1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 *  linux/fs/ext2/balloc.c
   4 *
   5 * Copyright (C) 1992, 1993, 1994, 1995
   6 * Remy Card (card@masi.ibp.fr)
   7 * Laboratoire MASI - Institut Blaise Pascal
   8 * Universite Pierre et Marie Curie (Paris VI)
   9 *
  10 *  Enhanced block allocation by Stephen Tweedie (sct@redhat.com), 1993
  11 *  Big-endian to little-endian byte-swapping/bitmaps by
  12 *        David S. Miller (davem@caip.rutgers.edu), 1995
  13 */
  14
  15#include "ext2.h"
  16#include <linux/quotaops.h>
  17#include <linux/slab.h>
  18#include <linux/sched.h>
  19#include <linux/cred.h>
  20#include <linux/buffer_head.h>
  21#include <linux/capability.h>
  22
  23/*
  24 * balloc.c contains the blocks allocation and deallocation routines
  25 */
  26
  27/*
  28 * The free blocks are managed by bitmaps.  A file system contains several
  29 * blocks groups.  Each group contains 1 bitmap block for blocks, 1 bitmap
  30 * block for inodes, N blocks for the inode table and data blocks.
  31 *
  32 * The file system contains group descriptors which are located after the
  33 * super block.  Each descriptor contains the number of the bitmap block and
  34 * the free blocks count in the block.  The descriptors are loaded in memory
  35 * when a file system is mounted (see ext2_fill_super).
  36 */
  37
  38
  39#define in_range(b, first, len)	((b) >= (first) && (b) <= (first) + (len) - 1)
  40
  41struct ext2_group_desc * ext2_get_group_desc(struct super_block * sb,
  42					     unsigned int block_group,
  43					     struct buffer_head ** bh)
  44{
  45	unsigned long group_desc;
  46	unsigned long offset;
  47	struct ext2_group_desc * desc;
  48	struct ext2_sb_info *sbi = EXT2_SB(sb);
  49
  50	if (block_group >= sbi->s_groups_count) {
  51		WARN(1, "block_group >= groups_count - "
  52		     "block_group = %d, groups_count = %lu",
  53		     block_group, sbi->s_groups_count);
  54
  55		return NULL;
  56	}
  57
  58	group_desc = block_group >> EXT2_DESC_PER_BLOCK_BITS(sb);
  59	offset = block_group & (EXT2_DESC_PER_BLOCK(sb) - 1);
  60	if (!sbi->s_group_desc[group_desc]) {
  61		WARN(1, "Group descriptor not loaded - "
  62		     "block_group = %d, group_desc = %lu, desc = %lu",
  63		      block_group, group_desc, offset);
  64		return NULL;
  65	}
  66
  67	desc = (struct ext2_group_desc *) sbi->s_group_desc[group_desc]->b_data;
  68	if (bh)
  69		*bh = sbi->s_group_desc[group_desc];
  70	return desc + offset;
  71}
  72
  73static int ext2_valid_block_bitmap(struct super_block *sb,
  74					struct ext2_group_desc *desc,
  75					unsigned int block_group,
  76					struct buffer_head *bh)
  77{
  78	ext2_grpblk_t offset;
  79	ext2_grpblk_t next_zero_bit;
  80	ext2_fsblk_t bitmap_blk;
  81	ext2_fsblk_t group_first_block;
  82
  83	group_first_block = ext2_group_first_block_no(sb, block_group);
  84
  85	/* check whether block bitmap block number is set */
  86	bitmap_blk = le32_to_cpu(desc->bg_block_bitmap);
  87	offset = bitmap_blk - group_first_block;
  88	if (!ext2_test_bit(offset, bh->b_data))
  89		/* bad block bitmap */
  90		goto err_out;
  91
  92	/* check whether the inode bitmap block number is set */
  93	bitmap_blk = le32_to_cpu(desc->bg_inode_bitmap);
  94	offset = bitmap_blk - group_first_block;
  95	if (!ext2_test_bit(offset, bh->b_data))
  96		/* bad block bitmap */
  97		goto err_out;
  98
  99	/* check whether the inode table block number is set */
 100	bitmap_blk = le32_to_cpu(desc->bg_inode_table);
 101	offset = bitmap_blk - group_first_block;
 102	next_zero_bit = ext2_find_next_zero_bit(bh->b_data,
 103				offset + EXT2_SB(sb)->s_itb_per_group,
 104				offset);
 105	if (next_zero_bit >= offset + EXT2_SB(sb)->s_itb_per_group)
 106		/* good bitmap for inode tables */
 107		return 1;
 108
 109err_out:
 110	ext2_error(sb, __func__,
 111			"Invalid block bitmap - "
 112			"block_group = %d, block = %lu",
 113			block_group, bitmap_blk);
 114	return 0;
 115}
 116
 117/*
 118 * Read the bitmap for a given block_group,and validate the
 119 * bits for block/inode/inode tables are set in the bitmaps
 120 *
 121 * Return buffer_head on success or NULL in case of failure.
 122 */
 123static struct buffer_head *
 124read_block_bitmap(struct super_block *sb, unsigned int block_group)
 125{
 126	struct ext2_group_desc * desc;
 127	struct buffer_head * bh = NULL;
 128	ext2_fsblk_t bitmap_blk;
 129	int ret;
 130
 131	desc = ext2_get_group_desc(sb, block_group, NULL);
 132	if (!desc)
 133		return NULL;
 134	bitmap_blk = le32_to_cpu(desc->bg_block_bitmap);
 135	bh = sb_getblk(sb, bitmap_blk);
 136	if (unlikely(!bh)) {
 137		ext2_error(sb, __func__,
 138			    "Cannot read block bitmap - "
 139			    "block_group = %d, block_bitmap = %u",
 140			    block_group, le32_to_cpu(desc->bg_block_bitmap));
 141		return NULL;
 142	}
 143	ret = bh_read(bh, 0);
 144	if (ret > 0)
 145		return bh;
 146	if (ret < 0) {
 147		brelse(bh);
 148		ext2_error(sb, __func__,
 149			    "Cannot read block bitmap - "
 150			    "block_group = %d, block_bitmap = %u",
 151			    block_group, le32_to_cpu(desc->bg_block_bitmap));
 152		return NULL;
 153	}
 154
 155	ext2_valid_block_bitmap(sb, desc, block_group, bh);
 156	/*
 157	 * file system mounted not to panic on error, continue with corrupt
 158	 * bitmap
 159	 */
 160	return bh;
 161}
 162
 163static void group_adjust_blocks(struct super_block *sb, int group_no,
 164	struct ext2_group_desc *desc, struct buffer_head *bh, int count)
 165{
 166	if (count) {
 167		struct ext2_sb_info *sbi = EXT2_SB(sb);
 168		unsigned free_blocks;
 169
 170		spin_lock(sb_bgl_lock(sbi, group_no));
 171		free_blocks = le16_to_cpu(desc->bg_free_blocks_count);
 172		desc->bg_free_blocks_count = cpu_to_le16(free_blocks + count);
 173		spin_unlock(sb_bgl_lock(sbi, group_no));
 174		mark_buffer_dirty(bh);
 175	}
 176}
 177
 178/*
 179 * The reservation window structure operations
 180 * --------------------------------------------
 181 * Operations include:
 182 * dump, find, add, remove, is_empty, find_next_reservable_window, etc.
 183 *
 184 * We use a red-black tree to represent per-filesystem reservation
 185 * windows.
