 711 * being added to the folio after it was set dirty.
 712 *
 713 * Context: May only be called from process context.  Does not sleep.
 714 * Caller must ensure that @folio cannot be truncated during this call,
 715 * typically by holding the folio lock or having a page in the folio
 716 * mapped and holding the page table lock.
 717 *
 718 * Return: True if the folio was dirtied; false if it was already dirtied.
 719 */
 720bool block_dirty_folio(struct address_space *mapping, struct folio *folio)
 
 721{
 722	struct buffer_head *head;
 723	bool newly_dirty;
 724
 725	spin_lock(&mapping->i_private_lock);
 726	head = folio_buffers(folio);
 727	if (head) {
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 728		struct buffer_head *bh = head;
 729
 730		do {
 731			set_buffer_dirty(bh);
 732			bh = bh->b_this_page;
 733		} while (bh != head);
 734	}
 735	/*
 736	 * Lock out page's memcg migration to keep PageDirty
 737	 * synchronized with per-memcg dirty page counters.
 738	 */
 739	newly_dirty = !folio_test_set_dirty(folio);
 740	spin_unlock(&mapping->i_private_lock);
 
 741
 742	if (newly_dirty)
 743		__folio_mark_dirty(folio, mapping, 1);
 
 
 744
 745	if (newly_dirty)
 746		__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
 747
 748	return newly_dirty;
 749}
 750EXPORT_SYMBOL(block_dirty_folio);
 751
 752/*
 753 * Write out and wait upon a list of buffers.
 754 *
 755 * We have conflicting pressures: we want to make sure that all
 756 * initially dirty buffers get waited on, but that any subsequently
 757 * dirtied buffers don't.  After all, we don't want fsync to last
 758 * forever if somebody is actively writing to the file.
 759 *
 760 * Do this in two main stages: first we copy dirty buffers to a
 761 * temporary inode list, queueing the writes as we go.  Then we clean
 762 * up, waiting for those writes to complete.
 763 * 
 764 * During this second stage, any subsequent updates to the file may end
 765 * up refiling the buffer on the original inode's dirty list again, so
 766 * there is a chance we will end up with a buffer queued for write but
 767 * not yet completed on that list.  So, as a final cleanup we go through
 768 * the osync code to catch these locked, dirty buffers without requeuing
 769 * any newly dirty buffers for write.
 770 */
 771static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
 772{
 773	struct buffer_head *bh;
 
 774	struct address_space *mapping;
 775	int err = 0, err2;
 776	struct blk_plug plug;
 777	LIST_HEAD(tmp);
 778
 
 779	blk_start_plug(&plug);
 780
 781	spin_lock(lock);
 782	while (!list_empty(list)) {
 783		bh = BH_ENTRY(list->next);
 784		mapping = bh->b_assoc_map;
 785		__remove_assoc_queue(bh);
 786		/* Avoid race with mark_buffer_dirty_inode() which does
 787		 * a lockless check and we rely on seeing the dirty bit */
 788		smp_mb();
 789		if (buffer_dirty(bh) || buffer_locked(bh)) {
 790			list_add(&bh->b_assoc_buffers, &tmp);
 791			bh->b_assoc_map = mapping;
 792			if (buffer_dirty(bh)) {
 793				get_bh(bh);
 794				spin_unlock(lock);
 795				/*
 796				 * Ensure any pending I/O completes so that
 797				 * write_dirty_buffer() actually writes the
 798				 * current contents - it is a noop if I/O is
 799				 * still in flight on potentially older
 800				 * contents.
 801				 */
 802				write_dirty_buffer(bh, REQ_SYNC);
 803
 804				/*
 805				 * Kick off IO for the previous mapping. Note
 806				 * that we will not run the very last mapping,
 807				 * wait_on_buffer() will do that for us
 808				 * through sync_buffer().
 809				 */
 810				brelse(bh);
 811				spin_lock(lock);
 812			}
 813		}
 814	}
 815
 816	spin_unlock(lock);
 817	blk_finish_plug(&plug);
 818	spin_lock(lock);
 819
 820	while (!list_empty(&tmp)) {
 821		bh = BH_ENTRY(tmp.prev);
 822		get_bh(bh);
 823		mapping = bh->b_assoc_map;
 824		__remove_assoc_queue(bh);
 825		/* Avoid race with mark_buffer_dirty_inode() which does
 826		 * a lockless check and we rely on seeing the dirty bit */
 827		smp_mb();
 828		if (buffer_dirty(bh)) {
 829			list_add(&bh->b_assoc_buffers,
 830				 &mapping->i_private_list);
 831			bh->b_assoc_map = mapping;
 832		}
 833		spin_unlock(lock);
 834		wait_on_buffer(bh);
 835		if (!buffer_uptodate(bh))
 836			err = -EIO;
 837		brelse(bh);
 838		spin_lock(lock);
 839	}
 840	
 841	spin_unlock(lock);
 842	err2 = osync_buffers_list(lock, list);
 843	if (err)
 844		return err;
 845	else
 846		return err2;
 847}
 848
 849/*
 850 * Invalidate any and all dirty buffers on a given inode.  We are
 851 * probably unmounting the fs, but that doesn't mean we have already
 852 * done a sync().  Just drop the buffers from the inode list.
 853 *
 854 * NOTE: we take the inode's blockdev's mapping's i_private_lock.  Which
 855 * assumes that all the buffers are against the blockdev.
 
 856 */
 857void invalidate_inode_buffers(struct inode *inode)
 858{
 859	if (inode_has_buffers(inode)) {
 860		struct address_space *mapping = &inode->i_data;
 861		struct list_head *list = &mapping->i_private_list;
 862		struct address_space *buffer_mapping = mapping->i_private_data;
 863
 864		spin_lock(&buffer_mapping->i_private_lock);
 865		while (!list_empty(list))
 866			__remove_assoc_queue(BH_ENTRY(list->next));
 867		spin_unlock(&buffer_mapping->i_private_lock);
 868	}
 869}
 870EXPORT_SYMBOL(invalidate_inode_buffers);
 871
 872/*
 873 * Remove any clean buffers from the inode's buffer list.  This is called
 874 * when we're trying to free the inode itself.  Those buffers can pin it.
 875 *
 876 * Returns true if all buffers were removed.
 877 */
 878int remove_inode_buffers(struct inode *inode)
 879{
 880	int ret = 1;
 881
 882	if (inode_has_buffers(inode)) {
 883		struct address_space *mapping = &inode->i_data;
 884		struct list_head *list = &mapping->i_private_list;
 885		struct address_space *buffer_mapping = mapping->i_private_data;
 886
 887		spin_lock(&buffer_mapping->i_private_lock);
 888		while (!list_empty(list)) {
 889			struct buffer_head *bh = BH_ENTRY(list->next);
 890			if (buffer_dirty(bh)) {
 891				ret = 0;
 892				break;
 893			}
 894			__remove_assoc_queue(bh);
 895		}
 896		spin_unlock(&buffer_mapping->i_private_lock);
 897	}
 898	return ret;
 899}
 900
 901/*
 902 * Create the appropriate buffers when given a folio for data area and
 903 * the size of each buffer.. Use the bh->b_this_page linked list to
 904 * follow the buffers created.  Return NULL if unable to create more
 905 * buffers.
 906 *
 907 * The retry flag is used to differentiate async IO (paging, swapping)
 908 * which may not fail from ordinary buffer allocations.
 909 */
 910struct buffer_head *folio_alloc_buffers(struct folio *folio, unsigned long size,
 911					gfp_t gfp)
 912{
 913	struct buffer_head *bh, *head;
 
 914	long offset;
 915	struct mem_cgroup *memcg, *old_memcg;
 916
 917	/* The folio lock pins the memcg */
 918	memcg = folio_memcg(folio);
 919	old_memcg = set_active_memcg(memcg);
 920
 921	head = NULL;
 922	offset = folio_size(folio);
 923	while ((offset -= size) >= 0) {
 924		bh = alloc_buffer_head(gfp);
 925		if (!bh)
 926			goto no_grow;
 927
 928		bh->b_this_page = head;
 929		bh->b_blocknr = -1;
 930		head = bh;
 931
 932		bh->b_size = size;
 933
 934		/* Link the buffer to its folio */
 935		folio_set_bh(bh, folio, offset);
 936	}
 937out:
 938	set_active_memcg(old_memcg);
 939	return head;
 940/*
 941 * In case anything failed, we just free everything we got.
 942 */
 943no_grow:
 944	if (head) {
 945		do {
 946			bh = head;
 947			head = head->b_this_page;
 948			free_buffer_head(bh);
 949		} while (head);
 950	}
 951
 952	goto out;
 953}
 954EXPORT_SYMBOL_GPL(folio_alloc_buffers);
 955
 956struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size)
 957{
 958	gfp_t gfp = GFP_NOFS | __GFP_ACCOUNT;
 959
 960	return folio_alloc_buffers(page_folio(page), size, gfp);
 961}
 962EXPORT_SYMBOL_GPL(alloc_page_buffers);
 963
 964static inline void link_dev_buffers(struct folio *folio,
 965		struct buffer_head *head)
 966{
 967	struct buffer_head *bh, *tail;
 968
 969	bh = head;
 970	do {
 971		tail = bh;
 972		bh = bh->b_this_page;
 973	} while (bh);
 974	tail->b_this_page = head;
 975	folio_attach_private(folio, head);
 976}
 977
 978static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
 979{
 980	sector_t retval = ~((sector_t)0);
 981	loff_t sz = bdev_nr_bytes(bdev);
 982
 983	if (sz) {
 984		unsigned int sizebits = blksize_bits(size);
 985		retval = (sz >> sizebits);
 986	}
 987	return retval;
 988}
 989
 990/*
 991 * Initialise the state of a blockdev folio's buffers.
 992 */ 
 993static sector_t folio_init_buffers(struct folio *folio,
 994		struct block_device *bdev, unsigned size)
 
 995{
 996	struct buffer_head *head = folio_buffers(folio);
 997	struct buffer_head *bh = head;
 998	bool uptodate = folio_test_uptodate(folio);
 999	sector_t block = div_u64(folio_pos(folio), size);
1000	sector_t end_block = blkdev_max_block(bdev, size);
1001
1002	do {
1003		if (!buffer_mapped(bh)) {
1004			bh->b_end_io = NULL;
1005			bh->b_private = NULL;
1006			bh->b_bdev = bdev;
1007			bh->b_blocknr = block;
1008			if (uptodate)
1009				set_buffer_uptodate(bh);
1010			if (block < end_block)
1011				set_buffer_mapped(bh);
1012		}
1013		block++;
1014		bh = bh->b_this_page;
1015	} while (bh != head);
1016
1017	/*
1018	 * Caller needs to validate requested block against end of device.
1019	 */
1020	return end_block;
1021}
1022
1023/*
1024 * Create the page-cache folio that contains the requested block.
1025 *
1026 * This is used purely for blockdev mappings.
1027 *
1028 * Returns false if we have a failure which cannot be cured by retrying
1029 * without sleeping.  Returns true if we succeeded, or the caller should retry.
1030 */
1031static bool grow_dev_folio(struct block_device *bdev, sector_t block,
1032		pgoff_t index, unsigned size, gfp_t gfp)
 
1033{
1034	struct address_space *mapping = bdev->bd_mapping;
1035	struct folio *folio;
1036	struct buffer_head *bh;
1037	sector_t end_block = 0;
 
 
1038
1039	folio = __filemap_get_folio(mapping, index,
1040			FGP_LOCK | FGP_ACCESSED | FGP_CREAT, gfp);
1041	if (IS_ERR(folio))
1042		return false;
1043
1044	bh = folio_buffers(folio);
1045	if (bh) {
1046		if (bh->b_size == size) {
1047			end_block = folio_init_buffers(folio, bdev, size);
1048			goto unlock;
1049		}
 
1050
1051		/*
1052		 * Retrying may succeed; for example the folio may finish
1053		 * writeback, or buffers may be cleaned.  This should not
1054		 * happen very often; maybe we have old buffers attached to
1055		 * this blockdev's page cache and we're trying to change
1056		 * the block size?
1057		 */
1058		if (!try_to_free_buffers(folio)) {
1059			end_block = ~0ULL;
1060			goto unlock;
 
1061		}
 
 
1062	}
1063
1064	bh = folio_alloc_buffers(folio, size, gfp | __GFP_ACCOUNT);
1065	if (!bh)
1066		goto unlock;
 
1067
1068	/*
1069	 * Link the folio to the buffers and initialise them.  Take the
1070	 * lock to be atomic wrt __find_get_block(), which does not
1071	 * run under the folio lock.
1072	 */
1073	spin_lock(&mapping->i_private_lock);
1074	link_dev_buffers(folio, bh);
1075	end_block = folio_init_buffers(folio, bdev, size);
1076	spin_unlock(&mapping->i_private_lock);
1077unlock:
1078	folio_unlock(folio);
1079	folio_put(folio);
1080	return block < end_block;
 
 
 
1081}
1082
1083/*
1084 * Create buffers for the specified block device block's folio.  If
1085 * that folio was dirty, the buffers are set dirty also.  Returns false
1086 * if we've hit a permanent error.
1087 */
1088static bool grow_buffers(struct block_device *bdev, sector_t block,
1089		unsigned size, gfp_t gfp)
1090{
1091	loff_t pos;
 
 
 
 
 
 
 
 
1092
1093	/*
1094	 * Check for a block which lies outside our maximum possible
1095	 * pagecache index.
1096	 */
1097	if (check_mul_overflow(block, (sector_t)size, &pos) || pos > MAX_LFS_FILESIZE) {
1098		printk(KERN_ERR "%s: requested out-of-range block %llu for device %pg\n",
 
1099			__func__, (unsigned long long)block,
1100			bdev);
1101		return false;
1102	}
1103
1104	/* Create a folio with the proper size buffers */
1105	return grow_dev_folio(bdev, block, pos / PAGE_SIZE, size, gfp);
1106}
1107
1108static struct buffer_head *
1109__getblk_slow(struct block_device *bdev, sector_t block,
1110	     unsigned size, gfp_t gfp)
1111{
1112	/* Size must be multiple of hard sectorsize */
1113	if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
1114			(size < 512 || size > PAGE_SIZE))) {
1115		printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1116					size);
1117		printk(KERN_ERR "logical block size: %d\n",
1118					bdev_logical_block_size(bdev));
1119
1120		dump_stack();
1121		return NULL;
1122	}
1123
1124	for (;;) {
1125		struct buffer_head *bh;
 
1126
1127		bh = __find_get_block(bdev, block, size);
1128		if (bh)
1129			return bh;
1130
1131		if (!grow_buffers(bdev, block, size, gfp))
 
1132			return NULL;
1133	}
1134}
1135
1136/*
1137 * The relationship between dirty buffers and dirty pages:
1138 *
1139 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1140 * the page is tagged dirty in the page cache.
1141 *
1142 * At all times, the dirtiness of the buffers represents the dirtiness of
1143 * subsections of the page.  If the page has buffers, the page dirty bit is
1144 * merely a hint about the true dirty state.
1145 *
1146 * When a page is set dirty in its entirety, all its buffers are marked dirty
1147 * (if the page has buffers).
1148 *
1149 * When a buffer is marked dirty, its page is dirtied, but the page's other
1150 * buffers are not.
1151 *
1152 * Also.  When blockdev buffers are explicitly read with bread(), they
1153 * individually become uptodate.  But their backing page remains not
1154 * uptodate - even if all of its buffers are uptodate.  A subsequent
1155 * block_read_full_folio() against that folio will discover all the uptodate
1156 * buffers, will set the folio uptodate and will perform no I/O.
1157 */
1158
1159/**
1160 * mark_buffer_dirty - mark a buffer_head as needing writeout
1161 * @bh: the buffer_head to mark dirty
1162 *
1163 * mark_buffer_dirty() will set the dirty bit against the buffer, then set
1164 * its backing page dirty, then tag the page as dirty in the page cache
1165 * and then attach the address_space's inode to its superblock's dirty
1166 * inode list.
1167 *
1168 * mark_buffer_dirty() is atomic.  It takes bh->b_folio->mapping->i_private_lock,
1169 * i_pages lock and mapping->host->i_lock.
1170 */
1171void mark_buffer_dirty(struct buffer_head *bh)
1172{
1173	WARN_ON_ONCE(!buffer_uptodate(bh));
1174
1175	trace_block_dirty_buffer(bh);
1176
1177	/*
1178	 * Very *carefully* optimize the it-is-already-dirty case.
1179	 *
1180	 * Don't let the final "is it dirty" escape to before we
1181	 * perhaps modified the buffer.
1182	 */
1183	if (buffer_dirty(bh)) {
1184		smp_mb();
1185		if (buffer_dirty(bh))
1186			return;
1187	}
1188
1189	if (!test_set_buffer_dirty(bh)) {
1190		struct folio *folio = bh->b_folio;
1191		struct address_space *mapping = NULL;
1192
1193		if (!folio_test_set_dirty(folio)) {
1194			mapping = folio->mapping;
 
1195			if (mapping)
1196				__folio_mark_dirty(folio, mapping, 0);
1197		}
 
1198		if (mapping)
1199			__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
1200	}
1201}
1202EXPORT_SYMBOL(mark_buffer_dirty);
1203
1204void mark_buffer_write_io_error(struct buffer_head *bh)
1205{
1206	set_buffer_write_io_error(bh);
1207	/* FIXME: do we need to set this in both places? */
1208	if (bh->b_folio && bh->b_folio->mapping)
1209		mapping_set_error(bh->b_folio->mapping, -EIO);
1210	if (bh->b_assoc_map) {
1211		mapping_set_error(bh->b_assoc_map, -EIO);
1212		errseq_set(&bh->b_assoc_map->host->i_sb->s_wb_err, -EIO);
1213	}
1214}
1215EXPORT_SYMBOL(mark_buffer_write_io_error);
1216
1217/**
1218 * __brelse - Release a buffer.
1219 * @bh: The buffer to release.
1220 *
1221 * This variant of brelse() can be called if @bh is guaranteed to not be NULL.
 
1222 */
1223void __brelse(struct buffer_head *bh)
1224{
1225	if (atomic_read(&bh->b_count)) {
1226		put_bh(bh);
1227		return;
1228	}
1229	WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1230}
1231EXPORT_SYMBOL(__brelse);
1232
1233/**
1234 * __bforget - Discard any dirty data in a buffer.
1235 * @bh: The buffer to forget.
1236 *
1237 * This variant of bforget() can be called if @bh is guaranteed to not
1238 * be NULL.
1239 */
1240void __bforget(struct buffer_head *bh)
1241{
1242	clear_buffer_dirty(bh);
1243	if (bh->b_assoc_map) {
1244		struct address_space *buffer_mapping = bh->b_folio->mapping;
1245
1246		spin_lock(&buffer_mapping->i_private_lock);
1247		list_del_init(&bh->b_assoc_buffers);
1248		bh->b_assoc_map = NULL;
1249		spin_unlock(&buffer_mapping->i_private_lock);
1250	}
1251	__brelse(bh);
1252}
1253EXPORT_SYMBOL(__bforget);
1254
1255static struct buffer_head *__bread_slow(struct buffer_head *bh)
1256{
1257	lock_buffer(bh);
1258	if (buffer_uptodate(bh)) {
1259		unlock_buffer(bh);
1260		return bh;
1261	} else {
1262		get_bh(bh);
1263		bh->b_end_io = end_buffer_read_sync;
1264		submit_bh(REQ_OP_READ, bh);
1265		wait_on_buffer(bh);
1266		if (buffer_uptodate(bh))
1267			return bh;
1268	}
1269	brelse(bh);
1270	return NULL;
1271}
1272
1273/*
1274 * Per-cpu buffer LRU implementation.  To reduce the cost of __find_get_block().
1275 * The bhs[] array is sorted - newest buffer is at bhs[0].  Buffers have their
1276 * refcount elevated by one when they're in an LRU.  A buffer can only appear
1277 * once in a particular CPU's LRU.  A single buffer can be present in multiple
1278 * CPU's LRUs at the same time.
1279 *
1280 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1281 * sb_find_get_block().
1282 *
1283 * The LRUs themselves only need locking against invalidate_bh_lrus.  We use
1284 * a local interrupt disable for that.
1285 */
1286
1287#define BH_LRU_SIZE	16
1288
1289struct bh_lru {
1290	struct buffer_head *bhs[BH_LRU_SIZE];
1291};
1292
1293static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1294
1295#ifdef CONFIG_SMP
1296#define bh_lru_lock()	local_irq_disable()
1297#define bh_lru_unlock()	local_irq_enable()
1298#else
1299#define bh_lru_lock()	preempt_disable()
1300#define bh_lru_unlock()	preempt_enable()
1301#endif
1302
1303static inline void check_irqs_on(void)
1304{
1305#ifdef irqs_disabled
1306	BUG_ON(irqs_disabled());
1307#endif
1308}
1309
1310/*
1311 * Install a buffer_head into this cpu's LRU.  If not already in the LRU, it is
1312 * inserted at the front, and the buffer_head at the back if any is evicted.
1313 * Or, if already in the LRU it is moved to the front.
1314 */
1315static void bh_lru_install(struct buffer_head *bh)
1316{
1317	struct buffer_head *evictee = bh;
1318	struct bh_lru *b;
1319	int i;
1320
1321	check_irqs_on();
1322	bh_lru_lock();
1323
1324	/*
1325	 * the refcount of buffer_head in bh_lru prevents dropping the
1326	 * attached page(i.e., try_to_free_buffers) so it could cause
1327	 * failing page migration.
1328	 * Skip putting upcoming bh into bh_lru until migration is done.
1329	 */
1330	if (lru_cache_disabled() || cpu_is_isolated(smp_processor_id())) {
1331		bh_lru_unlock();
1332		return;
1333	}
1334
1335	b = this_cpu_ptr(&bh_lrus);
1336	for (i = 0; i < BH_LRU_SIZE; i++) {
1337		swap(evictee, b->bhs[i]);
1338		if (evictee == bh) {
1339			bh_lru_unlock();
1340			return;
1341		}
1342	}
1343
1344	get_bh(bh);
1345	bh_lru_unlock();
1346	brelse(evictee);
1347}
1348
1349/*
1350 * Look up the bh in this cpu's LRU.  If it's there, move it to the head.
1351 */
1352static struct buffer_head *
1353lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
1354{
1355	struct buffer_head *ret = NULL;
1356	unsigned int i;
1357
1358	check_irqs_on();
1359	bh_lru_lock();
1360	if (cpu_is_isolated(smp_processor_id())) {
1361		bh_lru_unlock();
1362		return NULL;
1363	}
1364	for (i = 0; i < BH_LRU_SIZE; i++) {
1365		struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
1366
1367		if (bh && bh->b_blocknr == block && bh->b_bdev == bdev &&
1368		    bh->b_size == size) {
1369			if (i) {
1370				while (i) {
1371					__this_cpu_write(bh_lrus.bhs[i],
1372						__this_cpu_read(bh_lrus.bhs[i - 1]));
1373					i--;
1374				}
1375				__this_cpu_write(bh_lrus.bhs[0], bh);
1376			}
1377			get_bh(bh);
1378			ret = bh;
1379			break;
1380		}
1381	}
1382	bh_lru_unlock();
1383	return ret;
1384}
1385
1386/*
1387 * Perform a pagecache lookup for the matching buffer.  If it's there, refresh
1388 * it in the LRU and mark it as accessed.  If it is not present then return
1389 * NULL
1390 */
1391struct buffer_head *
1392__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
1393{
1394	struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1395
1396	if (bh == NULL) {
1397		/* __find_get_block_slow will mark the page accessed */
1398		bh = __find_get_block_slow(bdev, block);
1399		if (bh)
1400			bh_lru_install(bh);
1401	} else
1402		touch_buffer(bh);
1403
1404	return bh;
1405}
1406EXPORT_SYMBOL(__find_get_block);
1407
1408/**
1409 * bdev_getblk - Get a buffer_head in a block device's buffer cache.
1410 * @bdev: The block device.
1411 * @block: The block number.
1412 * @size: The size of buffer_heads for this @bdev.
1413 * @gfp: The memory allocation flags to use.
1414 *
1415 * The returned buffer head has its reference count incremented, but is
1416 * not locked.  The caller should call brelse() when it has finished
1417 * with the buffer.  The buffer may not be uptodate.  If needed, the
1418 * caller can bring it uptodate either by reading it or overwriting it.
1419 *
1420 * Return: The buffer head, or NULL if memory could not be allocated.
 
