Re: [PATCH 1/2] namespaces: give each namespace a serial number

On 14/05/02, Serge E. Hallyn wrote: > Quoting Richard Guy Briggs (rgb(a)redhat.com): > > Most of this looks reasonable, but I'm curious about something, > > > +/** > > + * ns_serial - compute a serial number for the namespace > > + * > > + * Compute a serial number for the namespace to uniquely identify it in > > + * audit records. > > + */ > > +unsigned int ns_serial(void) > > +{ > > + static DEFINE_SPINLOCK(serial_lock); > > + static unsigned int serial = 4; /* reserved for IPC, UTS, user, PID */ > > + > > + unsigned long flags; > > + unsigned int ret; > > + > > + spin_lock_irqsave(&serial_lock, flags); > > + do { > > + ret = ++serial; > > + } while (unlikely(!ret)); > > Why exactly are you doing this? Surely if serial is going to > wrap around we've got a bigger problem than just wanting go > bump one more time? Thanks for catching this. The code was templated off audit_serial() which tries to solve a different problem and rolling it is much more likely. I hadn't noticed that rollover protection. However, I *had* thought of making it a long (which would be the same size on 32-bit arches, but larger on 64-bit) since a 64-bit system is more likely to roll it out of sheer speed and resource availability. But perhaps a long long would be safer.