 186 *
 187 */
 188
 189/**
 190 * __rsv_window_dump() -- Dump the filesystem block allocation reservation map
 191 * @root:		root of per-filesystem reservation rb tree
 192 * @verbose:		verbose mode
 193 * @fn:			function which wishes to dump the reservation map
 194 *
 195 * If verbose is turned on, it will print the whole block reservation
 196 * windows(start, end). Otherwise, it will only print out the "bad" windows,
 197 * those windows that overlap with their immediate neighbors.
 198 */
 199#if 1
 200static void __rsv_window_dump(struct rb_root *root, int verbose,
 201			      const char *fn)
 202{
 203	struct rb_node *n;
 204	struct ext2_reserve_window_node *rsv, *prev;
 205	int bad;
 206
 207restart:
 208	n = rb_first(root);
 209	bad = 0;
 210	prev = NULL;
 211
 212	printk("Block Allocation Reservation Windows Map (%s):\n", fn);
 213	while (n) {
 214		rsv = rb_entry(n, struct ext2_reserve_window_node, rsv_node);
 215		if (verbose)
 216			printk("reservation window 0x%p "
 217				"start: %lu, end: %lu\n",
 218				rsv, rsv->rsv_start, rsv->rsv_end);
 219		if (rsv->rsv_start && rsv->rsv_start >= rsv->rsv_end) {
 220			printk("Bad reservation %p (start >= end)\n",
 221			       rsv);
 222			bad = 1;
 223		}
 224		if (prev && prev->rsv_end >= rsv->rsv_start) {
 225			printk("Bad reservation %p (prev->end >= start)\n",
 226			       rsv);
 227			bad = 1;
 228		}
 229		if (bad) {
 230			if (!verbose) {
 231				printk("Restarting reservation walk in verbose mode\n");
 232				verbose = 1;
 233				goto restart;
 234			}
 235		}
 236		n = rb_next(n);
 237		prev = rsv;
 238	}
 239	printk("Window map complete.\n");
 240	BUG_ON(bad);
 241}
 242#define rsv_window_dump(root, verbose) \
 243	__rsv_window_dump((root), (verbose), __func__)
 244#else
 245#define rsv_window_dump(root, verbose) do {} while (0)
 246#endif
 247
 248/**
 249 * goal_in_my_reservation()
 250 * @rsv:		inode's reservation window
 251 * @grp_goal:		given goal block relative to the allocation block group
 252 * @group:		the current allocation block group
 253 * @sb:			filesystem super block
 254 *
 255 * Test if the given goal block (group relative) is within the file's
 256 * own block reservation window range.
 257 *
 258 * If the reservation window is outside the goal allocation group, return 0;
 259 * grp_goal (given goal block) could be -1, which means no specific
 260 * goal block. In this case, always return 1.
 261 * If the goal block is within the reservation window, return 1;
 262 * otherwise, return 0;
 263 */
 264static int
 265goal_in_my_reservation(struct ext2_reserve_window *rsv, ext2_grpblk_t grp_goal,
 266			unsigned int group, struct super_block * sb)
 267{
 268	ext2_fsblk_t group_first_block, group_last_block;
 269
 270	group_first_block = ext2_group_first_block_no(sb, group);
 271	group_last_block = ext2_group_last_block_no(sb, group);
 272
 273	if ((rsv->_rsv_start > group_last_block) ||
 274	    (rsv->_rsv_end < group_first_block))
 275		return 0;
 276	if ((grp_goal >= 0) && ((grp_goal + group_first_block < rsv->_rsv_start)
 277		|| (grp_goal + group_first_block > rsv->_rsv_end)))
 278		return 0;
 279	return 1;
 280}
 281
 282/**
 283 * search_reserve_window()
 284 * @root:		root of reservation tree
 285 * @goal:		target allocation block
 286 *
 287 * Find the reserved window which includes the goal, or the previous one
 288 * if the goal is not in any window.
 289 * Returns NULL if there are no windows or if all windows start after the goal.
 290 */
 291static struct ext2_reserve_window_node *
 292search_reserve_window(struct rb_root *root, ext2_fsblk_t goal)
 293{
 294	struct rb_node *n = root->rb_node;
 295	struct ext2_reserve_window_node *rsv;
 296
 297	if (!n)
 298		return NULL;
 299
 300	do {
 301		rsv = rb_entry(n, struct ext2_reserve_window_node, rsv_node);
 302
 303		if (goal < rsv->rsv_start)
 304			n = n->rb_left;
 305		else if (goal > rsv->rsv_end)
 306			n = n->rb_right;
 307		else
 308			return rsv;
 309	} while (n);
 310	/*
 311	 * We've fallen off the end of the tree: the goal wasn't inside
 312	 * any particular node.  OK, the previous node must be to one
 313	 * side of the interval containing the goal.  If it's the RHS,
 314	 * we need to back up one.
 315	 */
 316	if (rsv->rsv_start > goal) {
 317		n = rb_prev(&rsv->rsv_node);
 318		rsv = rb_entry(n, struct ext2_reserve_window_node, rsv_node);
 319	}
 320	return rsv;
 321}
 322
 323/*
 324 * ext2_rsv_window_add() -- Insert a window to the block reservation rb tree.
 325 * @sb:			super block
 326 * @rsv:		reservation window to add
 327 *
 328 * Must be called with rsv_lock held.
 329 */
 330void ext2_rsv_window_add(struct super_block *sb,
 331		    struct ext2_reserve_window_node *rsv)
 332{
 333	struct rb_root *root = &EXT2_SB(sb)->s_rsv_window_root;
 334	struct rb_node *node = &rsv->rsv_node;
 335	ext2_fsblk_t start = rsv->rsv_start;
 336
 337	struct rb_node ** p = &root->rb_node;
 338	struct rb_node * parent = NULL;
 339	struct ext2_reserve_window_node *this;
 340
 341	while (*p)
 342	{
 343		parent = *p;
 344		this = rb_entry(parent, struct ext2_reserve_window_node, rsv_node);
 345
 346		if (start < this->rsv_start)
 347			p = &(*p)->rb_left;
 348		else if (start > this->rsv_end)
 349			p = &(*p)->rb_right;
 350		else {
 351			rsv_window_dump(root, 1);
 352			BUG();
 353		}
 354	}
 355
 356	rb_link_node(node, parent, p);
 357	rb_insert_color(node, root);
 358}
 359
 360/**
 361 * rsv_window_remove() -- unlink a window from the reservation rb tree
 362 * @sb:			super block
 363 * @rsv:		reservation window to remove
 364 *
 365 * Mark the block reservation window as not allocated, and unlink it
 366 * from the filesystem reservation window rb tree. Must be called with
 367 * rsv_lock held.
 368 */
 369static void rsv_window_remove(struct super_block *sb,
 370			      struct ext2_reserve_window_node *rsv)
 371{
 372	rsv->rsv_start = EXT2_RESERVE_WINDOW_NOT_ALLOCATED;
 373	rsv->rsv_end = EXT2_RESERVE_WINDOW_NOT_ALLOCATED;
 374	rsv->rsv_alloc_hit = 0;
 375	rb_erase(&rsv->rsv_node, &EXT2_SB(sb)->s_rsv_window_root);
 376}
 377
 378/*
 379 * rsv_is_empty() -- Check if the reservation window is allocated.
 380 * @rsv:		given reservation window to check
 381 *
 382 * returns 1 if the end block is EXT2_RESERVE_WINDOW_NOT_ALLOCATED.
