// SPDX-License-Identifier: GPL-2.0

  /*

   *  linux/fs/ext4/balloc.c

   *
   * Copyright (C) 1992, 1993, 1994, 1995
   * Remy Card (card@masi.ibp.fr)
   * Laboratoire MASI - Institut Blaise Pascal
   * Universite Pierre et Marie Curie (Paris VI)
   *
   *  Enhanced block allocation by Stephen Tweedie (sct@redhat.com), 1993
   *  Big-endian to little-endian byte-swapping/bitmaps by
   *        David S. Miller (davem@caip.rutgers.edu), 1995
   */
  
  #include <linux/time.h>
  #include <linux/capability.h>
  #include <linux/fs.h>

  #include <linux/quotaops.h>
  #include <linux/buffer_head.h>

  #include "ext4.h"
  #include "ext4_jbd2.h"

  #include "mballoc.h"

  #include <trace/events/ext4.h>

  static unsigned ext4_num_base_meta_clusters(struct super_block *sb,
  					    ext4_group_t block_group);

  /*
   * balloc.c contains the blocks allocation and deallocation routines
   */
  
  /*

   * Calculate block group number for a given block number
   */
  ext4_group_t ext4_get_group_number(struct super_block *sb,
  				   ext4_fsblk_t block)
  {
  	ext4_group_t group;
  
  	if (test_opt2(sb, STD_GROUP_SIZE))

  		group = (block -
  			 le32_to_cpu(EXT4_SB(sb)->s_es->s_first_data_block)) >>

  			(EXT4_BLOCK_SIZE_BITS(sb) + EXT4_CLUSTER_BITS(sb) + 3);
  	else
  		ext4_get_group_no_and_offset(sb, block, &group, NULL);
  	return group;
  }
  
  /*

   * Calculate the block group number and offset into the block/cluster
   * allocation bitmap, given a block number

   */
  void ext4_get_group_no_and_offset(struct super_block *sb, ext4_fsblk_t blocknr,

  		ext4_group_t *blockgrpp, ext4_grpblk_t *offsetp)

  {

  	struct ext4_super_block *es = EXT4_SB(sb)->s_es;

  	ext4_grpblk_t offset;

  	blocknr = blocknr - le32_to_cpu(es->s_first_data_block);

  	offset = do_div(blocknr, EXT4_BLOCKS_PER_GROUP(sb)) >>
  		EXT4_SB(sb)->s_cluster_bits;

  	if (offsetp)
  		*offsetp = offset;
  	if (blockgrpp)

  		*blockgrpp = blocknr;

  
  }

  /*
   * Check whether the 'block' lives within the 'block_group'. Returns 1 if so
   * and 0 otherwise.
   */
  static inline int ext4_block_in_group(struct super_block *sb,
  				      ext4_fsblk_t block,
  				      ext4_group_t block_group)

  {
  	ext4_group_t actual_group;

  	actual_group = ext4_get_group_number(sb, block);

  	return (actual_group == block_group) ? 1 : 0;

  }

  /* Return the number of clusters used for file system metadata; this
   * represents the overhead needed by the file system.
   */

  static unsigned ext4_num_overhead_clusters(struct super_block *sb,
  					   ext4_group_t block_group,
  					   struct ext4_group_desc *gdp)

  {

  	unsigned num_clusters;
  	int block_cluster = -1, inode_cluster = -1, itbl_cluster = -1, i, c;
  	ext4_fsblk_t start = ext4_group_first_block_no(sb, block_group);
  	ext4_fsblk_t itbl_blk;

  	struct ext4_sb_info *sbi = EXT4_SB(sb);

  	/* This is the number of clusters used by the superblock,
  	 * block group descriptors, and reserved block group
  	 * descriptor blocks */
  	num_clusters = ext4_num_base_meta_clusters(sb, block_group);
  
