Push Giant a bit further off the NFS server in a number of straight

forward cases by converting from unconditional acquisition of Giant
around vnode operations to conditional acquisition:

- Remove nfsrv_access_withgiant(), and cause nfsrv_access() to now
  assert that Giant will be held if it is required for the vnode.

- Add nfsrv_fhtovp_locked(), which will drop the NFS server lock if
  required, and modify nfsrv_fhtovp() to conditionally acquire
  Giant if required.

- In the VOP's not dealing with more than one vnode at a time (i.e.,
  not involving a lookup), conditionally acquire Giant.

This removes Giant use for MPSAFE file systems for a number of quite
important RPCs, including getattr, read, write.  It leaves
unconditional Giant acquisitions in vnode operations that interact
with the name space or more than one vnode at a time as these
require further work.

Tested by:	kris
Reviewed by:	kib

1 files changed, 3 insertions, 0 deletions

diff --git a/sys/nfsserver/nfs.h b/sys/nfsserver/nfs.h
index c3b231a..292584e 100644
--- a/sys/nfsserver/nfs.h
+++ b/sys/nfsserver/nfs.h
@@ -360,6 +360,9 @@ int	nfsrv_create(struct nfsrv_descript *nfsd, struct nfssvc_sock *slp,
 	    struct thread *td, struct mbuf **mrq);
 int	nfsrv_fhtovp(fhandle_t *, int, struct vnode **, struct ucred *,
 	    struct nfssvc_sock *, struct sockaddr *, int *, int);
+int	nfsrv_fhtovp_locked(fhandle_t *, int, struct vnode **,
+	    struct ucred *, struct nfssvc_sock *, struct sockaddr *, int *,
+	    int);
 int	nfsrv_setpublicfs(struct mount *, struct netexport *,
 	    struct export_args *);
 int	nfs_ispublicfh(fhandle_t *);