/*
   *  linux/fs/ext3/resize.c
   *
   * Support for resizing an ext3 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.
   */
  
  #include <linux/config.h>
  
  #define EXT3FS_DEBUG
  
  #include <linux/sched.h>
  #include <linux/smp_lock.h>
  #include <linux/ext3_jbd.h>
  
  #include <linux/errno.h>
  #include <linux/slab.h>
  
  
  #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 ext3_new_group_data *input)
  {
  	struct ext3_sb_info *sbi = EXT3_SB(sb);
  	struct ext3_super_block *es = sbi->s_es;

  	ext3_fsblk_t start = le32_to_cpu(es->s_blocks_count);
  	ext3_fsblk_t end = start + input->blocks_count;

  	unsigned group = input->group;

  	ext3_fsblk_t itend = input->inode_table + sbi->s_itb_per_group;

  	unsigned overhead = ext3_bg_has_super(sb, group) ?
  		(1 + ext3_bg_num_gdb(sb, group) +
  		 le16_to_cpu(es->s_reserved_gdt_blocks)) : 0;

  	ext3_fsblk_t metaend = start + overhead;

  	struct buffer_head *bh = NULL;

  	ext3_grpblk_t free_blocks_count;

  	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 "EXT3-fs: adding %s group %u: %u blocks "
  		       "(%d free, %u reserved)
  ",
  		       ext3_bg_has_super(sb, input->group) ? "normal" :
  		       "no-super", input->group, input->blocks_count,
  		       free_blocks_count, input->reserved_blocks);
  
  	if (group != sbi->s_groups_count)
  		ext3_warning(sb, __FUNCTION__,
  			     "Cannot add at group %u (only %lu groups)",
  			     input->group, sbi->s_groups_count);
  	else if ((start - le32_to_cpu(es->s_first_data_block)) %
  		 EXT3_BLOCKS_PER_GROUP(sb))
  		ext3_warning(sb, __FUNCTION__, "Last group not full");
  	else if (input->reserved_blocks > input->blocks_count / 5)
  		ext3_warning(sb, __FUNCTION__, "Reserved blocks too high (%u)",
  			     input->reserved_blocks);
  	else if (free_blocks_count < 0)
  		ext3_warning(sb, __FUNCTION__, "Bad blocks count %u",
  			     input->blocks_count);
  	else if (!(bh = sb_bread(sb, end - 1)))

  		ext3_warning(sb, __FUNCTION__,
  			     "Cannot read last block ("E3FSBLK")",

  			     end - 1);
  	else if (outside(input->block_bitmap, start, end))
  		ext3_warning(sb, __FUNCTION__,
  			     "Block bitmap not in group (block %u)",
  			     input->block_bitmap);
  	else if (outside(input->inode_bitmap, start, end))
  		ext3_warning(sb, __FUNCTION__,
  			     "Inode bitmap not in group (block %u)",
  			     input->inode_bitmap);
  	else if (outside(input->inode_table, start, end) ||
  	         outside(itend - 1, start, end))
  		ext3_warning(sb, __FUNCTION__,

  			     "Inode table not in group (blocks %u-"E3FSBLK")",

  			     input->inode_table, itend - 1);
  	else if (input->inode_bitmap == input->block_bitmap)
  		ext3_warning(sb, __FUNCTION__,
  			     "Block bitmap same as inode bitmap (%u)",
  			     input->block_bitmap);
  	else if (inside(input->block_bitmap, input->inode_table, itend))
  		ext3_warning(sb, __FUNCTION__,

  			     "Block bitmap (%u) in inode table (%u-"E3FSBLK")",

  			     input->block_bitmap, input->inode_table, itend-1);
  	else if (inside(input->inode_bitmap, input->inode_table, itend))
  		ext3_warning(sb, __FUNCTION__,

  			     "Inode bitmap (%u) in inode table (%u-"E3FSBLK")",

  			     input->inode_bitmap, input->inode_table, itend-1);
  	else if (inside(input->block_bitmap, start, metaend))
  		ext3_warning(sb, __FUNCTION__,

