NFSD: De-duplicate net_generic(SVC_NET(rqstp), nfsd_net_id)

Since this pointer is used repeatedly, move it to a stack variable.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/vfs.c

@@ -954,6 +954,7 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfsd_file *nf,
 				unsigned long *cnt, int stable,
 				__be32 *verf)
 {
+	struct nfsd_net		*nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
 	struct file		*file = nf->nf_file;
 	struct super_block	*sb = file_inode(file)->i_sb;
 	struct svc_export	*exp;
@@ -998,13 +999,10 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfsd_file *nf,
 	iov_iter_kvec(&iter, WRITE, vec, vlen, *cnt);
 	since = READ_ONCE(file->f_wb_err);
 	if (verf)
-		nfsd_copy_boot_verifier(verf,
-				net_generic(SVC_NET(rqstp),
-				nfsd_net_id));
+		nfsd_copy_boot_verifier(verf, nn);
 	host_err = vfs_iter_write(file, &iter, &pos, flags);
 	if (host_err < 0) {
-		nfsd_reset_boot_verifier(net_generic(SVC_NET(rqstp),
-					 nfsd_net_id));
+		nfsd_reset_boot_verifier(nn);
 		goto out_nfserr;
 	}
 	*cnt = host_err;
@@ -1017,8 +1015,7 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfsd_file *nf,
 	if (stable && use_wgather) {
 		host_err = wait_for_concurrent_writes(file);
 		if (host_err < 0)
-			nfsd_reset_boot_verifier(net_generic(SVC_NET(rqstp),
-						 nfsd_net_id));
+			nfsd_reset_boot_verifier(nn);
 	}
 
 out_nfserr: