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 inode *bd_inode = bdev->bd_inode;
 193	struct address_space *bd_mapping = bd_inode->i_mapping;
 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 << bd_inode->i_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 << bd_inode->i_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		folio_set_error(folio);
 262	}
 263
 264	/*
 265	 * Be _very_ careful from here on. Bad things can happen if
 266	 * two buffer heads end IO at almost the same time and both
 267	 * decide that the page is now completely done.
 268	 */
 269	first = folio_buffers(folio);
 270	spin_lock_irqsave(&first->b_uptodate_lock, flags);
 271	clear_buffer_async_read(bh);
 272	unlock_buffer(bh);
 273	tmp = bh;
 274	do {
 275		if (!buffer_uptodate(tmp))
 276			folio_uptodate = 0;
 277		if (buffer_async_read(tmp)) {
 278			BUG_ON(!buffer_locked(tmp));
 279			goto still_busy;
 280		}
 281		tmp = tmp->b_this_page;
 282	} while (tmp != bh);
 283	spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
 284
 285	folio_end_read(folio, folio_uptodate);
 
 
 
 
 
 
 286	return;
 287
 288still_busy:
 289	spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
 290	return;
 291}
 292
 293struct postprocess_bh_ctx {
 294	struct work_struct work;
 295	struct buffer_head *bh;
 296};
 297
 298static void verify_bh(struct work_struct *work)
 299{
 300	struct postprocess_bh_ctx *ctx =
 301		container_of(work, struct postprocess_bh_ctx, work);
 302	struct buffer_head *bh = ctx->bh;
 303	bool valid;
 304
 305	valid = fsverity_verify_blocks(bh->b_folio, bh->b_size, bh_offset(bh));
 306	end_buffer_async_read(bh, valid);
 307	kfree(ctx);
 308}
 309
 310static bool need_fsverity(struct buffer_head *bh)
 311{
 312	struct folio *folio = bh->b_folio;
 313	struct inode *inode = folio->mapping->host;
 314
 315	return fsverity_active(inode) &&
 316		/* needed by ext4 */
 317		folio->index < DIV_ROUND_UP(inode->i_size, PAGE_SIZE);
 318}
 319
 320static void decrypt_bh(struct work_struct *work)
 321{
 322	struct postprocess_bh_ctx *ctx =
 323		container_of(work, struct postprocess_bh_ctx, work);
 324	struct buffer_head *bh = ctx->bh;
 325	int err;
 326
 327	err = fscrypt_decrypt_pagecache_blocks(bh->b_folio, bh->b_size,
 328					       bh_offset(bh));
 329	if (err == 0 && need_fsverity(bh)) {
 330		/*
 331		 * We use different work queues for decryption and for verity
 332		 * because verity may require reading metadata pages that need
 333		 * decryption, and we shouldn't recurse to the same workqueue.
 334		 */
 335		INIT_WORK(&ctx->work, verify_bh);
 336		fsverity_enqueue_verify_work(&ctx->work);
 337		return;
 338	}
 339	end_buffer_async_read(bh, err == 0);
 340	kfree(ctx);
 341}
 342
 343/*
 344 * I/O completion handler for block_read_full_folio() - pages
 345 * which come unlocked at the end of I/O.
 346 */
 347static void end_buffer_async_read_io(struct buffer_head *bh, int uptodate)
 348{
 349	struct inode *inode = bh->b_folio->mapping->host;
 350	bool decrypt = fscrypt_inode_uses_fs_layer_crypto(inode);
 351	bool verify = need_fsverity(bh);
 352
 353	/* Decrypt (with fscrypt) and/or verify (with fsverity) if needed. */
 354	if (uptodate && (decrypt || verify)) {
 355		struct postprocess_bh_ctx *ctx =
 356			kmalloc(sizeof(*ctx), GFP_ATOMIC);
 357
 358		if (ctx) {
 
 359			ctx->bh = bh;
 360			if (decrypt) {
 361				INIT_WORK(&ctx->work, decrypt_bh);
 362				fscrypt_enqueue_decrypt_work(&ctx->work);
 363			} else {
 364				INIT_WORK(&ctx->work, verify_bh);
 365				fsverity_enqueue_verify_work(&ctx->work);
 366			}
 367			return;
 368		}
 369		uptodate = 0;
 370	}
 371	end_buffer_async_read(bh, uptodate);
 372}
 373
 374/*
 375 * Completion handler for block_write_full_folio() - folios which are unlocked
 376 * during I/O, and which have the writeback flag cleared upon I/O completion.
 377 */
 378static void end_buffer_async_write(struct buffer_head *bh, int uptodate)
 379{
 380	unsigned long flags;
 381	struct buffer_head *first;
 382	struct buffer_head *tmp;
 383	struct folio *folio;
 384
 385	BUG_ON(!buffer_async_write(bh));
 386
 387	folio = bh->b_folio;
 388	if (uptodate) {
 389		set_buffer_uptodate(bh);
 390	} else {
 391		buffer_io_error(bh, ", lost async page write");
 392		mark_buffer_write_io_error(bh);
 393		clear_buffer_uptodate(bh);
 394		folio_set_error(folio);
 395	}
 396
 397	first = folio_buffers(folio);
 398	spin_lock_irqsave(&first->b_uptodate_lock, flags);
 399
 400	clear_buffer_async_write(bh);
 401	unlock_buffer(bh);
 402	tmp = bh->b_this_page;
 403	while (tmp != bh) {
 404		if (buffer_async_write(tmp)) {
 405			BUG_ON(!buffer_locked(tmp));
 406			goto still_busy;
 407		}
 408		tmp = tmp->b_this_page;
 409	}
 410	spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
 411	folio_end_writeback(folio);
 412	return;
 413
 414still_busy:
 415	spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
 416	return;
 417}
 
 418
 419/*
 420 * If a page's buffers are under async readin (end_buffer_async_read
 421 * completion) then there is a possibility that another thread of
 422 * control could lock one of the buffers after it has completed
 423 * but while some of the other buffers have not completed.  This
 424 * locked buffer would confuse end_buffer_async_read() into not unlocking
 425 * the page.  So the absence of BH_Async_Read tells end_buffer_async_read()
 426 * that this buffer is not under async I/O.
 427 *
 428 * The page comes unlocked when it has no locked buffer_async buffers
 429 * left.
 430 *
 431 * PageLocked prevents anyone starting new async I/O reads any of
 432 * the buffers.
 433 *
 434 * PageWriteback is used to prevent simultaneous writeout of the same
 435 * page.
 436 *
 437 * PageLocked prevents anyone from starting writeback of a page which is
 438 * under read I/O (PageWriteback is only ever set against a locked page).
 439 */
 440static void mark_buffer_async_read(struct buffer_head *bh)
 441{
 442	bh->b_end_io = end_buffer_async_read_io;
 443	set_buffer_async_read(bh);
 444}
 445
 446static void mark_buffer_async_write_endio(struct buffer_head *bh,
 447					  bh_end_io_t *handler)
 448{
 449	bh->b_end_io = handler;
 450	set_buffer_async_write(bh);
 451}
 452
 453void mark_buffer_async_write(struct buffer_head *bh)
 454{
 455	mark_buffer_async_write_endio(bh, end_buffer_async_write);
 456}
 457EXPORT_SYMBOL(mark_buffer_async_write);
 458
 459
 460/*
 461 * fs/buffer.c contains helper functions for buffer-backed address space's
 462 * fsync functions.  A common requirement for buffer-based filesystems is
 463 * that certain data from the backing blockdev needs to be written out for
 464 * a successful fsync().  For example, ext2 indirect blocks need to be
 465 * written back and waited upon before fsync() returns.
 466 *
 467 * The functions mark_buffer_dirty_inode(), fsync_inode_buffers(),
 468 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
 469 * management of a list of dependent buffers at ->i_mapping->i_private_list.
 470 *
 471 * Locking is a little subtle: try_to_free_buffers() will remove buffers
 472 * from their controlling inode's queue when they are being freed.  But
 473 * try_to_free_buffers() will be operating against the *blockdev* mapping
 474 * at the time, not against the S_ISREG file which depends on those buffers.
 475 * So the locking for i_private_list is via the i_private_lock in the address_space
 476 * which backs the buffers.  Which is different from the address_space 
 477 * against which the buffers are listed.  So for a particular address_space,
 478 * mapping->i_private_lock does *not* protect mapping->i_private_list!  In fact,
 479 * mapping->i_private_list will always be protected by the backing blockdev's
 480 * ->i_private_lock.
 481 *
 482 * Which introduces a requirement: all buffers on an address_space's
 483 * ->i_private_list must be from the same address_space: the blockdev's.
 484 *
 485 * address_spaces which do not place buffers at ->i_private_list via these
 486 * utility functions are free to use i_private_lock and i_private_list for
 487 * whatever they want.  The only requirement is that list_empty(i_private_list)
 488 * be true at clear_inode() time.
 489 *
 490 * FIXME: clear_inode should not call invalidate_inode_buffers().  The
 491 * filesystems should do that.  invalidate_inode_buffers() should just go
 492 * BUG_ON(!list_empty).
 493 *
 494 * FIXME: mark_buffer_dirty_inode() is a data-plane operation.  It should
 495 * take an address_space, not an inode.  And it should be called
 496 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
 497 * queued up.
 498 *
 499 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
 500 * list if it is already on a list.  Because if the buffer is on a list,
 501 * it *must* already be on the right one.  If not, the filesystem is being
 502 * silly.  This will save a ton of locking.  But first we have to ensure
 503 * that buffers are taken *off* the old inode's list when they are freed
 504 * (presumably in truncate).  That requires careful auditing of all
 505 * filesystems (do it inside bforget()).  It could also be done by bringing
 506 * b_inode back.
 507 */
 508
 509/*
 510 * The buffer's backing address_space's i_private_lock must be held
 511 */
 512static void __remove_assoc_queue(struct buffer_head *bh)
 513{
 514	list_del_init(&bh->b_assoc_buffers);
 515	WARN_ON(!bh->b_assoc_map);
 516	bh->b_assoc_map = NULL;
 517}
 518
 519int inode_has_buffers(struct inode *inode)
 520{
 521	return !list_empty(&inode->i_data.i_private_list);
 522}
 523
 524/*
 525 * osync is designed to support O_SYNC io.  It waits synchronously for
 526 * all already-submitted IO to complete, but does not queue any new
 527 * writes to the disk.
 528 *
 529 * To do O_SYNC writes, just queue the buffer writes with write_dirty_buffer
 530 * as you dirty the buffers, and then use osync_inode_buffers to wait for
 531 * completion.  Any other dirty buffers which are not yet queued for
 532 * write will not be flushed to disk by the osync.
 533 */
 534static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
 535{
 536	struct buffer_head *bh;
 537	struct list_head *p;
 538	int err = 0;
 539
 540	spin_lock(lock);
 541repeat:
 542	list_for_each_prev(p, list) {
 543		bh = BH_ENTRY(p);
 544		if (buffer_locked(bh)) {
 545			get_bh(bh);
 546			spin_unlock(lock);
 547			wait_on_buffer(bh);
 548			if (!buffer_uptodate(bh))
 549				err = -EIO;
 550			brelse(bh);
 551			spin_lock(lock);
 552			goto repeat;
 553		}
 554	}
 555	spin_unlock(lock);
 556	return err;
 557}
 558
 
 
 
 
 
