erofs: clean up erofs_register_sysfs()

After commit 684b290a ("erofs: add support for
FS_IOC_GETFSSYSFSPATH"), `sb->s_sysfs_name` is now valid.

Just use it to get rid of duplicated logic.
Reviewed-by: Sandeep Dhavale <dhavale@google.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20240828095232.571946-1-hsiangkao@linux.alibaba.com

fs/erofs/super.c

@@ -644,7 +644,6 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
 		sb->s_flags |= SB_POSIXACL;
 	else
 		sb->s_flags &= ~SB_POSIXACL;
-	erofs_set_sysfs_name(sb);
 
 #ifdef CONFIG_EROFS_FS_ZIP
 	xa_init(&sbi->managed_pslots);
@@ -682,6 +681,7 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
 	if (err)
 		return err;
 
+	erofs_set_sysfs_name(sb);
 	err = erofs_register_sysfs(sb);
 	if (err)
 		return err;

fs/erofs/sysfs.c

@@ -205,34 +205,16 @@ static struct kobject erofs_feat = {
 int erofs_register_sysfs(struct super_block *sb)
 {
 	struct erofs_sb_info *sbi = EROFS_SB(sb);
-	char *name;
-	char *str = NULL;
 	int err;
 
-	if (erofs_is_fscache_mode(sb)) {
-		if (sbi->domain_id) {
-			str = kasprintf(GFP_KERNEL, "%s,%s", sbi->domain_id,
-					sbi->fsid);
-			if (!str)
-				return -ENOMEM;
-			name = str;
-		} else {
-			name = sbi->fsid;
-		}
-	} else {
-		name = sb->s_id;
-	}
 	sbi->s_kobj.kset = &erofs_root;
 	init_completion(&sbi->s_kobj_unregister);
-	err = kobject_init_and_add(&sbi->s_kobj, &erofs_sb_ktype, NULL, "%s", name);
-	kfree(str);
-	if (err)
-		goto put_sb_kobj;
-	return 0;
-
-put_sb_kobj:
-	kobject_put(&sbi->s_kobj);
-	wait_for_completion(&sbi->s_kobj_unregister);
+	err = kobject_init_and_add(&sbi->s_kobj, &erofs_sb_ktype, NULL, "%s",
+				   sb->s_sysfs_name);
+	if (err) {
+		kobject_put(&sbi->s_kobj);
+		wait_for_completion(&sbi->s_kobj_unregister);
+	}
 	return err;
 }