f2fs: fix incorrect free inode count in ->statfs

While calculating inode count that we can create at most in the left space,
we should consider space which data/node blocks occupied, since we create
data/node mixly in main area. So fix the wrong calculation in ->statfs.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/super.c

@@ -852,7 +852,8 @@ static int f2fs_statfs(struct dentry *dentry, struct kstatfs *buf)
 	buf->f_bavail = user_block_count - valid_user_blocks(sbi);
 
 	buf->f_files = sbi->total_node_count - F2FS_RESERVED_NODE_NUM;
-	buf->f_ffree = buf->f_files - valid_inode_count(sbi);
+	buf->f_ffree = min(buf->f_files - valid_node_count(sbi),
+							buf->f_bavail);
 
 	buf->f_namelen = F2FS_NAME_LEN;
 	buf->f_fsid.val[0] = (u32)id;