 383 */
 384static inline int rsv_is_empty(struct ext2_reserve_window *rsv)
 385{
 386	/* a valid reservation end block could not be 0 */
 387	return (rsv->_rsv_end == EXT2_RESERVE_WINDOW_NOT_ALLOCATED);
 388}
 389
 390/**
 391 * ext2_init_block_alloc_info()
 392 * @inode:		file inode structure
 393 *
 394 * Allocate and initialize the  reservation window structure, and
 395 * link the window to the ext2 inode structure at last
 396 *
 397 * The reservation window structure is only dynamically allocated
 398 * and linked to ext2 inode the first time the open file
 399 * needs a new block. So, before every ext2_new_block(s) call, for
 400 * regular files, we should check whether the reservation window
 401 * structure exists or not. In the latter case, this function is called.
 402 * Fail to do so will result in block reservation being turned off for that
 403 * open file.
 404 *
 405 * This function is called from ext2_get_blocks_handle(), also called
 406 * when setting the reservation window size through ioctl before the file
 407 * is open for write (needs block allocation).
 408 *
 409 * Needs truncate_mutex protection prior to calling this function.
 410 */
 411void ext2_init_block_alloc_info(struct inode *inode)
 412{
 413	struct ext2_inode_info *ei = EXT2_I(inode);
 414	struct ext2_block_alloc_info *block_i;
 415	struct super_block *sb = inode->i_sb;
 416
 417	block_i = kmalloc(sizeof(*block_i), GFP_NOFS);
 418	if (block_i) {
 419		struct ext2_reserve_window_node *rsv = &block_i->rsv_window_node;
 420
 421		rsv->rsv_start = EXT2_RESERVE_WINDOW_NOT_ALLOCATED;
 422		rsv->rsv_end = EXT2_RESERVE_WINDOW_NOT_ALLOCATED;
 423
 424	 	/*
 425		 * if filesystem is mounted with NORESERVATION, the goal
 426		 * reservation window size is set to zero to indicate
 427		 * block reservation is off
 428		 */
 429		if (!test_opt(sb, RESERVATION))
 430			rsv->rsv_goal_size = 0;
 431		else
 432			rsv->rsv_goal_size = EXT2_DEFAULT_RESERVE_BLOCKS;
 433		rsv->rsv_alloc_hit = 0;
 434		block_i->last_alloc_logical_block = 0;
 435		block_i->last_alloc_physical_block = 0;
 436	}
 437	ei->i_block_alloc_info = block_i;
 438}
 439
 440/**
 441 * ext2_discard_reservation()
 442 * @inode:		inode
 443 *
 444 * Discard(free) block reservation window on last file close, or truncate
 445 * or at last iput().
 446 *
 447 * It is being called in three cases:
 448 * 	ext2_release_file(): last writer closes the file
 449 * 	ext2_clear_inode(): last iput(), when nobody links to this file.
 450 * 	ext2_truncate(): when the block indirect map is about to change.
 451 */
 452void ext2_discard_reservation(struct inode *inode)
 453{
 454	struct ext2_inode_info *ei = EXT2_I(inode);
 455	struct ext2_block_alloc_info *block_i = ei->i_block_alloc_info;
 456	struct ext2_reserve_window_node *rsv;
 457	spinlock_t *rsv_lock = &EXT2_SB(inode->i_sb)->s_rsv_window_lock;
 458
 459	if (!block_i)
 460		return;
 461
 462	rsv = &block_i->rsv_window_node;
 463	if (!rsv_is_empty(&rsv->rsv_window)) {
 464		spin_lock(rsv_lock);
 465		if (!rsv_is_empty(&rsv->rsv_window))
 466			rsv_window_remove(inode->i_sb, rsv);
 467		spin_unlock(rsv_lock);
 468	}
 469}
 470
 471/**
 472 * ext2_free_blocks() -- Free given blocks and update quota and i_blocks
 473 * @inode:		inode
 474 * @block:		start physical block to free
 475 * @count:		number of blocks to free
 476 */
 477void ext2_free_blocks (struct inode * inode, unsigned long block,
 478		       unsigned long count)
 479{
 480	struct buffer_head *bitmap_bh = NULL;
 481	struct buffer_head * bh2;
 482	unsigned long block_group;
 483	unsigned long bit;
 484	unsigned long i;
 485	unsigned long overflow;
 486	struct super_block * sb = inode->i_sb;
 487	struct ext2_sb_info * sbi = EXT2_SB(sb);
 488	struct ext2_group_desc * desc;
 489	struct ext2_super_block * es = sbi->s_es;
 490	unsigned freed = 0, group_freed;
 491
 492	if (!ext2_data_block_valid(sbi, block, count)) {
 493		ext2_error (sb, "ext2_free_blocks",
 494			    "Freeing blocks not in datazone - "
 495			    "block = %lu, count = %lu", block, count);
 496		goto error_return;
 497	}
 498
 499	ext2_debug ("freeing block(s) %lu-%lu\n", block, block + count - 1);
 500
 501do_more:
 502	overflow = 0;
 503	block_group = (block - le32_to_cpu(es->s_first_data_block)) /
 504		      EXT2_BLOCKS_PER_GROUP(sb);
 505	bit = (block - le32_to_cpu(es->s_first_data_block)) %
 506		      EXT2_BLOCKS_PER_GROUP(sb);
 507	/*
 508	 * Check to see if we are freeing blocks across a group
 509	 * boundary.
 510	 */
 511	if (bit + count > EXT2_BLOCKS_PER_GROUP(sb)) {
 512		overflow = bit + count - EXT2_BLOCKS_PER_GROUP(sb);
 513		count -= overflow;
 514	}
 515	brelse(bitmap_bh);
 516	bitmap_bh = read_block_bitmap(sb, block_group);
 517	if (!bitmap_bh)
 518		goto error_return;
 519
 520	desc = ext2_get_group_desc (sb, block_group, &bh2);
 521	if (!desc)
 522		goto error_return;
 523
 524	if (in_range (le32_to_cpu(desc->bg_block_bitmap), block, count) ||
 525	    in_range (le32_to_cpu(desc->bg_inode_bitmap), block, count) ||
 526	    in_range (block, le32_to_cpu(desc->bg_inode_table),
 527		      sbi->s_itb_per_group) ||
 528	    in_range (block + count - 1, le32_to_cpu(desc->bg_inode_table),
 529		      sbi->s_itb_per_group)) {
 530		ext2_error (sb, "ext2_free_blocks",
 531			    "Freeing blocks in system zones - "
 532			    "Block = %lu, count = %lu",
 533			    block, count);
 534		goto error_return;
 535	}
 536
 537	for (i = 0, group_freed = 0; i < count; i++) {
 538		if (!ext2_clear_bit_atomic(sb_bgl_lock(sbi, block_group),
 539						bit + i, bitmap_bh->b_data)) {
 540			ext2_error(sb, __func__,
 541				"bit already cleared for block %lu", block + i);
 542		} else {
 543			group_freed++;
 544		}
 545	}
 546
 547	mark_buffer_dirty(bitmap_bh);
 548	if (sb->s_flags & SB_SYNCHRONOUS)
 549		sync_dirty_buffer(bitmap_bh);
 550
 551	group_adjust_blocks(sb, block_group, desc, bh2, group_freed);
 552	freed += group_freed;
 553
 554	if (overflow) {
 555		block += count;
 556		count = overflow;
 557		goto do_more;
 558	}
 559error_return:
 560	brelse(bitmap_bh);
 561	if (freed) {
 562		percpu_counter_add(&sbi->s_freeblocks_counter, freed);
 563		dquot_free_block_nodirty(inode, freed);
 564		mark_inode_dirty(inode);
 565	}
 566}
 567
 568/**
 569 * bitmap_search_next_usable_block()
 570 * @start:		the starting block (group relative) of the search
 571 * @bh:			bufferhead contains the block group bitmap
 572 * @maxblocks:		the ending block (group relative) of the reservation
 573 *
 574 * The bitmap search --- search forward through the actual bitmap on disk until
 575 * we find a bit free.
