Re: [PATCH 3/7] containers (V7): Add generic multi-subsystem API to containers

Serge E. Hallyn
2007-02-12T15:40:08Z

Quoting menage@google.com (menage@google.com):
> This patch removes all cpuset-specific knowlege from the container
> system, replacing it with a generic API that can be used by multiple
> subsystems. Cpusets is adapted to be a container subsystem.
>
> Signed-off-by: Paul Menage <menage@google.com>
>
> ---
> Documentation/containers.txt | 415 +++++++++--
> Documentation/cpusets.txt | 20
> include/linux/container.h | 178 ++++
> include/linux/cpuset.h | 16
> include/linux/mempolicy.h | 12
> include/linux/sched.h | 4
> init/Kconfig | 12
> kernel/container.c | 1601 ++++++++++++++++++++++++++++++-------------
> kernel/cpuset.c | 170 ++--
> mm/mempolicy.c | 2
> 10 files changed, 1808 insertions(+), 622 deletions(-)
>
> Index: container-2.6.20/include/linux/container.h
> ===================================================================
> --- container-2.6.20.orig/include/linux/container.h
> +++ container-2.6.20/include/linux/container.h
> @@ -9,13 +9,12 @@
> */
>
> #include <linux/sched.h>
> +#include <linux/kref.h>
> #include <linux/cpumask.h>
> #include <linux/nodemask.h>
>
> #ifdef CONFIG_CONTAINERS
>
> -extern int number_of_containers; /* How many containers are defined in system? */
> -
> extern int container_init_early(void);
> extern int container_init(void);
> extern void container_init_smp(void);
> @@ -30,13 +29,105 @@ extern void container_unlock(void);
> extern void container_manage_lock(void);
> extern void container_manage_unlock(void);
>
> +struct containerfs_root;
> +
> +/* Per-subsystem/per-container state maintained by the system. */
> +struct container_subsys_state {
> + /* The container that this subsystem is attached to. Useful
> + * for subsystems that want to know about the container
> + * hierarchy structure */
> + struct container *container;
> +
> + /* State maintained by the container system to allow
> + * subsystems to be "busy". Should be accessed via css_get()
> + * and css_put() */
> + spinlock_t refcnt_lock;
> + atomic_t refcnt;
> +};
> +
> +/* A container_group is a structure holding pointers to a set of
> + * containers. This saves space in the task struct object and speeds
> + * up fork()/exit(), since a single inc/dec can bump the reference
> + * count on the entire container set for a task. */
> +
> +struct container_group {
> +
> + /* Reference count */
> + struct kref ref;
> +
> + /* List running through all container groups */
> + struct list_head list;
> +
> + /* Set of containers, one for each hierarchy. These are
> + * immutable once the container group has been created */
> + struct container *container[CONFIG_MAX_CONTAINER_HIERARCHIES];
> +
> + /* Set of subsystem states, one for each subsystem. NULL for
> + * subsystems that aren't part of this hierarchy. These
> + * pointers reduce the number of dereferences required to get
> + * from a task to its state for a given container, but result
> + * in increased space usage if tasks are in wildly different
> + * groupings across different hierarchies. This array is
> + * mostly immutable after creation - a newly registered
> + * subsystem can result in a pointer in this array
> + * transitioning from NULL to non-NULL */
> + struct container_subsys_state *subsys[CONFIG_MAX_CONTAINER_SUBSYS];
> +};
> +
> +/*
> + * Call css_get() to hold a reference on the container; following a
> + * return of 0, this container subsystem state object is guaranteed
> + * not to be destroyed until css_put() is called on it. A non-zero
> + * return code indicates that a reference could not be taken.
> + *
> + */
> +
> +static inline int css_get(struct container_subsys_state *css)
> +{
> + int retval = 0;
> + unsigned long flags;
> + /* Synchronize with container_rmdir() */
> + spin_lock_irqsave(&css->refcnt_lock, flags);
> + if (atomic_read(&css->refcnt) >= 0) {
> + /* Container is still alive */
> + atomic_inc(&css->refcnt);
> + } else {
> + /* Container removal is in progress */
> + retval = -EINVAL;
> + }
> + spin_unlock_irqrestore(&css->refcnt_lock, flags);
> + return retval;
> +}
> +
> +/*
> + * If you are holding current->alloc_lock then it's impossible for you
> + * to be moved out of your container, and hence it's impossible for
> + * your container to be destroyed. Therefore doing a simple
> + * atomic_inc() on a css is safe.
> + */
> +
> +static inline void css_get_current(struct container_subsys_state *css)
> +{
> + atomic_inc(&css->refcnt);
> +}
> +
> +/*
> + * css_put() should be called to release a reference taken by
> + * css_get() or css_get_current()
> + */
> +
> +static inline void css_put(struct container_subsys_state *css) {
> + atomic_dec(&css->refcnt);
> +}
> +
> struct container {
> unsigned long flags; /* "unsigned long" so bitops work */
>
> /*
> * Count is atomic so can incr (fork) or decr (exit) without a lock.
> */
> - atomic_t count; /* count tasks using this container */
> + atomic_t count; /* count of container groups
> + * using this container*/
>
> /*
> * We link our 'sibling' struct into our parent's 'children'.
> @@ -46,11 +137,15 @@ struct container {
> struct list_head children; /* my children */
>
> struct container *parent; /* my parent */
> - struct dentry *dentry; /* container fs entry */
> + struct dentry *dentry; /* container fs entry */
>
> -#ifdef CONFIG_CPUSETS
> - struct cpuset *cpuset;
> -#endif
> + /* Private pointers for each registered subsystem */
> + struct container_subsys_state *subsys[CONFIG_MAX_CONTAINER_SUBSYS];
> +
> + int hierarchy;
> +
> + struct containerfs_root *root;
> + struct container *top_container;
> };
>
> /* struct cftype:
> @@ -67,8 +162,11 @@ struct container {
> */
>
> struct inode;
> +#define MAX_CFTYPE_NAME 64
> struct cftype {
> - char *name;
> + /* By convention, the name should begin with the name of the
> + * subsystem, followed by a period */
> + char name[MAX_CFTYPE_NAME];
> int private;
> int (*open) (struct inode *inode, struct file *file);
> ssize_t (*read) (struct container *cont, struct cftype *cft,
> @@ -80,10 +178,72 @@ struct cftype {
> int (*release) (struct inode *inode, struct file *file);
> };
>
> +/* Add a new file to the given container directory. Should only be
> + * called by subsystems from within a populate() method */
> int container_add_file(struct container *cont, const struct cftype *cft);
>
> int container_is_removed(const struct container *cont);
> -void container_set_release_agent_path(const char *path);
> +
> +int container_path(const struct container *cont, char *buf, int buflen);
> +
> +int container_task_count(const struct container *cont);
> +
> +/* Return true if the container is a descendant of the current container */
> +int container_is_descendant(const struct container *cont);
> +
> +/* Container subsystem type. See Documentation/containers.txt for details */
> +
> +struct container_subsys {
> + int (*create)(struct container_subsys *ss,
> + struct container *cont);
> + void (*destroy)(struct container_subsys *ss, struct container *cont);
> + int (*can_attach)(struct container_subsys *ss,
> + struct container *cont, struct task_struct *tsk);
> + void (*attach)(struct container_subsys *ss, struct container *cont,
> + struct container *old_cont, struct task_struct *tsk);
> + void (*post_attach)(struct container_subsys *ss,
> + struct container *cont,
> + struct container *old_cont,
> + struct task_struct *tsk);
> + void (*fork)(struct container_subsys *ss, struct task_struct *task);
> + void (*exit)(struct container_subsys *ss, struct task_struct *task);
> + int (*populate)(struct container_subsys *ss,
> + struct container *cont);
> + void (*bind)(struct container_subsys *ss, struct container *root);
> + int subsys_id;
> + int active;
> +
> +#define MAX_CONTAINER_TYPE_NAMELEN 32
> + const char *name;
> +
> + /* Protected by RCU */
> + int hierarchy;
> +
> + struct list_head sibling;
> +};
> +
> +int container_register_subsys(struct container_subsys *subsys);
> +int container_clone(struct task_struct *tsk, struct container_subsys *ss);
> +
> +static inline struct container_subsys_state *container_subsys_state(
> + struct container *cont,
> + struct container_subsys *ss)
> +{
> + return cont->subsys[ss->subsys_id];
> +}
> +
> +static inline struct container* task_container(struct task_struct *task,
> + struct container_subsys *ss)
> +{
> + return rcu_dereference(task->containers->container[ss->hierarchy]);
> +}
> +
> +static inline struct container_subsys_state *task_subsys_state(
> + struct task_struct *task,
> + struct container_subsys *ss)
> +{
> + return rcu_dereference(task->containers->subsys[ss->subsys_id]);
> +}
>
> int container_path(const struct container *cont, char *buf, int buflen);
>
> Index: container-2.6.20/include/linux/cpuset.h
> ===================================================================
> --- container-2.6.20.orig/include/linux/cpuset.h
> +++ container-2.6.20/include/linux/cpuset.h
> @@ -70,16 +70,7 @@ static inline int cpuset_do_slab_mem_spr
>
> extern void cpuset_track_online_nodes(void);
>
> -extern int cpuset_can_attach_task(struct container *cont,
> - struct task_struct *tsk);
> -extern void cpuset_attach_task(struct container *cont,
> - struct task_struct *tsk);
> -extern void cpuset_post_attach_task(struct container *cont,
> - struct container *oldcont,
> - struct task_struct *tsk);
> -extern int cpuset_populate_dir(struct container *cont);
> -extern int cpuset_create(struct container *cont);
> -extern void cpuset_destroy(struct container *cont);
> +extern int current_cpuset_is_being_rebound(void);
>
> #else /* !CONFIG_CPUSETS */
>
> @@ -147,6 +138,11 @@ static inline int cpuset_do_slab_mem_spr
>
> static inline void cpuset_track_online_nodes(void) {}
>
> +static inline int current_cpuset_is_being_rebound(void)
> +{
> + return 0;
> +}
> +
> #endif /* !CONFIG_CPUSETS */
>
> #endif /* _LINUX_CPUSET_H */
> Index: container-2.6.20/kernel/container.c
> ===================================================================
> --- container-2.6.20.orig/kernel/container.c
> +++ container-2.6.20/kernel/container.c
> @@ -55,7 +55,6 @@
> #include <linux/time.h>
> #include <linux/backing-dev.h>
> #include <linux/sort.h>
> -#include <linux/cpuset.h>
>
> #include <asm/uaccess.h>
> #include <asm/atomic.h>
> @@ -63,17 +62,56 @@
>
> #define CONTAINER_SUPER_MAGIC 0x27e0eb
>
> -/*
> - * Tracks how many containers are currently defined in system.
