ext4: teach the inode allocator to use a goal inode number

Enhance the inode allocator to take a goal inode number as a
paremeter; if it is specified, it takes precedence over Orlov or
parent directory inode allocation algorithms.

The extents migration function uses the goal inode number so that the
extent trees allocated the migration function use the correct flex_bg.
In the future, the goal inode functionality will also be used to
allocate an adjacent inode for the extended attributes.

Also, for testing purposes the goal inode number can be specified via
/sys/fs/{dev}/inode_goal.  This can be useful for testing inode
allocation beyond 2^32 blocks on very large filesystems.

Signed-off-by: Andreas Dilger <adilger@sun.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

Documentation/ABI/testing/sysfs-fs-ext4

@@ -79,3 +79,13 @@ Description:
 		This file is read-only and shows the number of
 		kilobytes of data that have been written to this
 		filesystem since it was mounted.
+
+What:		/sys/fs/ext4/<disk>/inode_goal
+Date:		June 2008
+Contact:	"Theodore Ts'o" <tytso@mit.edu>
+Description:
+		Tuning parameter which (if non-zero) controls the goal
+		inode used by the inode allocator in p0reference to
+		all other allocation hueristics.  This is intended for
+		debugging use only, and should be 0 on production
+		systems.

fs/ext4/ext4.h

@@ -863,6 +863,7 @@ struct ext4_sb_info {
 	int s_inode_size;
 	int s_first_ino;
 	unsigned int s_inode_readahead_blks;
+	unsigned int s_inode_goal;
 	spinlock_t s_next_gen_lock;
 	u32 s_next_generation;
 	u32 s_hash_seed[4];
@@ -1316,7 +1317,7 @@ extern int ext4fs_dirhash(const char *name, int len, struct
 
 /* ialloc.c */
 extern struct inode *ext4_new_inode(handle_t *, struct inode *, int,
-				    const struct qstr *qstr);
+				    const struct qstr *qstr, __u32 goal);
 extern void ext4_free_inode(handle_t *, struct inode *);
 extern struct inode * ext4_orphan_get(struct super_block *, unsigned long);
 extern unsigned long ext4_count_free_inodes(struct super_block *);

fs/ext4/ialloc.c

@@ -799,7 +799,7 @@ err_ret:
  * group to find a free inode.
  */
 struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, int mode,
-			     const struct qstr *qstr)
+			     const struct qstr *qstr, __u32 goal)
 {
 	struct super_block *sb;
 	struct buffer_head *inode_bitmap_bh = NULL;
@@ -830,6 +830,16 @@ struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, int mode,
 	ei = EXT4_I(inode);
 	sbi = EXT4_SB(sb);
 
+	if (!goal)
+		goal = sbi->s_inode_goal;
+
+	if (goal && goal < le32_to_cpu(sbi->s_es->s_inodes_count)) {
+		group = (goal - 1) / EXT4_INODES_PER_GROUP(sb);
+		ino = (goal - 1) % EXT4_INODES_PER_GROUP(sb);
+		ret2 = 0;
+		goto got_group;
+	}
+
 	if (sbi->s_log_groups_per_flex && test_opt(sb, OLDALLOC)) {
 		ret2 = find_group_flex(sb, dir, &group);
 		if (ret2 == -1) {
@@ -858,7 +868,7 @@ got_group:
 	if (ret2 == -1)
 		goto out;
 
-	for (i = 0; i < ngroups; i++) {
+	for (i = 0; i < ngroups; i++, ino = 0) {
 		err = -EIO;
 
 		gdp = ext4_get_group_desc(sb, group, &group_desc_bh);
@@ -870,8 +880,6 @@ got_group:
 		if (!inode_bitmap_bh)
 			goto fail;
 
-		ino = 0;
-
 repeat_in_this_group:
 		ino = ext4_find_next_zero_bit((unsigned long *)
 					      inode_bitmap_bh->b_data,

fs/ext4/migrate.c

@@ -458,6 +458,7 @@ int ext4_ext_migrate(struct inode *inode)
 	struct inode *tmp_inode = NULL;
 	struct list_blocks_struct lb;
 	unsigned long max_entries;
+	__u32 goal;
 
