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>

1 files changed, 23 insertions, 8 deletions

diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
index 11baec7c9b2..82f7fac78e7 100644
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -173,7 +173,6 @@ struct bin_attribute bin_attr_##_name = __BIN_ATTR_RW(_name, _size)
 struct sysfs_ops {
 	ssize_t	(*show)(struct kobject *, struct attribute *, char *);
 	ssize_t	(*store)(struct kobject *, struct attribute *, const char *, size_t);
-	const void *(*namespace)(struct kobject *, const struct attribute *);
 };
 
 struct sysfs_dirent;
@@ -189,13 +188,15 @@ int __must_check sysfs_rename_dir(struct kobject *kobj, const char *new_name);
 int __must_check sysfs_move_dir(struct kobject *kobj,
 				struct kobject *new_parent_kobj);
 
-int __must_check sysfs_create_file(struct kobject *kobj,
-				   const struct attribute *attr);
+int __must_check sysfs_create_file_ns(struct kobject *kobj,
+				      const struct attribute *attr,
+				      const void *ns);
 int __must_check sysfs_create_files(struct kobject *kobj,
 				   const struct attribute **attr);
 int __must_check sysfs_chmod_file(struct kobject *kobj,
 				  const struct attribute *attr, umode_t mode);
-void sysfs_remove_file(struct kobject *kobj, const struct attribute *attr);
+void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
+			  const void *ns);
 void sysfs_remove_files(struct kobject *kobj, const struct attribute **attr);
 
 int __must_check sysfs_create_bin_file(struct kobject *kobj,
@@ -277,8 +278,9 @@ static inline int sysfs_move_dir(struct kobject *kobj,
 	return 0;
 }
 
-static inline int sysfs_create_file(struct kobject *kobj,
-				    const struct attribute *attr)
+static inline int sysfs_create_file_ns(struct kobject *kobj,
+				       const struct attribute *attr,
+				       const void *ns)
 {
 	return 0;
 }
@@ -295,8 +297,9 @@ static inline int sysfs_chmod_file(struct kobject *kobj,
 	return 0;
 }
 
-static inline void sysfs_remove_file(struct kobject *kobj,
-				     const struct attribute *attr)
+static inline void sysfs_remove_file_ns(struct kobject *kobj,
+					const struct attribute *attr,
+					const void *ns)
 {
 }
 
@@ -435,4 +438,16 @@ static inline int __must_check sysfs_init(void)
 
 #endif /* CONFIG_SYSFS */
 
+static inline int __must_check sysfs_create_file(struct kobject *kobj,
+						 const struct attribute *attr)
+{
+	return sysfs_create_file_ns(kobj, attr, NULL);
+}
+
+static inline void sysfs_remove_file(struct kobject *kobj,
+				     const struct attribute *attr)
+{
+	return sysfs_remove_file_ns(kobj, attr, NULL);
+}
+
 #endif /* _SYSFS_H_ */