Merge branch 'for-3.10-fixes' into for-3.11

Merging to receive 7805d000db ("cgroup: fix a subtle bug in descendant
pre-order walk") so that further iterator updates can build upon it.

Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 8bda1294c035b24912a3da178ebc2c8e1cd5f827..1df5f699be615a82be9089df82b783413c9d47f0 100644 (file)
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -542,6 +542,8 @@ int cgroup_is_removed(const struct cgroup *cgrp);
 bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor);
 
 int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen);
+int task_cgroup_path_from_hierarchy(struct task_struct *task, int hierarchy_id,
+                                   char *buf, size_t buflen);
 
 int cgroup_task_count(const struct cgroup *cgrp);
 
@@ -838,8 +840,6 @@ static inline void cgroup_fork(struct task_struct *p) {}
 static inline void cgroup_post_fork(struct task_struct *p) {}
 static inline void cgroup_exit(struct task_struct *p, int callbacks) {}
 
-static inline void cgroup_lock(void) {}
-static inline void cgroup_unlock(void) {}
 static inline int cgroupstats_build(struct cgroupstats *stats,
                                        struct dentry *dentry)
 {

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 31e9ef3190709da16828f8f11bf55b3d45f71af8..a19419f4af1a419d0c91faad08d8ffd9ae649e1c 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -189,9 +189,12 @@ struct cgroup_event {
 static LIST_HEAD(roots);
 static int root_count;
 
-static DEFINE_IDA(hierarchy_ida);
-static int next_hierarchy_id;
-static DEFINE_SPINLOCK(hierarchy_id_lock);
+/*
+ * Hierarchy ID allocation and mapping.  It follows the same exclusion
+ * rules as other root ops - both cgroup_mutex and cgroup_root_mutex for
+ * writes, either for reads.
+ */
+static DEFINE_IDR(cgroup_hierarchy_idr);
 
 /* dummytop is a shorthand for the dummy hierarchy's top cgroup */
 #define dummytop (&rootnode.top_cgroup)
@@ -1426,29 +1429,30 @@ static void init_cgroup_root(struct cgroupfs_root *root)
        list_add_tail(&cgrp->allcg_node, &root->allcg_list);
 }
 
-static bool init_root_id(struct cgroupfs_root *root)
+static int cgroup_init_root_id(struct cgroupfs_root *root)
 {
-       int ret = 0;
+       int id;
 
-       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;
+       lockdep_assert_held(&cgroup_mutex);
+       lockdep_assert_held(&cgroup_root_mutex);
+
+       id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, 2, 0, GFP_KERNEL);
+       if (id < 0)
+               return id;
+
+       root->hierarchy_id = id;
+       return 0;
+}
+
+static void cgroup_exit_root_id(struct cgroupfs_root *root)
+{
+       lockdep_assert_held(&cgroup_mutex);
+       lockdep_assert_held(&cgroup_root_mutex);
+
+       if (root->hierarchy_id) {
+               idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
+               root->hierarchy_id = 0;
+       }
 }
 
 static int cgroup_test_super(struct super_block *sb, void *data)
@@ -1482,10 +1486,6 @@ static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
        if (!root)
                return ERR_PTR(-ENOMEM);
 
-       if (!init_root_id(root)) {
-               kfree(root);
-               return ERR_PTR(-ENOMEM);
-       }
        init_cgroup_root(root);
 
        root->subsys_mask = opts->subsys_mask;
@@ -1500,17 +1500,15 @@ static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
        return root;
 }
 
-static void cgroup_drop_root(struct cgroupfs_root *root)
+static void cgroup_free_root(struct cgroupfs_root *root)
 {
-       if (!root)
-               return;
+       if (root) {
+               /* hierarhcy ID shoulid already have been released */
+               WARN_ON_ONCE(root->hierarchy_id);
 
