3 files changed, 51 insertions, 37 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 79fd9f4fadb7..34063739745b 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1128,7 +1128,7 @@ void blkcg_policy_unregister(struct blkcg_policy *pol)
 
         /* kill the intf files first */
         if (pol->cftypes)
-                cgroup_rm_cftypes(&blkio_subsys, pol->cftypes);
+                cgroup_rm_cftypes(pol->cftypes);
 
         /* unregister and update blkgs */
         blkcg_policy[pol->plid] = NULL;
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 9c2b9dd9121d..5db8138a0482 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -429,6 +429,12 @@ struct cftype {
         /* CFTYPE_* flags */
         unsigned int flags;
 
+        /*
+         * The subsys this file belongs to.  Initialized automatically
+         * during registration.  NULL for cgroup core files.
+         */
+        struct cgroup_subsys *ss;
+
         int (*open)(struct inode *inode, struct file *file);
         ssize_t (*read)(struct cgroup *cgrp, struct cftype *cft,
                         struct file *file,
@@ -542,7 +548,7 @@ static inline const char *cgroup_name(const struct cgroup *cgrp)
 }
 
 int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
-int cgroup_rm_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
+int cgroup_rm_cftypes(struct cftype *cfts);
 
 bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor);
 
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 271d9a5cde5f..c4bc8dac3b1d 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -219,8 +219,8 @@ static struct cftype cgroup_base_files[];
 
 static void cgroup_offline_fn(struct work_struct *work);
 static int cgroup_destroy_locked(struct cgroup *cgrp);
-static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
-                              struct cftype cfts[], bool is_add);
+static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
+                              bool is_add);
 
 /* convenient tests for these bits */
 static inline bool cgroup_is_dead(const struct cgroup *cgrp)
@@ -974,7 +974,7 @@ static void cgroup_clear_dir(struct cgroup *cgrp, unsigned long 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);
+                        cgroup_addrm_files(cgrp, set->cfts, false);
         }
 }
 
@@ -1623,7 +1623,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
                  */
                 cred = override_creds(&init_cred);
 
-                ret = cgroup_addrm_files(root_cgrp, NULL, cgroup_base_files, true);
+                ret = cgroup_addrm_files(root_cgrp, cgroup_base_files, true);
                 if (ret)
                         goto rm_base_files;
 
@@ -1681,7 +1681,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
 
  rm_base_files:
         free_cgrp_cset_links(&tmp_links);
-        cgroup_addrm_files(&root->top_cgroup, NULL, cgroup_base_files, false);
+        cgroup_addrm_files(&root->top_cgroup, cgroup_base_files, false);
         revert_creds(cred);
  unlock_drop:
         cgroup_exit_root_id(root);
@@ -2694,8 +2694,7 @@ static umode_t cgroup_file_mode(const struct cftype *cft)
         return mode;
 }
 
-static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
-                           struct cftype *cft)
+static int cgroup_add_file(struct cgroup *cgrp, struct cftype *cft)
 {
         struct dentry *dir = cgrp->dentry;
         struct cgroup *parent = __d_cgrp(dir);
@@ -2705,8 +2704,8 @@ static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
         umode_t mode;
         char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
 
-        if (subsys && !(cgrp->root->flags & CGRP_ROOT_NOPREFIX)) {
-                strcpy(name, subsys->name);
+        if (cft->ss && !(cgrp->root->flags & CGRP_ROOT_NOPREFIX)) {
+                strcpy(name, cft->ss->name);
                 strcat(name, ".");
         }
         strcat(name, cft->name);
@@ -2743,17 +2742,16 @@ out:
 /**
  * cgroup_addrm_files - add or remove files to a cgroup directory
  * @cgrp: the target cgroup
- * @subsys: the subsystem of files to be added
  * @cfts: array of cftypes to be added
  * @is_add: whether to add or remove
  *
  * Depending on @is_add, add or remove files defined by @cfts on @cgrp.
- * All @cfts should belong to @subsys.  For removals, this function never
- * fails.  If addition fails, this function doesn't remove files already
- * added.  The caller is responsible for cleaning up.
+ * For removals, this function never fails.  If addition fails, this
+ * function doesn't remove files already added.  The caller is responsible
+ * for cleaning up.
  */
-static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
-                              struct cftype cfts[], bool is_add)
+static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
+                              bool is_add)
 {
         struct cftype *cft;
         int ret;
@@ -2771,7 +2769,7 @@ static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
                         continue;
 
                 if (is_add) {
-                        ret = cgroup_add_file(cgrp, subsys, cft);
+                        ret = cgroup_add_file(cgrp, cft);
                         if (ret) {
                                 pr_warn("cgroup_addrm_files: failed to add %s, err=%d\n",
                                         cft->name, ret);
@@ -2796,11 +2794,11 @@ static void cgroup_cfts_prepare(void)
         mutex_lock(&cgroup_mutex);
 }
 
