Re: statfs() / statvfs() syscall ballsup...

[Trond Myklebust]

>>>>> " " == Andrew Morton <akpm@xxxxxxxx> writes:

     > POSIX does not define the fadvise() semantics very clearly, so
     > it is largely up to us to decide what makes sense.  There are a
     > number of things which we can do quite easily in there - it's
     > mainly a matter of working out exactly what we want to do.

Possibly, but there really is no need to get over-creative either. The
SUS definition of msync(MS_INVALIDATE) reads as follows:

        When MS_INVALIDATE is specified, msync() shall invalidate all
        cached copies of mapped data that are inconsistent with the
        permanent storage locations such that subsequent references
        shall obtain data that was consistent with the permanent
        storage locations sometime between the call to msync() and the
        first subsequent memory reference to the data.

(ref: http://www.opengroup.org/onlinepubs/007904975/functions/msync.html)

i.e. a strict implementation would mean that msync() will in fact act
as a synchronization point that is fully consistent with Linus'
proposal for a "this region is stale" function.

Unfortunately Linux appears incapable of implementing such a strict
definition of msync() as it stands.

Cheers,
  Trond
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