file.c 24.2 KB
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948
/*
 *  linux/fs/affs/file.c
 *
 *  (c) 1996  Hans-Joachim Widmaier - Rewritten
 *
 *  (C) 1993  Ray Burr - Modified for Amiga FFS filesystem.
 *
 *  (C) 1992  Eric Youngdale Modified for ISO 9660 filesystem.
 *
 *  (C) 1991  Linus Torvalds - minix filesystem
 *
 *  affs regular file handling primitives
 */

#include "affs.h"

#if PAGE_SIZE < 4096
#error PAGE_SIZE must be at least 4096
#endif

static int affs_grow_extcache(struct inode *inode, u32 lc_idx);
static struct buffer_head *affs_alloc_extblock(struct inode *inode, struct buffer_head *bh, u32 ext);
static inline struct buffer_head *affs_get_extblock(struct inode *inode, u32 ext);
static struct buffer_head *affs_get_extblock_slow(struct inode *inode, u32 ext);
static int affs_file_open(struct inode *inode, struct file *filp);
static int affs_file_release(struct inode *inode, struct file *filp);

const struct file_operations affs_file_operations = {
	.llseek		= generic_file_llseek,
	.read		= do_sync_read,
	.aio_read	= generic_file_aio_read,
	.write		= do_sync_write,
	.aio_write	= generic_file_aio_write,
	.mmap		= generic_file_mmap,
	.open		= affs_file_open,
	.release	= affs_file_release,
	.fsync		= affs_file_fsync,
	.splice_read	= generic_file_splice_read,
};

const struct inode_operations affs_file_inode_operations = {
	.setattr	= affs_notify_change,
};

static int
affs_file_open(struct inode *inode, struct file *filp)
{
	pr_debug("AFFS: open(%lu,%d)\n",
		 inode->i_ino, atomic_read(&AFFS_I(inode)->i_opencnt));
	atomic_inc(&AFFS_I(inode)->i_opencnt);
	return 0;
}

static int
affs_file_release(struct inode *inode, struct file *filp)
{
	pr_debug("AFFS: release(%lu, %d)\n",
		 inode->i_ino, atomic_read(&AFFS_I(inode)->i_opencnt));

	if (atomic_dec_and_test(&AFFS_I(inode)->i_opencnt)) {
		mutex_lock(&inode->i_mutex);
		if (inode->i_size != AFFS_I(inode)->mmu_private)
			affs_truncate(inode);
		affs_free_prealloc(inode);
		mutex_unlock(&inode->i_mutex);
	}

	return 0;
}

static int
affs_grow_extcache(struct inode *inode, u32 lc_idx)
{
	struct super_block	*sb = inode->i_sb;
	struct buffer_head	*bh;
	u32 lc_max;
	int i, j, key;

	if (!AFFS_I(inode)->i_lc) {
		char *ptr = (char *)get_zeroed_page(GFP_NOFS);
		if (!ptr)
			return -ENOMEM;
		AFFS_I(inode)->i_lc = (u32 *)ptr;
		AFFS_I(inode)->i_ac = (struct affs_ext_key *)(ptr + AFFS_CACHE_SIZE / 2);
	}

	lc_max = AFFS_LC_SIZE << AFFS_I(inode)->i_lc_shift;

	if (AFFS_I(inode)->i_extcnt > lc_max) {
		u32 lc_shift, lc_mask, tmp, off;

		/* need to recalculate linear cache, start from old size */
		lc_shift = AFFS_I(inode)->i_lc_shift;
		tmp = (AFFS_I(inode)->i_extcnt / AFFS_LC_SIZE) >> lc_shift;
		for (; tmp; tmp >>= 1)
			lc_shift++;
		lc_mask = (1 << lc_shift) - 1;

		/* fix idx and old size to new shift */
		lc_idx >>= (lc_shift - AFFS_I(inode)->i_lc_shift);
		AFFS_I(inode)->i_lc_size >>= (lc_shift - AFFS_I(inode)->i_lc_shift);

		/* first shrink old cache to make more space */
		off = 1 << (lc_shift - AFFS_I(inode)->i_lc_shift);
		for (i = 1, j = off; j < AFFS_LC_SIZE; i++, j += off)
			AFFS_I(inode)->i_ac[i] = AFFS_I(inode)->i_ac[j];

