/*
   *  linux/fs/ext2/ialloc.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)
   *
   *  BSD ufs-inspired inode and directory allocation by 
   *  Stephen Tweedie (sct@dcs.ed.ac.uk), 1993
   *  Big-endian to little-endian byte-swapping/bitmaps by
   *        David S. Miller (davem@caip.rutgers.edu), 1995
   */

  #include <linux/quotaops.h>
  #include <linux/sched.h>
  #include <linux/backing-dev.h>
  #include <linux/buffer_head.h>
  #include <linux/random.h>
  #include "ext2.h"
  #include "xattr.h"
  #include "acl.h"
  
  /*
   * ialloc.c contains the inodes allocation and deallocation routines
   */
  
  /*
   * The free inodes 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.
   */
  
  
  /*
   * Read the inode allocation bitmap for a given block_group, reading
   * into the specified slot in the superblock's bitmap cache.
   *
   * Return buffer_head of bitmap on success or NULL.
   */
  static struct buffer_head *
  read_inode_bitmap(struct super_block * sb, unsigned long block_group)
  {
  	struct ext2_group_desc *desc;
  	struct buffer_head *bh = NULL;
  
  	desc = ext2_get_group_desc(sb, block_group, NULL);
  	if (!desc)
  		goto error_out;
  
  	bh = sb_bread(sb, le32_to_cpu(desc->bg_inode_bitmap));
  	if (!bh)
  		ext2_error(sb, "read_inode_bitmap",
  			    "Cannot read inode bitmap - "
  			    "block_group = %lu, inode_bitmap = %u",
  			    block_group, le32_to_cpu(desc->bg_inode_bitmap));
  error_out:
  	return bh;
  }
  
  static void ext2_release_inode(struct super_block *sb, int group, int dir)
  {
  	struct ext2_group_desc * desc;
  	struct buffer_head *bh;
  
  	desc = ext2_get_group_desc(sb, group, &bh);
  	if (!desc) {
  		ext2_error(sb, "ext2_release_inode",
  			"can't get descriptor for group %d", group);
  		return;
  	}
  
  	spin_lock(sb_bgl_lock(EXT2_SB(sb), group));

  	le16_add_cpu(&desc->bg_free_inodes_count, 1);

  	if (dir)

  		le16_add_cpu(&desc->bg_used_dirs_count, -1);

  	spin_unlock(sb_bgl_lock(EXT2_SB(sb), group));
  	if (dir)
  		percpu_counter_dec(&EXT2_SB(sb)->s_dirs_counter);
  	sb->s_dirt = 1;
  	mark_buffer_dirty(bh);
  }
  
  /*
   * NOTE! When we get the inode, we're the only people
   * that have access to it, and as such there are no
   * race conditions we have to worry about. The inode
   * is not on the hash-lists, and it cannot be reached
   * through the filesystem because the directory entry
   * has been deleted earlier.
   *
   * HOWEVER: we must make sure that we get no aliases,
   * which means that we have to call "clear_inode()"
   * _before_ we mark the inode not in use in the inode
   * bitmaps. Otherwise a newly created file might use
   * the same inode number (not actually the same pointer
   * though), and then we'd have two inodes sharing the
   * same inode number and space on the harddisk.
   */
  void ext2_free_inode (struct inode * inode)
  {
  	struct super_block * sb = inode->i_sb;
  	int is_directory;
  	unsigned long ino;

  	struct buffer_head *bitmap_bh;

  	unsigned long block_group;
  	unsigned long bit;
  	struct ext2_super_block * es;
  
  	ino = inode->i_ino;
  	ext2_debug ("freeing inode %lu
  ", ino);
  
  	/*
  	 * Note: we must free any quota before locking the superblock,
  	 * as writing the quota to disk may need the lock as well.
  	 */

  	/* Quota is already initialized in iput() */
  	ext2_xattr_delete_inode(inode);
  	dquot_free_inode(inode);
  	dquot_drop(inode);

  
  	es = EXT2_SB(sb)->s_es;
  	is_directory = S_ISDIR(inode->i_mode);

  	if (ino < EXT2_FIRST_INO(sb) ||
  	    ino > le32_to_cpu(es->s_inodes_count)) {
  		ext2_error (sb, "ext2_free_inode",
  			    "reserved or nonexistent inode %lu", ino);

  		return;