  	/*
  	 * For the allocation bitmaps and inode table, we first need
  	 * to check to see if the block is in the block group.  If it
  	 * is, then check to see if the cluster is already accounted
  	 * for in the clusters used for the base metadata cluster, or
  	 * if we can increment the base metadata cluster to include
  	 * that block.  Otherwise, we will have to track the cluster
  	 * used for the allocation bitmap or inode table explicitly.
  	 * Normally all of these blocks are contiguous, so the special
  	 * case handling shouldn't be necessary except for *very*
  	 * unusual file system layouts.
  	 */
  	if (ext4_block_in_group(sb, ext4_block_bitmap(sb, gdp), block_group)) {

  		block_cluster = EXT4_B2C(sbi,
  					 ext4_block_bitmap(sb, gdp) - start);

  		if (block_cluster < num_clusters)
  			block_cluster = -1;
  		else if (block_cluster == num_clusters) {
  			num_clusters++;
  			block_cluster = -1;
  		}
  	}
  
  	if (ext4_block_in_group(sb, ext4_inode_bitmap(sb, gdp), block_group)) {
  		inode_cluster = EXT4_B2C(sbi,

  					 ext4_inode_bitmap(sb, gdp) - start);

  		if (inode_cluster < num_clusters)
  			inode_cluster = -1;
  		else if (inode_cluster == num_clusters) {
  			num_clusters++;
  			inode_cluster = -1;
  		}
  	}
  
  	itbl_blk = ext4_inode_table(sb, gdp);
  	for (i = 0; i < sbi->s_itb_per_group; i++) {
  		if (ext4_block_in_group(sb, itbl_blk + i, block_group)) {

  			c = EXT4_B2C(sbi, itbl_blk + i - start);

  			if ((c < num_clusters) || (c == inode_cluster) ||
  			    (c == block_cluster) || (c == itbl_cluster))
  				continue;
  			if (c == num_clusters) {
  				num_clusters++;
  				continue;
  			}
  			num_clusters++;
  			itbl_cluster = c;

  		}
  	}

  
  	if (block_cluster != -1)
  		num_clusters++;
  	if (inode_cluster != -1)
  		num_clusters++;
  
  	return num_clusters;

  }

  static unsigned int num_clusters_in_group(struct super_block *sb,
  					  ext4_group_t block_group)

  {

  	unsigned int blocks;

  	if (block_group == ext4_get_groups_count(sb) - 1) {
  		/*
  		 * Even though mke2fs always initializes the first and
  		 * last group, just in case some other tool was used,
  		 * we need to make sure we calculate the right free
  		 * blocks.
  		 */

  		blocks = ext4_blocks_count(EXT4_SB(sb)->s_es) -

  			ext4_group_first_block_no(sb, block_group);
  	} else

  		blocks = EXT4_BLOCKS_PER_GROUP(sb);
  	return EXT4_NUM_B2C(EXT4_SB(sb), blocks);

  }

  /* Initializes an uninitialized block bitmap */

  static int ext4_init_block_bitmap(struct super_block *sb,

  				   struct buffer_head *bh,
  				   ext4_group_t block_group,
  				   struct ext4_group_desc *gdp)

  {

  	unsigned int bit, bit_max;

  	struct ext4_sb_info *sbi = EXT4_SB(sb);

  	ext4_fsblk_t start, tmp;

  
  	J_ASSERT_BH(bh, buffer_locked(bh));
  
  	/* If checksum is bad mark all blocks used to prevent allocation
  	 * essentially implementing a per-group read-only flag. */

  	if (!ext4_group_desc_csum_verify(sb, block_group, gdp)) {

  		ext4_mark_group_bitmap_corrupted(sb, block_group,
  					EXT4_GROUP_INFO_BBITMAP_CORRUPT |
  					EXT4_GROUP_INFO_IBITMAP_CORRUPT);

  		return -EFSBADCRC;

  	}

  	memset(bh->b_data, 0, sb->s_blocksize);

  	bit_max = ext4_num_base_meta_clusters(sb, block_group);

  	if ((bit_max >> 3) >= bh->b_size)
  		return -EFSCORRUPTED;

  	for (bit = 0; bit < bit_max; bit++)
  		ext4_set_bit(bit, bh->b_data);

  	start = ext4_group_first_block_no(sb, block_group);

  	/* Set bits for block and inode bitmaps, and inode table */
  	tmp = ext4_block_bitmap(sb, gdp);

  	if (ext4_block_in_group(sb, tmp, block_group))

  		ext4_set_bit(EXT4_B2C(sbi, tmp - start), bh->b_data);

  	tmp = ext4_inode_bitmap(sb, gdp);

  	if (ext4_block_in_group(sb, tmp, block_group))

  		ext4_set_bit(EXT4_B2C(sbi, tmp - start), bh->b_data);

  	tmp = ext4_inode_table(sb, gdp);
  	for (; tmp < ext4_inode_table(sb, gdp) +
  		     sbi->s_itb_per_group; tmp++) {

  		if (ext4_block_in_group(sb, tmp, block_group))

  			ext4_set_bit(EXT4_B2C(sbi, tmp - start), bh->b_data);

