[PATCH] knfsd: lockd: optionally use hostnames for identifying peers

This patch adds the nsm_use_hostnames sysctl and module param.  If set, lockd
will use the client's name (as given in the NLM arguments) to find the NSM
handle.  This makes recovery work when the NFS peer is multi-homed, and the
reboot notification arrives from a different IP than the original lock calls.

Signed-off-by: Olaf Kirch <okir@suse.de>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/lockd/mon.c b/fs/lockd/mon.c
index 626b6c1..709cf7c 100644
--- a/fs/lockd/mon.c
+++ b/fs/lockd/mon.c
@@ -47,6 +47,7 @@
 	}
 
 	memset(&args, 0, sizeof(args));
+	args.mon_name = nsm->sm_name;
 	args.addr = nsm->sm_addr.sin_addr.s_addr;
 	args.prog = NLM_PROGRAM;
 	args.vers = 3;
@@ -150,7 +151,7 @@
 static u32 *
 xdr_encode_common(struct rpc_rqst *rqstp, u32 *p, struct nsm_args *argp)
 {
-	char	buffer[20];
+	char	buffer[20], *name;
 
 	/*
 	 * Use the dotted-quad IP address of the remote host as
@@ -158,8 +159,13 @@
 	 * hostname first for whatever remote hostname it receives,
 	 * so this works alright.
 	 */
-	sprintf(buffer, "%u.%u.%u.%u", NIPQUAD(argp->addr));
-	if (!(p = xdr_encode_string(p, buffer))
+	if (nsm_use_hostnames) {
+		name = argp->mon_name;
+	} else {
+		sprintf(buffer, "%u.%u.%u.%u", NIPQUAD(argp->addr));
+		name = buffer;
+	}
+	if (!(p = xdr_encode_string(p, name))
 	 || !(p = xdr_encode_string(p, utsname()->nodename)))
 		return ERR_PTR(-EIO);
 	*p++ = htonl(argp->prog);