 
 559/**
 560 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
 561 * @mapping: the mapping which wants those buffers written
 562 *
 563 * Starts I/O against the buffers at mapping->i_private_list, and waits upon
 564 * that I/O.
 565 *
 566 * Basically, this is a convenience function for fsync().
 567 * @mapping is a file or directory which needs those buffers to be written for
 568 * a successful fsync().
 569 */
 570int sync_mapping_buffers(struct address_space *mapping)
 571{
 572	struct address_space *buffer_mapping = mapping->i_private_data;
 573
 574	if (buffer_mapping == NULL || list_empty(&mapping->i_private_list))
 575		return 0;
 576
 577	return fsync_buffers_list(&buffer_mapping->i_private_lock,
 578					&mapping->i_private_list);
 579}
 580EXPORT_SYMBOL(sync_mapping_buffers);
 581
 582/**
 583 * generic_buffers_fsync_noflush - generic buffer fsync implementation
 584 * for simple filesystems with no inode lock
 585 *
 586 * @file:	file to synchronize
 587 * @start:	start offset in bytes
 588 * @end:	end offset in bytes (inclusive)
 589 * @datasync:	only synchronize essential metadata if true
 590 *
 591 * This is a generic implementation of the fsync method for simple
 592 * filesystems which track all non-inode metadata in the buffers list
 593 * hanging off the address_space structure.
 594 */
 595int generic_buffers_fsync_noflush(struct file *file, loff_t start, loff_t end,
 596				  bool datasync)
 597{
 598	struct inode *inode = file->f_mapping->host;
 599	int err;
 600	int ret;
 601
 602	err = file_write_and_wait_range(file, start, end);
 603	if (err)
 604		return err;
 605
 606	ret = sync_mapping_buffers(inode->i_mapping);
 607	if (!(inode->i_state & I_DIRTY_ALL))
 608		goto out;
 609	if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
 610		goto out;
 611
 612	err = sync_inode_metadata(inode, 1);
 613	if (ret == 0)
 614		ret = err;
 615
 616out:
 617	/* check and advance again to catch errors after syncing out buffers */
 618	err = file_check_and_advance_wb_err(file);
 619	if (ret == 0)
 620		ret = err;
 621	return ret;
 622}
 623EXPORT_SYMBOL(generic_buffers_fsync_noflush);
 624
 625/**
 626 * generic_buffers_fsync - generic buffer fsync implementation
 627 * for simple filesystems with no inode lock
 628 *
 629 * @file:	file to synchronize
 630 * @start:	start offset in bytes
 631 * @end:	end offset in bytes (inclusive)
 632 * @datasync:	only synchronize essential metadata if true
 633 *
 634 * This is a generic implementation of the fsync method for simple
 635 * filesystems which track all non-inode metadata in the buffers list
 636 * hanging off the address_space structure. This also makes sure that
 637 * a device cache flush operation is called at the end.
 638 */
 639int generic_buffers_fsync(struct file *file, loff_t start, loff_t end,
 640			  bool datasync)
 641{
 642	struct inode *inode = file->f_mapping->host;
 643	int ret;
 644
 645	ret = generic_buffers_fsync_noflush(file, start, end, datasync);
 646	if (!ret)
 647		ret = blkdev_issue_flush(inode->i_sb->s_bdev);
 648	return ret;
 649}
 650EXPORT_SYMBOL(generic_buffers_fsync);
 651
 652/*
 653 * Called when we've recently written block `bblock', and it is known that
 654 * `bblock' was for a buffer_boundary() buffer.  This means that the block at
 655 * `bblock + 1' is probably a dirty indirect block.  Hunt it down and, if it's
 656 * dirty, schedule it for IO.  So that indirects merge nicely with their data.
 657 */
 658void write_boundary_block(struct block_device *bdev,
 659			sector_t bblock, unsigned blocksize)
 660{
 661	struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
 662	if (bh) {
 663		if (buffer_dirty(bh))
 664			write_dirty_buffer(bh, 0);
 665		put_bh(bh);
 666	}
 667}
 668
 669void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
 670{
 671	struct address_space *mapping = inode->i_mapping;
 672	struct address_space *buffer_mapping = bh->b_folio->mapping;
 673
 674	mark_buffer_dirty(bh);
 675	if (!mapping->i_private_data) {
 676		mapping->i_private_data = buffer_mapping;
 677	} else {
 678		BUG_ON(mapping->i_private_data != buffer_mapping);
 679	}
 680	if (!bh->b_assoc_map) {
 681		spin_lock(&buffer_mapping->i_private_lock);
 682		list_move_tail(&bh->b_assoc_buffers,
 683				&mapping->i_private_list);
 684		bh->b_assoc_map = mapping;
 685		spin_unlock(&buffer_mapping->i_private_lock);
 686	}
 687}
 688EXPORT_SYMBOL(mark_buffer_dirty_inode);
 689
 690/*
 691 * Add a page to the dirty page list.
 692 *
 693 * It is a sad fact of life that this function is called from several places
 694 * deeply under spinlocking.  It may not sleep.
 695 *
 696 * If the page has buffers, the uptodate buffers are set dirty, to preserve
 697 * dirty-state coherency between the page and the buffers.  It the page does
 698 * not have buffers then when they are later attached they will all be set
 699 * dirty.
 700 *
 701 * The buffers are dirtied before the page is dirtied.  There's a small race
 702 * window in which a writepage caller may see the page cleanness but not the
 703 * buffer dirtiness.  That's fine.  If this code were to set the page dirty
 704 * before the buffers, a concurrent writepage caller could clear the page dirty
 705 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
 706 * page on the dirty page list.
 707 *
 708 * We use i_private_lock to lock against try_to_free_buffers while using the
 709 * page's buffer list.  Also use this to protect against clean buffers being
 710 * added to the page after it was set dirty.
 711 *
 712 * FIXME: may need to call ->reservepage here as well.  That's rather up to the
 713 * address_space though.
 714 */
 715bool block_dirty_folio(struct address_space *mapping, struct folio *folio)
 716{
 717	struct buffer_head *head;
 718	bool newly_dirty;
 719
 720	spin_lock(&mapping->i_private_lock);
 721	head = folio_buffers(folio);
 722	if (head) {
 
 
 
 723		struct buffer_head *bh = head;
 724
 725		do {
 726			set_buffer_dirty(bh);
 727			bh = bh->b_this_page;
 728		} while (bh != head);
 729	}
 730	/*
 731	 * Lock out page's memcg migration to keep PageDirty
 732	 * synchronized with per-memcg dirty page counters.
 733	 */
 734	folio_memcg_lock(folio);
 735	newly_dirty = !folio_test_set_dirty(folio);
 736	spin_unlock(&mapping->i_private_lock);
 737
 738	if (newly_dirty)
 739		__folio_mark_dirty(folio, mapping, 1);
 740
 741	folio_memcg_unlock(folio);
 742
 743	if (newly_dirty)
 744		__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
 745
 746	return newly_dirty;
 747}
 748EXPORT_SYMBOL(block_dirty_folio);
 749
 750/*
 751 * Write out and wait upon a list of buffers.
 752 *
 753 * We have conflicting pressures: we want to make sure that all
 754 * initially dirty buffers get waited on, but that any subsequently
 755 * dirtied buffers don't.  After all, we don't want fsync to last
 756 * forever if somebody is actively writing to the file.
 757 *
 758 * Do this in two main stages: first we copy dirty buffers to a
 759 * temporary inode list, queueing the writes as we go.  Then we clean
 760 * up, waiting for those writes to complete.
 761 * 
 762 * During this second stage, any subsequent updates to the file may end
 763 * up refiling the buffer on the original inode's dirty list again, so
 764 * there is a chance we will end up with a buffer queued for write but
 765 * not yet completed on that list.  So, as a final cleanup we go through
 766 * the osync code to catch these locked, dirty buffers without requeuing
 767 * any newly dirty buffers for write.
 768 */
 769static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
 770{
 771	struct buffer_head *bh;
 772	struct list_head tmp;
 773	struct address_space *mapping;
 774	int err = 0, err2;
 775	struct blk_plug plug;
 776
 777	INIT_LIST_HEAD(&tmp);
 778	blk_start_plug(&plug);
 779
 780	spin_lock(lock);
 781	while (!list_empty(list)) {
 782		bh = BH_ENTRY(list->next);
 783		mapping = bh->b_assoc_map;
 784		__remove_assoc_queue(bh);
 785		/* Avoid race with mark_buffer_dirty_inode() which does
 786		 * a lockless check and we rely on seeing the dirty bit */
 787		smp_mb();
 788		if (buffer_dirty(bh) || buffer_locked(bh)) {
 789			list_add(&bh->b_assoc_buffers, &tmp);
 790			bh->b_assoc_map = mapping;
 791			if (buffer_dirty(bh)) {
 792				get_bh(bh);
 793				spin_unlock(lock);
 794				/*
 795				 * Ensure any pending I/O completes so that
 796				 * write_dirty_buffer() actually writes the
 797				 * current contents - it is a noop if I/O is
 798				 * still in flight on potentially older
 799				 * contents.
 800				 */
 801				write_dirty_buffer(bh, REQ_SYNC);
 802
 803				/*
 804				 * Kick off IO for the previous mapping. Note
 805				 * that we will not run the very last mapping,
 806				 * wait_on_buffer() will do that for us
 807				 * through sync_buffer().
 808				 */
 809				brelse(bh);
 810				spin_lock(lock);
 811			}
 812		}
 813	}
 814
 815	spin_unlock(lock);
 816	blk_finish_plug(&plug);
 817	spin_lock(lock);
 818
 819	while (!list_empty(&tmp)) {
 820		bh = BH_ENTRY(tmp.prev);
 821		get_bh(bh);
 822		mapping = bh->b_assoc_map;
 823		__remove_assoc_queue(bh);
 824		/* Avoid race with mark_buffer_dirty_inode() which does
 825		 * a lockless check and we rely on seeing the dirty bit */
 826		smp_mb();
 827		if (buffer_dirty(bh)) {
 828			list_add(&bh->b_assoc_buffers,
 829				 &mapping->i_private_list);
 830			bh->b_assoc_map = mapping;
 831		}
 832		spin_unlock(lock);
 833		wait_on_buffer(bh);
 834		if (!buffer_uptodate(bh))
 835			err = -EIO;
 836		brelse(bh);
 837		spin_lock(lock);
 838	}
 839	
 840	spin_unlock(lock);
 841	err2 = osync_buffers_list(lock, list);
 842	if (err)
 843		return err;
 844	else
 845		return err2;
 846}
 847
 848/*
 849 * Invalidate any and all dirty buffers on a given inode.  We are
 850 * probably unmounting the fs, but that doesn't mean we have already
 851 * done a sync().  Just drop the buffers from the inode list.
 852 *
 853 * NOTE: we take the inode's blockdev's mapping's i_private_lock.  Which
 854 * assumes that all the buffers are against the blockdev.  Not true
 855 * for reiserfs.
 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				       bool retry)
 958{
 959	gfp_t gfp = GFP_NOFS | __GFP_ACCOUNT;
 960	if (retry)
 961		gfp |= __GFP_NOFAIL;
 962
 963	return folio_alloc_buffers(page_folio(page), size, gfp);
 964}
 965EXPORT_SYMBOL_GPL(alloc_page_buffers);
 966
 967static inline void link_dev_buffers(struct folio *folio,
 968		struct buffer_head *head)
 969{
 970	struct buffer_head *bh, *tail;
 971
 972	bh = head;
 973	do {
 974		tail = bh;
 975		bh = bh->b_this_page;
 976	} while (bh);
 977	tail->b_this_page = head;
 978	folio_attach_private(folio, head);
 979}
 980
 981static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
 982{
 983	sector_t retval = ~((sector_t)0);
 984	loff_t sz = bdev_nr_bytes(bdev);
 985
 986	if (sz) {
 987		unsigned int sizebits = blksize_bits(size);
 988		retval = (sz >> sizebits);
 989	}
 990	return retval;
 991}
 992
 993/*
 994 * Initialise the state of a blockdev folio's buffers.
 995 */ 
 996static sector_t folio_init_buffers(struct folio *folio,
 997		struct block_device *bdev, unsigned size)
 
 998{
 999	struct buffer_head *head = folio_buffers(folio);
1000	struct buffer_head *bh = head;
1001	bool uptodate = folio_test_uptodate(folio);
1002	sector_t block = div_u64(folio_pos(folio), size);
1003	sector_t end_block = blkdev_max_block(bdev, size);
1004
1005	do {
1006		if (!buffer_mapped(bh)) {
1007			bh->b_end_io = NULL;
1008			bh->b_private = NULL;
1009			bh->b_bdev = bdev;
1010			bh->b_blocknr = block;
1011			if (uptodate)
1012				set_buffer_uptodate(bh);
1013			if (block < end_block)
1014				set_buffer_mapped(bh);
1015		}
1016		block++;
1017		bh = bh->b_this_page;
1018	} while (bh != head);
1019
1020	/*
1021	 * Caller needs to validate requested block against end of device.
1022	 */
1023	return end_block;
1024}
1025
1026/*
1027 * Create the page-cache folio that contains the requested block.
1028 *
1029 * This is used purely for blockdev mappings.
1030 *
1031 * Returns false if we have a failure which cannot be cured by retrying
1032 * without sleeping.  Returns true if we succeeded, or the caller should retry.
1033 */
1034static bool grow_dev_folio(struct block_device *bdev, sector_t block,
1035		pgoff_t index, unsigned size, gfp_t gfp)
 
