net/unix : possible race bug at unix_create1()

Hi. I am reporting a possible race bug at unix_create1()
in net/unix/af_unix.c of Linux 2.6.30.4.

Concurrent executions of unix_create1() function
in two different threads may result race condition
when unix_nr_socks +1 == 2 * get_max_files().

It is possible that no thread can pass the if-condition
checking if two atomic_inc() operations are executed
before.

It seems that it would be better to combine two
atomic operations into one atomic_inc_and_return().

Please examine the code and let me know your opinion.

Thank you

Sincerely
Shin Hong