/*

   *  linux/fs/ext4/resize.c

   *

   * Support for resizing an ext4 filesystem while it is mounted.

   *
   * Copyright (C) 2001, 2002 Andreas Dilger <adilger@clusterfs.com>
   *
   * This could probably be made into a module, because it is not often in use.
   */

  #define EXT4FS_DEBUG

  #include <linux/errno.h>
  #include <linux/slab.h>

  #include "ext4_jbd2.h"

  int ext4_resize_begin(struct super_block *sb)
  {
  	int ret = 0;
  
  	if (!capable(CAP_SYS_RESOURCE))
  		return -EPERM;

  	/*
  	 * We are not allowed to do online-resizing on a filesystem mounted
  	 * with error, because it can destroy the filesystem easily.
  	 */
  	if (EXT4_SB(sb)->s_mount_state & EXT4_ERROR_FS) {
  		ext4_warning(sb, "There are errors in the filesystem, "
  			     "so online resizing is not allowed
  ");
  		return -EPERM;
  	}

  	if (test_and_set_bit_lock(EXT4_RESIZING, &EXT4_SB(sb)->s_resize_flags))
  		ret = -EBUSY;
  
  	return ret;
  }
  
  void ext4_resize_end(struct super_block *sb)
  {
  	clear_bit_unlock(EXT4_RESIZING, &EXT4_SB(sb)->s_resize_flags);
  	smp_mb__after_clear_bit();
  }

  #define outside(b, first, last)	((b) < (first) || (b) >= (last))
  #define inside(b, first, last)	((b) >= (first) && (b) < (last))
  
  static int verify_group_input(struct super_block *sb,

  			      struct ext4_new_group_data *input)

  {

  	struct ext4_sb_info *sbi = EXT4_SB(sb);
  	struct ext4_super_block *es = sbi->s_es;

  	ext4_fsblk_t start = ext4_blocks_count(es);

  	ext4_fsblk_t end = start + input->blocks_count;

  	ext4_group_t group = input->group;

  	ext4_fsblk_t itend = input->inode_table + sbi->s_itb_per_group;
  	unsigned overhead = ext4_bg_has_super(sb, group) ?
  		(1 + ext4_bg_num_gdb(sb, group) +

  		 le16_to_cpu(es->s_reserved_gdt_blocks)) : 0;

  	ext4_fsblk_t metaend = start + overhead;

  	struct buffer_head *bh = NULL;

  	ext4_grpblk_t free_blocks_count, offset;

  	int err = -EINVAL;
  
  	input->free_blocks_count = free_blocks_count =
  		input->blocks_count - 2 - overhead - sbi->s_itb_per_group;
  
  	if (test_opt(sb, DEBUG))

  		printk(KERN_DEBUG "EXT4-fs: adding %s group %u: %u blocks "

  		       "(%d free, %u reserved)
  ",

  		       ext4_bg_has_super(sb, input->group) ? "normal" :

  		       "no-super", input->group, input->blocks_count,
  		       free_blocks_count, input->reserved_blocks);

  	ext4_get_group_no_and_offset(sb, start, NULL, &offset);

  	if (group != sbi->s_groups_count)

  		ext4_warning(sb, "Cannot add at group %u (only %u groups)",

  			     input->group, sbi->s_groups_count);

  	else if (offset != 0)

  			ext4_warning(sb, "Last group not full");

  	else if (input->reserved_blocks > input->blocks_count / 5)

  		ext4_warning(sb, "Reserved blocks too high (%u)",

  			     input->reserved_blocks);
  	else if (free_blocks_count < 0)

  		ext4_warning(sb, "Bad blocks count %u",

  			     input->blocks_count);
  	else if (!(bh = sb_bread(sb, end - 1)))

  		ext4_warning(sb, "Cannot read last block (%llu)",

  			     end - 1);
  	else if (outside(input->block_bitmap, start, end))

  		ext4_warning(sb, "Block bitmap not in group (block %llu)",

  			     (unsigned long long)input->block_bitmap);

  	else if (outside(input->inode_bitmap, start, end))

  		ext4_warning(sb, "Inode bitmap not in group (block %llu)",

  			     (unsigned long long)input->inode_bitmap);

  	else if (outside(input->inode_table, start, end) ||

  		 outside(itend - 1, start, end))

  		ext4_warning(sb, "Inode table not in group (blocks %llu-%llu)",

  			     (unsigned long long)input->inode_table, itend - 1);

  	else if (input->inode_bitmap == input->block_bitmap)

  		ext4_warning(sb, "Block bitmap same as inode bitmap (%llu)",

  			     (unsigned long long)input->block_bitmap);

  	else if (inside(input->block_bitmap, input->inode_table, itend))

  		ext4_warning(sb, "Block bitmap (%llu) in inode table "
  			     "(%llu-%llu)",

  			     (unsigned long long)input->block_bitmap,
  			     (unsigned long long)input->inode_table, itend - 1);

  	else if (inside(input->inode_bitmap, input->inode_table, itend))

  		ext4_warning(sb, "Inode bitmap (%llu) in inode table "
  			     "(%llu-%llu)",

  			     (unsigned long long)input->inode_bitmap,
  			     (unsigned long long)input->inode_table, itend - 1);

  	else if (inside(input->block_bitmap, start, metaend))

  		ext4_warning(sb, "Block bitmap (%llu) in GDT table (%llu-%llu)",

  			     (unsigned long long)input->block_bitmap,
  			     start, metaend - 1);

  	else if (inside(input->inode_bitmap, start, metaend))

  		ext4_warning(sb, "Inode bitmap (%llu) in GDT table (%llu-%llu)",

  			     (unsigned long long)input->inode_bitmap,
  			     start, metaend - 1);

  	else if (inside(input->inode_table, start, metaend) ||

  		 inside(itend - 1, start, metaend))

  		ext4_warning(sb, "Inode table (%llu-%llu) overlaps GDT table "
  			     "(%llu-%llu)",

  			     (unsigned long long)input->inode_table,
  			     itend - 1, start, metaend - 1);

  	else
  		err = 0;
  	brelse(bh);
  
  	return err;
  }

  /*
   * ext4_new_flex_group_data is used by 64bit-resize interface to add a flex
   * group each time.
   */
  struct ext4_new_flex_group_data {
  	struct ext4_new_group_data *groups;	/* new_group_data for groups
  						   in the flex group */
  	__u16 *bg_flags;			/* block group flags of groups
  						   in @groups */
  	ext4_group_t count;			/* number of groups in @groups
  						 */
  };
  
  /*
   * alloc_flex_gd() allocates a ext4_new_flex_group_data with size of
   * @flexbg_size.
   *
   * Returns NULL on failure otherwise address of the allocated structure.
   */
  static struct ext4_new_flex_group_data *alloc_flex_gd(unsigned long flexbg_size)
  {
  	struct ext4_new_flex_group_data *flex_gd;
  
  	flex_gd = kmalloc(sizeof(*flex_gd), GFP_NOFS);
  	if (flex_gd == NULL)
  		goto out3;
  
  	flex_gd->count = flexbg_size;
  
  	flex_gd->groups = kmalloc(sizeof(struct ext4_new_group_data) *
  				  flexbg_size, GFP_NOFS);
  	if (flex_gd->groups == NULL)
  		goto out2;
  
  	flex_gd->bg_flags = kmalloc(flexbg_size * sizeof(__u16), GFP_NOFS);
  	if (flex_gd->bg_flags == NULL)
  		goto out1;
  
  	return flex_gd;
  
  out1:
  	kfree(flex_gd->groups);
  out2:
  	kfree(flex_gd);
  out3:
  	return NULL;
  }
  
  static void free_flex_gd(struct ext4_new_flex_group_data *flex_gd)
  {
  	kfree(flex_gd->bg_flags);
  	kfree(flex_gd->groups);
  	kfree(flex_gd);
  }