  	}
  	block_group = (ino - 1) / EXT2_INODES_PER_GROUP(sb);
  	bit = (ino - 1) % EXT2_INODES_PER_GROUP(sb);

  	bitmap_bh = read_inode_bitmap(sb, block_group);
  	if (!bitmap_bh)

  		return;

  
  	/* Ok, now we can actually update the inode bitmaps.. */
  	if (!ext2_clear_bit_atomic(sb_bgl_lock(EXT2_SB(sb), block_group),
  				bit, (void *) bitmap_bh->b_data))
  		ext2_error (sb, "ext2_free_inode",
  			      "bit already cleared for inode %lu", ino);
  	else
  		ext2_release_inode(sb, block_group, is_directory);
  	mark_buffer_dirty(bitmap_bh);
  	if (sb->s_flags & MS_SYNCHRONOUS)
  		sync_dirty_buffer(bitmap_bh);

  	brelse(bitmap_bh);
  }
  
  /*
   * We perform asynchronous prereading of the new inode's inode block when
   * we create the inode, in the expectation that the inode will be written
   * back soon.  There are two reasons:
   *
   * - When creating a large number of files, the async prereads will be
   *   nicely merged into large reads
   * - When writing out a large number of inodes, we don't need to keep on
   *   stalling the writes while we read the inode block.
   *
   * FIXME: ext2_get_group_desc() needs to be simplified.
   */
  static void ext2_preread_inode(struct inode *inode)
  {
  	unsigned long block_group;
  	unsigned long offset;
  	unsigned long block;

  	struct ext2_group_desc * gdp;
  	struct backing_dev_info *bdi;
  
  	bdi = inode->i_mapping->backing_dev_info;
  	if (bdi_read_congested(bdi))
  		return;
  	if (bdi_write_congested(bdi))
  		return;
  
  	block_group = (inode->i_ino - 1) / EXT2_INODES_PER_GROUP(inode->i_sb);

  	gdp = ext2_get_group_desc(inode->i_sb, block_group, NULL);

  	if (gdp == NULL)
  		return;
  
  	/*
  	 * Figure out the offset within the block group inode table
  	 */
  	offset = ((inode->i_ino - 1) % EXT2_INODES_PER_GROUP(inode->i_sb)) *
  				EXT2_INODE_SIZE(inode->i_sb);
  	block = le32_to_cpu(gdp->bg_inode_table) +
  				(offset >> EXT2_BLOCK_SIZE_BITS(inode->i_sb));
  	sb_breadahead(inode->i_sb, block);
  }
  
  /*
   * There are two policies for allocating an inode.  If the new inode is
   * a directory, then a forward search is made for a block group with both
   * free space and a low directory-to-inode ratio; if that fails, then of
   * the groups with above-average free space, that group with the fewest
   * directories already is chosen.
   *
   * For other inodes, search forward from the parent directory\'s block
   * group to find a free inode.
   */
  static int find_group_dir(struct super_block *sb, struct inode *parent)
  {
  	int ngroups = EXT2_SB(sb)->s_groups_count;
  	int avefreei = ext2_count_free_inodes(sb) / ngroups;
  	struct ext2_group_desc *desc, *best_desc = NULL;

  	int group, best_group = -1;
  
  	for (group = 0; group < ngroups; group++) {

  		desc = ext2_get_group_desc (sb, group, NULL);

  		if (!desc || !desc->bg_free_inodes_count)
  			continue;
  		if (le16_to_cpu(desc->bg_free_inodes_count) < avefreei)
  			continue;
  		if (!best_desc || 
  		    (le16_to_cpu(desc->bg_free_blocks_count) >
  		     le16_to_cpu(best_desc->bg_free_blocks_count))) {
  			best_group = group;
  			best_desc = desc;

  		}
  	}
  	if (!best_desc)
  		return -1;
  
  	return best_group;
  }
  
  /* 
   * Orlov's allocator for directories. 
   * 
   * We always try to spread first-level directories.
   *
   * If there are blockgroups with both free inodes and free blocks counts 
   * not worse than average we return one with smallest directory count. 
   * Otherwise we simply return a random group. 
   * 
   * For the rest rules look so: 
   * 
   * It's OK to put directory into a group unless 
   * it has too many directories already (max_dirs) or 
   * it has too few free inodes left (min_inodes) or 
   * it has too few free blocks left (min_blocks) or 
   * it's already running too large debt (max_debt). 

