NSM: Add nsm_lookup() function

Introduce a new API to fs/lockd/mon.c that allows nlm_host_rebooted()
to lookup up nsm_handles via the contents of an nlm_reboot struct.

The new function is equivalent to calling nsm_find() with @create set
to zero, but it takes a struct nlm_reboot instead of separate
arguments.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

2 files changed, 65 insertions, 0 deletions

diff --git a/fs/lockd/mon.c b/fs/lockd/mon.c
index 4424b0a5a51f..e46903995c99 100644
--- a/fs/lockd/mon.c
+++ b/fs/lockd/mon.c
@@ -201,6 +201,29 @@ void nsm_unmonitor(const struct nlm_host *host)
         }
 }
 
+static struct nsm_handle *nsm_lookup_hostname(const char *hostname,
+                                              const size_t len)
+{
+        struct nsm_handle *nsm;
+
+        list_for_each_entry(nsm, &nsm_handles, sm_link)
+                if (strlen(nsm->sm_name) == len &&
+                    memcmp(nsm->sm_name, hostname, len) == 0)
+                        return nsm;
+        return NULL;
+}
+
+static struct nsm_handle *nsm_lookup_priv(const struct nsm_private *priv)
+{
+        struct nsm_handle *nsm;
+
+        list_for_each_entry(nsm, &nsm_handles, sm_link)
+                if (memcmp(nsm->sm_priv.data, priv->data,
+                                        sizeof(priv->data)) == 0)
+                        return nsm;
+        return NULL;
+}
+
 /*
  * Construct a unique cookie to match this nsm_handle to this monitored
  * host.  It is passed to the local rpc.statd via NSMPROC_MON, and
@@ -298,6 +321,47 @@ found:
 }
 
 /**
+ * nsm_reboot_lookup - match NLMPROC_SM_NOTIFY arguments to an nsm_handle
+ * @info: pointer to NLMPROC_SM_NOTIFY arguments
+ *
+ * Returns a matching nsm_handle if found in the nsm cache; the returned
+ * nsm_handle's reference count is bumped and sm_monitored is cleared.
+ * Otherwise returns NULL if some error occurred.
+ */
+struct nsm_handle *nsm_reboot_lookup(const struct nlm_reboot *info)
+{
+        struct nsm_handle *cached;
+
+        spin_lock(&nsm_lock);
+
+        if (nsm_use_hostnames && info->mon != NULL)
+                cached = nsm_lookup_hostname(info->mon, info->len);
+        else
+                cached = nsm_lookup_priv(&info->priv);
+
+        if (unlikely(cached == NULL)) {
+                spin_unlock(&nsm_lock);
+                dprintk("lockd: never saw rebooted peer '%.*s' before\n",
+                                info->len, info->mon);
+                return cached;
+        }
+
+        atomic_inc(&cached->sm_count);
+        spin_unlock(&nsm_lock);
+
+        /*
+         * During subsequent lock activity, force a fresh
+         * notification to be set up for this host.
+         */
+        cached->sm_monitored = 0;
+
+        dprintk("lockd: host %s (%s) rebooted, cnt %d\n",
+                        cached->sm_name, cached->sm_addrbuf,
+                        atomic_read(&cached->sm_count));
+        return cached;
+}
+
+/**
  * nsm_release - Release an NSM handle
  * @nsm: pointer to handle to be released
  *
diff --git a/include/linux/lockd/lockd.h b/include/linux/lockd/lockd.h
index 2a3533ea38dd..5e3ad926de89 100644
--- a/include/linux/lockd/lockd.h
+++ b/include/linux/lockd/lockd.h
@@ -251,6 +251,7 @@ struct nsm_handle *nsm_find(const struct sockaddr *sap, const size_t salen,
                                         const char *hostname,
                                         const size_t hostname_len,
                                         const int create);
+struct nsm_handle *nsm_reboot_lookup(const struct nlm_reboot *info);
 void              nsm_release(struct nsm_handle *nsm);
 
 /*