  /*
   * ext4_alloc_group_tables() allocates block bitmaps, inode bitmaps
   * and inode tables for a flex group.
   *
   * This function is used by 64bit-resize.  Note that this function allocates
   * group tables from the 1st group of groups contained by @flexgd, which may
   * be a partial of a flex group.
   *
   * @sb: super block of fs to which the groups belongs
   */
  static void ext4_alloc_group_tables(struct super_block *sb,
  				struct ext4_new_flex_group_data *flex_gd,
  				int flexbg_size)
  {
  	struct ext4_new_group_data *group_data = flex_gd->groups;
  	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
  	ext4_fsblk_t start_blk;
  	ext4_fsblk_t last_blk;
  	ext4_group_t src_group;
  	ext4_group_t bb_index = 0;
  	ext4_group_t ib_index = 0;
  	ext4_group_t it_index = 0;
  	ext4_group_t group;
  	ext4_group_t last_group;
  	unsigned overhead;
  
  	BUG_ON(flex_gd->count == 0 || group_data == NULL);
  
  	src_group = group_data[0].group;
  	last_group  = src_group + flex_gd->count - 1;
  
  	BUG_ON((flexbg_size > 1) && ((src_group & ~(flexbg_size - 1)) !=
  	       (last_group & ~(flexbg_size - 1))));
  next_group:
  	group = group_data[0].group;
  	start_blk = ext4_group_first_block_no(sb, src_group);
  	last_blk = start_blk + group_data[src_group - group].blocks_count;
  
  	overhead = ext4_bg_has_super(sb, src_group) ?
  		   (1 + ext4_bg_num_gdb(sb, src_group) +
  		    le16_to_cpu(es->s_reserved_gdt_blocks)) : 0;
  
  	start_blk += overhead;
  
  	BUG_ON(src_group >= group_data[0].group + flex_gd->count);
  	/* We collect contiguous blocks as much as possible. */
  	src_group++;
  	for (; src_group <= last_group; src_group++)
  		if (!ext4_bg_has_super(sb, src_group))
  			last_blk += group_data[src_group - group].blocks_count;
  		else
  			break;
  
  	/* Allocate block bitmaps */
  	for (; bb_index < flex_gd->count; bb_index++) {
  		if (start_blk >= last_blk)
  			goto next_group;
  		group_data[bb_index].block_bitmap = start_blk++;
  		ext4_get_group_no_and_offset(sb, start_blk - 1, &group, NULL);
  		group -= group_data[0].group;
  		group_data[group].free_blocks_count--;
  		if (flexbg_size > 1)
  			flex_gd->bg_flags[group] &= ~EXT4_BG_BLOCK_UNINIT;
  	}
  
  	/* Allocate inode bitmaps */
  	for (; ib_index < flex_gd->count; ib_index++) {
  		if (start_blk >= last_blk)
  			goto next_group;
  		group_data[ib_index].inode_bitmap = start_blk++;
  		ext4_get_group_no_and_offset(sb, start_blk - 1, &group, NULL);
  		group -= group_data[0].group;
  		group_data[group].free_blocks_count--;
  		if (flexbg_size > 1)
  			flex_gd->bg_flags[group] &= ~EXT4_BG_BLOCK_UNINIT;
  	}
  
  	/* Allocate inode tables */
  	for (; it_index < flex_gd->count; it_index++) {
  		if (start_blk + EXT4_SB(sb)->s_itb_per_group > last_blk)
  			goto next_group;
  		group_data[it_index].inode_table = start_blk;
  		ext4_get_group_no_and_offset(sb, start_blk, &group, NULL);
  		group -= group_data[0].group;
  		group_data[group].free_blocks_count -=
  					EXT4_SB(sb)->s_itb_per_group;
  		if (flexbg_size > 1)
  			flex_gd->bg_flags[group] &= ~EXT4_BG_BLOCK_UNINIT;
  
  		start_blk += EXT4_SB(sb)->s_itb_per_group;
  	}
  
  	if (test_opt(sb, DEBUG)) {
  		int i;
  		group = group_data[0].group;
  
  		printk(KERN_DEBUG "EXT4-fs: adding a flex group with "
  		       "%d groups, flexbg size is %d:
  ", flex_gd->count,
  		       flexbg_size);
  
  		for (i = 0; i < flex_gd->count; i++) {
  			printk(KERN_DEBUG "adding %s group %u: %u "
  			       "blocks (%d free)
  ",
  			       ext4_bg_has_super(sb, group + i) ? "normal" :
  			       "no-super", group + i,
  			       group_data[i].blocks_count,
  			       group_data[i].free_blocks_count);
  		}
  	}
  }

  static struct buffer_head *bclean(handle_t *handle, struct super_block *sb,

  				  ext4_fsblk_t blk)

  {
  	struct buffer_head *bh;
  	int err;
  
  	bh = sb_getblk(sb, blk);
  	if (!bh)
  		return ERR_PTR(-EIO);

  	if ((err = ext4_journal_get_write_access(handle, bh))) {

  		brelse(bh);
  		bh = ERR_PTR(err);
  	} else {

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

  	}
  
  	return bh;
  }
  
  /*

   * If we have fewer than thresh credits, extend by EXT4_MAX_TRANS_DATA.
   * If that fails, restart the transaction & regain write access for the
   * buffer head which is used for block_bitmap modifications.
   */

  static int extend_or_restart_transaction(handle_t *handle, int thresh)

  {
  	int err;

  	if (ext4_handle_has_enough_credits(handle, thresh))

  		return 0;
  
  	err = ext4_journal_extend(handle, EXT4_MAX_TRANS_DATA);
  	if (err < 0)
  		return err;
  	if (err) {

  		err = ext4_journal_restart(handle, EXT4_MAX_TRANS_DATA);
  		if (err)

  			return err;

  	}

  
  	return 0;
  }
  
  /*

   * set_flexbg_block_bitmap() mark @count blocks starting from @block used.
   *
   * Helper function for ext4_setup_new_group_blocks() which set .
   *
   * @sb: super block
   * @handle: journal handle
   * @flex_gd: flex group data
   */
  static int set_flexbg_block_bitmap(struct super_block *sb, handle_t *handle,
  			struct ext4_new_flex_group_data *flex_gd,
  			ext4_fsblk_t block, ext4_group_t count)
  {
  	ext4_group_t count2;
  
  	ext4_debug("mark blocks [%llu/%u] used
  ", block, count);
  	for (count2 = count; count > 0; count -= count2, block += count2) {
  		ext4_fsblk_t start;
  		struct buffer_head *bh;
  		ext4_group_t group;
  		int err;
  
  		ext4_get_group_no_and_offset(sb, block, &group, NULL);
  		start = ext4_group_first_block_no(sb, group);
  		group -= flex_gd->groups[0].group;
  
  		count2 = sb->s_blocksize * 8 - (block - start);
  		if (count2 > count)
  			count2 = count;
  
  		if (flex_gd->bg_flags[group] & EXT4_BG_BLOCK_UNINIT) {
  			BUG_ON(flex_gd->count > 1);
  			continue;
  		}
  
  		err = extend_or_restart_transaction(handle, 1);
  		if (err)
  			return err;
  
  		bh = sb_getblk(sb, flex_gd->groups[group].block_bitmap);
  		if (!bh)
  			return -EIO;
  
  		err = ext4_journal_get_write_access(handle, bh);
  		if (err)
  			return err;
  		ext4_debug("mark block bitmap %#04llx (+%llu/%u)
  ", block,
  			   block - start, count2);
  		ext4_set_bits(bh->b_data, block - start, count2);
  
  		err = ext4_handle_dirty_metadata(handle, NULL, bh);
  		if (unlikely(err))
  			return err;
  		brelse(bh);
  	}
  
  	return 0;
  }
  
  /*
   * Set up the block and inode bitmaps, and the inode table for the new groups.
   * This doesn't need to be part of the main transaction, since we are only
   * changing blocks outside the actual filesystem.  We still do journaling to
   * ensure the recovery is correct in case of a failure just after resize.
   * If any part of this fails, we simply abort the resize.
   *
   * setup_new_flex_group_blocks handles a flex group as follow:
   *  1. copy super block and GDT, and initialize group tables if necessary.
   *     In this step, we only set bits in blocks bitmaps for blocks taken by
   *     super block and GDT.
   *  2. allocate group tables in block bitmaps, that is, set bits in block
   *     bitmap for blocks taken by group tables.
   */
  static int setup_new_flex_group_blocks(struct super_block *sb,
  				struct ext4_new_flex_group_data *flex_gd)
  {
  	int group_table_count[] = {1, 1, EXT4_SB(sb)->s_itb_per_group};
  	ext4_fsblk_t start;
  	ext4_fsblk_t block;
  	struct ext4_sb_info *sbi = EXT4_SB(sb);
  	struct ext4_super_block *es = sbi->s_es;
  	struct ext4_new_group_data *group_data = flex_gd->groups;
  	__u16 *bg_flags = flex_gd->bg_flags;
  	handle_t *handle;
  	ext4_group_t group, count;
  	struct buffer_head *bh = NULL;
  	int reserved_gdb, i, j, err = 0, err2;
  
