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/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 86ef346..a094356 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -408,7 +408,7 @@
 			IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING;
 
 	if (!value_sd) {
-		value_sd = sysfs_get_dirent(dev->kobj.sd, NULL, "value");
+		value_sd = sysfs_get_dirent(dev->kobj.sd, "value");
 		if (!value_sd) {
 			ret = -ENODEV;
 			goto err_out;
diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index a7fd821..12dc29b 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -1654,9 +1654,9 @@
 	bitmap->mddev = mddev;
 
 	if (mddev->kobj.sd)
-		bm = sysfs_get_dirent(mddev->kobj.sd, NULL, "bitmap");
+		bm = sysfs_get_dirent(mddev->kobj.sd, "bitmap");
 	if (bm) {
-		bitmap->sysfs_can_clear = sysfs_get_dirent(bm, NULL, "can_clear");
+		bitmap->sysfs_can_clear = sysfs_get_dirent(bm, "can_clear");
 		sysfs_put(bm);
 	} else
 		bitmap->sysfs_can_clear = NULL;
diff --git a/drivers/md/md.c b/drivers/md/md.c
index adf4d7e..8a0d762 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -3555,7 +3555,7 @@
 			printk(KERN_WARNING
 			       "md: cannot register extra attributes for %s\n",
 			       mdname(mddev));
-		mddev->sysfs_action = sysfs_get_dirent(mddev->kobj.sd, NULL, "sync_action");
+		mddev->sysfs_action = sysfs_get_dirent(mddev->kobj.sd, "sync_action");
 	}		
 	if (mddev->pers->sync_request != NULL &&
 	    pers->sync_request == NULL) {
diff --git a/drivers/md/md.h b/drivers/md/md.h
index 608050c..b0051f2 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -501,7 +501,7 @@
 static inline struct sysfs_dirent *sysfs_get_dirent_safe(struct sysfs_dirent *sd, char *name)
 {
 	if (sd)
-		return sysfs_get_dirent(sd, NULL, name);
+		return sysfs_get_dirent(sd, name);
 	return sd;
 }
 static inline void sysfs_notify_dirent_safe(struct sysfs_dirent *sd)