Merge branch 'for-3.7' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup updates from Tejun Heo:

 - xattr support added.  The implementation is shared with tmpfs.  The
   usage is restricted and intended to be used to manage per-cgroup
   metadata by system software.  tmpfs changes are routed through this
   branch with Hugh's permission.

 - cgroup subsystem ID handling simplified.

* 'for-3.7' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: Define CGROUP_SUBSYS_COUNT according the configuration
  cgroup: Assign subsystem IDs during compile time
  cgroup: Do not depend on a given order when populating the subsys array
  cgroup: Wrap subsystem selection macro
  cgroup: Remove CGROUP_BUILTIN_SUBSYS_COUNT
  cgroup: net_prio: Do not define task_netpioidx() when not selected
  cgroup: net_cls: Do not define task_cls_classid() when not selected
  cgroup: net_cls: Move sock_update_classid() declaration to cls_cgroup.h
  cgroup: trivial fixes for Documentation/cgroups/cgroups.txt
  xattr: mark variable as uninitialized to make both gcc and smatch happy
  fs: add missing documentation to simple_xattr functions
  cgroup: add documentation on extended attributes usage
  cgroup: rename subsys_bits to subsys_mask
  cgroup: add xattr support
  cgroup: revise how we re-populate root directory
  xattr: extract simple_xattr code from tmpfs

1 files changed, 219 insertions, 101 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 79818507e444..485cc1487ea2 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -88,11 +88,12 @@ static DEFINE_MUTEX(cgroup_root_mutex);
 
 /*
  * Generate an array of cgroup subsystem pointers. At boot time, this is
- * populated up to CGROUP_BUILTIN_SUBSYS_COUNT, and modular subsystems are
+ * populated with the built in subsystems, and modular subsystems are
  * registered after that. The mutable section of this array is protected by
  * cgroup_mutex.
  */
-#define SUBSYS(_x) &_x ## _subsys,
+#define SUBSYS(_x) [_x ## _subsys_id] = &_x ## _subsys,
+#define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
 static struct cgroup_subsys *subsys[CGROUP_SUBSYS_COUNT] = {
 #include <linux/cgroup_subsys.h>
 };
@@ -111,13 +112,13 @@ struct cgroupfs_root {
          * The bitmask of subsystems intended to be attached to this
          * hierarchy
          */
-        unsigned long subsys_bits;
+        unsigned long subsys_mask;
 
         /* Unique id for this hierarchy. */
         int hierarchy_id;
 
         /* The bitmask of subsystems currently attached to this hierarchy */
-        unsigned long actual_subsys_bits;
+        unsigned long actual_subsys_mask;
 
         /* A list running through the attached subsystems */
         struct list_head subsys_list;
@@ -276,7 +277,8 @@ inline int cgroup_is_removed(const struct cgroup *cgrp)
 
 /* bits in struct cgroupfs_root flags field */
 enum {
-        ROOT_NOPREFIX, /* mounted subsystems have no named prefix */
+        ROOT_NOPREFIX,  /* mounted subsystems have no named prefix */
+        ROOT_XATTR,     /* supports extended attributes */
 };
 
 static int cgroup_is_releasable(const struct cgroup *cgrp)
@@ -556,7 +558,7 @@ static struct css_set *find_existing_css_set(
          * won't change, so no need for locking.
          */
         for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
-                if (root->subsys_bits & (1UL << i)) {
+                if (root->subsys_mask & (1UL << i)) {
                         /* Subsystem is in this hierarchy. So we want
                          * the subsystem state from the new
                          * cgroup */
@@ -824,7 +826,8 @@ EXPORT_SYMBOL_GPL(cgroup_unlock);
 static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode);
 static struct dentry *cgroup_lookup(struct inode *, struct dentry *, unsigned int);
 static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
-static int cgroup_populate_dir(struct cgroup *cgrp);
+static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,
+                               unsigned long subsys_mask);
 static const struct inode_operations cgroup_dir_inode_operations;
 static const struct file_operations proc_cgroupstats_operations;
 