  	BUG_ON(!flex_gd->count || !group_data ||
  	       group_data[0].group != sbi->s_groups_count);
  
  	reserved_gdb = le16_to_cpu(es->s_reserved_gdt_blocks);
  
  	/* This transaction may be extended/restarted along the way */
  	handle = ext4_journal_start_sb(sb, EXT4_MAX_TRANS_DATA);
  	if (IS_ERR(handle))
  		return PTR_ERR(handle);
  
  	group = group_data[0].group;
  	for (i = 0; i < flex_gd->count; i++, group++) {
  		unsigned long gdblocks;
  
  		gdblocks = ext4_bg_num_gdb(sb, group);
  		start = ext4_group_first_block_no(sb, group);
  
  		/* Copy all of the GDT blocks into the backup in this group */
  		for (j = 0, block = start + 1; j < gdblocks; j++, block++) {
  			struct buffer_head *gdb;
  
  			ext4_debug("update backup group %#04llx
  ", block);
  			err = extend_or_restart_transaction(handle, 1);
  			if (err)
  				goto out;
  
  			gdb = sb_getblk(sb, block);
  			if (!gdb) {
  				err = -EIO;
  				goto out;
  			}
  
  			err = ext4_journal_get_write_access(handle, gdb);
  			if (err) {
  				brelse(gdb);
  				goto out;
  			}
  			memcpy(gdb->b_data, sbi->s_group_desc[j]->b_data,
  			       gdb->b_size);
  			set_buffer_uptodate(gdb);
  
  			err = ext4_handle_dirty_metadata(handle, NULL, gdb);
  			if (unlikely(err)) {
  				brelse(gdb);
  				goto out;
  			}
  			brelse(gdb);
  		}
  
  		/* Zero out all of the reserved backup group descriptor
  		 * table blocks
  		 */
  		if (ext4_bg_has_super(sb, group)) {
  			err = sb_issue_zeroout(sb, gdblocks + start + 1,
  					reserved_gdb, GFP_NOFS);
  			if (err)
  				goto out;
  		}
  
  		/* Initialize group tables of the grop @group */
  		if (!(bg_flags[i] & EXT4_BG_INODE_ZEROED))
  			goto handle_bb;
  
  		/* Zero out all of the inode table blocks */
  		block = group_data[i].inode_table;
  		ext4_debug("clear inode table blocks %#04llx -> %#04lx
  ",
  			   block, sbi->s_itb_per_group);
  		err = sb_issue_zeroout(sb, block, sbi->s_itb_per_group,
  				       GFP_NOFS);
  		if (err)
  			goto out;
  
  handle_bb:
  		if (bg_flags[i] & EXT4_BG_BLOCK_UNINIT)
  			goto handle_ib;
  
  		/* Initialize block bitmap of the @group */
  		block = group_data[i].block_bitmap;
  		err = extend_or_restart_transaction(handle, 1);
  		if (err)
  			goto out;
  
  		bh = bclean(handle, sb, block);
  		if (IS_ERR(bh)) {
  			err = PTR_ERR(bh);
  			goto out;
  		}
  		if (ext4_bg_has_super(sb, group)) {
  			ext4_debug("mark backup superblock %#04llx (+0)
  ",
  				   start);
  			ext4_set_bits(bh->b_data, 0, gdblocks + reserved_gdb +
  						     1);
  		}
  		ext4_mark_bitmap_end(group_data[i].blocks_count,
  				     sb->s_blocksize * 8, bh->b_data);
  		err = ext4_handle_dirty_metadata(handle, NULL, bh);
  		if (err)
  			goto out;
  		brelse(bh);
  
  handle_ib:
  		if (bg_flags[i] & EXT4_BG_INODE_UNINIT)
  			continue;
  
  		/* Initialize inode bitmap of the @group */
  		block = group_data[i].inode_bitmap;
  		err = extend_or_restart_transaction(handle, 1);
  		if (err)
  			goto out;
  		/* Mark unused entries in inode bitmap used */
  		bh = bclean(handle, sb, block);
  		if (IS_ERR(bh)) {
  			err = PTR_ERR(bh);
  			goto out;
  		}
  
  		ext4_mark_bitmap_end(EXT4_INODES_PER_GROUP(sb),
  				     sb->s_blocksize * 8, bh->b_data);
  		err = ext4_handle_dirty_metadata(handle, NULL, bh);
  		if (err)
  			goto out;
  		brelse(bh);
  	}
  	bh = NULL;
  
  	/* Mark group tables in block bitmap */
  	for (j = 0; j < GROUP_TABLE_COUNT; j++) {
  		count = group_table_count[j];
  		start = (&group_data[0].block_bitmap)[j];
  		block = start;
  		for (i = 1; i < flex_gd->count; i++) {
  			block += group_table_count[j];
  			if (block == (&group_data[i].block_bitmap)[j]) {
  				count += group_table_count[j];
  				continue;
  			}
  			err = set_flexbg_block_bitmap(sb, handle,
  						flex_gd, start, count);
  			if (err)
  				goto out;
  			count = group_table_count[j];
  			start = group_data[i].block_bitmap;
  			block = start;
  		}
  
  		if (count) {
  			err = set_flexbg_block_bitmap(sb, handle,
  						flex_gd, start, count);
  			if (err)
  				goto out;
  		}
  	}
  
  out:
  	brelse(bh);
  	err2 = ext4_journal_stop(handle);
  	if (err2 && !err)
  		err = err2;
  
  	return err;
  }
  
  /*

   * Iterate through the groups which hold BACKUP superblock/GDT copies in an

   * ext4 filesystem.  The counters should be initialized to 1, 5, and 7 before

   * calling this for the first time.  In a sparse filesystem it will be the
   * sequence of powers of 3, 5, and 7: 1, 3, 5, 7, 9, 25, 27, 49, 81, ...
   * For a non-sparse filesystem it will be every group: 1, 2, 3, 4, ...
   */

  static unsigned ext4_list_backups(struct super_block *sb, unsigned *three,

  				  unsigned *five, unsigned *seven)
  {
  	unsigned *min = three;
  	int mult = 3;
  	unsigned ret;

  	if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
  					EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER)) {

  		ret = *min;
  		*min += 1;
  		return ret;
  	}
  
  	if (*five < *min) {
  		min = five;
  		mult = 5;
  	}
  	if (*seven < *min) {
  		min = seven;
  		mult = 7;
  	}
  
  	ret = *min;
  	*min *= mult;
  
  	return ret;
  }
  
  /*
   * Check that all of the backup GDT blocks are held in the primary GDT block.
   * It is assumed that they are stored in group order.  Returns the number of
   * groups in current filesystem that have BACKUPS, or -ve error code.
   */
  static int verify_reserved_gdb(struct super_block *sb,

  			       ext4_group_t end,

  			       struct buffer_head *primary)
  {

  	const ext4_fsblk_t blk = primary->b_blocknr;

  	unsigned three = 1;
  	unsigned five = 5;
  	unsigned seven = 7;
  	unsigned grp;
  	__le32 *p = (__le32 *)primary->b_data;
  	int gdbackups = 0;

  	while ((grp = ext4_list_backups(sb, &three, &five, &seven)) < end) {

  		if (le32_to_cpu(*p++) !=
  		    grp * EXT4_BLOCKS_PER_GROUP(sb) + blk){

  			ext4_warning(sb, "reserved GDT %llu"