   * Parent's group is preferred, if it doesn't satisfy these 

   * conditions we search cyclically through the rest. If none 
   * of the groups look good we just look for a group with more 
   * free inodes than average (starting at parent's group). 
   * 
   * Debt is incremented each time we allocate a directory and decremented 
   * when we allocate an inode, within 0--255. 
   */ 
  
  #define INODE_COST 64
  #define BLOCK_COST 256
  
  static int find_group_orlov(struct super_block *sb, struct inode *parent)
  {
  	int parent_group = EXT2_I(parent)->i_block_group;
  	struct ext2_sb_info *sbi = EXT2_SB(sb);
  	struct ext2_super_block *es = sbi->s_es;
  	int ngroups = sbi->s_groups_count;
  	int inodes_per_group = EXT2_INODES_PER_GROUP(sb);
  	int freei;
  	int avefreei;
  	int free_blocks;
  	int avefreeb;
  	int blocks_per_dir;
  	int ndirs;
  	int max_debt, max_dirs, min_blocks, min_inodes;
  	int group = -1, i;
  	struct ext2_group_desc *desc;

  
  	freei = percpu_counter_read_positive(&sbi->s_freeinodes_counter);
  	avefreei = freei / ngroups;
  	free_blocks = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
  	avefreeb = free_blocks / ngroups;
  	ndirs = percpu_counter_read_positive(&sbi->s_dirs_counter);
  
  	if ((parent == sb->s_root->d_inode) ||
  	    (EXT2_I(parent)->i_flags & EXT2_TOPDIR_FL)) {
  		struct ext2_group_desc *best_desc = NULL;

  		int best_ndir = inodes_per_group;
  		int best_group = -1;
  
  		get_random_bytes(&group, sizeof(group));
  		parent_group = (unsigned)group % ngroups;
  		for (i = 0; i < ngroups; i++) {
  			group = (parent_group + i) % ngroups;

  			desc = ext2_get_group_desc (sb, group, NULL);

  			if (!desc || !desc->bg_free_inodes_count)
  				continue;
  			if (le16_to_cpu(desc->bg_used_dirs_count) >= best_ndir)
  				continue;
  			if (le16_to_cpu(desc->bg_free_inodes_count) < avefreei)
  				continue;
  			if (le16_to_cpu(desc->bg_free_blocks_count) < avefreeb)
  				continue;
  			best_group = group;
  			best_ndir = le16_to_cpu(desc->bg_used_dirs_count);
  			best_desc = desc;

  		}
  		if (best_group >= 0) {
  			desc = best_desc;

  			group = best_group;
  			goto found;
  		}
  		goto fallback;
  	}
  
  	if (ndirs == 0)
  		ndirs = 1;	/* percpu_counters are approximate... */
  
  	blocks_per_dir = (le32_to_cpu(es->s_blocks_count)-free_blocks) / ndirs;
  
  	max_dirs = ndirs / ngroups + inodes_per_group / 16;
  	min_inodes = avefreei - inodes_per_group / 4;
  	min_blocks = avefreeb - EXT2_BLOCKS_PER_GROUP(sb) / 4;
  
  	max_debt = EXT2_BLOCKS_PER_GROUP(sb) / max(blocks_per_dir, BLOCK_COST);
  	if (max_debt * INODE_COST > inodes_per_group)
  		max_debt = inodes_per_group / INODE_COST;
  	if (max_debt > 255)
  		max_debt = 255;
  	if (max_debt == 0)
  		max_debt = 1;
  
  	for (i = 0; i < ngroups; i++) {
  		group = (parent_group + i) % ngroups;

