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

[Trond Myklebust <trond.myklebust@fys.uio.no>]

>>>>> " " == Linus Torvalds <torvalds@osdl.org> writes:

     > On Fri, 10 Oct 2003, Joel Becker wrote:
    >>
    >> msync() forces write(), like fsync().  It doesn't force read().

     > Actually, the kernel has a "readahead(fd, offset, size)" system
     > call that will start asynchronous read-ahead on any
     > mapping. After that, just touching the page will obviously map
     > in and synchronize the result.

That's different. That's just preheating the page cache.

It does nothing for the case Joel mentioned where 2 different nodes
are writing to the same device, and you need to force a read in order
to resynchronize the page cache.
Apart from O_DIRECT, we have nothing in the kernel as it stands that
will allow userland to deal with this case.

Cheers,
  Trond