  				     " missing grp %d (%llu)",

  				     blk, grp,

  				     grp *
  				     (ext4_fsblk_t)EXT4_BLOCKS_PER_GROUP(sb) +
  				     blk);

  			return -EINVAL;
  		}

  		if (++gdbackups > EXT4_ADDR_PER_BLOCK(sb))

  			return -EFBIG;
  	}
  
  	return gdbackups;
  }
  
  /*
   * Called when we need to bring a reserved group descriptor table block into
   * use from the resize inode.  The primary copy of the new GDT block currently
   * is an indirect block (under the double indirect block in the resize inode).
   * The new backup GDT blocks will be stored as leaf blocks in this indirect
   * block, in group order.  Even though we know all the block numbers we need,
   * we check to ensure that the resize inode has actually reserved these blocks.
   *
   * Don't need to update the block bitmaps because the blocks are still in use.
   *
   * We get all of the error cases out of the way, so that we are sure to not
   * fail once we start modifying the data on disk, because JBD has no rollback.
   */
  static int add_new_gdb(handle_t *handle, struct inode *inode,

  		       ext4_group_t group)

  {
  	struct super_block *sb = inode->i_sb;

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

  	unsigned long gdb_num = group / EXT4_DESC_PER_BLOCK(sb);

  	ext4_fsblk_t gdblock = EXT4_SB(sb)->s_sbh->b_blocknr + 1 + gdb_num;

  	struct buffer_head **o_group_desc, **n_group_desc;
  	struct buffer_head *dind;

  	struct buffer_head *gdb_bh;

  	int gdbackups;

  	struct ext4_iloc iloc;

  	__le32 *data;
  	int err;
  
  	if (test_opt(sb, DEBUG))
  		printk(KERN_DEBUG

  		       "EXT4-fs: ext4_add_new_gdb: adding group block %lu
  ",

  		       gdb_num);

  	/*
  	 * If we are not using the primary superblock/GDT copy don't resize,

           * because the user tools have no way of handling this.  Probably a
           * bad time to do it anyways.
           */

  	if (EXT4_SB(sb)->s_sbh->b_blocknr !=
  	    le32_to_cpu(EXT4_SB(sb)->s_es->s_first_data_block)) {

  		ext4_warning(sb, "won't resize using backup superblock at %llu",

  			(unsigned long long)EXT4_SB(sb)->s_sbh->b_blocknr);

  		return -EPERM;
  	}

  	gdb_bh = sb_bread(sb, gdblock);
  	if (!gdb_bh)

  		return -EIO;

  	gdbackups = verify_reserved_gdb(sb, group, gdb_bh);

  	if (gdbackups < 0) {

  		err = gdbackups;
  		goto exit_bh;
  	}

  	data = EXT4_I(inode)->i_data + EXT4_DIND_BLOCK;

  	dind = sb_bread(sb, le32_to_cpu(*data));
  	if (!dind) {
  		err = -EIO;
  		goto exit_bh;
  	}
  
  	data = (__le32 *)dind->b_data;

  	if (le32_to_cpu(data[gdb_num % EXT4_ADDR_PER_BLOCK(sb)]) != gdblock) {

  		ext4_warning(sb, "new group %u GDT block %llu not reserved",

  			     group, gdblock);

  		err = -EINVAL;
  		goto exit_dind;
  	}

  	err = ext4_journal_get_write_access(handle, EXT4_SB(sb)->s_sbh);
  	if (unlikely(err))

  		goto exit_dind;

  	err = ext4_journal_get_write_access(handle, gdb_bh);

  	if (unlikely(err))

  		goto exit_sbh;

  	err = ext4_journal_get_write_access(handle, dind);
  	if (unlikely(err))
  		ext4_std_error(sb, err);

  	/* ext4_reserve_inode_write() gets a reference on the iloc */

  	err = ext4_reserve_inode_write(handle, inode, &iloc);
  	if (unlikely(err))

  		goto exit_dindj;

  	n_group_desc = ext4_kvmalloc((gdb_num + 1) *
  				     sizeof(struct buffer_head *),
  				     GFP_NOFS);

  	if (!n_group_desc) {
  		err = -ENOMEM;

  		ext4_warning(sb, "not enough memory for %lu groups",
  			     gdb_num + 1);

  		goto exit_inode;
  	}
  
  	/*
  	 * Finally, we have all of the possible failures behind us...
  	 *
  	 * Remove new GDT block from inode double-indirect block and clear out
  	 * the new GDT block for use (which also "frees" the backup GDT blocks
  	 * from the reserved inode).  We don't need to change the bitmaps for
  	 * these blocks, because they are marked as in-use from being in the
  	 * reserved inode, and will become GDT blocks (primary and backup).
  	 */

  	data[gdb_num % EXT4_ADDR_PER_BLOCK(sb)] = 0;

  	err = ext4_handle_dirty_metadata(handle, NULL, dind);
  	if (unlikely(err)) {
  		ext4_std_error(sb, err);
  		goto exit_inode;
  	}

  	inode->i_blocks -= (gdbackups + 1) * sb->s_blocksize >> 9;

  	ext4_mark_iloc_dirty(handle, inode, &iloc);

  	memset(gdb_bh->b_data, 0, sb->s_blocksize);
  	err = ext4_handle_dirty_metadata(handle, NULL, gdb_bh);

  	if (unlikely(err)) {
  		ext4_std_error(sb, err);
  		goto exit_inode;
  	}
  	brelse(dind);

  	o_group_desc = EXT4_SB(sb)->s_group_desc;

  	memcpy(n_group_desc, o_group_desc,

  	       EXT4_SB(sb)->s_gdb_count * sizeof(struct buffer_head *));

  	n_group_desc[gdb_num] = gdb_bh;

  	EXT4_SB(sb)->s_group_desc = n_group_desc;
  	EXT4_SB(sb)->s_gdb_count++;

  	ext4_kvfree(o_group_desc);

  	le16_add_cpu(&es->s_reserved_gdt_blocks, -1);

  	err = ext4_handle_dirty_metadata(handle, NULL, EXT4_SB(sb)->s_sbh);
  	if (err)
  		ext4_std_error(sb, err);

  	return err;

  
  exit_inode:

  	ext4_kvfree(n_group_desc);

  	/* ext4_handle_release_buffer(handle, iloc.bh); */

  	brelse(iloc.bh);
  exit_dindj:

  	/* ext4_handle_release_buffer(handle, dind); */

  exit_sbh:

  	/* ext4_handle_release_buffer(handle, EXT4_SB(sb)->s_sbh); */

  exit_dind:
  	brelse(dind);
  exit_bh:

  	brelse(gdb_bh);

  	ext4_debug("leaving with error %d
  ", err);

  	return err;
  }
  
  /*
   * Called when we are adding a new group which has a backup copy of each of
   * the GDT blocks (i.e. sparse group) and there are reserved GDT blocks.
   * We need to add these reserved backup GDT blocks to the resize inode, so
   * that they are kept for future resizing and not allocated to files.
   *
   * Each reserved backup GDT block will go into a different indirect block.
   * The indirect blocks are actually the primary reserved GDT blocks,
   * so we know in advance what their block numbers are.  We only get the
   * double-indirect block to verify it is pointing to the primary reserved
   * GDT blocks so we don't overwrite a data block by accident.  The reserved
   * backup GDT blocks are stored in their reserved primary GDT block.
   */
  static int reserve_backup_gdb(handle_t *handle, struct inode *inode,

  			      ext4_group_t group)

  {
  	struct super_block *sb = inode->i_sb;

  	int reserved_gdb =le16_to_cpu(EXT4_SB(sb)->s_es->s_reserved_gdt_blocks);

  	struct buffer_head **primary;
  	struct buffer_head *dind;

  	struct ext4_iloc iloc;
  	ext4_fsblk_t blk;

  	__le32 *data, *end;
  	int gdbackups = 0;
  	int res, i;
  	int err;

  	primary = kmalloc(reserved_gdb * sizeof(*primary), GFP_NOFS);

  	if (!primary)
  		return -ENOMEM;

  	data = EXT4_I(inode)->i_data + EXT4_DIND_BLOCK;

  	dind = sb_bread(sb, le32_to_cpu(*data));
  	if (!dind) {
  		err = -EIO;
  		goto exit_free;
  	}

  	blk = EXT4_SB(sb)->s_sbh->b_blocknr + 1 + EXT4_SB(sb)->s_gdb_count;

  	data = (__le32 *)dind->b_data + (EXT4_SB(sb)->s_gdb_count %
  					 EXT4_ADDR_PER_BLOCK(sb));

  	end = (__le32 *)dind->b_data + EXT4_ADDR_PER_BLOCK(sb);