		AFFS_I(inode)->i_lc_shift = lc_shift;
		AFFS_I(inode)->i_lc_mask = lc_mask;
	}

	/* fill cache to the needed index */
	i = AFFS_I(inode)->i_lc_size;
	AFFS_I(inode)->i_lc_size = lc_idx + 1;
	for (; i <= lc_idx; i++) {
		if (!i) {
			AFFS_I(inode)->i_lc[0] = inode->i_ino;
			continue;
		}
		key = AFFS_I(inode)->i_lc[i - 1];
		j = AFFS_I(inode)->i_lc_mask + 1;
		// unlock cache
		for (; j > 0; j--) {
			bh = affs_bread(sb, key);
			if (!bh)
				goto err;
			key = be32_to_cpu(AFFS_TAIL(sb, bh)->extension);
			affs_brelse(bh);
		}
		// lock cache
		AFFS_I(inode)->i_lc[i] = key;
	}

	return 0;

err:
	// lock cache
	return -EIO;
}

static struct buffer_head *
affs_alloc_extblock(struct inode *inode, struct buffer_head *bh, u32 ext)
{
	struct super_block *sb = inode->i_sb;
	struct buffer_head *new_bh;
	u32 blocknr, tmp;

	blocknr = affs_alloc_block(inode, bh->b_blocknr);
	if (!blocknr)
		return ERR_PTR(-ENOSPC);

	new_bh = affs_getzeroblk(sb, blocknr);
	if (!new_bh) {
		affs_free_block(sb, blocknr);
		return ERR_PTR(-EIO);
	}

	AFFS_HEAD(new_bh)->ptype = cpu_to_be32(T_LIST);
	AFFS_HEAD(new_bh)->key = cpu_to_be32(blocknr);
	AFFS_TAIL(sb, new_bh)->stype = cpu_to_be32(ST_FILE);
	AFFS_TAIL(sb, new_bh)->parent = cpu_to_be32(inode->i_ino);
	affs_fix_checksum(sb, new_bh);

	mark_buffer_dirty_inode(new_bh, inode);

	tmp = be32_to_cpu(AFFS_TAIL(sb, bh)->extension);
	if (tmp)
		affs_warning(sb, "alloc_ext", "previous extension set (%x)", tmp);
	AFFS_TAIL(sb, bh)->extension = cpu_to_be32(blocknr);
	affs_adjust_checksum(bh, blocknr - tmp);
	mark_buffer_dirty_inode(bh, inode);

	AFFS_I(inode)->i_extcnt++;
	mark_inode_dirty(inode);

	return new_bh;
}

static inline struct buffer_head *
affs_get_extblock(struct inode *inode, u32 ext)
{
	/* inline the simplest case: same extended block as last time */
	struct buffer_head *bh = AFFS_I(inode)->i_ext_bh;
	if (ext == AFFS_I(inode)->i_ext_last)
		get_bh(bh);
	else
		/* we have to do more (not inlined) */
		bh = affs_get_extblock_slow(inode, ext);

	return bh;
}

static struct buffer_head *
affs_get_extblock_slow(struct inode *inode, u32 ext)
{
	struct super_block *sb = inode->i_sb;
	struct buffer_head *bh;
	u32 ext_key;
	u32 lc_idx, lc_off, ac_idx;
	u32 tmp, idx;

	if (ext == AFFS_I(inode)->i_ext_last + 1) {
		/* read the next extended block from the current one */
		bh = AFFS_I(inode)->i_ext_bh;
		ext_key = be32_to_cpu(AFFS_TAIL(sb, bh)->extension);
		if (ext < AFFS_I(inode)->i_extcnt)
			goto read_ext;
		if (ext > AFFS_I(inode)->i_extcnt)
			BUG();
		bh = affs_alloc_extblock(inode, bh, ext);
		if (IS_ERR(bh))
			return bh;
		goto store_ext;
	}

	if (ext == 0) {
		/* we seek back to the file header block */
		ext_key = inode->i_ino;
		goto read_ext;
	}

	if (ext >= AFFS_I(inode)->i_extcnt) {
		struct buffer_head *prev_bh;

		/* allocate a new extended block */
		if (ext > AFFS_I(inode)->i_extcnt)
			BUG();

