sysfs: clean up sysfs_get_dirent()

The pre-existing sysfs interfaces which take explicit namespace
argument are weird in that they place the optional @ns in front of
@name which is contrary to the established convention.  For example,
we end up forcing vast majority of sysfs_get_dirent() users to do
sysfs_get_dirent(parent, NULL, name), which is silly and error-prone
especially as @ns and @name may be interchanged without causing
compilation warning.

This renames sysfs_get_dirent() to sysfs_get_dirent_ns() and swap the
positions of @name and @ns, and sysfs_get_dirent() is now a wrapper
around sysfs_get_dirent_ns().  This makes confusions a lot less
likely.

There are other interfaces which take @ns before @name.  They'll be
updated by following patches.

This patch doesn't introduce any functional changes.

v2: EXPORT_SYMBOL_GPL() wasn't updated leading to undefined symbol
    error on module builds.  Reported by build test robot.  Fixed.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Kay Sievers <kay@vrfy.org>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/fs/sysfs/group.c b/fs/sysfs/group.c
index 25c78f2..21102158 100644
--- a/fs/sysfs/group.c
+++ b/fs/sysfs/group.c
@@ -207,7 +207,7 @@
 	struct sysfs_dirent *sd;
 
 	if (grp->name) {
-		sd = sysfs_get_dirent(dir_sd, NULL, grp->name);
+		sd = sysfs_get_dirent(dir_sd, grp->name);
 		if (!sd) {
 			WARN(!sd, KERN_WARNING
 			     "sysfs group %p not found for kobject '%s'\n",
@@ -262,7 +262,7 @@
 	struct attribute *const *attr;
 	int i;
 
-	dir_sd = sysfs_get_dirent(kobj->sd, NULL, grp->name);
+	dir_sd = sysfs_get_dirent(kobj->sd, grp->name);
 	if (!dir_sd)
 		return -ENOENT;
 
@@ -289,7 +289,7 @@
 	struct sysfs_dirent *dir_sd;
 	struct attribute *const *attr;
 
-	dir_sd = sysfs_get_dirent(kobj->sd, NULL, grp->name);
+	dir_sd = sysfs_get_dirent(kobj->sd, grp->name);
 	if (dir_sd) {
 		for (attr = grp->attrs; *attr; ++attr)
 			sysfs_hash_and_remove(dir_sd, NULL, (*attr)->name);
@@ -311,7 +311,7 @@
 	struct sysfs_dirent *dir_sd;
 	int error = 0;
 
-	dir_sd = sysfs_get_dirent(kobj->sd, NULL, group_name);
+	dir_sd = sysfs_get_dirent(kobj->sd, group_name);
 	if (!dir_sd)
 		return -ENOENT;
 
@@ -333,7 +333,7 @@
 {
 	struct sysfs_dirent *dir_sd;
 
-	dir_sd = sysfs_get_dirent(kobj->sd, NULL, group_name);
+	dir_sd = sysfs_get_dirent(kobj->sd, group_name);
 	if (dir_sd) {
 		sysfs_hash_and_remove(dir_sd, NULL, link_name);
 		sysfs_put(dir_sd);