[PATCH] nfsd: set the server_scope during service startup

[Scott Mayhew <smayhew@redhat.com>]

Currently, nfsd4_encode_exchange_id() encodes the utsname nodename
string in the server_scope field.  In a multi-host container
environemnt, if an nfsd container is restarted on a different host than
it was originally running on, clients will see a server_scope mismatch
and will not attempt to reclaim opens.

Instead, set the server_scope while we're in a process context during
service startup, so we get the utsname nodename of the current process
and store that in nfsd_net.

Signed-off-by: Scott Mayhew <smayhew@redhat.com>
---
 fs/nfsd/netns.h   | 1 +
 fs/nfsd/nfs4xdr.c | 3 ++-
 fs/nfsd/nfssvc.c  | 3 +++
 3 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h
index 2baf32311e00..c6d95700105e 100644
--- a/fs/nfsd/netns.h
+++ b/fs/nfsd/netns.h
@@ -172,6 +172,7 @@ struct nfsd_net {
 	unsigned int             longest_chain_cachesize;
 
 	struct shrinker		nfsd_reply_cache_shrinker;
+	char			server_scope[UNX_MAXNODENAME+1];
 };
 
 /* Simple check to find out if a given net was properly initialized */
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 9761512674a0..209174ee431a 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -4005,10 +4005,11 @@ nfsd4_encode_exchange_id(struct nfsd4_compoundres *resp, __be32 nfserr,
 	int major_id_sz;
 	int server_scope_sz;
 	uint64_t minor_id = 0;
+	struct nfsd_net *nn = net_generic(SVC_NET(resp->rqstp), nfsd_net_id);
 
 	major_id = utsname()->nodename;
 	major_id_sz = strlen(major_id);
-	server_scope = utsname()->nodename;
+	server_scope = nn->server_scope;
 	server_scope_sz = strlen(server_scope);
 
 	p = xdr_reserve_space(xdr,
diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index 3b77b904212d..c4e00979aca4 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -749,6 +749,9 @@ nfsd_svc(int nrservs, struct net *net, const struct cred *cred)
 	if (nrservs == 0 && nn->nfsd_serv == NULL)
 		goto out;
 
+	strlcpy(nn->server_scope, utsname()->nodename,
+		sizeof(nn->server_scope));
+
 	error = nfsd_create_serv(net);
 	if (error)
 		goto out;
-- 
2.24.1