1 files changed, 99 insertions, 59 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 8ba680985335..14efffed72c8 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -49,6 +49,7 @@
 #include <linux/namei.h>
 #include <linux/smp_lock.h>
 #include <linux/pid_namespace.h>
+#include <linux/idr.h>
 
 #include <asm/atomic.h>
 
@@ -77,6 +78,9 @@ struct cgroupfs_root {
          */
         unsigned long subsys_bits;
 
+        /* Unique id for this hierarchy. */
+        int hierarchy_id;
+
         /* The bitmask of subsystems currently attached to this hierarchy */
         unsigned long actual_subsys_bits;
 
@@ -147,6 +151,10 @@ struct css_id {
 static LIST_HEAD(roots);
 static int root_count;
 
+static DEFINE_IDA(hierarchy_ida);
+static int next_hierarchy_id;
+static DEFINE_SPINLOCK(hierarchy_id_lock);
+
 /* dummytop is a shorthand for the dummy hierarchy's top cgroup */
 #define dummytop (&rootnode.top_cgroup)
 
@@ -264,42 +272,10 @@ static struct hlist_head *css_set_hash(struct cgroup_subsys_state *css[])
  * compiled into their kernel but not actually in use */
 static int use_task_css_set_links __read_mostly;
 
-/* When we create or destroy a css_set, the operation simply
- * takes/releases a reference count on all the cgroups referenced
- * by subsystems in this css_set. This can end up multiple-counting
- * some cgroups, but that's OK - the ref-count is just a
- * busy/not-busy indicator; ensuring that we only count each cgroup
- * once would require taking a global lock to ensure that no
- * subsystems moved between hierarchies while we were doing so.
- *
- * Possible TODO: decide at boot time based on the number of
- * registered subsystems and the number of CPUs or NUMA nodes whether
- * it's better for performance to ref-count every subsystem, or to
- * take a global lock and only add one ref count to each hierarchy.
- */
-
-/*
- * unlink a css_set from the list and free it
- */
-static void unlink_css_set(struct css_set *cg)
+static void __put_css_set(struct css_set *cg, int taskexit)
 {
         struct cg_cgroup_link *link;
         struct cg_cgroup_link *saved_link;
-
-        hlist_del(&cg->hlist);
-        css_set_count--;
-
-        list_for_each_entry_safe(link, saved_link, &cg->cg_links,
-                                 cg_link_list) {
-                list_del(&link->cg_link_list);
-                list_del(&link->cgrp_link_list);
-                kfree(link);
-        }
-}
-
-static void __put_css_set(struct css_set *cg, int taskexit)
-{
-        int i;
         /*
          * Ensure that the refcount doesn't hit zero while any readers
          * can see it. Similar to atomic_dec_and_lock(), but for an
@@ -312,20 +288,27 @@ static void __put_css_set(struct css_set *cg, int taskexit)
                 write_unlock(&css_set_lock);
                 return;
         }
-        unlink_css_set(cg);
-        write_unlock(&css_set_lock);
 
-        rcu_read_lock();
-        for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
-                struct cgroup *cgrp = rcu_dereference(cg->subsys[i]->cgroup);
+        /* This css_set is dead. unlink it and release cgroup refcounts */
+        hlist_del(&cg->hlist);
+        css_set_count--;
+
+        list_for_each_entry_safe(link, saved_link, &cg->cg_links,
+                                 cg_link_list) {
+                struct cgroup *cgrp = link->cgrp;
+                list_del(&link->cg_link_list);
+                list_del(&link->cgrp_link_list);
                 if (atomic_dec_and_test(&cgrp->count) &&
                     notify_on_release(cgrp)) {
                         if (taskexit)
                                 set_bit(CGRP_RELEASABLE, &cgrp->flags);
                         check_for_release(cgrp);
                 }
+
+                kfree(link);
         }
-        rcu_read_unlock();
+
+        write_unlock(&css_set_lock);
         kfree(cg);
 }
 