> - * When there is only one container (the root container) we can
> - * short circuit some hooks.
> +static struct container_subsys *subsys[CONFIG_MAX_CONTAINER_SUBSYS];
> +static int subsys_count = 0;
> +
> +/* A containerfs_root represents the root of a container hierarchy,
> + * and may be associated with a superblock to form an active
> + * hierarchy */
> +struct containerfs_root {
> + struct super_block *sb;
> +
> + /* The bitmask of subsystems attached to this hierarchy */
> + unsigned long subsys_bits;
> +
> + /* A list running through the attached subsystems */
> + struct list_head subsys_list;
> +
> + /* The root container for this hierarchy */
> + struct container top_container;
> +
> + /* Tracks how many containers are currently defined in hierarchy.*/
> + int number_of_containers;
> +
> +};
> +
> +/* The set of hierarchies in use. Hierarchy 0 is the "dummy
> + * container", reserved for the subsystems that are otherwise
> + * unattached - it never has more than a single container, and all
> + * tasks are part of that container. */
> +
> +static struct containerfs_root rootnode[CONFIG_MAX_CONTAINER_HIERARCHIES];
> +
> +/* dummytop is a shorthand for the dummy hierarchy's top container */
> +#define dummytop (&rootnode[0].top_container)
> +
> +/* This flag indicates whether tasks in the fork and exit paths should
> + * take callback_mutex and check for fork/exit handlers to call. This
> + * avoids us having to take locks in the fork/exit path if none of the
> + * subsystems need to be called.
> + *
> + * It is protected via RCU, with the invariant that a process in an
> + * rcu_read_lock() section will never see this as 0 if there are
> + * actually registered subsystems with a fork or exit
> + * handler. (Sometimes it may be 1 without there being any registered
> + * subsystems with such a handler, but such periods are safe and of
> + * short duration).
> */
> -int number_of_containers __read_mostly;
> +static int need_forkexit_callback = 0;
>
> /* bits in struct container flags field */
> typedef enum {
> CONT_REMOVED,
> - CONT_NOTIFY_ON_RELEASE,
> } container_flagbits_t;
>
> /* convenient tests for these bits */
> @@ -82,31 +120,144 @@ inline int container_is_removed(const st
> return test_bit(CONT_REMOVED, &cont->flags);
> }
>
> -static inline int notify_on_release(const struct container *cont)
> -{
> - return test_bit(CONT_NOTIFY_ON_RELEASE, &cont->flags);
> +/* for_each_subsys() allows you to act on each subsystem attached to
> + * an active hierarchy */
> +#define for_each_subsys(_hierarchy, _ss) \
> +list_for_each_entry(_ss, &rootnode[_hierarchy].subsys_list, sibling)
> +
> +/* The default container group - used by init and its children prior
> + * to any hierarchies being mounted. It contains a pointer to the top
> + * container in each hierarchy. Also used to anchor the list of
> + * container groups */
> +static struct container_group init_container_group;
> +static DEFINE_SPINLOCK(container_group_lock);
> +static int container_group_count;
> +
> +static void release_container_group(struct kref *k) {
> + struct container_group *cg =
> + container_of(k, struct container_group, ref);
> + int i;
> + spin_lock(&container_group_lock);
> + /* Release reference counts on all the containers pointed to
> + * by this container_group */
> + for (i = 0; i < CONFIG_MAX_CONTAINER_HIERARCHIES; i++) {
> + struct container *cont = cg->container[i];
> + if (!cont) continue;
> + atomic_dec(&cont->count);
> + }
> + list_del(&cg->list);
> + container_group_count--;
> + spin_unlock(&container_group_lock);
> + kfree(cg);
> }
>
> -static struct container top_container = {
> - .count = ATOMIC_INIT(0),
> - .sibling = LIST_HEAD_INIT(top_container.sibling),
> - .children = LIST_HEAD_INIT(top_container.children),
> -};
> +static inline void get_container_group(struct container_group *cg) {
> + kref_get(&cg->ref);
> +}
>
> -/* The path to use for release notifications. No locking between
> - * setting and use - so if userspace updates this while subcontainers
> - * exist, you could miss a notification */
> -static char release_agent_path[PATH_MAX] = "/sbin/container_release_agent";
> +static inline void put_container_group(struct container_group *cg) {
> + kref_put(&cg->ref, release_container_group);
> +}
>
> -void container_set_release_agent_path(const char *path)
> -{
> - container_manage_lock();
> - strcpy(release_agent_path, path);
> - container_manage_unlock();
> +/*
> + * find_existing_container_group() is a helper for
> + * find_container_group(), and checks to see whether an existing
> + * container_group is suitable. This currently walks a linked-list for
> + * simplicity; a later patch will use a hash table for better
> + * performance
> + */
> +
> +static struct container_group *find_existing_container_group(
> + struct container_group *oldcg,
> + struct container *cont)
> +{
> + int h = cont->hierarchy;
> + struct list_head *l = &init_container_group.list;
> + do {
> + int i;
> + struct container_group *cg =
> + list_entry(l, struct container_group, list);
> +
> + /* A container matches what we want if its container
> + * set is the same as "oldcg", except for the
> + * hierarchy for "cont" which should match "cont" */
> + for (i = 0; i < CONFIG_MAX_CONTAINER_HIERARCHIES; i++) {
> + if (i == h) {
> + if (cg->container[i] != cont)
> + break;
> + } else {
> + if (cg->container[i] != oldcg->container[i])
> + break;
> + }
> + }
> + if (i == CONFIG_MAX_CONTAINER_HIERARCHIES) {
> + /* All hierarchies matched what we want - success */
> + return cg;
> + }
> + /* Try the next container group */
> + l = l->next;
> + } while (l != &init_container_group.list);
> +
> + /* No existing container group matched */
> + return NULL;
> }
>
> -static struct vfsmount *container_mount;
> -static struct super_block *container_sb;
> +/*
> + * find_container_group() takes an existing container group and a
> + * container object, and returns a container_group object that's
> + * equivalent to the old group, but with the given container
> + * substituted into the appropriate hierarchy. Must be called with
> + * manage_mutex held
> + */
> +
> +static struct container_group *find_container_group(
> + struct container_group *oldcg, struct container *cont)
> +{
> + struct container_group *res;
> + struct container_subsys *ss;
> + int h = cont->hierarchy;
> + int i;
> +
> + BUG_ON(oldcg->container[h] == cont);
> + /* First see if we already have a container group that matches
> + * the desired set */
> + spin_lock(&container_group_lock);
> + res = find_existing_container_group(oldcg, cont);
> + if (res)
> + get_container_group(res);
> + spin_unlock(&container_group_lock);
> +
> + if (res)
> + return res;
> +
> + res = kmalloc(sizeof(*res), GFP_KERNEL);
> + if (!res)
> + return NULL;
> +
> + /* Copy the old container group into the new one but overwrite
> + * the appropriate hierarchy with the new container object and
> + * subsystem states and reset the reference count. */
> + *res = *oldcg;
> + kref_init(&res->ref);
> + res->container[h] = cont;
> + for_each_subsys(h, ss) {
> + res->subsys[ss->subsys_id] = cont->subsys[ss->subsys_id];
> + }
> + /* Take reference counts on all the referenced containers,
> + * including the new one */
> + for (i = 0; i < CONFIG_MAX_CONTAINER_HIERARCHIES; i++) {
> + BUG_ON(!res->container[i]);
> + atomic_inc(&res->container[i]->count);
> + }
> +
> + /* Link this container group into the list */
> + spin_lock(&container_group_lock);
> + list_add(&res->list, &init_container_group.list);
> + container_group_count++;
> + spin_unlock(&container_group_lock);
> +
> + return res;
> +}
>
> /*
> * We have two global container mutexes below. They can nest.
