f2fs: move f2fs_balance_fs to punch_hole

The f2fs_fallocate() has two operations: punch_hole and expand_size.

Only in the case of punch_hole, dirty node pages can be produced, so let's
trigger f2fs_balance_fs() in this case only.
Furthermore, let's trigger it at every data truncation routine.
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

fs/f2fs/file.c

@@ -410,6 +410,8 @@ int truncate_hole(struct inode *inode, pgoff_t pg_start, pgoff_t pg_end)
 		struct dnode_of_data dn;
 		struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
 
+		f2fs_balance_fs(sbi);
+
 		mutex_lock_op(sbi, DATA_TRUNC);
 		set_new_dnode(&dn, inode, NULL, NULL, 0);
 		err = get_dnode_of_data(&dn, index, RDONLY_NODE);
@@ -537,7 +539,6 @@ static long f2fs_fallocate(struct file *file, int mode,
 				loff_t offset, loff_t len)
 {
 	struct inode *inode = file->f_path.dentry->d_inode;
-	struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
 	long ret;
 
 	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
@@ -552,8 +553,6 @@ static long f2fs_fallocate(struct file *file, int mode,
 		inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 		mark_inode_dirty(inode);
 	}
-
-	f2fs_balance_fs(sbi);
 	return ret;
 }