  			     "Block bitmap (%u) in GDT table"
  			     " ("E3FSBLK"-"E3FSBLK")",

  			     input->block_bitmap, start, metaend - 1);
  	else if (inside(input->inode_bitmap, start, metaend))
  		ext3_warning(sb, __FUNCTION__,

  			     "Inode bitmap (%u) in GDT table"
  			     " ("E3FSBLK"-"E3FSBLK")",

  			     input->inode_bitmap, start, metaend - 1);
  	else if (inside(input->inode_table, start, metaend) ||
  	         inside(itend - 1, start, metaend))
  		ext3_warning(sb, __FUNCTION__,

  			     "Inode table (%u-"E3FSBLK") overlaps"
  			     "GDT table ("E3FSBLK"-"E3FSBLK")",

  			     input->inode_table, itend - 1, start, metaend - 1);
  	else
  		err = 0;
  	brelse(bh);
  
  	return err;
  }
  
  static struct buffer_head *bclean(handle_t *handle, struct super_block *sb,

  				  ext3_fsblk_t blk)

  {
  	struct buffer_head *bh;
  	int err;
  
  	bh = sb_getblk(sb, blk);

  	if (!bh)
  		return ERR_PTR(-EIO);

  	if ((err = ext3_journal_get_write_access(handle, bh))) {
  		brelse(bh);
  		bh = ERR_PTR(err);
  	} else {
  		lock_buffer(bh);
  		memset(bh->b_data, 0, sb->s_blocksize);
  		set_buffer_uptodate(bh);
  		unlock_buffer(bh);
  	}
  
  	return bh;
  }
  
  /*
   * To avoid calling the atomic setbit hundreds or thousands of times, we only
   * need to use it within a single byte (to ensure we get endianness right).
   * We can use memset for the rest of the bitmap as there are no other users.
   */
  static void mark_bitmap_end(int start_bit, int end_bit, char *bitmap)
  {
  	int i;
  
  	if (start_bit >= end_bit)
  		return;
  
  	ext3_debug("mark end bits +%d through +%d used
  ", start_bit, end_bit);
  	for (i = start_bit; i < ((start_bit + 7) & ~7UL); i++)
  		ext3_set_bit(i, bitmap);
  	if (i < end_bit)
  		memset(bitmap + (i >> 3), 0xff, (end_bit - i) >> 3);
  }
  
  /*
   * Set up the block and inode bitmaps, and the inode table for the new group.
   * 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.
   */
  static int setup_new_group_blocks(struct super_block *sb,
  				  struct ext3_new_group_data *input)
  {
  	struct ext3_sb_info *sbi = EXT3_SB(sb);

  	ext3_fsblk_t start = ext3_group_first_block_no(sb, input->group);

  	int reserved_gdb = ext3_bg_has_super(sb, input->group) ?
  		le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks) : 0;
  	unsigned long gdblocks = ext3_bg_num_gdb(sb, input->group);
  	struct buffer_head *bh;
  	handle_t *handle;

  	ext3_fsblk_t block;

  	ext3_grpblk_t bit;

  	int i;
  	int err = 0, err2;
  
  	handle = ext3_journal_start_sb(sb, reserved_gdb + gdblocks +
  				       2 + sbi->s_itb_per_group);
  	if (IS_ERR(handle))
  		return PTR_ERR(handle);
  
  	lock_super(sb);
  	if (input->group != sbi->s_groups_count) {
  		err = -EBUSY;
  		goto exit_journal;
  	}
  
  	if (IS_ERR(bh = bclean(handle, sb, input->block_bitmap))) {
  		err = PTR_ERR(bh);
  		goto exit_journal;
  	}
  
  	if (ext3_bg_has_super(sb, input->group)) {
  		ext3_debug("mark backup superblock %#04lx (+0)
  ", start);
  		ext3_set_bit(0, bh->b_data);
  	}
  