  
  	/* Get each reserved primary GDT block and verify it holds backups */
  	for (res = 0; res < reserved_gdb; res++, blk++) {
  		if (le32_to_cpu(*data) != blk) {

  			ext4_warning(sb, "reserved block %llu"

  				     " not at offset %ld",
  				     blk,
  				     (long)(data - (__le32 *)dind->b_data));
  			err = -EINVAL;
  			goto exit_bh;
  		}
  		primary[res] = sb_bread(sb, blk);
  		if (!primary[res]) {
  			err = -EIO;
  			goto exit_bh;
  		}

  		gdbackups = verify_reserved_gdb(sb, group, primary[res]);
  		if (gdbackups < 0) {

  			brelse(primary[res]);
  			err = gdbackups;
  			goto exit_bh;
  		}
  		if (++data >= end)
  			data = (__le32 *)dind->b_data;
  	}
  
  	for (i = 0; i < reserved_gdb; i++) {

  		if ((err = ext4_journal_get_write_access(handle, primary[i]))) {

  			/*
  			int j;
  			for (j = 0; j < i; j++)

  				ext4_handle_release_buffer(handle, primary[j]);

  			 */
  			goto exit_bh;
  		}
  	}

  	if ((err = ext4_reserve_inode_write(handle, inode, &iloc)))

  		goto exit_bh;
  
  	/*
  	 * Finally we can add each of the reserved backup GDT blocks from
  	 * the new group to its reserved primary GDT block.
  	 */

  	blk = group * EXT4_BLOCKS_PER_GROUP(sb);

  	for (i = 0; i < reserved_gdb; i++) {
  		int err2;
  		data = (__le32 *)primary[i]->b_data;
  		/* printk("reserving backup %lu[%u] = %lu
  ",
  		       primary[i]->b_blocknr, gdbackups,
  		       blk + primary[i]->b_blocknr); */
  		data[gdbackups] = cpu_to_le32(blk + primary[i]->b_blocknr);

  		err2 = ext4_handle_dirty_metadata(handle, NULL, primary[i]);

  		if (!err)
  			err = err2;
  	}
  	inode->i_blocks += reserved_gdb * sb->s_blocksize >> 9;

  	ext4_mark_iloc_dirty(handle, inode, &iloc);

  
  exit_bh:
  	while (--res >= 0)
  		brelse(primary[res]);
  	brelse(dind);
  
  exit_free:
  	kfree(primary);
  
  	return err;
  }
  
  /*

   * Update the backup copies of the ext4 metadata.  These don't need to be part

   * of the main resize transaction, because e2fsck will re-write them if there
   * is a problem (basically only OOM will cause a problem).  However, we
   * _should_ update the backups if possible, in case the primary gets trashed
   * for some reason and we need to run e2fsck from a backup superblock.  The
   * important part is that the new block and inode counts are in the backup
   * superblocks, and the location of the new group metadata in the GDT backups.
   *

   * We do not need take the s_resize_lock for this, because these
   * blocks are not otherwise touched by the filesystem code when it is
   * mounted.  We don't need to worry about last changing from
   * sbi->s_groups_count, because the worst that can happen is that we
   * do not copy the full number of backups at this time.  The resize
   * which changed s_groups_count will backup again.

   */
  static void update_backups(struct super_block *sb,
  			   int blk_off, char *data, int size)
  {

  	struct ext4_sb_info *sbi = EXT4_SB(sb);

  	const ext4_group_t last = sbi->s_groups_count;

  	const int bpg = EXT4_BLOCKS_PER_GROUP(sb);

  	unsigned three = 1;
  	unsigned five = 5;
  	unsigned seven = 7;

  	ext4_group_t group;

  	int rest = sb->s_blocksize - size;
  	handle_t *handle;
  	int err = 0, err2;

  	handle = ext4_journal_start_sb(sb, EXT4_MAX_TRANS_DATA);

  	if (IS_ERR(handle)) {
  		group = 1;
  		err = PTR_ERR(handle);
  		goto exit_err;
  	}

  	while ((group = ext4_list_backups(sb, &three, &five, &seven)) < last) {

  		struct buffer_head *bh;
  
  		/* Out of journal space, and can't get more - abort - so sad */

  		if (ext4_handle_valid(handle) &&
  		    handle->h_buffer_credits == 0 &&

  		    ext4_journal_extend(handle, EXT4_MAX_TRANS_DATA) &&
  		    (err = ext4_journal_restart(handle, EXT4_MAX_TRANS_DATA)))

  			break;
  
  		bh = sb_getblk(sb, group * bpg + blk_off);
  		if (!bh) {
  			err = -EIO;
  			break;
  		}

  		ext4_debug("update metadata backup %#04lx
  ",

  			  (unsigned long)bh->b_blocknr);

  		if ((err = ext4_journal_get_write_access(handle, bh)))

  			break;
  		lock_buffer(bh);
  		memcpy(bh->b_data, data, size);
  		if (rest)
  			memset(bh->b_data + size, 0, rest);
  		set_buffer_uptodate(bh);
  		unlock_buffer(bh);

  		err = ext4_handle_dirty_metadata(handle, NULL, bh);
  		if (unlikely(err))
  			ext4_std_error(sb, err);

  		brelse(bh);
  	}

  	if ((err2 = ext4_journal_stop(handle)) && !err)

  		err = err2;
  
  	/*
  	 * Ugh! Need to have e2fsck write the backup copies.  It is too
  	 * late to revert the resize, we shouldn't fail just because of
  	 * the backup copies (they are only needed in case of corruption).
  	 *
  	 * However, if we got here we have a journal problem too, so we
  	 * can't really start a transaction to mark the superblock.
  	 * Chicken out and just set the flag on the hope it will be written
  	 * to disk, and if not - we will simply wait until next fsck.
  	 */
  exit_err:
  	if (err) {

  		ext4_warning(sb, "can't update backup for group %u (err %d), "

  			     "forcing fsck on next reboot", group, err);

  		sbi->s_mount_state &= ~EXT4_VALID_FS;
  		sbi->s_es->s_state &= cpu_to_le16(~EXT4_VALID_FS);

  		mark_buffer_dirty(sbi->s_sbh);
  	}
  }

  /*
   * ext4_add_new_descs() adds @count group descriptor of groups
   * starting at @group
   *
   * @handle: journal handle
   * @sb: super block
   * @group: the group no. of the first group desc to be added
   * @resize_inode: the resize inode
   * @count: number of group descriptors to be added
   */
  static int ext4_add_new_descs(handle_t *handle, struct super_block *sb,
  			      ext4_group_t group, struct inode *resize_inode,
  			      ext4_group_t count)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(sb);
  	struct ext4_super_block *es = sbi->s_es;
  	struct buffer_head *gdb_bh;
  	int i, gdb_off, gdb_num, err = 0;
  
  	for (i = 0; i < count; i++, group++) {
  		int reserved_gdb = ext4_bg_has_super(sb, group) ?
  			le16_to_cpu(es->s_reserved_gdt_blocks) : 0;
  
  		gdb_off = group % EXT4_DESC_PER_BLOCK(sb);
  		gdb_num = group / EXT4_DESC_PER_BLOCK(sb);
  
  		/*
  		 * We will only either add reserved group blocks to a backup group
  		 * or remove reserved blocks for the first group in a new group block.
  		 * Doing both would be mean more complex code, and sane people don't
  		 * use non-sparse filesystems anymore.  This is already checked above.
  		 */
  		if (gdb_off) {
  			gdb_bh = sbi->s_group_desc[gdb_num];
  			err = ext4_journal_get_write_access(handle, gdb_bh);
  
  			if (!err && reserved_gdb && ext4_bg_num_gdb(sb, group))
  				err = reserve_backup_gdb(handle, resize_inode, group);
  		} else
  			err = add_new_gdb(handle, resize_inode, group);
  		if (err)
  			break;
  	}
  	return err;
  }

