ocfs2/cluster: Make fence method configurable - v2

By default, o2cb fences the box by calling emergency_restart(). While this
scheme works well in production, it comes in the way during testing as it
does not let the tester take stack/core dumps for analysis.

This patch allows user to dynamically change the fence method to panic() by:
# echo "panic" > /sys/kernel/config/cluster/<clustername>/fence_method

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>

3 files changed, 72 insertions, 2 deletions

diff --git a/fs/ocfs2/cluster/nodemanager.c b/fs/ocfs2/cluster/nodemanager.c
index 7ee6188bc79a..c81142e3ef84 100644
--- a/fs/ocfs2/cluster/nodemanager.c
+++ b/fs/ocfs2/cluster/nodemanager.c
@@ -35,6 +35,10 @@
  * cluster references throughout where nodes are looked up */
 struct o2nm_cluster *o2nm_single_cluster = NULL;
 
+char *o2nm_fence_method_desc[O2NM_FENCE_METHODS] = {
+                "reset",        /* O2NM_FENCE_RESET */
+                "panic",        /* O2NM_FENCE_PANIC */
+};
 
 struct o2nm_node *o2nm_get_node_by_num(u8 node_num)
 {
@@ -579,6 +583,43 @@ static ssize_t o2nm_cluster_attr_reconnect_delay_ms_write(
         return o2nm_cluster_attr_write(page, count,
                                        &cluster->cl_reconnect_delay_ms);
 }
+
+static ssize_t o2nm_cluster_attr_fence_method_read(
+        struct o2nm_cluster *cluster, char *page)
+{
+        ssize_t ret = 0;
+
+        if (cluster)
+                ret = sprintf(page, "%s\n",
+                              o2nm_fence_method_desc[cluster->cl_fence_method]);
+        return ret;
+}
+
+static ssize_t o2nm_cluster_attr_fence_method_write(
+        struct o2nm_cluster *cluster, const char *page, size_t count)
+{
+        unsigned int i;
+
+        if (page[count - 1] != '\n')
+                goto bail;
+
+        for (i = 0; i < O2NM_FENCE_METHODS; ++i) {
+                if (count != strlen(o2nm_fence_method_desc[i]) + 1)
+                        continue;
+                if (strncasecmp(page, o2nm_fence_method_desc[i], count - 1))
+                        continue;
+                if (cluster->cl_fence_method != i) {
+                        printk(KERN_INFO "ocfs2: Changing fence method to %s\n",
+                               o2nm_fence_method_desc[i]);
+                        cluster->cl_fence_method = i;
+                }
+                return count;
+        }
+
+bail:
+        return -EINVAL;
+}
+
 static struct o2nm_cluster_attribute o2nm_cluster_attr_idle_timeout_ms = {
         .attr   = { .ca_owner = THIS_MODULE,
                     .ca_name = "idle_timeout_ms",
@@ -603,10 +644,19 @@ static struct o2nm_cluster_attribute o2nm_cluster_attr_reconnect_delay_ms = {
         .store  = o2nm_cluster_attr_reconnect_delay_ms_write,
 };
 
+static struct o2nm_cluster_attribute o2nm_cluster_attr_fence_method = {
+        .attr   = { .ca_owner = THIS_MODULE,
+                    .ca_name = "fence_method",
+                    .ca_mode = S_IRUGO | S_IWUSR },
+        .show   = o2nm_cluster_attr_fence_method_read,
+        .store  = o2nm_cluster_attr_fence_method_write,
+};
+
 static struct configfs_attribute *o2nm_cluster_attrs[] = {
         &o2nm_cluster_attr_idle_timeout_ms.attr,
         &o2nm_cluster_attr_keepalive_delay_ms.attr,
         &o2nm_cluster_attr_reconnect_delay_ms.attr,
+        &o2nm_cluster_attr_fence_method.attr,
         NULL,
 };
 static ssize_t o2nm_cluster_show(struct config_item *item,
@@ -778,6 +828,7 @@ static struct config_group *o2nm_cluster_group_make_group(struct config_group *g
         cluster->cl_reconnect_delay_ms = O2NET_RECONNECT_DELAY_MS_DEFAULT;
         cluster->cl_idle_timeout_ms    = O2NET_IDLE_TIMEOUT_MS_DEFAULT;
         cluster->cl_keepalive_delay_ms = O2NET_KEEPALIVE_DELAY_MS_DEFAULT;
+        cluster->cl_fence_method       = O2NM_FENCE_RESET;
 
         ret = &cluster->cl_group;
         o2nm_single_cluster = cluster;
diff --git a/fs/ocfs2/cluster/nodemanager.h b/fs/ocfs2/cluster/nodemanager.h
index c992ea0da4ad..09ea2d388bbb 100644
--- a/fs/ocfs2/cluster/nodemanager.h
+++ b/fs/ocfs2/cluster/nodemanager.h
@@ -33,6 +33,12 @@
 #include <linux/configfs.h>
 #include <linux/rbtree.h>
 
+enum o2nm_fence_method {
+        O2NM_FENCE_RESET        = 0,
+        O2NM_FENCE_PANIC,
+        O2NM_FENCE_METHODS,     /* Number of fence methods */
+};
+
 struct o2nm_node {
         spinlock_t              nd_lock;
         struct config_item      nd_item;
@@ -58,6 +64,7 @@ struct o2nm_cluster {
         unsigned int            cl_idle_timeout_ms;
         unsigned int            cl_keepalive_delay_ms;
         unsigned int            cl_reconnect_delay_ms;
+        enum o2nm_fence_method  cl_fence_method;
 
         /* this bitmap is part of a hack for disk bitmap.. will go eventually. - zab */
         unsigned long   cl_nodes_bitmap[BITS_TO_LONGS(O2NM_MAX_NODES)];
diff --git a/fs/ocfs2/cluster/quorum.c b/fs/ocfs2/cluster/quorum.c
index bbacf7da48a4..639024033fce 100644
--- a/fs/ocfs2/cluster/quorum.c
+++ b/fs/ocfs2/cluster/quorum.c
@@ -74,8 +74,20 @@ static void o2quo_fence_self(void)
          * threads can still schedule, etc, etc */
         o2hb_stop_all_regions();
 
-        printk("ocfs2 is very sorry to be fencing this system by restarting\n");
-        emergency_restart();
+        switch (o2nm_single_cluster->cl_fence_method) {
+        case O2NM_FENCE_PANIC:
+                panic("*** ocfs2 is very sorry to be fencing this system by "
+                      "panicing ***\n");
+                break;
+        default:
+                WARN_ON(o2nm_single_cluster->cl_fence_method >=
+                        O2NM_FENCE_METHODS);
+        case O2NM_FENCE_RESET:
+                printk(KERN_ERR "*** ocfs2 is very sorry to be fencing this "
+                       "system by restarting ***\n");
+                emergency_restart();
+                break;
+        };
 }
 
 /* Indicate that a timeout occured on a hearbeat region write. The