  	/* Copy all of the GDT blocks into the backup in this group */
  	for (i = 0, bit = 1, block = start + 1;
  	     i < gdblocks; i++, block++, bit++) {
  		struct buffer_head *gdb;
  
  		ext3_debug("update backup group %#04lx (+%d)
  ", block, bit);
  
  		gdb = sb_getblk(sb, block);

  		if (!gdb) {
  			err = -EIO;
  			goto exit_bh;
  		}

  		if ((err = ext3_journal_get_write_access(handle, gdb))) {
  			brelse(gdb);
  			goto exit_bh;
  		}
  		lock_buffer(bh);

  		memcpy(gdb->b_data, sbi->s_group_desc[i]->b_data, bh->b_size);

  		set_buffer_uptodate(gdb);
  		unlock_buffer(bh);
  		ext3_journal_dirty_metadata(handle, gdb);
  		ext3_set_bit(bit, bh->b_data);
  		brelse(gdb);
  	}
  
  	/* Zero out all of the reserved backup group descriptor table blocks */
  	for (i = 0, bit = gdblocks + 1, block = start + bit;
  	     i < reserved_gdb; i++, block++, bit++) {
  		struct buffer_head *gdb;
  
  		ext3_debug("clear reserved block %#04lx (+%d)
  ", block, bit);
  
  		if (IS_ERR(gdb = bclean(handle, sb, block))) {
  			err = PTR_ERR(bh);
  			goto exit_bh;
  		}
  		ext3_journal_dirty_metadata(handle, gdb);
  		ext3_set_bit(bit, bh->b_data);
  		brelse(gdb);
  	}
  	ext3_debug("mark block bitmap %#04x (+%ld)
  ", input->block_bitmap,
  		   input->block_bitmap - start);
  	ext3_set_bit(input->block_bitmap - start, bh->b_data);
  	ext3_debug("mark inode bitmap %#04x (+%ld)
  ", input->inode_bitmap,
  		   input->inode_bitmap - start);
  	ext3_set_bit(input->inode_bitmap - start, bh->b_data);
  
  	/* Zero out all of the inode table blocks */
  	for (i = 0, block = input->inode_table, bit = block - start;
  	     i < sbi->s_itb_per_group; i++, bit++, block++) {
  		struct buffer_head *it;

  		ext3_debug("clear inode block %#04lx (+%d)
  ", block, bit);

  		if (IS_ERR(it = bclean(handle, sb, block))) {
  			err = PTR_ERR(it);
  			goto exit_bh;
  		}
  		ext3_journal_dirty_metadata(handle, it);
  		brelse(it);
  		ext3_set_bit(bit, bh->b_data);
  	}
  	mark_bitmap_end(input->blocks_count, EXT3_BLOCKS_PER_GROUP(sb),
  			bh->b_data);
  	ext3_journal_dirty_metadata(handle, bh);
  	brelse(bh);
  
  	/* Mark unused entries in inode bitmap used */
  	ext3_debug("clear inode bitmap %#04x (+%ld)
  ",
  		   input->inode_bitmap, input->inode_bitmap - start);
  	if (IS_ERR(bh = bclean(handle, sb, input->inode_bitmap))) {
  		err = PTR_ERR(bh);
  		goto exit_journal;
  	}
  
  	mark_bitmap_end(EXT3_INODES_PER_GROUP(sb), EXT3_BLOCKS_PER_GROUP(sb),
  			bh->b_data);
  	ext3_journal_dirty_metadata(handle, bh);
  exit_bh:
  	brelse(bh);
  
  exit_journal:
  	unlock_super(sb);
  	if ((err2 = ext3_journal_stop(handle)) && !err)
  		err = err2;
  
  	return err;
  }
  
  /*
   * Iterate through the groups which hold BACKUP superblock/GDT copies in an
   * ext3 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 ext3_list_backups(struct super_block *sb, unsigned *three,
  				  unsigned *five, unsigned *seven)
  {
  	unsigned *min = three;
  	int mult = 3;
  	unsigned ret;
  
  	if (!EXT3_HAS_RO_COMPAT_FEATURE(sb,
  					EXT3_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,
  			       struct buffer_head *primary)
  {

  	const ext3_fsblk_t blk = primary->b_blocknr;

  	const unsigned long end = EXT3_SB(sb)->s_groups_count;
  	unsigned three = 1;
  	unsigned five = 5;
  	unsigned seven = 7;
  	unsigned grp;
  	__u32 *p = (__u32 *)primary->b_data;
  	int gdbackups = 0;
  
  	while ((grp = ext3_list_backups(sb, &three, &five, &seven)) < end) {
  		if (le32_to_cpu(*p++) != grp * EXT3_BLOCKS_PER_GROUP(sb) + blk){
  			ext3_warning(sb, __FUNCTION__,

