/*

   *  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/jbd2.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 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;

  
  }

  static int ext4_block_in_group(struct super_block *sb, ext4_fsblk_t block,
  			ext4_group_t block_group)
  {
  	ext4_group_t actual_group;

  	ext4_get_group_no_and_offset(sb, block, &actual_group, NULL);

  	if (actual_group == block_group)
  		return 1;
  	return 0;
  }

  /* Return the number of clusters used for file system metadata; this
   * represents the overhead needed by the file system.
   */
  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, (start -
  					       ext4_block_bitmap(sb, gdp)));
  		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,
  					 start - ext4_inode_bitmap(sb, gdp));
  		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, start - itbl_blk + i);
  			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 */
  void 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;
  	int flex_bg = 0;
  
  	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(sbi, block_group, gdp)) {
  		ext4_error(sb, "Checksum bad for group %u", block_group);

  		ext4_free_group_clusters_set(sb, gdp, 0);

  		ext4_free_inodes_set(sb, gdp, 0);
  		ext4_itable_unused_set(sb, gdp, 0);
  		memset(bh->b_data, 0xff, sb->s_blocksize);
  		return;

  	}

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

  	bit_max = ext4_num_base_meta_clusters(sb, block_group);

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

  	start = ext4_group_first_block_no(sb, block_group);

  	if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG))
  		flex_bg = 1;

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

  	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);

  	if (!sbi->s_group_desc[group_desc]) {

  		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 *)sbi->s_group_desc[group_desc]->b_data +
  		offset * EXT4_DESC_SIZE(sb));

  	if (bh)
  		*bh = sbi->s_group_desc[group_desc];

  	return desc;

  }

  static int ext4_valid_block_bitmap(struct super_block *sb,
  					struct ext4_group_desc *desc,
  					unsigned int block_group,
  					struct buffer_head *bh)
  {
  	ext4_grpblk_t offset;
  	ext4_grpblk_t next_zero_bit;
  	ext4_fsblk_t bitmap_blk;
  	ext4_fsblk_t group_first_block;
  
  	if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) {
  		/* 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 1;
  	}
  	group_first_block = ext4_group_first_block_no(sb, block_group);
  
  	/* check whether block bitmap block number is set */
  	bitmap_blk = ext4_block_bitmap(sb, desc);
  	offset = bitmap_blk - group_first_block;
  	if (!ext4_test_bit(offset, bh->b_data))
  		/* bad block bitmap */
  		goto err_out;
  
  	/* check whether the inode bitmap block number is set */
  	bitmap_blk = ext4_inode_bitmap(sb, desc);
  	offset = bitmap_blk - group_first_block;
  	if (!ext4_test_bit(offset, bh->b_data))
  		/* bad block bitmap */
  		goto err_out;
  
  	/* check whether the inode table block number is set */
  	bitmap_blk = ext4_inode_table(sb, desc);
  	offset = bitmap_blk - group_first_block;
  	next_zero_bit = ext4_find_next_zero_bit(bh->b_data,
  				offset + EXT4_SB(sb)->s_itb_per_group,
  				offset);
  	if (next_zero_bit >= offset + EXT4_SB(sb)->s_itb_per_group)
  		/* good bitmap for inode tables */
  		return 1;
  
  err_out:

  	ext4_error(sb, "Invalid block bitmap - block_group = %d, block = %llu",

  			block_group, bitmap_blk);
  	return 0;
  }

  /**

   * ext4_read_block_bitmap()

   * @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 NULL in case of failure.
   */

  struct buffer_head *

  ext4_read_block_bitmap(struct super_block *sb, ext4_group_t block_group)

  {

  	struct ext4_group_desc *desc;
  	struct buffer_head *bh = NULL;

  	ext4_fsblk_t bitmap_blk;

  	desc = ext4_get_group_desc(sb, block_group, NULL);

  	if (!desc)

  		return NULL;
  	bitmap_blk = ext4_block_bitmap(sb, desc);

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

  		ext4_error(sb, "Cannot read block bitmap - "