  	}

  	/*
  	 * Also if the number of blocks within the group is less than
  	 * the blocksize * 8 ( which is the size of bitmap ), set rest
  	 * of the block bitmap to 1
  	 */

  	ext4_mark_bitmap_end(num_clusters_in_group(sb, block_group),

  			     sb->s_blocksize * 8, bh->b_data);

  	return 0;

  }

  /* Return the number of free blocks in a block group.  It is used when
   * the block bitmap is uninitialized, so we can't just count the bits
   * in the bitmap. */

  unsigned ext4_free_clusters_after_init(struct super_block *sb,
  				       ext4_group_t block_group,
  				       struct ext4_group_desc *gdp)

  {

  	return num_clusters_in_group(sb, block_group) - 
  		ext4_num_overhead_clusters(sb, block_group, gdp);

  }

  /*

   * The free blocks are managed by bitmaps.  A file system contains several
   * blocks groups.  Each group contains 1 bitmap block for blocks, 1 bitmap
   * block for inodes, N blocks for the inode table and data blocks.
   *
   * The file system contains group descriptors which are located after the
   * super block.  Each descriptor contains the number of the bitmap block and
   * the free blocks count in the block.  The descriptors are loaded in memory

   * when a file system is mounted (see ext4_fill_super).

   */

  /**

   * ext4_get_group_desc() -- load group descriptor from disk

   * @sb:			super block
   * @block_group:	given block group
   * @bh:			pointer to the buffer head to store the block
   *			group descriptor
   */

  struct ext4_group_desc * ext4_get_group_desc(struct super_block *sb,

  					     ext4_group_t block_group,

  					     struct buffer_head **bh)

  {

  	unsigned int group_desc;
  	unsigned int offset;

  	ext4_group_t ngroups = ext4_get_groups_count(sb);

  	struct ext4_group_desc *desc;

  	struct ext4_sb_info *sbi = EXT4_SB(sb);

  	struct buffer_head *bh_p;

  	if (block_group >= ngroups) {

  		ext4_error(sb, "block_group >= groups_count - block_group = %u,"
  			   " groups_count = %u", block_group, ngroups);

  
  		return NULL;
  	}

  	group_desc = block_group >> EXT4_DESC_PER_BLOCK_BITS(sb);
  	offset = block_group & (EXT4_DESC_PER_BLOCK(sb) - 1);

  	bh_p = sbi_array_rcu_deref(sbi, s_group_desc, group_desc);
  	/*
  	 * sbi_array_rcu_deref returns with rcu unlocked, this is ok since
  	 * the pointer being dereferenced won't be dereferenced again. By
  	 * looking at the usage in add_new_gdb() the value isn't modified,
  	 * just the pointer, and so it remains valid.
  	 */
  	if (!bh_p) {

  		ext4_error(sb, "Group descriptor not loaded - "

  			   "block_group = %u, group_desc = %u, desc = %u",

  			   block_group, group_desc, offset);

  		return NULL;
  	}

  	desc = (struct ext4_group_desc *)(

  		(__u8 *)bh_p->b_data +

  		offset * EXT4_DESC_SIZE(sb));

  	if (bh)

  		*bh = bh_p;

  	return desc;

  }

  /*
   * Return the block number which was discovered to be invalid, or 0 if
   * the block bitmap is valid.
   */
  static ext4_fsblk_t ext4_valid_block_bitmap(struct super_block *sb,
  					    struct ext4_group_desc *desc,

  					    ext4_group_t block_group,

  					    struct buffer_head *bh)

  {

  	struct ext4_sb_info *sbi = EXT4_SB(sb);

  	ext4_grpblk_t offset;
  	ext4_grpblk_t next_zero_bit;

  	ext4_grpblk_t max_bit = EXT4_CLUSTERS_PER_GROUP(sb);

  	ext4_fsblk_t blk;

  	ext4_fsblk_t group_first_block;

  	if (ext4_has_feature_flex_bg(sb)) {

  		/* with FLEX_BG, the inode/block bitmaps and itable
  		 * blocks may not be in the group at all
  		 * so the bitmap validation will be skipped for those groups
  		 * or it has to also read the block group where the bitmaps
  		 * are located to verify they are set.
  		 */

  		return 0;

  	}
  	group_first_block = ext4_group_first_block_no(sb, block_group);
  
