fs/ext2/ialloc.c - kernel/msm - Gitiles

 /*
  *  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 = NULL;
 	unsigned long block_group;
 	unsigned long bit;
 	struct ext2_super_block * es;

 	ino = inode->i_ino;
 	ext2_debug ("freeing inode %lu\n", ino);

 	/*
 	 * Note: we must free any quota before locking the superblock,
 	 * as writing the quota to disk may need the lock as well.
 	 */
 	if (!is_bad_inode(inode)) {
 		/* 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);

 	/* Do this BEFORE marking the inode not in use or returning an error */
 	clear_inode (inode);

 	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);
 		goto error_return;
 	}
 	block_group = (ino - 1) / EXT2_INODES_PER_GROUP(sb);
 	bit = (ino - 1) % EXT2_INODES_PER_GROUP(sb);
 	brelse(bitmap_bh);
 	bitmap_bh = read_inode_bitmap(sb, block_group);
 	if (!bitmap_bh)
 		goto error_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);
 error_return:
 	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, int mode)
 {
 	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);
 	inode->i_uid = current_fsuid();
 	if (test_opt (sb, GRPID))
 		inode->i_gid = dir->i_gid;
 	else if (dir->i_mode & S_ISGID) {
 		inode->i_gid = dir->i_gid;
 		if (S_ISDIR(mode))
 			mode |= S_ISGID;
 	} else
 		inode->i_gid = current_fsgid();
 	inode->i_mode = 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_I(dir)->i_flags & ~EXT2_BTREE_FL;
 	if (S_ISLNK(mode))
 		ei->i_flags &= ~(EXT2_IMMUTABLE_FL|EXT2_APPEND_FL);
 	/* dirsync is only applied to directories */
 	if (!S_ISDIR(mode))
 		ei->i_flags &= ~EXT2_DIRSYNC_FL;
 	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);
 	insert_inode_hash(inode);

 	if (DQUOT_ALLOC_INODE(inode)) {
 		err = -EDQUOT;
 		goto fail_drop;
 	}

 	err = ext2_init_acl(inode, dir);
 	if (err)
 		goto fail_free_drop;

 	err = ext2_init_security(inode,dir);
 	if (err)
 		goto fail_free_drop;

 	mark_inode_dirty(inode);
 	ext2_debug("allocating inode %lu\n", 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;
 	inode->i_nlink = 0;
 	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\n",
 			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\n",
 		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;
 }
	/*
	* 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 = NULL;
	unsigned long block_group;
	unsigned long bit;
	struct ext2_super_block * es;

	ino = inode->i_ino;
	ext2_debug ("freeing inode %lu\n", ino);

	/*
	* Note: we must free any quota before locking the superblock,
	* as writing the quota to disk may need the lock as well.
	*/
	if (!is_bad_inode(inode)) {
	/* 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);

	/* Do this BEFORE marking the inode not in use or returning an error */
	clear_inode (inode);

	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);
	goto error_return;
	}
	block_group = (ino - 1) / EXT2_INODES_PER_GROUP(sb);
	bit = (ino - 1) % EXT2_INODES_PER_GROUP(sb);
	brelse(bitmap_bh);
	bitmap_bh = read_inode_bitmap(sb, block_group);
	if (!bitmap_bh)
	goto error_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);
	error_return:
	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, int mode)
	{
	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);
	inode->i_uid = current_fsuid();
	if (test_opt (sb, GRPID))
	inode->i_gid = dir->i_gid;
	else if (dir->i_mode & S_ISGID) {
	inode->i_gid = dir->i_gid;
	if (S_ISDIR(mode))
	mode \|= S_ISGID;
	} else
	inode->i_gid = current_fsgid();
	inode->i_mode = 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_I(dir)->i_flags & ~EXT2_BTREE_FL;
	if (S_ISLNK(mode))
	ei->i_flags &= ~(EXT2_IMMUTABLE_FL\|EXT2_APPEND_FL);
	/* dirsync is only applied to directories */
	if (!S_ISDIR(mode))
	ei->i_flags &= ~EXT2_DIRSYNC_FL;
	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);
	insert_inode_hash(inode);

	if (DQUOT_ALLOC_INODE(inode)) {
	err = -EDQUOT;
	goto fail_drop;
	}

	err = ext2_init_acl(inode, dir);
	if (err)
	goto fail_free_drop;

	err = ext2_init_security(inode,dir);
	if (err)
	goto fail_free_drop;

	mark_inode_dirty(inode);
	ext2_debug("allocating inode %lu\n", 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;
	inode->i_nlink = 0;
	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\n",
	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\n",
	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;
	}