1036{
1037	struct inode *inode = bdev->bd_inode;
1038	struct folio *folio;
1039	struct buffer_head *bh;
1040	sector_t end_block = 0;
 
 
1041
1042	folio = __filemap_get_folio(inode->i_mapping, index,
1043			FGP_LOCK | FGP_ACCESSED | FGP_CREAT, gfp);
1044	if (IS_ERR(folio))
1045		return false;
1046
1047	bh = folio_buffers(folio);
1048	if (bh) {
1049		if (bh->b_size == size) {
1050			end_block = folio_init_buffers(folio, bdev, size);
1051			goto unlock;
1052		}
 
1053
1054		/*
1055		 * Retrying may succeed; for example the folio may finish
1056		 * writeback, or buffers may be cleaned.  This should not
1057		 * happen very often; maybe we have old buffers attached to
1058		 * this blockdev's page cache and we're trying to change
1059		 * the block size?
1060		 */
1061		if (!try_to_free_buffers(folio)) {
1062			end_block = ~0ULL;
1063			goto unlock;
 
1064		}
 
 
1065	}
1066
1067	bh = folio_alloc_buffers(folio, size, gfp | __GFP_ACCOUNT);
1068	if (!bh)
1069		goto unlock;
 
1070
1071	/*
1072	 * Link the folio to the buffers and initialise them.  Take the
1073	 * lock to be atomic wrt __find_get_block(), which does not
1074	 * run under the folio lock.
1075	 */
1076	spin_lock(&inode->i_mapping->i_private_lock);
1077	link_dev_buffers(folio, bh);
1078	end_block = folio_init_buffers(folio, bdev, size);
1079	spin_unlock(&inode->i_mapping->i_private_lock);
1080unlock:
1081	folio_unlock(folio);
1082	folio_put(folio);
1083	return block < end_block;
 
 
 
1084}
1085
1086/*
1087 * Create buffers for the specified block device block's folio.  If
1088 * that folio was dirty, the buffers are set dirty also.  Returns false
1089 * if we've hit a permanent error.
1090 */
1091static bool grow_buffers(struct block_device *bdev, sector_t block,
1092		unsigned size, gfp_t gfp)
1093{
1094	loff_t pos;
 
 
 
 
1095
1096	/*
1097	 * Check for a block which lies outside our maximum possible
1098	 * pagecache index.
1099	 */
1100	if (check_mul_overflow(block, (sector_t)size, &pos) || pos > MAX_LFS_FILESIZE) {
1101		printk(KERN_ERR "%s: requested out-of-range block %llu for device %pg\n",
 
1102			__func__, (unsigned long long)block,
1103			bdev);
1104		return false;
1105	}
1106
1107	/* Create a folio with the proper size buffers */
1108	return grow_dev_folio(bdev, block, pos / PAGE_SIZE, size, gfp);
1109}
1110
1111static struct buffer_head *
1112__getblk_slow(struct block_device *bdev, sector_t block,
1113	     unsigned size, gfp_t gfp)
1114{
1115	/* Size must be multiple of hard sectorsize */
1116	if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
1117			(size < 512 || size > PAGE_SIZE))) {
1118		printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1119					size);
1120		printk(KERN_ERR "logical block size: %d\n",
1121					bdev_logical_block_size(bdev));
1122
1123		dump_stack();
1124		return NULL;
1125	}
1126
1127	for (;;) {
1128		struct buffer_head *bh;
 
1129
1130		bh = __find_get_block(bdev, block, size);
1131		if (bh)
1132			return bh;
1133
1134		if (!grow_buffers(bdev, block, size, gfp))
 
1135			return NULL;
1136	}
1137}
1138
1139/*
1140 * The relationship between dirty buffers and dirty pages:
1141 *
1142 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1143 * the page is tagged dirty in the page cache.
1144 *
1145 * At all times, the dirtiness of the buffers represents the dirtiness of
1146 * subsections of the page.  If the page has buffers, the page dirty bit is
1147 * merely a hint about the true dirty state.
1148 *
1149 * When a page is set dirty in its entirety, all its buffers are marked dirty
1150 * (if the page has buffers).
1151 *
1152 * When a buffer is marked dirty, its page is dirtied, but the page's other
1153 * buffers are not.
1154 *
1155 * Also.  When blockdev buffers are explicitly read with bread(), they
1156 * individually become uptodate.  But their backing page remains not
1157 * uptodate - even if all of its buffers are uptodate.  A subsequent
1158 * block_read_full_folio() against that folio will discover all the uptodate
1159 * buffers, will set the folio uptodate and will perform no I/O.
1160 */
1161
1162/**
1163 * mark_buffer_dirty - mark a buffer_head as needing writeout
1164 * @bh: the buffer_head to mark dirty
1165 *
1166 * mark_buffer_dirty() will set the dirty bit against the buffer, then set
1167 * its backing page dirty, then tag the page as dirty in the page cache
1168 * and then attach the address_space's inode to its superblock's dirty
1169 * inode list.
1170 *
1171 * mark_buffer_dirty() is atomic.  It takes bh->b_folio->mapping->i_private_lock,
1172 * i_pages lock and mapping->host->i_lock.
1173 */
1174void mark_buffer_dirty(struct buffer_head *bh)
1175{
1176	WARN_ON_ONCE(!buffer_uptodate(bh));
1177
1178	trace_block_dirty_buffer(bh);
1179
1180	/*
1181	 * Very *carefully* optimize the it-is-already-dirty case.
1182	 *
1183	 * Don't let the final "is it dirty" escape to before we
1184	 * perhaps modified the buffer.
1185	 */
1186	if (buffer_dirty(bh)) {
1187		smp_mb();
1188		if (buffer_dirty(bh))
1189			return;
1190	}
1191
1192	if (!test_set_buffer_dirty(bh)) {
1193		struct folio *folio = bh->b_folio;
1194		struct address_space *mapping = NULL;
1195
1196		folio_memcg_lock(folio);
1197		if (!folio_test_set_dirty(folio)) {
1198			mapping = folio->mapping;
1199			if (mapping)
1200				__folio_mark_dirty(folio, mapping, 0);
1201		}
1202		folio_memcg_unlock(folio);
1203		if (mapping)
1204			__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
1205	}
1206}
1207EXPORT_SYMBOL(mark_buffer_dirty);
1208
1209void mark_buffer_write_io_error(struct buffer_head *bh)
1210{
 
 
1211	set_buffer_write_io_error(bh);
1212	/* FIXME: do we need to set this in both places? */
1213	if (bh->b_folio && bh->b_folio->mapping)
1214		mapping_set_error(bh->b_folio->mapping, -EIO);
1215	if (bh->b_assoc_map) {
1216		mapping_set_error(bh->b_assoc_map, -EIO);
1217		errseq_set(&bh->b_assoc_map->host->i_sb->s_wb_err, -EIO);
1218	}
 
 
 
1219}
1220EXPORT_SYMBOL(mark_buffer_write_io_error);
1221
1222/*
1223 * Decrement a buffer_head's reference count.  If all buffers against a page
1224 * have zero reference count, are clean and unlocked, and if the page is clean
1225 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1226 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1227 * a page but it ends up not being freed, and buffers may later be reattached).
1228 */
1229void __brelse(struct buffer_head * buf)
1230{
1231	if (atomic_read(&buf->b_count)) {
1232		put_bh(buf);
1233		return;
1234	}
1235	WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1236}
1237EXPORT_SYMBOL(__brelse);
1238
1239/*
1240 * bforget() is like brelse(), except it discards any
1241 * potentially dirty data.
1242 */
1243void __bforget(struct buffer_head *bh)
1244{
1245	clear_buffer_dirty(bh);
1246	if (bh->b_assoc_map) {
1247		struct address_space *buffer_mapping = bh->b_folio->mapping;
1248
1249		spin_lock(&buffer_mapping->i_private_lock);
1250		list_del_init(&bh->b_assoc_buffers);
1251		bh->b_assoc_map = NULL;
1252		spin_unlock(&buffer_mapping->i_private_lock);
1253	}
1254	__brelse(bh);
1255}
1256EXPORT_SYMBOL(__bforget);
1257
1258static struct buffer_head *__bread_slow(struct buffer_head *bh)
1259{
1260	lock_buffer(bh);
1261	if (buffer_uptodate(bh)) {
1262		unlock_buffer(bh);
1263		return bh;
1264	} else {
1265		get_bh(bh);
1266		bh->b_end_io = end_buffer_read_sync;
1267		submit_bh(REQ_OP_READ, bh);
1268		wait_on_buffer(bh);
1269		if (buffer_uptodate(bh))
1270			return bh;
1271	}
1272	brelse(bh);
1273	return NULL;
1274}
1275
1276/*
1277 * Per-cpu buffer LRU implementation.  To reduce the cost of __find_get_block().
1278 * The bhs[] array is sorted - newest buffer is at bhs[0].  Buffers have their
1279 * refcount elevated by one when they're in an LRU.  A buffer can only appear
1280 * once in a particular CPU's LRU.  A single buffer can be present in multiple
1281 * CPU's LRUs at the same time.
1282 *
1283 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1284 * sb_find_get_block().
1285 *
1286 * The LRUs themselves only need locking against invalidate_bh_lrus.  We use
1287 * a local interrupt disable for that.
1288 */
1289
1290#define BH_LRU_SIZE	16
1291
1292struct bh_lru {
1293	struct buffer_head *bhs[BH_LRU_SIZE];
1294};
1295
1296static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1297
1298#ifdef CONFIG_SMP
1299#define bh_lru_lock()	local_irq_disable()
1300#define bh_lru_unlock()	local_irq_enable()
1301#else
1302#define bh_lru_lock()	preempt_disable()
1303#define bh_lru_unlock()	preempt_enable()
1304#endif
1305
1306static inline void check_irqs_on(void)
1307{
1308#ifdef irqs_disabled
1309	BUG_ON(irqs_disabled());
1310#endif
1311}
1312
1313/*
1314 * Install a buffer_head into this cpu's LRU.  If not already in the LRU, it is
1315 * inserted at the front, and the buffer_head at the back if any is evicted.
1316 * Or, if already in the LRU it is moved to the front.
1317 */
1318static void bh_lru_install(struct buffer_head *bh)
1319{
1320	struct buffer_head *evictee = bh;
1321	struct bh_lru *b;
1322	int i;
1323
1324	check_irqs_on();
1325	bh_lru_lock();
1326
1327	/*
1328	 * the refcount of buffer_head in bh_lru prevents dropping the
1329	 * attached page(i.e., try_to_free_buffers) so it could cause
1330	 * failing page migration.
1331	 * Skip putting upcoming bh into bh_lru until migration is done.
1332	 */
1333	if (lru_cache_disabled() || cpu_is_isolated(smp_processor_id())) {
1334		bh_lru_unlock();
1335		return;
1336	}
 
1337
1338	b = this_cpu_ptr(&bh_lrus);
1339	for (i = 0; i < BH_LRU_SIZE; i++) {
1340		swap(evictee, b->bhs[i]);
1341		if (evictee == bh) {
1342			bh_lru_unlock();
1343			return;
1344		}
1345	}
1346
1347	get_bh(bh);
1348	bh_lru_unlock();
1349	brelse(evictee);
1350}
1351
1352/*
1353 * Look up the bh in this cpu's LRU.  If it's there, move it to the head.
1354 */
1355static struct buffer_head *
1356lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
1357{
1358	struct buffer_head *ret = NULL;
1359	unsigned int i;
1360
1361	check_irqs_on();
1362	bh_lru_lock();
1363	if (cpu_is_isolated(smp_processor_id())) {
1364		bh_lru_unlock();
1365		return NULL;
1366	}
1367	for (i = 0; i < BH_LRU_SIZE; i++) {
1368		struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
1369
1370		if (bh && bh->b_blocknr == block && bh->b_bdev == bdev &&
1371		    bh->b_size == size) {
1372			if (i) {
1373				while (i) {
1374					__this_cpu_write(bh_lrus.bhs[i],
1375						__this_cpu_read(bh_lrus.bhs[i - 1]));
1376					i--;
1377				}
1378				__this_cpu_write(bh_lrus.bhs[0], bh);
1379			}
1380			get_bh(bh);
1381			ret = bh;
1382			break;
1383		}
1384	}
1385	bh_lru_unlock();
1386	return ret;
1387}
1388
1389/*
1390 * Perform a pagecache lookup for the matching buffer.  If it's there, refresh
1391 * it in the LRU and mark it as accessed.  If it is not present then return
1392 * NULL
1393 */
1394struct buffer_head *
1395__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
1396{
1397	struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1398
1399	if (bh == NULL) {
1400		/* __find_get_block_slow will mark the page accessed */
1401		bh = __find_get_block_slow(bdev, block);
1402		if (bh)
1403			bh_lru_install(bh);
1404	} else
1405		touch_buffer(bh);
1406
1407	return bh;
1408}
1409EXPORT_SYMBOL(__find_get_block);
1410
1411/**
1412 * bdev_getblk - Get a buffer_head in a block device's buffer cache.
1413 * @bdev: The block device.
1414 * @block: The block number.
1415 * @size: The size of buffer_heads for this @bdev.
1416 * @gfp: The memory allocation flags to use.
1417 *
1418 * Return: The buffer head, or NULL if memory could not be allocated.
 