  		desc = ext2_get_group_desc (sb, group, NULL);

  		if (!desc || !desc->bg_free_inodes_count)
  			continue;
  		if (sbi->s_debts[group] >= max_debt)
  			continue;
  		if (le16_to_cpu(desc->bg_used_dirs_count) >= max_dirs)
  			continue;
  		if (le16_to_cpu(desc->bg_free_inodes_count) < min_inodes)
  			continue;
  		if (le16_to_cpu(desc->bg_free_blocks_count) < min_blocks)
  			continue;
  		goto found;
  	}
  
  fallback:
  	for (i = 0; i < ngroups; i++) {
  		group = (parent_group + i) % ngroups;

  		desc = ext2_get_group_desc (sb, group, NULL);

  		if (!desc || !desc->bg_free_inodes_count)
  			continue;
  		if (le16_to_cpu(desc->bg_free_inodes_count) >= avefreei)
  			goto found;
  	}
  
  	if (avefreei) {
  		/*
  		 * The free-inodes counter is approximate, and for really small
  		 * filesystems the above test can fail to find any blockgroups
  		 */
  		avefreei = 0;
  		goto fallback;
  	}
  
  	return -1;
  
  found:
  	return group;
  }
  
  static int find_group_other(struct super_block *sb, struct inode *parent)
  {
  	int parent_group = EXT2_I(parent)->i_block_group;
  	int ngroups = EXT2_SB(sb)->s_groups_count;
  	struct ext2_group_desc *desc;

  	int group, i;
  
  	/*
  	 * Try to place the inode in its parent directory
  	 */
  	group = parent_group;

  	desc = ext2_get_group_desc (sb, group, NULL);

  	if (desc && le16_to_cpu(desc->bg_free_inodes_count) &&
  			le16_to_cpu(desc->bg_free_blocks_count))
  		goto found;
  
  	/*
  	 * We're going to place this inode in a different blockgroup from its
  	 * parent.  We want to cause files in a common directory to all land in
  	 * the same blockgroup.  But we want files which are in a different
  	 * directory which shares a blockgroup with our parent to land in a
  	 * different blockgroup.
  	 *
  	 * So add our directory's i_ino into the starting point for the hash.
  	 */
  	group = (group + parent->i_ino) % ngroups;
  
  	/*
  	 * Use a quadratic hash to find a group with a free inode and some
  	 * free blocks.
  	 */
  	for (i = 1; i < ngroups; i <<= 1) {
  		group += i;
  		if (group >= ngroups)
  			group -= ngroups;

  		desc = ext2_get_group_desc (sb, group, NULL);

  		if (desc && le16_to_cpu(desc->bg_free_inodes_count) &&
  				le16_to_cpu(desc->bg_free_blocks_count))
  			goto found;
  	}
  
  	/*
  	 * That failed: try linear search for a free inode, even if that group
  	 * has no free blocks.
  	 */
  	group = parent_group;
  	for (i = 0; i < ngroups; i++) {
  		if (++group >= ngroups)
  			group = 0;

  		desc = ext2_get_group_desc (sb, group, NULL);

  		if (desc && le16_to_cpu(desc->bg_free_inodes_count))
  			goto found;
  	}
  
  	return -1;
  
  found:
  	return group;
  }

  struct inode *ext2_new_inode(struct inode *dir, umode_t mode,

  			     const struct qstr *qstr)

  {
  	struct super_block *sb;
  	struct buffer_head *bitmap_bh = NULL;
  	struct buffer_head *bh2;
  	int group, i;
  	ino_t ino = 0;
  	struct inode * inode;
  	struct ext2_group_desc *gdp;
  	struct ext2_super_block *es;
  	struct ext2_inode_info *ei;
  	struct ext2_sb_info *sbi;
  	int err;
  
  	sb = dir->i_sb;
  	inode = new_inode(sb);
  	if (!inode)
  		return ERR_PTR(-ENOMEM);
  
