cgroup: update error handling in cgroup_populate_dir()

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.

v2: The original patch also converted for_each_root_subsys() usages to
    for_each_subsys() without explaining why.  That part has been
    moved to a separate patch.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>

1 files changed, 11 insertions, 2 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 9835a097f3c0..6b7324431b99 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4171,10 +4171,13 @@ 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 ret = 0;
 
         /* process cftsets of each subsystem */
         for_each_root_subsys(cgrp->root, ss) {
@@ -4182,8 +4185,11 @@ static int cgroup_populate_dir(struct cgroup *cgrp, unsigned long subsys_mask)
                 if (!test_bit(ss->subsys_id, &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 +4207,9 @@ 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)