ialloc.c

讲述linux的初始化过程

		return ERR_PTR(-EPERM);

	sb = dir->i_sb;
	inode = new_inode(sb);
	if (!inode)
		return ERR_PTR(-ENOMEM);

	lock_super (sb);
	es = sb->u.ext2_sb.s_es;
repeat:
	gdp = NULL; i=0;
	
	if (S_ISDIR(mode)) {
		avefreei = le32_to_cpu(es->s_free_inodes_count) /
			sb->u.ext2_sb.s_groups_count;
/* I am not yet convinced that this next bit is necessary.
		i = dir->u.ext2_i.i_block_group;
		for (j = 0; j < sb->u.ext2_sb.s_groups_count; j++) {
			tmp = ext2_get_group_desc (sb, i, &bh2);
			if (tmp &&
			    (le16_to_cpu(tmp->bg_used_dirs_count) << 8) < 
			     le16_to_cpu(tmp->bg_free_inodes_count)) {
				gdp = tmp;
				break;
			}
			else
			i = ++i % sb->u.ext2_sb.s_groups_count;
		}
*/
		if (!gdp) {
			for (j = 0; j < sb->u.ext2_sb.s_groups_count; j++) {
				tmp = ext2_get_group_desc (sb, j, &bh2);
				if (tmp &&
				    le16_to_cpu(tmp->bg_free_inodes_count) &&
				    le16_to_cpu(tmp->bg_free_inodes_count) >= avefreei) {
					if (!gdp || 
					    (le16_to_cpu(tmp->bg_free_blocks_count) >
					     le16_to_cpu(gdp->bg_free_blocks_count))) {
						i = j;
						gdp = tmp;
					}
				}
			}
		}
	}
	else 
	{
		/*
		 * Try to place the inode in its parent directory
		 */
		i = dir->u.ext2_i.i_block_group;
		tmp = ext2_get_group_desc (sb, i, &bh2);
		if (tmp && le16_to_cpu(tmp->bg_free_inodes_count))
			gdp = tmp;
		else
		{
			/*
			 * Use a quadratic hash to find a group with a
			 * free inode
			 */
			for (j = 1; j < sb->u.ext2_sb.s_groups_count; j <<= 1) {
				i += j;
				if (i >= sb->u.ext2_sb.s_groups_count)
					i -= sb->u.ext2_sb.s_groups_count;
				tmp = ext2_get_group_desc (sb, i, &bh2);
				if (tmp &&
				    le16_to_cpu(tmp->bg_free_inodes_count)) {
					gdp = tmp;
					break;
				}
			}
		}
		if (!gdp) {
			/*
			 * That failed: try linear search for a free inode
			 */
			i = dir->u.ext2_i.i_block_group + 1;
			for (j = 2; j < sb->u.ext2_sb.s_groups_count; j++) {
				if (++i >= sb->u.ext2_sb.s_groups_count)
					i = 0;
				tmp = ext2_get_group_desc (sb, i, &bh2);
				if (tmp &&
				    le16_to_cpu(tmp->bg_free_inodes_count)) {
					gdp = tmp;
					break;
				}
			}
		}
	}

	err = -ENOSPC;
	if (!gdp)
		goto fail;

	err = -EIO;
	bitmap_nr = load_inode_bitmap (sb, i);
	if (bitmap_nr < 0)
		goto fail;

	bh = sb->u.ext2_sb.s_inode_bitmap[bitmap_nr];
	if ((j = ext2_find_first_zero_bit ((unsigned long *) bh->b_data,
				      EXT2_INODES_PER_GROUP(sb))) <
	    EXT2_INODES_PER_GROUP(sb)) {
		if (ext2_set_bit (j, bh->b_data)) {
			ext2_error (sb, "ext2_new_inode",
				      "bit already set for inode %d", j);
			goto repeat;
		}
		mark_buffer_dirty(bh);
		if (sb->s_flags & MS_SYNCHRONOUS) {
			ll_rw_block (WRITE, 1, &bh);
			wait_on_buffer (bh);
		}
	} else {
		if (le16_to_cpu(gdp->bg_free_inodes_count) != 0) {
			ext2_error (sb, "ext2_new_inode",
				    "Free inodes count corrupted in group %d",
				    i);
			/* Is it really ENOSPC? */
			err = -ENOSPC;
			if (sb->s_flags & MS_RDONLY)
				goto fail;