1419 */
1420struct buffer_head *bdev_getblk(struct block_device *bdev, sector_t block,
1421		unsigned size, gfp_t gfp)
 
1422{
1423	struct buffer_head *bh = __find_get_block(bdev, block, size);
1424
1425	might_alloc(gfp);
1426	if (bh)
1427		return bh;
1428
1429	return __getblk_slow(bdev, block, size, gfp);
1430}
1431EXPORT_SYMBOL(bdev_getblk);
1432
1433/*
1434 * Do async read-ahead on a buffer..
1435 */
1436void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
1437{
1438	struct buffer_head *bh = bdev_getblk(bdev, block, size,
1439			GFP_NOWAIT | __GFP_MOVABLE);
1440
1441	if (likely(bh)) {
1442		bh_readahead(bh, REQ_RAHEAD);
1443		brelse(bh);
1444	}
1445}
1446EXPORT_SYMBOL(__breadahead);
1447
 
 
 
 
 
 
 
 
 
 
 
1448/**
1449 *  __bread_gfp() - reads a specified block and returns the bh
1450 *  @bdev: the block_device to read from
1451 *  @block: number of block
1452 *  @size: size (in bytes) to read
1453 *  @gfp: page allocation flag
1454 *
1455 *  Reads a specified block, and returns buffer head that contains it.
1456 *  The page cache can be allocated from non-movable area
1457 *  not to prevent page migration if you set gfp to zero.
1458 *  It returns NULL if the block was unreadable.
1459 */
1460struct buffer_head *
1461__bread_gfp(struct block_device *bdev, sector_t block,
1462		   unsigned size, gfp_t gfp)
1463{
1464	struct buffer_head *bh;
1465
1466	gfp |= mapping_gfp_constraint(bdev->bd_inode->i_mapping, ~__GFP_FS);
1467
1468	/*
1469	 * Prefer looping in the allocator rather than here, at least that
1470	 * code knows what it's doing.
1471	 */
1472	gfp |= __GFP_NOFAIL;
1473
1474	bh = bdev_getblk(bdev, block, size, gfp);
1475
1476	if (likely(bh) && !buffer_uptodate(bh))
1477		bh = __bread_slow(bh);
1478	return bh;
1479}
1480EXPORT_SYMBOL(__bread_gfp);
1481
1482static void __invalidate_bh_lrus(struct bh_lru *b)
1483{
1484	int i;
1485
1486	for (i = 0; i < BH_LRU_SIZE; i++) {
1487		brelse(b->bhs[i]);
1488		b->bhs[i] = NULL;
1489	}
1490}
1491/*
1492 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1493 * This doesn't race because it runs in each cpu either in irq
1494 * or with preempt disabled.
1495 */
1496static void invalidate_bh_lru(void *arg)
1497{
1498	struct bh_lru *b = &get_cpu_var(bh_lrus);
1499
1500	__invalidate_bh_lrus(b);
1501	put_cpu_var(bh_lrus);
1502}
1503
1504bool has_bh_in_lru(int cpu, void *dummy)
1505{
1506	struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
1507	int i;
1508	
1509	for (i = 0; i < BH_LRU_SIZE; i++) {
1510		if (b->bhs[i])
1511			return true;
1512	}
1513
1514	return false;
1515}
1516
1517void invalidate_bh_lrus(void)
1518{
1519	on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1);
1520}
1521EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
1522
1523/*
1524 * It's called from workqueue context so we need a bh_lru_lock to close
1525 * the race with preemption/irq.
1526 */
1527void invalidate_bh_lrus_cpu(void)
1528{
1529	struct bh_lru *b;
1530
1531	bh_lru_lock();
1532	b = this_cpu_ptr(&bh_lrus);
1533	__invalidate_bh_lrus(b);
1534	bh_lru_unlock();
1535}
1536
1537void folio_set_bh(struct buffer_head *bh, struct folio *folio,
1538		  unsigned long offset)
1539{
1540	bh->b_folio = folio;
1541	BUG_ON(offset >= folio_size(folio));
1542	if (folio_test_highmem(folio))
1543		/*
1544		 * This catches illegal uses and preserves the offset:
1545		 */
1546		bh->b_data = (char *)(0 + offset);
1547	else
1548		bh->b_data = folio_address(folio) + offset;
1549}
1550EXPORT_SYMBOL(folio_set_bh);
1551
1552/*
1553 * Called when truncating a buffer on a page completely.
1554 */
1555
1556/* Bits that are cleared during an invalidate */
1557#define BUFFER_FLAGS_DISCARD \
1558	(1 << BH_Mapped | 1 << BH_New | 1 << BH_Req | \
1559	 1 << BH_Delay | 1 << BH_Unwritten)
1560
1561static void discard_buffer(struct buffer_head * bh)
1562{
1563	unsigned long b_state;
1564
1565	lock_buffer(bh);
1566	clear_buffer_dirty(bh);
1567	bh->b_bdev = NULL;
1568	b_state = READ_ONCE(bh->b_state);
1569	do {
1570	} while (!try_cmpxchg(&bh->b_state, &b_state,
1571			      b_state & ~BUFFER_FLAGS_DISCARD));
 
 
 
 
1572	unlock_buffer(bh);
1573}
1574
1575/**
1576 * block_invalidate_folio - Invalidate part or all of a buffer-backed folio.
1577 * @folio: The folio which is affected.
 
1578 * @offset: start of the range to invalidate
1579 * @length: length of the range to invalidate
1580 *
1581 * block_invalidate_folio() is called when all or part of the folio has been
1582 * invalidated by a truncate operation.
1583 *
1584 * block_invalidate_folio() does not have to release all buffers, but it must
1585 * ensure that no dirty buffer is left outside @offset and that no I/O
1586 * is underway against any of the blocks which are outside the truncation
1587 * point.  Because the caller is about to free (and possibly reuse) those
1588 * blocks on-disk.
1589 */
1590void block_invalidate_folio(struct folio *folio, size_t offset, size_t length)
 
1591{
1592	struct buffer_head *head, *bh, *next;
1593	size_t curr_off = 0;
1594	size_t stop = length + offset;
1595
1596	BUG_ON(!folio_test_locked(folio));
 
 
1597
1598	/*
1599	 * Check for overflow
1600	 */
1601	BUG_ON(stop > folio_size(folio) || stop < length);
1602
1603	head = folio_buffers(folio);
1604	if (!head)
1605		return;
1606
 
1607	bh = head;
1608	do {
1609		size_t next_off = curr_off + bh->b_size;
1610		next = bh->b_this_page;
1611
1612		/*
1613		 * Are we still fully in range ?
1614		 */
1615		if (next_off > stop)
1616			goto out;
1617
1618		/*
1619		 * is this block fully invalidated?
1620		 */
1621		if (offset <= curr_off)
1622			discard_buffer(bh);
1623		curr_off = next_off;
1624		bh = next;
1625	} while (bh != head);
1626
1627	/*
1628	 * We release buffers only if the entire folio is being invalidated.
1629	 * The get_block cached value has been unconditionally invalidated,
1630	 * so real IO is not possible anymore.
1631	 */
1632	if (length == folio_size(folio))
1633		filemap_release_folio(folio, 0);
1634out:
1635	return;
1636}
1637EXPORT_SYMBOL(block_invalidate_folio);
 
1638
1639/*
1640 * We attach and possibly dirty the buffers atomically wrt
1641 * block_dirty_folio() via i_private_lock.  try_to_free_buffers
1642 * is already excluded via the folio lock.
1643 */
1644struct buffer_head *create_empty_buffers(struct folio *folio,
1645		unsigned long blocksize, unsigned long b_state)
1646{
1647	struct buffer_head *bh, *head, *tail;
1648	gfp_t gfp = GFP_NOFS | __GFP_ACCOUNT | __GFP_NOFAIL;
1649
1650	head = folio_alloc_buffers(folio, blocksize, gfp);
1651	bh = head;
1652	do {
1653		bh->b_state |= b_state;
1654		tail = bh;
1655		bh = bh->b_this_page;
1656	} while (bh);
1657	tail->b_this_page = head;
1658
1659	spin_lock(&folio->mapping->i_private_lock);
1660	if (folio_test_uptodate(folio) || folio_test_dirty(folio)) {
1661		bh = head;
1662		do {
1663			if (folio_test_dirty(folio))
1664				set_buffer_dirty(bh);
1665			if (folio_test_uptodate(folio))
1666				set_buffer_uptodate(bh);
1667			bh = bh->b_this_page;
1668		} while (bh != head);
1669	}
1670	folio_attach_private(folio, head);
1671	spin_unlock(&folio->mapping->i_private_lock);
1672
1673	return head;
1674}
1675EXPORT_SYMBOL(create_empty_buffers);
1676
1677/**
1678 * clean_bdev_aliases: clean a range of buffers in block device
1679 * @bdev: Block device to clean buffers in
1680 * @block: Start of a range of blocks to clean
1681 * @len: Number of blocks to clean
1682 *
1683 * We are taking a range of blocks for data and we don't want writeback of any
1684 * buffer-cache aliases starting from return from this function and until the
1685 * moment when something will explicitly mark the buffer dirty (hopefully that
1686 * will not happen until we will free that block ;-) We don't even need to mark
1687 * it not-uptodate - nobody can expect anything from a newly allocated buffer
1688 * anyway. We used to use unmap_buffer() for such invalidation, but that was
1689 * wrong. We definitely don't want to mark the alias unmapped, for example - it
1690 * would confuse anyone who might pick it with bread() afterwards...
1691 *
1692 * Also..  Note that bforget() doesn't lock the buffer.  So there can be
1693 * writeout I/O going on against recently-freed buffers.  We don't wait on that
1694 * I/O in bforget() - it's more efficient to wait on the I/O only if we really
1695 * need to.  That happens here.
1696 */
1697void clean_bdev_aliases(struct block_device *bdev, sector_t block, sector_t len)
1698{
1699	struct inode *bd_inode = bdev->bd_inode;
1700	struct address_space *bd_mapping = bd_inode->i_mapping;
1701	struct folio_batch fbatch;
1702	pgoff_t index = ((loff_t)block << bd_inode->i_blkbits) / PAGE_SIZE;
1703	pgoff_t end;
1704	int i, count;
1705	struct buffer_head *bh;
1706	struct buffer_head *head;
1707
1708	end = ((loff_t)(block + len - 1) << bd_inode->i_blkbits) / PAGE_SIZE;
1709	folio_batch_init(&fbatch);
1710	while (filemap_get_folios(bd_mapping, &index, end, &fbatch)) {
1711		count = folio_batch_count(&fbatch);
1712		for (i = 0; i < count; i++) {
1713			struct folio *folio = fbatch.folios[i];
1714
1715			if (!folio_buffers(folio))
1716				continue;
1717			/*
1718			 * We use folio lock instead of bd_mapping->i_private_lock
1719			 * to pin buffers here since we can afford to sleep and
1720			 * it scales better than a global spinlock lock.
1721			 */
1722			folio_lock(folio);
1723			/* Recheck when the folio is locked which pins bhs */
1724			head = folio_buffers(folio);
1725			if (!head)
1726				goto unlock_page;
 
