cgroup_rm_file: don't delete the uncreated files

in cgroup_add_file,when creating files for cgroup,
some of creation may be skipped. So we need to avoid
deleting these uncreated files in cgroup_rm_file,
otherwise the warning msg will be triggered.

"cgroup_addrm_files: failed to remove memory_pressure_enabled, err=-2"

Signed-off-by: Gao feng <gaofeng@cn.fujitsu.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@redhat.com>
Cc: stable@vger.kernel.org

kernel/cgroup.c

@@ -2724,12 +2724,6 @@ static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
 
 	simple_xattrs_init(&cft->xattrs);
 
-	/* does @cft->flags tell us to skip creation on @cgrp? */
-	if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent)
-		return 0;
-	if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgrp->parent)
-		return 0;
-
 	if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) {
 		strcpy(name, subsys->name);
 		strcat(name, ".");
@@ -2770,6 +2764,12 @@ static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
 	int err, ret = 0;
 
 	for (cft = cfts; cft->name[0] != '\0'; cft++) {
+		/* does cft->flags tell us to skip this file on @cgrp? */
+		if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent)
+			continue;
+		if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgrp->parent)
+			continue;
+
 		if (is_add)
 			err = cgroup_add_file(cgrp, subsys, cft);
 		else