			gdp->bg_free_inodes_count = 0;
			mark_buffer_dirty(bh2);
		}
		goto repeat;
	}
	j += i * EXT2_INODES_PER_GROUP(sb) + 1;
	if (j < EXT2_FIRST_INO(sb) || j > le32_to_cpu(es->s_inodes_count)) {
		ext2_error (sb, "ext2_new_inode",
			    "reserved inode or inode > inodes count - "
			    "block_group = %d,inode=%d", i, j);
		err = -EIO;
		goto fail;
	}
	gdp->bg_free_inodes_count =
		cpu_to_le16(le16_to_cpu(gdp->bg_free_inodes_count) - 1);
	if (S_ISDIR(mode))
		gdp->bg_used_dirs_count =
			cpu_to_le16(le16_to_cpu(gdp->bg_used_dirs_count) + 1);
	mark_buffer_dirty(bh2);
	es->s_free_inodes_count =
		cpu_to_le32(le32_to_cpu(es->s_free_inodes_count) - 1);
	mark_buffer_dirty(sb->u.ext2_sb.s_sbh);
	sb->s_dirt = 1;
	inode->i_mode = mode;
	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_ino = j;
	inode->i_blksize = PAGE_SIZE;	/* This is the optimal IO size (for stat), not the fs block size */
	inode->i_blocks = 0;
	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
	inode->u.ext2_i.i_new_inode = 1;
	inode->u.ext2_i.i_flags = dir->u.ext2_i.i_flags;
	if (S_ISLNK(mode))
		inode->u.ext2_i.i_flags &= ~(EXT2_IMMUTABLE_FL | EXT2_APPEND_FL);
	inode->u.ext2_i.i_faddr = 0;
	inode->u.ext2_i.i_frag_no = 0;
	inode->u.ext2_i.i_frag_size = 0;
	inode->u.ext2_i.i_file_acl = 0;
	inode->u.ext2_i.i_dir_acl = 0;
	inode->u.ext2_i.i_dtime = 0;
	inode->u.ext2_i.i_block_group = i;
	if (inode->u.ext2_i.i_flags & EXT2_SYNC_FL)
		inode->i_flags |= S_SYNC;
	insert_inode_hash(inode);
	inode->i_generation = event++;
	mark_inode_dirty(inode);

	unlock_super (sb);
	if(DQUOT_ALLOC_INODE(sb, inode)) {
		sb->dq_op->drop(inode);
		inode->i_nlink = 0;
		iput(inode);
		return ERR_PTR(-EDQUOT);
	}
	ext2_debug ("allocating inode %lu\n", inode->i_ino);
	return inode;

fail:
	unlock_super(sb);
	iput(inode);
	return ERR_PTR(err);
}

unsigned long ext2_count_free_inodes (struct super_block * sb)
{
#ifdef EXT2FS_DEBUG
	struct ext2_super_block * es;
	unsigned long desc_count, bitmap_count, x;
	int bitmap_nr;
	struct ext2_group_desc * gdp;
	int i;

	lock_super (sb);
	es = sb->u.ext2_sb.s_es;
	desc_count = 0;
	bitmap_count = 0;
	gdp = NULL;
	for (i = 0; i < sb->u.ext2_sb.s_groups_count; i++) {
		gdp = ext2_get_group_desc (sb, i, NULL);
		if (!gdp)
			continue;
		desc_count += le16_to_cpu(gdp->bg_free_inodes_count);
		bitmap_nr = load_inode_bitmap (sb, i);
		if (bitmap_nr < 0)
			continue;

		x = ext2_count_free (sb->u.ext2_sb.s_inode_bitmap[bitmap_nr],
				     EXT2_INODES_PER_GROUP(sb) / 8);
		printk ("group %d: stored = %d, counted = %lu\n",
			i, le16_to_cpu(gdp->bg_free_inodes_count), x);
		bitmap_count += x;
	}
	printk("ext2_count_free_inodes: stored = %lu, computed = %lu, %lu\n",
		le32_to_cpu(es->s_free_inodes_count), desc_count, bitmap_count);
	unlock_super (sb);
	return desc_count;
#else
	return le32_to_cpu(sb->u.ext2_sb.s_es->s_free_inodes_count);
#endif
}

#ifdef CONFIG_EXT2_CHECK
/* Called at mount-time, super-block is locked */
void ext2_check_inodes_bitmap (struct super_block * sb)
{
	struct ext2_super_block * es;
	unsigned long desc_count, bitmap_count, x;
	int bitmap_nr;
	struct ext2_group_desc * gdp;
	int i;

	es = sb->u.ext2_sb.s_es;
	desc_count = 0;
	bitmap_count = 0;
	gdp = NULL;
	for (i = 0; i < sb->u.ext2_sb.s_groups_count; i++) {
		gdp = ext2_get_group_desc (sb, i, NULL);
		if (!gdp)
			continue;
		desc_count += le16_to_cpu(gdp->bg_free_inodes_count);
		bitmap_nr = load_inode_bitmap (sb, i);
		if (bitmap_nr < 0)
			continue;
		
		x = ext2_count_free (sb->u.ext2_sb.s_inode_bitmap[bitmap_nr],
				     EXT2_INODES_PER_GROUP(sb) / 8);
		if (le16_to_cpu(gdp->bg_free_inodes_count) != x)
			ext2_error (sb, "ext2_check_inodes_bitmap",
				    "Wrong free inodes count in group %d, "
				    "stored = %d, counted = %lu", i,
				    le16_to_cpu(gdp->bg_free_inodes_count), x);
		bitmap_count += x;
	}
	if (le32_to_cpu(es->s_free_inodes_count) != bitmap_count)
		ext2_error (sb, "ext2_check_inodes_bitmap",
			    "Wrong free inodes count in super block, "
			    "stored = %lu, counted = %lu",
			    (unsigned long) le32_to_cpu(es->s_free_inodes_count),
			    bitmap_count);
}
#endif