1421 */
1422struct buffer_head *bdev_getblk(struct block_device *bdev, sector_t block,
1423		unsigned size, gfp_t gfp)
 
1424{
1425	struct buffer_head *bh = __find_get_block(bdev, block, size);
1426
1427	might_alloc(gfp);
1428	if (bh)
1429		return bh;
1430
1431	return __getblk_slow(bdev, block, size, gfp);
1432}
1433EXPORT_SYMBOL(bdev_getblk);
1434
1435/*
1436 * Do async read-ahead on a buffer..
1437 */
1438void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
1439{
1440	struct buffer_head *bh = bdev_getblk(bdev, block, size,
1441			GFP_NOWAIT | __GFP_MOVABLE);
1442
1443	if (likely(bh)) {
1444		bh_readahead(bh, REQ_RAHEAD);
1445		brelse(bh);
1446	}
1447}
1448EXPORT_SYMBOL(__breadahead);
1449
1450/**
1451 * __bread_gfp() - Read a block.
1452 * @bdev: The block device to read from.
1453 * @block: Block number in units of block size.
1454 * @size: The block size of this device in bytes.
1455 * @gfp: Not page allocation flags; see below.
1456 *
1457 * You are not expected to call this function.  You should use one of
1458 * sb_bread(), sb_bread_unmovable() or __bread().
1459 *
1460 * Read a specified block, and return the buffer head that refers to it.
1461 * If @gfp is 0, the memory will be allocated using the block device's
1462 * default GFP flags.  If @gfp is __GFP_MOVABLE, the memory may be
1463 * allocated from a movable area.  Do not pass in a complete set of
1464 * GFP flags.
1465 *
1466 * The returned buffer head has its refcount increased.  The caller should
1467 * call brelse() when it has finished with the buffer.
1468 *
1469 * Context: May sleep waiting for I/O.
1470 * Return: NULL if the block was unreadable.
1471 */
1472struct buffer_head *__bread_gfp(struct block_device *bdev, sector_t block,
1473		unsigned size, gfp_t gfp)
 
1474{
1475	struct buffer_head *bh;
1476
1477	gfp |= mapping_gfp_constraint(bdev->bd_mapping, ~__GFP_FS);
1478
1479	/*
1480	 * Prefer looping in the allocator rather than here, at least that
1481	 * code knows what it's doing.
1482	 */
1483	gfp |= __GFP_NOFAIL;
1484
1485	bh = bdev_getblk(bdev, block, size, gfp);
1486
1487	if (likely(bh) && !buffer_uptodate(bh))
1488		bh = __bread_slow(bh);
1489	return bh;
1490}
1491EXPORT_SYMBOL(__bread_gfp);
1492
1493static void __invalidate_bh_lrus(struct bh_lru *b)
1494{
1495	int i;
1496
1497	for (i = 0; i < BH_LRU_SIZE; i++) {
1498		brelse(b->bhs[i]);
1499		b->bhs[i] = NULL;
1500	}
1501}
1502/*
1503 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1504 * This doesn't race because it runs in each cpu either in irq
1505 * or with preempt disabled.
1506 */
1507static void invalidate_bh_lru(void *arg)
1508{
1509	struct bh_lru *b = &get_cpu_var(bh_lrus);
 
1510
1511	__invalidate_bh_lrus(b);
 
 
 
1512	put_cpu_var(bh_lrus);
1513}
1514
1515bool has_bh_in_lru(int cpu, void *dummy)
1516{
1517	struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
1518	int i;
1519	
1520	for (i = 0; i < BH_LRU_SIZE; i++) {
1521		if (b->bhs[i])
1522			return true;
1523	}
1524
1525	return false;
1526}
1527
1528void invalidate_bh_lrus(void)
1529{
1530	on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1);
1531}
1532EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
1533
1534/*
1535 * It's called from workqueue context so we need a bh_lru_lock to close
1536 * the race with preemption/irq.
1537 */
1538void invalidate_bh_lrus_cpu(void)
1539{
1540	struct bh_lru *b;
1541
1542	bh_lru_lock();
1543	b = this_cpu_ptr(&bh_lrus);
1544	__invalidate_bh_lrus(b);
1545	bh_lru_unlock();
1546}
1547
1548void folio_set_bh(struct buffer_head *bh, struct folio *folio,
1549		  unsigned long offset)
1550{
1551	bh->b_folio = folio;
1552	BUG_ON(offset >= folio_size(folio));
1553	if (folio_test_highmem(folio))
1554		/*
1555		 * This catches illegal uses and preserves the offset:
1556		 */
1557		bh->b_data = (char *)(0 + offset);
1558	else
1559		bh->b_data = folio_address(folio) + offset;
1560}
1561EXPORT_SYMBOL(folio_set_bh);
1562
1563/*
1564 * Called when truncating a buffer on a page completely.
1565 */
1566
1567/* Bits that are cleared during an invalidate */
1568#define BUFFER_FLAGS_DISCARD \
1569	(1 << BH_Mapped | 1 << BH_New | 1 << BH_Req | \
1570	 1 << BH_Delay | 1 << BH_Unwritten)
1571
1572static void discard_buffer(struct buffer_head * bh)
1573{
1574	unsigned long b_state;
1575
1576	lock_buffer(bh);
1577	clear_buffer_dirty(bh);
1578	bh->b_bdev = NULL;
1579	b_state = READ_ONCE(bh->b_state);
1580	do {
1581	} while (!try_cmpxchg(&bh->b_state, &b_state,
1582			      b_state & ~BUFFER_FLAGS_DISCARD));
 
 
 
 
1583	unlock_buffer(bh);
1584}
1585
1586/**
1587 * block_invalidate_folio - Invalidate part or all of a buffer-backed folio.
1588 * @folio: The folio which is affected.
 
1589 * @offset: start of the range to invalidate
1590 * @length: length of the range to invalidate
1591 *
1592 * block_invalidate_folio() is called when all or part of the folio has been
1593 * invalidated by a truncate operation.
1594 *
1595 * block_invalidate_folio() does not have to release all buffers, but it must
1596 * ensure that no dirty buffer is left outside @offset and that no I/O
1597 * is underway against any of the blocks which are outside the truncation
1598 * point.  Because the caller is about to free (and possibly reuse) those
1599 * blocks on-disk.
1600 */
1601void block_invalidate_folio(struct folio *folio, size_t offset, size_t length)
 
1602{
1603	struct buffer_head *head, *bh, *next;
1604	size_t curr_off = 0;
1605	size_t stop = length + offset;
1606
1607	BUG_ON(!folio_test_locked(folio));
 
 
1608
1609	/*
1610	 * Check for overflow
1611	 */
1612	BUG_ON(stop > folio_size(folio) || stop < length);
1613
1614	head = folio_buffers(folio);
1615	if (!head)
1616		return;
1617
 
1618	bh = head;
1619	do {
1620		size_t next_off = curr_off + bh->b_size;
1621		next = bh->b_this_page;
1622
1623		/*
1624		 * Are we still fully in range ?
1625		 */
1626		if (next_off > stop)
1627			goto out;
1628
1629		/*
1630		 * is this block fully invalidated?
1631		 */
1632		if (offset <= curr_off)
1633			discard_buffer(bh);
1634		curr_off = next_off;
1635		bh = next;
1636	} while (bh != head);
1637
1638	/*
1639	 * We release buffers only if the entire folio is being invalidated.
1640	 * The get_block cached value has been unconditionally invalidated,
1641	 * so real IO is not possible anymore.
1642	 */
1643	if (length == folio_size(folio))
1644		filemap_release_folio(folio, 0);
1645out:
1646	folio_clear_mappedtodisk(folio);
1647	return;
1648}
1649EXPORT_SYMBOL(block_invalidate_folio);
 
1650
1651/*
1652 * We attach and possibly dirty the buffers atomically wrt
1653 * block_dirty_folio() via i_private_lock.  try_to_free_buffers
1654 * is already excluded via the folio lock.
1655 */
1656struct buffer_head *create_empty_buffers(struct folio *folio,
1657		unsigned long blocksize, unsigned long b_state)
1658{
1659	struct buffer_head *bh, *head, *tail;
1660	gfp_t gfp = GFP_NOFS | __GFP_ACCOUNT | __GFP_NOFAIL;
1661
1662	head = folio_alloc_buffers(folio, blocksize, gfp);
1663	bh = head;
1664	do {
1665		bh->b_state |= b_state;
1666		tail = bh;
1667		bh = bh->b_this_page;
1668	} while (bh);
1669	tail->b_this_page = head;
1670
1671	spin_lock(&folio->mapping->i_private_lock);
1672	if (folio_test_uptodate(folio) || folio_test_dirty(folio)) {
1673		bh = head;
1674		do {
1675			if (folio_test_dirty(folio))
1676				set_buffer_dirty(bh);
1677			if (folio_test_uptodate(folio))
1678				set_buffer_uptodate(bh);
1679			bh = bh->b_this_page;
1680		} while (bh != head);
1681	}
1682	folio_attach_private(folio, head);
1683	spin_unlock(&folio->mapping->i_private_lock);
1684
1685	return head;
1686}
1687EXPORT_SYMBOL(create_empty_buffers);
1688
1689/**
1690 * clean_bdev_aliases: clean a range of buffers in block device
1691 * @bdev: Block device to clean buffers in
1692 * @block: Start of a range of blocks to clean
1693 * @len: Number of blocks to clean
1694 *
1695 * We are taking a range of blocks for data and we don't want writeback of any
1696 * buffer-cache aliases starting from return from this function and until the
1697 * moment when something will explicitly mark the buffer dirty (hopefully that
1698 * will not happen until we will free that block ;-) We don't even need to mark
1699 * it not-uptodate - nobody can expect anything from a newly allocated buffer
1700 * anyway. We used to use unmap_buffer() for such invalidation, but that was
1701 * wrong. We definitely don't want to mark the alias unmapped, for example - it
1702 * would confuse anyone who might pick it with bread() afterwards...
1703 *
1704 * Also..  Note that bforget() doesn't lock the buffer.  So there can be
1705 * writeout I/O going on against recently-freed buffers.  We don't wait on that
1706 * I/O in bforget() - it's more efficient to wait on the I/O only if we really
1707 * need to.  That happens here.
1708 */
1709void clean_bdev_aliases(struct block_device *bdev, sector_t block, sector_t len)
1710{
1711	struct address_space *bd_mapping = bdev->bd_mapping;
1712	const int blkbits = bd_mapping->host->i_blkbits;
1713	struct folio_batch fbatch;
1714	pgoff_t index = ((loff_t)block << blkbits) / PAGE_SIZE;
1715	pgoff_t end;
1716	int i, count;
1717	struct buffer_head *bh;
1718	struct buffer_head *head;
1719
1720	end = ((loff_t)(block + len - 1) << blkbits) / PAGE_SIZE;
1721	folio_batch_init(&fbatch);
1722	while (filemap_get_folios(bd_mapping, &index, end, &fbatch)) {
1723		count = folio_batch_count(&fbatch);
1724		for (i = 0; i < count; i++) {
1725			struct folio *folio = fbatch.folios[i];
1726
1727			if (!folio_buffers(folio))
1728				continue;
1729			/*
1730			 * We use folio lock instead of bd_mapping->i_private_lock
1731			 * to pin buffers here since we can afford to sleep and
1732			 * it scales better than a global spinlock lock.
1733			 */
1734			folio_lock(folio);
1735			/* Recheck when the folio is locked which pins bhs */
1736			head = folio_buffers(folio);
1737			if (!head)
1738				goto unlock_page;
 
1739			bh = head;
1740			do {
1741				if (!buffer_mapped(bh) || (bh->b_blocknr < block))
1742					goto next;
1743				if (bh->b_blocknr >= block + len)
1744					break;
1745				clear_buffer_dirty(bh);
1746				wait_on_buffer(bh);
1747				clear_buffer_req(bh);
1748next:
1749				bh = bh->b_this_page;
1750			} while (bh != head);
1751unlock_page:
1752			folio_unlock(folio);
1753		}
1754		folio_batch_release(&fbatch);
1755		cond_resched();
1756		/* End of range already reached? */
1757		if (index > end || !index)
1758			break;
1759	}
1760}
1761EXPORT_SYMBOL(clean_bdev_aliases);
1762
1763static struct buffer_head *folio_create_buffers(struct folio *folio,
1764						struct inode *inode,
1765						unsigned int b_state)
 
 
 
 
 
 
1766{
1767	struct buffer_head *bh;
 
1768
1769	BUG_ON(!folio_test_locked(folio));
 
 
1770
1771	bh = folio_buffers(folio);
1772	if (!bh)
1773		bh = create_empty_buffers(folio,
1774				1 << READ_ONCE(inode->i_blkbits), b_state);
1775	return bh;
1776}
1777
1778/*
1779 * NOTE! All mapped/uptodate combinations are valid:
1780 *
1781 *	Mapped	Uptodate	Meaning
1782 *
1783 *	No	No		"unknown" - must do get_block()
1784 *	No	Yes		"hole" - zero-filled
1785 *	Yes	No		"allocated" - allocated on disk, not read in
1786 *	Yes	Yes		"valid" - allocated and up-to-date in memory.
1787 *
1788 * "Dirty" is valid only with the last case (mapped+uptodate).
1789 */
1790
1791/*
1792 * While block_write_full_folio is writing back the dirty buffers under
1793 * the page lock, whoever dirtied the buffers may decide to clean them
1794 * again at any time.  We handle that by only looking at the buffer
1795 * state inside lock_buffer().
1796 *
1797 * If block_write_full_folio() is called for regular writeback
1798 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1799 * locked buffer.   This only can happen if someone has written the buffer
1800 * directly, with submit_bh().  At the address_space level PageWriteback
1801 * prevents this contention from occurring.
1802 *
1803 * If block_write_full_folio() is called with wbc->sync_mode ==
1804 * WB_SYNC_ALL, the writes are posted using REQ_SYNC; this
1805 * causes the writes to be flagged as synchronous writes.
1806 */
1807int __block_write_full_folio(struct inode *inode, struct folio *folio,
1808			get_block_t *get_block, struct writeback_control *wbc)
 
1809{
1810	int err;
1811	sector_t block;
1812	sector_t last_block;
1813	struct buffer_head *bh, *head;
1814	size_t blocksize;
1815	int nr_underway = 0;
1816	blk_opf_t write_flags = wbc_to_write_flags(wbc);
1817
1818	head = folio_create_buffers(folio, inode,
1819				    (1 << BH_Dirty) | (1 << BH_Uptodate));
1820
1821	/*
1822	 * Be very careful.  We have no exclusion from block_dirty_folio
1823	 * here, and the (potentially unmapped) buffers may become dirty at
1824	 * any time.  If a buffer becomes dirty here after we've inspected it
1825	 * then we just miss that fact, and the folio stays dirty.
1826	 *
1827	 * Buffers outside i_size may be dirtied by block_dirty_folio;
1828	 * handle that here by just cleaning them.
1829	 */
1830
1831	bh = head;
1832	blocksize = bh->b_size;
 
1833
1834	block = div_u64(folio_pos(folio), blocksize);
1835	last_block = div_u64(i_size_read(inode) - 1, blocksize);
1836
1837	/*
1838	 * Get all the dirty buffers mapped to disk addresses and
1839	 * handle any aliases from the underlying blockdev's mapping.
1840	 */
1841	do {
1842		if (block > last_block) {
1843			/*
1844			 * mapped buffers outside i_size will occur, because
1845			 * this folio can be outside i_size when there is a
1846			 * truncate in progress.
1847			 */
1848			/*
1849			 * The buffer was zeroed by block_write_full_folio()
1850			 */
1851			clear_buffer_dirty(bh);
1852			set_buffer_uptodate(bh);
1853		} else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1854			   buffer_dirty(bh)) {
1855			WARN_ON(bh->b_size != blocksize);
1856			err = get_block(inode, block, bh, 1);
1857			if (err)
1858				goto recover;
1859			clear_buffer_delay(bh);
1860			if (buffer_new(bh)) {
1861				/* blockdev mappings never come here */
1862				clear_buffer_new(bh);
1863				clean_bdev_bh_alias(bh);
1864			}
1865		}
1866		bh = bh->b_this_page;
1867		block++;
1868	} while (bh != head);
1869
1870	do {
1871		if (!buffer_mapped(bh))
1872			continue;
1873		/*
1874		 * If it's a fully non-blocking write attempt and we cannot
1875		 * lock the buffer then redirty the folio.  Note that this can
1876		 * potentially cause a busy-wait loop from writeback threads
1877		 * and kswapd activity, but those code paths have their own
1878		 * higher-level throttling.
1879		 */
1880		if (wbc->sync_mode != WB_SYNC_NONE) {
1881			lock_buffer(bh);
1882		} else if (!trylock_buffer(bh)) {
1883			folio_redirty_for_writepage(wbc, folio);
1884			continue;
1885		}
1886		if (test_clear_buffer_dirty(bh)) {
1887			mark_buffer_async_write_endio(bh,
1888				end_buffer_async_write);
1889		} else {
1890			unlock_buffer(bh);
1891		}
1892	} while ((bh = bh->b_this_page) != head);
1893
1894	/*
1895	 * The folio and its buffers are protected by the writeback flag,
1896	 * so we can drop the bh refcounts early.
1897	 */
1898	BUG_ON(folio_test_writeback(folio));
1899	folio_start_writeback(folio);
1900
1901	do {
1902		struct buffer_head *next = bh->b_this_page;
1903		if (buffer_async_write(bh)) {
1904			submit_bh_wbc(REQ_OP_WRITE | write_flags, bh,
1905				      inode->i_write_hint, wbc);
1906			nr_underway++;
1907		}
1908		bh = next;
1909	} while (bh != head);
1910	folio_unlock(folio);
1911
1912	err = 0;
1913done:
1914	if (nr_underway == 0) {
1915		/*
1916		 * The folio was marked dirty, but the buffers were
1917		 * clean.  Someone wrote them back by hand with
1918		 * write_dirty_buffer/submit_bh.  A rare case.
1919		 */
1920		folio_end_writeback(folio);
1921
1922		/*
1923		 * The folio and buffer_heads can be released at any time from
1924		 * here on.
1925		 */
1926	}
1927	return err;
1928
1929recover:
1930	/*
1931	 * ENOSPC, or some other error.  We may already have added some
1932	 * blocks to the file, so we need to write these out to avoid
1933	 * exposing stale data.
1934	 * The folio is currently locked and not marked for writeback
1935	 */
1936	bh = head;
1937	/* Recovery: lock and submit the mapped buffers */
1938	do {
1939		if (buffer_mapped(bh) && buffer_dirty(bh) &&
1940		    !buffer_delay(bh)) {
1941			lock_buffer(bh);
1942			mark_buffer_async_write_endio(bh,
1943				end_buffer_async_write);
1944		} else {
1945			/*
1946			 * The buffer may have been set dirty during
1947			 * attachment to a dirty folio.
1948			 */
1949			clear_buffer_dirty(bh);
1950		}
1951	} while ((bh = bh->b_this_page) != head);
1952	BUG_ON(folio_test_writeback(folio));
1953	mapping_set_error(folio->mapping, err);
1954	folio_start_writeback(folio);
 
1955	do {
1956		struct buffer_head *next = bh->b_this_page;
1957		if (buffer_async_write(bh)) {
1958			clear_buffer_dirty(bh);
1959			submit_bh_wbc(REQ_OP_WRITE | write_flags, bh,
1960				      inode->i_write_hint, wbc);
1961			nr_underway++;
1962		}
1963		bh = next;
1964	} while (bh != head);
1965	folio_unlock(folio);
1966	goto done;
1967}
1968EXPORT_SYMBOL(__block_write_full_folio);
1969
1970/*
1971 * If a folio has any new buffers, zero them out here, and mark them uptodate
1972 * and dirty so they'll be written out (in order to prevent uninitialised
1973 * block data from leaking). And clear the new bit.
1974 */
1975void folio_zero_new_buffers(struct folio *folio, size_t from, size_t to)
1976{
1977	size_t block_start, block_end;
1978	struct buffer_head *head, *bh;
1979
1980	BUG_ON(!folio_test_locked(folio));
1981	head = folio_buffers(folio);
1982	if (!head)
1983		return;
1984
1985	bh = head;
1986	block_start = 0;
1987	do {
1988		block_end = block_start + bh->b_size;
1989
1990		if (buffer_new(bh)) {
1991			if (block_end > from && block_start < to) {
1992				if (!folio_test_uptodate(folio)) {
1993					size_t start, xend;
1994
1995					start = max(from, block_start);
1996					xend = min(to, block_end);
1997
1998					folio_zero_segment(folio, start, xend);
1999					set_buffer_uptodate(bh);
2000				}
2001
2002				clear_buffer_new(bh);
2003				mark_buffer_dirty(bh);
2004			}
2005		}
2006
2007		block_start = block_end;
2008		bh = bh->b_this_page;
2009	} while (bh != head);
2010}
2011EXPORT_SYMBOL(folio_zero_new_buffers);
2012
2013static int
2014iomap_to_bh(struct inode *inode, sector_t block, struct buffer_head *bh,
2015		const struct iomap *iomap)
2016{
2017	loff_t offset = (loff_t)block << inode->i_blkbits;
2018
2019	bh->b_bdev = iomap->bdev;
2020
2021	/*
2022	 * Block points to offset in file we need to map, iomap contains
2023	 * the offset at which the map starts. If the map ends before the
2024	 * current block, then do not map the buffer and let the caller
2025	 * handle it.
2026	 */
2027	if (offset >= iomap->offset + iomap->length)
2028		return -EIO;
2029
2030	switch (iomap->type) {
2031	case IOMAP_HOLE:
2032		/*
2033		 * If the buffer is not up to date or beyond the current EOF,
2034		 * we need to mark it as new to ensure sub-block zeroing is
2035		 * executed if necessary.
2036		 */
2037		if (!buffer_uptodate(bh) ||
2038		    (offset >= i_size_read(inode)))
2039			set_buffer_new(bh);
2040		return 0;
2041	case IOMAP_DELALLOC:
2042		if (!buffer_uptodate(bh) ||
2043		    (offset >= i_size_read(inode)))
2044			set_buffer_new(bh);
2045		set_buffer_uptodate(bh);
2046		set_buffer_mapped(bh);
2047		set_buffer_delay(bh);
2048		return 0;
2049	case IOMAP_UNWRITTEN:
2050		/*
2051		 * For unwritten regions, we always need to ensure that regions
2052		 * in the block we are not writing to are zeroed. Mark the
2053		 * buffer as new to ensure this.
2054		 */
2055		set_buffer_new(bh);
2056		set_buffer_unwritten(bh);
2057		fallthrough;
2058	case IOMAP_MAPPED:
2059		if ((iomap->flags & IOMAP_F_NEW) ||
2060		    offset >= i_size_read(inode)) {
2061			/*
2062			 * This can happen if truncating the block device races
2063			 * with the check in the caller as i_size updates on
2064			 * block devices aren't synchronized by i_rwsem for
2065			 * block devices.
2066			 */
2067			if (S_ISBLK(inode->i_mode))
2068				return -EIO;
2069			set_buffer_new(bh);
2070		}
2071		bh->b_blocknr = (iomap->addr + offset - iomap->offset) >>
2072				inode->i_blkbits;
2073		set_buffer_mapped(bh);
2074		return 0;
2075	default:
2076		WARN_ON_ONCE(1);
2077		return -EIO;
2078	}
2079}
2080
2081int __block_write_begin_int(struct folio *folio, loff_t pos, unsigned len,
2082		get_block_t *get_block, const struct iomap *iomap)
2083{
2084	size_t from = offset_in_folio(folio, pos);
2085	size_t to = from + len;
2086	struct inode *inode = folio->mapping->host;
2087	size_t block_start, block_end;
2088	sector_t block;
2089	int err = 0;
2090	size_t blocksize;
2091	struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
2092
2093	BUG_ON(!folio_test_locked(folio));
2094	BUG_ON(to > folio_size(folio));
 
2095	BUG_ON(from > to);
2096
2097	head = folio_create_buffers(folio, inode, 0);
2098	blocksize = head->b_size;
2099	block = div_u64(folio_pos(folio), blocksize);
2100
2101	for (bh = head, block_start = 0; bh != head || !block_start;
 
 
2102	    block++, block_start=block_end, bh = bh->b_this_page) {
2103		block_end = block_start + blocksize;
2104		if (block_end <= from || block_start >= to) {
2105			if (folio_test_uptodate(folio)) {
2106				if (!buffer_uptodate(bh))
2107					set_buffer_uptodate(bh);
2108			}
2109			continue;
2110		}
2111		if (buffer_new(bh))
2112			clear_buffer_new(bh);
2113		if (!buffer_mapped(bh)) {
2114			WARN_ON(bh->b_size != blocksize);
2115			if (get_block)
2116				err = get_block(inode, block, bh, 1);
2117			else
2118				err = iomap_to_bh(inode, block, bh, iomap);
2119			if (err)
2120				break;
 
2121
2122			if (buffer_new(bh)) {
2123				clean_bdev_bh_alias(bh);
2124				if (folio_test_uptodate(folio)) {
2125					clear_buffer_new(bh);
2126					set_buffer_uptodate(bh);
2127					mark_buffer_dirty(bh);
2128					continue;
2129				}
2130				if (block_end > to || block_start < from)
2131					folio_zero_segments(folio,
2132						to, block_end,
2133						block_start, from);
2134				continue;
2135			}
2136		}
2137		if (folio_test_uptodate(folio)) {
2138			if (!buffer_uptodate(bh))
2139				set_buffer_uptodate(bh);
2140			continue; 
2141		}
2142		if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
2143		    !buffer_unwritten(bh) &&
2144		     (block_start < from || block_end > to)) {
2145			bh_read_nowait(bh, 0);
2146			*wait_bh++=bh;
2147		}
2148	}
2149	/*
2150	 * If we issued read requests - let them complete.
2151	 */
2152	while(wait_bh > wait) {
2153		wait_on_buffer(*--wait_bh);
2154		if (!buffer_uptodate(*wait_bh))
2155			err = -EIO;
2156	}
2157	if (unlikely(err))
2158		folio_zero_new_buffers(folio, from, to);
2159	return err;
2160}
2161
2162int __block_write_begin(struct folio *folio, loff_t pos, unsigned len,
2163		get_block_t *get_block)
2164{
2165	return __block_write_begin_int(folio, pos, len, get_block, NULL);
2166}
2167EXPORT_SYMBOL(__block_write_begin);
2168
2169static void __block_commit_write(struct folio *folio, size_t from, size_t to)
 
2170{
2171	size_t block_start, block_end;
2172	bool partial = false;
2173	unsigned blocksize;
2174	struct buffer_head *bh, *head;
2175
2176	bh = head = folio_buffers(folio);
2177	if (!bh)
2178		return;
2179	blocksize = bh->b_size;
2180
2181	block_start = 0;
2182	do {
2183		block_end = block_start + blocksize;
2184		if (block_end <= from || block_start >= to) {
2185			if (!buffer_uptodate(bh))
2186				partial = true;
2187		} else {
2188			set_buffer_uptodate(bh);
2189			mark_buffer_dirty(bh);
2190		}
2191		if (buffer_new(bh))
2192			clear_buffer_new(bh);
2193
2194		block_start = block_end;
2195		bh = bh->b_this_page;
2196	} while (bh != head);
2197
2198	/*
2199	 * If this is a partial write which happened to make all buffers
2200	 * uptodate then we can optimize away a bogus read_folio() for
2201	 * the next read(). Here we 'discover' whether the folio went
2202	 * uptodate as a result of this (potentially partial) write.
2203	 */
2204	if (!partial)
2205		folio_mark_uptodate(folio);
 