  	ei = EXT2_I(inode);
  	sbi = EXT2_SB(sb);
  	es = sbi->s_es;
  	if (S_ISDIR(mode)) {
  		if (test_opt(sb, OLDALLOC))
  			group = find_group_dir(sb, dir);
  		else
  			group = find_group_orlov(sb, dir);
  	} else 
  		group = find_group_other(sb, dir);
  
  	if (group == -1) {
  		err = -ENOSPC;
  		goto fail;
  	}
  
  	for (i = 0; i < sbi->s_groups_count; i++) {
  		gdp = ext2_get_group_desc(sb, group, &bh2);
  		brelse(bitmap_bh);
  		bitmap_bh = read_inode_bitmap(sb, group);
  		if (!bitmap_bh) {
  			err = -EIO;
  			goto fail;
  		}
  		ino = 0;
  
  repeat_in_this_group:
  		ino = ext2_find_next_zero_bit((unsigned long *)bitmap_bh->b_data,
  					      EXT2_INODES_PER_GROUP(sb), ino);
  		if (ino >= EXT2_INODES_PER_GROUP(sb)) {
  			/*
  			 * Rare race: find_group_xx() decided that there were
  			 * free inodes in this group, but by the time we tried
  			 * to allocate one, they're all gone.  This can also
  			 * occur because the counters which find_group_orlov()
  			 * uses are approximate.  So just go and search the
  			 * next block group.
  			 */
  			if (++group == sbi->s_groups_count)
  				group = 0;
  			continue;
  		}
  		if (ext2_set_bit_atomic(sb_bgl_lock(sbi, group),
  						ino, bitmap_bh->b_data)) {
  			/* we lost this inode */
  			if (++ino >= EXT2_INODES_PER_GROUP(sb)) {
  				/* this group is exhausted, try next group */
  				if (++group == sbi->s_groups_count)
  					group = 0;
  				continue;
  			}
  			/* try to find free inode in the same group */
  			goto repeat_in_this_group;
  		}
  		goto got;
  	}
  
  	/*
  	 * Scanned all blockgroups.
  	 */
  	err = -ENOSPC;
  	goto fail;
  got:
  	mark_buffer_dirty(bitmap_bh);
  	if (sb->s_flags & MS_SYNCHRONOUS)
  		sync_dirty_buffer(bitmap_bh);
  	brelse(bitmap_bh);
  
  	ino += group * EXT2_INODES_PER_GROUP(sb) + 1;
  	if (ino < EXT2_FIRST_INO(sb) || ino > le32_to_cpu(es->s_inodes_count)) {
  		ext2_error (sb, "ext2_new_inode",
  			    "reserved inode or inode > inodes count - "
  			    "block_group = %d,inode=%lu", group,
  			    (unsigned long) ino);
  		err = -EIO;
  		goto fail;
  	}

  	percpu_counter_add(&sbi->s_freeinodes_counter, -1);

  	if (S_ISDIR(mode))
  		percpu_counter_inc(&sbi->s_dirs_counter);
  
  	spin_lock(sb_bgl_lock(sbi, group));

  	le16_add_cpu(&gdp->bg_free_inodes_count, -1);

  	if (S_ISDIR(mode)) {
  		if (sbi->s_debts[group] < 255)
  			sbi->s_debts[group]++;

  		le16_add_cpu(&gdp->bg_used_dirs_count, 1);

  	} else {
  		if (sbi->s_debts[group])
  			sbi->s_debts[group]--;
  	}
  	spin_unlock(sb_bgl_lock(sbi, group));
  
  	sb->s_dirt = 1;
  	mark_buffer_dirty(bh2);

  	if (test_opt(sb, GRPID)) {
  		inode->i_mode = mode;
  		inode->i_uid = current_fsuid();

  		inode->i_gid = dir->i_gid;