  	/* check whether block bitmap block number is set */

  	blk = ext4_block_bitmap(sb, desc);
  	offset = blk - group_first_block;

  	if (offset < 0 || EXT4_B2C(sbi, offset) >= max_bit ||

  	    !ext4_test_bit(EXT4_B2C(sbi, offset), bh->b_data))

  		/* bad block bitmap */

  		return blk;

  
  	/* check whether the inode bitmap block number is set */

  	blk = ext4_inode_bitmap(sb, desc);
  	offset = blk - group_first_block;

  	if (offset < 0 || EXT4_B2C(sbi, offset) >= max_bit ||

  	    !ext4_test_bit(EXT4_B2C(sbi, offset), bh->b_data))

  		/* bad block bitmap */

  		return blk;

  
  	/* check whether the inode table block number is set */

  	blk = ext4_inode_table(sb, desc);
  	offset = blk - group_first_block;

  	if (offset < 0 || EXT4_B2C(sbi, offset) >= max_bit ||
  	    EXT4_B2C(sbi, offset + sbi->s_itb_per_group) >= max_bit)

  		return blk;

  	next_zero_bit = ext4_find_next_zero_bit(bh->b_data,

  			EXT4_B2C(sbi, offset + sbi->s_itb_per_group),

  			EXT4_B2C(sbi, offset));
  	if (next_zero_bit <

  	    EXT4_B2C(sbi, offset + sbi->s_itb_per_group))

  		/* bad bitmap for inode tables */
  		return blk;

  	return 0;
  }

  static int ext4_validate_block_bitmap(struct super_block *sb,
  				      struct ext4_group_desc *desc,
  				      ext4_group_t block_group,
  				      struct buffer_head *bh)

  {

  	ext4_fsblk_t	blk;

  	struct ext4_group_info *grp = ext4_get_group_info(sb, block_group);

  	if (buffer_verified(bh))
  		return 0;
  	if (EXT4_MB_GRP_BBITMAP_CORRUPT(grp))
  		return -EFSCORRUPTED;

  
  	ext4_lock_group(sb, block_group);

  	if (buffer_verified(bh))
  		goto verified;

  	if (unlikely(!ext4_block_bitmap_csum_verify(sb, block_group,

  						    desc, bh) ||
  		     ext4_simulate_fail(sb, EXT4_SIM_BBITMAP_CRC))) {

  		ext4_unlock_group(sb, block_group);

  		ext4_error(sb, "bg %u: bad block bitmap checksum", block_group);

  		ext4_mark_group_bitmap_corrupted(sb, block_group,
  					EXT4_GROUP_INFO_BBITMAP_CORRUPT);

  		return -EFSBADCRC;

  	}

  	blk = ext4_valid_block_bitmap(sb, desc, block_group, bh);
  	if (unlikely(blk != 0)) {

  		ext4_unlock_group(sb, block_group);

  		ext4_error(sb, "bg %u: block %llu: invalid block bitmap",
  			   block_group, blk);

  		ext4_mark_group_bitmap_corrupted(sb, block_group,
  					EXT4_GROUP_INFO_BBITMAP_CORRUPT);

  		return -EFSCORRUPTED;

  	}
  	set_buffer_verified(bh);

  verified:

  	ext4_unlock_group(sb, block_group);

  	return 0;

  }

  /**

   * ext4_read_block_bitmap_nowait()

   * @sb:			super block
   * @block_group:	given block group
   *

   * Read the bitmap for a given block_group,and validate the
   * bits for block/inode/inode tables are set in the bitmaps

   *

   * Return buffer_head on success or an ERR_PTR in case of failure.

   */

  struct buffer_head *

  ext4_read_block_bitmap_nowait(struct super_block *sb, ext4_group_t block_group)

  {

  	struct ext4_group_desc *desc;

  	struct ext4_sb_info *sbi = EXT4_SB(sb);

  	struct buffer_head *bh;

  	ext4_fsblk_t bitmap_blk;

  	int err;

  	desc = ext4_get_group_desc(sb, block_group, NULL);

  	if (!desc)

  		return ERR_PTR(-EFSCORRUPTED);

  	bitmap_blk = ext4_block_bitmap(sb, desc);

  	if ((bitmap_blk <= le32_to_cpu(sbi->s_es->s_first_data_block)) ||
  	    (bitmap_blk >= ext4_blocks_count(sbi->s_es))) {
  		ext4_error(sb, "Invalid block bitmap block %llu in "
  			   "block_group %u", bitmap_blk, block_group);

  		ext4_mark_group_bitmap_corrupted(sb, block_group,
  					EXT4_GROUP_INFO_BBITMAP_CORRUPT);

  		return ERR_PTR(-EFSCORRUPTED);
  	}

  	bh = sb_getblk(sb, bitmap_blk);
  	if (unlikely(!bh)) {

  		ext4_warning(sb, "Cannot get buffer for block bitmap - "
  			     "block_group = %u, block_bitmap = %llu",
  			     block_group, bitmap_blk);

  		return ERR_PTR(-ENOMEM);