2206}
2207
2208/*
2209 * block_write_begin takes care of the basic task of block allocation and
2210 * bringing partial write blocks uptodate first.
2211 *
2212 * The filesystem needs to handle block truncation upon failure.
2213 */
2214int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
2215		struct folio **foliop, get_block_t *get_block)
2216{
2217	pgoff_t index = pos >> PAGE_SHIFT;
2218	struct folio *folio;
2219	int status;
2220
2221	folio = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,
2222			mapping_gfp_mask(mapping));
2223	if (IS_ERR(folio))
2224		return PTR_ERR(folio);
2225
2226	status = __block_write_begin_int(folio, pos, len, get_block, NULL);
2227	if (unlikely(status)) {
2228		folio_unlock(folio);
2229		folio_put(folio);
2230		folio = NULL;
2231	}
2232
2233	*foliop = folio;
2234	return status;
2235}
2236EXPORT_SYMBOL(block_write_begin);
2237
2238int block_write_end(struct file *file, struct address_space *mapping,
2239			loff_t pos, unsigned len, unsigned copied,
2240			struct folio *folio, void *fsdata)
2241{
2242	size_t start = pos - folio_pos(folio);
 
 
 
2243
2244	if (unlikely(copied < len)) {
2245		/*
2246		 * The buffers that were written will now be uptodate, so
2247		 * we don't have to worry about a read_folio reading them
2248		 * and overwriting a partial write. However if we have
2249		 * encountered a short write and only partially written
2250		 * into a buffer, it will not be marked uptodate, so a
2251		 * read_folio might come in and destroy our partial write.
2252		 *
2253		 * Do the simplest thing, and just treat any short write to a
2254		 * non uptodate folio as a zero-length write, and force the
2255		 * caller to redo the whole thing.
2256		 */
2257		if (!folio_test_uptodate(folio))
2258			copied = 0;
2259
2260		folio_zero_new_buffers(folio, start+copied, start+len);
2261	}
2262	flush_dcache_folio(folio);
2263
2264	/* This could be a short (even 0-length) commit */
2265	__block_commit_write(folio, start, start + copied);
2266
2267	return copied;
2268}
2269EXPORT_SYMBOL(block_write_end);
2270
2271int generic_write_end(struct file *file, struct address_space *mapping,
2272			loff_t pos, unsigned len, unsigned copied,
2273			struct folio *folio, void *fsdata)
2274{
2275	struct inode *inode = mapping->host;
2276	loff_t old_size = inode->i_size;
2277	bool i_size_changed = false;
2278
2279	copied = block_write_end(file, mapping, pos, len, copied, folio, fsdata);
2280
2281	/*
2282	 * No need to use i_size_read() here, the i_size cannot change under us
2283	 * because we hold i_rwsem.
2284	 *
2285	 * But it's important to update i_size while still holding folio lock:
2286	 * page writeout could otherwise come in and zero beyond i_size.
2287	 */
2288	if (pos + copied > inode->i_size) {
2289		i_size_write(inode, pos + copied);
2290		i_size_changed = true;
2291	}
2292
2293	folio_unlock(folio);
2294	folio_put(folio);
2295
2296	if (old_size < pos)
2297		pagecache_isize_extended(inode, old_size, pos);
2298	/*
2299	 * Don't mark the inode dirty under page lock. First, it unnecessarily
2300	 * makes the holding time of page lock longer. Second, it forces lock
2301	 * ordering of page lock and transaction start for journaling
2302	 * filesystems.
2303	 */
2304	if (i_size_changed)
2305		mark_inode_dirty(inode);
 
2306	return copied;
2307}
2308EXPORT_SYMBOL(generic_write_end);
2309
2310/*
2311 * block_is_partially_uptodate checks whether buffers within a folio are
2312 * uptodate or not.
2313 *
2314 * Returns true if all buffers which correspond to the specified part
2315 * of the folio are uptodate.
2316 */
2317bool block_is_partially_uptodate(struct folio *folio, size_t from, size_t count)
 
2318{
2319	unsigned block_start, block_end, blocksize;
2320	unsigned to;
2321	struct buffer_head *bh, *head;
2322	bool ret = true;
 
 
 
2323
2324	head = folio_buffers(folio);
2325	if (!head)
2326		return false;
2327	blocksize = head->b_size;
2328	to = min_t(unsigned, folio_size(folio) - from, count);
2329	to = from + to;
2330	if (from < blocksize && to > folio_size(folio) - blocksize)
2331		return false;
2332
2333	bh = head;
2334	block_start = 0;
2335	do {
2336		block_end = block_start + blocksize;
2337		if (block_end > from && block_start < to) {
2338			if (!buffer_uptodate(bh)) {
2339				ret = false;
2340				break;
2341			}
2342			if (block_end >= to)
2343				break;
2344		}
2345		block_start = block_end;
2346		bh = bh->b_this_page;
2347	} while (bh != head);
2348
2349	return ret;
2350}
2351EXPORT_SYMBOL(block_is_partially_uptodate);
2352
2353/*
2354 * Generic "read_folio" function for block devices that have the normal
2355 * get_block functionality. This is most of the block device filesystems.
2356 * Reads the folio asynchronously --- the unlock_buffer() and
2357 * set/clear_buffer_uptodate() functions propagate buffer state into the
2358 * folio once IO has completed.
2359 */
2360int block_read_full_folio(struct folio *folio, get_block_t *get_block)
2361{
2362	struct inode *inode = folio->mapping->host;
2363	sector_t iblock, lblock;
2364	struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2365	size_t blocksize;
2366	int nr, i;
2367	int fully_mapped = 1;
2368	bool page_error = false;
2369	loff_t limit = i_size_read(inode);
2370
2371	/* This is needed for ext4. */
2372	if (IS_ENABLED(CONFIG_FS_VERITY) && IS_VERITY(inode))
2373		limit = inode->i_sb->s_maxbytes;
2374
2375	VM_BUG_ON_FOLIO(folio_test_large(folio), folio);
2376
2377	head = folio_create_buffers(folio, inode, 0);
2378	blocksize = head->b_size;
 
2379
2380	iblock = div_u64(folio_pos(folio), blocksize);
2381	lblock = div_u64(limit + blocksize - 1, blocksize);
2382	bh = head;
2383	nr = 0;
2384	i = 0;
2385
2386	do {
2387		if (buffer_uptodate(bh))
2388			continue;
2389
2390		if (!buffer_mapped(bh)) {
2391			int err = 0;
2392
2393			fully_mapped = 0;
2394			if (iblock < lblock) {
2395				WARN_ON(bh->b_size != blocksize);
2396				err = get_block(inode, iblock, bh, 0);
2397				if (err)
2398					page_error = true;
2399			}
2400			if (!buffer_mapped(bh)) {
2401				folio_zero_range(folio, i * blocksize,
2402						blocksize);
2403				if (!err)
2404					set_buffer_uptodate(bh);
2405				continue;
2406			}
2407			/*
2408			 * get_block() might have updated the buffer
2409			 * synchronously
2410			 */
2411			if (buffer_uptodate(bh))
2412				continue;
2413		}
2414		arr[nr++] = bh;
2415	} while (i++, iblock++, (bh = bh->b_this_page) != head);
2416
2417	if (fully_mapped)
2418		folio_set_mappedtodisk(folio);
2419
2420	if (!nr) {
2421		/*
2422		 * All buffers are uptodate or get_block() returned an
2423		 * error when trying to map them - we can finish the read.
2424		 */
2425		folio_end_read(folio, !page_error);
 
 
2426		return 0;
2427	}
2428
2429	/* Stage two: lock the buffers */
2430	for (i = 0; i < nr; i++) {
2431		bh = arr[i];
2432		lock_buffer(bh);
2433		mark_buffer_async_read(bh);
2434	}
2435
2436	/*
2437	 * Stage 3: start the IO.  Check for uptodateness
2438	 * inside the buffer lock in case another process reading
2439	 * the underlying blockdev brought it uptodate (the sct fix).
2440	 */
2441	for (i = 0; i < nr; i++) {
2442		bh = arr[i];
2443		if (buffer_uptodate(bh))
2444			end_buffer_async_read(bh, 1);
2445		else
2446			submit_bh(REQ_OP_READ, bh);
2447	}
2448	return 0;
2449}
2450EXPORT_SYMBOL(block_read_full_folio);
2451
2452/* utility function for filesystems that need to do work on expanding
2453 * truncates.  Uses filesystem pagecache writes to allow the filesystem to
2454 * deal with the hole.  
2455 */
2456int generic_cont_expand_simple(struct inode *inode, loff_t size)
2457{
2458	struct address_space *mapping = inode->i_mapping;
2459	const struct address_space_operations *aops = mapping->a_ops;
2460	struct folio *folio;
2461	void *fsdata = NULL;
2462	int err;
2463
2464	err = inode_newsize_ok(inode, size);
2465	if (err)
2466		goto out;
2467
2468	err = aops->write_begin(NULL, mapping, size, 0, &folio, &fsdata);
 
2469	if (err)
2470		goto out;
2471
2472	err = aops->write_end(NULL, mapping, size, 0, 0, folio, fsdata);
2473	BUG_ON(err > 0);
2474
2475out:
2476	return err;
2477}
2478EXPORT_SYMBOL(generic_cont_expand_simple);
2479
2480static int cont_expand_zero(struct file *file, struct address_space *mapping,
2481			    loff_t pos, loff_t *bytes)
2482{
2483	struct inode *inode = mapping->host;
2484	const struct address_space_operations *aops = mapping->a_ops;
2485	unsigned int blocksize = i_blocksize(inode);
2486	struct folio *folio;
2487	void *fsdata = NULL;
2488	pgoff_t index, curidx;
2489	loff_t curpos;
2490	unsigned zerofrom, offset, len;
2491	int err = 0;
2492
2493	index = pos >> PAGE_SHIFT;
2494	offset = pos & ~PAGE_MASK;
2495
2496	while (index > (curidx = (curpos = *bytes)>>PAGE_SHIFT)) {
2497		zerofrom = curpos & ~PAGE_MASK;
2498		if (zerofrom & (blocksize-1)) {
2499			*bytes |= (blocksize-1);
2500			(*bytes)++;
2501		}
2502		len = PAGE_SIZE - zerofrom;
2503
2504		err = aops->write_begin(file, mapping, curpos, len,
2505					    &folio, &fsdata);
2506		if (err)
2507			goto out;
2508		folio_zero_range(folio, offset_in_folio(folio, curpos), len);
2509		err = aops->write_end(file, mapping, curpos, len, len,
2510						folio, fsdata);
2511		if (err < 0)
2512			goto out;
2513		BUG_ON(err != len);
2514		err = 0;
2515
2516		balance_dirty_pages_ratelimited(mapping);
2517
2518		if (fatal_signal_pending(current)) {
2519			err = -EINTR;
2520			goto out;
2521		}
2522	}
2523
2524	/* page covers the boundary, find the boundary offset */
2525	if (index == curidx) {
2526		zerofrom = curpos & ~PAGE_MASK;
2527		/* if we will expand the thing last block will be filled */
2528		if (offset <= zerofrom) {
2529			goto out;
2530		}
2531		if (zerofrom & (blocksize-1)) {
2532			*bytes |= (blocksize-1);
2533			(*bytes)++;
2534		}
2535		len = offset - zerofrom;
2536
2537		err = aops->write_begin(file, mapping, curpos, len,
2538					    &folio, &fsdata);
2539		if (err)
2540			goto out;
2541		folio_zero_range(folio, offset_in_folio(folio, curpos), len);
2542		err = aops->write_end(file, mapping, curpos, len, len,
2543						folio, fsdata);
2544		if (err < 0)
2545			goto out;
2546		BUG_ON(err != len);
2547		err = 0;
2548	}
2549out:
2550	return err;
2551}
2552
2553/*
2554 * For moronic filesystems that do not allow holes in file.
2555 * We may have to extend the file.
2556 */
2557int cont_write_begin(struct file *file, struct address_space *mapping,
2558			loff_t pos, unsigned len,
2559			struct folio **foliop, void **fsdata,
2560			get_block_t *get_block, loff_t *bytes)
2561{
2562	struct inode *inode = mapping->host;
2563	unsigned int blocksize = i_blocksize(inode);
2564	unsigned int zerofrom;
2565	int err;
2566
2567	err = cont_expand_zero(file, mapping, pos, bytes);
2568	if (err)
2569		return err;
2570
2571	zerofrom = *bytes & ~PAGE_MASK;
2572	if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2573		*bytes |= (blocksize-1);
2574		(*bytes)++;
2575	}
2576
2577	return block_write_begin(mapping, pos, len, foliop, get_block);
2578}
2579EXPORT_SYMBOL(cont_write_begin);
2580
2581void block_commit_write(struct page *page, unsigned from, unsigned to)
2582{
2583	struct folio *folio = page_folio(page);
2584	__block_commit_write(folio, from, to);
 
2585}
2586EXPORT_SYMBOL(block_commit_write);
2587
2588/*
2589 * block_page_mkwrite() is not allowed to change the file size as it gets
2590 * called from a page fault handler when a page is first dirtied. Hence we must
2591 * be careful to check for EOF conditions here. We set the page up correctly
2592 * for a written page which means we get ENOSPC checking when writing into
2593 * holes and correct delalloc and unwritten extent mapping on filesystems that
2594 * support these features.
2595 *
2596 * We are not allowed to take the i_mutex here so we have to play games to
2597 * protect against truncate races as the page could now be beyond EOF.  Because
2598 * truncate writes the inode size before removing pages, once we have the
2599 * page lock we can determine safely if the page is beyond EOF. If it is not
2600 * beyond EOF, then the page is guaranteed safe against truncation until we
2601 * unlock the page.
2602 *
2603 * Direct callers of this function should protect against filesystem freezing
2604 * using sb_start_pagefault() - sb_end_pagefault() functions.
2605 */
2606int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2607			 get_block_t get_block)
2608{
2609	struct folio *folio = page_folio(vmf->page);
2610	struct inode *inode = file_inode(vma->vm_file);
2611	unsigned long end;
2612	loff_t size;
2613	int ret;
2614
2615	folio_lock(folio);
2616	size = i_size_read(inode);
2617	if ((folio->mapping != inode->i_mapping) ||
2618	    (folio_pos(folio) >= size)) {
2619		/* We overload EFAULT to mean page got truncated */
2620		ret = -EFAULT;
2621		goto out_unlock;
2622	}
2623
2624	end = folio_size(folio);
2625	/* folio is wholly or partially inside EOF */
2626	if (folio_pos(folio) + end > size)
2627		end = size - folio_pos(folio);
2628
2629	ret = __block_write_begin_int(folio, 0, end, get_block, NULL);
2630	if (unlikely(ret))
2631		goto out_unlock;
2632
2633	__block_commit_write(folio, 0, end);
 
 
2634
2635	folio_mark_dirty(folio);
2636	folio_wait_stable(folio);
 
 
2637	return 0;
2638out_unlock:
2639	folio_unlock(folio);
2640	return ret;
2641}
2642EXPORT_SYMBOL(block_page_mkwrite);
2643
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2644int block_truncate_page(struct address_space *mapping,
2645			loff_t from, get_block_t *get_block)
2646{
2647	pgoff_t index = from >> PAGE_SHIFT;
 
2648	unsigned blocksize;
2649	sector_t iblock;
2650	size_t offset, length, pos;
2651	struct inode *inode = mapping->host;
2652	struct folio *folio;
2653	struct buffer_head *bh;
2654	int err = 0;
2655
2656	blocksize = i_blocksize(inode);
2657	length = from & (blocksize - 1);
2658
2659	/* Block boundary? Nothing to do */
2660	if (!length)
2661		return 0;
2662
2663	length = blocksize - length;
2664	iblock = ((loff_t)index * PAGE_SIZE) >> inode->i_blkbits;
 
 
 
 
 
2665
2666	folio = filemap_grab_folio(mapping, index);
2667	if (IS_ERR(folio))
2668		return PTR_ERR(folio);
2669
2670	bh = folio_buffers(folio);
2671	if (!bh)
2672		bh = create_empty_buffers(folio, blocksize, 0);
2673
2674	/* Find the buffer that contains "offset" */
2675	offset = offset_in_folio(folio, from);
2676	pos = blocksize;
2677	while (offset >= pos) {
2678		bh = bh->b_this_page;
2679		iblock++;
2680		pos += blocksize;
2681	}
2682
 
2683	if (!buffer_mapped(bh)) {
2684		WARN_ON(bh->b_size != blocksize);
2685		err = get_block(inode, iblock, bh, 0);
2686		if (err)
2687			goto unlock;
2688		/* unmapped? It's a hole - nothing to do */
2689		if (!buffer_mapped(bh))
2690			goto unlock;
2691	}
2692
2693	/* Ok, it's mapped. Make sure it's up-to-date */
2694	if (folio_test_uptodate(folio))
2695		set_buffer_uptodate(bh);
2696
2697	if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
2698		err = bh_read(bh, 0);
 
 
2699		/* Uhhuh. Read error. Complain and punt. */
2700		if (err < 0)
2701			goto unlock;
2702	}
2703
2704	folio_zero_range(folio, offset, length);
2705	mark_buffer_dirty(bh);
 
2706
2707unlock:
2708	folio_unlock(folio);
2709	folio_put(folio);
2710
2711	return err;
2712}
2713EXPORT_SYMBOL(block_truncate_page);
2714
2715/*
2716 * The generic ->writepage function for buffer-backed address_spaces
2717 */
2718int block_write_full_folio(struct folio *folio, struct writeback_control *wbc,
2719		void *get_block)
2720{
2721	struct inode * const inode = folio->mapping->host;
2722	loff_t i_size = i_size_read(inode);
 
 
2723
2724	/* Is the folio fully inside i_size? */
2725	if (folio_pos(folio) + folio_size(folio) <= i_size)
2726		return __block_write_full_folio(inode, folio, get_block, wbc);
2727
2728	/* Is the folio fully outside i_size? (truncate in progress) */
2729	if (folio_pos(folio) >= i_size) {
2730		folio_unlock(folio);
 
 
 
 
 
 
 
 
2731		return 0; /* don't care */
2732	}
2733
2734	/*
2735	 * The folio straddles i_size.  It must be zeroed out on each and every
2736	 * writepage invocation because it may be mmapped.  "A file is mapped
2737	 * in multiples of the page size.  For a file that is not a multiple of
2738	 * the page size, the remaining memory is zeroed when mapped, and
2739	 * writes to that region are not written out to the file."
2740	 */
2741	folio_zero_segment(folio, offset_in_folio(folio, i_size),
2742			folio_size(folio));
2743	return __block_write_full_folio(inode, folio, get_block, wbc);
2744}
 
2745
2746sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2747			    get_block_t *get_block)
2748{
2749	struct inode *inode = mapping->host;
2750	struct buffer_head tmp = {
2751		.b_size = i_blocksize(inode),
2752	};
2753
2754	get_block(inode, block, &tmp, 0);
2755	return tmp.b_blocknr;
2756}
2757EXPORT_SYMBOL(generic_block_bmap);
2758
2759static void end_bio_bh_io_sync(struct bio *bio)
2760{
2761	struct buffer_head *bh = bio->bi_private;
2762
2763	if (unlikely(bio_flagged(bio, BIO_QUIET)))
2764		set_bit(BH_Quiet, &bh->b_state);
2765
2766	bh->b_end_io(bh, !bio->bi_status);
2767	bio_put(bio);
2768}
2769
2770static void submit_bh_wbc(blk_opf_t opf, struct buffer_head *bh,
2771			  enum rw_hint write_hint,
2772			  struct writeback_control *wbc)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2773{
2774	const enum req_op op = opf & REQ_OP_MASK;
2775	struct bio *bio;
2776
2777	BUG_ON(!buffer_locked(bh));
2778	BUG_ON(!buffer_mapped(bh));
2779	BUG_ON(!bh->b_end_io);
2780	BUG_ON(buffer_delay(bh));
2781	BUG_ON(buffer_unwritten(bh));
2782
2783	/*
2784	 * Only clear out a write error when rewriting
2785	 */
2786	if (test_set_buffer_req(bh) && (op == REQ_OP_WRITE))
2787		clear_buffer_write_io_error(bh);
2788
2789	if (buffer_meta(bh))
2790		opf |= REQ_META;
2791	if (buffer_prio(bh))
2792		opf |= REQ_PRIO;
2793
2794	bio = bio_alloc(bh->b_bdev, 1, opf, GFP_NOIO);
2795
2796	fscrypt_set_bio_crypt_ctx_bh(bio, bh, GFP_NOIO);
 
 
 
2797
2798	bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
 
2799	bio->bi_write_hint = write_hint;
2800
2801	bio_add_folio_nofail(bio, bh->b_folio, bh->b_size, bh_offset(bh));
 
2802
2803	bio->bi_end_io = end_bio_bh_io_sync;
2804	bio->bi_private = bh;
2805
2806	/* Take care of bh's that straddle the end of the device */
2807	guard_bio_eod(bio);
2808
2809	if (wbc) {
2810		wbc_init_bio(wbc, bio);
2811		wbc_account_cgroup_owner(wbc, bh->b_folio, bh->b_size);
2812	}
 
2813
2814	submit_bio(bio);
 
2815}
2816
2817void submit_bh(blk_opf_t opf, struct buffer_head *bh)
2818{
2819	submit_bh_wbc(opf, bh, WRITE_LIFE_NOT_SET, NULL);
2820}
2821EXPORT_SYMBOL(submit_bh);
2822
2823void write_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2824{
2825	lock_buffer(bh);
2826	if (!test_clear_buffer_dirty(bh)) {
2827		unlock_buffer(bh);
2828		return;
2829	}
2830	bh->b_end_io = end_buffer_write_sync;
2831	get_bh(bh);
2832	submit_bh(REQ_OP_WRITE | op_flags, bh);
2833}
2834EXPORT_SYMBOL(write_dirty_buffer);
2835
2836/*
2837 * For a data-integrity writeout, we need to wait upon any in-progress I/O
2838 * and then start new I/O and then wait upon it.  The caller must have a ref on
2839 * the buffer_head.
2840 */
2841int __sync_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags)
2842{
 
