[PATCH] Break the kobject namespace defs into their own header

[PATCH] Break the kobject namespace defs into their own header

[David Howells]

Break the kobject namespace defs into their own header to avoid a header file
inclusion ordering problem between linux/sysfs.h and linux/kobject.h.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 include/linux/kobject.h    |   35 +---------------------------
 include/linux/kobject_ns.h |   56 ++++++++++++++++++++++++++++++++++++++++++++
 include/linux/sysfs.h      |    1 +
 3 files changed, 58 insertions(+), 34 deletions(-)
 create mode 100644 include/linux/kobject_ns.h


diff --git a/include/linux/kobject.h b/include/linux/kobject.h
index cf343a8..7950a37 100644
--- a/include/linux/kobject.h
+++ b/include/linux/kobject.h
@@ -22,6 +22,7 @@
 #include <linux/compiler.h>
 #include <linux/spinlock.h>
 #include <linux/kref.h>
+#include <linux/kobject_ns.h>
 #include <linux/kernel.h>
 #include <linux/wait.h>
 #include <asm/atomic.h>
@@ -136,42 +137,8 @@ struct kobj_attribute {
 
 extern const struct sysfs_ops kobj_sysfs_ops;
 
-/*
- * Namespace types which are used to tag kobjects and sysfs entries.
- * Network namespace will likely be the first.
- */
-enum kobj_ns_type {
-	KOBJ_NS_TYPE_NONE = 0,
-	KOBJ_NS_TYPE_NET,
-	KOBJ_NS_TYPES
-};
-
 struct sock;
 
-/*
- * Callbacks so sysfs can determine namespaces
- *   @current_ns: return calling task's namespace
- *   @netlink_ns: return namespace to which a sock belongs (right?)
- *   @initial_ns: return the initial namespace (i.e. init_net_ns)
- */
-struct kobj_ns_type_operations {
-	enum kobj_ns_type type;
-	const void *(*current_ns)(void);
-	const void *(*netlink_ns)(struct sock *sk);
-	const void *(*initial_ns)(void);
-};
-
-int kobj_ns_type_register(const struct kobj_ns_type_operations *ops);
-int kobj_ns_type_registered(enum kobj_ns_type type);
-const struct kobj_ns_type_operations *kobj_child_ns_ops(struct kobject *parent);
-const struct kobj_ns_type_operations *kobj_ns_ops(struct kobject *kobj);
-
-const void *kobj_ns_current(enum kobj_ns_type type);
-const void *kobj_ns_netlink(enum kobj_ns_type type, struct sock *sk);
-const void *kobj_ns_initial(enum kobj_ns_type type);
-void kobj_ns_exit(enum kobj_ns_type type, const void *ns);
-
-
 /**
  * struct kset - a set of kobjects of a specific type, belonging to a specific subsystem.
  *
diff --git a/include/linux/kobject_ns.h b/include/linux/kobject_ns.h
new file mode 100644
index 0000000..82cb5bf
--- /dev/null
+++ b/include/linux/kobject_ns.h
@@ -0,0 +1,56 @@
+/* Kernel object name space definitions
+ *
+ * Copyright (c) 2002-2003 Patrick Mochel
+ * Copyright (c) 2002-2003 Open Source Development Labs
+ * Copyright (c) 2006-2008 Greg Kroah-Hartman <greg@kroah.com>
+ * Copyright (c) 2006-2008 Novell Inc.
+ *
+ * Split from kobject.h by David Howells (dhowells@redhat.com)
+ *
+ * This file is released under the GPLv2.
+ *
+ * Please read Documentation/kobject.txt before using the kobject
+ * interface, ESPECIALLY the parts about reference counts and object
+ * destructors.
+ */
+
+#ifndef _LINUX_KOBJECT_NS_H
+#define _LINUX_KOBJECT_NS_H
+
+struct sock;
+struct kobject;
+
+/*
+ * Namespace types which are used to tag kobjects and sysfs entries.
+ * Network namespace will likely be the first.
+ */
+enum kobj_ns_type {
+	KOBJ_NS_TYPE_NONE = 0,
+	KOBJ_NS_TYPE_NET,
+	KOBJ_NS_TYPES
+};
+
+/*
+ * Callbacks so sysfs can determine namespaces
+ *   @current_ns: return calling task's namespace
+ *   @netlink_ns: return namespace to which a sock belongs (right?)
+ *   @initial_ns: return the initial namespace (i.e. init_net_ns)
+ */
+struct kobj_ns_type_operations {
+	enum kobj_ns_type type;
+	const void *(*current_ns)(void);
+	const void *(*netlink_ns)(struct sock *sk);
+	const void *(*initial_ns)(void);
+};
+
+int kobj_ns_type_register(const struct kobj_ns_type_operations *ops);
+int kobj_ns_type_registered(enum kobj_ns_type type);
+const struct kobj_ns_type_operations *kobj_child_ns_ops(struct kobject *parent);
+const struct kobj_ns_type_operations *kobj_ns_ops(struct kobject *kobj);
+
+const void *kobj_ns_current(enum kobj_ns_type type);
+const void *kobj_ns_netlink(enum kobj_ns_type type, struct sock *sk);
+const void *kobj_ns_initial(enum kobj_ns_type type);
+void kobj_ns_exit(enum kobj_ns_type type, const void *ns);
+
+#endif /* _LINUX_KOBJECT_NS_H */
diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
index 3c92121..96eb576 100644
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -16,6 +16,7 @@
 #include <linux/errno.h>
 #include <linux/list.h>
 #include <linux/lockdep.h>
+#include <linux/kobject_ns.h>
 #include <asm/atomic.h>
 