		/* get previous extended block */
		prev_bh = affs_get_extblock(inode, ext - 1);
		if (IS_ERR(prev_bh))
			return prev_bh;
		bh = affs_alloc_extblock(inode, prev_bh, ext);
		affs_brelse(prev_bh);
		if (IS_ERR(bh))
			return bh;
		goto store_ext;
	}

again:
	/* check if there is an extended cache and whether it's large enough */
	lc_idx = ext >> AFFS_I(inode)->i_lc_shift;
	lc_off = ext & AFFS_I(inode)->i_lc_mask;

	if (lc_idx >= AFFS_I(inode)->i_lc_size) {
		int err;

		err = affs_grow_extcache(inode, lc_idx);
		if (err)
			return ERR_PTR(err);
		goto again;
	}

	/* every n'th key we find in the linear cache */
	if (!lc_off) {
		ext_key = AFFS_I(inode)->i_lc[lc_idx];
		goto read_ext;
	}

	/* maybe it's still in the associative cache */
	ac_idx = (ext - lc_idx - 1) & AFFS_AC_MASK;
	if (AFFS_I(inode)->i_ac[ac_idx].ext == ext) {
		ext_key = AFFS_I(inode)->i_ac[ac_idx].key;
		goto read_ext;
	}

	/* try to find one of the previous extended blocks */
	tmp = ext;
	idx = ac_idx;
	while (--tmp, --lc_off > 0) {
		idx = (idx - 1) & AFFS_AC_MASK;
		if (AFFS_I(inode)->i_ac[idx].ext == tmp) {
			ext_key = AFFS_I(inode)->i_ac[idx].key;
			goto find_ext;
		}
	}

	/* fall back to the linear cache */
	ext_key = AFFS_I(inode)->i_lc[lc_idx];
find_ext:
	/* read all extended blocks until we find the one we need */
	//unlock cache
	do {
		bh = affs_bread(sb, ext_key);
		if (!bh)
			goto err_bread;
		ext_key = be32_to_cpu(AFFS_TAIL(sb, bh)->extension);
		affs_brelse(bh);
		tmp++;
	} while (tmp < ext);
	//lock cache

	/* store it in the associative cache */
	// recalculate ac_idx?
	AFFS_I(inode)->i_ac[ac_idx].ext = ext;
	AFFS_I(inode)->i_ac[ac_idx].key = ext_key;

read_ext:
	/* finally read the right extended block */
	//unlock cache
	bh = affs_bread(sb, ext_key);
	if (!bh)
		goto err_bread;
	//lock cache

store_ext:
	/* release old cached extended block and store the new one */
	affs_brelse(AFFS_I(inode)->i_ext_bh);
	AFFS_I(inode)->i_ext_last = ext;
	AFFS_I(inode)->i_ext_bh = bh;
	get_bh(bh);

	return bh;

err_bread:
	affs_brelse(bh);
	return ERR_PTR(-EIO);
}

static int
affs_get_block(struct inode *inode, sector_t block, struct buffer_head *bh_result, int create)
{
	struct super_block	*sb = inode->i_sb;
	struct buffer_head	*ext_bh;
	u32			 ext;

	pr_debug("AFFS: get_block(%u, %lu)\n", (u32)inode->i_ino, (unsigned long)block);

	BUG_ON(block > (sector_t)0x7fffffffUL);

	if (block >= AFFS_I(inode)->i_blkcnt) {
		if (block > AFFS_I(inode)->i_blkcnt || !create)
			goto err_big;
	} else
		create = 0;

	//lock cache
	affs_lock_ext(inode);

	ext = (u32)block / AFFS_SB(sb)->s_hashsize;
	block -= ext * AFFS_SB(sb)->s_hashsize;
	ext_bh = affs_get_extblock(inode, ext);
	if (IS_ERR(ext_bh))
		goto err_ext;
	map_bh(bh_result, sb, (sector_t)be32_to_cpu(AFFS_BLOCK(sb, ext_bh, block)));

	if (create) {
		u32 blocknr = affs_alloc_block(inode, ext_bh->b_blocknr);
		if (!blocknr)
			goto err_alloc;
		set_buffer_new(bh_result);
		AFFS_I(inode)->mmu_private += AFFS_SB(sb)->s_data_blksize;
		AFFS_I(inode)->i_blkcnt++;