1727			bh = head;
1728			do {
1729				if (!buffer_mapped(bh) || (bh->b_blocknr < block))
1730					goto next;
1731				if (bh->b_blocknr >= block + len)
1732					break;
1733				clear_buffer_dirty(bh);
1734				wait_on_buffer(bh);
1735				clear_buffer_req(bh);
1736next:
1737				bh = bh->b_this_page;
1738			} while (bh != head);
1739unlock_page:
1740			folio_unlock(folio);
1741		}
1742		folio_batch_release(&fbatch);
1743		cond_resched();
1744		/* End of range already reached? */
1745		if (index > end || !index)
1746			break;
1747	}
1748}
1749EXPORT_SYMBOL(clean_bdev_aliases);
1750
1751static struct buffer_head *folio_create_buffers(struct folio *folio,
1752						struct inode *inode,
1753						unsigned int b_state)
 
 
 
 
 
 
1754{
1755	struct buffer_head *bh;
 
1756
1757	BUG_ON(!folio_test_locked(folio));
 
 
1758
1759	bh = folio_buffers(folio);
1760	if (!bh)
1761		bh = create_empty_buffers(folio,
1762				1 << READ_ONCE(inode->i_blkbits), b_state);
1763	return bh;
1764}
1765
1766/*
1767 * NOTE! All mapped/uptodate combinations are valid:
1768 *
1769 *	Mapped	Uptodate	Meaning
1770 *
1771 *	No	No		"unknown" - must do get_block()
1772 *	No	Yes		"hole" - zero-filled
1773 *	Yes	No		"allocated" - allocated on disk, not read in
1774 *	Yes	Yes		"valid" - allocated and up-to-date in memory.
1775 *
1776 * "Dirty" is valid only with the last case (mapped+uptodate).
1777 */
1778
1779/*
1780 * While block_write_full_folio is writing back the dirty buffers under
1781 * the page lock, whoever dirtied the buffers may decide to clean them
1782 * again at any time.  We handle that by only looking at the buffer
1783 * state inside lock_buffer().
1784 *
1785 * If block_write_full_folio() is called for regular writeback
1786 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1787 * locked buffer.   This only can happen if someone has written the buffer
1788 * directly, with submit_bh().  At the address_space level PageWriteback
1789 * prevents this contention from occurring.
1790 *
1791 * If block_write_full_folio() is called with wbc->sync_mode ==
1792 * WB_SYNC_ALL, the writes are posted using REQ_SYNC; this
1793 * causes the writes to be flagged as synchronous writes.
1794 */
1795int __block_write_full_folio(struct inode *inode, struct folio *folio,
1796			get_block_t *get_block, struct writeback_control *wbc)
 
1797{
1798	int err;
1799	sector_t block;
1800	sector_t last_block;
1801	struct buffer_head *bh, *head;
1802	size_t blocksize;
1803	int nr_underway = 0;
1804	blk_opf_t write_flags = wbc_to_write_flags(wbc);
1805
1806	head = folio_create_buffers(folio, inode,
1807				    (1 << BH_Dirty) | (1 << BH_Uptodate));
1808
1809	/*
1810	 * Be very careful.  We have no exclusion from block_dirty_folio
1811	 * here, and the (potentially unmapped) buffers may become dirty at
1812	 * any time.  If a buffer becomes dirty here after we've inspected it
1813	 * then we just miss that fact, and the folio stays dirty.
1814	 *
1815	 * Buffers outside i_size may be dirtied by block_dirty_folio;
1816	 * handle that here by just cleaning them.
1817	 */
1818
1819	bh = head;
1820	blocksize = bh->b_size;
 
1821
1822	block = div_u64(folio_pos(folio), blocksize);
1823	last_block = div_u64(i_size_read(inode) - 1, blocksize);
1824
1825	/*
1826	 * Get all the dirty buffers mapped to disk addresses and
1827	 * handle any aliases from the underlying blockdev's mapping.
1828	 */
1829	do {
1830		if (block > last_block) {
1831			/*
1832			 * mapped buffers outside i_size will occur, because
1833			 * this folio can be outside i_size when there is a
1834			 * truncate in progress.
1835			 */
1836			/*
1837			 * The buffer was zeroed by block_write_full_folio()
1838			 */
1839			clear_buffer_dirty(bh);
1840			set_buffer_uptodate(bh);
1841		} else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1842			   buffer_dirty(bh)) {
1843			WARN_ON(bh->b_size != blocksize);
1844			err = get_block(inode, block, bh, 1);
1845			if (err)
1846				goto recover;
1847			clear_buffer_delay(bh);
1848			if (buffer_new(bh)) {
1849				/* blockdev mappings never come here */
1850				clear_buffer_new(bh);
1851				clean_bdev_bh_alias(bh);
1852			}
1853		}
1854		bh = bh->b_this_page;
1855		block++;
1856	} while (bh != head);
1857
1858	do {
1859		if (!buffer_mapped(bh))
1860			continue;
1861		/*
1862		 * If it's a fully non-blocking write attempt and we cannot
1863		 * lock the buffer then redirty the folio.  Note that this can
1864		 * potentially cause a busy-wait loop from writeback threads
1865		 * and kswapd activity, but those code paths have their own
1866		 * higher-level throttling.
1867		 */
1868		if (wbc->sync_mode != WB_SYNC_NONE) {
1869			lock_buffer(bh);
1870		} else if (!trylock_buffer(bh)) {
1871			folio_redirty_for_writepage(wbc, folio);
1872			continue;
1873		}
1874		if (test_clear_buffer_dirty(bh)) {
1875			mark_buffer_async_write_endio(bh,
1876				end_buffer_async_write);
1877		} else {
1878			unlock_buffer(bh);
1879		}
1880	} while ((bh = bh->b_this_page) != head);
1881
1882	/*
1883	 * The folio and its buffers are protected by the writeback flag,
1884	 * so we can drop the bh refcounts early.
1885	 */
1886	BUG_ON(folio_test_writeback(folio));
1887	folio_start_writeback(folio);
1888
1889	do {
1890		struct buffer_head *next = bh->b_this_page;
1891		if (buffer_async_write(bh)) {
1892			submit_bh_wbc(REQ_OP_WRITE | write_flags, bh,
1893				      inode->i_write_hint, wbc);
1894			nr_underway++;
1895		}
1896		bh = next;
1897	} while (bh != head);
1898	folio_unlock(folio);
1899
1900	err = 0;
1901done:
1902	if (nr_underway == 0) {
1903		/*
1904		 * The folio was marked dirty, but the buffers were
1905		 * clean.  Someone wrote them back by hand with
1906		 * write_dirty_buffer/submit_bh.  A rare case.
1907		 */
1908		folio_end_writeback(folio);
1909
1910		/*
1911		 * The folio and buffer_heads can be released at any time from
1912		 * here on.
1913		 */
1914	}
1915	return err;
1916
1917recover:
1918	/*
1919	 * ENOSPC, or some other error.  We may already have added some
1920	 * blocks to the file, so we need to write these out to avoid
1921	 * exposing stale data.
1922	 * The folio is currently locked and not marked for writeback
1923	 */
1924	bh = head;
1925	/* Recovery: lock and submit the mapped buffers */
1926	do {
1927		if (buffer_mapped(bh) && buffer_dirty(bh) &&
1928		    !buffer_delay(bh)) {
1929			lock_buffer(bh);
1930			mark_buffer_async_write_endio(bh,
1931				end_buffer_async_write);
1932		} else {
1933			/*
1934			 * The buffer may have been set dirty during
1935			 * attachment to a dirty folio.
1936			 */
1937			clear_buffer_dirty(bh);
1938		}
1939	} while ((bh = bh->b_this_page) != head);
1940	folio_set_error(folio);
1941	BUG_ON(folio_test_writeback(folio));
1942	mapping_set_error(folio->mapping, err);
1943	folio_start_writeback(folio);
1944	do {
1945		struct buffer_head *next = bh->b_this_page;
1946		if (buffer_async_write(bh)) {
1947			clear_buffer_dirty(bh);
1948			submit_bh_wbc(REQ_OP_WRITE | write_flags, bh,
1949				      inode->i_write_hint, wbc);
1950			nr_underway++;
1951		}
1952		bh = next;
1953	} while (bh != head);
1954	folio_unlock(folio);
1955	goto done;
1956}
1957EXPORT_SYMBOL(__block_write_full_folio);
1958
1959/*
1960 * If a folio has any new buffers, zero them out here, and mark them uptodate
1961 * and dirty so they'll be written out (in order to prevent uninitialised
1962 * block data from leaking). And clear the new bit.
1963 */
1964void folio_zero_new_buffers(struct folio *folio, size_t from, size_t to)
1965{
1966	size_t block_start, block_end;
1967	struct buffer_head *head, *bh;
1968
1969	BUG_ON(!folio_test_locked(folio));
1970	head = folio_buffers(folio);
1971	if (!head)
1972		return;
1973
1974	bh = head;
1975	block_start = 0;
1976	do {
1977		block_end = block_start + bh->b_size;
1978
1979		if (buffer_new(bh)) {
1980			if (block_end > from && block_start < to) {
1981				if (!folio_test_uptodate(folio)) {
1982					size_t start, xend;
1983
1984					start = max(from, block_start);
1985					xend = min(to, block_end);
1986
1987					folio_zero_segment(folio, start, xend);
1988					set_buffer_uptodate(bh);
1989				}
1990
1991				clear_buffer_new(bh);
1992				mark_buffer_dirty(bh);
1993			}
1994		}
1995
1996		block_start = block_end;
1997		bh = bh->b_this_page;
1998	} while (bh != head);
1999}
2000EXPORT_SYMBOL(folio_zero_new_buffers);
2001
2002static int
2003iomap_to_bh(struct inode *inode, sector_t block, struct buffer_head *bh,
2004		const struct iomap *iomap)
2005{
2006	loff_t offset = (loff_t)block << inode->i_blkbits;
2007
2008	bh->b_bdev = iomap->bdev;
2009
2010	/*
2011	 * Block points to offset in file we need to map, iomap contains
2012	 * the offset at which the map starts. If the map ends before the
2013	 * current block, then do not map the buffer and let the caller
2014	 * handle it.
2015	 */
2016	if (offset >= iomap->offset + iomap->length)
2017		return -EIO;
2018
2019	switch (iomap->type) {
2020	case IOMAP_HOLE:
2021		/*
2022		 * If the buffer is not up to date or beyond the current EOF,
2023		 * we need to mark it as new to ensure sub-block zeroing is
2024		 * executed if necessary.
2025		 */
2026		if (!buffer_uptodate(bh) ||
2027		    (offset >= i_size_read(inode)))
2028			set_buffer_new(bh);
2029		return 0;
2030	case IOMAP_DELALLOC:
2031		if (!buffer_uptodate(bh) ||
2032		    (offset >= i_size_read(inode)))
2033			set_buffer_new(bh);
2034		set_buffer_uptodate(bh);
2035		set_buffer_mapped(bh);
2036		set_buffer_delay(bh);
2037		return 0;
2038	case IOMAP_UNWRITTEN:
2039		/*
2040		 * For unwritten regions, we always need to ensure that regions
2041		 * in the block we are not writing to are zeroed. Mark the
2042		 * buffer as new to ensure this.
2043		 */
2044		set_buffer_new(bh);
2045		set_buffer_unwritten(bh);
2046		fallthrough;
2047	case IOMAP_MAPPED:
2048		if ((iomap->flags & IOMAP_F_NEW) ||
2049		    offset >= i_size_read(inode)) {
2050			/*
2051			 * This can happen if truncating the block device races
2052			 * with the check in the caller as i_size updates on
2053			 * block devices aren't synchronized by i_rwsem for
2054			 * block devices.
2055			 */
2056			if (S_ISBLK(inode->i_mode))
2057				return -EIO;
2058			set_buffer_new(bh);
2059		}
2060		bh->b_blocknr = (iomap->addr + offset - iomap->offset) >>
2061				inode->i_blkbits;
2062		set_buffer_mapped(bh);
2063		return 0;
2064	default:
2065		WARN_ON_ONCE(1);
2066		return -EIO;
2067	}
2068}
2069
2070int __block_write_begin_int(struct folio *folio, loff_t pos, unsigned len,
2071		get_block_t *get_block, const struct iomap *iomap)
2072{
2073	size_t from = offset_in_folio(folio, pos);
2074	size_t to = from + len;
2075	struct inode *inode = folio->mapping->host;
2076	size_t block_start, block_end;
2077	sector_t block;
2078	int err = 0;
2079	size_t blocksize;
2080	struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
2081
2082	BUG_ON(!folio_test_locked(folio));
2083	BUG_ON(to > folio_size(folio));
 