> @@ -156,44 +307,109 @@ static struct super_block *container_sb;
> * small pieces of code, such as when reading out possibly multi-word
> * cpumasks and nodemasks.
> *
> - * The fork and exit callbacks container_fork() and container_exit(), don't
> - * (usually) take either mutex. These are the two most performance
> - * critical pieces of code here. The exception occurs on container_exit(),
> - * when a task in a notify_on_release container exits. Then manage_mutex
> - * is taken, and if the container count is zero, a usermode call made
> - * to /sbin/container_release_agent with the name of the container (path
> - * relative to the root of container file system) as the argument.
> - *
> - * A container can only be deleted if both its 'count' of using tasks
> - * is zero, and its list of 'children' containers is empty. Since all
> - * tasks in the system use _some_ container, and since there is always at
> - * least one task in the system (init, pid == 1), therefore, top_container
> - * always has either children containers and/or using tasks. So we don't
> + * The fork and exit callbacks container_fork() and container_exit(),
> + * don't take either mutex, unless some subsystem has registered a
> + * fork/exit callback.
> + *
> + * A container can only be deleted if all three conditions below hold:
> + *
> + * - its 'count' of using container groups is zero
> + * - its list of 'children' containers is empty.
> + * - all of its subsystems' state records have a zero 'refcnt'
> + *
> + * Since all tasks in the system use _some_ container group, and since
> + * there is always at least one task in the system (init, pid == 1),
> + * therefore, the top_container in each hierarchy always has either
> + * children containers and/or using container groups. So we don't
> * need a special hack to ensure that top_container cannot be deleted.
> *
> * The above "Tale of Two Semaphores" would be complete, but for:
> *
> * The task_lock() exception
> *
> - * The need for this exception arises from the action of attach_task(),
> - * which overwrites one tasks container pointer with another. It does
> - * so using both mutexes, however there are several performance
> - * critical places that need to reference task->container without the
> - * expense of grabbing a system global mutex. Therefore except as
> - * noted below, when dereferencing or, as in attach_task(), modifying
> - * a tasks container pointer we use task_lock(), which acts on a spinlock
> + * The need for this exception arises from the action of
> + * attach_task(), which overwrites a task's container group pointer
> + * with a pointer to a different group. It does so using both
> + * mutexes, however there are several performance critical places that
> + * need to reference task->containers without the expense of grabbing
> + * a system global mutex. Therefore except as noted below, when
> + * dereferencing or, as in attach_task(), modifying a task's
> + * containers pointer we use task_lock(), which acts on a spinlock
> * (task->alloc_lock) already in the task_struct routinely used for
> * such matters.
> *
> * P.S. One more locking exception. RCU is used to guard the
> - * update of a tasks container pointer by attach_task() and the
> + * update of a task's containers pointer by attach_task() and the
> * access of task->container->mems_generation via that pointer in
> * the routine container_update_task_memory_state().
> + *
> + * Some container subsystems and other external code also use these
> + * mutexes, exposed through the container_lock()/container_unlock()
> + * and container_manage_lock()/container_manage_unlock() functions.
> + *
> + * E.g. the out of memory (OOM) code needs to prevent containers from
> + * being changed while it scans the tasklist looking for a task in an
> + * overlapping container. The tasklist_lock is a spinlock, so must be
> + * taken inside callback_mutex.
> + *
> + * Some container subsystems (including cpusets) also use
> + * callback_mutex as a primary lock for synchronizing access to
> + * subsystem state. Deciding on best practices of when to use
> + * fine-grained locks vs container_lock()/container_unlock() is still
> + * a TODO.
> + *
> + * Note that manage_mutex and callback_mutex should both nest inside
> + * any inode->i_mutex, unless the inode isn't accessible to any code
> + * outside the current thread.
> */
>
> static DEFINE_MUTEX(manage_mutex);
> static DEFINE_MUTEX(callback_mutex);
>
> +/**
> + * container_lock - lock out any changes to container structures
> + *
> + */
> +
> +void container_lock(void)
> +{
> + mutex_lock(&callback_mutex);
> +}
> +
> +/**
> + * container_unlock - release lock on container changes
> + *
> + * Undo the lock taken in a previous container_lock() call.
> + */
> +
> +void container_unlock(void)
> +{
> + mutex_unlock(&callback_mutex);
> +}
> +
> +/**
> + * container_manage_lock() - lock out anyone else considering making
> + * changes to container structures. This is a more heavy-weight lock
> + * than the callback_mutex taken by container_lock() */
> +
> +void container_manage_lock(void)
> +{
> + mutex_lock(&manage_mutex);
> +}
> +
> +/**
> + * container_manage_unlock
> + *
> + * Undo the lock taken in a previous container_manage_lock() call.
> + */
> +
> +void container_manage_unlock(void)
> +{
> + mutex_unlock(&manage_mutex);
> +}
> +
> +
> +
> /*
> * A couple of forward declarations required, due to cyclic reference loop:
> * container_mkdir -> container_create -> container_populate_dir -> container_add_file
> @@ -202,15 +418,18 @@ static DEFINE_MUTEX(callback_mutex);
>
> static int container_mkdir(struct inode *dir, struct dentry *dentry, int mode);
> static int container_rmdir(struct inode *unused_dir, struct dentry *dentry);
> +static int container_populate_dir(struct container *cont);
> +static struct inode_operations container_dir_inode_operations;
> +struct file_operations proc_containerstats_operations;
>
> static struct backing_dev_info container_backing_dev_info = {
> .ra_pages = 0, /* No readahead */
> .capabilities = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
> };
>
> -static struct inode *container_new_inode(mode_t mode)
> +static struct inode *container_new_inode(mode_t mode, struct super_block *sb)
> {
> - struct inode *inode = new_inode(container_sb);
> + struct inode *inode = new_inode(sb);
>
> if (inode) {
> inode->i_mode = mode;
> @@ -238,7 +457,8 @@ static struct dentry_operations containe
> .d_iput = container_diput,
> };
>
> -static struct dentry *container_get_dentry(struct dentry *parent, const char *name)
> +static struct dentry *container_get_dentry(struct dentry *parent,
> + const char *name)
> {
> struct dentry *d = lookup_one_len(name, parent, strlen(name));
> if (!IS_ERR(d))
> @@ -255,19 +475,19 @@ static void remove_dir(struct dentry *d)
> dput(parent);
> }
>
> -/*
> - * NOTE : the dentry must have been dget()'ed
> - */
> -static void container_d_remove_dir(struct dentry *dentry)
> +static void container_clear_directory(struct dentry *dentry)
> {
> struct list_head *node;
> -
> + BUG_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
> spin_lock(&dcache_lock);
> node = dentry->d_subdirs.next;
> while (node != &dentry->d_subdirs) {
> struct dentry *d = list_entry(node, struct dentry, d_u.d_child);
> list_del_init(node);
> if (d->d_inode) {
> + /* This should never be called on a container
> + * directory with child containers */
> + BUG_ON(d->d_inode->i_mode & S_IFDIR);
> d = dget_locked(d);
> spin_unlock(&dcache_lock);
> d_delete(d);
> @@ -277,37 +497,222 @@ static void container_d_remove_dir(struc
> }
> node = dentry->d_subdirs.next;
> }
> + spin_unlock(&dcache_lock);
> +}
> +
> +/*
> + * NOTE : the dentry must have been dget()'ed
> + */
> +static void container_d_remove_dir(struct dentry *dentry)
> +{
> + container_clear_directory(dentry);
> +
> + spin_lock(&dcache_lock);
> list_del_init(&dentry->d_u.d_child);
> spin_unlock(&dcache_lock);
> remove_dir(dentry);
> }
>
> +static int rebind_subsystems(struct containerfs_root *root,
> + unsigned long final_bits)
> +{
> + unsigned long added_bits, removed_bits;
> + struct container *cont = &root->top_container;
> + int i;
> + int hierarchy = cont->hierarchy;
> +
> + removed_bits = root->subsys_bits & ~final_bits;
> + added_bits = final_bits & ~root->subsys_bits;
> + /* Check that any added subsystems are currently free */
> + for (i = 0; i < subsys_count; i++) {
> + unsigned long long bit = 1ull << i;
> + struct container_subsys *ss = subsys[i];
> + if (!(bit & added_bits))