  				     "reserved GDT "E3FSBLK
  				     " missing grp %d ("E3FSBLK")",

  				     blk, grp,
  				     grp * EXT3_BLOCKS_PER_GROUP(sb) + blk);
  			return -EINVAL;
  		}
  		if (++gdbackups > EXT3_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,
  		       struct ext3_new_group_data *input,
  		       struct buffer_head **primary)
  {
  	struct super_block *sb = inode->i_sb;
  	struct ext3_super_block *es = EXT3_SB(sb)->s_es;
  	unsigned long gdb_num = input->group / EXT3_DESC_PER_BLOCK(sb);

  	ext3_fsblk_t gdblock = EXT3_SB(sb)->s_sbh->b_blocknr + 1 + gdb_num;

  	struct buffer_head **o_group_desc, **n_group_desc;
  	struct buffer_head *dind;
  	int gdbackups;
  	struct ext3_iloc iloc;
  	__u32 *data;
  	int err;
  
  	if (test_opt(sb, DEBUG))
  		printk(KERN_DEBUG
  		       "EXT3-fs: ext3_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 (EXT3_SB(sb)->s_sbh->b_blocknr !=
  	    le32_to_cpu(EXT3_SB(sb)->s_es->s_first_data_block)) {
  		ext3_warning(sb, __FUNCTION__,

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

  			(unsigned long long)EXT3_SB(sb)->s_sbh->b_blocknr);
  		return -EPERM;
  	}
  
  	*primary = sb_bread(sb, gdblock);
  	if (!*primary)
  		return -EIO;
  
  	if ((gdbackups = verify_reserved_gdb(sb, *primary)) < 0) {
  		err = gdbackups;
  		goto exit_bh;
  	}
  
  	data = EXT3_I(inode)->i_data + EXT3_DIND_BLOCK;
  	dind = sb_bread(sb, le32_to_cpu(*data));
  	if (!dind) {
  		err = -EIO;
  		goto exit_bh;
  	}
  
  	data = (__u32 *)dind->b_data;
  	if (le32_to_cpu(data[gdb_num % EXT3_ADDR_PER_BLOCK(sb)]) != gdblock) {
  		ext3_warning(sb, __FUNCTION__,

  			     "new group %u GDT block "E3FSBLK" not reserved",

  			     input->group, gdblock);
  		err = -EINVAL;
  		goto exit_dind;
  	}
  
  	if ((err = ext3_journal_get_write_access(handle, EXT3_SB(sb)->s_sbh)))
  		goto exit_dind;
  
  	if ((err = ext3_journal_get_write_access(handle, *primary)))
  		goto exit_sbh;
  
  	if ((err = ext3_journal_get_write_access(handle, dind)))
  		goto exit_primary;
  
  	/* ext3_reserve_inode_write() gets a reference on the iloc */
  	if ((err = ext3_reserve_inode_write(handle, inode, &iloc)))
  		goto exit_dindj;
  
  	n_group_desc = (struct buffer_head **)kmalloc((gdb_num + 1) *
  				sizeof(struct buffer_head *), GFP_KERNEL);
  	if (!n_group_desc) {
  		err = -ENOMEM;
  		ext3_warning (sb, __FUNCTION__,
  			      "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 % EXT3_ADDR_PER_BLOCK(sb)] = 0;
  	ext3_journal_dirty_metadata(handle, dind);
  	brelse(dind);
  	inode->i_blocks -= (gdbackups + 1) * sb->s_blocksize >> 9;
  	ext3_mark_iloc_dirty(handle, inode, &iloc);
  	memset((*primary)->b_data, 0, sb->s_blocksize);
  	ext3_journal_dirty_metadata(handle, *primary);
  
  	o_group_desc = EXT3_SB(sb)->s_group_desc;
  	memcpy(n_group_desc, o_group_desc,
  	       EXT3_SB(sb)->s_gdb_count * sizeof(struct buffer_head *));
  	n_group_desc[gdb_num] = *primary;
  	EXT3_SB(sb)->s_group_desc = n_group_desc;
  	EXT3_SB(sb)->s_gdb_count++;
  	kfree(o_group_desc);
  