2084	BUG_ON(from > to);
2085
2086	head = folio_create_buffers(folio, inode, 0);
2087	blocksize = head->b_size;
2088	block = div_u64(folio_pos(folio), blocksize);
2089
2090	for (bh = head, block_start = 0; bh != head || !block_start;
 
 
2091	    block++, block_start=block_end, bh = bh->b_this_page) {
2092		block_end = block_start + blocksize;
2093		if (block_end <= from || block_start >= to) {
2094			if (folio_test_uptodate(folio)) {
2095				if (!buffer_uptodate(bh))
2096					set_buffer_uptodate(bh);
2097			}
2098			continue;
2099		}
2100		if (buffer_new(bh))
2101			clear_buffer_new(bh);
2102		if (!buffer_mapped(bh)) {
2103			WARN_ON(bh->b_size != blocksize);
2104			if (get_block)
2105				err = get_block(inode, block, bh, 1);
2106			else
2107				err = iomap_to_bh(inode, block, bh, iomap);
2108			if (err)
2109				break;
 
2110
2111			if (buffer_new(bh)) {
2112				clean_bdev_bh_alias(bh);
2113				if (folio_test_uptodate(folio)) {
2114					clear_buffer_new(bh);
2115					set_buffer_uptodate(bh);
2116					mark_buffer_dirty(bh);
2117					continue;
2118				}
2119				if (block_end > to || block_start < from)
2120					folio_zero_segments(folio,
2121						to, block_end,
2122						block_start, from);
2123				continue;
2124			}
2125		}
2126		if (folio_test_uptodate(folio)) {
2127			if (!buffer_uptodate(bh))
2128				set_buffer_uptodate(bh);
2129			continue; 
2130		}
2131		if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
2132		    !buffer_unwritten(bh) &&
2133		     (block_start < from || block_end > to)) {
2134			bh_read_nowait(bh, 0);
2135			*wait_bh++=bh;
2136		}
2137	}
2138	/*
2139	 * If we issued read requests - let them complete.
2140	 */
2141	while(wait_bh > wait) {
2142		wait_on_buffer(*--wait_bh);
2143		if (!buffer_uptodate(*wait_bh))
2144			err = -EIO;
2145	}
2146	if (unlikely(err))
2147		folio_zero_new_buffers(folio, from, to);
2148	return err;
2149}
2150
2151int __block_write_begin(struct page *page, loff_t pos, unsigned len,
2152		get_block_t *get_block)
2153{
2154	return __block_write_begin_int(page_folio(page), pos, len, get_block,
2155				       NULL);
2156}
2157EXPORT_SYMBOL(__block_write_begin);
2158
2159static void __block_commit_write(struct folio *folio, size_t from, size_t to)
 
2160{
2161	size_t block_start, block_end;
2162	bool partial = false;
2163	unsigned blocksize;
2164	struct buffer_head *bh, *head;
2165
2166	bh = head = folio_buffers(folio);
2167	blocksize = bh->b_size;
2168
2169	block_start = 0;
2170	do {
2171		block_end = block_start + blocksize;
2172		if (block_end <= from || block_start >= to) {
2173			if (!buffer_uptodate(bh))
2174				partial = true;
2175		} else {
2176			set_buffer_uptodate(bh);
2177			mark_buffer_dirty(bh);
2178		}
2179		if (buffer_new(bh))
2180			clear_buffer_new(bh);
2181
2182		block_start = block_end;
2183		bh = bh->b_this_page;
2184	} while (bh != head);
2185
2186	/*
2187	 * If this is a partial write which happened to make all buffers
2188	 * uptodate then we can optimize away a bogus read_folio() for
2189	 * the next read(). Here we 'discover' whether the folio went
2190	 * uptodate as a result of this (potentially partial) write.
2191	 */
2192	if (!partial)
2193		folio_mark_uptodate(folio);
 
2194}
2195
2196/*
2197 * block_write_begin takes care of the basic task of block allocation and
2198 * bringing partial write blocks uptodate first.
2199 *
2200 * The filesystem needs to handle block truncation upon failure.
2201 */
2202int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
2203		struct page **pagep, get_block_t *get_block)
2204{
2205	pgoff_t index = pos >> PAGE_SHIFT;
2206	struct page *page;
2207	int status;
2208
2209	page = grab_cache_page_write_begin(mapping, index);
2210	if (!page)
2211		return -ENOMEM;
2212
2213	status = __block_write_begin(page, pos, len, get_block);
2214	if (unlikely(status)) {
2215		unlock_page(page);
2216		put_page(page);
2217		page = NULL;
2218	}
2219
2220	*pagep = page;
2221	return status;
2222}
2223EXPORT_SYMBOL(block_write_begin);
2224
2225int block_write_end(struct file *file, struct address_space *mapping,
2226			loff_t pos, unsigned len, unsigned copied,
2227			struct page *page, void *fsdata)
2228{
2229	struct folio *folio = page_folio(page);
2230	size_t start = pos - folio_pos(folio);
 
 
2231
2232	if (unlikely(copied < len)) {
2233		/*
2234		 * The buffers that were written will now be uptodate, so
2235		 * we don't have to worry about a read_folio reading them
2236		 * and overwriting a partial write. However if we have
2237		 * encountered a short write and only partially written
2238		 * into a buffer, it will not be marked uptodate, so a
2239		 * read_folio might come in and destroy our partial write.
2240		 *
2241		 * Do the simplest thing, and just treat any short write to a
2242		 * non uptodate folio as a zero-length write, and force the
2243		 * caller to redo the whole thing.
2244		 */
2245		if (!folio_test_uptodate(folio))
2246			copied = 0;
2247
2248		folio_zero_new_buffers(folio, start+copied, start+len);
2249	}
2250	flush_dcache_folio(folio);
2251
2252	/* This could be a short (even 0-length) commit */
2253	__block_commit_write(folio, start, start + copied);
2254
2255	return copied;
2256}
2257EXPORT_SYMBOL(block_write_end);
2258
2259int generic_write_end(struct file *file, struct address_space *mapping,
2260			loff_t pos, unsigned len, unsigned copied,
2261			struct page *page, void *fsdata)
2262{
2263	struct inode *inode = mapping->host;
2264	loff_t old_size = inode->i_size;
2265	bool i_size_changed = false;
2266
2267	copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2268
2269	/*
2270	 * No need to use i_size_read() here, the i_size cannot change under us
2271	 * because we hold i_rwsem.
2272	 *
2273	 * But it's important to update i_size while still holding page lock:
2274	 * page writeout could otherwise come in and zero beyond i_size.
2275	 */
2276	if (pos + copied > inode->i_size) {
2277		i_size_write(inode, pos + copied);
2278		i_size_changed = true;
2279	}
2280
2281	unlock_page(page);
2282	put_page(page);
2283
2284	if (old_size < pos)
2285		pagecache_isize_extended(inode, old_size, pos);
2286	/*
2287	 * Don't mark the inode dirty under page lock. First, it unnecessarily
2288	 * makes the holding time of page lock longer. Second, it forces lock
2289	 * ordering of page lock and transaction start for journaling
2290	 * filesystems.
2291	 */
2292	if (i_size_changed)
2293		mark_inode_dirty(inode);
2294	return copied;
2295}
2296EXPORT_SYMBOL(generic_write_end);
2297
2298/*
2299 * block_is_partially_uptodate checks whether buffers within a folio are
2300 * uptodate or not.
2301 *
2302 * Returns true if all buffers which correspond to the specified part
2303 * of the folio are uptodate.
2304 */
2305bool block_is_partially_uptodate(struct folio *folio, size_t from, size_t count)
 
2306{
2307	unsigned block_start, block_end, blocksize;
2308	unsigned to;
2309	struct buffer_head *bh, *head;
2310	bool ret = true;
 
 
 
2311
2312	head = folio_buffers(folio);
2313	if (!head)
2314		return false;
2315	blocksize = head->b_size;
2316	to = min_t(unsigned, folio_size(folio) - from, count);
2317	to = from + to;
2318	if (from < blocksize && to > folio_size(folio) - blocksize)
2319		return false;
2320
2321	bh = head;
2322	block_start = 0;
2323	do {
2324		block_end = block_start + blocksize;
2325		if (block_end > from && block_start < to) {
2326			if (!buffer_uptodate(bh)) {
2327				ret = false;
2328				break;
2329			}
2330			if (block_end >= to)
2331				break;
2332		}
2333		block_start = block_end;
2334		bh = bh->b_this_page;
2335	} while (bh != head);
2336
2337	return ret;
2338}
2339EXPORT_SYMBOL(block_is_partially_uptodate);
2340
2341/*
2342 * Generic "read_folio" function for block devices that have the normal
2343 * get_block functionality. This is most of the block device filesystems.
2344 * Reads the folio asynchronously --- the unlock_buffer() and
2345 * set/clear_buffer_uptodate() functions propagate buffer state into the
2346 * folio once IO has completed.
2347 */
2348int block_read_full_folio(struct folio *folio, get_block_t *get_block)
2349{
2350	struct inode *inode = folio->mapping->host;
2351	sector_t iblock, lblock;
2352	struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2353	size_t blocksize;
2354	int nr, i;
2355	int fully_mapped = 1;
2356	bool page_error = false;
2357	loff_t limit = i_size_read(inode);
2358
2359	/* This is needed for ext4. */
2360	if (IS_ENABLED(CONFIG_FS_VERITY) && IS_VERITY(inode))
2361		limit = inode->i_sb->s_maxbytes;
2362
2363	VM_BUG_ON_FOLIO(folio_test_large(folio), folio);
2364
2365	head = folio_create_buffers(folio, inode, 0);
2366	blocksize = head->b_size;
 
2367
2368	iblock = div_u64(folio_pos(folio), blocksize);
2369	lblock = div_u64(limit + blocksize - 1, blocksize);
2370	bh = head;
2371	nr = 0;
2372	i = 0;
2373
2374	do {
2375		if (buffer_uptodate(bh))
2376			continue;
2377
2378		if (!buffer_mapped(bh)) {
2379			int err = 0;
2380
2381			fully_mapped = 0;
2382			if (iblock < lblock) {
2383				WARN_ON(bh->b_size != blocksize);
2384				err = get_block(inode, iblock, bh, 0);
2385				if (err) {
2386					folio_set_error(folio);
2387					page_error = true;
2388				}
2389			}
2390			if (!buffer_mapped(bh)) {
2391				folio_zero_range(folio, i * blocksize,
2392						blocksize);
2393				if (!err)
2394					set_buffer_uptodate(bh);
2395				continue;
2396			}
2397			/*
2398			 * get_block() might have updated the buffer
2399			 * synchronously
2400			 */
2401			if (buffer_uptodate(bh))
2402				continue;
2403		}
2404		arr[nr++] = bh;
2405	} while (i++, iblock++, (bh = bh->b_this_page) != head);
2406
2407	if (fully_mapped)
2408		folio_set_mappedtodisk(folio);
2409
2410	if (!nr) {
2411		/*
2412		 * All buffers are uptodate or get_block() returned an
2413		 * error when trying to map them - we can finish the read.
2414		 */
2415		folio_end_read(folio, !page_error);
 