> + continue;
> + if (ss->hierarchy != 0) {
> + /* Subsystem isn't free */
> + return -EBUSY;
> + }
> + }
> +
> + /* Currently we don't handle adding/removing subsystems when
> + * any subcontainers exist. This is theoretically supportable
> + * but involves complex erro r handling, so it's being left until
> + * later */
> + if (!list_empty(&cont->children)) {
> + return -EBUSY;
> + }
> +
> + mutex_lock(&callback_mutex);
> + /* Process each subsystem */
> + for (i = 0; i < subsys_count; i++) {
> + struct container_subsys *ss = subsys[i];
> + unsigned long bit = 1UL << i;
> + if (bit & added_bits) {
> + /* We're binding this subsystem to this hierarchy */
> + BUG_ON(cont->subsys[i]);
> + BUG_ON(dummytop->subsys[i]->container != dummytop);
> + cont->subsys[i] = dummytop->subsys[i];
> + cont->subsys[i]->container = cont;
> + list_add(&ss->sibling, &root->subsys_list);
> + rcu_assign_pointer(ss->hierarchy, hierarchy);
> + if (ss->bind)
> + ss->bind(ss, cont);
> +
> + } else if (bit & removed_bits) {
> + /* We're removing this subsystem */
> + BUG_ON(cont->subsys[i] != dummytop->subsys[i]);
> + BUG_ON(cont->subsys[i]->container != cont);
> + if (ss->bind)
> + ss->bind(ss, dummytop);
> + dummytop->subsys[i]->container = dummytop;
> + cont->subsys[i] = NULL;
> + rcu_assign_pointer(subsys[i]->hierarchy, 0);
> + list_del(&ss->sibling);
> + } else if (bit & final_bits) {
> + /* Subsystem state should already exist */
> + BUG_ON(!cont->subsys[i]);
> + } else {
> + /* Subsystem state shouldn't exist */
> + BUG_ON(cont->subsys[i]);
> + }
> + }
> + root->subsys_bits = final_bits;
> + mutex_unlock(&callback_mutex);
> + synchronize_rcu();
> +
> + return 0;
> +}
> +
> +/*
> + * Release the last use of a hierarchy. Will never be called when
> + * there are active subcontainers since each subcontainer bumps the
> + * value of sb->s_active.
> + */
> +
> +static void container_put_super(struct super_block *sb) {
> +
> + struct containerfs_root *root = sb->s_fs_info;
> + struct container *cont = &root->top_container;
> + int ret;
> +
> + root->sb = NULL;
> + sb->s_fs_info = NULL;
> +
> + mutex_lock(&manage_mutex);
> +
> + BUG_ON(root->number_of_containers != 1);
> + BUG_ON(!list_empty(&cont->children));
> + BUG_ON(!list_empty(&cont->sibling));
> + BUG_ON(!root->subsys_bits);
> +
> + /* Rebind all subsystems back to the default hierarchy */
> + ret = rebind_subsystems(root, 0);
> + BUG_ON(ret);
> +
> + mutex_unlock(&manage_mutex);
> +}
> +
> +static int container_show_options(struct seq_file *seq, struct vfsmount *vfs)
> +{
> + struct containerfs_root *root = vfs->mnt_sb->s_fs_info;
> + struct container_subsys *ss;
> + for_each_subsys(root->top_container.hierarchy, ss) {
> + seq_printf(seq, ",%s", ss->name);
> + }
> + return 0;
> +}
> +
> +/* Convert a hierarchy specifier into a bitmask. LL=manage_mutex */
> +static int parse_containerfs_options(char *opts, unsigned long *bits)
> +{
> + char *token, *o = opts ?: "all";
> +
> + *bits = 0;
> +
> + while ((token = strsep(&o, ",")) != NULL) {
> + if (!*token)
> + return -EINVAL;
> + if (!strcmp(token, "all")) {
> + *bits = (1 << subsys_count) - 1;
> + } else {
> + struct container_subsys *ss;
> + int i;
> + for (i = 0; i < subsys_count; i++) {
> + ss = subsys[i];
> + if (!strcmp(token, ss->name)) {
> + *bits |= 1 << i;
> + break;
> + }
> + }
> + if (i == subsys_count)
> + return -ENOENT;
> + }
> + }
> +
> + /* We can't have an empty hierarchy */
> + if (!*bits)
> + return -EINVAL;
> +
> + return 0;
> +}
> +
> +static int container_remount(struct super_block *sb, int *flags, char *data)
> +{
> + int ret = 0;
> + unsigned long subsys_bits;
> + struct containerfs_root *root = sb->s_fs_info;
> + struct container *cont = &root->top_container;
> +
> + mutex_lock(&cont->dentry->d_inode->i_mutex);
> + mutex_lock(&manage_mutex);
> +
> + /* See what subsystems are wanted */
> + ret = parse_containerfs_options(data, &subsys_bits);
> + if (ret)
> + goto out_unlock;
> +
> + ret = rebind_subsystems(root, subsys_bits);
> +
> + /* (re)populate subsystem files */
> + if (!ret)
> + container_populate_dir(cont);
> +
> + out_unlock:
> + mutex_unlock(&manage_mutex);
> + mutex_unlock(&cont->dentry->d_inode->i_mutex);
> + return ret;
> +}
> +
> static struct super_operations container_ops = {
> .statfs = simple_statfs,
> .drop_inode = generic_delete_inode,
> + .put_super = container_put_super,
> + .show_options = container_show_options,
> + .remount_fs = container_remount,
> };
>
> -static int container_fill_super(struct super_block *sb, void *unused_data,
> - int unused_silent)
> +static int container_fill_super(struct super_block *sb, void *options,
> + int unused_silent)
> {
> struct inode *inode;
> struct dentry *root;
> + struct containerfs_root *hroot = options;
>
> sb->s_blocksize = PAGE_CACHE_SIZE;
> sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
> sb->s_magic = CONTAINER_SUPER_MAGIC;
> sb->s_op = &container_ops;
> - container_sb = sb;
>
> - inode = container_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR);
> - if (inode) {
> - inode->i_op = &simple_dir_inode_operations;
> - inode->i_fop = &simple_dir_operations;
> - /* directories start off with i_nlink == 2 (for "." entry) */
> - inode->i_nlink++;
> - } else {
> + inode = container_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR, sb);
> + if (!inode)
> return -ENOMEM;
> - }
> +
> + inode->i_op = &simple_dir_inode_operations;
> + inode->i_fop = &simple_dir_operations;
> + inode->i_op = &container_dir_inode_operations;
> + /* directories start off with i_nlink == 2 (for "." entry) */
> + inc_nlink(inode);
>
> root = d_alloc_root(inode);
> if (!root) {
> @@ -315,6 +720,12 @@ static int container_fill_super(struct s
> return -ENOMEM;
> }
> sb->s_root = root;
> + root->d_fsdata = &hroot->top_container;
> + hroot->top_container.dentry = root;
> +
> + sb->s_fs_info = hroot;
> + hroot->sb = sb;
> +
> return 0;
> }
>
> @@ -322,7 +733,82 @@ static int container_get_sb(struct file_
> int flags, const char *unused_dev_name,
> void *data, struct vfsmount *mnt)
> {
> - return get_sb_single(fs_type, flags, data, container_fill_super, mnt);
> + int i;
> + unsigned long subsys_bits = 0;
> + int ret = 0;
> + struct containerfs_root *root = NULL;
> + int hierarchy;
> +
> + mutex_lock(&manage_mutex);
> +
> + /* First find the desired set of resource controllers */
> + ret = parse_containerfs_options(data, &subsys_bits);
> + if (ret)
> + goto out_unlock;
> +
> + /* See if we already have a hierarchy containing this set */
> +
> + for (i = 1; i < CONFIG_MAX_CONTAINER_HIERARCHIES; i++) {
> + root = &rootnode[i];
> + /* We match - use this hieracrchy */
> + if (root->subsys_bits == subsys_bits) break;
> + /* We clash - fail */
> + if (root->subsys_bits & subsys_bits) {
> + ret = -EBUSY;
> + goto out_unlock;
> + }
> + }
> +
> + if (i == CONFIG_MAX_CONTAINER_HIERARCHIES) {
> + /* No existing hierarchy matched this set - but we
> + * know that all the subsystems are free */
> + for (i = 1; i < CONFIG_MAX_CONTAINER_HIERARCHIES; i++) {
> + root = &rootnode[i];
> + if (!root->sb && !root->subsys_bits) break;
> + }
> + }
> +
> + if (i == CONFIG_MAX_CONTAINER_HIERARCHIES) {
> + ret = -ENOSPC;
> + goto out_unlock;
> + }
> +
> + hierarchy = i;
> +
> + if (!root->sb) {
> + /* We need a new superblock for this container combination */
> + struct container *cont = &root->top_container;
> +
> + BUG_ON(root->subsys_bits);
> + ret = get_sb_nodev(fs_type, flags, root,
> + container_fill_super, mnt);
> + if (ret)
> + goto out_unlock;
> +
> + BUG_ON(!list_empty(&cont->sibling));
> + BUG_ON(!list_empty(&cont->children));
> + BUG_ON(root->number_of_containers != 1);
> +
> + ret = rebind_subsystems(root, subsys_bits);
> +
> + /* It's safe to nest i_mutex inside manage_mutex in
> + * this case, since no-one else can be accessing this
> + * directory yet */
> + mutex_lock(&cont->dentry->d_inode->i_mutex);
> + container_populate_dir(cont);
> + mutex_unlock(&cont->dentry->d_inode->i_mutex);
> + BUG_ON(ret);
> +
> + } else {
> + /* Reuse the existing superblock */
> + ret = simple_set_mnt(mnt, root->sb);
> + if (!ret)
> + atomic_inc(&root->sb->s_active);
> + }
> +
> + out_unlock:
> + mutex_unlock(&manage_mutex);
> + return ret;
> }
>
> static struct file_system_type container_fs_type = {
> @@ -372,135 +858,79 @@ int container_path(const struct containe
> }
>
> /*
> - * Notify userspace when a container is released, by running
> - * /sbin/container_release_agent with the name of the container (path
> - * relative to the root of container file system) as the argument.
