[GFS2] Add gfs2_tool lockdump support to gfs2 (bz 228540)

The attached patch resolves bz 228540.  This adds the capability
for gfs2 to dump gfs2 locks through the debugfs file system.
This used to exist in gfs1 as "gfs_tool lockdump" but it's missing from
gfs2 because all the ioctls were stripped out.  Please see the bugzilla
for more history about the fix.  This patch is also attached to the bugzilla
record.

The patch is against Steve Whitehouse's latest nmw git tree kernel
(2.6.21-rc1) and has been tested on system trin-10.
Signed-off-by: Robert Peterson <rpeterso@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

fs/gfs2/glock.h

@@ -135,5 +135,9 @@ void gfs2_scand_internal(struct gfs2_sbd *sdp);
 void gfs2_gl_hash_clear(struct gfs2_sbd *sdp, int wait);
 
 int __init gfs2_glock_init(void);
+int gfs2_create_debugfs_file(struct gfs2_sbd *sdp);
+void gfs2_delete_debugfs_file(struct gfs2_sbd *sdp);
+int gfs2_register_debugfs(void);
+void gfs2_unregister_debugfs(void);
 
 #endif /* __GLOCK_DOT_H__ */

fs/gfs2/incore.h

@@ -611,6 +611,7 @@ struct gfs2_sbd {
 
 	unsigned long sd_last_warning;
 	struct vfsmount *sd_gfs2mnt;
+	struct dentry *debugfs_dentry; /* for debugfs */
 };
 
 #endif /* __INCORE_DOT_H__ */

fs/gfs2/main.c

@@ -103,6 +103,8 @@ static int __init init_gfs2_fs(void)
 	if (error)
 		goto fail_unregister;
 
+	gfs2_register_debugfs();
+
 	printk("GFS2 (built %s %s) installed\n", __DATE__, __TIME__);
 
 	return 0;
@@ -130,6 +132,7 @@ static int __init init_gfs2_fs(void)
 
 static void __exit exit_gfs2_fs(void)
 {
+	gfs2_unregister_debugfs();
 	unregister_filesystem(&gfs2_fs_type);
 	unregister_filesystem(&gfs2meta_fs_type);
 

fs/gfs2/ops_fstype.c

@@ -690,6 +690,8 @@ static int fill_super(struct super_block *sb, void *data, int silent)
 	if (error)
 		goto fail;
 
+	gfs2_create_debugfs_file(sdp);
+
 	error = gfs2_sys_fs_add(sdp);
 	if (error)
 		goto fail;
@@ -896,6 +898,7 @@ static int gfs2_get_sb_meta(struct file_system_type *fs_type, int flags,
 
 static void gfs2_kill_sb(struct super_block *sb)
 {
+	gfs2_delete_debugfs_file(sb->s_fs_info);
 	kill_block_super(sb);
 }