 576 */
 577static ext2_grpblk_t
 578bitmap_search_next_usable_block(ext2_grpblk_t start, struct buffer_head *bh,
 579					ext2_grpblk_t maxblocks)
 580{
 581	ext2_grpblk_t next;
 582
 583	next = ext2_find_next_zero_bit(bh->b_data, maxblocks, start);
 584	if (next >= maxblocks)
 585		return -1;
 586	return next;
 587}
 588
 589/**
 590 * find_next_usable_block()
 591 * @start:		the starting block (group relative) to find next
 592 * 			allocatable block in bitmap.
 593 * @bh:			bufferhead contains the block group bitmap
 594 * @maxblocks:		the ending block (group relative) for the search
 595 *
 596 * Find an allocatable block in a bitmap.  We perform the "most
 597 * appropriate allocation" algorithm of looking for a free block near
 598 * the initial goal; then for a free byte somewhere in the bitmap;
 599 * then for any free bit in the bitmap.
 600 */
 601static ext2_grpblk_t
 602find_next_usable_block(int start, struct buffer_head *bh, int maxblocks)
 603{
 604	ext2_grpblk_t here, next;
 605	char *p, *r;
 606
 607	if (start > 0) {
 608		/*
 609		 * The goal was occupied; search forward for a free 
 610		 * block within the next XX blocks.
 611		 *
 612		 * end_goal is more or less random, but it has to be
 613		 * less than EXT2_BLOCKS_PER_GROUP. Aligning up to the
 614		 * next 64-bit boundary is simple..
 615		 */
 616		ext2_grpblk_t end_goal = (start + 63) & ~63;
 617		if (end_goal > maxblocks)
 618			end_goal = maxblocks;
 619		here = ext2_find_next_zero_bit(bh->b_data, end_goal, start);
 620		if (here < end_goal)
 621			return here;
 622		ext2_debug("Bit not found near goal\n");
 623	}
 624
 625	here = start;
 626	if (here < 0)
 627		here = 0;
 628
 629	p = ((char *)bh->b_data) + (here >> 3);
 630	r = memscan(p, 0, ((maxblocks + 7) >> 3) - (here >> 3));
 631	next = (r - ((char *)bh->b_data)) << 3;
 632
 633	if (next < maxblocks && next >= here)
 634		return next;
 635
 636	here = bitmap_search_next_usable_block(here, bh, maxblocks);
 637	return here;
 638}
 639
 640/**
 641 * ext2_try_to_allocate()
 642 * @sb:			superblock
 643 * @group:		given allocation block group
 644 * @bitmap_bh:		bufferhead holds the block bitmap
 645 * @grp_goal:		given target block within the group
 646 * @count:		target number of blocks to allocate
 647 * @my_rsv:		reservation window
 648 *
 649 * Attempt to allocate blocks within a give range. Set the range of allocation
 650 * first, then find the first free bit(s) from the bitmap (within the range),
 651 * and at last, allocate the blocks by claiming the found free bit as allocated.
 652 *
 653 * To set the range of this allocation:
 654 * 	if there is a reservation window, only try to allocate block(s)
 655 * 	from the file's own reservation window;
 656 * 	Otherwise, the allocation range starts from the give goal block,
 657 * 	ends at the block group's last block.
 658 *
 659 * If we failed to allocate the desired block then we may end up crossing to a
 660 * new bitmap.
 661 */
 662static int
 663ext2_try_to_allocate(struct super_block *sb, int group,
 664			struct buffer_head *bitmap_bh, ext2_grpblk_t grp_goal,
 665			unsigned long *count,
 666			struct ext2_reserve_window *my_rsv)
 667{
 668	ext2_fsblk_t group_first_block = ext2_group_first_block_no(sb, group);
 669	ext2_fsblk_t group_last_block = ext2_group_last_block_no(sb, group);
 670	ext2_grpblk_t start, end;
 671	unsigned long num = 0;
 672
 673	start = 0;
 674	end = group_last_block - group_first_block + 1;
 675	/* we do allocation within the reservation window if we have a window */
 676	if (my_rsv) {
 677		if (my_rsv->_rsv_start >= group_first_block)
 678			start = my_rsv->_rsv_start - group_first_block;
 679		if (my_rsv->_rsv_end < group_last_block)
 680			end = my_rsv->_rsv_end - group_first_block + 1;
 681		if (grp_goal < start || grp_goal >= end)
 682			grp_goal = -1;
 683	}
 684	BUG_ON(start > EXT2_BLOCKS_PER_GROUP(sb));
 685
 686	if (grp_goal < 0) {
 687		grp_goal = find_next_usable_block(start, bitmap_bh, end);
 688		if (grp_goal < 0)
 689			goto fail_access;
 690		if (!my_rsv) {
 691			int i;
 692
 693			for (i = 0; i < 7 && grp_goal > start &&
 694					!ext2_test_bit(grp_goal - 1,
 695					     		bitmap_bh->b_data);
 696			     		i++, grp_goal--)
 697				;
 698		}
 699	}
 700
 701	for (; num < *count && grp_goal < end; grp_goal++) {
 702		if (ext2_set_bit_atomic(sb_bgl_lock(EXT2_SB(sb), group),
 703					grp_goal, bitmap_bh->b_data)) {
 704			if (num == 0)
 705				continue;
 706			break;
 707		}
 708		num++;
 709	}
 710
 711	if (num == 0)
 712		goto fail_access;
 713
 714	*count = num;
 715	return grp_goal - num;
 716fail_access:
 717	return -1;
 718}
 719
 720/**
 721 * 	find_next_reservable_window():
 722 *		find a reservable space within the given range.
 723 *		It does not allocate the reservation window for now:
 724 *		alloc_new_reservation() will do the work later.
 725 *
 726 * 	@search_head: the head of the searching list;
 727 *		This is not necessarily the list head of the whole filesystem
 728 *
 729 *		We have both head and start_block to assist the search
 730 *		for the reservable space. The list starts from head,
 731 *		but we will shift to the place where start_block is,
 732 *		then start from there, when looking for a reservable space.
 733 *
 734 *	@sb: the super block.
 735 *
 736 * 	@start_block: the first block we consider to start the real search from
 737 *
 738 * 	@last_block:
 739 *		the maximum block number that our goal reservable space
 740 *		could start from. This is normally the last block in this
 741 *		group. The search will end when we found the start of next
 742 *		possible reservable space is out of this boundary.
 743 *		This could handle the cross boundary reservation window
 744 *		request.
 745 *
 746 * 	basically we search from the given range, rather than the whole
 747 * 	reservation double linked list, (start_block, last_block)
 748 * 	to find a free region that is of my size and has not
 749 * 	been reserved.
 750 *
 
 
 751 */
 752static int find_next_reservable_window(
 753				struct ext2_reserve_window_node *search_head,
 754				struct ext2_reserve_window_node *my_rsv,
 755				struct super_block * sb,
 756				ext2_fsblk_t start_block,
 757				ext2_fsblk_t last_block)
 758{
 759	struct rb_node *next;
 760	struct ext2_reserve_window_node *rsv, *prev;
 761	ext2_fsblk_t cur;
 762	int size = my_rsv->rsv_goal_size;
 763
 764	/* TODO: make the start of the reservation window byte-aligned */
 765	/* cur = *start_block & ~7;*/
 766	cur = start_block;
 767	rsv = search_head;
 768	if (!rsv)
 769		return -1;
 770
 771	while (1) {
 772		if (cur <= rsv->rsv_end)
 773			cur = rsv->rsv_end + 1;
 774
 775		/* TODO?