> - *
> - * Most likely, this user command will try to rmdir this container.
> - *
> - * This races with the possibility that some other task will be
> - * attached to this container before it is removed, or that some other
> - * user task will 'mkdir' a child container of this container. That's ok.
> - * The presumed 'rmdir' will fail quietly if this container is no longer
> - * unused, and this container will be reprieved from its death sentence,
> - * to continue to serve a useful existence. Next time it's released,
> - * we will get notified again, if it still has 'notify_on_release' set.
> - *
> - * The final arg to call_usermodehelper() is 0, which means don't
> - * wait. The separate /sbin/container_release_agent task is forked by
> - * call_usermodehelper(), then control in this thread returns here,
> - * without waiting for the release agent task. We don't bother to
> - * wait because the caller of this routine has no use for the exit
> - * status of the /sbin/container_release_agent task, so no sense holding
> - * our caller up for that.
> - *
> - * When we had only one container mutex, we had to call this
> - * without holding it, to avoid deadlock when call_usermodehelper()
> - * allocated memory. With two locks, we could now call this while
> - * holding manage_mutex, but we still don't, so as to minimize
> - * the time manage_mutex is held.
> + * Attach task 'tsk' to container 'cont'
> + *
> + * Call holding manage_mutex. May take callback_mutex and task_lock of
> + * the task 'pid' during call.
> */
>
> -static void container_release_agent(const char *pathbuf)
> +static int attach_task(struct container *cont, struct task_struct *tsk)
> {
> - char *argv[3], *envp[3];
> - int i;
> -
> - if (!pathbuf)
> - return;
> -
> - i = 0;
> - argv[i++] = release_agent_path;
> - argv[i++] = (char *)pathbuf;
> - argv[i] = NULL;
> -
> - i = 0;
> - /* minimal command environment */
> - envp[i++] = "HOME=/";
> - envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
> - envp[i] = NULL;
> + int retval = 0;
> + struct container_subsys *ss;
> + struct container_group *oldcg, *newcg;
> + struct container *oldcont;
> + int h = cont->hierarchy;
>
> - call_usermodehelper(argv[0], argv, envp, 0);
> - kfree(pathbuf);
> -}
> + /* Nothing to do if the task is already in that container */
> + if (tsk->containers->container[h] == cont)
> + return 0;
>
> -/*
> - * Either cont->count of using tasks transitioned to zero, or the
> - * cont->children list of child containers just became empty. If this
> - * cont is notify_on_release() and now both the user count is zero and
> - * the list of children is empty, prepare container path in a kmalloc'd
> - * buffer, to be returned via ppathbuf, so that the caller can invoke
> - * container_release_agent() with it later on, once manage_mutex is dropped.
> - * Call here with manage_mutex held.
> - *
> - * This check_for_release() routine is responsible for kmalloc'ing
> - * pathbuf. The above container_release_agent() is responsible for
> - * kfree'ing pathbuf. The caller of these routines is responsible
> - * for providing a pathbuf pointer, initialized to NULL, then
> - * calling check_for_release() with manage_mutex held and the address
> - * of the pathbuf pointer, then dropping manage_mutex, then calling
> - * container_release_agent() with pathbuf, as set by check_for_release().
> - */
> -
> -static void check_for_release(struct container *cont, char **ppathbuf)
> -{
> - if (notify_on_release(cont) && atomic_read(&cont->count) == 0 &&
> - list_empty(&cont->children)) {
> - char *buf;
> -
> - buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
> - if (!buf)
> - return;
> -
> - if (container_path(cont, buf, PAGE_SIZE) < 0)
> - kfree(buf);
> - else
> - *ppathbuf = buf;
> + for_each_subsys(h, ss) {
> + if (ss->can_attach) {
> + retval = ss->can_attach(ss, cont, tsk);
> + if (retval) {
> + put_task_struct(tsk);
> + return retval;
> + }
> + }
> }
> -}
>
> + /* Locate or allocate a new container_group for this task,
> + * based on its final set of containers */
> + oldcg = tsk->containers;
> + newcg = find_container_group(oldcg, cont);
> + if (!newcg) {
> + put_task_struct(tsk);
> + return -ENOMEM;
> + }
>
> -/*
> - * update_flag - read a 0 or a 1 in a file and update associated flag
> - * bit: the bit to update (CONT_NOTIFY_ON_RELEASE)
> - * cont: the container to update
> - * buf: the buffer where we read the 0 or 1
> - *
> - * Call with manage_mutex held.
> - */
> -
> -static int update_flag(container_flagbits_t bit, struct container *cont, char *buf)
> -{
> - int turning_on;
> + mutex_lock(&callback_mutex);
> + task_lock(tsk);
> + rcu_assign_pointer(tsk->containers, newcg);
> + task_unlock(tsk);
>
> - turning_on = (simple_strtoul(buf, NULL, 10) != 0);
> + oldcont = oldcg->container[h];
> + for_each_subsys(h, ss) {
> + if (ss->attach) {
> + ss->attach(ss, cont, oldcont, tsk);
> + }
> + }
>
> - mutex_lock(&callback_mutex);
> - if (turning_on)
> - set_bit(bit, &cont->flags);
> - else
> - clear_bit(bit, &cont->flags);
> mutex_unlock(&callback_mutex);
>
> + for_each_subsys(h, ss) {
> + if (ss->post_attach) {
> + ss->post_attach(ss, cont, oldcont, tsk);
> + }
> + }
> +
> + synchronize_rcu();
> + put_container_group(oldcg);
> return 0;
> }
>
> -
> /*
> - * Attack task specified by pid in 'pidbuf' to container 'cont', possibly
> - * writing the path of the old container in 'ppathbuf' if it needs to be
> - * notified on release.
> + * Attach task with pid 'pid' to container 'cont'. Call with
> + * manage_mutex, may take callback_mutex and task_lock of task
> *
> - * Call holding manage_mutex. May take callback_mutex and task_lock of
> - * the task 'pid' during call.
