sysfs: make attr namespace interface less convoluted

sysfs ns (namespace) implementation became more convoluted than
necessary while trying to hide ns information from visible interface.
The relatively recent attr ns support is a good example.

* attr ns tag is determined by sysfs_ops->namespace() callback while
  dir tag is determined by kobj_type->namespace().  The placement is
  arbitrary.

* Instead of performing operations with explicit ns tag, the namespace
  callback is routed through sysfs_attr_ns(), sysfs_ops->namespace(),
  class_attr_namespace(), class_attr->namespace().  It's not simpler
  in any sense.  The only thing this convolution does is traversing
  the whole stack backwards.

The namespace callbacks are unncessary because the operations involved
are inherently synchronous.  The information can be provided in in
straight-forward top-down direction and reversing that direction is
unnecessary and against basic design principles.

This backward interface is unnecessarily convoluted and hinders
properly separating out sysfs from driver model / kobject for proper
layering.  This patch updates attr ns support such that

* sysfs_ops->namespace() and class_attr->namespace() are dropped.

* sysfs_{create|remove}_file_ns(), which take explicit @ns param, are
  added and sysfs_{create|remove}_file() are now simple wrappers
  around the ns aware functions.

* ns handling is dropped from sysfs_chmod_file().  Nobody uses it at
  this point.  sysfs_chmod_file_ns() can be added later if necessary.

* Explicit @ns is propagated through class_{create|remove}_file_ns()
  and netdev_class_{create|remove}_file_ns().

* driver/net/bonding which is currently the only user of attr
  namespace is updated to use netdev_class_{create|remove}_file_ns()
  with @bh->net as the ns tag instead of using the namespace callback.

This patch should be an equivalent conversion without any functional
difference.  It makes the code easier to follow, reduces lines of code
a bit and helps proper separation and layering.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Kay Sievers <kay@vrfy.org>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 12 insertions, 31 deletions

diff --git a/drivers/base/class.c b/drivers/base/class.c
index 8b7818b..f96f704 100644
--- a/drivers/base/class.c
+++ b/drivers/base/class.c
@@ -47,18 +47,6 @@ static ssize_t class_attr_store(struct kobject *kobj, struct attribute *attr,
 	return ret;
 }
 
-static const void *class_attr_namespace(struct kobject *kobj,
-					const struct attribute *attr)
-{
-	struct class_attribute *class_attr = to_class_attr(attr);
-	struct subsys_private *cp = to_subsys_private(kobj);
-	const void *ns = NULL;
-
-	if (class_attr->namespace)
-		ns = class_attr->namespace(cp->class, class_attr);
-	return ns;
-}
-
 static void class_release(struct kobject *kobj)
 {
 	struct subsys_private *cp = to_subsys_private(kobj);
@@ -86,7 +74,6 @@ static const struct kobj_ns_type_operations *class_child_ns_type(struct kobject
 static const struct sysfs_ops class_sysfs_ops = {
 	.show	   = class_attr_show,
 	.store	   = class_attr_store,
-	.namespace = class_attr_namespace,
 };
 
 static struct kobj_type class_ktype = {
@@ -99,21 +86,23 @@ static struct kobj_type class_ktype = {
 static struct kset *class_kset;
 
 
-int class_create_file(struct class *cls, const struct class_attribute *attr)
+int class_create_file_ns(struct class *cls, const struct class_attribute *attr,
+			 const void *ns)
 {
 	int error;
 	if (cls)
-		error = sysfs_create_file(&cls->p->subsys.kobj,
-					  &attr->attr);
+		error = sysfs_create_file_ns(&cls->p->subsys.kobj,
+					     &attr->attr, ns);
 	else
 		error = -EINVAL;
 	return error;
 }
 
-void class_remove_file(struct class *cls, const struct class_attribute *attr)
+void class_remove_file_ns(struct class *cls, const struct class_attribute *attr,
+			  const void *ns)
 {
 	if (cls)
-		sysfs_remove_file(&cls->p->subsys.kobj, &attr->attr);
+		sysfs_remove_file_ns(&cls->p->subsys.kobj, &attr->attr, ns);
 }
 
 static struct class *class_get(struct class *cls)
@@ -600,8 +589,8 @@ int __init classes_init(void)
 	return 0;
 }
 
-EXPORT_SYMBOL_GPL(class_create_file);
-EXPORT_SYMBOL_GPL(class_remove_file);
+EXPORT_SYMBOL_GPL(class_create_file_ns);
+EXPORT_SYMBOL_GPL(class_remove_file_ns);
 EXPORT_SYMBOL_GPL(class_unregister);
 EXPORT_SYMBOL_GPL(class_destroy);
 
diff --git a/drivers/net/bonding/bond_sysfs.c b/drivers/net/bonding/bond_sysfs.c
index c29b836..ec9b646 100644
--- a/drivers/net/bonding/bond_sysfs.c
+++ b/drivers/net/bonding/bond_sysfs.c
@@ -149,14 +149,6 @@ err_no_cmd:
 	return -EPERM;
 }
 
-static const void *bonding_namespace(struct class *cls,
-				     const struct class_attribute *attr)
-{
-	const struct bond_net *bn =
-		container_of(attr, struct bond_net, class_attr_bonding_masters);
-	return bn->net;
-}
-
 /* class attribute for bond_masters file.  This ends up in /sys/class/net */
 static const struct class_attribute class_attr_bonding_masters = {
 	.attr = {
@@ -165,7 +157,6 @@ static const struct class_attribute class_attr_bonding_masters = {
 	},
 	.show = bonding_show_bonds,
 	.store = bonding_store_bonds,
-	.namespace = bonding_namespace,
 };
 
 int bond_create_slave_symlinks(struct net_device *master,
@@ -1787,7 +1778,8 @@ int bond_create_sysfs(struct bond_net *bn)
 	bn->class_attr_bonding_masters = class_attr_bonding_masters;
 	sysfs_attr_init(&bn->class_attr_bonding_masters.attr);
 
-	ret = netdev_class_create_file(&bn->class_attr_bonding_masters);
+	ret = netdev_class_create_file_ns(&bn->class_attr_bonding_masters,
+					  bn->net);
 	/*
 	 * Permit multiple loads of the module by ignoring failures to
 	 * create the bonding_masters sysfs file.  Bonding devices
@@ -1817,7 +1809,7 @@ int bond_create_sysfs(struct bond_net *bn)
  */
 void bond_destroy_sysfs(struct bond_net *bn)
 {
-	netdev_class_remove_file(&bn->class_attr_bonding_masters);
+	netdev_class_remove_file_ns(&bn->class_attr_bonding_masters, bn->net);
 }
 
 /*