@@ -912,15 +915,19 @@ static void cgroup_diput(struct dentry *dentry, struct inode *inode)
                  */
                 BUG_ON(!list_empty(&cgrp->pidlists));
 
+                simple_xattrs_free(&cgrp->xattrs);
+
                 kfree_rcu(cgrp, rcu_head);
         } else {
                 struct cfent *cfe = __d_cfe(dentry);
                 struct cgroup *cgrp = dentry->d_parent->d_fsdata;
+                struct cftype *cft = cfe->type;
 
                 WARN_ONCE(!list_empty(&cfe->node) &&
                           cgrp != &cgrp->root->top_cgroup,
                           "cfe still linked for %s\n", cfe->type->name);
                 kfree(cfe);
+                simple_xattrs_free(&cft->xattrs);
         }
         iput(inode);
 }
@@ -963,12 +970,29 @@ static int cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
         return -ENOENT;
 }
 
-static void cgroup_clear_directory(struct dentry *dir)
+/**
+ * cgroup_clear_directory - selective removal of base and subsystem files
+ * @dir: directory containing the files
+ * @base_files: true if the base files should be removed
+ * @subsys_mask: mask of the subsystem ids whose files should be removed
+ */
+static void cgroup_clear_directory(struct dentry *dir, bool base_files,
+                                   unsigned long subsys_mask)
 {
         struct cgroup *cgrp = __d_cgrp(dir);
+        struct cgroup_subsys *ss;
 
-        while (!list_empty(&cgrp->files))
-                cgroup_rm_file(cgrp, NULL);
+        for_each_subsys(cgrp->root, ss) {
+                struct cftype_set *set;
+                if (!test_bit(ss->subsys_id, &subsys_mask))
+                        continue;
+                list_for_each_entry(set, &ss->cftsets, node)
+                        cgroup_rm_file(cgrp, set->cfts);
+        }
+        if (base_files) {
+                while (!list_empty(&cgrp->files))
+                        cgroup_rm_file(cgrp, NULL);
+        }
 }
 
 /*
@@ -977,8 +1001,9 @@ static void cgroup_clear_directory(struct dentry *dir)
 static void cgroup_d_remove_dir(struct dentry *dentry)
 {
         struct dentry *parent;
+        struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
 
-        cgroup_clear_directory(dentry);
+        cgroup_clear_directory(dentry, true, root->subsys_mask);
 
         parent = dentry->d_parent;
         spin_lock(&parent->d_lock);
@@ -1022,22 +1047,22 @@ void cgroup_release_and_wakeup_rmdir(struct cgroup_subsys_state *css)
  * returns an error, no reference counts are touched.
  */
 static int rebind_subsystems(struct cgroupfs_root *root,
-                              unsigned long final_bits)
+                              unsigned long final_subsys_mask)
 {
-        unsigned long added_bits, removed_bits;
+        unsigned long added_mask, removed_mask;
         struct cgroup *cgrp = &root->top_cgroup;
         int i;
 
         BUG_ON(!mutex_is_locked(&cgroup_mutex));
         BUG_ON(!mutex_is_locked(&cgroup_root_mutex));
 