		/* store new block */
		if (bh_result->b_blocknr)
			affs_warning(sb, "get_block", "block already set (%x)", bh_result->b_blocknr);
		AFFS_BLOCK(sb, ext_bh, block) = cpu_to_be32(blocknr);
		AFFS_HEAD(ext_bh)->block_count = cpu_to_be32(block + 1);
		affs_adjust_checksum(ext_bh, blocknr - bh_result->b_blocknr + 1);
		bh_result->b_blocknr = blocknr;

		if (!block) {
			/* insert first block into header block */
			u32 tmp = be32_to_cpu(AFFS_HEAD(ext_bh)->first_data);
			if (tmp)
				affs_warning(sb, "get_block", "first block already set (%d)", tmp);
			AFFS_HEAD(ext_bh)->first_data = cpu_to_be32(blocknr);
			affs_adjust_checksum(ext_bh, blocknr - tmp);
		}
	}

	affs_brelse(ext_bh);
	//unlock cache
	affs_unlock_ext(inode);
	return 0;

err_big:
	affs_error(inode->i_sb,"get_block","strange block request %d", block);
	return -EIO;
err_ext:
	// unlock cache
	affs_unlock_ext(inode);
	return PTR_ERR(ext_bh);
err_alloc:
	brelse(ext_bh);
	clear_buffer_mapped(bh_result);
	bh_result->b_bdev = NULL;
	// unlock cache
	affs_unlock_ext(inode);
	return -ENOSPC;
}

static int affs_writepage(struct page *page, struct writeback_control *wbc)
{
	return block_write_full_page(page, affs_get_block, wbc);
}

static int affs_readpage(struct file *file, struct page *page)
{
	return block_read_full_page(page, affs_get_block);
}

static void affs_write_failed(struct address_space *mapping, loff_t to)
{
	struct inode *inode = mapping->host;

	if (to > inode->i_size) {
		truncate_pagecache(inode, inode->i_size);
		affs_truncate(inode);
	}
}

static int affs_write_begin(struct file *file, struct address_space *mapping,
			loff_t pos, unsigned len, unsigned flags,
			struct page **pagep, void **fsdata)
{
	int ret;

	*pagep = NULL;
	ret = cont_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
				affs_get_block,
				&AFFS_I(mapping->host)->mmu_private);
	if (unlikely(ret))
		affs_write_failed(mapping, pos + len);

	return ret;
}

static sector_t _affs_bmap(struct address_space *mapping, sector_t block)
{
	return generic_block_bmap(mapping,block,affs_get_block);
}

const struct address_space_operations affs_aops = {
	.readpage = affs_readpage,
	.writepage = affs_writepage,
	.write_begin = affs_write_begin,
	.write_end = generic_write_end,
	.bmap = _affs_bmap
};

static inline struct buffer_head *
affs_bread_ino(struct inode *inode, int block, int create)
{
	struct buffer_head *bh, tmp_bh;
	int err;

	tmp_bh.b_state = 0;
	err = affs_get_block(inode, block, &tmp_bh, create);
	if (!err) {
		bh = affs_bread(inode->i_sb, tmp_bh.b_blocknr);
		if (bh) {
			bh->b_state |= tmp_bh.b_state;
			return bh;
		}
		err = -EIO;
	}
	return ERR_PTR(err);
}

static inline struct buffer_head *
affs_getzeroblk_ino(struct inode *inode, int block)
{
	struct buffer_head *bh, tmp_bh;
	int err;

	tmp_bh.b_state = 0;
	err = affs_get_block(inode, block, &tmp_bh, 1);
	if (!err) {
		bh = affs_getzeroblk(inode->i_sb, tmp_bh.b_blocknr);
		if (bh) {
			bh->b_state |= tmp_bh.b_state;
			return bh;
		}
		err = -EIO;
	}
	return ERR_PTR(err);
}

static inline struct buffer_head *
affs_getemptyblk_ino(struct inode *inode, int block)
{
	struct buffer_head *bh, tmp_bh;
	int err;

	tmp_bh.b_state = 0;
	err = affs_get_block(inode, block, &tmp_bh, 1);
	if (!err) {
		bh = affs_getemptyblk(inode->i_sb, tmp_bh.b_blocknr);
		if (bh) {
			bh->b_state |= tmp_bh.b_state;
			return bh;
		}
		err = -EIO;
	}
	return ERR_PTR(err);
}

static int
affs_do_readpage_ofs(struct file *file, struct page *page, unsigned from, unsigned to)
{
	struct inode *inode = page->mapping->host;
	struct super_block *sb = inode->i_sb;
	struct buffer_head *bh;
	char *data;
	u32 bidx, boff, bsize;
	u32 tmp;