 776		 * in the case we could not find a reservable space
 777		 * that is what is expected, during the re-search, we could
 778		 * remember what's the largest reservable space we could have
 779		 * and return that one.
 780		 *
 781		 * For now it will fail if we could not find the reservable
 782		 * space with expected-size (or more)...
 783		 */
 784		if (cur > last_block)
 785			return -1;		/* fail */
 786
 787		prev = rsv;
 788		next = rb_next(&rsv->rsv_node);
 789		rsv = rb_entry(next,struct ext2_reserve_window_node,rsv_node);
 790
 791		/*
 792		 * Reached the last reservation, we can just append to the
 793		 * previous one.
 794		 */
 795		if (!next)
 796			break;
 797
 798		if (cur + size <= rsv->rsv_start) {
 799			/*
 800			 * Found a reserveable space big enough.  We could
 801			 * have a reservation across the group boundary here
 802		 	 */
 803			break;
 804		}
 805	}
 806	/*
 807	 * we come here either :
 808	 * when we reach the end of the whole list,
 809	 * and there is empty reservable space after last entry in the list.
 810	 * append it to the end of the list.
 811	 *
 812	 * or we found one reservable space in the middle of the list,
 813	 * return the reservation window that we could append to.
 814	 * succeed.
 815	 */
 816
 817	if ((prev != my_rsv) && (!rsv_is_empty(&my_rsv->rsv_window)))
 818		rsv_window_remove(sb, my_rsv);
 819
 820	/*
 821	 * Let's book the whole available window for now.  We will check the
 822	 * disk bitmap later and then, if there are free blocks then we adjust
 823	 * the window size if it's larger than requested.
 824	 * Otherwise, we will remove this node from the tree next time
 825	 * call find_next_reservable_window.
 826	 */
 827	my_rsv->rsv_start = cur;
 828	my_rsv->rsv_end = cur + size - 1;
 829	my_rsv->rsv_alloc_hit = 0;
 830
 831	if (prev != my_rsv)
 832		ext2_rsv_window_add(sb, my_rsv);
 833
 834	return 0;
 835}
 836
 837/**
 838 * 	alloc_new_reservation()--allocate a new reservation window
 839 *
 840 *		To make a new reservation, we search part of the filesystem
 841 *		reservation list (the list that inside the group). We try to
 842 *		allocate a new reservation window near the allocation goal,
 843 *		or the beginning of the group, if there is no goal.
 844 *
 845 *		We first find a reservable space after the goal, then from
 846 *		there, we check the bitmap for the first free block after
 847 *		it. If there is no free block until the end of group, then the
 848 *		whole group is full, we failed. Otherwise, check if the free
 849 *		block is inside the expected reservable space, if so, we
 850 *		succeed.
 851 *		If the first free block is outside the reservable space, then
 852 *		start from the first free block, we search for next available
 853 *		space, and go on.
 854 *
 855 *	on succeed, a new reservation will be found and inserted into the list
 856 *	It contains at least one free block, and it does not overlap with other
 857 *	reservation windows.
 858 *
 859 *	failed: we failed to find a reservation window in this group
 860 *
 861 *	@my_rsv: the reservation
 862 *
 863 *	@grp_goal: The goal (group-relative).  It is where the search for a
 864 *		free reservable space should start from.
 865 *		if we have a goal(goal >0 ), then start from there,
 866 *		no goal(goal = -1), we start from the first block
 867 *		of the group.
 868 *
 869 *	@sb: the super block
 870 *	@group: the group we are trying to allocate in
 871 *	@bitmap_bh: the block group block bitmap
 872 *
 
 
 873 */
 874static int alloc_new_reservation(struct ext2_reserve_window_node *my_rsv,
 875		ext2_grpblk_t grp_goal, struct super_block *sb,
 876		unsigned int group, struct buffer_head *bitmap_bh)
 877{
 878	struct ext2_reserve_window_node *search_head;
 879	ext2_fsblk_t group_first_block, group_end_block, start_block;
 880	ext2_grpblk_t first_free_block;
 881	struct rb_root *fs_rsv_root = &EXT2_SB(sb)->s_rsv_window_root;
 882	unsigned long size;
 883	int ret;
 884	spinlock_t *rsv_lock = &EXT2_SB(sb)->s_rsv_window_lock;
 885
 886	group_first_block = ext2_group_first_block_no(sb, group);
 887	group_end_block = ext2_group_last_block_no(sb, group);
 888
 889	if (grp_goal < 0)
 890		start_block = group_first_block;
 891	else
 892		start_block = grp_goal + group_first_block;
 893
 894	size = my_rsv->rsv_goal_size;
 895
 896	if (!rsv_is_empty(&my_rsv->rsv_window)) {
 897		/*
 898		 * if the old reservation is cross group boundary
 899		 * and if the goal is inside the old reservation window,
 900		 * we will come here when we just failed to allocate from
 901		 * the first part of the window. We still have another part
 902		 * that belongs to the next group. In this case, there is no
 903		 * point to discard our window and try to allocate a new one
 904		 * in this group(which will fail). we should
 905		 * keep the reservation window, just simply move on.
 906		 *
 907		 * Maybe we could shift the start block of the reservation
 908		 * window to the first block of next group.
 909		 */
 910
 911		if ((my_rsv->rsv_start <= group_end_block) &&
 912				(my_rsv->rsv_end > group_end_block) &&
 913				(start_block >= my_rsv->rsv_start))
 914			return -1;
 915
 916		if ((my_rsv->rsv_alloc_hit >
 917		     (my_rsv->rsv_end - my_rsv->rsv_start + 1) / 2)) {
 918			/*
 919			 * if the previously allocation hit ratio is
 920			 * greater than 1/2, then we double the size of
 921			 * the reservation window the next time,
 922			 * otherwise we keep the same size window
 923			 */
 924			size = size * 2;
 925			if (size > EXT2_MAX_RESERVE_BLOCKS)
 926				size = EXT2_MAX_RESERVE_BLOCKS;
 927			my_rsv->rsv_goal_size= size;
 928		}
 929	}
 930
 931	spin_lock(rsv_lock);
 932	/*
 933	 * shift the search start to the window near the goal block
 934	 */
 935	search_head = search_reserve_window(fs_rsv_root, start_block);
 936
 937	/*
 938	 * find_next_reservable_window() simply finds a reservable window
 939	 * inside the given range(start_block, group_end_block).
 940	 *
 941	 * To make sure the reservation window has a free bit inside it, we
 942	 * need to check the bitmap after we found a reservable window.
 943	 */
 944retry:
 945	ret = find_next_reservable_window(search_head, my_rsv, sb,
 946						start_block, group_end_block);
 947
 948	if (ret == -1) {
 949		if (!rsv_is_empty(&my_rsv->rsv_window))
 950			rsv_window_remove(sb, my_rsv);
 951		spin_unlock(rsv_lock);
 952		return -1;
 953	}
 954
 955	/*
 956	 * On success, find_next_reservable_window() returns the
 957	 * reservation window where there is a reservable space after it.
 958	 * Before we reserve this reservable space, we need
 959	 * to make sure there is at least a free block inside this region.
 960	 *
 961	 * Search the first free bit on the block bitmap.  Search starts from
 962	 * the start block of the reservable space we just found.
 963	 */
 964	spin_unlock(rsv_lock);
 965	first_free_block = bitmap_search_next_usable_block(
 966			my_rsv->rsv_start - group_first_block,
 967			bitmap_bh, group_end_block - group_first_block + 1);
 968
 969	if (first_free_block < 0) {
 970		/*
 971		 * no free block left on the bitmap, no point
 972		 * to reserve the space. return failed.
