On Apr 12, 2006 14:28 -0700, Mingming Cao wrote: > where the check for unsigned long overflow is only turned on 32 bit > platforms. > > > Or make the counter s64? so that it stays 64 bit on all arches? > > > > Well, don't we have the problem : 64 bit counter add/dec/update is not > always atomic on all 32 bit platforms? There are risk that we will get > bogus global value. My thought here is that the per-cpu counter could still be a 32-bit counter and the global value could be a 64-bit value. That way, we don't need to mess with 64-bit math in the common case, and we can still have a 64-bit global value. The minor drawback would be that we can't have a per-cpu delta of more than 2^31 at a time, but I don't think this is a worry here. > > why not change the global per-cpu counter type to unsigned long (as we > > discussed earlier), so we don't need the extra "ul" flags and interfaces, > > and all arches get a standard unsigned long return type? > > We could also > > do away with percpu_read_positive then no? The applications for per-cpu > > counters is going to be upcounters always methinks... The "percpu_read_positive" usage is broken in any case, since it doesn't correctly handle the case where there is no space in the filesystem at all. The calling code (ext3_statfs) really needs to just call percpu_read() and then return zero if this is negative. Cheers, Andreas -- Andreas Dilger Principal Software Engineer Cluster File Systems, Inc. - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
