sysfs: make sysfs_add_one() automatically check for duplicate entry

Make sysfs_add_one() check for duplicate entry and return -EEXIST if
such entry exists.  This simplifies node addition code a bit.

This patch doesn't introduce any noticeable behavior change.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c
index c129f307..a6b13f1 100644
--- a/fs/sysfs/symlink.c
+++ b/fs/sysfs/symlink.c
@@ -91,14 +91,11 @@
 	target_sd = NULL;	/* reference is now owned by the symlink */
 
 	sysfs_addrm_start(&acxt, parent_sd);
+	error = sysfs_add_one(&acxt, sd);
+	sysfs_addrm_finish(&acxt);
 
-	if (!sysfs_find_dirent(parent_sd, name))
-		sysfs_add_one(&acxt, sd);
-
-	if (!sysfs_addrm_finish(&acxt)) {
-		error = -EEXIST;
+	if (error)
 		goto out_put;
-	}
 
 	return 0;