	pr_debug("AFFS: read_page(%u, %ld, %d, %d)\n", (u32)inode->i_ino, page->index, from, to);
	BUG_ON(from > to || to > PAGE_CACHE_SIZE);
	kmap(page);
	data = page_address(page);
	bsize = AFFS_SB(sb)->s_data_blksize;
	tmp = (page->index << PAGE_CACHE_SHIFT) + from;
	bidx = tmp / bsize;
	boff = tmp % bsize;

	while (from < to) {
		bh = affs_bread_ino(inode, bidx, 0);
		if (IS_ERR(bh))
			return PTR_ERR(bh);
		tmp = min(bsize - boff, to - from);
		BUG_ON(from + tmp > to || tmp > bsize);
		memcpy(data + from, AFFS_DATA(bh) + boff, tmp);
		affs_brelse(bh);
		bidx++;
		from += tmp;
		boff = 0;
	}
	flush_dcache_page(page);
	kunmap(page);
	return 0;
}

static int
affs_extent_file_ofs(struct inode *inode, u32 newsize)
{
	struct super_block *sb = inode->i_sb;
	struct buffer_head *bh, *prev_bh;
	u32 bidx, boff;
	u32 size, bsize;
	u32 tmp;

	pr_debug("AFFS: extent_file(%u, %d)\n", (u32)inode->i_ino, newsize);
	bsize = AFFS_SB(sb)->s_data_blksize;
	bh = NULL;
	size = AFFS_I(inode)->mmu_private;
	bidx = size / bsize;
	boff = size % bsize;
	if (boff) {
		bh = affs_bread_ino(inode, bidx, 0);
		if (IS_ERR(bh))
			return PTR_ERR(bh);
		tmp = min(bsize - boff, newsize - size);
		BUG_ON(boff + tmp > bsize || tmp > bsize);
		memset(AFFS_DATA(bh) + boff, 0, tmp);
		be32_add_cpu(&AFFS_DATA_HEAD(bh)->size, tmp);
		affs_fix_checksum(sb, bh);
		mark_buffer_dirty_inode(bh, inode);
		size += tmp;
		bidx++;
	} else if (bidx) {
		bh = affs_bread_ino(inode, bidx - 1, 0);
		if (IS_ERR(bh))
			return PTR_ERR(bh);
	}

	while (size < newsize) {
		prev_bh = bh;
		bh = affs_getzeroblk_ino(inode, bidx);
		if (IS_ERR(bh))
			goto out;
		tmp = min(bsize, newsize - size);
		BUG_ON(tmp > bsize);
		AFFS_DATA_HEAD(bh)->ptype = cpu_to_be32(T_DATA);
		AFFS_DATA_HEAD(bh)->key = cpu_to_be32(inode->i_ino);
		AFFS_DATA_HEAD(bh)->sequence = cpu_to_be32(bidx);
		AFFS_DATA_HEAD(bh)->size = cpu_to_be32(tmp);
		affs_fix_checksum(sb, bh);
		bh->b_state &= ~(1UL << BH_New);
		mark_buffer_dirty_inode(bh, inode);
		if (prev_bh) {
			u32 tmp = be32_to_cpu(AFFS_DATA_HEAD(prev_bh)->next);
			if (tmp)
				affs_warning(sb, "extent_file_ofs", "next block already set for %d (%d)", bidx, tmp);
			AFFS_DATA_HEAD(prev_bh)->next = cpu_to_be32(bh->b_blocknr);
			affs_adjust_checksum(prev_bh, bh->b_blocknr - tmp);
			mark_buffer_dirty_inode(prev_bh, inode);
			affs_brelse(prev_bh);
		}
		size += bsize;
		bidx++;
	}
	affs_brelse(bh);
	inode->i_size = AFFS_I(inode)->mmu_private = newsize;
	return 0;

out:
	inode->i_size = AFFS_I(inode)->mmu_private = newsize;
	return PTR_ERR(bh);
}

static int
affs_readpage_ofs(struct file *file, struct page *page)
{
	struct inode *inode = page->mapping->host;
	u32 to;
	int err;

	pr_debug("AFFS: read_page(%u, %ld)\n", (u32)inode->i_ino, page->index);
	to = PAGE_CACHE_SIZE;
	if (((page->index + 1) << PAGE_CACHE_SHIFT) > inode->i_size) {
		to = inode->i_size & ~PAGE_CACHE_MASK;
		memset(page_address(page) + to, 0, PAGE_CACHE_SIZE - to);
	}