  	}

  
  	if (bitmap_uptodate(bh))

  		goto verify;

  	lock_buffer(bh);

  	if (bitmap_uptodate(bh)) {
  		unlock_buffer(bh);

  		goto verify;

  	}

  	ext4_lock_group(sb, block_group);

  	if (ext4_has_group_desc_csum(sb) &&
  	    (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT))) {
  		if (block_group == 0) {
  			ext4_unlock_group(sb, block_group);
  			unlock_buffer(bh);
  			ext4_error(sb, "Block bitmap for bg 0 marked "
  				   "uninitialized");
  			err = -EFSCORRUPTED;
  			goto out;
  		}

  		err = ext4_init_block_bitmap(sb, bh, block_group, desc);

  		set_bitmap_uptodate(bh);

  		set_buffer_uptodate(bh);

  		set_buffer_verified(bh);

  		ext4_unlock_group(sb, block_group);

  		unlock_buffer(bh);

  		if (err) {
  			ext4_error(sb, "Failed to init block bitmap for group "
  				   "%u: %d", block_group, err);

  			goto out;

  		}

  		goto verify;

  	}

  	ext4_unlock_group(sb, block_group);

  	if (buffer_uptodate(bh)) {
  		/*
  		 * if not uninit if bh is uptodate,
  		 * bitmap is also uptodate
  		 */
  		set_bitmap_uptodate(bh);
  		unlock_buffer(bh);

  		goto verify;

  	}
  	/*

  	 * submit the buffer_head for reading

  	 */

  	set_buffer_new(bh);

  	trace_ext4_read_block_bitmap_load(sb, block_group);

  	bh->b_end_io = ext4_end_bitmap_read;
  	get_bh(bh);

  	submit_bh(REQ_OP_READ, REQ_META | REQ_PRIO, bh);

  	return bh;

  verify:

  	err = ext4_validate_block_bitmap(sb, desc, block_group, bh);
  	if (err)
  		goto out;
  	return bh;
  out:

  	put_bh(bh);

  	return ERR_PTR(err);

  }

  /* Returns 0 on success, -errno on error */

  int ext4_wait_block_bitmap(struct super_block *sb, ext4_group_t block_group,
  			   struct buffer_head *bh)
  {
  	struct ext4_group_desc *desc;
  
  	if (!buffer_new(bh))
  		return 0;
  	desc = ext4_get_group_desc(sb, block_group, NULL);
  	if (!desc)

  		return -EFSCORRUPTED;

  	wait_on_buffer(bh);

  	ext4_simulate_fail_bh(sb, bh, EXT4_SIM_BBITMAP_EIO);

  	if (!buffer_uptodate(bh)) {

  		ext4_error_err(sb, EIO, "Cannot read block bitmap - "
  			       "block_group = %u, block_bitmap = %llu",
  			       block_group, (unsigned long long) bh->b_blocknr);

  		ext4_mark_group_bitmap_corrupted(sb, block_group,
  					EXT4_GROUP_INFO_BBITMAP_CORRUPT);

  		return -EIO;

  	}

  	clear_buffer_new(bh);
  	/* Panic or remount fs read-only if block bitmap is invalid */

  	return ext4_validate_block_bitmap(sb, desc, block_group, bh);

  }
  
  struct buffer_head *
  ext4_read_block_bitmap(struct super_block *sb, ext4_group_t block_group)
  {
  	struct buffer_head *bh;

  	int err;

  
  	bh = ext4_read_block_bitmap_nowait(sb, block_group);

  	if (IS_ERR(bh))
  		return bh;
  	err = ext4_wait_block_bitmap(sb, block_group, bh);
  	if (err) {

  		put_bh(bh);

  		return ERR_PTR(err);

  	}

  	return bh;
  }

  
  /**

   * ext4_has_free_clusters()

   * @sbi:	in-core super block structure.

   * @nclusters:	number of needed blocks
   * @flags:	flags from ext4_mb_new_blocks()

   *

   * Check if filesystem has nclusters free & available for allocation.