 973		 */
 974		spin_lock(rsv_lock);
 975		if (!rsv_is_empty(&my_rsv->rsv_window))
 976			rsv_window_remove(sb, my_rsv);
 977		spin_unlock(rsv_lock);
 978		return -1;		/* failed */
 979	}
 980
 981	start_block = first_free_block + group_first_block;
 982	/*
 983	 * check if the first free block is within the
 984	 * free space we just reserved
 985	 */
 986	if (start_block >= my_rsv->rsv_start && start_block <= my_rsv->rsv_end)
 987		return 0;		/* success */
 988	/*
 989	 * if the first free bit we found is out of the reservable space
 990	 * continue search for next reservable space,
 991	 * start from where the free block is,
 992	 * we also shift the list head to where we stopped last time
 993	 */
 994	search_head = my_rsv;
 995	spin_lock(rsv_lock);
 996	goto retry;
 997}
 998
 999/**
1000 * try_to_extend_reservation()
1001 * @my_rsv:		given reservation window
1002 * @sb:			super block
1003 * @size:		the delta to extend
1004 *
1005 * Attempt to expand the reservation window large enough to have
1006 * required number of free blocks
1007 *
1008 * Since ext2_try_to_allocate() will always allocate blocks within
1009 * the reservation window range, if the window size is too small,
1010 * multiple blocks allocation has to stop at the end of the reservation
1011 * window. To make this more efficient, given the total number of
1012 * blocks needed and the current size of the window, we try to
1013 * expand the reservation window size if necessary on a best-effort
1014 * basis before ext2_new_blocks() tries to allocate blocks.
1015 */
1016static void try_to_extend_reservation(struct ext2_reserve_window_node *my_rsv,
1017			struct super_block *sb, int size)
1018{
1019	struct ext2_reserve_window_node *next_rsv;
1020	struct rb_node *next;
1021	spinlock_t *rsv_lock = &EXT2_SB(sb)->s_rsv_window_lock;
1022
1023	if (!spin_trylock(rsv_lock))
1024		return;
1025
1026	next = rb_next(&my_rsv->rsv_node);
1027
1028	if (!next)
1029		my_rsv->rsv_end += size;
1030	else {
1031		next_rsv = rb_entry(next, struct ext2_reserve_window_node, rsv_node);
1032
1033		if ((next_rsv->rsv_start - my_rsv->rsv_end - 1) >= size)
1034			my_rsv->rsv_end += size;
1035		else
1036			my_rsv->rsv_end = next_rsv->rsv_start - 1;
1037	}
1038	spin_unlock(rsv_lock);
1039}
1040
1041/**
1042 * ext2_try_to_allocate_with_rsv()
1043 * @sb:			superblock
1044 * @group:		given allocation block group
1045 * @bitmap_bh:		bufferhead holds the block bitmap
1046 * @grp_goal:		given target block within the group
1047 * @count:		target number of blocks to allocate
1048 * @my_rsv:		reservation window
1049 *
1050 * This is the main function used to allocate a new block and its reservation
1051 * window.
1052 *
1053 * Each time when a new block allocation is need, first try to allocate from
1054 * its own reservation.  If it does not have a reservation window, instead of
1055 * looking for a free bit on bitmap first, then look up the reservation list to
1056 * see if it is inside somebody else's reservation window, we try to allocate a
1057 * reservation window for it starting from the goal first. Then do the block
1058 * allocation within the reservation window.
1059 *
1060 * This will avoid keeping on searching the reservation list again and
1061 * again when somebody is looking for a free block (without
1062 * reservation), and there are lots of free blocks, but they are all
1063 * being reserved.
1064 *
1065 * We use a red-black tree for the per-filesystem reservation list.
1066 */
1067static ext2_grpblk_t
1068ext2_try_to_allocate_with_rsv(struct super_block *sb, unsigned int group,
1069			struct buffer_head *bitmap_bh, ext2_grpblk_t grp_goal,
1070			struct ext2_reserve_window_node * my_rsv,
1071			unsigned long *count)
1072{
1073	ext2_fsblk_t group_first_block, group_last_block;
1074	ext2_grpblk_t ret = 0;
1075	unsigned long num = *count;
1076
1077	/*
1078	 * we don't deal with reservation when
1079	 * filesystem is mounted without reservation
1080	 * or the file is not a regular file
1081	 * or last attempt to allocate a block with reservation turned on failed
1082	 */
1083	if (my_rsv == NULL) {
1084		return ext2_try_to_allocate(sb, group, bitmap_bh,
1085						grp_goal, count, NULL);
1086	}
1087	/*
1088	 * grp_goal is a group relative block number (if there is a goal)
1089	 * 0 <= grp_goal < EXT2_BLOCKS_PER_GROUP(sb)
1090	 * first block is a filesystem wide block number
1091	 * first block is the block number of the first block in this group
1092	 */
1093	group_first_block = ext2_group_first_block_no(sb, group);
1094	group_last_block = ext2_group_last_block_no(sb, group);
1095
1096	/*
1097	 * Basically we will allocate a new block from inode's reservation
1098	 * window.
1099	 *
1100	 * We need to allocate a new reservation window, if:
1101	 * a) inode does not have a reservation window; or
1102	 * b) last attempt to allocate a block from existing reservation
1103	 *    failed; or
1104	 * c) we come here with a goal and with a reservation window
1105	 *
1106	 * We do not need to allocate a new reservation window if we come here
1107	 * at the beginning with a goal and the goal is inside the window, or
1108	 * we don't have a goal but already have a reservation window.
1109	 * then we could go to allocate from the reservation window directly.
1110	 */
1111	while (1) {
1112		if (rsv_is_empty(&my_rsv->rsv_window) || (ret < 0) ||
1113			!goal_in_my_reservation(&my_rsv->rsv_window,
1114						grp_goal, group, sb)) {
1115			if (my_rsv->rsv_goal_size < *count)
1116				my_rsv->rsv_goal_size = *count;
1117			ret = alloc_new_reservation(my_rsv, grp_goal, sb,
1118							group, bitmap_bh);
1119			if (ret < 0)
1120				break;			/* failed */
1121
1122			if (!goal_in_my_reservation(&my_rsv->rsv_window,
1123							grp_goal, group, sb))
1124				grp_goal = -1;
1125		} else if (grp_goal >= 0) {
1126			int curr = my_rsv->rsv_end -
1127					(grp_goal + group_first_block) + 1;
1128
1129			if (curr < *count)
1130				try_to_extend_reservation(my_rsv, sb,
1131							*count - curr);
1132		}
1133
1134		if ((my_rsv->rsv_start > group_last_block) ||
1135				(my_rsv->rsv_end < group_first_block)) {
 
 
 
 
 
1136			rsv_window_dump(&EXT2_SB(sb)->s_rsv_window_root, 1);
1137			BUG();
1138		}
1139		ret = ext2_try_to_allocate(sb, group, bitmap_bh, grp_goal,
1140					   &num, &my_rsv->rsv_window);
1141		if (ret >= 0) {
1142			my_rsv->rsv_alloc_hit += num;
1143			*count = num;
1144			break;				/* succeed */
1145		}
1146		num = *count;
1147	}
1148	return ret;
1149}
1150
1151/**
1152 * ext2_has_free_blocks()
1153 * @sbi:		in-core super block structure.
1154 *
1155 * Check if filesystem has at least 1 free block available for allocation.