	err = affs_do_readpage_ofs(file, page, 0, to);
	if (!err)
		SetPageUptodate(page);
	unlock_page(page);
	return err;
}

static int affs_write_begin_ofs(struct file *file, struct address_space *mapping,
				loff_t pos, unsigned len, unsigned flags,
				struct page **pagep, void **fsdata)
{
	struct inode *inode = mapping->host;
	struct page *page;
	pgoff_t index;
	int err = 0;

	pr_debug("AFFS: write_begin(%u, %llu, %llu)\n", (u32)inode->i_ino, (unsigned long long)pos, (unsigned long long)pos + len);
	if (pos > AFFS_I(inode)->mmu_private) {
		/* XXX: this probably leaves a too-big i_size in case of
		 * failure. Should really be updating i_size at write_end time
		 */
		err = affs_extent_file_ofs(inode, pos);
		if (err)
			return err;
	}

	index = pos >> PAGE_CACHE_SHIFT;
	page = grab_cache_page_write_begin(mapping, index, flags);
	if (!page)
		return -ENOMEM;
	*pagep = page;

	if (PageUptodate(page))
		return 0;

	/* XXX: inefficient but safe in the face of short writes */
	err = affs_do_readpage_ofs(file, page, 0, PAGE_CACHE_SIZE);
	if (err) {
		unlock_page(page);
		page_cache_release(page);
	}
	return err;
}

static int affs_write_end_ofs(struct file *file, struct address_space *mapping,
				loff_t pos, unsigned len, unsigned copied,
				struct page *page, void *fsdata)
{
	struct inode *inode = mapping->host;
	struct super_block *sb = inode->i_sb;
	struct buffer_head *bh, *prev_bh;
	char *data;
	u32 bidx, boff, bsize;
	unsigned from, to;
	u32 tmp;
	int written;

	from = pos & (PAGE_CACHE_SIZE - 1);
	to = pos + len;
	/*
	 * XXX: not sure if this can handle short copies (len < copied), but
	 * we don't have to, because the page should always be uptodate here,
	 * due to write_begin.
	 */

	pr_debug("AFFS: write_begin(%u, %llu, %llu)\n", (u32)inode->i_ino, (unsigned long long)pos, (unsigned long long)pos + len);
	bsize = AFFS_SB(sb)->s_data_blksize;
	data = page_address(page);