 struct kobject;

Re: [PATCH] Break the kobject namespace defs into their own header

[Greg KH]

On Wed, Aug 11, 2010 at 03:01:02PM +0100, David Howells wrote:
> Break the kobject namespace defs into their own header to avoid a header file
> inclusion ordering problem between linux/sysfs.h and linux/kobject.h.

What "ordering problem" is there?  I don't see a build error here, do
you?

thanks,

greg k-h

Re: [PATCH] Break the kobject namespace defs into their own header

[David Howells]

Greg KH <gregkh@suse.de> wrote:

> What "ordering problem" is there?  I don't see a build error here, do
> you?

Yes:

  CC      arch/mn10300/kernel/asm-offsets.s
In file included from include/linux/kobject.h:21,
                 from include/linux/sched.h:91,
                 from arch/mn10300/kernel/asm-offsets.c:7:
include/linux/sysfs.h:177: warning: parameter 1 ('type') has incomplete type
  GEN     include/generated/asm-offsets.h
  CALL    scripts/checksyscalls.sh
<stdin>:1526:2: warning: #warning syscall fanotify_init not implemented
<stdin>:1530:2: warning: #warning syscall fanotify_mark not implemented
<stdin>:1534:2: warning: #warning syscall prlimit64 not implemented
  CC      init/main.o
  CC      arch/mn10300/mm/init.o
  CC      arch/mn10300/kernel/process.o
In file included from include/linux/kobject.h:21,
                 from include/linux/sched.h:91,
                 from include/linux/utsname.h:35,
                 from /warthog/am33/linux-2.6-mn10300/arch/mn10300/include/asm/elf.h:15,
                 from include/linux/elf.h:7,
                 from include/linux/module.h:14,
                 from init/main.c:13:
include/linux/sysfs.h:177: warning: parameter 1 ('type') has incomplete type
In file included from include/linux/kobject.h:21,
                 from include/linux/sched.h:91,
                 from arch/mn10300/mm/init.c:13:
include/linux/sysfs.h:177: warning: parameter 1 ('type') has incomplete type
In file included from include/linux/kobject.h:21,
                 from include/linux/sched.h:91,
                 from include/linux/utsname.h:35,
                 from /warthog/am33/linux-2.6-mn10300/arch/mn10300/include/asm/elf.h:15,
                 from include/linux/elf.h:7,
                 from include/linux/module.h:14,
                 from arch/mn10300/kernel/process.c:11:
include/linux/sysfs.h:177: warning: parameter 1 ('type') has incomplete type
...


The problem appears to be that 

	enum kobj_ns_type

is defined in linux/kobject.h but referenced in linux/sysfs.h, which is
included by linux/kobject.h.  Whilst I see a predeclaration at the top of
linux/sysfs.h, my compiler seems to ignore it.

The compiler is:

	gcc version 3.4-am33-04r2-5

which is a supported version according to the compiler-gcc3.h header file.

David

Re: [PATCH] Break the kobject namespace defs into their own header

[Greg KH]

On Thu, Aug 12, 2010 at 12:56:25PM +0100, David Howells wrote:
> 
> The compiler is:
> 
> 	gcc version 3.4-am33-04r2-5
> 
> which is a supported version according to the compiler-gcc3.h header file.

Ah, yeah, it's a gcc thing.  I'll queue this up.

thanks,

greg k-h