-        removed_bits = root->actual_subsys_bits & ~final_bits;
-        added_bits = final_bits & ~root->actual_subsys_bits;
+        removed_mask = root->actual_subsys_mask & ~final_subsys_mask;
+        added_mask = final_subsys_mask & ~root->actual_subsys_mask;
         /* Check that any added subsystems are currently free */
         for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
                 unsigned long bit = 1UL << i;
                 struct cgroup_subsys *ss = subsys[i];
-                if (!(bit & added_bits))
+                if (!(bit & added_mask))
                         continue;
                 /*
                  * Nobody should tell us to do a subsys that doesn't exist:
@@ -1062,7 +1087,7 @@ static int rebind_subsystems(struct cgroupfs_root *root,
         for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
                 struct cgroup_subsys *ss = subsys[i];
                 unsigned long bit = 1UL << i;
-                if (bit & added_bits) {
+                if (bit & added_mask) {
                         /* We're binding this subsystem to this hierarchy */
                         BUG_ON(ss == NULL);
                         BUG_ON(cgrp->subsys[i]);
@@ -1075,7 +1100,7 @@ static int rebind_subsystems(struct cgroupfs_root *root,
                         if (ss->bind)
                                 ss->bind(cgrp);
                         /* refcount was already taken, and we're keeping it */
-                } else if (bit & removed_bits) {
+                } else if (bit & removed_mask) {
                         /* We're removing this subsystem */
                         BUG_ON(ss == NULL);
                         BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
@@ -1088,7 +1113,7 @@ static int rebind_subsystems(struct cgroupfs_root *root,
                         list_move(&ss->sibling, &rootnode.subsys_list);
                         /* subsystem is now free - drop reference on module */
                         module_put(ss->module);
-                } else if (bit & final_bits) {
+                } else if (bit & final_subsys_mask) {
                         /* Subsystem state should already exist */
                         BUG_ON(ss == NULL);
                         BUG_ON(!cgrp->subsys[i]);
@@ -1105,7 +1130,7 @@ static int rebind_subsystems(struct cgroupfs_root *root,
                         BUG_ON(cgrp->subsys[i]);
                 }
         }
-        root->subsys_bits = root->actual_subsys_bits = final_bits;
+        root->subsys_mask = root->actual_subsys_mask = final_subsys_mask;
         synchronize_rcu();
 
         return 0;
@@ -1121,6 +1146,8 @@ static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
                 seq_printf(seq, ",%s", ss->name);
         if (test_bit(ROOT_NOPREFIX, &root->flags))
                 seq_puts(seq, ",noprefix");
+        if (test_bit(ROOT_XATTR, &root->flags))
+                seq_puts(seq, ",xattr");
         if (strlen(root->release_agent_path))
                 seq_printf(seq, ",release_agent=%s", root->release_agent_path);
         if (clone_children(&root->top_cgroup))
@@ -1132,7 +1159,7 @@ static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
 }
 
 struct cgroup_sb_opts {
-        unsigned long subsys_bits;
+        unsigned long subsys_mask;
         unsigned long flags;
         char *release_agent;
         bool clone_children;
@@ -1189,6 +1216,10 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
                         opts->clone_children = true;
                         continue;
                 }
+                if (!strcmp(token, "xattr")) {
+                        set_bit(ROOT_XATTR, &opts->flags);
+                        continue;
+                }
                 if (!strncmp(token, "release_agent=", 14)) {
                         /* Specifying two release agents is forbidden */
                         if (opts->release_agent)
@@ -1237,7 +1268,7 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
                         /* Mutually exclusive option 'all' + subsystem name */
                         if (all_ss)
                                 return -EINVAL;
-                        set_bit(i, &opts->subsys_bits);
+                        set_bit(i, &opts->subsys_mask);
                         one_ss = true;
 
                         break;
@@ -1258,7 +1289,7 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
                                 continue;
                         if (ss->disabled)
                                 continue;
-                        set_bit(i, &opts->subsys_bits);
+                        set_bit(i, &opts->subsys_mask);
                 }
         }
 
@@ -1270,19 +1301,19 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
          * the cpuset subsystem.
          */
         if (test_bit(ROOT_NOPREFIX, &opts->flags) &&
-            (opts->subsys_bits & mask))
+            (opts->subsys_mask & mask))
                 return -EINVAL;
 
 
         /* Can't specify "none" and some subsystems */
-        if (opts->subsys_bits && opts->none)
+        if (opts->subsys_mask && opts->none)
                 return -EINVAL;
 
         /*
          * We either have to specify by name or by subsystems. (So all
          * empty hierarchies must have a name).
          */
-        if (!opts->subsys_bits && !opts->name)
+        if (!opts->subsys_mask && !opts->name)
                 return -EINVAL;
 