	bh = NULL;
	written = 0;
	tmp = (page->index << PAGE_CACHE_SHIFT) + from;
	bidx = tmp / bsize;
	boff = tmp % bsize;
	if (boff) {
		bh = affs_bread_ino(inode, bidx, 0);
		if (IS_ERR(bh))
			return PTR_ERR(bh);
		tmp = min(bsize - boff, to - from);
		BUG_ON(boff + tmp > bsize || tmp > bsize);
		memcpy(AFFS_DATA(bh) + boff, data + from, tmp);
		be32_add_cpu(&AFFS_DATA_HEAD(bh)->size, tmp);
		affs_fix_checksum(sb, bh);
		mark_buffer_dirty_inode(bh, inode);
		written += tmp;
		from += tmp;
		bidx++;
	} else if (bidx) {
		bh = affs_bread_ino(inode, bidx - 1, 0);
		if (IS_ERR(bh))
			return PTR_ERR(bh);
	}
	while (from + bsize <= to) {
		prev_bh = bh;
		bh = affs_getemptyblk_ino(inode, bidx);
		if (IS_ERR(bh))
			goto out;
		memcpy(AFFS_DATA(bh), data + from, bsize);
		if (buffer_new(bh)) {
			AFFS_DATA_HEAD(bh)->ptype = cpu_to_be32(T_DATA);
			AFFS_DATA_HEAD(bh)->key = cpu_to_be32(inode->i_ino);
			AFFS_DATA_HEAD(bh)->sequence = cpu_to_be32(bidx);
			AFFS_DATA_HEAD(bh)->size = cpu_to_be32(bsize);
			AFFS_DATA_HEAD(bh)->next = 0;
			bh->b_state &= ~(1UL << BH_New);
			if (prev_bh) {
				u32 tmp = be32_to_cpu(AFFS_DATA_HEAD(prev_bh)->next);
				if (tmp)
					affs_warning(sb, "commit_write_ofs", "next block already set for %d (%d)", bidx, tmp);
				AFFS_DATA_HEAD(prev_bh)->next = cpu_to_be32(bh->b_blocknr);
				affs_adjust_checksum(prev_bh, bh->b_blocknr - tmp);
				mark_buffer_dirty_inode(prev_bh, inode);
			}
		}
		affs_brelse(prev_bh);
		affs_fix_checksum(sb, bh);
		mark_buffer_dirty_inode(bh, inode);
		written += bsize;
		from += bsize;
		bidx++;
	}
	if (from < to) {
		prev_bh = bh;
		bh = affs_bread_ino(inode, bidx, 1);
		if (IS_ERR(bh))
			goto out;
		tmp = min(bsize, to - from);
		BUG_ON(tmp > bsize);
		memcpy(AFFS_DATA(bh), data + from, tmp);
		if (buffer_new(bh)) {
			AFFS_DATA_HEAD(bh)->ptype = cpu_to_be32(T_DATA);
			AFFS_DATA_HEAD(bh)->key = cpu_to_be32(inode->i_ino);
			AFFS_DATA_HEAD(bh)->sequence = cpu_to_be32(bidx);
			AFFS_DATA_HEAD(bh)->size = cpu_to_be32(tmp);
			AFFS_DATA_HEAD(bh)->next = 0;
			bh->b_state &= ~(1UL << BH_New);
			if (prev_bh) {
				u32 tmp = be32_to_cpu(AFFS_DATA_HEAD(prev_bh)->next);
				if (tmp)
					affs_warning(sb, "commit_write_ofs", "next block already set for %d (%d)", bidx, tmp);
				AFFS_DATA_HEAD(prev_bh)->next = cpu_to_be32(bh->b_blocknr);
				affs_adjust_checksum(prev_bh, bh->b_blocknr - tmp);
				mark_buffer_dirty_inode(prev_bh, inode);
			}
		} else if (be32_to_cpu(AFFS_DATA_HEAD(bh)->size) < tmp)
			AFFS_DATA_HEAD(bh)->size = cpu_to_be32(tmp);
		affs_brelse(prev_bh);
		affs_fix_checksum(sb, bh);
		mark_buffer_dirty_inode(bh, inode);
		written += tmp;
		from += tmp;
		bidx++;
	}
	SetPageUptodate(page);

done:
	affs_brelse(bh);
	tmp = (page->index << PAGE_CACHE_SHIFT) + from;
	if (tmp > inode->i_size)
		inode->i_size = AFFS_I(inode)->mmu_private = tmp;

	unlock_page(page);
	page_cache_release(page);

	return written;

out:
	bh = prev_bh;
	if (!written)
		written = PTR_ERR(bh);
	goto done;
}

const struct address_space_operations affs_aops_ofs = {
	.readpage = affs_readpage_ofs,
	//.writepage = affs_writepage_ofs,
	.write_begin = affs_write_begin_ofs,
	.write_end = affs_write_end_ofs
};

/* Free any preallocated blocks. */

void
affs_free_prealloc(struct inode *inode)
{
	struct super_block *sb = inode->i_sb;

	pr_debug("AFFS: free_prealloc(ino=%lu)\n", inode->i_ino);

	while (AFFS_I(inode)->i_pa_cnt) {
		AFFS_I(inode)->i_pa_cnt--;
		affs_free_block(sb, ++AFFS_I(inode)->i_lastalloc);
	}
}

/* Truncate (or enlarge) a file to the requested size. */

void
affs_truncate(struct inode *inode)
{
	struct super_block *sb = inode->i_sb;
	u32 ext, ext_key;
	u32 last_blk, blkcnt, blk;
	u32 size;
	struct buffer_head *ext_bh;
	int i;

	pr_debug("AFFS: truncate(inode=%d, oldsize=%u, newsize=%u)\n",
		 (u32)inode->i_ino, (u32)AFFS_I(inode)->mmu_private, (u32)inode->i_size);

	last_blk = 0;
	ext = 0;
	if (inode->i_size) {
		last_blk = ((u32)inode->i_size - 1) / AFFS_SB(sb)->s_data_blksize;
		ext = last_blk / AFFS_SB(sb)->s_hashsize;
	}

	if (inode->i_size > AFFS_I(inode)->mmu_private) {
		struct address_space *mapping = inode->i_mapping;
		struct page *page;
		void *fsdata;
		loff_t size = inode->i_size;
		int res;

		res = mapping->a_ops->write_begin(NULL, mapping, size, 0, 0, &page, &fsdata);
		if (!res)
			res = mapping->a_ops->write_end(NULL, mapping, size, 0, 0, page, fsdata);
		else
			inode->i_size = AFFS_I(inode)->mmu_private;
		mark_inode_dirty(inode);
		return;
	} else if (inode->i_size == AFFS_I(inode)->mmu_private)
		return;

