Re: another nfs puzzle

[Peter Staubach]

Trond Myklebust wrote:

> On Wed, 2005-12-07 at 09:01 -0500, Peter Staubach wrote:
>  
>
> > Kenny Simpson wrote:
> >
> >    
> >
> > > Hi again,
> > > I am seeing some odd behavior with O_DIRECT.  If a file opened with O_DIRECT has a page mmap'd,
> > > and the file is extended via pwrite, then the mmap'd region seems to get lost - i.e. it neither
> > > takes up system memory, nor does it get written out.
> > >
> > >
> > >      
> > I don't think that I understand why or how the kernel allows a file,
> > which was opened with O_DIRECT, to be mmap'd.  The use of O_DIRECT
> > implies no caching and mmap implies the use of caching.
> >    
>
> In this context it doesn't matter whether or not the you use the same
> file descriptor. The problem is the same if my process opens the file
> for O_DIRECT and then your process open it for normal I/O, and mmaps it.

Yup, same problem.  Why is this allowed?  Does it really work correctly?

   Thanx...

      ps
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/