cgroup: fix bogus kernel warnings when cgroup_create() failed

If cgroup_create() failed and cgroup_destroy_locked() is called to
do cleanup, we'll see a bunch of warnings:

cgroup_addrm_files: failed to remove 2MB.limit_in_bytes, err=-2
cgroup_addrm_files: failed to remove 2MB.usage_in_bytes, err=-2
cgroup_addrm_files: failed to remove 2MB.max_usage_in_bytes, err=-2
cgroup_addrm_files: failed to remove 2MB.failcnt, err=-2
cgroup_addrm_files: failed to remove prioidx, err=-2
cgroup_addrm_files: failed to remove ifpriomap, err=-2
...

We failed to remove those files, because cgroup_create() has failed
before creating those cgroup files.

To fix this, we simply don't warn if cgroup_rm_file() can't find the
cft entry.

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

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index a893985..ad3359f 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -921,13 +921,17 @@ static void remove_dir(struct dentry *d)
        dput(parent);
 }
 
-static int cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
+static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
 {
        struct cfent *cfe;
 
        lockdep_assert_held(&cgrp->dentry->d_inode->i_mutex);
        lockdep_assert_held(&cgroup_mutex);
 
+       /*
+        * If we're doing cleanup due to failure of cgroup_create(),
+        * the corresponding @cfe may not exist.
+        */
        list_for_each_entry(cfe, &cgrp->files, node) {
                struct dentry *d = cfe->dentry;
 
@@ -940,9 +944,8 @@ static int cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
                list_del_init(&cfe->node);
                dput(d);
 
-               return 0;
+               break;
        }
-       return -ENOENT;
 }
 
 /**
@@ -2758,14 +2761,14 @@ static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
                if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgrp->parent)
                        continue;
 
-               if (is_add)
+               if (is_add) {
                        err = cgroup_add_file(cgrp, subsys, cft);
-               else
-                       err = cgroup_rm_file(cgrp, cft);
-               if (err) {
-                       pr_warning("cgroup_addrm_files: failed to %s %s, err=%d\n",
-                                  is_add ? "add" : "remove", cft->name, err);
+                       if (err)
+                               pr_warn("cgroup_addrm_files: failed to add %s, err=%d\n",
+                                       cft->name, err);
                        ret = err;
+               } else {
+                       cgroup_rm_file(cgrp, cft);
                }
        }
        return ret;