mknod() will fail and the file will be not created if:
[ENOTDIR]
A component of the path prefix is not a directory.
[ENAMETOOLONG]
A component of a pathname exceeded {NAME_MAX} characters, or an entire path name exceeded {PATH_MAX} characters.
[ENOENT]
A component of the path prefix does not exist.
[EACCES]
Search permission is denied for a component of the path prefix.
[ELOOP]
Too many symbolic links were encountered in translating the pathname.
[EPERM]
The process's effective user ID is not super-user.
[EIO]
An I/O error occurred while making the directory entry or allocating the inode.
[ENOSPC]
The directory in which the entry for the new node is being placed cannot be extended because there is no space left on the file system containing the directory.
[ENOSPC]
There are no free inodes on the file system on which the node is being created.
[EDQUOT]
The directory in which the entry for the new node is being placed cannot be extended because the user's quota of disk blocks on the file system containing the directory has been exhausted.
[EDQUOT]
The user's quota of inodes on the file system on which the node is being created has been exhausted.
[EROFS]
The named file resides on a read-only file system.
[EEXIST]
The named file exists.
[EFAULT]
path points outside the process's allocated address space.