  			    "block_group = %u, block_bitmap = %llu",

  			    block_group, bitmap_blk);

  		return NULL;
  	}

  
  	if (bitmap_uptodate(bh))

  		return bh;

  	lock_buffer(bh);

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

  	ext4_lock_group(sb, block_group);

  	if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {

  		ext4_init_block_bitmap(sb, bh, block_group, desc);

  		set_bitmap_uptodate(bh);

  		set_buffer_uptodate(bh);

  		ext4_unlock_group(sb, block_group);

  		unlock_buffer(bh);

  		return bh;

  	}

  	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);
  		return bh;
  	}
  	/*
  	 * submit the buffer_head for read. We can
  	 * safely mark the bitmap as uptodate now.
  	 * We do it here so the bitmap uptodate bit
  	 * get set with buffer lock held.
  	 */

  	trace_ext4_read_block_bitmap_load(sb, block_group);

  	set_bitmap_uptodate(bh);

  	if (bh_submit_read(bh) < 0) {
  		put_bh(bh);

  		ext4_error(sb, "Cannot read block bitmap - "

  			    "block_group = %u, block_bitmap = %llu",

  			    block_group, bitmap_blk);

  		return NULL;
  	}

  	ext4_valid_block_bitmap(sb, desc, block_group, bh);
  	/*
  	 * file system mounted not to panic on error,
  	 * continue with corrupt bitmap
  	 */

  	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, root_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);
  	root_clusters = EXT4_B2C(sbi, ext4_r_blocks_count(sbi->s_es));

  	if (free_clusters - (nclusters + root_clusters + dirty_clusters) <
  					EXT4_FREECLUSTERS_WATERMARK) {
  		free_clusters  = EXT4_C2B(sbi, 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 >= ((root_clusters + nclusters) + dirty_clusters))

  		return 1;

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

  	if (sbi->s_resuid == current_fsuid() ||

  	    ((sbi->s_resgid != 0) && in_group_p(sbi->s_resgid)) ||

  	    capable(CAP_SYS_RESOURCE) ||
  		(flags & EXT4_MB_USE_ROOT_BLOCKS)) {

  		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()

   * @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.
   *
   * if the total number of retries exceed three times, return FALSE.
   */

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

  {

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

  	    (*retries)++ > 3 ||
  	    !EXT4_SB(sb)->s_journal)

  		return 0;
  
  	jbd_debug(1, "%s: retrying operation after ENOSPC
  ", sb->s_id);

  	return jbd2_journal_force_commit_nested(EXT4_SB(sb)->s_journal);

  }

  /*

   * 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) &&
  	    ext4_test_inode_state(inode, EXT4_STATE_DELALLOC_RESERVED)) {

  		spin_lock(&EXT4_I(inode)->i_block_reservation_lock);

  		EXT4_I(inode)->i_allocated_meta_blocks += ar.len;

  		spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);

  		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);

  #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;

  		desc_count += ext4_free_group_clusters(sb, gdp);

  		brelse(bitmap_bh);

  		bitmap_bh = ext4_read_block_bitmap(sb, i);

  		if (bitmap_bh == NULL)
  			continue;

  		x = ext4_count_free(bitmap_bh, sb->s_blocksize);

  		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_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;

  		desc_count += ext4_free_group_clusters(sb, gdp);

  	}
  
  	return desc_count;
  #endif
  }

  static inline int test_root(ext4_group_t a, int b)

  {
  	int num = b;
  
  	while (a > num)
  		num *= b;
  	return num == a;
  }

  static int ext4_group_sparse(ext4_group_t group)

  {
  	if (group <= 1)
  		return 1;
  	if (!(group & 1))
  		return 0;
  	return (test_root(group, 7) || test_root(group, 5) ||
  		test_root(group, 3));
  }
  
  /**

   *	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)

  {

  	if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
  				EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER) &&
  			!ext4_group_sparse(group))

  		return 0;
  	return 1;
  }

  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_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG))
  		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_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG) ||

  			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_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG) ||
  	    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 = (current->pid % 16) *
  			(EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16);
  	else
  		colour = (current->pid % 16) * ((last_block - bg_start) / 16);
  	return bg_start + colour;
  }