From: David Teigland <teigland@redhat.com>
Subject: [RHEL5.1 PATCH] dlm: misc device removed when lockspace removal fails
Date: Thu, 31 May 2007 09:36:41 -0500
Bugzilla: 241817
Message-Id: <20070531143641.GI2642@redhat.com>
Changelog: [dlm] misc device removed when lockspace removal fails


bz 241817

Currently if the lockspace removal fails the misc device associated with a
lockspace is left deleted. After that there is no way to access the orphaned
lockspace from userland.

This patch recreates the misc device if th dlm_release_lockspace fails. I
believe this is better than attempting to remove the lockspace first because
that leaves an unattached device lying around. The potential gap in which there
is no access to the lockspace between removing the misc device and recreating it
is acceptable ... after all the application is trying to remove it, and only new
users of the lockspace will be affected.

Also, to sync with upstream, add const to file_operations and include user.h.

upstream: gfs2-2.6-nmw.git and -mm

Index: linux-rhel51-quilt/fs/dlm/user.c
===================================================================
--- linux-rhel51-quilt.orig/fs/dlm/user.c	2007-06-08 10:18:13.000000000 -0500
+++ linux-rhel51-quilt/fs/dlm/user.c	2007-06-08 10:21:21.000000000 -0500
@@ -22,10 +22,11 @@
 #include "lockspace.h"
 #include "lock.h"
 #include "lvb_table.h"
+#include "user.h"
 
 static const char *name_prefix="dlm";
 static struct miscdevice ctl_device;
-static struct file_operations device_fops;
+static const struct file_operations device_fops;
 
 #ifdef CONFIG_COMPAT
 
@@ -336,6 +337,29 @@
 	return error;
 }
 
+static int create_misc_device(struct dlm_ls *ls, char *name)
+{
+	int error, len;
+
+	error = -ENOMEM;
+	len = strlen(name) + strlen(name_prefix) + 2;
+	ls->ls_device.name = kzalloc(len, GFP_KERNEL);
+	if (!ls->ls_device.name)
+		goto fail;
+
+	snprintf((char *)ls->ls_device.name, len, "%s_%s", name_prefix,
+		 name);
+	ls->ls_device.fops = &device_fops;
+	ls->ls_device.minor = MISC_DYNAMIC_MINOR;
+
+	error = misc_register(&ls->ls_device);
+	if (error) {
+		kfree(ls->ls_device.name);
+	}
+fail:
+	return error;
+}
+
 static int device_user_purge(struct dlm_user_proc *proc,
 			     struct dlm_purge_params *params)
 {
@@ -356,7 +380,7 @@
 {
 	dlm_lockspace_t *lockspace;
 	struct dlm_ls *ls;
-	int error, len;
+	int error;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
@@ -370,29 +394,14 @@
 	if (!ls)
 		return -ENOENT;
 
-	error = -ENOMEM;
-	len = strlen(params->name) + strlen(name_prefix) + 2;
-	ls->ls_device.name = kzalloc(len, GFP_KERNEL);
-	if (!ls->ls_device.name)
-		goto fail;
-	snprintf((char *)ls->ls_device.name, len, "%s_%s", name_prefix,
-		 params->name);
-	ls->ls_device.fops = &device_fops;
-	ls->ls_device.minor = MISC_DYNAMIC_MINOR;
-
-	error = misc_register(&ls->ls_device);
-	if (error) {
-		kfree(ls->ls_device.name);
-		goto fail;
-	}
-
-	error = ls->ls_device.minor;
+	error = create_misc_device(ls, params->name);
 	dlm_put_lockspace(ls);
-	return error;
 
- fail:
-	dlm_put_lockspace(ls);
-	dlm_release_lockspace(lockspace, 0);
+	if (error)
+		dlm_release_lockspace(lockspace, 0);
+	else
+		error = ls->ls_device.minor;
+
 	return error;
 }
 
@@ -409,6 +418,10 @@
 	if (!ls)
 		return -ENOENT;
 
+	/* Deregister the misc device first, so we don't have
+	 * a device that's not attached to a lockspace. If
+	 * dlm_release_lockspace fails then we can recreate it
+	 */
 	error = misc_deregister(&ls->ls_device);
 	if (error) {
 		dlm_put_lockspace(ls);
@@ -427,6 +440,8 @@
 
 	dlm_put_lockspace(ls);
 	error = dlm_release_lockspace(lockspace, force);
+	if (error)
+		create_misc_device(ls, ls->ls_name);
  out:
 	return error;
 }
@@ -864,7 +879,7 @@
 	return 0;
 }
 
-static struct file_operations device_fops = {
+static const struct file_operations device_fops = {
 	.open    = device_open,
 	.release = device_close,
 	.read    = device_read,
@@ -873,7 +888,7 @@
 	.owner   = THIS_MODULE,
 };
 
-static struct file_operations ctl_device_fops = {
+static const struct file_operations ctl_device_fops = {
 	.open    = ctl_device_open,
 	.release = ctl_device_close,
 	.read    = device_read,