> */
>
> -static int attach_task(struct container *cont, char *pidbuf, char **ppathbuf)
> +static int attach_task_by_pid(struct container *cont, char *pidbuf)
> {
> pid_t pid;
> struct task_struct *tsk;
> - struct container *oldcont;
> - int retval = 0;
> + int ret;
>
> if (sscanf(pidbuf, "%d", &pid) != 1)
> return -EIO;
> @@ -527,43 +957,9 @@ static int attach_task(struct container
> get_task_struct(tsk);
> }
>
> -#ifdef CONFIG_CPUSETS
> - retval = cpuset_can_attach_task(cont, tsk);
> -#endif
> - if (retval) {
> - put_task_struct(tsk);
> - return retval;
> - }
> -
> - mutex_lock(&callback_mutex);
> -
> - task_lock(tsk);
> - oldcont = tsk->container;
> - if (!oldcont) {
> - task_unlock(tsk);
> - mutex_unlock(&callback_mutex);
> - put_task_struct(tsk);
> - return -ESRCH;
> - }
> - atomic_inc(&cont->count);
> - rcu_assign_pointer(tsk->container, cont);
> - task_unlock(tsk);
> -
> -#ifdef CONFIG_CPUSETS
> - cpuset_attach_task(cont, tsk);
> -#endif
> -
> - mutex_unlock(&callback_mutex);
> -
> -#ifdef CONFIG_CPUSETS
> - cpuset_post_attach_task(cont, oldcont, tsk);
> -#endif
> -
> + ret = attach_task(cont, tsk);
> put_task_struct(tsk);
> - synchronize_rcu();
> - if (atomic_dec_and_test(&oldcont->count))
> - check_for_release(oldcont, ppathbuf);
> - return 0;
> + return ret;
> }
>
> /* The various types of files and directories in a container file system */
> @@ -571,9 +967,7 @@ static int attach_task(struct container
> typedef enum {
> FILE_ROOT,
> FILE_DIR,
> - FILE_NOTIFY_ON_RELEASE,
> FILE_TASKLIST,
> - FILE_RELEASE_AGENT,
> } container_filetype_t;
>
> static ssize_t container_common_file_write(struct container *cont,
> @@ -584,7 +978,6 @@ static ssize_t container_common_file_wri
> {
> container_filetype_t type = cft->private;
> char *buffer;
> - char *pathbuf = NULL;
> int retval = 0;
>
> if (nbytes >= PATH_MAX)
> @@ -608,26 +1001,9 @@ static ssize_t container_common_file_wri
> }
>
> switch (type) {
> - case FILE_NOTIFY_ON_RELEASE:
> - retval = update_flag(CONT_NOTIFY_ON_RELEASE, cont, buffer);
> - break;
> case FILE_TASKLIST:
> - retval = attach_task(cont, buffer, &pathbuf);
> - break;
> - case FILE_RELEASE_AGENT:
> - {
> - if (nbytes < sizeof(release_agent_path)) {
> - /* We never write anything other than '\0'
> - * into the last char of release_agent_path,
> - * so it always remains a NUL-terminated
> - * string */
> - strncpy(release_agent_path, buffer, nbytes);
> - release_agent_path[nbytes] = 0;
> - } else {
> - retval = -ENOSPC;
> - }
> + retval = attach_task_by_pid(cont, buffer);
> break;
> - }
> default:
> retval = -EINVAL;
> goto out2;
> @@ -637,7 +1013,6 @@ static ssize_t container_common_file_wri
> retval = nbytes;
> out2:
> mutex_unlock(&manage_mutex);
> - container_release_agent(pathbuf);
> out1:
> kfree(buffer);
> return retval;
> @@ -646,80 +1021,27 @@ out1:
> static ssize_t container_file_write(struct file *file, const char __user *buf,
> size_t nbytes, loff_t *ppos)
> {
> - ssize_t retval = 0;
> struct cftype *cft = __d_cft(file->f_dentry);
> struct container *cont = __d_cont(file->f_dentry->d_parent);
> if (!cft)
> return -ENODEV;
> + if (!cft->write)
> + return -EINVAL;
>
> - /* special function ? */
> - if (cft->write)
> - retval = cft->write(cont, cft, file, buf, nbytes, ppos);
> - else
> - retval = -EINVAL;
> -
> - return retval;
> + return cft->write(cont, cft, file, buf, nbytes, ppos);
> }
>
> -static ssize_t container_common_file_read(struct container *cont,
> - struct cftype *cft,
> - struct file *file,
> - char __user *buf,
> - size_t nbytes, loff_t *ppos)
> +static ssize_t container_file_read(struct file *file, char __user *buf,
> + size_t nbytes, loff_t *ppos)
> {
> - container_filetype_t type = cft->private;
> - char *page;
> - ssize_t retval = 0;
> - char *s;
> -
> - if (!(page = (char *)__get_free_page(GFP_KERNEL)))
> - return -ENOMEM;
> -
> - s = page;
> -
> - switch (type) {
> - case FILE_NOTIFY_ON_RELEASE:
> - *s++ = notify_on_release(cont) ? '1' : '0';
> - break;
> - case FILE_RELEASE_AGENT:
> - {
> - size_t n;
> - container_manage_lock();
> - n = strnlen(release_agent_path, sizeof(release_agent_path));
> - n = min(n, (size_t) PAGE_SIZE);
> - strncpy(s, release_agent_path, n);
> - container_manage_unlock();
> - s += n;
> - break;
> - }
> - default:
> - retval = -EINVAL;
> - goto out;
> - }
> - *s++ = '\n';
> -
> - retval = simple_read_from_buffer(buf, nbytes, ppos, page, s - page);
> -out:
> - free_page((unsigned long)page);
> - return retval;
> -}
> -
> -static ssize_t container_file_read(struct file *file, char __user *buf, size_t nbytes,
> - loff_t *ppos)
> -{
> - ssize_t retval = 0;
> struct cftype *cft = __d_cft(file->f_dentry);
> struct container *cont = __d_cont(file->f_dentry->d_parent);
> if (!cft)
> return -ENODEV;
> + if (!cft->read)
> + return -EINVAL;
>
> - /* special function ? */
> - if (cft->read)
> - retval = cft->read(cont, cft, file, buf, nbytes, ppos);
> - else
> - retval = -EINVAL;
> -
> - return retval;
> + return cft->read(cont, cft, file, buf, nbytes, ppos);
> }
>
> static int container_file_open(struct inode *inode, struct file *file)
> @@ -780,7 +1102,7 @@ static struct inode_operations container
> .rename = container_rename,
> };
>
> -static int container_create_file(struct dentry *dentry, int mode)
> +static int container_create_file(struct dentry *dentry, int mode, struct super_block *sb)
> {
> struct inode *inode;
>
> @@ -789,7 +1111,7 @@ static int container_create_file(struct
> if (dentry->d_inode)
> return -EEXIST;
>
> - inode = container_new_inode(mode);
> + inode = container_new_inode(mode, sb);
> if (!inode)
> return -ENOMEM;
>
> @@ -798,7 +1120,11 @@ static int container_create_file(struct
> inode->i_fop = &simple_dir_operations;
>
> /* start off with i_nlink == 2 (for "." entry) */
> - inode->i_nlink++;
> + inc_nlink(inode);
> +
> + /* start with the directory inode held, so that we can
> + * populate it without racing with another mkdir */
> + mutex_lock(&inode->i_mutex);
> } else if (S_ISREG(mode)) {
> inode->i_size = 0;
> inode->i_fop = &container_file_operations;
> @@ -818,20 +1144,19 @@ static int container_create_file(struct
> * mode: mode to set on new directory.
> */
>
> -static int container_create_dir(struct container *cont, const char *name, int mode)
> +static int container_create_dir(struct container *cont, struct dentry *dentry,
> + int mode)
> {
> - struct dentry *dentry = NULL;
> struct dentry *parent;
> int error = 0;
>
> parent = cont->parent->dentry;
> - dentry = container_get_dentry(parent, name);
> if (IS_ERR(dentry))
> return PTR_ERR(dentry);
> - error = container_create_file(dentry, S_IFDIR | mode);
> + error = container_create_file(dentry, S_IFDIR | mode, cont->root->sb);
> if (!error) {
> dentry->d_fsdata = cont;
> - parent->d_inode->i_nlink++;
> + inc_nlink(parent->d_inode);
> cont->dentry = dentry;
> }
> dput(dentry);
> @@ -845,19 +1170,40 @@ int container_add_file(struct container
> struct dentry *dentry;
> int error;
>
> - mutex_lock(&dir->d_inode->i_mutex);
> + BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
> dentry = container_get_dentry(dir, cft->name);
> if (!IS_ERR(dentry)) {
> - error = container_create_file(dentry, 0644 | S_IFREG);
> + error = container_create_file(dentry, 0644 | S_IFREG, cont->root->sb);
> if (!error)
> dentry->d_fsdata = (void *)cft;
> dput(dentry);
> } else
> error = PTR_ERR(dentry);
> - mutex_unlock(&dir->d_inode->i_mutex);
> return error;
> }
>
> +/* Count the number of tasks in a container. Could be made more
> + * time-efficient but less space-efficient with more linked lists
> + * running through each container and the container_group structures
> + * that referenced it. */
> +
> +int container_task_count(const struct container *cont) {
> + int count = 0;
> + int hierarchy = cont->hierarchy;
> + struct list_head *l;
> + spin_lock(&container_group_lock);
> + l = &init_container_group.list;
> + do {
> + struct container_group *cg =
> + list_entry(l, struct container_group, list);
> + if (cg->container[hierarchy] == cont)
> + count += atomic_read(&cg->ref.refcount);
> + l = l->next;
> + } while (l != &init_container_group.list);
> + spin_unlock(&container_group_lock);
> + return count;
> +}
> +
> /*
> * Stuff for reading the 'tasks' file.