1156 */
1157static int ext2_has_free_blocks(struct ext2_sb_info *sbi)
1158{
1159	ext2_fsblk_t free_blocks, root_blocks;
1160
1161	free_blocks = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
1162	root_blocks = le32_to_cpu(sbi->s_es->s_r_blocks_count);
1163	if (free_blocks < root_blocks + 1 && !capable(CAP_SYS_RESOURCE) &&
1164		!uid_eq(sbi->s_resuid, current_fsuid()) &&
1165		(gid_eq(sbi->s_resgid, GLOBAL_ROOT_GID) ||
1166		 !in_group_p (sbi->s_resgid))) {
1167		return 0;
1168	}
1169	return 1;
1170}
1171
1172/*
1173 * Returns 1 if the passed-in block region is valid; 0 if some part overlaps
1174 * with filesystem metadata blocks.
1175 */
1176int ext2_data_block_valid(struct ext2_sb_info *sbi, ext2_fsblk_t start_blk,
1177			  unsigned int count)
1178{
1179	if ((start_blk <= le32_to_cpu(sbi->s_es->s_first_data_block)) ||
1180	    (start_blk + count - 1 < start_blk) ||
1181	    (start_blk + count - 1 >= le32_to_cpu(sbi->s_es->s_blocks_count)))
1182		return 0;
1183
1184	/* Ensure we do not step over superblock */
1185	if ((start_blk <= sbi->s_sb_block) &&
1186	    (start_blk + count - 1 >= sbi->s_sb_block))
1187		return 0;
1188
1189	return 1;
1190}
1191
1192/*
1193 * ext2_new_blocks() -- core block(s) allocation function
1194 * @inode:		file inode
1195 * @goal:		given target block(filesystem wide)
1196 * @count:		target number of blocks to allocate
1197 * @errp:		error code
 
1198 *
1199 * ext2_new_blocks uses a goal block to assist allocation.  If the goal is
1200 * free, or there is a free block within 32 blocks of the goal, that block
1201 * is allocated.  Otherwise a forward search is made for a free block; within 
1202 * each block group the search first looks for an entire free byte in the block
1203 * bitmap, and then for any free bit if that fails.
1204 * This function also updates quota and i_blocks field.
1205 */
1206ext2_fsblk_t ext2_new_blocks(struct inode *inode, ext2_fsblk_t goal,
1207		    unsigned long *count, int *errp)
1208{
1209	struct buffer_head *bitmap_bh = NULL;
1210	struct buffer_head *gdp_bh;
1211	int group_no;
1212	int goal_group;
1213	ext2_grpblk_t grp_target_blk;	/* blockgroup relative goal block */
1214	ext2_grpblk_t grp_alloc_blk;	/* blockgroup-relative allocated block*/
1215	ext2_fsblk_t ret_block;		/* filesyetem-wide allocated block */
1216	int bgi;			/* blockgroup iteration index */
1217	int performed_allocation = 0;
1218	ext2_grpblk_t free_blocks;	/* number of free blocks in a group */
1219	struct super_block *sb;
1220	struct ext2_group_desc *gdp;
1221	struct ext2_super_block *es;
1222	struct ext2_sb_info *sbi;
1223	struct ext2_reserve_window_node *my_rsv = NULL;
1224	struct ext2_block_alloc_info *block_i;
1225	unsigned short windowsz = 0;
1226	unsigned long ngroups;
1227	unsigned long num = *count;
1228	int ret;
1229
1230	*errp = -ENOSPC;
1231	sb = inode->i_sb;
1232
1233	/*
1234	 * Check quota for allocation of this block.
1235	 */
1236	ret = dquot_alloc_block(inode, num);
1237	if (ret) {
1238		*errp = ret;
1239		return 0;
1240	}
1241
1242	sbi = EXT2_SB(sb);
1243	es = EXT2_SB(sb)->s_es;
1244	ext2_debug("goal=%lu.\n", goal);
1245	/*
1246	 * Allocate a block from reservation only when
1247	 * filesystem is mounted with reservation(default,-o reservation), and
1248	 * it's a regular file, and
1249	 * the desired window size is greater than 0 (One could use ioctl
1250	 * command EXT2_IOC_SETRSVSZ to set the window size to 0 to turn off
1251	 * reservation on that particular file)
1252	 */
1253	block_i = EXT2_I(inode)->i_block_alloc_info;
1254	if (block_i) {
1255		windowsz = block_i->rsv_window_node.rsv_goal_size;
1256		if (windowsz > 0)
1257			my_rsv = &block_i->rsv_window_node;
1258	}
1259
1260	if (!ext2_has_free_blocks(sbi)) {
1261		*errp = -ENOSPC;
1262		goto out;
1263	}
1264
1265	/*
1266	 * First, test whether the goal block is free.
1267	 */
1268	if (goal < le32_to_cpu(es->s_first_data_block) ||
1269	    goal >= le32_to_cpu(es->s_blocks_count))
1270		goal = le32_to_cpu(es->s_first_data_block);
1271	group_no = (goal - le32_to_cpu(es->s_first_data_block)) /
1272			EXT2_BLOCKS_PER_GROUP(sb);
1273	goal_group = group_no;
1274retry_alloc:
1275	gdp = ext2_get_group_desc(sb, group_no, &gdp_bh);
1276	if (!gdp)
1277		goto io_error;
1278
1279	free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
1280	/*
1281	 * if there is not enough free blocks to make a new resevation
1282	 * turn off reservation for this allocation
1283	 */
1284	if (my_rsv && (free_blocks < windowsz)
1285		&& (free_blocks > 0)
1286		&& (rsv_is_empty(&my_rsv->rsv_window)))
1287		my_rsv = NULL;
1288
1289	if (free_blocks > 0) {
1290		grp_target_blk = ((goal - le32_to_cpu(es->s_first_data_block)) %
1291				EXT2_BLOCKS_PER_GROUP(sb));
1292		/*
1293		 * In case we retry allocation (due to fs reservation not
1294		 * working out or fs corruption), the bitmap_bh is non-null
1295		 * pointer and we have to release it before calling
1296		 * read_block_bitmap().
1297		 */
1298		brelse(bitmap_bh);
1299		bitmap_bh = read_block_bitmap(sb, group_no);
1300		if (!bitmap_bh)
1301			goto io_error;
1302		grp_alloc_blk = ext2_try_to_allocate_with_rsv(sb, group_no,
1303					bitmap_bh, grp_target_blk,
1304					my_rsv, &num);
1305		if (grp_alloc_blk >= 0)
1306			goto allocated;
1307	}
1308
1309	ngroups = EXT2_SB(sb)->s_groups_count;
1310	smp_rmb();
1311
1312	/*
1313	 * Now search the rest of the groups.  We assume that
1314	 * group_no and gdp correctly point to the last group visited.
1315	 */
1316	for (bgi = 0; bgi < ngroups; bgi++) {
1317		group_no++;
1318		if (group_no >= ngroups)
1319			group_no = 0;
1320		gdp = ext2_get_group_desc(sb, group_no, &gdp_bh);
1321		if (!gdp)
1322			goto io_error;
1323
1324		free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
1325		/*
1326		 * skip this group (and avoid loading bitmap) if there
1327		 * are no free blocks
1328		 */
1329		if (!free_blocks)
1330			continue;
1331		/*
1332		 * skip this group if the number of
1333		 * free blocks is less than half of the reservation
1334		 * window size.
1335		 */
1336		if (my_rsv && (free_blocks <= (windowsz/2)))
1337			continue;
1338
1339		brelse(bitmap_bh);
1340		bitmap_bh = read_block_bitmap(sb, group_no);
1341		if (!bitmap_bh)
1342			goto io_error;
1343		/*
1344		 * try to allocate block(s) from this group, without a goal(-1).