  	es->s_reserved_gdt_blocks =
  		cpu_to_le16(le16_to_cpu(es->s_reserved_gdt_blocks) - 1);
  	ext3_journal_dirty_metadata(handle, EXT3_SB(sb)->s_sbh);
  
  	return 0;
  
  exit_inode:
  	//ext3_journal_release_buffer(handle, iloc.bh);
  	brelse(iloc.bh);
  exit_dindj:
  	//ext3_journal_release_buffer(handle, dind);
  exit_primary:
  	//ext3_journal_release_buffer(handle, *primary);
  exit_sbh:
  	//ext3_journal_release_buffer(handle, *primary);
  exit_dind:
  	brelse(dind);
  exit_bh:
  	brelse(*primary);
  
  	ext3_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,
  			      struct ext3_new_group_data *input)
  {
  	struct super_block *sb = inode->i_sb;
  	int reserved_gdb =le16_to_cpu(EXT3_SB(sb)->s_es->s_reserved_gdt_blocks);
  	struct buffer_head **primary;
  	struct buffer_head *dind;
  	struct ext3_iloc iloc;

  	ext3_fsblk_t blk;

  	__u32 *data, *end;
  	int gdbackups = 0;
  	int res, i;
  	int err;
  
  	primary = kmalloc(reserved_gdb * sizeof(*primary), GFP_KERNEL);
  	if (!primary)
  		return -ENOMEM;
  
  	data = EXT3_I(inode)->i_data + EXT3_DIND_BLOCK;
  	dind = sb_bread(sb, le32_to_cpu(*data));
  	if (!dind) {
  		err = -EIO;
  		goto exit_free;
  	}
  
  	blk = EXT3_SB(sb)->s_sbh->b_blocknr + 1 + EXT3_SB(sb)->s_gdb_count;
  	data = (__u32 *)dind->b_data + EXT3_SB(sb)->s_gdb_count;
  	end = (__u32 *)dind->b_data + EXT3_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) {
  			ext3_warning(sb, __FUNCTION__,

  				     "reserved block "E3FSBLK
  				     " not at offset %ld",

  				     blk, (long)(data - (__u32 *)dind->b_data));
  			err = -EINVAL;
  			goto exit_bh;
  		}
  		primary[res] = sb_bread(sb, blk);
  		if (!primary[res]) {
  			err = -EIO;
  			goto exit_bh;
  		}
  		if ((gdbackups = verify_reserved_gdb(sb, primary[res])) < 0) {
  			brelse(primary[res]);
  			err = gdbackups;
  			goto exit_bh;
  		}
  		if (++data >= end)
  			data = (__u32 *)dind->b_data;
  	}
  
  	for (i = 0; i < reserved_gdb; i++) {
  		if ((err = ext3_journal_get_write_access(handle, primary[i]))) {
  			/*
  			int j;
  			for (j = 0; j < i; j++)
  				ext3_journal_release_buffer(handle, primary[j]);
  			 */
  			goto exit_bh;
  		}
  	}
  
  	if ((err = ext3_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 = input->group * EXT3_BLOCKS_PER_GROUP(sb);
  	for (i = 0; i < reserved_gdb; i++) {
  		int err2;
  		data = (__u32 *)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 = ext3_journal_dirty_metadata(handle, primary[i]);
  		if (!err)
  			err = err2;
  	}
  	inode->i_blocks += reserved_gdb * sb->s_blocksize >> 9;
  	ext3_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 ext3 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 lock_super() 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 ext3_sb_info *sbi = EXT3_SB(sb);
  	const unsigned long last = sbi->s_groups_count;
  	const int bpg = EXT3_BLOCKS_PER_GROUP(sb);
  	unsigned three = 1;
  	unsigned five = 5;
  	unsigned seven = 7;
  	unsigned group;
  	int rest = sb->s_blocksize - size;
  	handle_t *handle;
  	int err = 0, err2;
  
  	handle = ext3_journal_start_sb(sb, EXT3_MAX_TRANS_DATA);
  	if (IS_ERR(handle)) {
  		group = 1;
  		err = PTR_ERR(handle);
  		goto exit_err;
  	}
  
  	while ((group = ext3_list_backups(sb, &three, &five, &seven)) < last) {
  		struct buffer_head *bh;
  