   * On success return 1, return 0 on failure.
   */

  static int ext4_has_free_clusters(struct ext4_sb_info *sbi,
  				  s64 nclusters, unsigned int flags)

  {

  	s64 free_clusters, dirty_clusters, rsv, resv_clusters;

  	struct percpu_counter *fcc = &sbi->s_freeclusters_counter;

  	struct percpu_counter *dcc = &sbi->s_dirtyclusters_counter;

  	free_clusters  = percpu_counter_read_positive(fcc);
  	dirty_clusters = percpu_counter_read_positive(dcc);

  	resv_clusters = atomic64_read(&sbi->s_resv_clusters);

  
  	/*
  	 * r_blocks_count should always be multiple of the cluster ratio so
  	 * we are safe to do a plane bit shift only.
  	 */

  	rsv = (ext4_r_blocks_count(sbi->s_es) >> sbi->s_cluster_bits) +
  	      resv_clusters;

  	if (free_clusters - (nclusters + rsv + dirty_clusters) <

  					EXT4_FREECLUSTERS_WATERMARK) {

  		free_clusters  = percpu_counter_sum_positive(fcc);

  		dirty_clusters = percpu_counter_sum_positive(dcc);

  	}

  	/* Check whether we have space after accounting for current
  	 * dirty clusters & root reserved clusters.

  	 */

  	if (free_clusters >= (rsv + nclusters + dirty_clusters))

  		return 1;

  	/* Hm, nope.  Are (enough) root reserved clusters available? */

  	if (uid_eq(sbi->s_resuid, current_fsuid()) ||
  	    (!gid_eq(sbi->s_resgid, GLOBAL_ROOT_GID) && in_group_p(sbi->s_resgid)) ||

  	    capable(CAP_SYS_RESOURCE) ||

  	    (flags & EXT4_MB_USE_ROOT_BLOCKS)) {

  		if (free_clusters >= (nclusters + dirty_clusters +
  				      resv_clusters))
  			return 1;
  	}
  	/* No free blocks. Let's see if we can dip into reserved pool */
  	if (flags & EXT4_MB_USE_RESERVED) {

  		if (free_clusters >= (nclusters + dirty_clusters))

  			return 1;
  	}
  
  	return 0;

  }

  int ext4_claim_free_clusters(struct ext4_sb_info *sbi,
  			     s64 nclusters, unsigned int flags)

  {

  	if (ext4_has_free_clusters(sbi, nclusters, flags)) {

  		percpu_counter_add(&sbi->s_dirtyclusters_counter, nclusters);

  		return 0;

  	} else
  		return -ENOSPC;

  }

  /**

   * ext4_should_retry_alloc() - check if a block allocation should be retried

   * @sb:			super block

   * @retries:		number of attemps has been made

   *

   * ext4_should_retry_alloc() is called when ENOSPC is returned, and if

   * it is profitable to retry the operation, this function will wait

   * for the current or committing transaction to complete, and then

   * return TRUE.  We will only retry once.

   */

  int ext4_should_retry_alloc(struct super_block *sb, int *retries)

  {

  	if (!ext4_has_free_clusters(EXT4_SB(sb), 1, 0) ||

  	    (*retries)++ > 1 ||

  	    !EXT4_SB(sb)->s_journal)

  		return 0;

  	smp_mb();

  	if (EXT4_SB(sb)->s_mb_free_pending == 0)
  		return 0;
  
  	jbd_debug(1, "%s: retrying operation after ENOSPC
  ", sb->s_id);
  	jbd2_journal_force_commit_nested(EXT4_SB(sb)->s_journal);

  	return 1;

  }

  /*

   * ext4_new_meta_blocks() -- allocate block for meta data (indexing) blocks

   *
   * @handle:             handle to this transaction
   * @inode:              file inode
   * @goal:               given target block(filesystem wide)

   * @count:		pointer to total number of clusters needed

   * @errp:               error code
   *

   * Return 1st allocated block number on success, *count stores total account

   * error stores in errp pointer

   */

  ext4_fsblk_t ext4_new_meta_blocks(handle_t *handle, struct inode *inode,

  				  ext4_fsblk_t goal, unsigned int flags,
  				  unsigned long *count, int *errp)

  {

  	struct ext4_allocation_request ar;

  	ext4_fsblk_t ret;

  
  	memset(&ar, 0, sizeof(ar));
  	/* Fill with neighbour allocated blocks */
  	ar.inode = inode;
  	ar.goal = goal;
  	ar.len = count ? *count : 1;

  	ar.flags = flags;

  
  	ret = ext4_mb_new_blocks(handle, &ar, errp);
  	if (count)
  		*count = ar.len;

  	/*

  	 * Account for the allocated meta blocks.  We will never
  	 * fail EDQUOT for metdata, but we do account for it.