@@ -519,6 +502,7 @@ static void link_css_set(struct list_head *tmp_cg_links,
                                 cgrp_link_list);
         link->cg = cg;
         link->cgrp = cgrp;
+        atomic_inc(&cgrp->count);
         list_move(&link->cgrp_link_list, &cgrp->css_sets);
         /*
          * Always add links to the tail of the list so that the list
@@ -539,7 +523,6 @@ static struct css_set *find_css_set(
 {
         struct css_set *res;
         struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];
-        int i;
 
         struct list_head tmp_cg_links;
 
@@ -578,10 +561,6 @@ static struct css_set *find_css_set(
 
         write_lock(&css_set_lock);
         /* Add reference counts and links from the new css_set. */
-        for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
-                struct cgroup *cgrp = res->subsys[i]->cgroup;
-                atomic_inc(&cgrp->count);
-        }
         list_for_each_entry(link, &oldcg->cg_links, cg_link_list) {
                 struct cgroup *c = link->cgrp;
                 if (c->root == cgrp->root)
@@ -972,8 +951,11 @@ struct cgroup_sb_opts {
         unsigned long flags;
         char *release_agent;
         char *name;
+        /* User explicitly requested empty subsystem */
+        bool none;
 
         struct cgroupfs_root *new_root;
+
 };
 
 /* Convert a hierarchy specifier into a bitmask of subsystems and
@@ -1002,6 +984,9 @@ static int parse_cgroupfs_options(char *data,
                                 if (!ss->disabled)
                                         opts->subsys_bits |= 1ul << i;
                         }
+                } else if (!strcmp(token, "none")) {
+                        /* Explicitly have no subsystems */
+                        opts->none = true;
                 } else if (!strcmp(token, "noprefix")) {
                         set_bit(ROOT_NOPREFIX, &opts->flags);
                 } else if (!strncmp(token, "release_agent=", 14)) {
@@ -1051,6 +1036,8 @@ static int parse_cgroupfs_options(char *data,
                 }
         }
 
+        /* Consistency checks */
+
         /*
          * Option noprefix was introduced just for backward compatibility
          * with the old cpuset, so we allow noprefix only if mounting just
@@ -1060,7 +1047,15 @@ static int parse_cgroupfs_options(char *data,
             (opts->subsys_bits & mask))
                 return -EINVAL;
 
-        /* We can't have an empty hierarchy */
+
+        /* Can't specify "none" and some subsystems */
+        if (opts->subsys_bits && 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)
                 return -EINVAL;
 
@@ -1141,6 +1136,31 @@ static void init_cgroup_root(struct cgroupfs_root *root)
         init_cgroup_housekeeping(cgrp);
 }
 
+static bool init_root_id(struct cgroupfs_root *root)
+{
+        int ret = 0;
+
+        do {
+                if (!ida_pre_get(&hierarchy_ida, GFP_KERNEL))
+                        return false;
+                spin_lock(&hierarchy_id_lock);
+                /* Try to allocate the next unused ID */
+                ret = ida_get_new_above(&hierarchy_ida, next_hierarchy_id,
+                                        &root->hierarchy_id);
+                if (ret == -ENOSPC)
+                        /* Try again starting from 0 */
+                        ret = ida_get_new(&hierarchy_ida, &root->hierarchy_id);
+                if (!ret) {
+                        next_hierarchy_id = root->hierarchy_id + 1;
+                } else if (ret != -EAGAIN) {
+                        /* Can only get here if the 31-bit IDR is full ... */
+                        BUG_ON(ret);
+                }
+                spin_unlock(&hierarchy_id_lock);
+        } while (ret);
+        return true;
+}
+
 static int cgroup_test_super(struct super_block *sb, void *data)
 {
         struct cgroup_sb_opts *opts = data;
@@ -1150,8 +1170,12 @@ static int cgroup_test_super(struct super_block *sb, void *data)
         if (opts->name && strcmp(opts->name, root->name))
                 return 0;
 
-        /* If we asked for subsystems then they must match */
-        if (opts->subsys_bits && (opts->subsys_bits != root->subsys_bits))
+        /*
+         * 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))
                 return 0;
 
         return 1;
@@ -1161,15 +1185,19 @@ static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
 {
         struct cgroupfs_root *root;
 
-        /* Empty hierarchies aren't supported */
-        if (!opts->subsys_bits)
+        if (!opts->subsys_bits && !opts->none)
                 return NULL;
 
         root = kzalloc(sizeof(*root), GFP_KERNEL);
         if (!root)
                 return ERR_PTR(-ENOMEM);
 