  		/* Out of journal space, and can't get more - abort - so sad */
  		if (handle->h_buffer_credits == 0 &&
  		    ext3_journal_extend(handle, EXT3_MAX_TRANS_DATA) &&
  		    (err = ext3_journal_restart(handle, EXT3_MAX_TRANS_DATA)))
  			break;
  
  		bh = sb_getblk(sb, group * bpg + blk_off);

  		if (!bh) {
  			err = -EIO;
  			break;
  		}

  		ext3_debug("update metadata backup %#04lx
  ",
  			  (unsigned long)bh->b_blocknr);

  		if ((err = ext3_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);
  		ext3_journal_dirty_metadata(handle, bh);
  		brelse(bh);
  	}
  	if ((err2 = ext3_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) {
  		ext3_warning(sb, __FUNCTION__,
  			     "can't update backup for group %d (err %d), "

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

  		sbi->s_mount_state &= ~EXT3_VALID_FS;
  		sbi->s_es->s_state &= ~cpu_to_le16(EXT3_VALID_FS);
  		mark_buffer_dirty(sbi->s_sbh);
  	}
  }
  
  /* 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 ext3_group_add(struct super_block *sb, struct ext3_new_group_data *input)
  {
  	struct ext3_sb_info *sbi = EXT3_SB(sb);
  	struct ext3_super_block *es = sbi->s_es;
  	int reserved_gdb = ext3_bg_has_super(sb, input->group) ?
  		le16_to_cpu(es->s_reserved_gdt_blocks) : 0;
  	struct buffer_head *primary = NULL;
  	struct ext3_group_desc *gdp;
  	struct inode *inode = NULL;
  	handle_t *handle;
  	int gdb_off, gdb_num;
  	int err, err2;
  
  	gdb_num = input->group / EXT3_DESC_PER_BLOCK(sb);
  	gdb_off = input->group % EXT3_DESC_PER_BLOCK(sb);
  
  	if (gdb_off == 0 && !EXT3_HAS_RO_COMPAT_FEATURE(sb,
  					EXT3_FEATURE_RO_COMPAT_SPARSE_SUPER)) {
  		ext3_warning(sb, __FUNCTION__,

  			     "Can't resize non-sparse filesystem further");

  		return -EPERM;
  	}
  
  	if (reserved_gdb || gdb_off == 0) {
  		if (!EXT3_HAS_COMPAT_FEATURE(sb,
  					     EXT3_FEATURE_COMPAT_RESIZE_INODE)){
  			ext3_warning(sb, __FUNCTION__,

  				     "No reserved GDT blocks, can't resize");

  			return -EPERM;
  		}
  		inode = iget(sb, EXT3_RESIZE_INO);
  		if (!inode || is_bad_inode(inode)) {
  			ext3_warning(sb, __FUNCTION__,

  				     "Error opening resize inode");

  			iput(inode);
  			return -ENOENT;
  		}
  	}
  
  	if ((err = verify_group_input(sb, input)))
  		goto exit_put;
  
  	if ((err = setup_new_group_blocks(sb, input)))
  		goto exit_put;
  
  	/*
  	 * We will always be modifying at least the superblock and a 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.
  	 */
  	handle = ext3_journal_start_sb(sb,
  				       ext3_bg_has_super(sb, input->group) ?
  				       3 + reserved_gdb : 4);
  	if (IS_ERR(handle)) {
  		err = PTR_ERR(handle);
  		goto exit_put;
  	}
  
  	lock_super(sb);

  	if (input->group != sbi->s_groups_count) {

  		ext3_warning(sb, __FUNCTION__,

  			     "multiple resizers run on filesystem!");

  		err = -EBUSY;

  		goto exit_journal;
  	}
  
  	if ((err = ext3_journal_get_write_access(handle, sbi->s_sbh)))
  		goto exit_journal;
  