 
2843	WARN_ON(atomic_read(&bh->b_count) < 1);
2844	lock_buffer(bh);
2845	if (test_clear_buffer_dirty(bh)) {
2846		/*
2847		 * The bh should be mapped, but it might not be if the
2848		 * device was hot-removed. Not much we can do but fail the I/O.
2849		 */
2850		if (!buffer_mapped(bh)) {
2851			unlock_buffer(bh);
2852			return -EIO;
2853		}
2854
2855		get_bh(bh);
2856		bh->b_end_io = end_buffer_write_sync;
2857		submit_bh(REQ_OP_WRITE | op_flags, bh);
2858		wait_on_buffer(bh);
2859		if (!buffer_uptodate(bh))
2860			return -EIO;
2861	} else {
2862		unlock_buffer(bh);
2863	}
2864	return 0;
2865}
2866EXPORT_SYMBOL(__sync_dirty_buffer);
2867
2868int sync_dirty_buffer(struct buffer_head *bh)
2869{
2870	return __sync_dirty_buffer(bh, REQ_SYNC);
2871}
2872EXPORT_SYMBOL(sync_dirty_buffer);
2873
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2874static inline int buffer_busy(struct buffer_head *bh)
2875{
2876	return atomic_read(&bh->b_count) |
2877		(bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
2878}
2879
2880static bool
2881drop_buffers(struct folio *folio, struct buffer_head **buffers_to_free)
2882{
2883	struct buffer_head *head = folio_buffers(folio);
2884	struct buffer_head *bh;
2885
2886	bh = head;
2887	do {
2888		if (buffer_busy(bh))
2889			goto failed;
2890		bh = bh->b_this_page;
2891	} while (bh != head);
2892
2893	do {
2894		struct buffer_head *next = bh->b_this_page;
2895
2896		if (bh->b_assoc_map)
2897			__remove_assoc_queue(bh);
2898		bh = next;
2899	} while (bh != head);
2900	*buffers_to_free = head;
2901	folio_detach_private(folio);
2902	return true;
2903failed:
2904	return false;
2905}
2906
2907/**
2908 * try_to_free_buffers - Release buffers attached to this folio.
2909 * @folio: The folio.
2910 *
2911 * If any buffers are in use (dirty, under writeback, elevated refcount),
2912 * no buffers will be freed.
2913 *
2914 * If the folio is dirty but all the buffers are clean then we need to
2915 * be sure to mark the folio clean as well.  This is because the folio
2916 * may be against a block device, and a later reattachment of buffers
2917 * to a dirty folio will set *all* buffers dirty.  Which would corrupt
2918 * filesystem data on the same device.
2919 *
2920 * The same applies to regular filesystem folios: if all the buffers are
2921 * clean then we set the folio clean and proceed.  To do that, we require
2922 * total exclusion from block_dirty_folio().  That is obtained with
2923 * i_private_lock.
2924 *
2925 * Exclusion against try_to_free_buffers may be obtained by either
2926 * locking the folio or by holding its mapping's i_private_lock.
2927 *
2928 * Context: Process context.  @folio must be locked.  Will not sleep.
2929 * Return: true if all buffers attached to this folio were freed.
2930 */
2931bool try_to_free_buffers(struct folio *folio)
2932{
2933	struct address_space * const mapping = folio->mapping;
2934	struct buffer_head *buffers_to_free = NULL;
2935	bool ret = 0;
2936
2937	BUG_ON(!folio_test_locked(folio));
2938	if (folio_test_writeback(folio))
2939		return false;
2940
2941	if (mapping == NULL) {		/* can this still happen? */
2942		ret = drop_buffers(folio, &buffers_to_free);
2943		goto out;
2944	}
2945
2946	spin_lock(&mapping->i_private_lock);
2947	ret = drop_buffers(folio, &buffers_to_free);
2948
2949	/*
2950	 * If the filesystem writes its buffers by hand (eg ext3)
2951	 * then we can have clean buffers against a dirty folio.  We
2952	 * clean the folio here; otherwise the VM will never notice
2953	 * that the filesystem did any IO at all.
2954	 *
2955	 * Also, during truncate, discard_buffer will have marked all
2956	 * the folio's buffers clean.  We discover that here and clean
2957	 * the folio also.
2958	 *
2959	 * i_private_lock must be held over this entire operation in order
2960	 * to synchronise against block_dirty_folio and prevent the
2961	 * dirty bit from being lost.
2962	 */
2963	if (ret)
2964		folio_cancel_dirty(folio);
2965	spin_unlock(&mapping->i_private_lock);
2966out:
2967	if (buffers_to_free) {
2968		struct buffer_head *bh = buffers_to_free;
2969
2970		do {
2971			struct buffer_head *next = bh->b_this_page;
2972			free_buffer_head(bh);
2973			bh = next;
2974		} while (bh != buffers_to_free);
2975	}
2976	return ret;
2977}
2978EXPORT_SYMBOL(try_to_free_buffers);
2979
2980/*
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2981 * Buffer-head allocation
2982 */
2983static struct kmem_cache *bh_cachep __ro_after_init;
2984
2985/*
2986 * Once the number of bh's in the machine exceeds this level, we start
2987 * stripping them in writeback.
2988 */
2989static unsigned long max_buffer_heads __ro_after_init;
2990
2991int buffer_heads_over_limit;
2992
2993struct bh_accounting {
2994	int nr;			/* Number of live bh's */
2995	int ratelimit;		/* Limit cacheline bouncing */
2996};
2997
2998static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
2999
3000static void recalc_bh_state(void)
3001{
3002	int i;
3003	int tot = 0;
3004
3005	if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
3006		return;
3007	__this_cpu_write(bh_accounting.ratelimit, 0);
3008	for_each_online_cpu(i)
3009		tot += per_cpu(bh_accounting, i).nr;
3010	buffer_heads_over_limit = (tot > max_buffer_heads);
3011}
3012
3013struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
3014{
3015	struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
3016	if (ret) {
3017		INIT_LIST_HEAD(&ret->b_assoc_buffers);
3018		spin_lock_init(&ret->b_uptodate_lock);
3019		preempt_disable();
3020		__this_cpu_inc(bh_accounting.nr);
3021		recalc_bh_state();
3022		preempt_enable();
3023	}
3024	return ret;
3025}
3026EXPORT_SYMBOL(alloc_buffer_head);
3027
3028void free_buffer_head(struct buffer_head *bh)
3029{
3030	BUG_ON(!list_empty(&bh->b_assoc_buffers));
3031	kmem_cache_free(bh_cachep, bh);
3032	preempt_disable();
3033	__this_cpu_dec(bh_accounting.nr);
3034	recalc_bh_state();
3035	preempt_enable();
3036}
3037EXPORT_SYMBOL(free_buffer_head);
3038
3039static int buffer_exit_cpu_dead(unsigned int cpu)
3040{
3041	int i;
3042	struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3043
3044	for (i = 0; i < BH_LRU_SIZE; i++) {
3045		brelse(b->bhs[i]);
3046		b->bhs[i] = NULL;
3047	}
3048	this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
3049	per_cpu(bh_accounting, cpu).nr = 0;
3050	return 0;
3051}
3052
3053/**
3054 * bh_uptodate_or_lock - Test whether the buffer is uptodate
3055 * @bh: struct buffer_head
3056 *
3057 * Return true if the buffer is up-to-date and false,
3058 * with the buffer locked, if not.
3059 */
3060int bh_uptodate_or_lock(struct buffer_head *bh)
3061{
3062	if (!buffer_uptodate(bh)) {
3063		lock_buffer(bh);
3064		if (!buffer_uptodate(bh))
3065			return 0;
3066		unlock_buffer(bh);
3067	}
3068	return 1;
3069}
3070EXPORT_SYMBOL(bh_uptodate_or_lock);
3071
3072/**
3073 * __bh_read - Submit read for a locked buffer
3074 * @bh: struct buffer_head
3075 * @op_flags: appending REQ_OP_* flags besides REQ_OP_READ
3076 * @wait: wait until reading finish
3077 *
3078 * Returns zero on success or don't wait, and -EIO on error.
3079 */
3080int __bh_read(struct buffer_head *bh, blk_opf_t op_flags, bool wait)
3081{
3082	int ret = 0;
3083
3084	BUG_ON(!buffer_locked(bh));
3085
 
 
 
 
 
3086	get_bh(bh);
3087	bh->b_end_io = end_buffer_read_sync;
3088	submit_bh(REQ_OP_READ | op_flags, bh);
3089	if (wait) {
3090		wait_on_buffer(bh);
3091		if (!buffer_uptodate(bh))
3092			ret = -EIO;
3093	}
3094	return ret;
3095}
3096EXPORT_SYMBOL(__bh_read);
3097
3098/**
3099 * __bh_read_batch - Submit read for a batch of unlocked buffers
3100 * @nr: entry number of the buffer batch
3101 * @bhs: a batch of struct buffer_head
3102 * @op_flags: appending REQ_OP_* flags besides REQ_OP_READ
3103 * @force_lock: force to get a lock on the buffer if set, otherwise drops any
3104 *              buffer that cannot lock.
3105 *
3106 * Returns zero on success or don't wait, and -EIO on error.
3107 */
3108void __bh_read_batch(int nr, struct buffer_head *bhs[],
3109		     blk_opf_t op_flags, bool force_lock)
3110{
3111	int i;
 
 
3112
3113	for (i = 0; i < nr; i++) {
3114		struct buffer_head *bh = bhs[i];
3115
3116		if (buffer_uptodate(bh))
 
 
 
3117			continue;
3118
3119		if (force_lock)
3120			lock_buffer(bh);
3121		else
3122			if (!trylock_buffer(bh))
3123				continue;
 
 
3124
3125		if (buffer_uptodate(bh)) {
3126			unlock_buffer(bh);
3127			continue;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
3128		}
 
 
3129
3130		bh->b_end_io = end_buffer_read_sync;
3131		get_bh(bh);
3132		submit_bh(REQ_OP_READ | op_flags, bh);
3133	}
 
 
 
 
 
 
 
 
3134}
3135EXPORT_SYMBOL(__bh_read_batch);
3136
3137void __init buffer_init(void)
3138{
3139	unsigned long nrpages;
3140	int ret;
3141
3142	bh_cachep = KMEM_CACHE(buffer_head,
3143				SLAB_RECLAIM_ACCOUNT|SLAB_PANIC);
 
 
 
 
3144	/*
3145	 * Limit the bh occupancy to 10% of ZONE_NORMAL
3146	 */
3147	nrpages = (nr_free_buffer_pages() * 10) / 100;
3148	max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3149	ret = cpuhp_setup_state_nocalls(CPUHP_FS_BUFF_DEAD, "fs/buffer:dead",
3150					NULL, buffer_exit_cpu_dead);
3151	WARN_ON(ret < 0);
3152}
v4.17
 
   1/*
   2 *  linux/fs/buffer.c
   3 *
   4 *  Copyright (C) 1991, 1992, 2002  Linus Torvalds
   5 */
   6
   7/*
   8 * Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95
   9 *
  10 * Removed a lot of unnecessary code and simplified things now that
  11 * the buffer cache isn't our primary cache - Andrew Tridgell 12/96
  12 *
  13 * Speed up hash, lru, and free list operations.  Use gfp() for allocating
  14 * hash table, use SLAB cache for buffer heads. SMP threading.  -DaveM
  15 *
  16 * Added 32k buffer block sizes - these are required older ARM systems. - RMK
  17 *
  18 * async buffer flushing, 1999 Andrea Arcangeli <andrea@suse.de>
  19 */
  20
  21#include <linux/kernel.h>
  22#include <linux/sched/signal.h>
  23#include <linux/syscalls.h>
  24#include <linux/fs.h>
  25#include <linux/iomap.h>
  26#include <linux/mm.h>
  27#include <linux/percpu.h>
  28#include <linux/slab.h>
  29#include <linux/capability.h>
  30#include <linux/blkdev.h>
  31#include <linux/file.h>
  32#include <linux/quotaops.h>
  33#include <linux/highmem.h>
  34#include <linux/export.h>
  35#include <linux/backing-dev.h>
  36#include <linux/writeback.h>
  37#include <linux/hash.h>
  38#include <linux/suspend.h>
  39#include <linux/buffer_head.h>
  40#include <linux/task_io_accounting_ops.h>
  41#include <linux/bio.h>
  42#include <linux/notifier.h>
  43#include <linux/cpu.h>
  44#include <linux/bitops.h>
  45#include <linux/mpage.h>
  46#include <linux/bit_spinlock.h>
  47#include <linux/pagevec.h>
 
  48#include <trace/events/block.h>
 
 
 
 
 
  49
  50static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
  51static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh,
  52			 enum rw_hint hint, struct writeback_control *wbc);
  53
  54#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
  55
  56inline void touch_buffer(struct buffer_head *bh)
  57{
  58	trace_block_touch_buffer(bh);
  59	mark_page_accessed(bh->b_page);
  60}
  61EXPORT_SYMBOL(touch_buffer);
  62
  63void __lock_buffer(struct buffer_head *bh)
  64{
  65	wait_on_bit_lock_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
  66}
  67EXPORT_SYMBOL(__lock_buffer);
  68
  69void unlock_buffer(struct buffer_head *bh)
  70{
  71	clear_bit_unlock(BH_Lock, &bh->b_state);
  72	smp_mb__after_atomic();
  73	wake_up_bit(&bh->b_state, BH_Lock);
  74}
  75EXPORT_SYMBOL(unlock_buffer);
  76
  77/*
  78 * Returns if the page has dirty or writeback buffers. If all the buffers
  79 * are unlocked and clean then the PageDirty information is stale. If
  80 * any of the pages are locked, it is assumed they are locked for IO.
  81 */
  82void buffer_check_dirty_writeback(struct page *page,
  83				     bool *dirty, bool *writeback)
  84{
  85	struct buffer_head *head, *bh;
  86	*dirty = false;
  87	*writeback = false;
  88
  89	BUG_ON(!PageLocked(page));
  90
  91	if (!page_has_buffers(page))
 
  92		return;
  93
  94	if (PageWriteback(page))
  95		*writeback = true;
  96
  97	head = page_buffers(page);
  98	bh = head;
  99	do {
 100		if (buffer_locked(bh))
 101			*writeback = true;
 102
 103		if (buffer_dirty(bh))
 104			*dirty = true;
 105
 106		bh = bh->b_this_page;
 107	} while (bh != head);
 108}
 109EXPORT_SYMBOL(buffer_check_dirty_writeback);
 110
 111/*
 112 * Block until a buffer comes unlocked.  This doesn't stop it
 113 * from becoming locked again - you have to lock it yourself
 114 * if you want to preserve its state.
 115 */
 116void __wait_on_buffer(struct buffer_head * bh)
 117{
 118	wait_on_bit_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
 119}
 120EXPORT_SYMBOL(__wait_on_buffer);
 121
 122static void
 123__clear_page_buffers(struct page *page)
 124{
 125	ClearPagePrivate(page);
 126	set_page_private(page, 0);
 127	put_page(page);
 128}
 129
 130static void buffer_io_error(struct buffer_head *bh, char *msg)
 131{
 132	if (!test_bit(BH_Quiet, &bh->b_state))
 133		printk_ratelimited(KERN_ERR
 134			"Buffer I/O error on dev %pg, logical block %llu%s\n",
 135			bh->b_bdev, (unsigned long long)bh->b_blocknr, msg);
 136}
 137
 138/*
 139 * End-of-IO handler helper function which does not touch the bh after
 140 * unlocking it.
 141 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
 142 * a race there is benign: unlock_buffer() only use the bh's address for
 143 * hashing after unlocking the buffer, so it doesn't actually touch the bh
 144 * itself.
 145 */
 146static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
 147{
 148	if (uptodate) {
 149		set_buffer_uptodate(bh);
 150	} else {
 151		/* This happens, due to failed read-ahead attempts. */
 152		clear_buffer_uptodate(bh);
 153	}
 154	unlock_buffer(bh);
 155}
 156
 157/*
 158 * Default synchronous end-of-IO handler..  Just mark it up-to-date and
 159 * unlock the buffer. This is what ll_rw_block uses too.
 160 */
 161void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
 162{
 163	__end_buffer_read_notouch(bh, uptodate);
 164	put_bh(bh);
 165}
 166EXPORT_SYMBOL(end_buffer_read_sync);
 167
 168void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
 169{
 170	if (uptodate) {
 171		set_buffer_uptodate(bh);
 172	} else {
 173		buffer_io_error(bh, ", lost sync page write");
 174		mark_buffer_write_io_error(bh);
 175		clear_buffer_uptodate(bh);
 176	}
 177	unlock_buffer(bh);
 178	put_bh(bh);
 179}
 180EXPORT_SYMBOL(end_buffer_write_sync);
 181
 182/*
 183 * Various filesystems appear to want __find_get_block to be non-blocking.
 184 * But it's the page lock which protects the buffers.  To get around this,
 185 * we get exclusion from try_to_free_buffers with the blockdev mapping's
 186 * private_lock.
 187 *
 188 * Hack idea: for the blockdev mapping, private_lock contention
 189 * may be quite high.  This code could TryLock the page, and if that
 190 * succeeds, there is no need to take private_lock.
 191 */
 192static struct buffer_head *
 193__find_get_block_slow(struct block_device *bdev, sector_t block)
 194{
 195	struct inode *bd_inode = bdev->bd_inode;
 196	struct address_space *bd_mapping = bd_inode->i_mapping;
 197	struct buffer_head *ret = NULL;
 198	pgoff_t index;
 199	struct buffer_head *bh;
 200	struct buffer_head *head;
 201	struct page *page;
 202	int all_mapped = 1;
 
 203
 204	index = block >> (PAGE_SHIFT - bd_inode->i_blkbits);
 205	page = find_get_page_flags(bd_mapping, index, FGP_ACCESSED);
 206	if (!page)
 207		goto out;
 208
 209	spin_lock(&bd_mapping->private_lock);
 210	if (!page_has_buffers(page))
 
 211		goto out_unlock;
 212	head = page_buffers(page);
 213	bh = head;
 214	do {
 215		if (!buffer_mapped(bh))
 216			all_mapped = 0;
 217		else if (bh->b_blocknr == block) {
 218			ret = bh;
 219			get_bh(bh);
 220			goto out_unlock;
 221		}
 222		bh = bh->b_this_page;
 223	} while (bh != head);
 224
 225	/* we might be here because some of the buffers on this page are
 226	 * not mapped.  This is due to various races between
 227	 * file io on the block device and getblk.  It gets dealt with
 228	 * elsewhere, don't buffer_error if we had some unmapped buffers
 229	 */
 230	if (all_mapped) {
 231		printk("__find_get_block_slow() failed. "
 232			"block=%llu, b_blocknr=%llu\n",
 233			(unsigned long long)block,
 234			(unsigned long long)bh->b_blocknr);
 235		printk("b_state=0x%08lx, b_size=%zu\n",
 236			bh->b_state, bh->b_size);
 237		printk("device %pg blocksize: %d\n", bdev,
 238			1 << bd_inode->i_blkbits);
 239	}
 240out_unlock:
 241	spin_unlock(&bd_mapping->private_lock);
 242	put_page(page);
 243out:
 244	return ret;
 245}
 246
 247/*
 248 * I/O completion handler for block_read_full_page() - pages
 249 * which come unlocked at the end of I/O.
 250 */
 251static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
 252{
 253	unsigned long flags;
 254	struct buffer_head *first;
 255	struct buffer_head *tmp;
 256	struct page *page;
 257	int page_uptodate = 1;
 258
 259	BUG_ON(!buffer_async_read(bh));
 260
 261	page = bh->b_page;
 262	if (uptodate) {
 263		set_buffer_uptodate(bh);
 264	} else {
 265		clear_buffer_uptodate(bh);
 266		buffer_io_error(bh, ", async page read");
 267		SetPageError(page);
 268	}
 269
 270	/*
 271	 * Be _very_ careful from here on. Bad things can happen if
 272	 * two buffer heads end IO at almost the same time and both
 273	 * decide that the page is now completely done.
 274	 */
 275	first = page_buffers(page);
 276	local_irq_save(flags);
 277	bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
 278	clear_buffer_async_read(bh);
 279	unlock_buffer(bh);
 280	tmp = bh;
 281	do {
 282		if (!buffer_uptodate(tmp))
 283			page_uptodate = 0;
 284		if (buffer_async_read(tmp)) {
 285			BUG_ON(!buffer_locked(tmp));
 286			goto still_busy;
 287		}
 288		tmp = tmp->b_this_page;
 289	} while (tmp != bh);
 290	bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
 291	local_irq_restore(flags);
 292
 293	/*
 294	 * If none of the buffers had errors and they are all
 295	 * uptodate then we can set the page uptodate.
 296	 */
 297	if (page_uptodate && !PageError(page))
 298		SetPageUptodate(page);
 299	unlock_page(page);
 300	return;
 301
 302still_busy:
 303	bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
 304	local_irq_restore(flags);
 305	return;
 306}
 307
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 308/*
 309 * Completion handler for block_write_full_page() - pages which are unlocked
 310 * during I/O, and which have PageWriteback cleared upon I/O completion.
 311 */
 312void end_buffer_async_write(struct buffer_head *bh, int uptodate)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 313{
 314	unsigned long flags;
 315	struct buffer_head *first;
 316	struct buffer_head *tmp;
 317	struct page *page;
 318
 319	BUG_ON(!buffer_async_write(bh));
 320
 321	page = bh->b_page;
 322	if (uptodate) {
 323		set_buffer_uptodate(bh);
 324	} else {
 325		buffer_io_error(bh, ", lost async page write");
 326		mark_buffer_write_io_error(bh);
 327		clear_buffer_uptodate(bh);
 328		SetPageError(page);
 329	}
 330
 331	first = page_buffers(page);
 332	local_irq_save(flags);
 333	bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
 334
 335	clear_buffer_async_write(bh);
 336	unlock_buffer(bh);
 337	tmp = bh->b_this_page;
 338	while (tmp != bh) {
 339		if (buffer_async_write(tmp)) {
 340			BUG_ON(!buffer_locked(tmp));
 341			goto still_busy;
 342		}
 343		tmp = tmp->b_this_page;
 344	}
 345	bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
 346	local_irq_restore(flags);
 347	end_page_writeback(page);
 348	return;
 349
 350still_busy:
 351	bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
 352	local_irq_restore(flags);
 353	return;
 354}
 355EXPORT_SYMBOL(end_buffer_async_write);
 356
 357/*
 358 * If a page's buffers are under async readin (end_buffer_async_read
 359 * completion) then there is a possibility that another thread of
 360 * control could lock one of the buffers after it has completed
 361 * but while some of the other buffers have not completed.  This
 362 * locked buffer would confuse end_buffer_async_read() into not unlocking
 363 * the page.  So the absence of BH_Async_Read tells end_buffer_async_read()
 364 * that this buffer is not under async I/O.
 365 *
 366 * The page comes unlocked when it has no locked buffer_async buffers
 367 * left.
 368 *
 369 * PageLocked prevents anyone starting new async I/O reads any of
 370 * the buffers.
 371 *
 372 * PageWriteback is used to prevent simultaneous writeout of the same
 373 * page.
 374 *
 375 * PageLocked prevents anyone from starting writeback of a page which is
 376 * under read I/O (PageWriteback is only ever set against a locked page).
 377 */
 378static void mark_buffer_async_read(struct buffer_head *bh)
 379{
 380	bh->b_end_io = end_buffer_async_read;
 381	set_buffer_async_read(bh);
 382}
 383
 384static void mark_buffer_async_write_endio(struct buffer_head *bh,
 385					  bh_end_io_t *handler)
 386{
 387	bh->b_end_io = handler;
 388	set_buffer_async_write(bh);
 389}
 390
 391void mark_buffer_async_write(struct buffer_head *bh)
 392{
 393	mark_buffer_async_write_endio(bh, end_buffer_async_write);
 394}
 395EXPORT_SYMBOL(mark_buffer_async_write);
 396
 397
 398/*
 399 * fs/buffer.c contains helper functions for buffer-backed address space's
 400 * fsync functions.  A common requirement for buffer-based filesystems is
 401 * that certain data from the backing blockdev needs to be written out for
 402 * a successful fsync().  For example, ext2 indirect blocks need to be
 403 * written back and waited upon before fsync() returns.
 404 *
 405 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
 406 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
 407 * management of a list of dependent buffers at ->i_mapping->private_list.
 408 *
 409 * Locking is a little subtle: try_to_free_buffers() will remove buffers
 410 * from their controlling inode's queue when they are being freed.  But
 411 * try_to_free_buffers() will be operating against the *blockdev* mapping
 412 * at the time, not against the S_ISREG file which depends on those buffers.
 413 * So the locking for private_list is via the private_lock in the address_space
 414 * which backs the buffers.  Which is different from the address_space 
 415 * against which the buffers are listed.  So for a particular address_space,
 416 * mapping->private_lock does *not* protect mapping->private_list!  In fact,
 417 * mapping->private_list will always be protected by the backing blockdev's
 418 * ->private_lock.
 419 *
 420 * Which introduces a requirement: all buffers on an address_space's
 421 * ->private_list must be from the same address_space: the blockdev's.
 422 *
 423 * address_spaces which do not place buffers at ->private_list via these
 424 * utility functions are free to use private_lock and private_list for
 425 * whatever they want.  The only requirement is that list_empty(private_list)
 426 * be true at clear_inode() time.
 427 *
 428 * FIXME: clear_inode should not call invalidate_inode_buffers().  The
 429 * filesystems should do that.  invalidate_inode_buffers() should just go
 430 * BUG_ON(!list_empty).
 431 *
 432 * FIXME: mark_buffer_dirty_inode() is a data-plane operation.  It should
 433 * take an address_space, not an inode.  And it should be called
 434 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
 435 * queued up.
 436 *
 437 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
 438 * list if it is already on a list.  Because if the buffer is on a list,
 439 * it *must* already be on the right one.  If not, the filesystem is being
 440 * silly.  This will save a ton of locking.  But first we have to ensure
 441 * that buffers are taken *off* the old inode's list when they are freed
 442 * (presumably in truncate).  That requires careful auditing of all
 443 * filesystems (do it inside bforget()).  It could also be done by bringing
 444 * b_inode back.
 445 */
 446
 447/*
 448 * The buffer's backing address_space's private_lock must be held
 449 */
 450static void __remove_assoc_queue(struct buffer_head *bh)
 451{
 452	list_del_init(&bh->b_assoc_buffers);
 453	WARN_ON(!bh->b_assoc_map);
 454	bh->b_assoc_map = NULL;
 455}
 456
 457int inode_has_buffers(struct inode *inode)
 458{
 459	return !list_empty(&inode->i_data.private_list);
 460}
 461
 462/*
 463 * osync is designed to support O_SYNC io.  It waits synchronously for
 464 * all already-submitted IO to complete, but does not queue any new
 465 * writes to the disk.
 466 *
 467 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
 468 * you dirty the buffers, and then use osync_inode_buffers to wait for
 469 * completion.  Any other dirty buffers which are not yet queued for
 470 * write will not be flushed to disk by the osync.
 471 */
 472static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
 473{
 474	struct buffer_head *bh;
 475	struct list_head *p;
 476	int err = 0;
 477
 478	spin_lock(lock);
 479repeat:
 480	list_for_each_prev(p, list) {
 481		bh = BH_ENTRY(p);
 482		if (buffer_locked(bh)) {
 483			get_bh(bh);
 484			spin_unlock(lock);
 485			wait_on_buffer(bh);
 486			if (!buffer_uptodate(bh))
 487				err = -EIO;
 488			brelse(bh);
 489			spin_lock(lock);
 490			goto repeat;
 491		}
 492	}
 493	spin_unlock(lock);
 494	return err;
 495}
 496
 497void emergency_thaw_bdev(struct super_block *sb)
 498{
 499	while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb))
 500		printk(KERN_WARNING "Emergency Thaw on %pg\n", sb->s_bdev);
 501}
 502
 503/**
 504 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
 505 * @mapping: the mapping which wants those buffers written
 506 *
 507 * Starts I/O against the buffers at mapping->private_list, and waits upon
 508 * that I/O.
 509 *
 510 * Basically, this is a convenience function for fsync().
 511 * @mapping is a file or directory which needs those buffers to be written for
 512 * a successful fsync().
 513 */
 514int sync_mapping_buffers(struct address_space *mapping)
 515{
 516	struct address_space *buffer_mapping = mapping->private_data;
 517
 518	if (buffer_mapping == NULL || list_empty(&mapping->private_list))
 519		return 0;
 520
 521	return fsync_buffers_list(&buffer_mapping->private_lock,
 522					&mapping->private_list);
 523}
 524EXPORT_SYMBOL(sync_mapping_buffers);
 525
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 526/*
 527 * Called when we've recently written block `bblock', and it is known that
 528 * `bblock' was for a buffer_boundary() buffer.  This means that the block at
 529 * `bblock + 1' is probably a dirty indirect block.  Hunt it down and, if it's
 530 * dirty, schedule it for IO.  So that indirects merge nicely with their data.
 531 */
 532void write_boundary_block(struct block_device *bdev,
 533			sector_t bblock, unsigned blocksize)
 534{
 535	struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
 536	if (bh) {
 537		if (buffer_dirty(bh))
 538			ll_rw_block(REQ_OP_WRITE, 0, 1, &bh);
 539		put_bh(bh);
 540	}
 541}
 542
 543void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
 544{
 545	struct address_space *mapping = inode->i_mapping;
 546	struct address_space *buffer_mapping = bh->b_page->mapping;
 547
 548	mark_buffer_dirty(bh);
 549	if (!mapping->private_data) {
 550		mapping->private_data = buffer_mapping;
 551	} else {
 552		BUG_ON(mapping->private_data != buffer_mapping);
 553	}
 554	if (!bh->b_assoc_map) {
 555		spin_lock(&buffer_mapping->private_lock);
 556		list_move_tail(&bh->b_assoc_buffers,
 557				&mapping->private_list);
 558		bh->b_assoc_map = mapping;
 559		spin_unlock(&buffer_mapping->private_lock);
 560	}
 561}
 562EXPORT_SYMBOL(mark_buffer_dirty_inode);
 563
 564/*
 565 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
 566 * dirty.
 567 *
 568 * If warn is true, then emit a warning if the page is not uptodate and has
 569 * not been truncated.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 570 *
 571 * The caller must hold lock_page_memcg().
 572 */
 573void __set_page_dirty(struct page *page, struct address_space *mapping,
 574			     int warn)
 575{
 576	unsigned long flags;
 