  /*
   * ext4_setup_new_descs() will set up the group descriptor descriptors of a flex bg
   */
  static int ext4_setup_new_descs(handle_t *handle, struct super_block *sb,
  				struct ext4_new_flex_group_data *flex_gd)
  {
  	struct ext4_new_group_data	*group_data = flex_gd->groups;
  	struct ext4_group_desc		*gdp;
  	struct ext4_sb_info		*sbi = EXT4_SB(sb);
  	struct buffer_head		*gdb_bh;
  	ext4_group_t			group;
  	__u16				*bg_flags = flex_gd->bg_flags;
  	int				i, gdb_off, gdb_num, err = 0;
  	
  
  	for (i = 0; i < flex_gd->count; i++, group_data++, bg_flags++) {
  		group = group_data->group;
  
  		gdb_off = group % EXT4_DESC_PER_BLOCK(sb);
  		gdb_num = group / EXT4_DESC_PER_BLOCK(sb);
  
  		/*
  		 * get_write_access() has been called on gdb_bh by ext4_add_new_desc().
  		 */
  		gdb_bh = sbi->s_group_desc[gdb_num];
  		/* Update group descriptor block for new group */
  		gdp = (struct ext4_group_desc *)((char *)gdb_bh->b_data +
  						 gdb_off * EXT4_DESC_SIZE(sb));
  
  		memset(gdp, 0, EXT4_DESC_SIZE(sb));
  		ext4_block_bitmap_set(sb, gdp, group_data->block_bitmap);
  		ext4_inode_bitmap_set(sb, gdp, group_data->inode_bitmap);
  		ext4_inode_table_set(sb, gdp, group_data->inode_table);
  		ext4_free_group_clusters_set(sb, gdp,
  					     EXT4_B2C(sbi, group_data->free_blocks_count));
  		ext4_free_inodes_set(sb, gdp, EXT4_INODES_PER_GROUP(sb));
  		gdp->bg_flags = cpu_to_le16(*bg_flags);
  		gdp->bg_checksum = ext4_group_desc_csum(sbi, group, gdp);
  
  		err = ext4_handle_dirty_metadata(handle, NULL, gdb_bh);
  		if (unlikely(err)) {
  			ext4_std_error(sb, err);
  			break;
  		}
  
  		/*
  		 * We can allocate memory for mb_alloc based on the new group
  		 * descriptor
  		 */
  		err = ext4_mb_add_groupinfo(sb, group, gdp);
  		if (err)
  			break;
  	}
  	return err;
  }

  /*
   * ext4_update_super() updates the super block so that the newly added
   * groups can be seen by the filesystem.
   *
   * @sb: super block
   * @flex_gd: new added groups
   */
  static void ext4_update_super(struct super_block *sb,
  			     struct ext4_new_flex_group_data *flex_gd)
  {
  	ext4_fsblk_t blocks_count = 0;
  	ext4_fsblk_t free_blocks = 0;
  	ext4_fsblk_t reserved_blocks = 0;
  	struct ext4_new_group_data *group_data = flex_gd->groups;
  	struct ext4_sb_info *sbi = EXT4_SB(sb);
  	struct ext4_super_block *es = sbi->s_es;
  	int i;
  
  	BUG_ON(flex_gd->count == 0 || group_data == NULL);
  	/*
  	 * Make the new blocks and inodes valid next.  We do this before
  	 * increasing the group count so that once the group is enabled,
  	 * all of its blocks and inodes are already valid.
  	 *
  	 * We always allocate group-by-group, then block-by-block or
  	 * inode-by-inode within a group, so enabling these
  	 * blocks/inodes before the group is live won't actually let us
  	 * allocate the new space yet.
  	 */
  	for (i = 0; i < flex_gd->count; i++) {
  		blocks_count += group_data[i].blocks_count;
  		free_blocks += group_data[i].free_blocks_count;
  	}
  
  	reserved_blocks = ext4_r_blocks_count(es) * 100;
  	do_div(reserved_blocks, ext4_blocks_count(es));
  	reserved_blocks *= blocks_count;
  	do_div(reserved_blocks, 100);
  
  	ext4_blocks_count_set(es, ext4_blocks_count(es) + blocks_count);
  	le32_add_cpu(&es->s_inodes_count, EXT4_INODES_PER_GROUP(sb) *
  		     flex_gd->count);
  
  	/*
  	 * We need to protect s_groups_count against other CPUs seeing
  	 * inconsistent state in the superblock.
  	 *
  	 * The precise rules we use are:
  	 *
  	 * * Writers must perform a smp_wmb() after updating all
  	 *   dependent data and before modifying the groups count
  	 *
  	 * * Readers must perform an smp_rmb() after reading the groups
  	 *   count and before reading any dependent data.
  	 *
  	 * NB. These rules can be relaxed when checking the group count
  	 * while freeing data, as we can only allocate from a block
  	 * group after serialising against the group count, and we can
  	 * only then free after serialising in turn against that
  	 * allocation.
  	 */
  	smp_wmb();
  
  	/* Update the global fs size fields */
  	sbi->s_groups_count += flex_gd->count;
  
  	/* Update the reserved block counts only once the new group is
  	 * active. */
  	ext4_r_blocks_count_set(es, ext4_r_blocks_count(es) +
  				reserved_blocks);
  
  	/* Update the free space counts */
  	percpu_counter_add(&sbi->s_freeclusters_counter,
  			   EXT4_B2C(sbi, free_blocks));
  	percpu_counter_add(&sbi->s_freeinodes_counter,
  			   EXT4_INODES_PER_GROUP(sb) * flex_gd->count);
  
  	if (EXT4_HAS_INCOMPAT_FEATURE(sb,
  				      EXT4_FEATURE_INCOMPAT_FLEX_BG) &&
  	    sbi->s_log_groups_per_flex) {
  		ext4_group_t flex_group;
  		flex_group = ext4_flex_group(sbi, group_data[0].group);
  		atomic_add(EXT4_B2C(sbi, free_blocks),
  			   &sbi->s_flex_groups[flex_group].free_clusters);
  		atomic_add(EXT4_INODES_PER_GROUP(sb) * flex_gd->count,
  			   &sbi->s_flex_groups[flex_group].free_inodes);
  	}
  
  	if (test_opt(sb, DEBUG))
  		printk(KERN_DEBUG "EXT4-fs: added group %u:"
  		       "%llu blocks(%llu free %llu reserved)
  ", flex_gd->count,
  		       blocks_count, free_blocks, reserved_blocks);
  }

  /* Add a flex group to an fs. Ensure we handle all possible error conditions
   * _before_ we start modifying the filesystem, because we cannot abort the
   * transaction and not have it write the data to disk.
   */
  static int ext4_flex_group_add(struct super_block *sb,
  			       struct inode *resize_inode,
  			       struct ext4_new_flex_group_data *flex_gd)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(sb);
  	struct ext4_super_block *es = sbi->s_es;
  	ext4_fsblk_t o_blocks_count;
  	ext4_grpblk_t last;
  	ext4_group_t group;
  	handle_t *handle;
  	unsigned reserved_gdb;
  	int err = 0, err2 = 0, credit;
  