         /*
@@ -1291,10 +1322,10 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
          * take duplicate reference counts on a subsystem that's already used,
          * but rebind_subsystems handles this case.
          */
-        for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
+        for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
                 unsigned long bit = 1UL << i;
 
-                if (!(bit & opts->subsys_bits))
+                if (!(bit & opts->subsys_mask))
                         continue;
                 if (!try_module_get(subsys[i]->module)) {
                         module_pin_failed = true;
@@ -1307,11 +1338,11 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
                  * raced with a module_delete call, and to the user this is
                  * essentially a "subsystem doesn't exist" case.
                  */
-                for (i--; i >= CGROUP_BUILTIN_SUBSYS_COUNT; i--) {
+                for (i--; i >= 0; i--) {
                         /* drop refcounts only on the ones we took */
                         unsigned long bit = 1UL << i;
 
-                        if (!(bit & opts->subsys_bits))
+                        if (!(bit & opts->subsys_mask))
                                 continue;
                         module_put(subsys[i]->module);
                 }
@@ -1321,13 +1352,13 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
         return 0;
 }
 
-static void drop_parsed_module_refcounts(unsigned long subsys_bits)
+static void drop_parsed_module_refcounts(unsigned long subsys_mask)
 {
         int i;
-        for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
+        for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
                 unsigned long bit = 1UL << i;
 
-                if (!(bit & subsys_bits))
+                if (!(bit & subsys_mask))
                         continue;
                 module_put(subsys[i]->module);
         }
@@ -1339,6 +1370,7 @@ static int cgroup_remount(struct super_block *sb, int *flags, char *data)
         struct cgroupfs_root *root = sb->s_fs_info;
         struct cgroup *cgrp = &root->top_cgroup;
         struct cgroup_sb_opts opts;
+        unsigned long added_mask, removed_mask;
 
         mutex_lock(&cgrp->dentry->d_inode->i_mutex);
         mutex_lock(&cgroup_mutex);
@@ -1350,27 +1382,31 @@ static int cgroup_remount(struct super_block *sb, int *flags, char *data)
                 goto out_unlock;
 
         /* See feature-removal-schedule.txt */
-        if (opts.subsys_bits != root->actual_subsys_bits || opts.release_agent)
+        if (opts.subsys_mask != root->actual_subsys_mask || opts.release_agent)
                 pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n",
                            task_tgid_nr(current), current->comm);
 
+        added_mask = opts.subsys_mask & ~root->subsys_mask;
+        removed_mask = root->subsys_mask & ~opts.subsys_mask;
+
         /* Don't allow flags or name to change at remount */
         if (opts.flags != root->flags ||
             (opts.name && strcmp(opts.name, root->name))) {
                 ret = -EINVAL;
-                drop_parsed_module_refcounts(opts.subsys_bits);
+                drop_parsed_module_refcounts(opts.subsys_mask);
                 goto out_unlock;
         }
 
-        ret = rebind_subsystems(root, opts.subsys_bits);
+        ret = rebind_subsystems(root, opts.subsys_mask);
         if (ret) {
-                drop_parsed_module_refcounts(opts.subsys_bits);
+                drop_parsed_module_refcounts(opts.subsys_mask);
                 goto out_unlock;
         }
 
         /* clear out any existing files and repopulate subsystem files */
-        cgroup_clear_directory(cgrp->dentry);
-        cgroup_populate_dir(cgrp);
+        cgroup_clear_directory(cgrp->dentry, false, removed_mask);
+        /* re-populate subsystem files */
+        cgroup_populate_dir(cgrp, false, added_mask);
 
         if (opts.release_agent)
                 strcpy(root->release_agent_path, opts.release_agent);
@@ -1401,6 +1437,7 @@ static void init_cgroup_housekeeping(struct cgroup *cgrp)
         mutex_init(&cgrp->pidlist_mutex);
         INIT_LIST_HEAD(&cgrp->event_list);
         spin_lock_init(&cgrp->event_list_lock);
+        simple_xattrs_init(&cgrp->xattrs);
 }
 