1345		 */
1346		grp_alloc_blk = ext2_try_to_allocate_with_rsv(sb, group_no,
1347					bitmap_bh, -1, my_rsv, &num);
1348		if (grp_alloc_blk >= 0)
1349			goto allocated;
1350	}
1351	/*
1352	 * We may end up a bogus earlier ENOSPC error due to
1353	 * filesystem is "full" of reservations, but
1354	 * there maybe indeed free blocks available on disk
1355	 * In this case, we just forget about the reservations
1356	 * just do block allocation as without reservations.
1357	 */
1358	if (my_rsv) {
1359		my_rsv = NULL;
1360		windowsz = 0;
1361		group_no = goal_group;
1362		goto retry_alloc;
1363	}
1364	/* No space left on the device */
1365	*errp = -ENOSPC;
1366	goto out;
1367
1368allocated:
1369
1370	ext2_debug("using block group %d(%d)\n",
1371			group_no, gdp->bg_free_blocks_count);
1372
1373	ret_block = grp_alloc_blk + ext2_group_first_block_no(sb, group_no);
1374
1375	if (in_range(le32_to_cpu(gdp->bg_block_bitmap), ret_block, num) ||
1376	    in_range(le32_to_cpu(gdp->bg_inode_bitmap), ret_block, num) ||
1377	    in_range(ret_block, le32_to_cpu(gdp->bg_inode_table),
1378		      EXT2_SB(sb)->s_itb_per_group) ||
1379	    in_range(ret_block + num - 1, le32_to_cpu(gdp->bg_inode_table),
1380		      EXT2_SB(sb)->s_itb_per_group)) {
1381		ext2_error(sb, "ext2_new_blocks",
1382			    "Allocating block in system zone - "
1383			    "blocks from "E2FSBLK", length %lu",
1384			    ret_block, num);
1385		/*
1386		 * ext2_try_to_allocate marked the blocks we allocated as in
1387		 * use.  So we may want to selectively mark some of the blocks
1388		 * as free
1389		 */
1390		num = *count;
1391		goto retry_alloc;
1392	}
1393
1394	performed_allocation = 1;
1395
1396	if (ret_block + num - 1 >= le32_to_cpu(es->s_blocks_count)) {
1397		ext2_error(sb, "ext2_new_blocks",
1398			    "block("E2FSBLK") >= blocks count(%d) - "
1399			    "block_group = %d, es == %p ", ret_block,
1400			le32_to_cpu(es->s_blocks_count), group_no, es);
1401		goto out;
1402	}
1403
1404	group_adjust_blocks(sb, group_no, gdp, gdp_bh, -num);
1405	percpu_counter_sub(&sbi->s_freeblocks_counter, num);
1406
1407	mark_buffer_dirty(bitmap_bh);
1408	if (sb->s_flags & SB_SYNCHRONOUS)
1409		sync_dirty_buffer(bitmap_bh);
1410
1411	*errp = 0;
1412	brelse(bitmap_bh);
1413	if (num < *count) {
1414		dquot_free_block_nodirty(inode, *count-num);
1415		mark_inode_dirty(inode);
1416		*count = num;
1417	}
1418	return ret_block;
1419
1420io_error:
1421	*errp = -EIO;
1422out:
1423	/*
1424	 * Undo the block allocation
1425	 */
1426	if (!performed_allocation) {
1427		dquot_free_block_nodirty(inode, *count);
1428		mark_inode_dirty(inode);
1429	}
1430	brelse(bitmap_bh);
1431	return 0;
1432}
1433
1434ext2_fsblk_t ext2_new_block(struct inode *inode, unsigned long goal, int *errp)
1435{
1436	unsigned long count = 1;
1437
1438	return ext2_new_blocks(inode, goal, &count, errp);
1439}
1440
1441#ifdef EXT2FS_DEBUG
1442
1443unsigned long ext2_count_free(struct buffer_head *map, unsigned int numchars)
1444{
1445	return numchars * BITS_PER_BYTE - memweight(map->b_data, numchars);
1446}
1447
1448#endif  /*  EXT2FS_DEBUG  */
1449
1450unsigned long ext2_count_free_blocks (struct super_block * sb)
1451{
1452	struct ext2_group_desc * desc;
1453	unsigned long desc_count = 0;
1454	int i;
1455#ifdef EXT2FS_DEBUG
1456	unsigned long bitmap_count, x;
1457	struct ext2_super_block *es;
1458
1459	es = EXT2_SB(sb)->s_es;
1460	desc_count = 0;
1461	bitmap_count = 0;
1462	desc = NULL;
1463	for (i = 0; i < EXT2_SB(sb)->s_groups_count; i++) {
1464		struct buffer_head *bitmap_bh;
1465		desc = ext2_get_group_desc (sb, i, NULL);
1466		if (!desc)
1467			continue;
1468		desc_count += le16_to_cpu(desc->bg_free_blocks_count);
1469		bitmap_bh = read_block_bitmap(sb, i);
1470		if (!bitmap_bh)
1471			continue;
1472		
1473		x = ext2_count_free(bitmap_bh, sb->s_blocksize);
1474		printk ("group %d: stored = %d, counted = %lu\n",
1475			i, le16_to_cpu(desc->bg_free_blocks_count), x);
1476		bitmap_count += x;
1477		brelse(bitmap_bh);
1478	}
1479	printk("ext2_count_free_blocks: stored = %lu, computed = %lu, %lu\n",
1480		(long)le32_to_cpu(es->s_free_blocks_count),
1481		desc_count, bitmap_count);
1482	return bitmap_count;
1483#else
1484	for (i = 0; i < EXT2_SB(sb)->s_groups_count; i++) {
1485		desc = ext2_get_group_desc(sb, i, NULL);
1486		if (!desc)
1487			continue;
1488		desc_count += le16_to_cpu(desc->bg_free_blocks_count);
1489	}
1490	return desc_count;
1491#endif
1492}
1493
1494static inline int test_root(int a, int b)
1495{
1496	int num = b;
1497
1498	while (a > num)
1499		num *= b;
1500	return num == a;
1501}
1502
1503static int ext2_group_sparse(int group)
1504{
1505	if (group <= 1)
1506		return 1;
1507	return (test_root(group, 3) || test_root(group, 5) ||
1508		test_root(group, 7));
1509}
1510
1511/**
1512 *	ext2_bg_has_super - number of blocks used by the superblock in group
1513 *	@sb: superblock for filesystem
1514 *	@group: group number to check
1515 *
1516 *	Return the number of blocks used by the superblock (primary or backup)
1517 *	in this group.  Currently this will be only 0 or 1.
1518 */
1519int ext2_bg_has_super(struct super_block *sb, int group)
1520{
1521	if (EXT2_HAS_RO_COMPAT_FEATURE(sb,EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER)&&
1522	    !ext2_group_sparse(group))
1523		return 0;
1524	return 1;
1525}
1526
1527/**
1528 *	ext2_bg_num_gdb - number of blocks used by the group table in group
1529 *	@sb: superblock for filesystem
1530 *	@group: group number to check
1531 *
1532 *	Return the number of blocks used by the group descriptor table
1533 *	(primary or backup) in this group.  In the future there may be a
1534 *	different number of descriptor blocks in each group.
1535 */
1536unsigned long ext2_bg_num_gdb(struct super_block *sb, int group)
1537{
1538	return ext2_bg_has_super(sb, group) ? EXT2_SB(sb)->s_gdb_count : 0;
1539}
1540