> *
> @@ -881,20 +1227,23 @@ struct ctr_struct {
> };
>
> /*
> - * Load into 'pidarray' up to 'npids' of the tasks using container 'cont'.
> - * Return actual number of pids loaded. No need to task_lock(p)
> - * when reading out p->container, as we don't really care if it changes
> - * on the next cycle, and we are not going to try to dereference it.
> + * Load into 'pidarray' up to 'npids' of the tasks using container
> + * 'cont'. Return actual number of pids loaded. No need to
> + * task_lock(p) when reading out p->container, since we're in an RCU
> + * read section, so the container_group can't go away, and is
> + * immutable after creation.
> */
> static int pid_array_load(pid_t *pidarray, int npids, struct container *cont)
> {
> int n = 0;
> struct task_struct *g, *p;
> + int h = cont->hierarchy;
>
> + rcu_read_lock();
> read_lock(&tasklist_lock);
>
> do_each_thread(g, p) {
> - if (p->container == cont) {
> + if (p->containers->container[h] == cont) {
> pidarray[n++] = pid_nr(task_pid(p));
> if (unlikely(n == npids))
> goto array_full;
> @@ -903,6 +1252,7 @@ static int pid_array_load(pid_t *pidarra
>
> array_full:
> read_unlock(&tasklist_lock);
> + rcu_read_unlock();
> return n;
> }
>
> @@ -953,7 +1303,7 @@ static int container_tasks_open(struct i
> * caller from the case that the additional container users didn't
> * show up until sometime later on.
> */
> - npids = atomic_read(&cont->count);
> + npids = container_task_count(cont);
> pidarray = kmalloc(npids * sizeof(pid_t), GFP_KERNEL);
> if (!pidarray)
> goto err1;
> @@ -1020,38 +1370,34 @@ static struct cftype cft_tasks = {
> .private = FILE_TASKLIST,
> };
>
> -static struct cftype cft_notify_on_release = {
> - .name = "notify_on_release",
> - .read = container_common_file_read,
> - .write = container_common_file_write,
> - .private = FILE_NOTIFY_ON_RELEASE,
> -};
> -
> -static struct cftype cft_release_agent = {
> - .name = "release_agent",
> - .read = container_common_file_read,
> - .write = container_common_file_write,
> - .private = FILE_RELEASE_AGENT,
> -};
> -
> static int container_populate_dir(struct container *cont)
> {
> int err;
> + struct container_subsys *ss;
> +
> + /* First clear out any existing files */
> + container_clear_directory(cont->dentry);
>
> - if ((err = container_add_file(cont, &cft_notify_on_release)) < 0)
> - return err;
> if ((err = container_add_file(cont, &cft_tasks)) < 0)
> return err;
> - if ((cont == &top_container) &&
> - (err = container_add_file(cont, &cft_release_agent)) < 0)
> - return err;
> -#ifdef CONFIG_CPUSETS
> - if ((err = cpuset_populate_dir(cont)) < 0)
> - return err;
> -#endif
> +
> + for_each_subsys(cont->hierarchy, ss) {
> + if (ss->populate && (err = ss->populate(ss, cont)) < 0)
> + return err;
> + }
> +
> return 0;
> }
>
> +static void init_container_css(struct container_subsys *ss,
> + struct container *cont)
> +{
> + struct container_subsys_state *css = cont->subsys[ss->subsys_id];
> + css->container = cont;
> + spin_lock_init(&css->refcnt_lock);
> + atomic_set(&css->refcnt, 0);
> +}
> +
> /*
> * container_create - create a container
> * parent: container that will be parent of the new container.
> @@ -1061,61 +1407,83 @@ static int container_populate_dir(struct
> * Must be called with the mutex on the parent inode held
> */
>
> -static long container_create(struct container *parent, const char *name, int mode)
> +static long container_create(struct container *parent, struct dentry *dentry,
> + int mode)
> {
> struct container *cont;
> - int err;
> + struct containerfs_root *root = parent->root;
> + int err = 0;
> + struct container_subsys *ss;
> + struct super_block *sb = root->sb;
>
> - cont = kmalloc(sizeof(*cont), GFP_KERNEL);
> + cont = kzalloc(sizeof(*cont), GFP_KERNEL);
> if (!cont)
> return -ENOMEM;
>
> + /* Grab a reference on the superblock so the hierarchy doesn't
> + * get deleted on unmount if there are child containers. This
> + * can be done outside manage_mutex, since the sb can't
> + * disappear while someone has an open control file on the
> + * fs */
> + atomic_inc(&sb->s_active);
> +
> mutex_lock(&manage_mutex);
> +
> cont->flags = 0;
> - if (notify_on_release(parent))
> - set_bit(CONT_NOTIFY_ON_RELEASE, &cont->flags);
> atomic_set(&cont->count, 0);
> INIT_LIST_HEAD(&cont->sibling);
> INIT_LIST_HEAD(&cont->children);
>
> cont->parent = parent;
> -
> -#ifdef CONFIG_CPUSETS
> - err = cpuset_create(cont);
> - if (err)
> - goto err_unlock_free;
> -#endif
> + cont->root = parent->root;
> + cont->hierarchy = parent->hierarchy;
> + cont->top_container = parent->top_container;
> +
> + for_each_subsys(cont->hierarchy, ss) {
> + err = ss->create(ss, cont);
> + if (err) goto err_destroy;
> + init_container_css(ss, cont);
> + }
>
> mutex_lock(&callback_mutex);
> list_add(&cont->sibling, &cont->parent->children);
> - number_of_containers++;
> + root->number_of_containers++;
> mutex_unlock(&callback_mutex);
>
> - err = container_create_dir(cont, name, mode);
> + err = container_create_dir(cont, dentry, mode);
> if (err < 0)
> goto err_remove;
>
> - /*
> - * Release manage_mutex before container_populate_dir() because it
> - * will down() this new directory's i_mutex and if we race with
> - * another mkdir, we might deadlock.
> - */
> - mutex_unlock(&manage_mutex);
> + /* The container directory was pre-locked for us */
> + BUG_ON(!mutex_is_locked(&cont->dentry->d_inode->i_mutex));
>
> err = container_populate_dir(cont);
> /* If err < 0, we have a half-filled directory - oh well ;) */
> +
> + mutex_unlock(&manage_mutex);
> + mutex_unlock(&cont->dentry->d_inode->i_mutex);
> +
> return 0;
>
> err_remove:
> -#ifdef CONFIG_CPUSETS
> - cpuset_destroy(cont);
> -#endif
> +
> mutex_lock(&callback_mutex);
> list_del(&cont->sibling);
> - number_of_containers--;
> + root->number_of_containers--;
> mutex_unlock(&callback_mutex);
> - err_unlock_free:
> +
> + err_destroy:
> +
> + for_each_subsys(cont->hierarchy, ss) {
> + if (cont->subsys[ss->subsys_id])
> + ss->destroy(ss, cont);
> + }
> +
> mutex_unlock(&manage_mutex);
> +
> + /* Release the reference count that we took on the superblock */
> + deactivate_super(sb);
> +
> kfree(cont);
> return err;
> }
> @@ -1125,26 +1493,20 @@ static int container_mkdir(struct inode
> struct container *c_parent = dentry->d_parent->d_fsdata;
>
> /* the vfs holds inode->i_mutex already */
> - return container_create(c_parent, dentry->d_name.name, mode | S_IFDIR);
> + return container_create(c_parent, dentry, mode | S_IFDIR);
> }
>
> -/*
> - * Locking note on the strange update_flag() call below:
> - *
> - * If the container being removed is marked cpu_exclusive, then simulate
> - * turning cpu_exclusive off, which will call update_cpu_domains().
> - * The lock_cpu_hotplug() call in update_cpu_domains() must not be
> - * made while holding callback_mutex. Elsewhere the kernel nests
> - * callback_mutex inside lock_cpu_hotplug() calls. So the reverse
> - * nesting would risk an ABBA deadlock.