 static void init_cgroup_root(struct cgroupfs_root *root)
@@ -1455,8 +1492,8 @@ static int cgroup_test_super(struct super_block *sb, void *data)
          * If we asked for subsystems (or explicitly for no
          * subsystems) then they must match
          */
-        if ((opts->subsys_bits || opts->none)
-            && (opts->subsys_bits != root->subsys_bits))
+        if ((opts->subsys_mask || opts->none)
+            && (opts->subsys_mask != root->subsys_mask))
                 return 0;
 
         return 1;
@@ -1466,7 +1503,7 @@ static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
 {
         struct cgroupfs_root *root;
 
-        if (!opts->subsys_bits && !opts->none)
+        if (!opts->subsys_mask && !opts->none)
                 return NULL;
 
         root = kzalloc(sizeof(*root), GFP_KERNEL);
@@ -1479,7 +1516,7 @@ static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
         }
         init_cgroup_root(root);
 
-        root->subsys_bits = opts->subsys_bits;
+        root->subsys_mask = opts->subsys_mask;
         root->flags = opts->flags;
         if (opts->release_agent)
                 strcpy(root->release_agent_path, opts->release_agent);
@@ -1511,7 +1548,7 @@ static int cgroup_set_super(struct super_block *sb, void *data)
         if (!opts->new_root)
                 return -EINVAL;
 
-        BUG_ON(!opts->subsys_bits && !opts->none);
+        BUG_ON(!opts->subsys_mask && !opts->none);
 
         ret = set_anon_super(sb, NULL);
         if (ret)
@@ -1629,7 +1666,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
                 if (ret)
                         goto unlock_drop;
 
-                ret = rebind_subsystems(root, root->subsys_bits);
+                ret = rebind_subsystems(root, root->subsys_mask);
                 if (ret == -EBUSY) {
                         free_cg_links(&tmp_cg_links);
                         goto unlock_drop;
@@ -1669,7 +1706,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
                 BUG_ON(root->number_of_cgroups != 1);
 
                 cred = override_creds(&init_cred);
-                cgroup_populate_dir(root_cgrp);
+                cgroup_populate_dir(root_cgrp, true, root->subsys_mask);
                 revert_creds(cred);
                 mutex_unlock(&cgroup_root_mutex);
                 mutex_unlock(&cgroup_mutex);
@@ -1681,7 +1718,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
                  */
                 cgroup_drop_root(opts.new_root);
                 /* no subsys rebinding, so refcounts don't change */
-                drop_parsed_module_refcounts(opts.subsys_bits);
+                drop_parsed_module_refcounts(opts.subsys_mask);
         }
 
         kfree(opts.release_agent);
@@ -1695,7 +1732,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
  drop_new_super:
         deactivate_locked_super(sb);
  drop_modules:
-        drop_parsed_module_refcounts(opts.subsys_bits);
+        drop_parsed_module_refcounts(opts.subsys_mask);
  out_err:
         kfree(opts.release_agent);
         kfree(opts.name);
@@ -1745,6 +1782,8 @@ static void cgroup_kill_sb(struct super_block *sb) {
         mutex_unlock(&cgroup_root_mutex);
         mutex_unlock(&cgroup_mutex);
 
+        simple_xattrs_free(&cgrp->xattrs);
+
         kill_litter_super(sb);
         cgroup_drop_root(root);
 }
@@ -2551,6 +2590,64 @@ static int cgroup_rename(struct inode *old_dir, struct dentry *old_dentry,
         return simple_rename(old_dir, old_dentry, new_dir, new_dentry);
 }
 