  	 */

  	if (!(*errp) && (flags & EXT4_MB_DELALLOC_RESERVED)) {

  		dquot_alloc_block_nofail(inode,
  				EXT4_C2B(EXT4_SB(inode->i_sb), ar.len));

  	}
  	return ret;

  }

  /**

   * ext4_count_free_clusters() -- count filesystem free clusters

   * @sb:		superblock
   *

   * Adds up the number of free clusters from each block group.

   */

  ext4_fsblk_t ext4_count_free_clusters(struct super_block *sb)

  {

  	ext4_fsblk_t desc_count;
  	struct ext4_group_desc *gdp;

  	ext4_group_t i;

  	ext4_group_t ngroups = ext4_get_groups_count(sb);

  	struct ext4_group_info *grp;

  #ifdef EXT4FS_DEBUG
  	struct ext4_super_block *es;
  	ext4_fsblk_t bitmap_count;

  	unsigned int x;

  	struct buffer_head *bitmap_bh = NULL;

  	es = EXT4_SB(sb)->s_es;

  	desc_count = 0;
  	bitmap_count = 0;
  	gdp = NULL;

  	for (i = 0; i < ngroups; i++) {

  		gdp = ext4_get_group_desc(sb, i, NULL);

  		if (!gdp)
  			continue;

  		grp = NULL;
  		if (EXT4_SB(sb)->s_group_info)
  			grp = ext4_get_group_info(sb, i);
  		if (!grp || !EXT4_MB_GRP_BBITMAP_CORRUPT(grp))
  			desc_count += ext4_free_group_clusters(sb, gdp);

  		brelse(bitmap_bh);

  		bitmap_bh = ext4_read_block_bitmap(sb, i);

  		if (IS_ERR(bitmap_bh)) {
  			bitmap_bh = NULL;

  			continue;

  		}

  		x = ext4_count_free(bitmap_bh->b_data,

  				    EXT4_CLUSTERS_PER_GROUP(sb) / 8);

  		printk(KERN_DEBUG "group %u: stored = %d, counted = %u
  ",

  			i, ext4_free_group_clusters(sb, gdp), x);

  		bitmap_count += x;
  	}
  	brelse(bitmap_bh);

  	printk(KERN_DEBUG "ext4_count_free_clusters: stored = %llu"
  	       ", computed = %llu, %llu
  ",

  	       EXT4_NUM_B2C(EXT4_SB(sb), ext4_free_blocks_count(es)),

  	       desc_count, bitmap_count);

  	return bitmap_count;
  #else
  	desc_count = 0;

  	for (i = 0; i < ngroups; i++) {

  		gdp = ext4_get_group_desc(sb, i, NULL);

  		if (!gdp)
  			continue;

  		grp = NULL;
  		if (EXT4_SB(sb)->s_group_info)
  			grp = ext4_get_group_info(sb, i);
  		if (!grp || !EXT4_MB_GRP_BBITMAP_CORRUPT(grp))
  			desc_count += ext4_free_group_clusters(sb, gdp);

  	}
  
  	return desc_count;
  #endif
  }

  static inline int test_root(ext4_group_t a, int b)

  {

  	while (1) {
  		if (a < b)
  			return 0;
  		if (a == b)
  			return 1;
  		if ((a % b) != 0)
  			return 0;
  		a = a / b;
  	}

  }

  /**

   *	ext4_bg_has_super - number of blocks used by the superblock in group

   *	@sb: superblock for filesystem
   *	@group: group number to check
   *
   *	Return the number of blocks used by the superblock (primary or backup)
   *	in this group.  Currently this will be only 0 or 1.
   */

  int ext4_bg_has_super(struct super_block *sb, ext4_group_t group)

  {

  	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
  
  	if (group == 0)
  		return 1;

  	if (ext4_has_feature_sparse_super2(sb)) {

  		if (group == le32_to_cpu(es->s_backup_bgs[0]) ||
  		    group == le32_to_cpu(es->s_backup_bgs[1]))
  			return 1;
  		return 0;
  	}

  	if ((group <= 1) || !ext4_has_feature_sparse_super(sb))

  		return 1;
  	if (!(group & 1))

  		return 0;

  	if (test_root(group, 3) || (test_root(group, 5)) ||
  	    test_root(group, 7))
  		return 1;
  
  	return 0;

