RE: [PATCH 0/3] Include OFD lock owners when looking up state

["Frank Filz" <ffilzlnx@mindspring.com>]

> > On Fri, Apr 1, 2016 at 11:48 AM, Benjamin Coddington
> > <bcodding@redhat.com> wrote:
> > > On Fri, 1 Apr 2016, Trond Myklebust wrote:
> > >
> > >> On Fri, Apr 1, 2016 at 11:34 AM, Benjamin Coddington
> > >> <bcodding@redhat.com> wrote:
> > >> > The client sends IO only under the open stateid when using OFD
> > >> > (and flock) locking instead of the appropriate lock stateid
> > >> > because the nfs_lock_context only tracks POSIX lockowners, which
> > >> > is the reference to the process' file table.
> > >> >
> > >> > This is a problem for two reasons.  The first is that rfc7530,
> > >> > section-9.1.4.5 states that IO sent by an entity corresponding to
> > >> > the lock-owner which holds a byte-range lock should be sent under
> > >> > the lock stateid for that lock.  Otherwise, a server enforcing
> > >> > mandatory byte-range locking might reject that operation.
> > >> > Secondly, not tracking OFD lock owners means that accounting for
> > >> > IO sent under those owners is broken.  That creates a problem for
> > >> > some work to guarantee an unlock will be sent after operations
> scheduled under a lock complete.
> > >>
> > >> OK. Can we just kill this in the bud? No support for OFD locks in
NFS:
> > >> this is nuts....
> > >
> > > Will you explain why it is nuts?  That would be helpful for me.
> >
> > The point of the OFD crap was that they should work exactly like POSIX
> > locks except for the unlock-on-close, the latter being managed by the
> > VFS layer. If we have to make loads of changes to NFS in order to
> > change the tracking of lock owners, then the design itself is broken,
> > and needs to be fixed.
> 
> 
> No, there were other reasons for them as well.
> 
> For instance, traditional POSIX locks are useless for serializing betwee
> threads within the same process because the lock owner is always the same
> regardless of which thread you're using. With OFD locks, this is possible
if
> each thread has its own file description.

Which is a feature humongously useful for Ganesha... Not that Ganesha will
ever use OFD locks over NFS...

I have used OFD locks over NFS to make sure that Ganesha handles one
open-owner to many lock-owners correctly.

Of course it may be a real question if anyone other than Ganesha (and maybe
Samba) will ever use OFD locks since they aren't a POSIX standard...

Frank


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