+static struct simple_xattrs *__d_xattrs(struct dentry *dentry)
+{
+        if (S_ISDIR(dentry->d_inode->i_mode))
+                return &__d_cgrp(dentry)->xattrs;
+        else
+                return &__d_cft(dentry)->xattrs;
+}
+
+static inline int xattr_enabled(struct dentry *dentry)
+{
+        struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
+        return test_bit(ROOT_XATTR, &root->flags);
+}
+
+static bool is_valid_xattr(const char *name)
+{
+        if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) ||
+            !strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN))
+                return true;
+        return false;
+}
+
+static int cgroup_setxattr(struct dentry *dentry, const char *name,
+                           const void *val, size_t size, int flags)
+{
+        if (!xattr_enabled(dentry))
+                return -EOPNOTSUPP;
+        if (!is_valid_xattr(name))
+                return -EINVAL;
+        return simple_xattr_set(__d_xattrs(dentry), name, val, size, flags);
+}
+
+static int cgroup_removexattr(struct dentry *dentry, const char *name)
+{
+        if (!xattr_enabled(dentry))
+                return -EOPNOTSUPP;
+        if (!is_valid_xattr(name))
+                return -EINVAL;
+        return simple_xattr_remove(__d_xattrs(dentry), name);
+}
+
+static ssize_t cgroup_getxattr(struct dentry *dentry, const char *name,
+                               void *buf, size_t size)
+{
+        if (!xattr_enabled(dentry))
+                return -EOPNOTSUPP;
+        if (!is_valid_xattr(name))
+                return -EINVAL;
+        return simple_xattr_get(__d_xattrs(dentry), name, buf, size);
+}
+
+static ssize_t cgroup_listxattr(struct dentry *dentry, char *buf, size_t size)
+{
+        if (!xattr_enabled(dentry))
+                return -EOPNOTSUPP;
+        return simple_xattr_list(__d_xattrs(dentry), buf, size);
+}
+
 static const struct file_operations cgroup_file_operations = {
         .read = cgroup_file_read,
         .write = cgroup_file_write,
@@ -2559,11 +2656,22 @@ static const struct file_operations cgroup_file_operations = {
         .release = cgroup_file_release,
 };
 
+static const struct inode_operations cgroup_file_inode_operations = {
+        .setxattr = cgroup_setxattr,
+        .getxattr = cgroup_getxattr,
+        .listxattr = cgroup_listxattr,
+        .removexattr = cgroup_removexattr,
+};
+
 static const struct inode_operations cgroup_dir_inode_operations = {
         .lookup = cgroup_lookup,
         .mkdir = cgroup_mkdir,
         .rmdir = cgroup_rmdir,
         .rename = cgroup_rename,
+        .setxattr = cgroup_setxattr,
+        .getxattr = cgroup_getxattr,
+        .listxattr = cgroup_listxattr,
+        .removexattr = cgroup_removexattr,
 };
 
 static struct dentry *cgroup_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
@@ -2611,6 +2719,7 @@ static int cgroup_create_file(struct dentry *dentry, umode_t mode,
         } else if (S_ISREG(mode)) {
                 inode->i_size = 0;
                 inode->i_fop = &cgroup_file_operations;
+                inode->i_op = &cgroup_file_inode_operations;
         }
         d_instantiate(dentry, inode);
         dget(dentry);   /* Extra count - pin the dentry in core */
@@ -2671,7 +2780,7 @@ static umode_t cgroup_file_mode(const struct cftype *cft)
 }
 
 static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
-                           const struct cftype *cft)
+                           struct cftype *cft)
 {
         struct dentry *dir = cgrp->dentry;
         struct cgroup *parent = __d_cgrp(dir);
@@ -2681,6 +2790,8 @@ 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 };
 
