Server backend storage hang should not cause the mount point to hang.

Submitted-by: Krishna Srinivas <krishna@gluster.com>
NOTE: fixed compilation issues in posix.c introduced while merging

storage/posix polls for FS/kernel being functional by issuing
statvfs() call. In case statvfs expires the timer, storage/posix will
send CHILD_DOWN to upper translator. Ultimately this will cause
protocol/server to disconnect all clients connected and also cleans up
the data structures. Hence if soft lockup or other kernel bug causes
backend FS to hang, the clients will not be hung.

Signed-off-by: Krishna Srinivas <krishna@gluster.com>
Signed-off-by: Anand V. Avati <avati@blackhole.gluster.com>
Signed-off-by: Anand V. Avati <avati@dev.gluster.com>

BUG: 272 (Server backend storage hang should not cause the mount point to hang)
URL: http://bugs.gluster.com/cgi-bin/bugzilla3/show_bug.cgi?id=272

1 files changed, 110 insertions, 2 deletions

diff --git a/xlators/protocol/server/src/server-helpers.c b/xlators/protocol/server/src/server-helpers.c
index 88dada1516e..0e22f0ba5fa 100644
--- a/xlators/protocol/server/src/server-helpers.c
+++ b/xlators/protocol/server/src/server-helpers.c
@@ -645,13 +645,14 @@ out:
 
 
 int
-server_connection_cleanup (xlator_t *this, server_connection_t *conn)
+server_connection_cleanup (xlator_t *this, server_connection_t *conn, transport_t *trans)
 {
         char                do_cleanup = 0;
 	struct _lock_table *ltable = NULL;
         fdentry_t          *fdentries = NULL;
         uint32_t            fd_count = 0;
         int                 ret = 0; 
+        int                 i = 0;
 
         if (conn == NULL) {
                 goto out;
@@ -659,6 +660,12 @@ server_connection_cleanup (xlator_t *this, server_connection_t *conn)
 
         pthread_mutex_lock (&conn->lock);
         {
+                for (i = 0; i < TRANSPORTS_PER_SERVER_CONN; i++) {
+                        if (conn->transports[i] == trans) {
+                                conn->transports[i] = NULL;
+                                transport_unref (trans);
+                        }
+                }
                 conn->active_transports--;
                 if (conn->active_transports == 0) {
 			if (conn->ltable) {
@@ -850,11 +857,12 @@ out:
 
 
 server_connection_t *
-server_connection_get (xlator_t *this, const char *id)
+server_connection_get (xlator_t *this, const char *id, transport_t *trans)
 {
 	server_connection_t *conn = NULL;
 	server_connection_t *trav = NULL;
 	server_conf_t       *conf = NULL;
+        int                  i = 0;
 
 	conf = this->private;
 
@@ -878,10 +886,30 @@ server_connection_get (xlator_t *this, const char *id)
 
 			list_add (&conn->list, &conf->conns);
 		}
+                if (conn->active_transports == TRANSPORTS_PER_SERVER_CONN) {
+                        gf_log (this->name, GF_LOG_DEBUG,
+                                "Maximum number of connections allowed is %d",
+                                TRANSPORTS_PER_SERVER_CONN);
+                        goto unlock;
+                }
+
+                for (i = 0; i < TRANSPORTS_PER_SERVER_CONN; i++) {
+                        if (!conn->transports[i])
+                                break;
+                }
+
+                if (i == TRANSPORTS_PER_SERVER_CONN) {
+                        gf_log (this->name, GF_LOG_DEBUG,
+                                "Could not find a vacant slot");
+                        goto unlock;
+                }
+
+                conn->transports[i] = transport_ref (trans);
 
 		conn->ref++;
                 conn->active_transports++;
 	}
+unlock:
 	pthread_mutex_unlock (&conf->mutex);
 
 	return conn;
@@ -918,3 +946,83 @@ server_connection_put (xlator_t *this, server_connection_t *conn)
 out:
 	return;
 }
+
+void
+server_child_down (xlator_t *this, xlator_t *bound_xl)
+{
+        server_conf_t       *conf = NULL;
+        server_connection_t *trav = NULL;
+        transport_t         *trans = NULL;
+        int                  subvol_idx = 0;
+        int                  i = 0;
+        xlator_list_t       *xltrav = NULL;
+
+        conf = this->private;
+
+        if (conf == NULL)
+                return;
+
+        xltrav = this->children;
+
+        while (xltrav) {
+                if (xltrav->xlator == bound_xl)
+                        break;
+                xltrav = xltrav->next;
+                subvol_idx++;
+	}
+        gf_log (this->name, GF_LOG_DEBUG,
+                "subvolume %s(%d) went down", bound_xl->name, subvol_idx);
+
+        conf->subvol_list[subvol_idx] = 0;
+
+        pthread_mutex_lock (&conf->mutex);
+        {
+        if (!list_empty(&conf->conns)) {
+                list_for_each_entry (trav, &conf->conns, list) {
+                        if (bound_xl == trav->bound_xl) {
+                                gf_log (this->name, GF_LOG_DEBUG,
+                                        "disonnecting conn=%p", trav);
+                                for (i = 0; i < TRANSPORTS_PER_SERVER_CONN; i++)
+                                {
+                                        trans = trav->transports[i];
+                                        if (trans == NULL)
+                                                continue;
+                                        gf_log (this->name, GF_LOG_DEBUG,
+                                                "disconnecting %p(%d)", 
+                                                trans, i);
+                                        transport_disconnect (trans);
+                                }
+                        }
+                }
+        }
+        }
+        pthread_mutex_unlock (&conf->mutex);
+}
+
+void
+server_child_up (xlator_t *this, xlator_t *bound_xl)
+{
+	server_conf_t       *conf = NULL;
+	int                  subvol_idx = 0;
+	xlator_list_t       *xltrav = NULL;
+
+	conf = this->private;
+
+	if (conf == NULL)
+		return;
+
+	xltrav = this->children;
+
+	while (xltrav) {
+		if (bound_xl == xltrav->xlator) {
+			break;
+		}
+		subvol_idx++;
+                xltrav = xltrav->next;
+	}
+
+        gf_log (this->name, GF_LOG_DEBUG,
+                "subvolume %s(%d) came up", bound_xl->name, subvol_idx);
+
+        conf->subvol_list[subvol_idx] = 1;
+}