  	/*
  	 * 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) {
  		primary = sbi->s_group_desc[gdb_num];
  		if ((err = ext3_journal_get_write_access(handle, primary)))
  			goto exit_journal;
  
  		if (reserved_gdb && ext3_bg_num_gdb(sb, input->group) &&
  		    (err = reserve_backup_gdb(handle, inode, input)))
  			goto exit_journal;
  	} else if ((err = add_new_gdb(handle, inode, input, &primary)))
  		goto exit_journal;
  
  	/*
  	 * OK, now we've set up the new group.  Time to make it active.
  	 *
  	 * Current kernels don't lock all allocations via lock_super(),
  	 * so we have to be safe wrt. concurrent accesses the group
  	 * data.  So we need to be careful to set all of the relevant
  	 * group descriptor data etc. *before* we enable the group.
  	 *

  	 * The key field here is sbi->s_groups_count: as long as

  	 * that retains its old value, nobody is going to access the new
  	 * group.
  	 *
  	 * So first we update all the descriptor metadata for the new
  	 * group; then we update the total disk blocks count; then we
  	 * update the groups count to enable the group; then finally we
  	 * update the free space counts so that the system can start
  	 * using the new disk blocks.
  	 */
  
  	/* Update group descriptor block for new group */
  	gdp = (struct ext3_group_desc *)primary->b_data + gdb_off;
  
  	gdp->bg_block_bitmap = cpu_to_le32(input->block_bitmap);
  	gdp->bg_inode_bitmap = cpu_to_le32(input->inode_bitmap);
  	gdp->bg_inode_table = cpu_to_le32(input->inode_table);
  	gdp->bg_free_blocks_count = cpu_to_le16(input->free_blocks_count);
  	gdp->bg_free_inodes_count = cpu_to_le16(EXT3_INODES_PER_GROUP(sb));
  
  	/*
  	 * 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.
  	 */
  	es->s_blocks_count = cpu_to_le32(le32_to_cpu(es->s_blocks_count) +
  		input->blocks_count);
  	es->s_inodes_count = cpu_to_le32(le32_to_cpu(es->s_inodes_count) +
  		EXT3_INODES_PER_GROUP(sb));
  
  	/*
  	 * We need to protect s_groups_count against other CPUs seeing
  	 * inconsistent state in the superblock.
  	 *
  	 * The precise rules we use are:
  	 *
  	 * * Writers of s_groups_count *must* hold lock_super
  	 * AND
  	 * * Writers must perform a smp_wmb() after updating all dependent
  	 *   data and before modifying the groups count
  	 *
  	 * * Readers must hold lock_super() over the access
  	 * OR
  	 * * 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++;

  
  	ext3_journal_dirty_metadata(handle, primary);
  
  	/* Update the reserved block counts only once the new group is
  	 * active. */
  	es->s_r_blocks_count = cpu_to_le32(le32_to_cpu(es->s_r_blocks_count) +
  		input->reserved_blocks);
  
  	/* Update the free space counts */
  	percpu_counter_mod(&sbi->s_freeblocks_counter,
  			   input->free_blocks_count);
  	percpu_counter_mod(&sbi->s_freeinodes_counter,
  			   EXT3_INODES_PER_GROUP(sb));

  	ext3_journal_dirty_metadata(handle, sbi->s_sbh);

  	sb->s_dirt = 1;
  
  exit_journal:
  	unlock_super(sb);
  	if ((err2 = ext3_journal_stop(handle)) && !err)
  		err = err2;
  	if (!err) {
  		update_backups(sb, sbi->s_sbh->b_blocknr, (char *)es,
  			       sizeof(struct ext3_super_block));
  		update_backups(sb, primary->b_blocknr, primary->b_data,
  			       primary->b_size);
  	}
  exit_put:
  	iput(inode);
  	return err;
  } /* ext3_group_add */
  
  /* 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 ext3_group_add()
   * allow the "remount" trick to work for arbitrary resizing, assuming enough
   * GDT blocks are reserved to grow to the desired size.
   */
  int ext3_group_extend(struct super_block *sb, struct ext3_super_block *es,

  		      ext3_fsblk_t n_blocks_count)

  {

  	ext3_fsblk_t o_blocks_count;

  	unsigned long o_groups_count;

  	ext3_grpblk_t last;
  	ext3_grpblk_t add;

  	struct buffer_head * bh;
  	handle_t *handle;

  	int err;
  	unsigned long freed_blocks;

