SUNRPC: Faster detection if gssd is actually running

Recent changes to the NFS security flavour negotiation mean that
we have a stronger dependency on rpc.gssd. If the latter is not
running, because the user failed to start it, then we time out
and mark the container as not having an instance. We then
use that information to time out faster the next time.

If, on the other hand, the rpc.gssd successfully binds to an rpc_pipe,
then we mark the container as having an rpc.gssd instance.

Signed-off-by: Trond Myklebust <[e-mail]>

net/sunrpc/auth_gss/auth_gss.c

···
 #include <linux/sunrpc/gss_api.h>
 #include <asm/uaccess.h>
 
+#include "../netns.h"
+
 static const struct rpc_authops authgss_ops;
 
 static const struct rpc_credops gss_credops;
···
 static inline int
 gss_create_upcall(struct gss_auth *gss_auth, struct gss_cred *gss_cred)
 {
+	struct net *net = rpc_net_ns(gss_auth->client);
+	struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
 	struct rpc_pipe *pipe;
 	struct rpc_cred *cred = &gss_cred->gc_base;
 	struct gss_upcall_msg *gss_msg;
+	unsigned long timeout;
 	DEFINE_WAIT(wait);
 	int err;
 
···
 		__func__, from_kuid(&init_user_ns, cred->cr_uid));
 retry:
 	err = 0;
+	/* Default timeout is 15s unless we know that gssd is not running */
+	timeout = 15 * HZ;
+	if (!sn->gssd_running)
+		timeout = HZ >> 2;
 	gss_msg = gss_setup_upcall(gss_auth->client, gss_auth, cred);
 	if (PTR_ERR(gss_msg) == -EAGAIN) {
 		err = wait_event_interruptible_timeout(pipe_version_waitqueue,
-				pipe_version >= 0, 15*HZ);
+				pipe_version >= 0, timeout);
 		if (pipe_version < 0) {
+			if (err == 0)
+				sn->gssd_running = 0;
 			warn_gssd();
 			err = -EACCES;
 		}

net/sunrpc/netns.h

···
 	struct rpc_clnt *gssp_clnt;
 	int use_gss_proxy;
 	struct proc_dir_entry *use_gssp_proc;
+
+	unsigned int gssd_running;
 };
 
 extern int sunrpc_net_id;

net/sunrpc/rpc_pipe.c

···
 static int
 rpc_pipe_open(struct inode *inode, struct file *filp)
 {
+	struct net *net = inode->i_sb->s_fs_info;
+	struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
 	struct rpc_pipe *pipe;
 	int first_open;
 	int res = -ENXIO;
 
 	mutex_lock(&inode->i_mutex);
+	sn->gssd_running = 1;
 	pipe = RPC_I(inode)->pipe;
 	if (pipe == NULL)
 		goto out;
···
 	struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
 
 	mutex_init(&sn->pipefs_sb_lock);
+	sn->gssd_running = 1;
 }
 
 /*