-       BUG_ON(!root->hierarchy_id);
-       spin_lock(&hierarchy_id_lock);
-       ida_remove(&hierarchy_ida, root->hierarchy_id);
-       spin_unlock(&hierarchy_id_lock);
-       ida_destroy(&root->cgroup_ida);
-       kfree(root);
+               ida_destroy(&root->cgroup_ida);
+               kfree(root);
+       }
 }
 
 static int cgroup_set_super(struct super_block *sb, void *data)
@@ -1597,7 +1595,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
        sb = sget(fs_type, cgroup_test_super, cgroup_set_super, 0, &opts);
        if (IS_ERR(sb)) {
                ret = PTR_ERR(sb);
-               cgroup_drop_root(opts.new_root);
+               cgroup_free_root(opts.new_root);
                goto drop_modules;
        }
 
@@ -1641,6 +1639,10 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
                if (ret)
                        goto unlock_drop;
 
+               ret = cgroup_init_root_id(root);
+               if (ret)
+                       goto unlock_drop;
+
                ret = rebind_subsystems(root, root->subsys_mask);
                if (ret == -EBUSY) {
                        free_cg_links(&tmp_cg_links);
@@ -1684,7 +1686,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
                 * We re-used an existing hierarchy - the new root (if
                 * any) is not needed
                 */
-               cgroup_drop_root(opts.new_root);
+               cgroup_free_root(opts.new_root);
 
                if (((root->flags | opts.flags) & CGRP_ROOT_SANE_BEHAVIOR) &&
                    root->flags != opts.flags) {
@@ -1702,6 +1704,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
        return dget(sb->s_root);
 
  unlock_drop:
+       cgroup_exit_root_id(root);
        mutex_unlock(&cgroup_root_mutex);
        mutex_unlock(&cgroup_mutex);
        mutex_unlock(&inode->i_mutex);
@@ -1754,13 +1757,15 @@ static void cgroup_kill_sb(struct super_block *sb) {
                root_count--;
        }
 
+       cgroup_exit_root_id(root);
+
        mutex_unlock(&cgroup_root_mutex);
        mutex_unlock(&cgroup_mutex);
 
        simple_xattrs_free(&cgrp->xattrs);
 
        kill_litter_super(sb);
-       cgroup_drop_root(root);
+       cgroup_free_root(root);
 }
 
 static struct file_system_type cgroup_fs_type = {
@@ -1822,6 +1827,38 @@ out:
 }
 EXPORT_SYMBOL_GPL(cgroup_path);
 
+/**
+ * task_cgroup_path_from_hierarchy - cgroup path of a task on a hierarchy
+ * @task: target task
+ * @hierarchy_id: the hierarchy to look up @task's cgroup from
+ * @buf: the buffer to write the path into
+ * @buflen: the length of the buffer
+ *
+ * Determine @task's cgroup on the hierarchy specified by @hierarchy_id and
+ * copy its path into @buf.  This function grabs cgroup_mutex and shouldn't
+ * be used inside locks used by cgroup controller callbacks.
+ */
+int task_cgroup_path_from_hierarchy(struct task_struct *task, int hierarchy_id,
+                                   char *buf, size_t buflen)
+{
+       struct cgroupfs_root *root;
+       struct cgroup *cgrp = NULL;
+       int ret = -ENOENT;
+
+       mutex_lock(&cgroup_mutex);
+
+       root = idr_find(&cgroup_hierarchy_idr, hierarchy_id);
+       if (root) {
+               cgrp = task_cgroup_from_root(task, root);
+               ret = cgroup_path(cgrp, buf, buflen);
+       }
+
+       mutex_unlock(&cgroup_mutex);
+
+       return ret;
+}
+EXPORT_SYMBOL_GPL(task_cgroup_path_from_hierarchy);
+
 /*
  * Control Group taskset
  */
@@ -4640,7 +4677,15 @@ int __init cgroup_init(void)
        /* Add init_css_set to the hash table */
        key = css_set_hash(init_css_set.subsys);
        hash_add(css_set_table, &init_css_set.hlist, key);
-       BUG_ON(!init_root_id(&rootnode));
+
+       /* allocate id for the dummy hierarchy */
+       mutex_lock(&cgroup_mutex);
+       mutex_lock(&cgroup_root_mutex);
+
+       BUG_ON(cgroup_init_root_id(&rootnode));
+
+       mutex_unlock(&cgroup_root_mutex);
+       mutex_unlock(&cgroup_mutex);
 
        cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj);
        if (!cgroup_kobj) {