+        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;
@@ -2721,9 +2832,9 @@ out:
 }
 
 static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
-                              const struct cftype cfts[], bool is_add)
+                              struct cftype cfts[], bool is_add)
 {
-        const struct cftype *cft;
+        struct cftype *cft;
         int err, ret = 0;
 
         for (cft = cfts; cft->name[0] != '\0'; cft++) {
@@ -2757,7 +2868,7 @@ static void cgroup_cfts_prepare(void)
 }
 
 static void cgroup_cfts_commit(struct cgroup_subsys *ss,
-                               const struct cftype *cfts, bool is_add)
+                               struct cftype *cfts, bool is_add)
         __releases(&cgroup_mutex) __releases(&cgroup_cft_mutex)
 {
         LIST_HEAD(pending);
@@ -2808,7 +2919,7 @@ static void cgroup_cfts_commit(struct cgroup_subsys *ss,
  * function currently returns 0 as long as @cfts registration is successful
  * even if some file creation attempts on existing cgroups fail.
  */
-int cgroup_add_cftypes(struct cgroup_subsys *ss, const struct cftype *cfts)
+int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
 {
         struct cftype_set *set;
 
@@ -2838,7 +2949,7 @@ EXPORT_SYMBOL_GPL(cgroup_add_cftypes);
  * Returns 0 on successful unregistration, -ENOENT if @cfts is not
  * registered with @ss.
  */
-int cgroup_rm_cftypes(struct cgroup_subsys *ss, const struct cftype *cfts)
+int cgroup_rm_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
 {
         struct cftype_set *set;
 
@@ -3843,18 +3954,29 @@ static struct cftype files[] = {
         { }     /* terminate */
 };
 
-static int cgroup_populate_dir(struct cgroup *cgrp)
+/**
+ * cgroup_populate_dir - selectively creation of files in a directory
+ * @cgrp: target cgroup
+ * @base_files: true if the base files should be added
+ * @subsys_mask: mask of the subsystem ids whose files should be added
+ */
+static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,
+                               unsigned long subsys_mask)
 {
         int err;
         struct cgroup_subsys *ss;
 
-        err = cgroup_addrm_files(cgrp, NULL, files, true);
-        if (err < 0)
-                return err;
+        if (base_files) {
+                err = cgroup_addrm_files(cgrp, NULL, files, true);
+                if (err < 0)
+                        return err;
+        }
 
         /* process cftsets of each subsystem */
         for_each_subsys(cgrp->root, ss) {
                 struct cftype_set *set;
+                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);
@@ -3988,7 +4110,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
 
         list_add_tail(&cgrp->allcg_node, &root->allcg_list);
 
-        err = cgroup_populate_dir(cgrp);
+        err = cgroup_populate_dir(cgrp, true, root->subsys_mask);
         /* If err < 0, we have a half-filled directory - oh well ;) */
 
         mutex_unlock(&cgroup_mutex);
@@ -4321,8 +4443,7 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
          * since cgroup_init_subsys will have already taken care of it.
          */
         if (ss->module == NULL) {
-                /* a few sanity checks */
-                BUG_ON(ss->subsys_id >= CGROUP_BUILTIN_SUBSYS_COUNT);
+                /* a sanity check */
                 BUG_ON(subsys[ss->subsys_id] != ss);
                 return 0;
         }
@@ -4330,24 +4451,8 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
         /* init base cftset */
         cgroup_init_cftsets(ss);
 
-        /*
-         * need to register a subsys id before anything else - for example,
-         * init_cgroup_css needs it.
-         */
         mutex_lock(&cgroup_mutex);
-        /* find the first empty slot in the array */
-        for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
-                if (subsys[i] == NULL)
-                        break;
-        }
-        if (i == CGROUP_SUBSYS_COUNT) {
-                /* maximum number of subsystems already registered! */
-                mutex_unlock(&cgroup_mutex);
-                return -EBUSY;
-        }
-        /* assign ourselves the subsys_id */
-        ss->subsys_id = i;
-        subsys[i] = ss;
+        subsys[ss->subsys_id] = ss;
 