	// lock cache
	ext_bh = affs_get_extblock(inode, ext);
	if (IS_ERR(ext_bh)) {
		affs_warning(sb, "truncate", "unexpected read error for ext block %u (%d)",
			     ext, PTR_ERR(ext_bh));
		return;
	}
	if (AFFS_I(inode)->i_lc) {
		/* clear linear cache */
		i = (ext + 1) >> AFFS_I(inode)->i_lc_shift;
		if (AFFS_I(inode)->i_lc_size > i) {
			AFFS_I(inode)->i_lc_size = i;
			for (; i < AFFS_LC_SIZE; i++)
				AFFS_I(inode)->i_lc[i] = 0;
		}
		/* clear associative cache */
		for (i = 0; i < AFFS_AC_SIZE; i++)
			if (AFFS_I(inode)->i_ac[i].ext >= ext)
				AFFS_I(inode)->i_ac[i].ext = 0;
	}
	ext_key = be32_to_cpu(AFFS_TAIL(sb, ext_bh)->extension);

	blkcnt = AFFS_I(inode)->i_blkcnt;
	i = 0;
	blk = last_blk;
	if (inode->i_size) {
		i = last_blk % AFFS_SB(sb)->s_hashsize + 1;
		blk++;
	} else
		AFFS_HEAD(ext_bh)->first_data = 0;
	AFFS_HEAD(ext_bh)->block_count = cpu_to_be32(i);
	size = AFFS_SB(sb)->s_hashsize;
	if (size > blkcnt - blk + i)
		size = blkcnt - blk + i;
	for (; i < size; i++, blk++) {
		affs_free_block(sb, be32_to_cpu(AFFS_BLOCK(sb, ext_bh, i)));
		AFFS_BLOCK(sb, ext_bh, i) = 0;
	}
	AFFS_TAIL(sb, ext_bh)->extension = 0;
	affs_fix_checksum(sb, ext_bh);
	mark_buffer_dirty_inode(ext_bh, inode);
	affs_brelse(ext_bh);

	if (inode->i_size) {
		AFFS_I(inode)->i_blkcnt = last_blk + 1;
		AFFS_I(inode)->i_extcnt = ext + 1;
		if (AFFS_SB(sb)->s_flags & SF_OFS) {
			struct buffer_head *bh = affs_bread_ino(inode, last_blk, 0);
			u32 tmp;
			if (IS_ERR(bh)) {
				affs_warning(sb, "truncate", "unexpected read error for last block %u (%d)",
					     ext, PTR_ERR(bh));
				return;
			}
			tmp = be32_to_cpu(AFFS_DATA_HEAD(bh)->next);
			AFFS_DATA_HEAD(bh)->next = 0;
			affs_adjust_checksum(bh, -tmp);
			affs_brelse(bh);
		}
	} else {
		AFFS_I(inode)->i_blkcnt = 0;
		AFFS_I(inode)->i_extcnt = 1;
	}
	AFFS_I(inode)->mmu_private = inode->i_size;
	// unlock cache

	while (ext_key) {
		ext_bh = affs_bread(sb, ext_key);
		size = AFFS_SB(sb)->s_hashsize;
		if (size > blkcnt - blk)
			size = blkcnt - blk;
		for (i = 0; i < size; i++, blk++)
			affs_free_block(sb, be32_to_cpu(AFFS_BLOCK(sb, ext_bh, i)));
		affs_free_block(sb, ext_key);
		ext_key = be32_to_cpu(AFFS_TAIL(sb, ext_bh)->extension);
		affs_brelse(ext_bh);
	}
	affs_free_prealloc(inode);
}

int affs_file_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
{
	struct inode *inode = filp->f_mapping->host;
	int ret, err;

	err = filemap_write_and_wait_range(inode->i_mapping, start, end);
	if (err)
		return err;

	mutex_lock(&inode->i_mutex);
	ret = write_inode_now(inode, 0);
	err = sync_blockdev(inode->i_sb->s_bdev);
	if (!ret)
		ret = err;
	mutex_unlock(&inode->i_mutex);
	return ret;
}