  	BUG_ON(!flex_gd->count || !flex_gd->groups || !flex_gd->bg_flags);
  
  	reserved_gdb = le16_to_cpu(es->s_reserved_gdt_blocks);
  	o_blocks_count = ext4_blocks_count(es);
  	ext4_get_group_no_and_offset(sb, o_blocks_count, &group, &last);
  	BUG_ON(last);
  
  	err = setup_new_flex_group_blocks(sb, flex_gd);
  	if (err)
  		goto exit;
  	/*
  	 * We will always be modifying at least the superblock and  GDT
  	 * block.  If we are adding a group past the last current GDT block,
  	 * we will also modify the inode and the dindirect block.  If we
  	 * are adding a group with superblock/GDT backups  we will also
  	 * modify each of the reserved GDT dindirect blocks.
  	 */
  	credit = flex_gd->count * 4 + reserved_gdb;
  	handle = ext4_journal_start_sb(sb, credit);
  	if (IS_ERR(handle)) {
  		err = PTR_ERR(handle);
  		goto exit;
  	}
  
  	err = ext4_journal_get_write_access(handle, sbi->s_sbh);
  	if (err)
  		goto exit_journal;
  
  	group = flex_gd->groups[0].group;
  	BUG_ON(group != EXT4_SB(sb)->s_groups_count);
  	err = ext4_add_new_descs(handle, sb, group,
  				resize_inode, flex_gd->count);
  	if (err)
  		goto exit_journal;
  
  	err = ext4_setup_new_descs(handle, sb, flex_gd);
  	if (err)
  		goto exit_journal;
  
  	ext4_update_super(sb, flex_gd);
  
  	err = ext4_handle_dirty_super(handle, sb);
  
  exit_journal:
  	err2 = ext4_journal_stop(handle);
  	if (!err)
  		err = err2;
  
  	if (!err) {
  		int i;
  		update_backups(sb, sbi->s_sbh->b_blocknr, (char *)es,
  			       sizeof(struct ext4_super_block));
  		for (i = 0; i < flex_gd->count; i++, group++) {
  			struct buffer_head *gdb_bh;
  			int gdb_num;
  			gdb_num = group / EXT4_BLOCKS_PER_GROUP(sb);
  			gdb_bh = sbi->s_group_desc[gdb_num];
  			update_backups(sb, gdb_bh->b_blocknr, gdb_bh->b_data,
  				       gdb_bh->b_size);
  		}
  	}
  exit:
  	return err;
  }

  static int ext4_setup_next_flex_gd(struct super_block *sb,
  				    struct ext4_new_flex_group_data *flex_gd,
  				    ext4_fsblk_t n_blocks_count,
  				    unsigned long flexbg_size)
  {
  	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
  	struct ext4_new_group_data *group_data = flex_gd->groups;
  	ext4_fsblk_t o_blocks_count;
  	ext4_group_t n_group;
  	ext4_group_t group;
  	ext4_group_t last_group;
  	ext4_grpblk_t last;
  	ext4_grpblk_t blocks_per_group;
  	unsigned long i;
  
  	blocks_per_group = EXT4_BLOCKS_PER_GROUP(sb);
  
  	o_blocks_count = ext4_blocks_count(es);
  
  	if (o_blocks_count == n_blocks_count)
  		return 0;
  
  	ext4_get_group_no_and_offset(sb, o_blocks_count, &group, &last);
  	BUG_ON(last);
  	ext4_get_group_no_and_offset(sb, n_blocks_count - 1, &n_group, &last);
  
  	last_group = group | (flexbg_size - 1);
  	if (last_group > n_group)
  		last_group = n_group;
  
  	flex_gd->count = last_group - group + 1;
  
  	for (i = 0; i < flex_gd->count; i++) {
  		int overhead;
  
  		group_data[i].group = group + i;
  		group_data[i].blocks_count = blocks_per_group;
  		overhead = ext4_bg_has_super(sb, group + i) ?
  			   (1 + ext4_bg_num_gdb(sb, group + i) +
  			    le16_to_cpu(es->s_reserved_gdt_blocks)) : 0;
  		group_data[i].free_blocks_count = blocks_per_group - overhead;
  		if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
  					       EXT4_FEATURE_RO_COMPAT_GDT_CSUM))
  			flex_gd->bg_flags[i] = EXT4_BG_BLOCK_UNINIT |
  					       EXT4_BG_INODE_UNINIT;
  		else
  			flex_gd->bg_flags[i] = EXT4_BG_INODE_ZEROED;
  	}
  
  	if (last_group == n_group &&
  	    EXT4_HAS_RO_COMPAT_FEATURE(sb,
  				       EXT4_FEATURE_RO_COMPAT_GDT_CSUM))
  		/* We need to initialize block bitmap of last group. */
  		flex_gd->bg_flags[i - 1] &= ~EXT4_BG_BLOCK_UNINIT;
  
  	if ((last_group == n_group) && (last != blocks_per_group - 1)) {
  		group_data[i - 1].blocks_count = last + 1;
  		group_data[i - 1].free_blocks_count -= blocks_per_group-
  					last - 1;
  	}
  
  	return 1;
  }

  /* Add group descriptor data to an existing or new group descriptor block.
   * Ensure we handle all possible error conditions _before_ we start modifying
   * the filesystem, because we cannot abort the transaction and not have it
   * write the data to disk.
   *
   * If we are on a GDT block boundary, we need to get the reserved GDT block.
   * Otherwise, we may need to add backup GDT blocks for a sparse group.
   *
   * We only need to hold the superblock lock while we are actually adding
   * in the new group's counts to the superblock.  Prior to that we have
   * not really "added" the group at all.  We re-check that we are still
   * adding in the last group in case things have changed since verifying.
   */

  int ext4_group_add(struct super_block *sb, struct ext4_new_group_data *input)

  {

  	struct ext4_new_flex_group_data flex_gd;

  	struct ext4_sb_info *sbi = EXT4_SB(sb);
  	struct ext4_super_block *es = sbi->s_es;
  	int reserved_gdb = ext4_bg_has_super(sb, input->group) ?

  		le16_to_cpu(es->s_reserved_gdt_blocks) : 0;

  	struct inode *inode = NULL;

  	int gdb_off, gdb_num;

  	int err;
  	__u16 bg_flags = 0;

  	gdb_num = input->group / EXT4_DESC_PER_BLOCK(sb);
  	gdb_off = input->group % EXT4_DESC_PER_BLOCK(sb);

  	if (gdb_off == 0 && !EXT4_HAS_RO_COMPAT_FEATURE(sb,
  					EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER)) {

  		ext4_warning(sb, "Can't resize non-sparse filesystem further");

  		return -EPERM;
  	}

  	if (ext4_blocks_count(es) + input->blocks_count <
  	    ext4_blocks_count(es)) {

  		ext4_warning(sb, "blocks_count overflow");

  		return -EINVAL;
  	}

  	if (le32_to_cpu(es->s_inodes_count) + EXT4_INODES_PER_GROUP(sb) <

  	    le32_to_cpu(es->s_inodes_count)) {

  		ext4_warning(sb, "inodes_count overflow");

  		return -EINVAL;
  	}
  
  	if (reserved_gdb || gdb_off == 0) {

  		if (!EXT4_HAS_COMPAT_FEATURE(sb,

  					     EXT4_FEATURE_COMPAT_RESIZE_INODE)
  		    || !le16_to_cpu(es->s_reserved_gdt_blocks)) {

  			ext4_warning(sb,

  				     "No reserved GDT blocks, can't resize");
  			return -EPERM;
  		}

  		inode = ext4_iget(sb, EXT4_RESIZE_INO);
  		if (IS_ERR(inode)) {

  			ext4_warning(sb, "Error opening resize inode");

  			return PTR_ERR(inode);

  		}
  	}

  	err = verify_group_input(sb, input);

  	if (err)

  		goto out;

  	flex_gd.count = 1;
  	flex_gd.groups = input;
  	flex_gd.bg_flags = &bg_flags;
  	err = ext4_flex_group_add(sb, inode, &flex_gd);
  out:

  	iput(inode);
  	return err;

  } /* ext4_group_add */

  /*

   * extend a group without checking assuming that checking has been done.
   */
  static int ext4_group_extend_no_check(struct super_block *sb,
  				      ext4_fsblk_t o_blocks_count, ext4_grpblk_t add)
  {
  	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
  	handle_t *handle;
  	int err = 0, err2;
  
  	/* We will update the superblock, one block bitmap, and
  	 * one group descriptor via ext4_group_add_blocks().
  	 */
  	handle = ext4_journal_start_sb(sb, 3);
  	if (IS_ERR(handle)) {
  		err = PTR_ERR(handle);
  		ext4_warning(sb, "error %d on journal start", err);
  		return err;
  	}
  
  	err = ext4_journal_get_write_access(handle, EXT4_SB(sb)->s_sbh);
  	if (err) {
  		ext4_warning(sb, "error %d on journal write access", err);
  		goto errout;
  	}
  
  	ext4_blocks_count_set(es, o_blocks_count + add);
  	ext4_debug("freeing blocks %llu through %llu
  ", o_blocks_count,
  		   o_blocks_count + add);
  	/* We add the blocks to the bitmap and set the group need init bit */
  	err = ext4_group_add_blocks(handle, sb, o_blocks_count, add);
  	if (err)
  		goto errout;
  	ext4_handle_dirty_super(handle, sb);
  	ext4_debug("freed blocks %llu through %llu
  ", o_blocks_count,
  		   o_blocks_count + add);
  errout:
  	err2 = ext4_journal_stop(handle);
  	if (err2 && !err)
  		err = err2;
  
  	if (!err) {
  		if (test_opt(sb, DEBUG))
  			printk(KERN_DEBUG "EXT4-fs: extended group to %llu "
  			       "blocks
  ", ext4_blocks_count(es));
  		update_backups(sb, EXT4_SB(sb)->s_sbh->b_blocknr, (char *)es,
  			       sizeof(struct ext4_super_block));
  	}
  	return err;
  }
  