 577
 578	xa_lock_irqsave(&mapping->i_pages, flags);
 579	if (page->mapping) {	/* Race with truncate? */
 580		WARN_ON_ONCE(warn && !PageUptodate(page));
 581		account_page_dirtied(page, mapping);
 582		radix_tree_tag_set(&mapping->i_pages,
 583				page_index(page), PAGECACHE_TAG_DIRTY);
 584	}
 585	xa_unlock_irqrestore(&mapping->i_pages, flags);
 586}
 587EXPORT_SYMBOL_GPL(__set_page_dirty);
 588
 589/*
 590 * Add a page to the dirty page list.
 591 *
 592 * It is a sad fact of life that this function is called from several places
 593 * deeply under spinlocking.  It may not sleep.
 594 *
 595 * If the page has buffers, the uptodate buffers are set dirty, to preserve
 596 * dirty-state coherency between the page and the buffers.  It the page does
 597 * not have buffers then when they are later attached they will all be set
 598 * dirty.
 599 *
 600 * The buffers are dirtied before the page is dirtied.  There's a small race
 601 * window in which a writepage caller may see the page cleanness but not the
 602 * buffer dirtiness.  That's fine.  If this code were to set the page dirty
 603 * before the buffers, a concurrent writepage caller could clear the page dirty
 604 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
 605 * page on the dirty page list.
 606 *
 607 * We use private_lock to lock against try_to_free_buffers while using the
 608 * page's buffer list.  Also use this to protect against clean buffers being
 609 * added to the page after it was set dirty.
 610 *
 611 * FIXME: may need to call ->reservepage here as well.  That's rather up to the
 612 * address_space though.
 613 */
 614int __set_page_dirty_buffers(struct page *page)
 615{
 616	int newly_dirty;
 617	struct address_space *mapping = page_mapping(page);
 618
 619	if (unlikely(!mapping))
 620		return !TestSetPageDirty(page);
 621
 622	spin_lock(&mapping->private_lock);
 623	if (page_has_buffers(page)) {
 624		struct buffer_head *head = page_buffers(page);
 625		struct buffer_head *bh = head;
 626
 627		do {
 628			set_buffer_dirty(bh);
 629			bh = bh->b_this_page;
 630		} while (bh != head);
 631	}
 632	/*
 633	 * Lock out page->mem_cgroup migration to keep PageDirty
 634	 * synchronized with per-memcg dirty page counters.
 635	 */
 636	lock_page_memcg(page);
 637	newly_dirty = !TestSetPageDirty(page);
 638	spin_unlock(&mapping->private_lock);
 639
 640	if (newly_dirty)
 641		__set_page_dirty(page, mapping, 1);
 642
 643	unlock_page_memcg(page);
 644
 645	if (newly_dirty)
 646		__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
 647
 648	return newly_dirty;
 649}
 650EXPORT_SYMBOL(__set_page_dirty_buffers);
 651
 652/*
 653 * Write out and wait upon a list of buffers.
 654 *
 655 * We have conflicting pressures: we want to make sure that all
 656 * initially dirty buffers get waited on, but that any subsequently
 657 * dirtied buffers don't.  After all, we don't want fsync to last
 658 * forever if somebody is actively writing to the file.
 659 *
 660 * Do this in two main stages: first we copy dirty buffers to a
 661 * temporary inode list, queueing the writes as we go.  Then we clean
 662 * up, waiting for those writes to complete.
 663 * 
 664 * During this second stage, any subsequent updates to the file may end
 665 * up refiling the buffer on the original inode's dirty list again, so
 666 * there is a chance we will end up with a buffer queued for write but
 667 * not yet completed on that list.  So, as a final cleanup we go through
 668 * the osync code to catch these locked, dirty buffers without requeuing
 669 * any newly dirty buffers for write.
 670 */
 671static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
 672{
 673	struct buffer_head *bh;
 674	struct list_head tmp;
 675	struct address_space *mapping;
 676	int err = 0, err2;
 677	struct blk_plug plug;
 
 678
 679	INIT_LIST_HEAD(&tmp);
 680	blk_start_plug(&plug);
 681
 682	spin_lock(lock);
 683	while (!list_empty(list)) {
 684		bh = BH_ENTRY(list->next);
 685		mapping = bh->b_assoc_map;
 686		__remove_assoc_queue(bh);
 687		/* Avoid race with mark_buffer_dirty_inode() which does
 688		 * a lockless check and we rely on seeing the dirty bit */
 689		smp_mb();
 690		if (buffer_dirty(bh) || buffer_locked(bh)) {
 691			list_add(&bh->b_assoc_buffers, &tmp);
 692			bh->b_assoc_map = mapping;
 693			if (buffer_dirty(bh)) {
 694				get_bh(bh);
 695				spin_unlock(lock);
 696				/*
 697				 * Ensure any pending I/O completes so that
 698				 * write_dirty_buffer() actually writes the
 699				 * current contents - it is a noop if I/O is
 700				 * still in flight on potentially older
 701				 * contents.
 702				 */
 703				write_dirty_buffer(bh, REQ_SYNC);
 704
 705				/*
 706				 * Kick off IO for the previous mapping. Note
 707				 * that we will not run the very last mapping,
 708				 * wait_on_buffer() will do that for us
 709				 * through sync_buffer().
 710				 */
 711				brelse(bh);
 712				spin_lock(lock);
 713			}
 714		}
 715	}
 716
 717	spin_unlock(lock);
 718	blk_finish_plug(&plug);
 719	spin_lock(lock);
 720
 721	while (!list_empty(&tmp)) {
 722		bh = BH_ENTRY(tmp.prev);
 723		get_bh(bh);
 724		mapping = bh->b_assoc_map;
 725		__remove_assoc_queue(bh);
 726		/* Avoid race with mark_buffer_dirty_inode() which does
 727		 * a lockless check and we rely on seeing the dirty bit */
 728		smp_mb();
 729		if (buffer_dirty(bh)) {
 730			list_add(&bh->b_assoc_buffers,
 731				 &mapping->private_list);
 732			bh->b_assoc_map = mapping;
 733		}
 734		spin_unlock(lock);
 735		wait_on_buffer(bh);
 736		if (!buffer_uptodate(bh))
 737			err = -EIO;
 738		brelse(bh);
 739		spin_lock(lock);
 740	}
 741	
 742	spin_unlock(lock);
 743	err2 = osync_buffers_list(lock, list);
 744	if (err)
 745		return err;
 746	else
 747		return err2;
 748}
 749
 750/*
 751 * Invalidate any and all dirty buffers on a given inode.  We are
 752 * probably unmounting the fs, but that doesn't mean we have already
 753 * done a sync().  Just drop the buffers from the inode list.
 754 *
 755 * NOTE: we take the inode's blockdev's mapping's private_lock.  Which
 756 * assumes that all the buffers are against the blockdev.  Not true
 757 * for reiserfs.
 758 */
 759void invalidate_inode_buffers(struct inode *inode)
 760{
 761	if (inode_has_buffers(inode)) {
 762		struct address_space *mapping = &inode->i_data;
 763		struct list_head *list = &mapping->private_list;
 764		struct address_space *buffer_mapping = mapping->private_data;
 765
 766		spin_lock(&buffer_mapping->private_lock);
 767		while (!list_empty(list))
 768			__remove_assoc_queue(BH_ENTRY(list->next));
 769		spin_unlock(&buffer_mapping->private_lock);
 770	}
 771}
 772EXPORT_SYMBOL(invalidate_inode_buffers);
 773
 774/*
 775 * Remove any clean buffers from the inode's buffer list.  This is called
 776 * when we're trying to free the inode itself.  Those buffers can pin it.
 777 *
 778 * Returns true if all buffers were removed.
 779 */
 780int remove_inode_buffers(struct inode *inode)
 781{
 782	int ret = 1;
 783
 784	if (inode_has_buffers(inode)) {
 785		struct address_space *mapping = &inode->i_data;
 786		struct list_head *list = &mapping->private_list;
 787		struct address_space *buffer_mapping = mapping->private_data;
 788
 789		spin_lock(&buffer_mapping->private_lock);
 790		while (!list_empty(list)) {
 791			struct buffer_head *bh = BH_ENTRY(list->next);
 792			if (buffer_dirty(bh)) {
 793				ret = 0;
 794				break;
 795			}
 796			__remove_assoc_queue(bh);
 797		}
 798		spin_unlock(&buffer_mapping->private_lock);
 799	}
 800	return ret;
 801}
 802
 803/*
 804 * Create the appropriate buffers when given a page for data area and
 805 * the size of each buffer.. Use the bh->b_this_page linked list to
 806 * follow the buffers created.  Return NULL if unable to create more
 807 * buffers.
 808 *
 809 * The retry flag is used to differentiate async IO (paging, swapping)
 810 * which may not fail from ordinary buffer allocations.
 811 */
 812struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
 813		bool retry)
 814{
 815	struct buffer_head *bh, *head;
 816	gfp_t gfp = GFP_NOFS;
 817	long offset;
 
 818
 819	if (retry)
 820		gfp |= __GFP_NOFAIL;
 
 821
 822	head = NULL;
 823	offset = PAGE_SIZE;
 824	while ((offset -= size) >= 0) {
 825		bh = alloc_buffer_head(gfp);
 826		if (!bh)
 827			goto no_grow;
 828
 829		bh->b_this_page = head;
 830		bh->b_blocknr = -1;
 831		head = bh;
 832
 833		bh->b_size = size;
 834
 835		/* Link the buffer to its page */
 836		set_bh_page(bh, page, offset);
 837	}
 
 
 838	return head;
 839/*
 840 * In case anything failed, we just free everything we got.
 841 */
 842no_grow:
 843	if (head) {
 844		do {
 845			bh = head;
 846			head = head->b_this_page;
 847			free_buffer_head(bh);
 848		} while (head);
 849	}
 850
 851	return NULL;
 
 
 
 
 
 
 
 
 852}
 853EXPORT_SYMBOL_GPL(alloc_page_buffers);
 854
 855static inline void
 856link_dev_buffers(struct page *page, struct buffer_head *head)
 857{
 858	struct buffer_head *bh, *tail;
 859
 860	bh = head;
 861	do {
 862		tail = bh;
 863		bh = bh->b_this_page;
 864	} while (bh);
 865	tail->b_this_page = head;
 866	attach_page_buffers(page, head);
 867}
 868
 869static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
 870{
 871	sector_t retval = ~((sector_t)0);
 872	loff_t sz = i_size_read(bdev->bd_inode);
 873
 874	if (sz) {
 875		unsigned int sizebits = blksize_bits(size);
 876		retval = (sz >> sizebits);
 877	}
 878	return retval;
 879}
 880
 881/*
 882 * Initialise the state of a blockdev page's buffers.
 883 */ 
 884static sector_t
 885init_page_buffers(struct page *page, struct block_device *bdev,
 886			sector_t block, int size)
 887{
 888	struct buffer_head *head = page_buffers(page);
 889	struct buffer_head *bh = head;
 890	int uptodate = PageUptodate(page);
 891	sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode), size);
 
 892
 893	do {
 894		if (!buffer_mapped(bh)) {
 895			bh->b_end_io = NULL;
 896			bh->b_private = NULL;
 897			bh->b_bdev = bdev;
 898			bh->b_blocknr = block;
 899			if (uptodate)
 900				set_buffer_uptodate(bh);
 901			if (block < end_block)
 902				set_buffer_mapped(bh);
 903		}
 904		block++;
 905		bh = bh->b_this_page;
 906	} while (bh != head);
 907
 908	/*
 909	 * Caller needs to validate requested block against end of device.
 910	 */
 911	return end_block;
 912}
 913
 914/*
 915 * Create the page-cache page that contains the requested block.
 916 *
 917 * This is used purely for blockdev mappings.
 
 
 
 918 */
 919static int
 920grow_dev_page(struct block_device *bdev, sector_t block,
 921	      pgoff_t index, int size, int sizebits, gfp_t gfp)
 922{
 923	struct inode *inode = bdev->bd_inode;
 924	struct page *page;
 925	struct buffer_head *bh;
 926	sector_t end_block;
 927	int ret = 0;		/* Will call free_more_memory() */
 928	gfp_t gfp_mask;
 929
 930	gfp_mask = mapping_gfp_constraint(inode->i_mapping, ~__GFP_FS) | gfp;
 
 
 
 931
 932	/*
 933	 * XXX: __getblk_slow() can not really deal with failure and
 934	 * will endlessly loop on improvised global reclaim.  Prefer
 935	 * looping in the allocator rather than here, at least that
 936	 * code knows what it's doing.
 937	 */
 938	gfp_mask |= __GFP_NOFAIL;
 939
 940	page = find_or_create_page(inode->i_mapping, index, gfp_mask);
 941
 942	BUG_ON(!PageLocked(page));
 943
 944	if (page_has_buffers(page)) {
 945		bh = page_buffers(page);
 946		if (bh->b_size == size) {
 947			end_block = init_page_buffers(page, bdev,
 948						(sector_t)index << sizebits,
 949						size);
 950			goto done;
 951		}
 952		if (!try_to_free_buffers(page))
 953			goto failed;
 954	}
 955
 956	/*
 957	 * Allocate some buffers for this page
 958	 */
 959	bh = alloc_page_buffers(page, size, true);
 960
 961	/*
 962	 * Link the page to the buffers and initialise them.  Take the
 963	 * lock to be atomic wrt __find_get_block(), which does not
 964	 * run under the page lock.
 965	 */
 966	spin_lock(&inode->i_mapping->private_lock);
 967	link_dev_buffers(page, bh);
 968	end_block = init_page_buffers(page, bdev, (sector_t)index << sizebits,
 969			size);
 970	spin_unlock(&inode->i_mapping->private_lock);
 971done:
 972	ret = (block < end_block) ? 1 : -ENXIO;
 973failed:
 974	unlock_page(page);
 975	put_page(page);
 976	return ret;
 977}
 978
 979/*
 980 * Create buffers for the specified block device block's page.  If
 981 * that page was dirty, the buffers are set dirty also.
 
 982 */
 983static int
 984grow_buffers(struct block_device *bdev, sector_t block, int size, gfp_t gfp)
 985{
 986	pgoff_t index;
 987	int sizebits;
 988
 989	sizebits = -1;
 990	do {
 991		sizebits++;
 992	} while ((size << sizebits) < PAGE_SIZE);
 993
 994	index = block >> sizebits;
 995
 996	/*
 997	 * Check for a block which wants to lie outside our maximum possible
 998	 * pagecache index.  (this comparison is done using sector_t types).
 999	 */
1000	if (unlikely(index != block >> sizebits)) {
1001		printk(KERN_ERR "%s: requested out-of-range block %llu for "
1002			"device %pg\n",
1003			__func__, (unsigned long long)block,
1004			bdev);
1005		return -EIO;
1006	}
1007
1008	/* Create a page with the proper size buffers.. */
1009	return grow_dev_page(bdev, block, index, size, sizebits, gfp);
1010}
1011
1012static struct buffer_head *
1013__getblk_slow(struct block_device *bdev, sector_t block,
1014	     unsigned size, gfp_t gfp)
1015{
1016	/* Size must be multiple of hard sectorsize */
1017	if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
1018			(size < 512 || size > PAGE_SIZE))) {
1019		printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1020					size);
1021		printk(KERN_ERR "logical block size: %d\n",
1022					bdev_logical_block_size(bdev));
1023
1024		dump_stack();
1025		return NULL;
1026	}
1027
1028	for (;;) {
1029		struct buffer_head *bh;
1030		int ret;
1031
1032		bh = __find_get_block(bdev, block, size);
1033		if (bh)
1034			return bh;
1035
1036		ret = grow_buffers(bdev, block, size, gfp);
1037		if (ret < 0)
1038			return NULL;
1039	}
1040}
1041
1042/*
1043 * The relationship between dirty buffers and dirty pages:
1044 *
1045 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1046 * the page is tagged dirty in its radix tree.
1047 *
1048 * At all times, the dirtiness of the buffers represents the dirtiness of
1049 * subsections of the page.  If the page has buffers, the page dirty bit is
1050 * merely a hint about the true dirty state.
1051 *
1052 * When a page is set dirty in its entirety, all its buffers are marked dirty
1053 * (if the page has buffers).
1054 *
1055 * When a buffer is marked dirty, its page is dirtied, but the page's other
1056 * buffers are not.
1057 *
1058 * Also.  When blockdev buffers are explicitly read with bread(), they
1059 * individually become uptodate.  But their backing page remains not
1060 * uptodate - even if all of its buffers are uptodate.  A subsequent
1061 * block_read_full_page() against that page will discover all the uptodate
1062 * buffers, will set the page uptodate and will perform no I/O.
1063 */
1064
1065/**
1066 * mark_buffer_dirty - mark a buffer_head as needing writeout
1067 * @bh: the buffer_head to mark dirty
1068 *
1069 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1070 * backing page dirty, then tag the page as dirty in its address_space's radix
1071 * tree and then attach the address_space's inode to its superblock's dirty
1072 * inode list.
1073 *
1074 * mark_buffer_dirty() is atomic.  It takes bh->b_page->mapping->private_lock,
1075 * i_pages lock and mapping->host->i_lock.
1076 */
1077void mark_buffer_dirty(struct buffer_head *bh)
1078{
1079	WARN_ON_ONCE(!buffer_uptodate(bh));
1080
1081	trace_block_dirty_buffer(bh);
1082
1083	/*
1084	 * Very *carefully* optimize the it-is-already-dirty case.
1085	 *
1086	 * Don't let the final "is it dirty" escape to before we
1087	 * perhaps modified the buffer.
1088	 */
1089	if (buffer_dirty(bh)) {
1090		smp_mb();
1091		if (buffer_dirty(bh))
1092			return;
1093	}
1094
1095	if (!test_set_buffer_dirty(bh)) {
1096		struct page *page = bh->b_page;
1097		struct address_space *mapping = NULL;
1098
1099		lock_page_memcg(page);
1100		if (!TestSetPageDirty(page)) {
1101			mapping = page_mapping(page);
1102			if (mapping)
1103				__set_page_dirty(page, mapping, 0);
1104		}
1105		unlock_page_memcg(page);
1106		if (mapping)
1107			__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
1108	}
1109}
1110EXPORT_SYMBOL(mark_buffer_dirty);
1111
1112void mark_buffer_write_io_error(struct buffer_head *bh)
1113{
1114	set_buffer_write_io_error(bh);
1115	/* FIXME: do we need to set this in both places? */
1116	if (bh->b_page && bh->b_page->mapping)
1117		mapping_set_error(bh->b_page->mapping, -EIO);
1118	if (bh->b_assoc_map)
1119		mapping_set_error(bh->b_assoc_map, -EIO);
 
 
1120}
1121EXPORT_SYMBOL(mark_buffer_write_io_error);
1122
1123/*
1124 * Decrement a buffer_head's reference count.  If all buffers against a page
1125 * have zero reference count, are clean and unlocked, and if the page is clean
1126 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1127 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1128 * a page but it ends up not being freed, and buffers may later be reattached).
1129 */
1130void __brelse(struct buffer_head * buf)
1131{
1132	if (atomic_read(&buf->b_count)) {
1133		put_bh(buf);
1134		return;
1135	}
1136	WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1137}
1138EXPORT_SYMBOL(__brelse);
1139
1140/*
1141 * bforget() is like brelse(), except it discards any
1142 * potentially dirty data.
 
 
 
1143 */
1144void __bforget(struct buffer_head *bh)
1145{
1146	clear_buffer_dirty(bh);
1147	if (bh->b_assoc_map) {
1148		struct address_space *buffer_mapping = bh->b_page->mapping;
1149
1150		spin_lock(&buffer_mapping->private_lock);
1151		list_del_init(&bh->b_assoc_buffers);
1152		bh->b_assoc_map = NULL;
1153		spin_unlock(&buffer_mapping->private_lock);
1154	}
1155	__brelse(bh);
1156}
1157EXPORT_SYMBOL(__bforget);
1158
1159static struct buffer_head *__bread_slow(struct buffer_head *bh)
1160{
1161	lock_buffer(bh);
1162	if (buffer_uptodate(bh)) {
1163		unlock_buffer(bh);
1164		return bh;
1165	} else {
1166		get_bh(bh);
1167		bh->b_end_io = end_buffer_read_sync;
1168		submit_bh(REQ_OP_READ, 0, bh);
1169		wait_on_buffer(bh);
1170		if (buffer_uptodate(bh))
1171			return bh;
1172	}
1173	brelse(bh);
1174	return NULL;
1175}
1176
1177/*
1178 * Per-cpu buffer LRU implementation.  To reduce the cost of __find_get_block().
1179 * The bhs[] array is sorted - newest buffer is at bhs[0].  Buffers have their
1180 * refcount elevated by one when they're in an LRU.  A buffer can only appear
1181 * once in a particular CPU's LRU.  A single buffer can be present in multiple
1182 * CPU's LRUs at the same time.
1183 *
1184 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1185 * sb_find_get_block().
1186 *
1187 * The LRUs themselves only need locking against invalidate_bh_lrus.  We use
1188 * a local interrupt disable for that.
1189 */
1190
1191#define BH_LRU_SIZE	16
1192
1193struct bh_lru {
1194	struct buffer_head *bhs[BH_LRU_SIZE];
1195};
1196
1197static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1198
1199#ifdef CONFIG_SMP
1200#define bh_lru_lock()	local_irq_disable()
1201#define bh_lru_unlock()	local_irq_enable()
1202#else
1203#define bh_lru_lock()	preempt_disable()
1204#define bh_lru_unlock()	preempt_enable()
1205#endif
1206
1207static inline void check_irqs_on(void)
1208{
1209#ifdef irqs_disabled
1210	BUG_ON(irqs_disabled());
1211#endif
1212}
1213
1214/*
1215 * Install a buffer_head into this cpu's LRU.  If not already in the LRU, it is
1216 * inserted at the front, and the buffer_head at the back if any is evicted.
1217 * Or, if already in the LRU it is moved to the front.
1218 */
1219static void bh_lru_install(struct buffer_head *bh)
1220{
1221	struct buffer_head *evictee = bh;
1222	struct bh_lru *b;
1223	int i;
1224
1225	check_irqs_on();
1226	bh_lru_lock();
1227
 
 
 
 
 
 
 
 
 
 
 
1228	b = this_cpu_ptr(&bh_lrus);
1229	for (i = 0; i < BH_LRU_SIZE; i++) {
1230		swap(evictee, b->bhs[i]);
1231		if (evictee == bh) {
1232			bh_lru_unlock();
1233			return;
1234		}
1235	}
1236
1237	get_bh(bh);
1238	bh_lru_unlock();
1239	brelse(evictee);
1240}
1241
1242/*
1243 * Look up the bh in this cpu's LRU.  If it's there, move it to the head.
1244 */
1245static struct buffer_head *
1246lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
1247{
1248	struct buffer_head *ret = NULL;
1249	unsigned int i;
1250
1251	check_irqs_on();
1252	bh_lru_lock();
 
 
 
 
1253	for (i = 0; i < BH_LRU_SIZE; i++) {
1254		struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
1255
1256		if (bh && bh->b_blocknr == block && bh->b_bdev == bdev &&
1257		    bh->b_size == size) {
1258			if (i) {
1259				while (i) {
1260					__this_cpu_write(bh_lrus.bhs[i],
1261						__this_cpu_read(bh_lrus.bhs[i - 1]));
1262					i--;
1263				}
1264				__this_cpu_write(bh_lrus.bhs[0], bh);
1265			}
1266			get_bh(bh);
1267			ret = bh;
1268			break;
1269		}
1270	}
1271	bh_lru_unlock();
1272	return ret;
1273}
1274
1275/*
1276 * Perform a pagecache lookup for the matching buffer.  If it's there, refresh
1277 * it in the LRU and mark it as accessed.  If it is not present then return
1278 * NULL
1279 */
1280struct buffer_head *
1281__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
1282{
1283	struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1284
1285	if (bh == NULL) {
1286		/* __find_get_block_slow will mark the page accessed */
1287		bh = __find_get_block_slow(bdev, block);
1288		if (bh)
1289			bh_lru_install(bh);
1290	} else
1291		touch_buffer(bh);
1292
1293	return bh;
1294}
1295EXPORT_SYMBOL(__find_get_block);
1296
1297/*
1298 * __getblk_gfp() will locate (and, if necessary, create) the buffer_head
1299 * which corresponds to the passed block_device, block and size. The
1300 * returned buffer has its reference count incremented.
 