  	} else

  		inode_init_owner(inode, dir, mode);

  
  	inode->i_ino = ino;

  	inode->i_blocks = 0;
  	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME_SEC;
  	memset(ei->i_data, 0, sizeof(ei->i_data));

  	ei->i_flags =
  		ext2_mask_flags(mode, EXT2_I(dir)->i_flags & EXT2_FL_INHERITED);

  	ei->i_faddr = 0;
  	ei->i_frag_no = 0;
  	ei->i_frag_size = 0;
  	ei->i_file_acl = 0;
  	ei->i_dir_acl = 0;
  	ei->i_dtime = 0;

  	ei->i_block_alloc_info = NULL;

  	ei->i_block_group = group;

  	ei->i_dir_start_lookup = 0;
  	ei->i_state = EXT2_STATE_NEW;
  	ext2_set_inode_flags(inode);
  	spin_lock(&sbi->s_next_gen_lock);
  	inode->i_generation = sbi->s_next_generation++;
  	spin_unlock(&sbi->s_next_gen_lock);

  	if (insert_inode_locked(inode) < 0) {

  		ext2_error(sb, "ext2_new_inode",
  			   "inode number already in use - inode=%lu",
  			   (unsigned long) ino);
  		err = -EIO;
  		goto fail;

  	}

  	dquot_initialize(inode);

  	err = dquot_alloc_inode(inode);
  	if (err)

  		goto fail_drop;

  	err = ext2_init_acl(inode, dir);

  	if (err)
  		goto fail_free_drop;

  	err = ext2_init_security(inode, dir, qstr);

  	if (err)
  		goto fail_free_drop;

  	mark_inode_dirty(inode);
  	ext2_debug("allocating inode %lu
  ", inode->i_ino);
  	ext2_preread_inode(inode);
  	return inode;

  fail_free_drop:

  	dquot_free_inode(inode);

  
  fail_drop:

  	dquot_drop(inode);

  	inode->i_flags |= S_NOQUOTA;

  	clear_nlink(inode);

  	unlock_new_inode(inode);

  	iput(inode);
  	return ERR_PTR(err);
  
  fail:
  	make_bad_inode(inode);
  	iput(inode);
  	return ERR_PTR(err);
  }
  
  unsigned long ext2_count_free_inodes (struct super_block * sb)
  {
  	struct ext2_group_desc *desc;
  	unsigned long desc_count = 0;
  	int i;	
  
  #ifdef EXT2FS_DEBUG
  	struct ext2_super_block *es;
  	unsigned long bitmap_count = 0;
  	struct buffer_head *bitmap_bh = NULL;

  	es = EXT2_SB(sb)->s_es;
  	for (i = 0; i < EXT2_SB(sb)->s_groups_count; i++) {
  		unsigned x;
  
  		desc = ext2_get_group_desc (sb, i, NULL);
  		if (!desc)
  			continue;
  		desc_count += le16_to_cpu(desc->bg_free_inodes_count);
  		brelse(bitmap_bh);
  		bitmap_bh = read_inode_bitmap(sb, i);
  		if (!bitmap_bh)
  			continue;
  
  		x = ext2_count_free(bitmap_bh, EXT2_INODES_PER_GROUP(sb) / 8);
  		printk("group %d: stored = %d, counted = %u
  ",
  			i, le16_to_cpu(desc->bg_free_inodes_count), x);
  		bitmap_count += x;
  	}
  	brelse(bitmap_bh);
  	printk("ext2_count_free_inodes: stored = %lu, computed = %lu, %lu
  ",
  		percpu_counter_read(&EXT2_SB(sb)->s_freeinodes_counter),
  		desc_count, bitmap_count);

  	return desc_count;
  #else
  	for (i = 0; i < EXT2_SB(sb)->s_groups_count; i++) {
  		desc = ext2_get_group_desc (sb, i, NULL);
  		if (!desc)
  			continue;
  		desc_count += le16_to_cpu(desc->bg_free_inodes_count);
  	}
  	return desc_count;
  #endif
  }
  
  /* Called at mount-time, super-block is locked */
  unsigned long ext2_count_dirs (struct super_block * sb)
  {
  	unsigned long count = 0;
  	int i;
  
  	for (i = 0; i < EXT2_SB(sb)->s_groups_count; i++) {
  		struct ext2_group_desc *gdp = ext2_get_group_desc (sb, i, NULL);
  		if (!gdp)
  			continue;
  		count += le16_to_cpu(gdp->bg_used_dirs_count);
  	}
  	return count;
  }