nfds: avoid gettimeofday for nfssvc_boot time

do_gettimeofday() is deprecated and we should generally use time64_t
based functions instead.

In case of nfsd, all three users of nfssvc_boot only use the initial
time as a unique token, and are not affected by it overflowing, so they
are not affected by the y2038 overflow.

This converts the structure to timespec64 anyway and adds comments
to all uses, to document that we have thought about it and avoid
having to look at it again.

Signed-off-by: Arnd Bergmann <[e-mail]>
Signed-off-by: J. Bruce Fields <[e-mail]>

fs/nfsd/netns.h

···
 	bool lockd_up;
 
 	/* Time of server startup */
-	struct timeval nfssvc_boot;
+	struct timespec64 nfssvc_boot;
 
 	/*
 	 * Max number of connections this nfsd container will allow. Defaults

fs/nfsd/nfs3xdr.c

···
 	if (resp->status == 0) {
 		*p++ = htonl(resp->count);
 		*p++ = htonl(resp->committed);
-		*p++ = htonl(nn->nfssvc_boot.tv_sec);
-		*p++ = htonl(nn->nfssvc_boot.tv_usec);
+		/* unique identifier, y2038 overflow can be ignored */
+		*p++ = htonl((u32)nn->nfssvc_boot.tv_sec);
+		*p++ = htonl(nn->nfssvc_boot.tv_nsec);
 	}
 	return xdr_ressize_check(rqstp, p);
 }
···
 	p = encode_wcc_data(rqstp, p, &resp->fh);
 	/* Write verifier */
 	if (resp->status == 0) {
-		*p++ = htonl(nn->nfssvc_boot.tv_sec);
-		*p++ = htonl(nn->nfssvc_boot.tv_usec);
+		/* unique identifier, y2038 overflow can be ignored */
+		*p++ = htonl((u32)nn->nfssvc_boot.tv_sec);
+		*p++ = htonl(nn->nfssvc_boot.tv_nsec);
 	}
 	return xdr_ressize_check(rqstp, p);
 }

fs/nfsd/nfs4proc.c

···
 
 	/*
 	 * This is opaque to client, so no need to byte-swap. Use
-	 * __force to keep sparse happy
+	 * __force to keep sparse happy. y2038 time_t overflow is
+	 * irrelevant in this usage.
 	 */
 	verf[0] = (__force __be32)nn->nfssvc_boot.tv_sec;
-	verf[1] = (__force __be32)nn->nfssvc_boot.tv_usec;
+	verf[1] = (__force __be32)nn->nfssvc_boot.tv_nsec;
 	memcpy(verifier->data, verf, sizeof(verifier->data));
 }
 

fs/nfsd/nfssvc.c

···
 		register_inet6addr_notifier(&nfsd_inet6addr_notifier);
 #endif
 	}
-	do_gettimeofday(&nn->nfssvc_boot);		/* record boot time */
+	ktime_get_real_ts64(&nn->nfssvc_boot); /* record boot time */
 	return 0;
 }