 	/*
 	 * If the filesystem does not support extents, or the inode
@@ -483,8 +484,10 @@ int ext4_ext_migrate(struct inode *inode)
 		retval = PTR_ERR(handle);
 		return retval;
 	}
+	goal = (((inode->i_ino - 1) / EXT4_INODES_PER_GROUP(inode->i_sb)) *
+		EXT4_INODES_PER_GROUP(inode->i_sb)) + 1;
 	tmp_inode = ext4_new_inode(handle, inode->i_sb->s_root->d_inode,
-				   S_IFREG, 0);
+				   S_IFREG, 0, goal);
 	if (IS_ERR(tmp_inode)) {
 		retval = -ENOMEM;
 		ext4_journal_stop(handle);

fs/ext4/namei.c

@@ -1782,7 +1782,7 @@ retry:
 	if (IS_DIRSYNC(dir))
 		ext4_handle_sync(handle);
 
-	inode = ext4_new_inode(handle, dir, mode, &dentry->d_name);
+	inode = ext4_new_inode(handle, dir, mode, &dentry->d_name, 0);
 	err = PTR_ERR(inode);
 	if (!IS_ERR(inode)) {
 		inode->i_op = &ext4_file_inode_operations;
@@ -1816,7 +1816,7 @@ retry:
 	if (IS_DIRSYNC(dir))
 		ext4_handle_sync(handle);
 
-	inode = ext4_new_inode(handle, dir, mode, &dentry->d_name);
+	inode = ext4_new_inode(handle, dir, mode, &dentry->d_name, 0);
 	err = PTR_ERR(inode);
 	if (!IS_ERR(inode)) {
 		init_special_inode(inode, inode->i_mode, rdev);
@@ -1853,7 +1853,8 @@ retry:
 	if (IS_DIRSYNC(dir))
 		ext4_handle_sync(handle);
 
-	inode = ext4_new_inode(handle, dir, S_IFDIR | mode, &dentry->d_name);
+	inode = ext4_new_inode(handle, dir, S_IFDIR | mode,
+			       &dentry->d_name, 0);
 	err = PTR_ERR(inode);
 	if (IS_ERR(inode))
 		goto out_stop;
@@ -2264,7 +2265,8 @@ retry:
 	if (IS_DIRSYNC(dir))
 		ext4_handle_sync(handle);
 
-	inode = ext4_new_inode(handle, dir, S_IFLNK|S_IRWXUGO, &dentry->d_name);
+	inode = ext4_new_inode(handle, dir, S_IFLNK|S_IRWXUGO,
+			       &dentry->d_name, 0);
 	err = PTR_ERR(inode);
 	if (IS_ERR(inode))
 		goto out_stop;

fs/ext4/super.c

@@ -2206,6 +2206,7 @@ EXT4_RO_ATTR(session_write_kbytes);
 EXT4_RO_ATTR(lifetime_write_kbytes);
 EXT4_ATTR_OFFSET(inode_readahead_blks, 0644, sbi_ui_show,
 		 inode_readahead_blks_store, s_inode_readahead_blks);
+EXT4_RW_ATTR_SBI_UI(inode_goal, s_inode_goal);
 EXT4_RW_ATTR_SBI_UI(mb_stats, s_mb_stats);
 EXT4_RW_ATTR_SBI_UI(mb_max_to_scan, s_mb_max_to_scan);
 EXT4_RW_ATTR_SBI_UI(mb_min_to_scan, s_mb_min_to_scan);
@@ -2218,6 +2219,7 @@ static struct attribute *ext4_attrs[] = {
 	ATTR_LIST(session_write_kbytes),
 	ATTR_LIST(lifetime_write_kbytes),
 	ATTR_LIST(inode_readahead_blks),
+	ATTR_LIST(inode_goal),
 	ATTR_LIST(mb_stats),
 	ATTR_LIST(mb_max_to_scan),
 	ATTR_LIST(mb_min_to_scan),