nfsd: don't take nfsd4_copy ref for OP_OFFLOAD_STATUS

We're not doing any blocking operations for OP_OFFLOAD_STATUS, so taking
and putting a reference is a waste of effort. Take the client lock,
search for the copy and fetch the wr_bytes_written field and return.

Also, make find_async_copy a static function.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Olga Kornievskaia <kolga@netapp.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfs4proc.c

@@ -1824,23 +1824,34 @@ nfsd4_copy(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	goto out;
 }
 
-struct nfsd4_copy *
-find_async_copy(struct nfs4_client *clp, stateid_t *stateid)
+static struct nfsd4_copy *
+find_async_copy_locked(struct nfs4_client *clp, stateid_t *stateid)
 {
 	struct nfsd4_copy *copy;
 
-	spin_lock(&clp->async_lock);
+	lockdep_assert_held(&clp->async_lock);
+
 	list_for_each_entry(copy, &clp->async_copies, copies) {
 		if (memcmp(&copy->cp_stateid.cs_stid, stateid, NFS4_STATEID_SIZE))
 			continue;
-		refcount_inc(&copy->refcount);
-		spin_unlock(&clp->async_lock);
 		return copy;
 	}
-	spin_unlock(&clp->async_lock);
 	return NULL;
 }
 
+static struct nfsd4_copy *
+find_async_copy(struct nfs4_client *clp, stateid_t *stateid)
+{
+	struct nfsd4_copy *copy;
+
+	spin_lock(&clp->async_lock);
+	copy = find_async_copy_locked(clp, stateid);
+	if (copy)
+		refcount_inc(&copy->refcount);
+	spin_unlock(&clp->async_lock);
+	return copy;
+}
+
 static __be32
 nfsd4_offload_cancel(struct svc_rqst *rqstp,
 		     struct nfsd4_compound_state *cstate,
@@ -1925,22 +1936,24 @@ nfsd4_fallocate(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	nfsd_file_put(nf);
 	return status;
 }
+
 static __be32
 nfsd4_offload_status(struct svc_rqst *rqstp,
 		     struct nfsd4_compound_state *cstate,
 		     union nfsd4_op_u *u)
 {
 	struct nfsd4_offload_status *os = &u->offload_status;
-	__be32 status = 0;
+	__be32 status = nfs_ok;
 	struct nfsd4_copy *copy;
 	struct nfs4_client *clp = cstate->clp;
 
-	copy = find_async_copy(clp, &os->stateid);
-	if (copy) {
+	spin_lock(&clp->async_lock);
+	copy = find_async_copy_locked(clp, &os->stateid);
+	if (copy)
 		os->count = copy->cp_res.wr_bytes_written;
-		nfs4_put_copy(copy);
-	} else
+	else
 		status = nfserr_bad_stateid;
+	spin_unlock(&clp->async_lock);
 
 	return status;
 }

fs/nfsd/state.h

@@ -705,8 +705,6 @@ extern struct nfs4_client_reclaim *nfs4_client_to_reclaim(struct xdr_netobj name
 extern bool nfs4_has_reclaimed_state(struct xdr_netobj name, struct nfsd_net *nn);
 
 void put_nfs4_file(struct nfs4_file *fi);
-extern struct nfsd4_copy *
-find_async_copy(struct nfs4_client *clp, stateid_t *staetid);
 extern void nfs4_put_cpntf_state(struct nfsd_net *nn,
 				 struct nfs4_cpntf_state *cps);
 extern __be32 manage_cpntf_state(struct nfsd_net *nn, stateid_t *st,