-static int cgroup_cfts_commit(struct cgroup_subsys *ss,
-                              struct cftype *cfts, bool is_add)
+static int cgroup_cfts_commit(struct cftype *cfts, bool is_add)
         __releases(&cgroup_mutex)
 {
         LIST_HEAD(pending);
+        struct cgroup_subsys *ss = cfts[0].ss;
         struct cgroup *cgrp, *root = &ss->root->top_cgroup;
         struct super_block *sb = ss->root->sb;
         struct dentry *prev = NULL;
@@ -2828,7 +2826,7 @@ static int cgroup_cfts_commit(struct cgroup_subsys *ss,
         inode = root->dentry->d_inode;
         mutex_lock(&inode->i_mutex);
         mutex_lock(&cgroup_mutex);
-        ret = cgroup_addrm_files(root, ss, cfts, is_add);
+        ret = cgroup_addrm_files(root, cfts, is_add);
         mutex_unlock(&cgroup_mutex);
         mutex_unlock(&inode->i_mutex);
 
@@ -2851,7 +2849,7 @@ static int cgroup_cfts_commit(struct cgroup_subsys *ss,
                 mutex_lock(&inode->i_mutex);
                 mutex_lock(&cgroup_mutex);
                 if (cgrp->serial_nr < update_before && !cgroup_is_dead(cgrp))
-                        ret = cgroup_addrm_files(cgrp, ss, cfts, is_add);
+                        ret = cgroup_addrm_files(cgrp, cfts, is_add);
                 mutex_unlock(&cgroup_mutex);
                 mutex_unlock(&inode->i_mutex);
 
@@ -2883,51 +2881,56 @@ out_deact:
 int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
 {
         struct cftype_set *set;
+        struct cftype *cft;
         int ret;
 
         set = kzalloc(sizeof(*set), GFP_KERNEL);
         if (!set)
                 return -ENOMEM;
 
+        for (cft = cfts; cft->name[0] != '\0'; cft++)
+                cft->ss = ss;
+
         cgroup_cfts_prepare();
         set->cfts = cfts;
         list_add_tail(&set->node, &ss->cftsets);
-        ret = cgroup_cfts_commit(ss, cfts, true);
+        ret = cgroup_cfts_commit(cfts, true);
         if (ret)
-                cgroup_rm_cftypes(ss, cfts);
+                cgroup_rm_cftypes(cfts);
         return ret;
 }
 EXPORT_SYMBOL_GPL(cgroup_add_cftypes);
 
 /**
  * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
- * @ss: target cgroup subsystem
  * @cfts: zero-length name terminated array of cftypes
  *
- * Unregister @cfts from @ss.  Files described by @cfts are removed from
- * all existing cgroups to which @ss is attached and all future cgroups
- * won't have them either.  This function can be called anytime whether @ss
- * is attached or not.
+ * Unregister @cfts.  Files described by @cfts are removed from all
+ * existing cgroups and all future cgroups won't have them either.  This
+ * function can be called anytime whether @cfts' subsys is attached or not.
  *
  * Returns 0 on successful unregistration, -ENOENT if @cfts is not
- * registered with @ss.
+ * registered.
  */
-int cgroup_rm_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
+int cgroup_rm_cftypes(struct cftype *cfts)
 {
         struct cftype_set *set;
 
+        if (!cfts || !cfts[0].ss)
+                return -ENOENT;
+
         cgroup_cfts_prepare();
 
-        list_for_each_entry(set, &ss->cftsets, node) {
+        list_for_each_entry(set, &cfts[0].ss->cftsets, node) {
                 if (set->cfts == cfts) {
                         list_del(&set->node);
                         kfree(set);
-                        cgroup_cfts_commit(ss, cfts, false);
+                        cgroup_cfts_commit(cfts, false);
                         return 0;
                 }
         }
 
-        cgroup_cfts_commit(ss, NULL, false);
+        cgroup_cfts_commit(NULL, false);
         return -ENOENT;
 }
 
@@ -4148,7 +4151,7 @@ static int cgroup_populate_dir(struct cgroup *cgrp, unsigned long subsys_mask)
                         continue;
 
                 list_for_each_entry(set, &ss->cftsets, node) {
-                        ret = cgroup_addrm_files(cgrp, ss, set->cfts, true);
+                        ret = cgroup_addrm_files(cgrp, set->cfts, true);
                         if (ret < 0)
                                 goto err;
                 }
@@ -4377,7 +4380,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
 
         idr_replace(&root->cgroup_idr, cgrp, cgrp->id);
 
-        err = cgroup_addrm_files(cgrp, NULL, cgroup_base_files, true);
+        err = cgroup_addrm_files(cgrp, cgroup_base_files, true);
         if (err)
                 goto err_destroy;
 
@@ -4538,7 +4541,7 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
          * but we aren't quite done with @cgrp yet, so hold onto it.
          */
         cgroup_clear_dir(cgrp, cgrp->root->subsys_mask);
-        cgroup_addrm_files(cgrp, NULL, cgroup_base_files, false);
+        cgroup_addrm_files(cgrp, cgroup_base_files, false);
         dget(d);
         cgroup_d_remove_dir(d);
 
@@ -4632,6 +4635,11 @@ static void __init_or_module cgroup_init_cftsets(struct cgroup_subsys *ss)
          * deregistration.
          */
         if (ss->base_cftypes) {
+                struct cftype *cft;
+
+                for (cft = ss->base_cftypes; cft->name[0] != '\0'; cft++)
+                        cft->ss = ss;
+
                 ss->base_cftset.cfts = ss->base_cftypes;
                 list_add_tail(&ss->base_cftset.node, &ss->cftsets);
         }