         /*
          * no ss->create seems to need anything important in the ss struct, so
@@ -4356,7 +4461,7 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
         css = ss->create(dummytop);
         if (IS_ERR(css)) {
                 /* failure case - need to deassign the subsys[] slot. */
-                subsys[i] = NULL;
+                subsys[ss->subsys_id] = NULL;
                 mutex_unlock(&cgroup_mutex);
                 return PTR_ERR(css);
         }
@@ -4372,7 +4477,7 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
                 if (ret) {
                         dummytop->subsys[ss->subsys_id] = NULL;
                         ss->destroy(dummytop);
-                        subsys[i] = NULL;
+                        subsys[ss->subsys_id] = NULL;
                         mutex_unlock(&cgroup_mutex);
                         return ret;
                 }
@@ -4439,7 +4544,6 @@ void cgroup_unload_subsys(struct cgroup_subsys *ss)
 
         mutex_lock(&cgroup_mutex);
         /* deassign the subsys_id */
-        BUG_ON(ss->subsys_id < CGROUP_BUILTIN_SUBSYS_COUNT);
         subsys[ss->subsys_id] = NULL;
 
         /* remove subsystem from rootnode's list of subsystems */
@@ -4502,10 +4606,13 @@ int __init cgroup_init_early(void)
         for (i = 0; i < CSS_SET_TABLE_SIZE; i++)
                 INIT_HLIST_HEAD(&css_set_table[i]);
 
-        /* at bootup time, we don't worry about modular subsystems */
-        for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
+        for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
                 struct cgroup_subsys *ss = subsys[i];
 
+                /* at bootup time, we don't worry about modular subsystems */
+                if (!ss || ss->module)
+                        continue;
+
                 BUG_ON(!ss->name);
                 BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
                 BUG_ON(!ss->create);
@@ -4538,9 +4645,12 @@ int __init cgroup_init(void)
         if (err)
                 return err;
 
-        /* at bootup time, we don't worry about modular subsystems */
-        for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
+        for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
                 struct cgroup_subsys *ss = subsys[i];
+
+                /* at bootup time, we don't worry about modular subsystems */
+                if (!ss || ss->module)
+                        continue;
                 if (!ss->early_init)
                         cgroup_init_subsys(ss);
                 if (ss->use_id)
@@ -4735,13 +4845,16 @@ void cgroup_fork_callbacks(struct task_struct *child)
 {
         if (need_forkexit_callback) {
                 int i;
-                /*
-                 * forkexit callbacks are only supported for builtin
-                 * subsystems, and the builtin section of the subsys array is
-                 * immutable, so we don't need to lock the subsys array here.
-                 */
-                for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
+                for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
                         struct cgroup_subsys *ss = subsys[i];
+
+                        /*
+                         * forkexit callbacks are only supported for
+                         * builtin subsystems.
+                         */
+                        if (!ss || ss->module)
+                                continue;
+
                         if (ss->fork)
                                 ss->fork(child);
                 }
@@ -4846,12 +4959,13 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks)
         tsk->cgroups = &init_css_set;
 
         if (run_callbacks && need_forkexit_callback) {
-                /*
-                 * modular subsystems can't use callbacks, so no need to lock
-                 * the subsys array
-                 */
-                for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
+                for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
                         struct cgroup_subsys *ss = subsys[i];
+
+                        /* modular subsystems can't use callbacks */
+                        if (!ss || ss->module)
+                                continue;
+
                         if (ss->exit) {
                                 struct cgroup *old_cgrp =
                                         rcu_dereference_raw(cg->subsys[i])->cgroup;
@@ -5037,13 +5151,17 @@ static int __init cgroup_disable(char *str)
         while ((token = strsep(&str, ",")) != NULL) {
                 if (!*token)
                         continue;
-                /*
-                 * cgroup_disable, being at boot time, can't know about module
-                 * subsystems, so we don't worry about them.
-                 */
-                for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
+                for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
                         struct cgroup_subsys *ss = subsys[i];
 
+                        /*
+                         * cgroup_disable, being at boot time, can't
+                         * know about module subsystems, so we don't
+                         * worry about them.
+                         */
+                        if (!ss || ss->module)
+                                continue;
+
                         if (!strcmp(token, ss->name)) {
                                 ss->disabled = 1;
                                 printk(KERN_INFO "Disabling %s control group"