 
2416		return 0;
2417	}
2418
2419	/* Stage two: lock the buffers */
2420	for (i = 0; i < nr; i++) {
2421		bh = arr[i];
2422		lock_buffer(bh);
2423		mark_buffer_async_read(bh);
2424	}
2425
2426	/*
2427	 * Stage 3: start the IO.  Check for uptodateness
2428	 * inside the buffer lock in case another process reading
2429	 * the underlying blockdev brought it uptodate (the sct fix).
2430	 */
2431	for (i = 0; i < nr; i++) {
2432		bh = arr[i];
2433		if (buffer_uptodate(bh))
2434			end_buffer_async_read(bh, 1);
2435		else
2436			submit_bh(REQ_OP_READ, bh);
2437	}
2438	return 0;
2439}
2440EXPORT_SYMBOL(block_read_full_folio);
2441
2442/* utility function for filesystems that need to do work on expanding
2443 * truncates.  Uses filesystem pagecache writes to allow the filesystem to
2444 * deal with the hole.  
2445 */
2446int generic_cont_expand_simple(struct inode *inode, loff_t size)
2447{
2448	struct address_space *mapping = inode->i_mapping;
2449	const struct address_space_operations *aops = mapping->a_ops;
2450	struct page *page;
2451	void *fsdata = NULL;
2452	int err;
2453
2454	err = inode_newsize_ok(inode, size);
2455	if (err)
2456		goto out;
2457
2458	err = aops->write_begin(NULL, mapping, size, 0, &page, &fsdata);
 
2459	if (err)
2460		goto out;
2461
2462	err = aops->write_end(NULL, mapping, size, 0, 0, page, fsdata);
2463	BUG_ON(err > 0);
2464
2465out:
2466	return err;
2467}
2468EXPORT_SYMBOL(generic_cont_expand_simple);
2469
2470static int cont_expand_zero(struct file *file, struct address_space *mapping,
2471			    loff_t pos, loff_t *bytes)
2472{
2473	struct inode *inode = mapping->host;
2474	const struct address_space_operations *aops = mapping->a_ops;
2475	unsigned int blocksize = i_blocksize(inode);
2476	struct page *page;
2477	void *fsdata = NULL;
2478	pgoff_t index, curidx;
2479	loff_t curpos;
2480	unsigned zerofrom, offset, len;
2481	int err = 0;
2482
2483	index = pos >> PAGE_SHIFT;
2484	offset = pos & ~PAGE_MASK;
2485
2486	while (index > (curidx = (curpos = *bytes)>>PAGE_SHIFT)) {
2487		zerofrom = curpos & ~PAGE_MASK;
2488		if (zerofrom & (blocksize-1)) {
2489			*bytes |= (blocksize-1);
2490			(*bytes)++;
2491		}
2492		len = PAGE_SIZE - zerofrom;
2493
2494		err = aops->write_begin(file, mapping, curpos, len,
2495					    &page, &fsdata);
2496		if (err)
2497			goto out;
2498		zero_user(page, zerofrom, len);
2499		err = aops->write_end(file, mapping, curpos, len, len,
2500						page, fsdata);
2501		if (err < 0)
2502			goto out;
2503		BUG_ON(err != len);
2504		err = 0;
2505
2506		balance_dirty_pages_ratelimited(mapping);
2507
2508		if (fatal_signal_pending(current)) {
2509			err = -EINTR;
2510			goto out;
2511		}
2512	}
2513
2514	/* page covers the boundary, find the boundary offset */
2515	if (index == curidx) {
2516		zerofrom = curpos & ~PAGE_MASK;
2517		/* if we will expand the thing last block will be filled */
2518		if (offset <= zerofrom) {
2519			goto out;
2520		}
2521		if (zerofrom & (blocksize-1)) {
2522			*bytes |= (blocksize-1);
2523			(*bytes)++;
2524		}
2525		len = offset - zerofrom;
2526
2527		err = aops->write_begin(file, mapping, curpos, len,
2528					    &page, &fsdata);
2529		if (err)
2530			goto out;
2531		zero_user(page, zerofrom, len);
2532		err = aops->write_end(file, mapping, curpos, len, len,
2533						page, fsdata);
2534		if (err < 0)
2535			goto out;
2536		BUG_ON(err != len);
2537		err = 0;
2538	}
2539out:
2540	return err;
2541}
2542
2543/*
2544 * For moronic filesystems that do not allow holes in file.
2545 * We may have to extend the file.
2546 */
2547int cont_write_begin(struct file *file, struct address_space *mapping,
2548			loff_t pos, unsigned len,
2549			struct page **pagep, void **fsdata,
2550			get_block_t *get_block, loff_t *bytes)
2551{
2552	struct inode *inode = mapping->host;
2553	unsigned int blocksize = i_blocksize(inode);
2554	unsigned int zerofrom;
2555	int err;
2556
2557	err = cont_expand_zero(file, mapping, pos, bytes);
2558	if (err)
2559		return err;
2560
2561	zerofrom = *bytes & ~PAGE_MASK;
2562	if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2563		*bytes |= (blocksize-1);
2564		(*bytes)++;
2565	}
2566
2567	return block_write_begin(mapping, pos, len, pagep, get_block);
2568}
2569EXPORT_SYMBOL(cont_write_begin);
2570
2571void block_commit_write(struct page *page, unsigned from, unsigned to)
2572{
2573	struct folio *folio = page_folio(page);
2574	__block_commit_write(folio, from, to);
 
2575}
2576EXPORT_SYMBOL(block_commit_write);
2577
2578/*
2579 * block_page_mkwrite() is not allowed to change the file size as it gets
2580 * called from a page fault handler when a page is first dirtied. Hence we must
2581 * be careful to check for EOF conditions here. We set the page up correctly
2582 * for a written page which means we get ENOSPC checking when writing into
2583 * holes and correct delalloc and unwritten extent mapping on filesystems that
2584 * support these features.
2585 *
2586 * We are not allowed to take the i_mutex here so we have to play games to
2587 * protect against truncate races as the page could now be beyond EOF.  Because
2588 * truncate writes the inode size before removing pages, once we have the
2589 * page lock we can determine safely if the page is beyond EOF. If it is not
2590 * beyond EOF, then the page is guaranteed safe against truncation until we
2591 * unlock the page.
2592 *
2593 * Direct callers of this function should protect against filesystem freezing
2594 * using sb_start_pagefault() - sb_end_pagefault() functions.
2595 */
2596int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2597			 get_block_t get_block)
2598{
2599	struct folio *folio = page_folio(vmf->page);
2600	struct inode *inode = file_inode(vma->vm_file);
2601	unsigned long end;
2602	loff_t size;
2603	int ret;
2604
2605	folio_lock(folio);
2606	size = i_size_read(inode);
2607	if ((folio->mapping != inode->i_mapping) ||
2608	    (folio_pos(folio) >= size)) {
2609		/* We overload EFAULT to mean page got truncated */
2610		ret = -EFAULT;
2611		goto out_unlock;
2612	}
2613
2614	end = folio_size(folio);
2615	/* folio is wholly or partially inside EOF */
2616	if (folio_pos(folio) + end > size)
2617		end = size - folio_pos(folio);
2618
2619	ret = __block_write_begin_int(folio, 0, end, get_block, NULL);
2620	if (unlikely(ret))
2621		goto out_unlock;
2622
2623	__block_commit_write(folio, 0, end);
 
 
2624
2625	folio_mark_dirty(folio);
2626	folio_wait_stable(folio);
 
 
2627	return 0;
2628out_unlock:
2629	folio_unlock(folio);
2630	return ret;
2631}
2632EXPORT_SYMBOL(block_page_mkwrite);
2633
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2634int block_truncate_page(struct address_space *mapping,
2635			loff_t from, get_block_t *get_block)
2636{
2637	pgoff_t index = from >> PAGE_SHIFT;
 
2638	unsigned blocksize;
2639	sector_t iblock;
2640	size_t offset, length, pos;
2641	struct inode *inode = mapping->host;
2642	struct folio *folio;
2643	struct buffer_head *bh;
2644	int err = 0;
2645
2646	blocksize = i_blocksize(inode);
2647	length = from & (blocksize - 1);
2648
2649	/* Block boundary? Nothing to do */
2650	if (!length)
2651		return 0;
2652
2653	length = blocksize - length;
2654	iblock = ((loff_t)index * PAGE_SIZE) >> inode->i_blkbits;
 
 
 
 
 
2655
2656	folio = filemap_grab_folio(mapping, index);
2657	if (IS_ERR(folio))
2658		return PTR_ERR(folio);
2659
2660	bh = folio_buffers(folio);
2661	if (!bh)
2662		bh = create_empty_buffers(folio, blocksize, 0);
2663
2664	/* Find the buffer that contains "offset" */
2665	offset = offset_in_folio(folio, from);
2666	pos = blocksize;
2667	while (offset >= pos) {
2668		bh = bh->b_this_page;
2669		iblock++;
2670		pos += blocksize;
2671	}
2672
 
2673	if (!buffer_mapped(bh)) {
2674		WARN_ON(bh->b_size != blocksize);
2675		err = get_block(inode, iblock, bh, 0);
2676		if (err)
2677			goto unlock;
2678		/* unmapped? It's a hole - nothing to do */
2679		if (!buffer_mapped(bh))
2680			goto unlock;
2681	}
2682
2683	/* Ok, it's mapped. Make sure it's up-to-date */
2684	if (folio_test_uptodate(folio))
2685		set_buffer_uptodate(bh);
2686
2687	if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
2688		err = bh_read(bh, 0);
 
 
2689		/* Uhhuh. Read error. Complain and punt. */
2690		if (err < 0)
2691			goto unlock;
2692	}
2693
2694	folio_zero_range(folio, offset, length);
2695	mark_buffer_dirty(bh);
 
2696
2697unlock:
2698	folio_unlock(folio);
2699	folio_put(folio);
2700
2701	return err;
2702}
2703EXPORT_SYMBOL(block_truncate_page);
2704
2705/*
2706 * The generic ->writepage function for buffer-backed address_spaces
2707 */
2708int block_write_full_folio(struct folio *folio, struct writeback_control *wbc,
2709		void *get_block)
2710{
2711	struct inode * const inode = folio->mapping->host;
2712	loff_t i_size = i_size_read(inode);
 
 
2713
2714	/* Is the folio fully inside i_size? */
2715	if (folio_pos(folio) + folio_size(folio) <= i_size)
2716		return __block_write_full_folio(inode, folio, get_block, wbc);
2717
2718	/* Is the folio fully outside i_size? (truncate in progress) */
2719	if (folio_pos(folio) >= i_size) {
2720		folio_unlock(folio);
 
 
2721		return 0; /* don't care */
2722	}
2723
2724	/*
2725	 * The folio straddles i_size.  It must be zeroed out on each and every
2726	 * writepage invocation because it may be mmapped.  "A file is mapped
2727	 * in multiples of the page size.  For a file that is not a multiple of
2728	 * the page size, the remaining memory is zeroed when mapped, and
2729	 * writes to that region are not written out to the file."
2730	 */
2731	folio_zero_segment(folio, offset_in_folio(folio, i_size),
2732			folio_size(folio));
2733	return __block_write_full_folio(inode, folio, get_block, wbc);
2734}
 
2735
2736sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2737			    get_block_t *get_block)
2738{
2739	struct inode *inode = mapping->host;
2740	struct buffer_head tmp = {
2741		.b_size = i_blocksize(inode),
2742	};
2743
2744	get_block(inode, block, &tmp, 0);
2745	return tmp.b_blocknr;
2746}
2747EXPORT_SYMBOL(generic_block_bmap);
2748
2749static void end_bio_bh_io_sync(struct bio *bio)
2750{
2751	struct buffer_head *bh = bio->bi_private;
2752
2753	if (unlikely(bio_flagged(bio, BIO_QUIET)))
2754		set_bit(BH_Quiet, &bh->b_state);
2755
2756	bh->b_end_io(bh, !bio->bi_status);
2757	bio_put(bio);
2758}
2759
2760static void submit_bh_wbc(blk_opf_t opf, struct buffer_head *bh,
2761			  enum rw_hint write_hint,
2762			  struct writeback_control *wbc)
2763{
2764	const enum req_op op = opf & REQ_OP_MASK;
2765	struct bio *bio;
2766
2767	BUG_ON(!buffer_locked(bh));
2768	BUG_ON(!buffer_mapped(bh));
2769	BUG_ON(!bh->b_end_io);
2770	BUG_ON(buffer_delay(bh));
2771	BUG_ON(buffer_unwritten(bh));
2772
2773	/*
2774	 * Only clear out a write error when rewriting
2775	 */
2776	if (test_set_buffer_req(bh) && (op == REQ_OP_WRITE))
2777		clear_buffer_write_io_error(bh);
2778
2779	if (buffer_meta(bh))
2780		opf |= REQ_META;
2781	if (buffer_prio(bh))
2782		opf |= REQ_PRIO;
2783
2784	bio = bio_alloc(bh->b_bdev, 1, opf, GFP_NOIO);
2785
2786	fscrypt_set_bio_crypt_ctx_bh(bio, bh, GFP_NOIO);
2787
2788	bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
 