+        if (!init_root_id(root)) {
+                kfree(root);
+                return ERR_PTR(-ENOMEM);
+        }
         init_cgroup_root(root);
+
         root->subsys_bits = opts->subsys_bits;
         root->flags = opts->flags;
         if (opts->release_agent)
@@ -1179,6 +1207,18 @@ static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
         return root;
 }
 
+static void cgroup_drop_root(struct cgroupfs_root *root)
+{
+        if (!root)
+                return;
+
+        BUG_ON(!root->hierarchy_id);
+        spin_lock(&hierarchy_id_lock);
+        ida_remove(&hierarchy_ida, root->hierarchy_id);
+        spin_unlock(&hierarchy_id_lock);
+        kfree(root);
+}
+
 static int cgroup_set_super(struct super_block *sb, void *data)
 {
         int ret;
@@ -1188,7 +1228,7 @@ static int cgroup_set_super(struct super_block *sb, void *data)
         if (!opts->new_root)
                 return -EINVAL;
 
-        BUG_ON(!opts->subsys_bits);
+        BUG_ON(!opts->subsys_bits && !opts->none);
 
         ret = set_anon_super(sb, NULL);
         if (ret)
@@ -1257,7 +1297,7 @@ static int cgroup_get_sb(struct file_system_type *fs_type,
         sb = sget(fs_type, cgroup_test_super, cgroup_set_super, &opts);
         if (IS_ERR(sb)) {
                 ret = PTR_ERR(sb);
-                kfree(opts.new_root);
+                cgroup_drop_root(opts.new_root);
                 goto out_err;
         }
 
@@ -1351,7 +1391,7 @@ static int cgroup_get_sb(struct file_system_type *fs_type,
                  * We re-used an existing hierarchy - the new root (if
                  * any) is not needed
                  */
-                kfree(opts.new_root);
+                cgroup_drop_root(opts.new_root);
         }
 
         simple_set_mnt(mnt, sb);
@@ -1410,7 +1450,7 @@ static void cgroup_kill_sb(struct super_block *sb) {
         mutex_unlock(&cgroup_mutex);
 
         kill_litter_super(sb);
-        kfree(root);
+        cgroup_drop_root(root);
 }
 
 static struct file_system_type cgroup_fs_type = {
@@ -3109,7 +3149,7 @@ int __init cgroup_init(void)
         /* Add init_css_set to the hash table */
         hhead = css_set_hash(init_css_set.subsys);
         hlist_add_head(&init_css_set.hlist, hhead);
-
+        BUG_ON(!init_root_id(&rootnode));
         err = register_filesystem(&cgroup_fs_type);
         if (err < 0)
                 goto out;
@@ -3164,7 +3204,7 @@ static int proc_cgroup_show(struct seq_file *m, void *v)
                 struct cgroup *cgrp;
                 int count = 0;
 
-                seq_printf(m, "%lu:", root->subsys_bits);
+                seq_printf(m, "%d:", root->hierarchy_id);
                 for_each_subsys(root, ss)
                         seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
                 if (strlen(root->name))
@@ -3210,8 +3250,8 @@ static int proc_cgroupstats_show(struct seq_file *m, void *v)
         mutex_lock(&cgroup_mutex);
         for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
                 struct cgroup_subsys *ss = subsys[i];
-                seq_printf(m, "%s\t%lu\t%d\t%d\n",
-                           ss->name, ss->root->subsys_bits,
+                seq_printf(m, "%s\t%d\t%d\t%d\n",
+                           ss->name, ss->root->hierarchy_id,
                            ss->root->number_of_cgroups, !ss->disabled);
         }
         mutex_unlock(&cgroup_mutex);
@@ -3929,8 +3969,8 @@ static int current_css_set_cg_links_read(struct cgroup *cont,
                         name = c->dentry->d_name.name;
                 else
                         name = "?";
-                seq_printf(seq, "Root %lu group %s\n",
-                           c->root->subsys_bits, name);
+                seq_printf(seq, "Root %d group %s\n",
+                           c->root->hierarchy_id, name);
         }
         rcu_read_unlock();
         read_unlock(&css_set_lock);