 
 
 
 
 
 
1301 *
1302 * __getblk_gfp() will lock up the machine if grow_dev_page's
1303 * try_to_free_buffers() attempt is failing.  FIXME, perhaps?
1304 */
1305struct buffer_head *
1306__getblk_gfp(struct block_device *bdev, sector_t block,
1307	     unsigned size, gfp_t gfp)
1308{
1309	struct buffer_head *bh = __find_get_block(bdev, block, size);
1310
1311	might_sleep();
1312	if (bh == NULL)
1313		bh = __getblk_slow(bdev, block, size, gfp);
1314	return bh;
 
1315}
1316EXPORT_SYMBOL(__getblk_gfp);
1317
1318/*
1319 * Do async read-ahead on a buffer..
1320 */
1321void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
1322{
1323	struct buffer_head *bh = __getblk(bdev, block, size);
 
 
1324	if (likely(bh)) {
1325		ll_rw_block(REQ_OP_READ, REQ_RAHEAD, 1, &bh);
1326		brelse(bh);
1327	}
1328}
1329EXPORT_SYMBOL(__breadahead);
1330
1331/**
1332 *  __bread_gfp() - reads a specified block and returns the bh
1333 *  @bdev: the block_device to read from
1334 *  @block: number of block
1335 *  @size: size (in bytes) to read
1336 *  @gfp: page allocation flag
1337 *
1338 *  Reads a specified block, and returns buffer head that contains it.
1339 *  The page cache can be allocated from non-movable area
1340 *  not to prevent page migration if you set gfp to zero.
1341 *  It returns NULL if the block was unreadable.
 
 
 
 
 
 
 
 
 
 
1342 */
1343struct buffer_head *
1344__bread_gfp(struct block_device *bdev, sector_t block,
1345		   unsigned size, gfp_t gfp)
1346{
1347	struct buffer_head *bh = __getblk_gfp(bdev, block, size, gfp);
 
 
 
 
 
 
 
 
 
 
1348
1349	if (likely(bh) && !buffer_uptodate(bh))
1350		bh = __bread_slow(bh);
1351	return bh;
1352}
1353EXPORT_SYMBOL(__bread_gfp);
1354
 
 
 
 
 
 
 
 
 
1355/*
1356 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1357 * This doesn't race because it runs in each cpu either in irq
1358 * or with preempt disabled.
1359 */
1360static void invalidate_bh_lru(void *arg)
1361{
1362	struct bh_lru *b = &get_cpu_var(bh_lrus);
1363	int i;
1364
1365	for (i = 0; i < BH_LRU_SIZE; i++) {
1366		brelse(b->bhs[i]);
1367		b->bhs[i] = NULL;
1368	}
1369	put_cpu_var(bh_lrus);
1370}
1371
1372static bool has_bh_in_lru(int cpu, void *dummy)
1373{
1374	struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
1375	int i;
1376	
1377	for (i = 0; i < BH_LRU_SIZE; i++) {
1378		if (b->bhs[i])
1379			return 1;
1380	}
1381
1382	return 0;
1383}
1384
1385void invalidate_bh_lrus(void)
1386{
1387	on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL);
1388}
1389EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
1390
1391void set_bh_page(struct buffer_head *bh,
1392		struct page *page, unsigned long offset)
 
 
 
1393{
1394	bh->b_page = page;
1395	BUG_ON(offset >= PAGE_SIZE);
1396	if (PageHighMem(page))
 
 
 
 
 
 
 
 
 
 
 
1397		/*
1398		 * This catches illegal uses and preserves the offset:
1399		 */
1400		bh->b_data = (char *)(0 + offset);
1401	else
1402		bh->b_data = page_address(page) + offset;
1403}
1404EXPORT_SYMBOL(set_bh_page);
1405
1406/*
1407 * Called when truncating a buffer on a page completely.
1408 */
1409
1410/* Bits that are cleared during an invalidate */
1411#define BUFFER_FLAGS_DISCARD \
1412	(1 << BH_Mapped | 1 << BH_New | 1 << BH_Req | \
1413	 1 << BH_Delay | 1 << BH_Unwritten)
1414
1415static void discard_buffer(struct buffer_head * bh)
1416{
1417	unsigned long b_state, b_state_old;
1418
1419	lock_buffer(bh);
1420	clear_buffer_dirty(bh);
1421	bh->b_bdev = NULL;
1422	b_state = bh->b_state;
1423	for (;;) {
1424		b_state_old = cmpxchg(&bh->b_state, b_state,
1425				      (b_state & ~BUFFER_FLAGS_DISCARD));
1426		if (b_state_old == b_state)
1427			break;
1428		b_state = b_state_old;
1429	}
1430	unlock_buffer(bh);
1431}
1432
1433/**
1434 * block_invalidatepage - invalidate part or all of a buffer-backed page
1435 *
1436 * @page: the page which is affected
1437 * @offset: start of the range to invalidate
1438 * @length: length of the range to invalidate
1439 *
1440 * block_invalidatepage() is called when all or part of the page has become
1441 * invalidated by a truncate operation.
1442 *
1443 * block_invalidatepage() does not have to release all buffers, but it must
1444 * ensure that no dirty buffer is left outside @offset and that no I/O
1445 * is underway against any of the blocks which are outside the truncation
1446 * point.  Because the caller is about to free (and possibly reuse) those
1447 * blocks on-disk.
1448 */
1449void block_invalidatepage(struct page *page, unsigned int offset,
1450			  unsigned int length)
1451{
1452	struct buffer_head *head, *bh, *next;
1453	unsigned int curr_off = 0;
1454	unsigned int stop = length + offset;
1455
1456	BUG_ON(!PageLocked(page));
1457	if (!page_has_buffers(page))
1458		goto out;
1459
1460	/*
1461	 * Check for overflow
1462	 */
1463	BUG_ON(stop > PAGE_SIZE || stop < length);
 
 
 
 
1464
1465	head = page_buffers(page);
1466	bh = head;
1467	do {
1468		unsigned int next_off = curr_off + bh->b_size;
1469		next = bh->b_this_page;
1470
1471		/*
1472		 * Are we still fully in range ?
1473		 */
1474		if (next_off > stop)
1475			goto out;
1476
1477		/*
1478		 * is this block fully invalidated?
1479		 */
1480		if (offset <= curr_off)
1481			discard_buffer(bh);
1482		curr_off = next_off;
1483		bh = next;
1484	} while (bh != head);
1485
1486	/*
1487	 * We release buffers only if the entire page is being invalidated.
1488	 * The get_block cached value has been unconditionally invalidated,
1489	 * so real IO is not possible anymore.
1490	 */
1491	if (length == PAGE_SIZE)
1492		try_to_release_page(page, 0);
1493out:
 
1494	return;
1495}
1496EXPORT_SYMBOL(block_invalidatepage);
1497
1498
1499/*
1500 * We attach and possibly dirty the buffers atomically wrt
1501 * __set_page_dirty_buffers() via private_lock.  try_to_free_buffers
1502 * is already excluded via the page lock.
1503 */
1504void create_empty_buffers(struct page *page,
1505			unsigned long blocksize, unsigned long b_state)
1506{
1507	struct buffer_head *bh, *head, *tail;
 
1508
1509	head = alloc_page_buffers(page, blocksize, true);
1510	bh = head;
1511	do {
1512		bh->b_state |= b_state;
1513		tail = bh;
1514		bh = bh->b_this_page;
1515	} while (bh);
1516	tail->b_this_page = head;
1517
1518	spin_lock(&page->mapping->private_lock);
1519	if (PageUptodate(page) || PageDirty(page)) {
1520		bh = head;
1521		do {
1522			if (PageDirty(page))
1523				set_buffer_dirty(bh);
1524			if (PageUptodate(page))
1525				set_buffer_uptodate(bh);
1526			bh = bh->b_this_page;
1527		} while (bh != head);
1528	}
1529	attach_page_buffers(page, head);
1530	spin_unlock(&page->mapping->private_lock);
 
 
1531}
1532EXPORT_SYMBOL(create_empty_buffers);
1533
1534/**
1535 * clean_bdev_aliases: clean a range of buffers in block device
1536 * @bdev: Block device to clean buffers in
1537 * @block: Start of a range of blocks to clean
1538 * @len: Number of blocks to clean
1539 *
1540 * We are taking a range of blocks for data and we don't want writeback of any
1541 * buffer-cache aliases starting from return from this function and until the
1542 * moment when something will explicitly mark the buffer dirty (hopefully that
1543 * will not happen until we will free that block ;-) We don't even need to mark
1544 * it not-uptodate - nobody can expect anything from a newly allocated buffer
1545 * anyway. We used to use unmap_buffer() for such invalidation, but that was
1546 * wrong. We definitely don't want to mark the alias unmapped, for example - it
1547 * would confuse anyone who might pick it with bread() afterwards...
1548 *
1549 * Also..  Note that bforget() doesn't lock the buffer.  So there can be
1550 * writeout I/O going on against recently-freed buffers.  We don't wait on that
1551 * I/O in bforget() - it's more efficient to wait on the I/O only if we really
1552 * need to.  That happens here.
1553 */
1554void clean_bdev_aliases(struct block_device *bdev, sector_t block, sector_t len)
1555{
1556	struct inode *bd_inode = bdev->bd_inode;
1557	struct address_space *bd_mapping = bd_inode->i_mapping;
1558	struct pagevec pvec;
1559	pgoff_t index = block >> (PAGE_SHIFT - bd_inode->i_blkbits);
1560	pgoff_t end;
1561	int i, count;
1562	struct buffer_head *bh;
1563	struct buffer_head *head;
1564
1565	end = (block + len - 1) >> (PAGE_SHIFT - bd_inode->i_blkbits);
1566	pagevec_init(&pvec);
1567	while (pagevec_lookup_range(&pvec, bd_mapping, &index, end)) {
1568		count = pagevec_count(&pvec);
1569		for (i = 0; i < count; i++) {
1570			struct page *page = pvec.pages[i];
1571
1572			if (!page_has_buffers(page))
1573				continue;
1574			/*
1575			 * We use page lock instead of bd_mapping->private_lock
1576			 * to pin buffers here since we can afford to sleep and
1577			 * it scales better than a global spinlock lock.
1578			 */
1579			lock_page(page);
1580			/* Recheck when the page is locked which pins bhs */
1581			if (!page_has_buffers(page))
 
1582				goto unlock_page;
1583			head = page_buffers(page);
1584			bh = head;
1585			do {
1586				if (!buffer_mapped(bh) || (bh->b_blocknr < block))
1587					goto next;
1588				if (bh->b_blocknr >= block + len)
1589					break;
1590				clear_buffer_dirty(bh);
1591				wait_on_buffer(bh);
1592				clear_buffer_req(bh);
1593next:
1594				bh = bh->b_this_page;
1595			} while (bh != head);
1596unlock_page:
1597			unlock_page(page);
1598		}
1599		pagevec_release(&pvec);
1600		cond_resched();
1601		/* End of range already reached? */
1602		if (index > end || !index)
1603			break;
1604	}
1605}
1606EXPORT_SYMBOL(clean_bdev_aliases);
1607
1608/*
1609 * Size is a power-of-two in the range 512..PAGE_SIZE,
1610 * and the case we care about most is PAGE_SIZE.
1611 *
1612 * So this *could* possibly be written with those
1613 * constraints in mind (relevant mostly if some
1614 * architecture has a slow bit-scan instruction)
1615 */
1616static inline int block_size_bits(unsigned int blocksize)
1617{
1618	return ilog2(blocksize);
1619}
1620
1621static struct buffer_head *create_page_buffers(struct page *page, struct inode *inode, unsigned int b_state)
1622{
1623	BUG_ON(!PageLocked(page));
1624
1625	if (!page_has_buffers(page))
1626		create_empty_buffers(page, 1 << READ_ONCE(inode->i_blkbits),
1627				     b_state);
1628	return page_buffers(page);
 
1629}
1630
1631/*
1632 * NOTE! All mapped/uptodate combinations are valid:
1633 *
1634 *	Mapped	Uptodate	Meaning
1635 *
1636 *	No	No		"unknown" - must do get_block()
1637 *	No	Yes		"hole" - zero-filled
1638 *	Yes	No		"allocated" - allocated on disk, not read in
1639 *	Yes	Yes		"valid" - allocated and up-to-date in memory.
1640 *
1641 * "Dirty" is valid only with the last case (mapped+uptodate).
1642 */
1643
1644/*
1645 * While block_write_full_page is writing back the dirty buffers under
1646 * the page lock, whoever dirtied the buffers may decide to clean them
1647 * again at any time.  We handle that by only looking at the buffer
1648 * state inside lock_buffer().
1649 *
1650 * If block_write_full_page() is called for regular writeback
1651 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1652 * locked buffer.   This only can happen if someone has written the buffer
1653 * directly, with submit_bh().  At the address_space level PageWriteback
1654 * prevents this contention from occurring.
1655 *
1656 * If block_write_full_page() is called with wbc->sync_mode ==
1657 * WB_SYNC_ALL, the writes are posted using REQ_SYNC; this
1658 * causes the writes to be flagged as synchronous writes.
1659 */
1660int __block_write_full_page(struct inode *inode, struct page *page,
1661			get_block_t *get_block, struct writeback_control *wbc,
1662			bh_end_io_t *handler)
1663{
1664	int err;
1665	sector_t block;
1666	sector_t last_block;
1667	struct buffer_head *bh, *head;
1668	unsigned int blocksize, bbits;
1669	int nr_underway = 0;
1670	int write_flags = wbc_to_write_flags(wbc);
1671
1672	head = create_page_buffers(page, inode,
1673					(1 << BH_Dirty)|(1 << BH_Uptodate));
1674
1675	/*
1676	 * Be very careful.  We have no exclusion from __set_page_dirty_buffers
1677	 * here, and the (potentially unmapped) buffers may become dirty at
1678	 * any time.  If a buffer becomes dirty here after we've inspected it
1679	 * then we just miss that fact, and the page stays dirty.
1680	 *
1681	 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1682	 * handle that here by just cleaning them.
1683	 */
1684
1685	bh = head;
1686	blocksize = bh->b_size;
1687	bbits = block_size_bits(blocksize);
1688
1689	block = (sector_t)page->index << (PAGE_SHIFT - bbits);
1690	last_block = (i_size_read(inode) - 1) >> bbits;
1691
1692	/*
1693	 * Get all the dirty buffers mapped to disk addresses and
1694	 * handle any aliases from the underlying blockdev's mapping.
1695	 */
1696	do {
1697		if (block > last_block) {
1698			/*
1699			 * mapped buffers outside i_size will occur, because
1700			 * this page can be outside i_size when there is a
1701			 * truncate in progress.
1702			 */
1703			/*
1704			 * The buffer was zeroed by block_write_full_page()
1705			 */
1706			clear_buffer_dirty(bh);
1707			set_buffer_uptodate(bh);
1708		} else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1709			   buffer_dirty(bh)) {
1710			WARN_ON(bh->b_size != blocksize);
1711			err = get_block(inode, block, bh, 1);
1712			if (err)
1713				goto recover;
1714			clear_buffer_delay(bh);
1715			if (buffer_new(bh)) {
1716				/* blockdev mappings never come here */
1717				clear_buffer_new(bh);
1718				clean_bdev_bh_alias(bh);
1719			}
1720		}
1721		bh = bh->b_this_page;
1722		block++;
1723	} while (bh != head);
1724
1725	do {
1726		if (!buffer_mapped(bh))
1727			continue;
1728		/*
1729		 * If it's a fully non-blocking write attempt and we cannot
1730		 * lock the buffer then redirty the page.  Note that this can
1731		 * potentially cause a busy-wait loop from writeback threads
1732		 * and kswapd activity, but those code paths have their own
1733		 * higher-level throttling.
1734		 */
1735		if (wbc->sync_mode != WB_SYNC_NONE) {
1736			lock_buffer(bh);
1737		} else if (!trylock_buffer(bh)) {
1738			redirty_page_for_writepage(wbc, page);
1739			continue;
1740		}
1741		if (test_clear_buffer_dirty(bh)) {
1742			mark_buffer_async_write_endio(bh, handler);
 
1743		} else {
1744			unlock_buffer(bh);
1745		}
1746	} while ((bh = bh->b_this_page) != head);
1747
1748	/*
1749	 * The page and its buffers are protected by PageWriteback(), so we can
1750	 * drop the bh refcounts early.
1751	 */
1752	BUG_ON(PageWriteback(page));
1753	set_page_writeback(page);
1754
1755	do {
1756		struct buffer_head *next = bh->b_this_page;
1757		if (buffer_async_write(bh)) {
1758			submit_bh_wbc(REQ_OP_WRITE, write_flags, bh,
1759					inode->i_write_hint, wbc);
1760			nr_underway++;
1761		}
1762		bh = next;
1763	} while (bh != head);
1764	unlock_page(page);
1765
1766	err = 0;
1767done:
1768	if (nr_underway == 0) {
1769		/*
1770		 * The page was marked dirty, but the buffers were
1771		 * clean.  Someone wrote them back by hand with
1772		 * ll_rw_block/submit_bh.  A rare case.
1773		 */
1774		end_page_writeback(page);
1775
1776		/*
1777		 * The page and buffer_heads can be released at any time from
1778		 * here on.
1779		 */
1780	}
1781	return err;
1782
1783recover:
1784	/*
1785	 * ENOSPC, or some other error.  We may already have added some
1786	 * blocks to the file, so we need to write these out to avoid
1787	 * exposing stale data.
1788	 * The page is currently locked and not marked for writeback
1789	 */
1790	bh = head;
1791	/* Recovery: lock and submit the mapped buffers */
1792	do {
1793		if (buffer_mapped(bh) && buffer_dirty(bh) &&
1794		    !buffer_delay(bh)) {
1795			lock_buffer(bh);
1796			mark_buffer_async_write_endio(bh, handler);
 
1797		} else {
1798			/*
1799			 * The buffer may have been set dirty during
1800			 * attachment to a dirty page.
1801			 */
1802			clear_buffer_dirty(bh);
1803		}
1804	} while ((bh = bh->b_this_page) != head);
1805	SetPageError(page);
1806	BUG_ON(PageWriteback(page));
1807	mapping_set_error(page->mapping, err);
1808	set_page_writeback(page);
1809	do {
1810		struct buffer_head *next = bh->b_this_page;
1811		if (buffer_async_write(bh)) {
1812			clear_buffer_dirty(bh);
1813			submit_bh_wbc(REQ_OP_WRITE, write_flags, bh,
1814					inode->i_write_hint, wbc);
1815			nr_underway++;
1816		}
1817		bh = next;
1818	} while (bh != head);
1819	unlock_page(page);
1820	goto done;
1821}
1822EXPORT_SYMBOL(__block_write_full_page);
1823
1824/*
1825 * If a page has any new buffers, zero them out here, and mark them uptodate
1826 * and dirty so they'll be written out (in order to prevent uninitialised
1827 * block data from leaking). And clear the new bit.
1828 */
1829void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1830{
1831	unsigned int block_start, block_end;
1832	struct buffer_head *head, *bh;
1833
1834	BUG_ON(!PageLocked(page));
1835	if (!page_has_buffers(page))
 
1836		return;
1837
1838	bh = head = page_buffers(page);
1839	block_start = 0;
1840	do {
1841		block_end = block_start + bh->b_size;
1842
1843		if (buffer_new(bh)) {
1844			if (block_end > from && block_start < to) {
1845				if (!PageUptodate(page)) {
1846					unsigned start, size;
1847
1848					start = max(from, block_start);
1849					size = min(to, block_end) - start;
1850
1851					zero_user(page, start, size);
1852					set_buffer_uptodate(bh);
1853				}
1854
1855				clear_buffer_new(bh);
1856				mark_buffer_dirty(bh);
1857			}
1858		}
1859
1860		block_start = block_end;
1861		bh = bh->b_this_page;
1862	} while (bh != head);
1863}
1864EXPORT_SYMBOL(page_zero_new_buffers);
1865
1866static void
1867iomap_to_bh(struct inode *inode, sector_t block, struct buffer_head *bh,
1868		struct iomap *iomap)
1869{
1870	loff_t offset = block << inode->i_blkbits;
1871
1872	bh->b_bdev = iomap->bdev;
1873
1874	/*
1875	 * Block points to offset in file we need to map, iomap contains
1876	 * the offset at which the map starts. If the map ends before the
1877	 * current block, then do not map the buffer and let the caller
1878	 * handle it.
1879	 */
1880	BUG_ON(offset >= iomap->offset + iomap->length);
 
1881
1882	switch (iomap->type) {
1883	case IOMAP_HOLE:
1884		/*
1885		 * If the buffer is not up to date or beyond the current EOF,
1886		 * we need to mark it as new to ensure sub-block zeroing is
1887		 * executed if necessary.
1888		 */
1889		if (!buffer_uptodate(bh) ||
1890		    (offset >= i_size_read(inode)))
1891			set_buffer_new(bh);
1892		break;
1893	case IOMAP_DELALLOC:
1894		if (!buffer_uptodate(bh) ||
1895		    (offset >= i_size_read(inode)))
1896			set_buffer_new(bh);
1897		set_buffer_uptodate(bh);
1898		set_buffer_mapped(bh);
1899		set_buffer_delay(bh);
1900		break;
1901	case IOMAP_UNWRITTEN:
1902		/*
1903		 * For unwritten regions, we always need to ensure that
1904		 * sub-block writes cause the regions in the block we are not
1905		 * writing to are zeroed. Set the buffer as new to ensure this.
1906		 */
1907		set_buffer_new(bh);
1908		set_buffer_unwritten(bh);
1909		/* FALLTHRU */
1910	case IOMAP_MAPPED:
1911		if (offset >= i_size_read(inode))
 
 
 
 
 
 
 
 
 
1912			set_buffer_new(bh);
 
1913		bh->b_blocknr = (iomap->addr + offset - iomap->offset) >>
1914				inode->i_blkbits;
1915		set_buffer_mapped(bh);
1916		break;
 
 
 
1917	}
1918}
1919
1920int __block_write_begin_int(struct page *page, loff_t pos, unsigned len,
1921		get_block_t *get_block, struct iomap *iomap)
1922{
1923	unsigned from = pos & (PAGE_SIZE - 1);
1924	unsigned to = from + len;
1925	struct inode *inode = page->mapping->host;
1926	unsigned block_start, block_end;
1927	sector_t block;
1928	int err = 0;
1929	unsigned blocksize, bbits;
1930	struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1931
1932	BUG_ON(!PageLocked(page));
1933	BUG_ON(from > PAGE_SIZE);
1934	BUG_ON(to > PAGE_SIZE);
1935	BUG_ON(from > to);
1936
1937	head = create_page_buffers(page, inode, 0);
1938	blocksize = head->b_size;
1939	bbits = block_size_bits(blocksize);
1940
1941	block = (sector_t)page->index << (PAGE_SHIFT - bbits);
1942
1943	for(bh = head, block_start = 0; bh != head || !block_start;
1944	    block++, block_start=block_end, bh = bh->b_this_page) {
1945		block_end = block_start + blocksize;
1946		if (block_end <= from || block_start >= to) {
1947			if (PageUptodate(page)) {
1948				if (!buffer_uptodate(bh))
1949					set_buffer_uptodate(bh);
1950			}
1951			continue;
1952		}
1953		if (buffer_new(bh))
1954			clear_buffer_new(bh);
1955		if (!buffer_mapped(bh)) {
1956			WARN_ON(bh->b_size != blocksize);
1957			if (get_block) {
1958				err = get_block(inode, block, bh, 1);
1959				if (err)
1960					break;
1961			} else {
1962				iomap_to_bh(inode, block, bh, iomap);
1963			}
1964
1965			if (buffer_new(bh)) {
1966				clean_bdev_bh_alias(bh);
1967				if (PageUptodate(page)) {
1968					clear_buffer_new(bh);
1969					set_buffer_uptodate(bh);
1970					mark_buffer_dirty(bh);
1971					continue;
1972				}
1973				if (block_end > to || block_start < from)
1974					zero_user_segments(page,
1975						to, block_end,
1976						block_start, from);
1977				continue;
1978			}
1979		}
1980		if (PageUptodate(page)) {
1981			if (!buffer_uptodate(bh))
1982				set_buffer_uptodate(bh);
1983			continue; 
1984		}
1985		if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
1986		    !buffer_unwritten(bh) &&
1987		     (block_start < from || block_end > to)) {
1988			ll_rw_block(REQ_OP_READ, 0, 1, &bh);
1989			*wait_bh++=bh;
1990		}
1991	}
1992	/*
1993	 * If we issued read requests - let them complete.
1994	 */
1995	while(wait_bh > wait) {
1996		wait_on_buffer(*--wait_bh);
1997		if (!buffer_uptodate(*wait_bh))
1998			err = -EIO;
1999	}
2000	if (unlikely(err))
2001		page_zero_new_buffers(page, from, to);
2002	return err;
2003}
2004
2005int __block_write_begin(struct page *page, loff_t pos, unsigned len,
2006		get_block_t *get_block)
2007{
2008	return __block_write_begin_int(page, pos, len, get_block, NULL);
2009}
2010EXPORT_SYMBOL(__block_write_begin);
2011
2012static int __block_commit_write(struct inode *inode, struct page *page,
2013		unsigned from, unsigned to)
2014{
2015	unsigned block_start, block_end;
2016	int partial = 0;
2017	unsigned blocksize;
2018	struct buffer_head *bh, *head;
2019
2020	bh = head = page_buffers(page);
 
 
2021	blocksize = bh->b_size;
2022
2023	block_start = 0;
2024	do {
2025		block_end = block_start + blocksize;
2026		if (block_end <= from || block_start >= to) {
2027			if (!buffer_uptodate(bh))
2028				partial = 1;
2029		} else {
2030			set_buffer_uptodate(bh);
2031			mark_buffer_dirty(bh);
2032		}
2033		clear_buffer_new(bh);
 