2789	bio->bi_write_hint = write_hint;
2790
2791	__bio_add_page(bio, bh->b_page, bh->b_size, bh_offset(bh));
 
2792
2793	bio->bi_end_io = end_bio_bh_io_sync;
2794	bio->bi_private = bh;
2795
 
 
 
 
 
 
2796	/* Take care of bh's that straddle the end of the device */
2797	guard_bio_eod(bio);
2798
2799	if (wbc) {
2800		wbc_init_bio(wbc, bio);
2801		wbc_account_cgroup_owner(wbc, bh->b_page, bh->b_size);
2802	}
2803
2804	submit_bio(bio);
 
2805}
2806
2807void submit_bh(blk_opf_t opf, struct buffer_head *bh)
2808{
2809	submit_bh_wbc(opf, bh, WRITE_LIFE_NOT_SET, NULL);
2810}
2811EXPORT_SYMBOL(submit_bh);
2812
2813void write_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2814{
2815	lock_buffer(bh);
2816	if (!test_clear_buffer_dirty(bh)) {
2817		unlock_buffer(bh);
2818		return;
2819	}
2820	bh->b_end_io = end_buffer_write_sync;
2821	get_bh(bh);
2822	submit_bh(REQ_OP_WRITE | op_flags, bh);
2823}
2824EXPORT_SYMBOL(write_dirty_buffer);
2825
2826/*
2827 * For a data-integrity writeout, we need to wait upon any in-progress I/O
2828 * and then start new I/O and then wait upon it.  The caller must have a ref on
2829 * the buffer_head.
2830 */
2831int __sync_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags)
2832{
 
 
2833	WARN_ON(atomic_read(&bh->b_count) < 1);
2834	lock_buffer(bh);
2835	if (test_clear_buffer_dirty(bh)) {
2836		/*
2837		 * The bh should be mapped, but it might not be if the
2838		 * device was hot-removed. Not much we can do but fail the I/O.
2839		 */
2840		if (!buffer_mapped(bh)) {
2841			unlock_buffer(bh);
2842			return -EIO;
2843		}
2844
2845		get_bh(bh);
2846		bh->b_end_io = end_buffer_write_sync;
2847		submit_bh(REQ_OP_WRITE | op_flags, bh);
2848		wait_on_buffer(bh);
2849		if (!buffer_uptodate(bh))
2850			return -EIO;
2851	} else {
2852		unlock_buffer(bh);
2853	}
2854	return 0;
2855}
2856EXPORT_SYMBOL(__sync_dirty_buffer);
2857
2858int sync_dirty_buffer(struct buffer_head *bh)
2859{
2860	return __sync_dirty_buffer(bh, REQ_SYNC);
2861}
2862EXPORT_SYMBOL(sync_dirty_buffer);
2863
2864/*
2865 * try_to_free_buffers() checks if all the buffers on this particular folio
2866 * are unused, and releases them if so.
2867 *
2868 * Exclusion against try_to_free_buffers may be obtained by either
2869 * locking the folio or by holding its mapping's i_private_lock.
2870 *
2871 * If the folio is dirty but all the buffers are clean then we need to
2872 * be sure to mark the folio clean as well.  This is because the folio
2873 * may be against a block device, and a later reattachment of buffers
2874 * to a dirty folio will set *all* buffers dirty.  Which would corrupt
2875 * filesystem data on the same device.
2876 *
2877 * The same applies to regular filesystem folios: if all the buffers are
2878 * clean then we set the folio clean and proceed.  To do that, we require
2879 * total exclusion from block_dirty_folio().  That is obtained with
2880 * i_private_lock.
2881 *
2882 * try_to_free_buffers() is non-blocking.
2883 */
2884static inline int buffer_busy(struct buffer_head *bh)
2885{
2886	return atomic_read(&bh->b_count) |
2887		(bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
2888}
2889
2890static bool
2891drop_buffers(struct folio *folio, struct buffer_head **buffers_to_free)
2892{
2893	struct buffer_head *head = folio_buffers(folio);
2894	struct buffer_head *bh;
2895
2896	bh = head;
2897	do {
2898		if (buffer_busy(bh))
2899			goto failed;
2900		bh = bh->b_this_page;
2901	} while (bh != head);
2902
2903	do {
2904		struct buffer_head *next = bh->b_this_page;
2905
2906		if (bh->b_assoc_map)
2907			__remove_assoc_queue(bh);
2908		bh = next;
2909	} while (bh != head);
2910	*buffers_to_free = head;
2911	folio_detach_private(folio);
2912	return true;
2913failed:
2914	return false;
2915}
2916
2917bool try_to_free_buffers(struct folio *folio)
2918{
2919	struct address_space * const mapping = folio->mapping;
2920	struct buffer_head *buffers_to_free = NULL;
2921	bool ret = 0;
2922
2923	BUG_ON(!folio_test_locked(folio));
2924	if (folio_test_writeback(folio))
2925		return false;
2926
2927	if (mapping == NULL) {		/* can this still happen? */
2928		ret = drop_buffers(folio, &buffers_to_free);
2929		goto out;
2930	}
2931
2932	spin_lock(&mapping->i_private_lock);
2933	ret = drop_buffers(folio, &buffers_to_free);
2934
2935	/*
2936	 * If the filesystem writes its buffers by hand (eg ext3)
2937	 * then we can have clean buffers against a dirty folio.  We
2938	 * clean the folio here; otherwise the VM will never notice
2939	 * that the filesystem did any IO at all.
2940	 *
2941	 * Also, during truncate, discard_buffer will have marked all
2942	 * the folio's buffers clean.  We discover that here and clean
2943	 * the folio also.
2944	 *
2945	 * i_private_lock must be held over this entire operation in order
2946	 * to synchronise against block_dirty_folio and prevent the
2947	 * dirty bit from being lost.
2948	 */
2949	if (ret)
2950		folio_cancel_dirty(folio);
2951	spin_unlock(&mapping->i_private_lock);
2952out:
2953	if (buffers_to_free) {
2954		struct buffer_head *bh = buffers_to_free;
2955
2956		do {
2957			struct buffer_head *next = bh->b_this_page;
2958			free_buffer_head(bh);
2959			bh = next;
2960		} while (bh != buffers_to_free);
2961	}
2962	return ret;
2963}
2964EXPORT_SYMBOL(try_to_free_buffers);
2965
2966/*
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2967 * Buffer-head allocation
2968 */
2969static struct kmem_cache *bh_cachep __ro_after_init;
2970
2971/*
2972 * Once the number of bh's in the machine exceeds this level, we start
2973 * stripping them in writeback.
2974 */
2975static unsigned long max_buffer_heads __ro_after_init;
2976
2977int buffer_heads_over_limit;
2978
2979struct bh_accounting {
2980	int nr;			/* Number of live bh's */
2981	int ratelimit;		/* Limit cacheline bouncing */
2982};
2983
2984static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
2985
2986static void recalc_bh_state(void)
2987{
2988	int i;
2989	int tot = 0;
2990
2991	if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
2992		return;
2993	__this_cpu_write(bh_accounting.ratelimit, 0);
2994	for_each_online_cpu(i)
2995		tot += per_cpu(bh_accounting, i).nr;
2996	buffer_heads_over_limit = (tot > max_buffer_heads);
2997}
2998
2999struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
3000{
3001	struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
3002	if (ret) {
3003		INIT_LIST_HEAD(&ret->b_assoc_buffers);
3004		spin_lock_init(&ret->b_uptodate_lock);
3005		preempt_disable();
3006		__this_cpu_inc(bh_accounting.nr);
3007		recalc_bh_state();
3008		preempt_enable();
3009	}
3010	return ret;
3011}
3012EXPORT_SYMBOL(alloc_buffer_head);
3013
3014void free_buffer_head(struct buffer_head *bh)
3015{
3016	BUG_ON(!list_empty(&bh->b_assoc_buffers));
3017	kmem_cache_free(bh_cachep, bh);
3018	preempt_disable();
3019	__this_cpu_dec(bh_accounting.nr);
3020	recalc_bh_state();
3021	preempt_enable();
3022}
3023EXPORT_SYMBOL(free_buffer_head);
3024
3025static int buffer_exit_cpu_dead(unsigned int cpu)
3026{
3027	int i;
3028	struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3029
3030	for (i = 0; i < BH_LRU_SIZE; i++) {
3031		brelse(b->bhs[i]);
3032		b->bhs[i] = NULL;
3033	}
3034	this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
3035	per_cpu(bh_accounting, cpu).nr = 0;
3036	return 0;
3037}
3038
3039/**
3040 * bh_uptodate_or_lock - Test whether the buffer is uptodate
3041 * @bh: struct buffer_head
3042 *
3043 * Return true if the buffer is up-to-date and false,
3044 * with the buffer locked, if not.
3045 */
3046int bh_uptodate_or_lock(struct buffer_head *bh)
3047{
3048	if (!buffer_uptodate(bh)) {
3049		lock_buffer(bh);
3050		if (!buffer_uptodate(bh))
3051			return 0;
3052		unlock_buffer(bh);
3053	}
3054	return 1;
3055}
3056EXPORT_SYMBOL(bh_uptodate_or_lock);
3057
3058/**
3059 * __bh_read - Submit read for a locked buffer
3060 * @bh: struct buffer_head
3061 * @op_flags: appending REQ_OP_* flags besides REQ_OP_READ
3062 * @wait: wait until reading finish
3063 *
3064 * Returns zero on success or don't wait, and -EIO on error.
3065 */
3066int __bh_read(struct buffer_head *bh, blk_opf_t op_flags, bool wait)
3067{
3068	int ret = 0;
3069
3070	BUG_ON(!buffer_locked(bh));
3071
3072	get_bh(bh);
3073	bh->b_end_io = end_buffer_read_sync;
3074	submit_bh(REQ_OP_READ | op_flags, bh);
3075	if (wait) {
3076		wait_on_buffer(bh);
3077		if (!buffer_uptodate(bh))
3078			ret = -EIO;
3079	}
3080	return ret;
3081}
3082EXPORT_SYMBOL(__bh_read);
3083
3084/**
3085 * __bh_read_batch - Submit read for a batch of unlocked buffers
3086 * @nr: entry number of the buffer batch
3087 * @bhs: a batch of struct buffer_head
3088 * @op_flags: appending REQ_OP_* flags besides REQ_OP_READ
3089 * @force_lock: force to get a lock on the buffer if set, otherwise drops any
3090 *              buffer that cannot lock.
3091 *
3092 * Returns zero on success or don't wait, and -EIO on error.
3093 */
3094void __bh_read_batch(int nr, struct buffer_head *bhs[],
3095		     blk_opf_t op_flags, bool force_lock)
3096{
3097	int i;
3098
3099	for (i = 0; i < nr; i++) {
3100		struct buffer_head *bh = bhs[i];
3101
3102		if (buffer_uptodate(bh))
3103			continue;
3104
3105		if (force_lock)
3106			lock_buffer(bh);
3107		else
3108			if (!trylock_buffer(bh))
3109				continue;
3110
3111		if (buffer_uptodate(bh)) {
3112			unlock_buffer(bh);
3113			continue;
3114		}
3115
3116		bh->b_end_io = end_buffer_read_sync;
3117		get_bh(bh);
3118		submit_bh(REQ_OP_READ | op_flags, bh);
3119	}
3120}
3121EXPORT_SYMBOL(__bh_read_batch);
3122
3123void __init buffer_init(void)
3124{
3125	unsigned long nrpages;
3126	int ret;
3127
3128	bh_cachep = KMEM_CACHE(buffer_head,
3129				SLAB_RECLAIM_ACCOUNT|SLAB_PANIC);
 
 
 
 
3130	/*
3131	 * Limit the bh occupancy to 10% of ZONE_NORMAL
3132	 */
3133	nrpages = (nr_free_buffer_pages() * 10) / 100;
3134	max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3135	ret = cpuhp_setup_state_nocalls(CPUHP_FS_BUFF_DEAD, "fs/buffer:dead",
3136					NULL, buffer_exit_cpu_dead);
3137	WARN_ON(ret < 0);
3138}