> - */
> -
> static int container_rmdir(struct inode *unused_dir, struct dentry *dentry)
> {
> struct container *cont = dentry->d_fsdata;
> struct dentry *d;
> struct container *parent;
> - char *pathbuf = NULL;
> + struct container_subsys *ss;
> + struct super_block *sb;
> + struct containerfs_root *root;
> + unsigned long flags;
> + int css_busy = 0;
> + int hierarchy;
>
> /* the vfs holds both inode->i_mutex already */
>
> @@ -1157,82 +1519,331 @@ static int container_rmdir(struct inode
> mutex_unlock(&manage_mutex);
> return -EBUSY;
> }
> +
> + hierarchy = cont->hierarchy;
> parent = cont->parent;
> + root = cont->root;
> + sb = root->sb;
> +
> + local_irq_save(flags);
> + /* Check each container, locking the refcnt lock and testing
> + * the refcnt. This will lock out any calls to css_get() */
> + for_each_subsys(hierarchy, ss) {
> + struct container_subsys_state *css;
> + css = cont->subsys[ss->subsys_id];
> + spin_lock(&css->refcnt_lock);
> + css_busy += atomic_read(&css->refcnt);
> + }
> + /* Go through and release all the locks; if we weren't busy,
> + * then set the refcount to -1 to prevent css_get() from adding
> + * a refcount */
> + for_each_subsys(hierarchy, ss) {
> + struct container_subsys_state *css;
> + css = cont->subsys[ss->subsys_id];
> + if (!css_busy) atomic_dec(&css->refcnt);
> + spin_unlock(&css->refcnt_lock);
> + }
> + local_irq_restore(flags);
> + if (css_busy) {
> + mutex_unlock(&manage_mutex);
> + return -EBUSY;
> + }
> +
> + for_each_subsys(hierarchy, ss) {
> + if (cont->subsys[ss->subsys_id])
> + ss->destroy(ss, cont);
> + }
> +
> mutex_lock(&callback_mutex);
> set_bit(CONT_REMOVED, &cont->flags);
> - list_del(&cont->sibling); /* delete my sibling from parent->children */
> + /* delete my sibling from parent->children */
> + list_del(&cont->sibling);
> spin_lock(&cont->dentry->d_lock);
> d = dget(cont->dentry);
> cont->dentry = NULL;
> spin_unlock(&d->d_lock);
> +
> container_d_remove_dir(d);
> dput(d);
> - number_of_containers--;
> + root->number_of_containers--;
> mutex_unlock(&callback_mutex);
> -#ifdef CONFIG_CPUSETS
> - cpuset_destroy(cont);
> -#endif
> - if (list_empty(&parent->children))
> - check_for_release(parent, &pathbuf);
> +
> mutex_unlock(&manage_mutex);
> - container_release_agent(pathbuf);
> + /* Drop the active superblock reference that we took when we
> + * created the container */
> + deactivate_super(sb);
> return 0;
> }
>
> -/*
> - * container_init_early - probably not needed yet, but will be needed
> - * once cpusets are hooked into this code
> +static atomic_t namecnt;
> +static void get_unused_name(char *buf) {
> + sprintf(buf, "node%d", atomic_inc_return(&namecnt));
> +}
> +
> +/**
> + * container_clone - duplicate the current container and move this
> + * task into the new child
> */
> +int container_clone(struct task_struct *tsk, struct container_subsys *subsys)
> +{
> + struct dentry *dentry;
> + int ret = 0;
> + char nodename[32];
> + struct container *parent, *child;
> + struct inode *inode;
> + int h;
> +
> + /* We shouldn't be called by an unregistered subsystem */
> + BUG_ON(subsys->subsys_id < 0);
> +
> + /* First figure out what hierarchy and container we're dealing
> + * with, and pin them so we can drop manage_mutex */
> + mutex_lock(&manage_mutex);
> + again:
> + h = subsys->hierarchy;
> + if (h == 0) {
> + printk(KERN_INFO
> + "Not cloning container for unused subsystem %s\n",
> + subsys->name);
> + mutex_unlock(&manage_mutex);
> + return 0;
> + }
> + parent = tsk->containers->container[h];
> + /* Pin the hierarchy */
> + atomic_inc(&parent->root->sb->s_active);
> + /* Keep the container alive */
> + atomic_inc(&parent->count);
> + mutex_unlock(&manage_mutex);
> +
> + /* Now do the VFS work to create a container */
> + get_unused_name(nodename);
> + inode = parent->dentry->d_inode;
> +
> + /* Hold the parent directory mutex across this operation to
> + * stop anyone else deleting the new container */
> + mutex_lock(&inode->i_mutex);
> + dentry = container_get_dentry(parent->dentry, nodename);
> + if (IS_ERR(dentry)) {
> + printk(KERN_INFO
> + "Couldn't allocate dentry for %s: %ld\n", nodename,
> + PTR_ERR(dentry));
> + ret = PTR_ERR(dentry);
> + goto out_release;
> + }
> +
> + /* Create the container directory, which also creates the container */
> + ret = vfs_mkdir(inode, dentry, S_IFDIR | 0755);
> + child = __d_cont(dentry);
> + dput(dentry);
> + if (ret) {
> + printk(KERN_INFO
> + "Failed to create container %s: %d\n", nodename,
> + ret);
> + goto out_release;
> + }
> +
> + if (!child) {
> + printk(KERN_INFO
> + "Couldn't find new container %s\n", nodename);
> + ret = -ENOMEM;
> + goto out_release;
> + }
> +
> + /* The container now exists. Retake manage_mutex and check
> + * that we're still in the same state that we thought we
> + * were. */
> + mutex_lock(&manage_mutex);
> + if ((h != subsys->hierarchy) ||
> + (parent != tsk->containers->container[h])) {
> + /* Aargh, we raced ... */
> + mutex_unlock(&inode->i_mutex);
> + atomic_dec(&parent->count);
> + deactivate_super(parent->root->sb);
> + printk(KERN_INFO
> + "Race in container_clone() - leaking container %s\n",
> + nodename);
> + goto again;
> + }
> +
> + /* All seems fine. Finish by moving the task into the new container */
> + ret = attach_task(child, tsk);
> + mutex_unlock(&manage_mutex);
> +
> + out_release:
> + mutex_unlock(&inode->i_mutex);
> + atomic_dec(&parent->count);
> + deactivate_super(parent->root->sb);
> + return ret;
> +}
> +
> +int container_is_descendant(const struct container *cont) {
> + int ret;
> + struct container *target;
> + container_lock();
> + target = current->containers->container[cont->hierarchy];
> + while (cont != target && cont!= target->top_container) {
> + cont = cont->parent;
> + }
> + ret = (cont == target);
> + container_unlock();
> + return ret;
> +}
> +
> +/**
> + * container_init_early - initialize containers at system boot
> + *
> + * Description: Initialize the container housekeeping structures
> + **/
>
> int __init container_init_early(void)
> {
> - struct task_struct *tsk = current;
> + int i;
> +
> + kref_init(&init_container_group.ref);
> + get_container_group(&init_container_group);
> + INIT_LIST_HEAD(&init_container_group.list);
> + container_group_count = 1;
> +
> + for (i = 0; i < CONFIG_MAX_CONTAINER_HIERARCHIES; i++) {
> + struct containerfs_root *root = &rootnode[i];
> + struct container *cont = &root->top_container;
> + INIT_LIST_HEAD(&root->subsys_list);
> + root->number_of_containers = 1;
> +
> + cont->root = root;
> + cont->hierarchy = i;
> + INIT_LIST_HEAD(&cont->sibling);
> + INIT_LIST_HEAD(&cont->children);
> + cont->top_container = cont;
> + atomic_set(&cont->count, 1);
> +
> + init_container_group.container[i] = cont;
> + }
> + init_task.containers = &init_container_group;
>
> - tsk->container = &top_container;
> return 0;
> }
>
> /**
> - * container_init - initialize containers at system boot
> - *
> - * Description: Initialize top_container and the container internal file system,
> + * container_init - register container filesystem and /proc file
> **/
>
> int __init container_init(void)
> {
> - struct dentry *root;
> int err;
> -
> - init_task.container = &top_container;
> + struct proc_dir_entry *entry;
>
> err = register_filesystem(&container_fs_type);
> if (err < 0)
> goto out;
> - container_mount = kern_mount(&container_fs_type);
> - if (IS_ERR(container_mount)) {
> - printk(KERN_ERR "container: could not mount!\n");
> - err = PTR_ERR(container_mount);
> - container_mount = NULL;
> - goto out;
> - }
> - root = container_mount->mnt_sb->s_root;
> - root->d_fsdata = &top_container;
> - root->d_inode->i_nlink++;
> - top_container.dentry = root;
> - root->d_inode->i_op = &container_dir_inode_operations;
> - number_of_containers = 1;
> - err = container_populate_dir(&top_container);
> +
> + entry = create_proc_entry("containers", 0, NULL);
> + if (entry)
> + entry->proc_fops = &proc_containerstats_operations;
> +
> out:
> return err;
> }
>
> +#include <asm/proto.h>

I did have a problem with this include. On s390 it didn't exist so I've
just been running without it (with no problems). A quick 'find'
suggests it only exists on x86_64, so I'd expect failures on all other
arches.

-serge