[PATCH 5/9] cgroup: update error handling in cgroup_populate_dir()

[Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

cgroup_populate_dir() didn't use to check whether the actual file
creations were successful and could return success with only subset of
the requested files created, which is nasty.

This patch udpates cgroup_populate_dir() so that it either succeeds
with all files or fails with no file.

Signed-off-by: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
---
 kernel/cgroup.c | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 254d54e..3475267 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -965,10 +965,12 @@ static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
 static void cgroup_clear_dir(struct cgroup *cgrp, unsigned long subsys_mask)
 {
 	struct cgroup_subsys *ss;
+	int i;
 
-	for_each_root_subsys(cgrp->root, ss) {
+	for_each_subsys(ss, i) {
 		struct cftype_set *set;
-		if (!test_bit(ss->subsys_id, &subsys_mask))
+
+		if (!test_bit(i, &subsys_mask))
 			continue;
 		list_for_each_entry(set, &ss->cftsets, node)
 			cgroup_addrm_files(cgrp, NULL, set->cfts, false);
@@ -4171,19 +4173,26 @@ static struct cftype cgroup_base_files[] = {
  * cgroup_populate_dir - create subsys files in a cgroup directory
  * @cgrp: target cgroup
  * @subsys_mask: mask of the subsystem ids whose files should be added
+ *
+ * On failure, no file is added.
  */
 static int cgroup_populate_dir(struct cgroup *cgrp, unsigned long subsys_mask)
 {
 	struct cgroup_subsys *ss;
+	int i, ret = 0;
 
 	/* process cftsets of each subsystem */
-	for_each_root_subsys(cgrp->root, ss) {
+	for_each_subsys(ss, i) {
 		struct cftype_set *set;
-		if (!test_bit(ss->subsys_id, &subsys_mask))
+
+		if (!test_bit(i, &subsys_mask))
 			continue;
 
-		list_for_each_entry(set, &ss->cftsets, node)
-			cgroup_addrm_files(cgrp, ss, set->cfts, true);
+		list_for_each_entry(set, &ss->cftsets, node) {
+			ret = cgroup_addrm_files(cgrp, ss, set->cfts, true);
+			if (ret < 0)
+				goto err;
+		}
 	}
 
 	/* This cgroup is ready now */
@@ -4201,6 +4210,9 @@ static int cgroup_populate_dir(struct cgroup *cgrp, unsigned long subsys_mask)
 	}
 
 	return 0;
+err:
+	cgroup_clear_dir(cgrp, subsys_mask);
+	return ret;
 }
 
 static void css_dput_fn(struct work_struct *work)
-- 
1.8.3.1