On Fri, Aug 28, 2020 at 09:13:07PM +0000, Trond Myklebust wrote:
> On Fri, 2020-08-28 at 15:58 -0400, Chuck Lever wrote:
> > If a write delegation isn't available, the Linux NFS client uses
> > a zero-stateid when performing a SETATTR.
> >
> > If that client happens to hold a read delegation, the server will
> > recall it immediately, resulting in a short delay while the
> > CB_RECALL operation is done. Optimize out this delay by having the
> > client return any delegation it may hold on a file before issuing a
> > SETATTR(zero-stateid) on that file.
> >
> > Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> > ---
> > fs/nfs/nfs4proc.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> > index dbd01548335b..53a56250cf4b 100644
> > --- a/fs/nfs/nfs4proc.c
> > +++ b/fs/nfs/nfs4proc.c
> > @@ -3314,6 +3314,7 @@ static int _nfs4_do_setattr(struct inode
> > *inode,
> > goto zero_stateid;
> > } else {
> > zero_stateid:
> > + nfs4_inode_return_delegation(inode);
> > nfs4_stateid_copy(&arg->stateid, &zero_stateid);
> > }
> > if (delegation_cred)
> >
>
> This should not be needed for NFSv4.1 or greater. Only NFSv4.0 is
> incapable of identifying the caller and recognising that it is the
> holder of the delegation.
And the server should be getting this right now in the >=4.1 case, so
let me know if you see otherwise.
--b.
