ocfs2: Add the ocfs2_control misc device.
Joel Becker [Tue, 19 Feb 2008 03:23:28 +0000 (19:23 -0800)]
The ocfs2_control misc device is how a userspace control daemon (controld)
talks to the filesystem.  Introduce the bare-bones filesystem ops.

Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>

fs/ocfs2/stack_user.c

index 920eb11..fdca5d3 100644 (file)
  */
 
 #include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/miscdevice.h>
+#include <linux/mutex.h>
+#include <linux/reboot.h>
 
 #include "stackglue.h"
 
 
-static int __init user_stack_init(void)
+/*
+ * The control protocol starts with a handshake.  Until the handshake
+ * is complete, the control device will fail all write(2)s.
+ *
+ * The handshake is simple.  First, the client reads until EOF.  Each line
+ * of output is a supported protocol tag.  All protocol tags are a single
+ * character followed by a two hex digit version number.  Currently the
+ * only things supported is T01, for "Text-base version 0x01".  Next, the
+ * client writes the version they would like to use.  If the version tag
+ * written is unknown, -EINVAL is returned.  Once the negotiation is
+ * complete, the client can start sending messages.
+ */
+
+/*
+ * ocfs2_live_connection is refcounted because the filesystem and
+ * miscdevice sides can detach in different order.  Let's just be safe.
+ */
+struct ocfs2_live_connection {
+       struct list_head                oc_list;
+       struct ocfs2_cluster_connection *oc_conn;
+};
+
+static atomic_t ocfs2_control_opened;
+
+static LIST_HEAD(ocfs2_live_connection_list);
+static DEFINE_MUTEX(ocfs2_control_lock);
+
+static struct ocfs2_live_connection *ocfs2_connection_find(const char *name)
+{
+       size_t len = strlen(name);
+       struct ocfs2_live_connection *c;
+
+       BUG_ON(!mutex_is_locked(&ocfs2_control_lock));
+
+       list_for_each_entry(c, &ocfs2_live_connection_list, oc_list) {
+               if ((c->oc_conn->cc_namelen == len) &&
+                   !strncmp(c->oc_conn->cc_name, name, len))
+                       return c;
+       }
+
+       return c;
+}
+
+/*
+ * ocfs2_live_connection structures are created underneath the ocfs2
+ * mount path.  Since the VFS prevents multiple calls to
+ * fill_super(), we can't get dupes here.
+ */
+static int ocfs2_live_connection_new(struct ocfs2_cluster_connection *conn,
+                                    struct ocfs2_live_connection **c_ret)
+{
+       int rc = 0;
+       struct ocfs2_live_connection *c;
+
+       c = kzalloc(sizeof(struct ocfs2_live_connection), GFP_KERNEL);
+       if (!c)
+               return -ENOMEM;
+
+       mutex_lock(&ocfs2_control_lock);
+       c->oc_conn = conn;
+
+       if (atomic_read(&ocfs2_control_opened))
+               list_add(&c->oc_list, &ocfs2_live_connection_list);
+       else {
+               printk(KERN_ERR
+                      "ocfs2: Userspace control daemon is not present\n");
+               rc = -ESRCH;
+       }
+
+       mutex_unlock(&ocfs2_control_lock);
+
+       if (!rc)
+               *c_ret = c;
+       else
+               kfree(c);
+
+       return rc;
+}
+
+/*
+ * This function disconnects the cluster connection from ocfs2_control.
+ * Afterwards, userspace can't affect the cluster connection.
+ */
+static void ocfs2_live_connection_drop(struct ocfs2_live_connection *c)
+{
+       mutex_lock(&ocfs2_control_lock);
+       list_del_init(&c->oc_list);
+       c->oc_conn = NULL;
+       mutex_unlock(&ocfs2_control_lock);
+
+       kfree(c);
+}
+
+
+static ssize_t ocfs2_control_write(struct file *file,
+                                  const char __user *buf,
+                                  size_t count,
+                                  loff_t *ppos)
 {
        return 0;
 }
 
+static ssize_t ocfs2_control_read(struct file *file,
+                                 char __user *buf,
+                                 size_t count,
+                                 loff_t *ppos)
+{
+       return 0;
+}
+
+static int ocfs2_control_release(struct inode *inode, struct file *file)
+{
+       if (atomic_dec_and_test(&ocfs2_control_opened)) {
+               mutex_lock(&ocfs2_control_lock);
+               if (!list_empty(&ocfs2_live_connection_list)) {
+                       /* XXX: Do bad things! */
+                       printk(KERN_ERR
+                              "ocfs2: Unexpected release of ocfs2_control!\n"
+                              "       Loss of cluster connection requires "
+                              "an emergency restart!\n");
+                       emergency_restart();
+               }
+               mutex_unlock(&ocfs2_control_lock);
+       }
+
+       return 0;
+}
+
+static int ocfs2_control_open(struct inode *inode, struct file *file)
+{
+       atomic_inc(&ocfs2_control_opened);
+
+       return 0;
+}
+
+static const struct file_operations ocfs2_control_fops = {
+       .open    = ocfs2_control_open,
+       .release = ocfs2_control_release,
+       .read    = ocfs2_control_read,
+       .write   = ocfs2_control_write,
+       .owner   = THIS_MODULE,
+};
+
+struct miscdevice ocfs2_control_device = {
+       .minor          = MISC_DYNAMIC_MINOR,
+       .name           = "ocfs2_control",
+       .fops           = &ocfs2_control_fops,
+};
+
+static int ocfs2_control_init(void)
+{
+       int rc;
+
+       atomic_set(&ocfs2_control_opened, 0);
+
+       rc = misc_register(&ocfs2_control_device);
+       if (rc)
+               printk(KERN_ERR
+                      "ocfs2: Unable to register ocfs2_control device "
+                      "(errno %d)\n",
+                      -rc);
+
+       return rc;
+}
+
+static void ocfs2_control_exit(void)
+{
+       int rc;
+
+       rc = misc_deregister(&ocfs2_control_device);
+       if (rc)
+               printk(KERN_ERR
+                      "ocfs2: Unable to deregister ocfs2_control device "
+                      "(errno %d)\n",
+                      -rc);
+}
+
+static int __init user_stack_init(void)
+{
+       return ocfs2_control_init();
+}
+
 static void __exit user_stack_exit(void)
 {
+       ocfs2_control_exit();
 }
 
 MODULE_AUTHOR("Oracle");