  /*

   * Extend the filesystem to the new number of blocks specified.  This entry

   * point is only used to extend the current filesystem to the end of the last
   * existing group.  It can be accessed via ioctl, or by "remount,resize=<size>"
   * for emergencies (because it has no dependencies on reserved blocks).
   *

   * If we _really_ wanted, we could use default values to call ext4_group_add()

   * allow the "remount" trick to work for arbitrary resizing, assuming enough
   * GDT blocks are reserved to grow to the desired size.
   */

  int ext4_group_extend(struct super_block *sb, struct ext4_super_block *es,
  		      ext4_fsblk_t n_blocks_count)

  {

  	ext4_fsblk_t o_blocks_count;

  	ext4_grpblk_t last;
  	ext4_grpblk_t add;

  	struct buffer_head *bh;

  	int err;

  	ext4_group_t group;

  	o_blocks_count = ext4_blocks_count(es);

  
  	if (test_opt(sb, DEBUG))

  		printk(KERN_DEBUG "EXT4-fs: extending last group from %llu to %llu blocks
  ",

  		       o_blocks_count, n_blocks_count);
  
  	if (n_blocks_count == 0 || n_blocks_count == o_blocks_count)
  		return 0;
  
  	if (n_blocks_count > (sector_t)(~0ULL) >> (sb->s_blocksize_bits - 9)) {

  		printk(KERN_ERR "EXT4-fs: filesystem on %s:"

  			" too large to resize to %llu blocks safely
  ",

  			sb->s_id, n_blocks_count);
  		if (sizeof(sector_t) < 8)

  			ext4_warning(sb, "CONFIG_LBDAF not enabled");

  		return -EINVAL;
  	}
  
  	if (n_blocks_count < o_blocks_count) {

  		ext4_warning(sb, "can't shrink FS - resize aborted");

  		return -EINVAL;

  	}
  
  	/* Handle the remaining blocks in the last group only. */

  	ext4_get_group_no_and_offset(sb, o_blocks_count, &group, &last);

  
  	if (last == 0) {

  		ext4_warning(sb, "need to use ext2online to resize further");

  		return -EPERM;
  	}

  	add = EXT4_BLOCKS_PER_GROUP(sb) - last;

  
  	if (o_blocks_count + add < o_blocks_count) {

  		ext4_warning(sb, "blocks_count overflow");

  		return -EINVAL;
  	}
  
  	if (o_blocks_count + add > n_blocks_count)
  		add = n_blocks_count - o_blocks_count;
  
  	if (o_blocks_count + add < n_blocks_count)

  		ext4_warning(sb, "will only finish group (%llu blocks, %u new)",

  			     o_blocks_count + add, add);
  
  	/* See if the device is actually as big as what was requested */

  	bh = sb_bread(sb, o_blocks_count + add - 1);

  	if (!bh) {

  		ext4_warning(sb, "can't read last block, resize aborted");

  		return -ENOSPC;
  	}
  	brelse(bh);

  	err = ext4_group_extend_no_check(sb, o_blocks_count, add);

  	return err;

  } /* ext4_group_extend */

  
  /*
   * ext4_resize_fs() resizes a fs to new size specified by @n_blocks_count
   *
   * @sb: super block of the fs to be resized
   * @n_blocks_count: the number of blocks resides in the resized fs
   */
  int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count)
  {
  	struct ext4_new_flex_group_data *flex_gd = NULL;
  	struct ext4_sb_info *sbi = EXT4_SB(sb);
  	struct ext4_super_block *es = sbi->s_es;
  	struct buffer_head *bh;
  	struct inode *resize_inode;
  	ext4_fsblk_t o_blocks_count;
  	ext4_group_t o_group;
  	ext4_group_t n_group;
  	ext4_grpblk_t offset;
  	unsigned long n_desc_blocks;
  	unsigned long o_desc_blocks;
  	unsigned long desc_blocks;
  	int err = 0, flexbg_size = 1;
  
  	o_blocks_count = ext4_blocks_count(es);
  
  	if (test_opt(sb, DEBUG))
  		printk(KERN_DEBUG "EXT4-fs: resizing filesystem from %llu "
  		       "upto %llu blocks
  ", o_blocks_count, n_blocks_count);
  
  	if (n_blocks_count < o_blocks_count) {
  		/* On-line shrinking not supported */
  		ext4_warning(sb, "can't shrink FS - resize aborted");
  		return -EINVAL;
  	}
  
  	if (n_blocks_count == o_blocks_count)
  		/* Nothing need to do */
  		return 0;
  
  	ext4_get_group_no_and_offset(sb, n_blocks_count - 1, &n_group, &offset);
  	ext4_get_group_no_and_offset(sb, o_blocks_count, &o_group, &offset);
  
  	n_desc_blocks = (n_group + EXT4_DESC_PER_BLOCK(sb)) /
  			EXT4_DESC_PER_BLOCK(sb);
  	o_desc_blocks = (sbi->s_groups_count + EXT4_DESC_PER_BLOCK(sb) - 1) /
  			EXT4_DESC_PER_BLOCK(sb);
  	desc_blocks = n_desc_blocks - o_desc_blocks;
  
  	if (desc_blocks &&
  	    (!EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_RESIZE_INODE) ||
  	     le16_to_cpu(es->s_reserved_gdt_blocks) < desc_blocks)) {
  		ext4_warning(sb, "No reserved GDT blocks, can't resize");
  		return -EPERM;
  	}
  
  	resize_inode = ext4_iget(sb, EXT4_RESIZE_INO);
  	if (IS_ERR(resize_inode)) {
  		ext4_warning(sb, "Error opening resize inode");
  		return PTR_ERR(resize_inode);
  	}
  
  	/* See if the device is actually as big as what was requested */
  	bh = sb_bread(sb, n_blocks_count - 1);
  	if (!bh) {
  		ext4_warning(sb, "can't read last block, resize aborted");
  		return -ENOSPC;
  	}
  	brelse(bh);
  
  	if (offset != 0) {
  		/* extend the last group */
  		ext4_grpblk_t add;
  		add = EXT4_BLOCKS_PER_GROUP(sb) - offset;
  		err = ext4_group_extend_no_check(sb, o_blocks_count, add);
  		if (err)
  			goto out;
  	}
  
  	if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG) &&
  	    es->s_log_groups_per_flex)
  		flexbg_size = 1 << es->s_log_groups_per_flex;
  
  	o_blocks_count = ext4_blocks_count(es);
  	if (o_blocks_count == n_blocks_count)
  		goto out;
  
  	flex_gd = alloc_flex_gd(flexbg_size);
  	if (flex_gd == NULL) {
  		err = -ENOMEM;
  		goto out;
  	}
  
  	/* Add flex groups. Note that a regular group is a
  	 * flex group with 1 group.
  	 */
  	while (ext4_setup_next_flex_gd(sb, flex_gd, n_blocks_count,
  					      flexbg_size)) {
  		ext4_alloc_group_tables(sb, flex_gd, flexbg_size);
  		err = ext4_flex_group_add(sb, resize_inode, flex_gd);
  		if (unlikely(err))
  			break;
  	}
  
  out:
  	if (flex_gd)
  		free_flex_gd(flex_gd);
  
  	iput(resize_inode);
  	if (test_opt(sb, DEBUG))
  		printk(KERN_DEBUG "EXT4-fs: resized filesystem from %llu "
  		       "upto %llu blocks
  ", o_blocks_count, n_blocks_count);
  	return err;
  }