  }

  static unsigned long ext4_bg_num_gdb_meta(struct super_block *sb,
  					ext4_group_t group)

  {

  	unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);

  	ext4_group_t first = metagroup * EXT4_DESC_PER_BLOCK(sb);
  	ext4_group_t last = first + EXT4_DESC_PER_BLOCK(sb) - 1;

  
  	if (group == first || group == first + 1 || group == last)
  		return 1;
  	return 0;
  }

  static unsigned long ext4_bg_num_gdb_nometa(struct super_block *sb,
  					ext4_group_t group)

  {

  	if (!ext4_bg_has_super(sb, group))
  		return 0;

  	if (ext4_has_feature_meta_bg(sb))

  		return le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg);
  	else
  		return EXT4_SB(sb)->s_gdb_count;

  }
  
  /**

   *	ext4_bg_num_gdb - number of blocks used by the group table in group

   *	@sb: superblock for filesystem
   *	@group: group number to check
   *
   *	Return the number of blocks used by the group descriptor table
   *	(primary or backup) in this group.  In the future there may be a
   *	different number of descriptor blocks in each group.
   */

  unsigned long ext4_bg_num_gdb(struct super_block *sb, ext4_group_t group)

  {
  	unsigned long first_meta_bg =

  			le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg);
  	unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);

  	if (!ext4_has_feature_meta_bg(sb) || metagroup < first_meta_bg)

  		return ext4_bg_num_gdb_nometa(sb, group);

  	return ext4_bg_num_gdb_meta(sb,group);

  
  }

  /*

   * This function returns the number of file system metadata clusters at

   * the beginning of a block group, including the reserved gdt blocks.
   */

  static unsigned ext4_num_base_meta_clusters(struct super_block *sb,

  				     ext4_group_t block_group)

  {
  	struct ext4_sb_info *sbi = EXT4_SB(sb);

  	unsigned num;

  
  	/* Check for superblock and gdt backups in this group */
  	num = ext4_bg_has_super(sb, block_group);

  	if (!ext4_has_feature_meta_bg(sb) ||

  	    block_group < le32_to_cpu(sbi->s_es->s_first_meta_bg) *
  			  sbi->s_desc_per_block) {
  		if (num) {
  			num += ext4_bg_num_gdb(sb, block_group);
  			num += le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks);
  		}
  	} else { /* For META_BG_BLOCK_GROUPS */
  		num += ext4_bg_num_gdb(sb, block_group);
  	}

  	return EXT4_NUM_B2C(sbi, num);

  }

  /**
   *	ext4_inode_to_goal_block - return a hint for block allocation
   *	@inode: inode for block allocation
   *
   *	Return the ideal location to start allocating blocks for a
   *	newly created inode.
   */
  ext4_fsblk_t ext4_inode_to_goal_block(struct inode *inode)
  {
  	struct ext4_inode_info *ei = EXT4_I(inode);
  	ext4_group_t block_group;
  	ext4_grpblk_t colour;
  	int flex_size = ext4_flex_bg_size(EXT4_SB(inode->i_sb));
  	ext4_fsblk_t bg_start;
  	ext4_fsblk_t last_block;
  
  	block_group = ei->i_block_group;
  	if (flex_size >= EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME) {
  		/*
  		 * If there are at least EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME
  		 * block groups per flexgroup, reserve the first block
  		 * group for directories and special files.  Regular
  		 * files will start at the second block group.  This
  		 * tends to speed up directory access and improves
  		 * fsck times.
  		 */
  		block_group &= ~(flex_size-1);
  		if (S_ISREG(inode->i_mode))
  			block_group++;
  	}
  	bg_start = ext4_group_first_block_no(inode->i_sb, block_group);
  	last_block = ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es) - 1;
  
  	/*
  	 * If we are doing delayed allocation, we don't need take
  	 * colour into account.
  	 */
  	if (test_opt(inode->i_sb, DELALLOC))
  		return bg_start;
  
  	if (bg_start + EXT4_BLOCKS_PER_GROUP(inode->i_sb) <= last_block)

  		colour = (task_pid_nr(current) % 16) *

  			(EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16);
  	else

  		colour = (task_pid_nr(current) % 16) *
  			((last_block - bg_start) / 16);

  	return bg_start + colour;
  }