  
  	/* We don't need to worry about locking wrt other resizers just
  	 * yet: we're going to revalidate es->s_blocks_count after
  	 * taking lock_super() below. */
  	o_blocks_count = le32_to_cpu(es->s_blocks_count);
  	o_groups_count = EXT3_SB(sb)->s_groups_count;
  
  	if (test_opt(sb, DEBUG))

  		printk(KERN_DEBUG "EXT3-fs: extending last group from "E3FSBLK" uto "E3FSBLK" 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 "EXT3-fs: filesystem on %s:"
  			" too large to resize to %lu blocks safely
  ",
  			sb->s_id, n_blocks_count);
  		if (sizeof(sector_t) < 8)
  			ext3_warning(sb, __FUNCTION__,
  			"CONFIG_LBD not enabled
  ");
  		return -EINVAL;
  	}

  	if (n_blocks_count < o_blocks_count) {
  		ext3_warning(sb, __FUNCTION__,
  			     "can't shrink FS - resize aborted");
  		return -EBUSY;
  	}
  
  	/* Handle the remaining blocks in the last group only. */
  	last = (o_blocks_count - le32_to_cpu(es->s_first_data_block)) %
  		EXT3_BLOCKS_PER_GROUP(sb);
  
  	if (last == 0) {
  		ext3_warning(sb, __FUNCTION__,

  			     "need to use ext2online to resize further");

  		return -EPERM;
  	}
  
  	add = EXT3_BLOCKS_PER_GROUP(sb) - last;
  
  	if (o_blocks_count + add > n_blocks_count)
  		add = n_blocks_count - o_blocks_count;
  
  	if (o_blocks_count + add < n_blocks_count)
  		ext3_warning(sb, __FUNCTION__,

  			     "will only finish group ("E3FSBLK
  			     " 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) {
  		ext3_warning(sb, __FUNCTION__,
  			     "can't read last block, resize aborted");
  		return -ENOSPC;
  	}
  	brelse(bh);
  
  	/* We will update the superblock, one block bitmap, and
  	 * one group descriptor via ext3_free_blocks().
  	 */
  	handle = ext3_journal_start_sb(sb, 3);
  	if (IS_ERR(handle)) {
  		err = PTR_ERR(handle);
  		ext3_warning(sb, __FUNCTION__, "error %d on journal start",err);
  		goto exit_put;
  	}
  
  	lock_super(sb);
  	if (o_blocks_count != le32_to_cpu(es->s_blocks_count)) {
  		ext3_warning(sb, __FUNCTION__,

  			     "multiple resizers run on filesystem!");

  		unlock_super(sb);

  		err = -EBUSY;
  		goto exit_put;
  	}
  
  	if ((err = ext3_journal_get_write_access(handle,
  						 EXT3_SB(sb)->s_sbh))) {
  		ext3_warning(sb, __FUNCTION__,
  			     "error %d on journal write access", err);
  		unlock_super(sb);
  		ext3_journal_stop(handle);
  		goto exit_put;
  	}
  	es->s_blocks_count = cpu_to_le32(o_blocks_count + add);
  	ext3_journal_dirty_metadata(handle, EXT3_SB(sb)->s_sbh);
  	sb->s_dirt = 1;
  	unlock_super(sb);

  	ext3_debug("freeing blocks %lu through "E3FSBLK"
  ", o_blocks_count,

  		   o_blocks_count + add);
  	ext3_free_blocks_sb(handle, sb, o_blocks_count, add, &freed_blocks);

  	ext3_debug("freed blocks "E3FSBLK" through "E3FSBLK"
  ", o_blocks_count,

  		   o_blocks_count + add);
  	if ((err = ext3_journal_stop(handle)))
  		goto exit_put;
  	if (test_opt(sb, DEBUG))
  		printk(KERN_DEBUG "EXT3-fs: extended group to %u blocks
  ",
  		       le32_to_cpu(es->s_blocks_count));
  	update_backups(sb, EXT3_SB(sb)->s_sbh->b_blocknr, (char *)es,
  		       sizeof(struct ext3_super_block));
  exit_put:
  	return err;
  } /* ext3_group_extend */