2034
2035		block_start = block_end;
2036		bh = bh->b_this_page;
2037	} while (bh != head);
2038
2039	/*
2040	 * If this is a partial write which happened to make all buffers
2041	 * uptodate then we can optimize away a bogus readpage() for
2042	 * the next read(). Here we 'discover' whether the page went
2043	 * uptodate as a result of this (potentially partial) write.
2044	 */
2045	if (!partial)
2046		SetPageUptodate(page);
2047	return 0;
2048}
2049
2050/*
2051 * block_write_begin takes care of the basic task of block allocation and
2052 * bringing partial write blocks uptodate first.
2053 *
2054 * The filesystem needs to handle block truncation upon failure.
2055 */
2056int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
2057		unsigned flags, struct page **pagep, get_block_t *get_block)
2058{
2059	pgoff_t index = pos >> PAGE_SHIFT;
2060	struct page *page;
2061	int status;
2062
2063	page = grab_cache_page_write_begin(mapping, index, flags);
2064	if (!page)
2065		return -ENOMEM;
 
2066
2067	status = __block_write_begin(page, pos, len, get_block);
2068	if (unlikely(status)) {
2069		unlock_page(page);
2070		put_page(page);
2071		page = NULL;
2072	}
2073
2074	*pagep = page;
2075	return status;
2076}
2077EXPORT_SYMBOL(block_write_begin);
2078
2079int block_write_end(struct file *file, struct address_space *mapping,
2080			loff_t pos, unsigned len, unsigned copied,
2081			struct page *page, void *fsdata)
2082{
2083	struct inode *inode = mapping->host;
2084	unsigned start;
2085
2086	start = pos & (PAGE_SIZE - 1);
2087
2088	if (unlikely(copied < len)) {
2089		/*
2090		 * The buffers that were written will now be uptodate, so we
2091		 * don't have to worry about a readpage reading them and
2092		 * overwriting a partial write. However if we have encountered
2093		 * a short write and only partially written into a buffer, it
2094		 * will not be marked uptodate, so a readpage might come in and
2095		 * destroy our partial write.
2096		 *
2097		 * Do the simplest thing, and just treat any short write to a
2098		 * non uptodate page as a zero-length write, and force the
2099		 * caller to redo the whole thing.
2100		 */
2101		if (!PageUptodate(page))
2102			copied = 0;
2103
2104		page_zero_new_buffers(page, start+copied, start+len);
2105	}
2106	flush_dcache_page(page);
2107
2108	/* This could be a short (even 0-length) commit */
2109	__block_commit_write(inode, page, start, start+copied);
2110
2111	return copied;
2112}
2113EXPORT_SYMBOL(block_write_end);
2114
2115int generic_write_end(struct file *file, struct address_space *mapping,
2116			loff_t pos, unsigned len, unsigned copied,
2117			struct page *page, void *fsdata)
2118{
2119	struct inode *inode = mapping->host;
2120	loff_t old_size = inode->i_size;
2121	int i_size_changed = 0;
2122
2123	copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2124
2125	/*
2126	 * No need to use i_size_read() here, the i_size
2127	 * cannot change under us because we hold i_mutex.
2128	 *
2129	 * But it's important to update i_size while still holding page lock:
2130	 * page writeout could otherwise come in and zero beyond i_size.
2131	 */
2132	if (pos+copied > inode->i_size) {
2133		i_size_write(inode, pos+copied);
2134		i_size_changed = 1;
2135	}
2136
2137	unlock_page(page);
2138	put_page(page);
2139
2140	if (old_size < pos)
2141		pagecache_isize_extended(inode, old_size, pos);
2142	/*
2143	 * Don't mark the inode dirty under page lock. First, it unnecessarily
2144	 * makes the holding time of page lock longer. Second, it forces lock
2145	 * ordering of page lock and transaction start for journaling
2146	 * filesystems.
2147	 */
2148	if (i_size_changed)
2149		mark_inode_dirty(inode);
2150
2151	return copied;
2152}
2153EXPORT_SYMBOL(generic_write_end);
2154
2155/*
2156 * block_is_partially_uptodate checks whether buffers within a page are
2157 * uptodate or not.
2158 *
2159 * Returns true if all buffers which correspond to a file portion
2160 * we want to read are uptodate.
2161 */
2162int block_is_partially_uptodate(struct page *page, unsigned long from,
2163					unsigned long count)
2164{
2165	unsigned block_start, block_end, blocksize;
2166	unsigned to;
2167	struct buffer_head *bh, *head;
2168	int ret = 1;
2169
2170	if (!page_has_buffers(page))
2171		return 0;
2172
2173	head = page_buffers(page);
 
 
2174	blocksize = head->b_size;
2175	to = min_t(unsigned, PAGE_SIZE - from, count);
2176	to = from + to;
2177	if (from < blocksize && to > PAGE_SIZE - blocksize)
2178		return 0;
2179
2180	bh = head;
2181	block_start = 0;
2182	do {
2183		block_end = block_start + blocksize;
2184		if (block_end > from && block_start < to) {
2185			if (!buffer_uptodate(bh)) {
2186				ret = 0;
2187				break;
2188			}
2189			if (block_end >= to)
2190				break;
2191		}
2192		block_start = block_end;
2193		bh = bh->b_this_page;
2194	} while (bh != head);
2195
2196	return ret;
2197}
2198EXPORT_SYMBOL(block_is_partially_uptodate);
2199
2200/*
2201 * Generic "read page" function for block devices that have the normal
2202 * get_block functionality. This is most of the block device filesystems.
2203 * Reads the page asynchronously --- the unlock_buffer() and
2204 * set/clear_buffer_uptodate() functions propagate buffer state into the
2205 * page struct once IO has completed.
2206 */
2207int block_read_full_page(struct page *page, get_block_t *get_block)
2208{
2209	struct inode *inode = page->mapping->host;
2210	sector_t iblock, lblock;
2211	struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2212	unsigned int blocksize, bbits;
2213	int nr, i;
2214	int fully_mapped = 1;
 
 
 
 
 
 
 
 
2215
2216	head = create_page_buffers(page, inode, 0);
2217	blocksize = head->b_size;
2218	bbits = block_size_bits(blocksize);
2219
2220	iblock = (sector_t)page->index << (PAGE_SHIFT - bbits);
2221	lblock = (i_size_read(inode)+blocksize-1) >> bbits;
2222	bh = head;
2223	nr = 0;
2224	i = 0;
2225
2226	do {
2227		if (buffer_uptodate(bh))
2228			continue;
2229
2230		if (!buffer_mapped(bh)) {
2231			int err = 0;
2232
2233			fully_mapped = 0;
2234			if (iblock < lblock) {
2235				WARN_ON(bh->b_size != blocksize);
2236				err = get_block(inode, iblock, bh, 0);
2237				if (err)
2238					SetPageError(page);
2239			}
2240			if (!buffer_mapped(bh)) {
2241				zero_user(page, i * blocksize, blocksize);
 
2242				if (!err)
2243					set_buffer_uptodate(bh);
2244				continue;
2245			}
2246			/*
2247			 * get_block() might have updated the buffer
2248			 * synchronously
2249			 */
2250			if (buffer_uptodate(bh))
2251				continue;
2252		}
2253		arr[nr++] = bh;
2254	} while (i++, iblock++, (bh = bh->b_this_page) != head);
2255
2256	if (fully_mapped)
2257		SetPageMappedToDisk(page);
2258
2259	if (!nr) {
2260		/*
2261		 * All buffers are uptodate - we can set the page uptodate
2262		 * as well. But not if get_block() returned an error.
2263		 */
2264		if (!PageError(page))
2265			SetPageUptodate(page);
2266		unlock_page(page);
2267		return 0;
2268	}
2269
2270	/* Stage two: lock the buffers */
2271	for (i = 0; i < nr; i++) {
2272		bh = arr[i];
2273		lock_buffer(bh);
2274		mark_buffer_async_read(bh);
2275	}
2276
2277	/*
2278	 * Stage 3: start the IO.  Check for uptodateness
2279	 * inside the buffer lock in case another process reading
2280	 * the underlying blockdev brought it uptodate (the sct fix).
2281	 */
2282	for (i = 0; i < nr; i++) {
2283		bh = arr[i];
2284		if (buffer_uptodate(bh))
2285			end_buffer_async_read(bh, 1);
2286		else
2287			submit_bh(REQ_OP_READ, 0, bh);
2288	}
2289	return 0;
2290}
2291EXPORT_SYMBOL(block_read_full_page);
2292
2293/* utility function for filesystems that need to do work on expanding
2294 * truncates.  Uses filesystem pagecache writes to allow the filesystem to
2295 * deal with the hole.  
2296 */
2297int generic_cont_expand_simple(struct inode *inode, loff_t size)
2298{
2299	struct address_space *mapping = inode->i_mapping;
2300	struct page *page;
2301	void *fsdata;
 
2302	int err;
2303
2304	err = inode_newsize_ok(inode, size);
2305	if (err)
2306		goto out;
2307
2308	err = pagecache_write_begin(NULL, mapping, size, 0,
2309				    AOP_FLAG_CONT_EXPAND, &page, &fsdata);
2310	if (err)
2311		goto out;
2312
2313	err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2314	BUG_ON(err > 0);
2315
2316out:
2317	return err;
2318}
2319EXPORT_SYMBOL(generic_cont_expand_simple);
2320
2321static int cont_expand_zero(struct file *file, struct address_space *mapping,
2322			    loff_t pos, loff_t *bytes)
2323{
2324	struct inode *inode = mapping->host;
 
2325	unsigned int blocksize = i_blocksize(inode);
2326	struct page *page;
2327	void *fsdata;
2328	pgoff_t index, curidx;
2329	loff_t curpos;
2330	unsigned zerofrom, offset, len;
2331	int err = 0;
2332
2333	index = pos >> PAGE_SHIFT;
2334	offset = pos & ~PAGE_MASK;
2335
2336	while (index > (curidx = (curpos = *bytes)>>PAGE_SHIFT)) {
2337		zerofrom = curpos & ~PAGE_MASK;
2338		if (zerofrom & (blocksize-1)) {
2339			*bytes |= (blocksize-1);
2340			(*bytes)++;
2341		}
2342		len = PAGE_SIZE - zerofrom;
2343
2344		err = pagecache_write_begin(file, mapping, curpos, len, 0,
2345					    &page, &fsdata);
2346		if (err)
2347			goto out;
2348		zero_user(page, zerofrom, len);
2349		err = pagecache_write_end(file, mapping, curpos, len, len,
2350						page, fsdata);
2351		if (err < 0)
2352			goto out;
2353		BUG_ON(err != len);
2354		err = 0;
2355
2356		balance_dirty_pages_ratelimited(mapping);
2357
2358		if (unlikely(fatal_signal_pending(current))) {
2359			err = -EINTR;
2360			goto out;
2361		}
2362	}
2363
2364	/* page covers the boundary, find the boundary offset */
2365	if (index == curidx) {
2366		zerofrom = curpos & ~PAGE_MASK;
2367		/* if we will expand the thing last block will be filled */
2368		if (offset <= zerofrom) {
2369			goto out;
2370		}
2371		if (zerofrom & (blocksize-1)) {
2372			*bytes |= (blocksize-1);
2373			(*bytes)++;
2374		}
2375		len = offset - zerofrom;
2376
2377		err = pagecache_write_begin(file, mapping, curpos, len, 0,
2378					    &page, &fsdata);
2379		if (err)
2380			goto out;
2381		zero_user(page, zerofrom, len);
2382		err = pagecache_write_end(file, mapping, curpos, len, len,
2383						page, fsdata);
2384		if (err < 0)
2385			goto out;
2386		BUG_ON(err != len);
2387		err = 0;
2388	}
2389out:
2390	return err;
2391}
2392
2393/*
2394 * For moronic filesystems that do not allow holes in file.
2395 * We may have to extend the file.
2396 */
2397int cont_write_begin(struct file *file, struct address_space *mapping,
2398			loff_t pos, unsigned len, unsigned flags,
2399			struct page **pagep, void **fsdata,
2400			get_block_t *get_block, loff_t *bytes)
2401{
2402	struct inode *inode = mapping->host;
2403	unsigned int blocksize = i_blocksize(inode);
2404	unsigned int zerofrom;
2405	int err;
2406
2407	err = cont_expand_zero(file, mapping, pos, bytes);
2408	if (err)
2409		return err;
2410
2411	zerofrom = *bytes & ~PAGE_MASK;
2412	if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2413		*bytes |= (blocksize-1);
2414		(*bytes)++;
2415	}
2416
2417	return block_write_begin(mapping, pos, len, flags, pagep, get_block);
2418}
2419EXPORT_SYMBOL(cont_write_begin);
2420
2421int block_commit_write(struct page *page, unsigned from, unsigned to)
2422{
2423	struct inode *inode = page->mapping->host;
2424	__block_commit_write(inode,page,from,to);
2425	return 0;
2426}
2427EXPORT_SYMBOL(block_commit_write);
2428
2429/*
2430 * block_page_mkwrite() is not allowed to change the file size as it gets
2431 * called from a page fault handler when a page is first dirtied. Hence we must
2432 * be careful to check for EOF conditions here. We set the page up correctly
2433 * for a written page which means we get ENOSPC checking when writing into
2434 * holes and correct delalloc and unwritten extent mapping on filesystems that
2435 * support these features.
2436 *
2437 * We are not allowed to take the i_mutex here so we have to play games to
2438 * protect against truncate races as the page could now be beyond EOF.  Because
2439 * truncate writes the inode size before removing pages, once we have the
2440 * page lock we can determine safely if the page is beyond EOF. If it is not
2441 * beyond EOF, then the page is guaranteed safe against truncation until we
2442 * unlock the page.
2443 *
2444 * Direct callers of this function should protect against filesystem freezing
2445 * using sb_start_pagefault() - sb_end_pagefault() functions.
2446 */
2447int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2448			 get_block_t get_block)
2449{
2450	struct page *page = vmf->page;
2451	struct inode *inode = file_inode(vma->vm_file);
2452	unsigned long end;
2453	loff_t size;
2454	int ret;
2455
2456	lock_page(page);
2457	size = i_size_read(inode);
2458	if ((page->mapping != inode->i_mapping) ||
2459	    (page_offset(page) > size)) {
2460		/* We overload EFAULT to mean page got truncated */
2461		ret = -EFAULT;
2462		goto out_unlock;
2463	}
2464
2465	/* page is wholly or partially inside EOF */
2466	if (((page->index + 1) << PAGE_SHIFT) > size)
2467		end = size & ~PAGE_MASK;
2468	else
2469		end = PAGE_SIZE;
 
 
 
2470
2471	ret = __block_write_begin(page, 0, end, get_block);
2472	if (!ret)
2473		ret = block_commit_write(page, 0, end);
2474
2475	if (unlikely(ret < 0))
2476		goto out_unlock;
2477	set_page_dirty(page);
2478	wait_for_stable_page(page);
2479	return 0;
2480out_unlock:
2481	unlock_page(page);
2482	return ret;
2483}
2484EXPORT_SYMBOL(block_page_mkwrite);
2485
2486/*
2487 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
2488 * immediately, while under the page lock.  So it needs a special end_io
2489 * handler which does not touch the bh after unlocking it.
2490 */
2491static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2492{
2493	__end_buffer_read_notouch(bh, uptodate);
2494}
2495
2496/*
2497 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2498 * the page (converting it to circular linked list and taking care of page
2499 * dirty races).
2500 */
2501static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2502{
2503	struct buffer_head *bh;
2504
2505	BUG_ON(!PageLocked(page));
2506
2507	spin_lock(&page->mapping->private_lock);
2508	bh = head;
2509	do {
2510		if (PageDirty(page))
2511			set_buffer_dirty(bh);
2512		if (!bh->b_this_page)
2513			bh->b_this_page = head;
2514		bh = bh->b_this_page;
2515	} while (bh != head);
2516	attach_page_buffers(page, head);
2517	spin_unlock(&page->mapping->private_lock);
2518}
2519
2520/*
2521 * On entry, the page is fully not uptodate.
2522 * On exit the page is fully uptodate in the areas outside (from,to)
2523 * The filesystem needs to handle block truncation upon failure.
2524 */
2525int nobh_write_begin(struct address_space *mapping,
2526			loff_t pos, unsigned len, unsigned flags,
2527			struct page **pagep, void **fsdata,
2528			get_block_t *get_block)
2529{
2530	struct inode *inode = mapping->host;
2531	const unsigned blkbits = inode->i_blkbits;
2532	const unsigned blocksize = 1 << blkbits;
2533	struct buffer_head *head, *bh;
2534	struct page *page;
2535	pgoff_t index;
2536	unsigned from, to;
2537	unsigned block_in_page;
2538	unsigned block_start, block_end;
2539	sector_t block_in_file;
2540	int nr_reads = 0;
2541	int ret = 0;
2542	int is_mapped_to_disk = 1;
2543
2544	index = pos >> PAGE_SHIFT;
2545	from = pos & (PAGE_SIZE - 1);
2546	to = from + len;
2547
2548	page = grab_cache_page_write_begin(mapping, index, flags);
2549	if (!page)
2550		return -ENOMEM;
2551	*pagep = page;
2552	*fsdata = NULL;
2553
2554	if (page_has_buffers(page)) {
2555		ret = __block_write_begin(page, pos, len, get_block);
2556		if (unlikely(ret))
2557			goto out_release;
2558		return ret;
2559	}
2560
2561	if (PageMappedToDisk(page))
2562		return 0;
2563
2564	/*
2565	 * Allocate buffers so that we can keep track of state, and potentially
2566	 * attach them to the page if an error occurs. In the common case of
2567	 * no error, they will just be freed again without ever being attached
2568	 * to the page (which is all OK, because we're under the page lock).
2569	 *
2570	 * Be careful: the buffer linked list is a NULL terminated one, rather
2571	 * than the circular one we're used to.
2572	 */
2573	head = alloc_page_buffers(page, blocksize, false);
2574	if (!head) {
2575		ret = -ENOMEM;
2576		goto out_release;
2577	}
2578
2579	block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits);
2580
2581	/*
2582	 * We loop across all blocks in the page, whether or not they are
2583	 * part of the affected region.  This is so we can discover if the
2584	 * page is fully mapped-to-disk.
2585	 */
2586	for (block_start = 0, block_in_page = 0, bh = head;
2587		  block_start < PAGE_SIZE;
2588		  block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
2589		int create;
2590
2591		block_end = block_start + blocksize;
2592		bh->b_state = 0;
2593		create = 1;
2594		if (block_start >= to)
2595			create = 0;
2596		ret = get_block(inode, block_in_file + block_in_page,
2597					bh, create);
2598		if (ret)
2599			goto failed;
2600		if (!buffer_mapped(bh))
2601			is_mapped_to_disk = 0;
2602		if (buffer_new(bh))
2603			clean_bdev_bh_alias(bh);
2604		if (PageUptodate(page)) {
2605			set_buffer_uptodate(bh);
2606			continue;
2607		}
2608		if (buffer_new(bh) || !buffer_mapped(bh)) {
2609			zero_user_segments(page, block_start, from,
2610							to, block_end);
2611			continue;
2612		}
2613		if (buffer_uptodate(bh))
2614			continue;	/* reiserfs does this */
2615		if (block_start < from || block_end > to) {
2616			lock_buffer(bh);
2617			bh->b_end_io = end_buffer_read_nobh;
2618			submit_bh(REQ_OP_READ, 0, bh);
2619			nr_reads++;
2620		}
2621	}
2622
2623	if (nr_reads) {
2624		/*
2625		 * The page is locked, so these buffers are protected from
2626		 * any VM or truncate activity.  Hence we don't need to care
2627		 * for the buffer_head refcounts.
2628		 */
2629		for (bh = head; bh; bh = bh->b_this_page) {
2630			wait_on_buffer(bh);
2631			if (!buffer_uptodate(bh))
2632				ret = -EIO;
2633		}
2634		if (ret)
2635			goto failed;
2636	}
2637
2638	if (is_mapped_to_disk)
2639		SetPageMappedToDisk(page);
2640
2641	*fsdata = head; /* to be released by nobh_write_end */
2642
2643	return 0;
2644
2645failed:
2646	BUG_ON(!ret);
2647	/*
2648	 * Error recovery is a bit difficult. We need to zero out blocks that
2649	 * were newly allocated, and dirty them to ensure they get written out.
2650	 * Buffers need to be attached to the page at this point, otherwise
2651	 * the handling of potential IO errors during writeout would be hard
2652	 * (could try doing synchronous writeout, but what if that fails too?)
2653	 */
2654	attach_nobh_buffers(page, head);
2655	page_zero_new_buffers(page, from, to);
2656
2657out_release:
2658	unlock_page(page);
2659	put_page(page);
2660	*pagep = NULL;
2661
2662	return ret;
2663}
2664EXPORT_SYMBOL(nobh_write_begin);
2665
2666int nobh_write_end(struct file *file, struct address_space *mapping,
2667			loff_t pos, unsigned len, unsigned copied,
2668			struct page *page, void *fsdata)
2669{
2670	struct inode *inode = page->mapping->host;
2671	struct buffer_head *head = fsdata;
2672	struct buffer_head *bh;
2673	BUG_ON(fsdata != NULL && page_has_buffers(page));
2674
2675	if (unlikely(copied < len) && head)
2676		attach_nobh_buffers(page, head);
2677	if (page_has_buffers(page))
2678		return generic_write_end(file, mapping, pos, len,
2679					copied, page, fsdata);
2680
2681	SetPageUptodate(page);
2682	set_page_dirty(page);
2683	if (pos+copied > inode->i_size) {
2684		i_size_write(inode, pos+copied);
2685		mark_inode_dirty(inode);
2686	}
2687
2688	unlock_page(page);
2689	put_page(page);
2690
2691	while (head) {
2692		bh = head;
2693		head = head->b_this_page;
2694		free_buffer_head(bh);
2695	}
2696
2697	return copied;
2698}
2699EXPORT_SYMBOL(nobh_write_end);
2700
2701/*
2702 * nobh_writepage() - based on block_full_write_page() except
2703 * that it tries to operate without attaching bufferheads to
2704 * the page.
2705 */
2706int nobh_writepage(struct page *page, get_block_t *get_block,
2707			struct writeback_control *wbc)
2708{
2709	struct inode * const inode = page->mapping->host;
2710	loff_t i_size = i_size_read(inode);
2711	const pgoff_t end_index = i_size >> PAGE_SHIFT;
2712	unsigned offset;
2713	int ret;
2714
2715	/* Is the page fully inside i_size? */
2716	if (page->index < end_index)
2717		goto out;
2718
2719	/* Is the page fully outside i_size? (truncate in progress) */
2720	offset = i_size & (PAGE_SIZE-1);
2721	if (page->index >= end_index+1 || !offset) {
2722		/*
2723		 * The page may have dirty, unmapped buffers.  For example,
2724		 * they may have been added in ext3_writepage().  Make them
2725		 * freeable here, so the page does not leak.
2726		 */
2727#if 0
2728		/* Not really sure about this  - do we need this ? */
2729		if (page->mapping->a_ops->invalidatepage)
2730			page->mapping->a_ops->invalidatepage(page, offset);
2731#endif
2732		unlock_page(page);
2733		return 0; /* don't care */
2734	}
2735
2736	/*
2737	 * The page straddles i_size.  It must be zeroed out on each and every
2738	 * writepage invocation because it may be mmapped.  "A file is mapped
2739	 * in multiples of the page size.  For a file that is not a multiple of
2740	 * the  page size, the remaining memory is zeroed when mapped, and
2741	 * writes to that region are not written out to the file."
2742	 */
2743	zero_user_segment(page, offset, PAGE_SIZE);
2744out:
2745	ret = mpage_writepage(page, get_block, wbc);
2746	if (ret == -EAGAIN)
2747		ret = __block_write_full_page(inode, page, get_block, wbc,
2748					      end_buffer_async_write);
2749	return ret;
2750}
2751EXPORT_SYMBOL(nobh_writepage);
2752
2753int nobh_truncate_page(struct address_space *mapping,
2754			loff_t from, get_block_t *get_block)
2755{
2756	pgoff_t index = from >> PAGE_SHIFT;
2757	unsigned offset = from & (PAGE_SIZE-1);
2758	unsigned blocksize;
2759	sector_t iblock;
2760	unsigned length, pos;
2761	struct inode *inode = mapping->host;
2762	struct page *page;
2763	struct buffer_head map_bh;
2764	int err;
2765
2766	blocksize = i_blocksize(inode);
2767	length = offset & (blocksize - 1);
2768
2769	/* Block boundary? Nothing to do */
2770	if (!length)
2771		return 0;
2772
2773	length = blocksize - length;
2774	iblock = (sector_t)index << (PAGE_SHIFT - inode->i_blkbits);
2775
2776	page = grab_cache_page(mapping, index);
2777	err = -ENOMEM;
2778	if (!page)
2779		goto out;
2780
2781	if (page_has_buffers(page)) {
2782has_buffers:
2783		unlock_page(page);
2784		put_page(page);
2785		return block_truncate_page(mapping, from, get_block);
2786	}
2787
2788	/* Find the buffer that contains "offset" */
2789	pos = blocksize;
2790	while (offset >= pos) {
2791		iblock++;
2792		pos += blocksize;
2793	}
2794
2795	map_bh.b_size = blocksize;
2796	map_bh.b_state = 0;
2797	err = get_block(inode, iblock, &map_bh, 0);
2798	if (err)
2799		goto unlock;
2800	/* unmapped? It's a hole - nothing to do */
2801	if (!buffer_mapped(&map_bh))
2802		goto unlock;
2803
2804	/* Ok, it's mapped. Make sure it's up-to-date */
2805	if (!PageUptodate(page)) {
2806		err = mapping->a_ops->readpage(NULL, page);
2807		if (err) {
2808			put_page(page);
2809			goto out;
2810		}
2811		lock_page(page);
2812		if (!PageUptodate(page)) {
2813			err = -EIO;
2814			goto unlock;
2815		}
2816		if (page_has_buffers(page))
2817			goto has_buffers;
2818	}
2819	zero_user(page, offset, length);
2820	set_page_dirty(page);
2821	err = 0;
2822
2823unlock:
2824	unlock_page(page);
2825	put_page(page);
2826out:
2827	return err;
2828}
2829EXPORT_SYMBOL(nobh_truncate_page);
2830
2831int block_truncate_page(struct address_space *mapping,
2832			loff_t from, get_block_t *get_block)
2833{
2834	pgoff_t index = from >> PAGE_SHIFT;
2835	unsigned offset = from & (PAGE_SIZE-1);
2836	unsigned blocksize;
2837	sector_t iblock;
2838	unsigned length, pos;
2839	struct inode *inode = mapping->host;
2840	struct page *page;
2841	struct buffer_head *bh;
2842	int err;
2843
2844	blocksize = i_blocksize(inode);
2845	length = offset & (blocksize - 1);
2846
2847	/* Block boundary? Nothing to do */
2848	if (!length)
2849		return 0;
2850
2851	length = blocksize - length;
2852	iblock = (sector_t)index << (PAGE_SHIFT - inode->i_blkbits);
2853	
2854	page = grab_cache_page(mapping, index);
2855	err = -ENOMEM;
2856	if (!page)
2857		goto out;
2858
2859	if (!page_has_buffers(page))
2860		create_empty_buffers(page, blocksize, 0);
 
