linux-kernel - [PATCH] nfds: avoid gettimeofday for nfssvc

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Message-Id: <20171019100435.1170955-1-arnd@arndb.de>
Date:   Thu, 19 Oct 2017 12:04:11 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     y2038@...ts.linaro.org, "J. Bruce Fields" <bfields@...ldses.org>,
        Jeff Layton <jlayton@...chiereds.net>
Cc:     Deepa Dinamani <deepa.kernel@...il.com>,
        linux-fsdevel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        Trond Myklebust <trond.myklebust@...marydata.com>,
        NeilBrown <neilb@...e.com>, Kinglong Mee <kinglongmee@...il.com>,
        linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] 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 <arnd@...db.de>
---
 fs/nfsd/netns.h    |  2 +-
 fs/nfsd/nfs3xdr.c  | 10 ++++++----
 fs/nfsd/nfs4proc.c |  5 +++--
 fs/nfsd/nfssvc.c   |  2 +-
 4 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h
index 3714231a9d0f..1c91391f4805 100644
--- a/fs/nfsd/netns.h
+++ b/fs/nfsd/netns.h
@@ -107,7 +107,7 @@ struct nfsd_net {
 	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
diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
index bf444b664011..3579e0ae1131 100644
--- a/fs/nfsd/nfs3xdr.c
+++ b/fs/nfsd/nfs3xdr.c
@@ -747,8 +747,9 @@ nfs3svc_encode_writeres(struct svc_rqst *rqstp, __be32 *p)
 	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);
 }
@@ -1118,8 +1119,9 @@ nfs3svc_encode_commitres(struct svc_rqst *rqstp, __be32 *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);
 }
diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 7896f841482e..008ea0b627d0 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -564,10 +564,11 @@ static void gen_boot_verifier(nfs4_verifier *verifier, struct net *net)
 
 	/*
 	 * 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));
 }
 
diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index 6bbc717f40f2..28ff3e078af6 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -516,7 +516,7 @@ int nfsd_create_serv(struct net *net)
 		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;
 }
 
-- 
2.9.0