 
 
 
 
2861
2862	/* Find the buffer that contains "offset" */
2863	bh = page_buffers(page);
2864	pos = blocksize;
2865	while (offset >= pos) {
2866		bh = bh->b_this_page;
2867		iblock++;
2868		pos += blocksize;
2869	}
2870
2871	err = 0;
2872	if (!buffer_mapped(bh)) {
2873		WARN_ON(bh->b_size != blocksize);
2874		err = get_block(inode, iblock, bh, 0);
2875		if (err)
2876			goto unlock;
2877		/* unmapped? It's a hole - nothing to do */
2878		if (!buffer_mapped(bh))
2879			goto unlock;
2880	}
2881
2882	/* Ok, it's mapped. Make sure it's up-to-date */
2883	if (PageUptodate(page))
2884		set_buffer_uptodate(bh);
2885
2886	if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
2887		err = -EIO;
2888		ll_rw_block(REQ_OP_READ, 0, 1, &bh);
2889		wait_on_buffer(bh);
2890		/* Uhhuh. Read error. Complain and punt. */
2891		if (!buffer_uptodate(bh))
2892			goto unlock;
2893	}
2894
2895	zero_user(page, offset, length);
2896	mark_buffer_dirty(bh);
2897	err = 0;
2898
2899unlock:
2900	unlock_page(page);
2901	put_page(page);
2902out:
2903	return err;
2904}
2905EXPORT_SYMBOL(block_truncate_page);
2906
2907/*
2908 * The generic ->writepage function for buffer-backed address_spaces
2909 */
2910int block_write_full_page(struct page *page, get_block_t *get_block,
2911			struct writeback_control *wbc)
2912{
2913	struct inode * const inode = page->mapping->host;
2914	loff_t i_size = i_size_read(inode);
2915	const pgoff_t end_index = i_size >> PAGE_SHIFT;
2916	unsigned offset;
2917
2918	/* Is the page fully inside i_size? */
2919	if (page->index < end_index)
2920		return __block_write_full_page(inode, page, get_block, wbc,
2921					       end_buffer_async_write);
2922
2923	/* Is the page fully outside i_size? (truncate in progress) */
2924	offset = i_size & (PAGE_SIZE-1);
2925	if (page->index >= end_index+1 || !offset) {
2926		/*
2927		 * The page may have dirty, unmapped buffers.  For example,
2928		 * they may have been added in ext3_writepage().  Make them
2929		 * freeable here, so the page does not leak.
2930		 */
2931		do_invalidatepage(page, 0, PAGE_SIZE);
2932		unlock_page(page);
2933		return 0; /* don't care */
2934	}
2935
2936	/*
2937	 * The page straddles i_size.  It must be zeroed out on each and every
2938	 * writepage invocation because it may be mmapped.  "A file is mapped
2939	 * in multiples of the page size.  For a file that is not a multiple of
2940	 * the  page size, the remaining memory is zeroed when mapped, and
2941	 * writes to that region are not written out to the file."
2942	 */
2943	zero_user_segment(page, offset, PAGE_SIZE);
2944	return __block_write_full_page(inode, page, get_block, wbc,
2945							end_buffer_async_write);
2946}
2947EXPORT_SYMBOL(block_write_full_page);
2948
2949sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2950			    get_block_t *get_block)
2951{
2952	struct inode *inode = mapping->host;
2953	struct buffer_head tmp = {
2954		.b_size = i_blocksize(inode),
2955	};
2956
2957	get_block(inode, block, &tmp, 0);
2958	return tmp.b_blocknr;
2959}
2960EXPORT_SYMBOL(generic_block_bmap);
2961
2962static void end_bio_bh_io_sync(struct bio *bio)
2963{
2964	struct buffer_head *bh = bio->bi_private;
2965
2966	if (unlikely(bio_flagged(bio, BIO_QUIET)))
2967		set_bit(BH_Quiet, &bh->b_state);
2968
2969	bh->b_end_io(bh, !bio->bi_status);
2970	bio_put(bio);
2971}
2972
2973/*
2974 * This allows us to do IO even on the odd last sectors
2975 * of a device, even if the block size is some multiple
2976 * of the physical sector size.
2977 *
2978 * We'll just truncate the bio to the size of the device,
2979 * and clear the end of the buffer head manually.
2980 *
2981 * Truly out-of-range accesses will turn into actual IO
2982 * errors, this only handles the "we need to be able to
2983 * do IO at the final sector" case.
2984 */
2985void guard_bio_eod(int op, struct bio *bio)
2986{
2987	sector_t maxsector;
2988	struct bio_vec *bvec = bio_last_bvec_all(bio);
2989	unsigned truncated_bytes;
2990	struct hd_struct *part;
2991
2992	rcu_read_lock();
2993	part = __disk_get_part(bio->bi_disk, bio->bi_partno);
2994	if (part)
2995		maxsector = part_nr_sects_read(part);
2996	else
2997		maxsector = get_capacity(bio->bi_disk);
2998	rcu_read_unlock();
2999
3000	if (!maxsector)
3001		return;
3002
3003	/*
3004	 * If the *whole* IO is past the end of the device,
3005	 * let it through, and the IO layer will turn it into
3006	 * an EIO.
3007	 */
3008	if (unlikely(bio->bi_iter.bi_sector >= maxsector))
3009		return;
3010
3011	maxsector -= bio->bi_iter.bi_sector;
3012	if (likely((bio->bi_iter.bi_size >> 9) <= maxsector))
3013		return;
3014
3015	/* Uhhuh. We've got a bio that straddles the device size! */
3016	truncated_bytes = bio->bi_iter.bi_size - (maxsector << 9);
3017
3018	/* Truncate the bio.. */
3019	bio->bi_iter.bi_size -= truncated_bytes;
3020	bvec->bv_len -= truncated_bytes;
3021
3022	/* ..and clear the end of the buffer for reads */
3023	if (op == REQ_OP_READ) {
3024		zero_user(bvec->bv_page, bvec->bv_offset + bvec->bv_len,
3025				truncated_bytes);
3026	}
3027}
3028
3029static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh,
3030			 enum rw_hint write_hint, struct writeback_control *wbc)
3031{
 
3032	struct bio *bio;
3033
3034	BUG_ON(!buffer_locked(bh));
3035	BUG_ON(!buffer_mapped(bh));
3036	BUG_ON(!bh->b_end_io);
3037	BUG_ON(buffer_delay(bh));
3038	BUG_ON(buffer_unwritten(bh));
3039
3040	/*
3041	 * Only clear out a write error when rewriting
3042	 */
3043	if (test_set_buffer_req(bh) && (op == REQ_OP_WRITE))
3044		clear_buffer_write_io_error(bh);
3045
3046	/*
3047	 * from here on down, it's all bio -- do the initial mapping,
3048	 * submit_bio -> generic_make_request may further map this bio around
3049	 */
3050	bio = bio_alloc(GFP_NOIO, 1);
 
3051
3052	if (wbc) {
3053		wbc_init_bio(wbc, bio);
3054		wbc_account_io(wbc, bh->b_page, bh->b_size);
3055	}
3056
3057	bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
3058	bio_set_dev(bio, bh->b_bdev);
3059	bio->bi_write_hint = write_hint;
3060
3061	bio_add_page(bio, bh->b_page, bh->b_size, bh_offset(bh));
3062	BUG_ON(bio->bi_iter.bi_size != bh->b_size);
3063
3064	bio->bi_end_io = end_bio_bh_io_sync;
3065	bio->bi_private = bh;
3066
3067	/* Take care of bh's that straddle the end of the device */
3068	guard_bio_eod(op, bio);
3069
3070	if (buffer_meta(bh))
3071		op_flags |= REQ_META;
3072	if (buffer_prio(bh))
3073		op_flags |= REQ_PRIO;
3074	bio_set_op_attrs(bio, op, op_flags);
3075
3076	submit_bio(bio);
3077	return 0;
3078}
3079
3080int submit_bh(int op, int op_flags, struct buffer_head *bh)
3081{
3082	return submit_bh_wbc(op, op_flags, bh, 0, NULL);
3083}
3084EXPORT_SYMBOL(submit_bh);
3085
3086/**
3087 * ll_rw_block: low-level access to block devices (DEPRECATED)
3088 * @op: whether to %READ or %WRITE
3089 * @op_flags: req_flag_bits
3090 * @nr: number of &struct buffer_heads in the array
3091 * @bhs: array of pointers to &struct buffer_head
3092 *
3093 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
3094 * requests an I/O operation on them, either a %REQ_OP_READ or a %REQ_OP_WRITE.
3095 * @op_flags contains flags modifying the detailed I/O behavior, most notably
3096 * %REQ_RAHEAD.
3097 *
3098 * This function drops any buffer that it cannot get a lock on (with the
3099 * BH_Lock state bit), any buffer that appears to be clean when doing a write
3100 * request, and any buffer that appears to be up-to-date when doing read
3101 * request.  Further it marks as clean buffers that are processed for
3102 * writing (the buffer cache won't assume that they are actually clean
3103 * until the buffer gets unlocked).
3104 *
3105 * ll_rw_block sets b_end_io to simple completion handler that marks
3106 * the buffer up-to-date (if appropriate), unlocks the buffer and wakes
3107 * any waiters. 
3108 *
3109 * All of the buffers must be for the same device, and must also be a
3110 * multiple of the current approved size for the device.
3111 */
3112void ll_rw_block(int op, int op_flags,  int nr, struct buffer_head *bhs[])
3113{
3114	int i;
3115
3116	for (i = 0; i < nr; i++) {
3117		struct buffer_head *bh = bhs[i];
3118
3119		if (!trylock_buffer(bh))
3120			continue;
3121		if (op == WRITE) {
3122			if (test_clear_buffer_dirty(bh)) {
3123				bh->b_end_io = end_buffer_write_sync;
3124				get_bh(bh);
3125				submit_bh(op, op_flags, bh);
3126				continue;
3127			}
3128		} else {
3129			if (!buffer_uptodate(bh)) {
3130				bh->b_end_io = end_buffer_read_sync;
3131				get_bh(bh);
3132				submit_bh(op, op_flags, bh);
3133				continue;
3134			}
3135		}
3136		unlock_buffer(bh);
3137	}
3138}
3139EXPORT_SYMBOL(ll_rw_block);
3140
3141void write_dirty_buffer(struct buffer_head *bh, int op_flags)
3142{
3143	lock_buffer(bh);
3144	if (!test_clear_buffer_dirty(bh)) {
3145		unlock_buffer(bh);
3146		return;
3147	}
3148	bh->b_end_io = end_buffer_write_sync;
3149	get_bh(bh);
3150	submit_bh(REQ_OP_WRITE, op_flags, bh);
3151}
3152EXPORT_SYMBOL(write_dirty_buffer);
3153
3154/*
3155 * For a data-integrity writeout, we need to wait upon any in-progress I/O
3156 * and then start new I/O and then wait upon it.  The caller must have a ref on
3157 * the buffer_head.
3158 */
3159int __sync_dirty_buffer(struct buffer_head *bh, int op_flags)
3160{
3161	int ret = 0;
3162
3163	WARN_ON(atomic_read(&bh->b_count) < 1);
3164	lock_buffer(bh);
3165	if (test_clear_buffer_dirty(bh)) {
 
 
 
 
 
 
 
 
 
3166		get_bh(bh);
3167		bh->b_end_io = end_buffer_write_sync;
3168		ret = submit_bh(REQ_OP_WRITE, op_flags, bh);
3169		wait_on_buffer(bh);
3170		if (!ret && !buffer_uptodate(bh))
3171			ret = -EIO;
3172	} else {
3173		unlock_buffer(bh);
3174	}
3175	return ret;
3176}
3177EXPORT_SYMBOL(__sync_dirty_buffer);
3178
3179int sync_dirty_buffer(struct buffer_head *bh)
3180{
3181	return __sync_dirty_buffer(bh, REQ_SYNC);
3182}
3183EXPORT_SYMBOL(sync_dirty_buffer);
3184
3185/*
3186 * try_to_free_buffers() checks if all the buffers on this particular page
3187 * are unused, and releases them if so.
3188 *
3189 * Exclusion against try_to_free_buffers may be obtained by either
3190 * locking the page or by holding its mapping's private_lock.
3191 *
3192 * If the page is dirty but all the buffers are clean then we need to
3193 * be sure to mark the page clean as well.  This is because the page
3194 * may be against a block device, and a later reattachment of buffers
3195 * to a dirty page will set *all* buffers dirty.  Which would corrupt
3196 * filesystem data on the same device.
3197 *
3198 * The same applies to regular filesystem pages: if all the buffers are
3199 * clean then we set the page clean and proceed.  To do that, we require
3200 * total exclusion from __set_page_dirty_buffers().  That is obtained with
3201 * private_lock.
3202 *
3203 * try_to_free_buffers() is non-blocking.
3204 */
3205static inline int buffer_busy(struct buffer_head *bh)
3206{
3207	return atomic_read(&bh->b_count) |
3208		(bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3209}
3210
3211static int
3212drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3213{
3214	struct buffer_head *head = page_buffers(page);
3215	struct buffer_head *bh;
3216
3217	bh = head;
3218	do {
3219		if (buffer_busy(bh))
3220			goto failed;
3221		bh = bh->b_this_page;
3222	} while (bh != head);
3223
3224	do {
3225		struct buffer_head *next = bh->b_this_page;
3226
3227		if (bh->b_assoc_map)
3228			__remove_assoc_queue(bh);
3229		bh = next;
3230	} while (bh != head);
3231	*buffers_to_free = head;
3232	__clear_page_buffers(page);
3233	return 1;
3234failed:
3235	return 0;
3236}
3237
3238int try_to_free_buffers(struct page *page)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
3239{
3240	struct address_space * const mapping = page->mapping;
3241	struct buffer_head *buffers_to_free = NULL;
3242	int ret = 0;
3243
3244	BUG_ON(!PageLocked(page));
3245	if (PageWriteback(page))
3246		return 0;
3247
3248	if (mapping == NULL) {		/* can this still happen? */
3249		ret = drop_buffers(page, &buffers_to_free);
3250		goto out;
3251	}
3252
3253	spin_lock(&mapping->private_lock);
3254	ret = drop_buffers(page, &buffers_to_free);
3255
3256	/*
3257	 * If the filesystem writes its buffers by hand (eg ext3)
3258	 * then we can have clean buffers against a dirty page.  We
3259	 * clean the page here; otherwise the VM will never notice
3260	 * that the filesystem did any IO at all.
3261	 *
3262	 * Also, during truncate, discard_buffer will have marked all
3263	 * the page's buffers clean.  We discover that here and clean
3264	 * the page also.
3265	 *
3266	 * private_lock must be held over this entire operation in order
3267	 * to synchronise against __set_page_dirty_buffers and prevent the
3268	 * dirty bit from being lost.
3269	 */
3270	if (ret)
3271		cancel_dirty_page(page);
3272	spin_unlock(&mapping->private_lock);
3273out:
3274	if (buffers_to_free) {
3275		struct buffer_head *bh = buffers_to_free;
3276
3277		do {
3278			struct buffer_head *next = bh->b_this_page;
3279			free_buffer_head(bh);
3280			bh = next;
3281		} while (bh != buffers_to_free);
3282	}
3283	return ret;
3284}
3285EXPORT_SYMBOL(try_to_free_buffers);
3286
3287/*
3288 * There are no bdflush tunables left.  But distributions are
3289 * still running obsolete flush daemons, so we terminate them here.
3290 *
3291 * Use of bdflush() is deprecated and will be removed in a future kernel.
3292 * The `flush-X' kernel threads fully replace bdflush daemons and this call.
3293 */
3294SYSCALL_DEFINE2(bdflush, int, func, long, data)
3295{
3296	static int msg_count;
3297
3298	if (!capable(CAP_SYS_ADMIN))
3299		return -EPERM;
3300
3301	if (msg_count < 5) {
3302		msg_count++;
3303		printk(KERN_INFO
3304			"warning: process `%s' used the obsolete bdflush"
3305			" system call\n", current->comm);
3306		printk(KERN_INFO "Fix your initscripts?\n");
3307	}
3308
3309	if (func == 1)
3310		do_exit(0);
3311	return 0;
3312}
3313
3314/*
3315 * Buffer-head allocation
3316 */
3317static struct kmem_cache *bh_cachep __read_mostly;
3318
3319/*
3320 * Once the number of bh's in the machine exceeds this level, we start
3321 * stripping them in writeback.
3322 */
3323static unsigned long max_buffer_heads;
3324
3325int buffer_heads_over_limit;
3326
3327struct bh_accounting {
3328	int nr;			/* Number of live bh's */
3329	int ratelimit;		/* Limit cacheline bouncing */
3330};
3331
3332static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3333
3334static void recalc_bh_state(void)
3335{
3336	int i;
3337	int tot = 0;
3338
3339	if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
3340		return;
3341	__this_cpu_write(bh_accounting.ratelimit, 0);
3342	for_each_online_cpu(i)
3343		tot += per_cpu(bh_accounting, i).nr;
3344	buffer_heads_over_limit = (tot > max_buffer_heads);
3345}
3346
3347struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
3348{
3349	struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
3350	if (ret) {
3351		INIT_LIST_HEAD(&ret->b_assoc_buffers);
 
3352		preempt_disable();
3353		__this_cpu_inc(bh_accounting.nr);
3354		recalc_bh_state();
3355		preempt_enable();
3356	}
3357	return ret;
3358}
3359EXPORT_SYMBOL(alloc_buffer_head);
3360
3361void free_buffer_head(struct buffer_head *bh)
3362{
3363	BUG_ON(!list_empty(&bh->b_assoc_buffers));
3364	kmem_cache_free(bh_cachep, bh);
3365	preempt_disable();
3366	__this_cpu_dec(bh_accounting.nr);
3367	recalc_bh_state();
3368	preempt_enable();
3369}
3370EXPORT_SYMBOL(free_buffer_head);
3371
3372static int buffer_exit_cpu_dead(unsigned int cpu)
3373{
3374	int i;
3375	struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3376
3377	for (i = 0; i < BH_LRU_SIZE; i++) {
3378		brelse(b->bhs[i]);
3379		b->bhs[i] = NULL;
3380	}
3381	this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
3382	per_cpu(bh_accounting, cpu).nr = 0;
3383	return 0;
3384}
3385
3386/**
3387 * bh_uptodate_or_lock - Test whether the buffer is uptodate
3388 * @bh: struct buffer_head
3389 *
3390 * Return true if the buffer is up-to-date and false,
3391 * with the buffer locked, if not.
3392 */
3393int bh_uptodate_or_lock(struct buffer_head *bh)
3394{
3395	if (!buffer_uptodate(bh)) {
3396		lock_buffer(bh);
3397		if (!buffer_uptodate(bh))
3398			return 0;
3399		unlock_buffer(bh);
3400	}
3401	return 1;
3402}
3403EXPORT_SYMBOL(bh_uptodate_or_lock);
3404
3405/**
3406 * bh_submit_read - Submit a locked buffer for reading
3407 * @bh: struct buffer_head
 
 
3408 *
3409 * Returns zero on success and -EIO on error.
3410 */
3411int bh_submit_read(struct buffer_head *bh)
3412{
 
 
3413	BUG_ON(!buffer_locked(bh));
3414
3415	if (buffer_uptodate(bh)) {
3416		unlock_buffer(bh);
3417		return 0;
3418	}
3419
3420	get_bh(bh);
3421	bh->b_end_io = end_buffer_read_sync;
3422	submit_bh(REQ_OP_READ, 0, bh);
3423	wait_on_buffer(bh);
3424	if (buffer_uptodate(bh))
3425		return 0;
3426	return -EIO;
 
 
3427}
3428EXPORT_SYMBOL(bh_submit_read);
3429
3430/*
3431 * Seek for SEEK_DATA / SEEK_HOLE within @page, starting at @lastoff.
 
 
 
 
 
3432 *
3433 * Returns the offset within the file on success, and -ENOENT otherwise.
3434 */
3435static loff_t
3436page_seek_hole_data(struct page *page, loff_t lastoff, int whence)
3437{
3438	loff_t offset = page_offset(page);
3439	struct buffer_head *bh, *head;
3440	bool seek_data = whence == SEEK_DATA;
3441
3442	if (lastoff < offset)
3443		lastoff = offset;
3444
3445	bh = head = page_buffers(page);
3446	do {
3447		offset += bh->b_size;
3448		if (lastoff >= offset)
3449			continue;
3450
3451		/*
3452		 * Unwritten extents that have data in the page cache covering
3453		 * them can be identified by the BH_Unwritten state flag.
3454		 * Pages with multiple buffers might have a mix of holes, data
3455		 * and unwritten extents - any buffer with valid data in it
3456		 * should have BH_Uptodate flag set on it.
3457		 */
3458
3459		if ((buffer_unwritten(bh) || buffer_uptodate(bh)) == seek_data)
3460			return lastoff;
3461
3462		lastoff = offset;
3463	} while ((bh = bh->b_this_page) != head);
3464	return -ENOENT;
3465}
3466
3467/*
3468 * Seek for SEEK_DATA / SEEK_HOLE in the page cache.
3469 *
3470 * Within unwritten extents, the page cache determines which parts are holes
3471 * and which are data: unwritten and uptodate buffer heads count as data;
3472 * everything else counts as a hole.
3473 *
3474 * Returns the resulting offset on successs, and -ENOENT otherwise.
3475 */
3476loff_t
3477page_cache_seek_hole_data(struct inode *inode, loff_t offset, loff_t length,
3478			  int whence)
3479{
3480	pgoff_t index = offset >> PAGE_SHIFT;
3481	pgoff_t end = DIV_ROUND_UP(offset + length, PAGE_SIZE);
3482	loff_t lastoff = offset;
3483	struct pagevec pvec;
3484
3485	if (length <= 0)
3486		return -ENOENT;
3487
3488	pagevec_init(&pvec);
3489
3490	do {
3491		unsigned nr_pages, i;
3492
3493		nr_pages = pagevec_lookup_range(&pvec, inode->i_mapping, &index,
3494						end - 1);
3495		if (nr_pages == 0)
3496			break;
3497
3498		for (i = 0; i < nr_pages; i++) {
3499			struct page *page = pvec.pages[i];
3500
3501			/*
3502			 * At this point, the page may be truncated or
3503			 * invalidated (changing page->mapping to NULL), or
3504			 * even swizzled back from swapper_space to tmpfs file
3505			 * mapping.  However, page->index will not change
3506			 * because we have a reference on the page.
3507                         *
3508			 * If current page offset is beyond where we've ended,
3509			 * we've found a hole.
3510                         */
3511			if (whence == SEEK_HOLE &&
3512			    lastoff < page_offset(page))
3513				goto check_range;
3514
3515			lock_page(page);
3516			if (likely(page->mapping == inode->i_mapping) &&
3517			    page_has_buffers(page)) {
3518				lastoff = page_seek_hole_data(page, lastoff, whence);
3519				if (lastoff >= 0) {
3520					unlock_page(page);
3521					goto check_range;
3522				}
3523			}
3524			unlock_page(page);
3525			lastoff = page_offset(page) + PAGE_SIZE;
3526		}
3527		pagevec_release(&pvec);
3528	} while (index < end);
3529
3530	/* When no page at lastoff and we are not done, we found a hole. */
3531	if (whence != SEEK_HOLE)
3532		goto not_found;
3533
3534check_range:
3535	if (lastoff < offset + length)
3536		goto out;
3537not_found:
3538	lastoff = -ENOENT;
3539out:
3540	pagevec_release(&pvec);
3541	return lastoff;
3542}
 
3543
3544void __init buffer_init(void)
3545{
3546	unsigned long nrpages;
3547	int ret;
3548
3549	bh_cachep = kmem_cache_create("buffer_head",
3550			sizeof(struct buffer_head), 0,
3551				(SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3552				SLAB_MEM_SPREAD),
3553				NULL);
3554
3555	/*
3556	 * Limit the bh occupancy to 10% of ZONE_NORMAL
3557	 */
3558	nrpages = (nr_free_buffer_pages() * 10) / 100;
3559	max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3560	ret = cpuhp_setup_state_nocalls(CPUHP_FS_BUFF_DEAD, "fs/buffer:dead",
3561					NULL, buffer_exit_cpu_dead);
3562	WARN_ON(ret < 0);
3563}