Home » Mailing lists » Devel » [PATCH 00/10] Task Containers(V11): Introduction
| Re: [PATCH 07/10] Task Containers(V11): Automatic userspace notification of idle containers [message #15235 is a reply to message #15198] |
Mon, 23 July 2007 17:41  |
serue
Messages: 750
Registered: February 2006
|
Senior Member |
|
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Quoting menage@google.com (menage@google.com):
> This patch adds the following files to the container filesystem:
>
> notify_on_release - configures/reports whether the container subsystem should
> attempt to run a release script when this container becomes unused
>
> release_agent - configures/reports the release agent to be used for
> this hierarchy (top level in each hierarchy only)
>
> releasable - reports whether this container would have been auto-released if
> notify_on_release was true and a release agent was configured (mainly useful
> for debugging)
>
> To avoid locking issues, invoking the userspace release agent is done via a
> workqueue task; containers that need to have their release agents invoked by
> the workqueue task are linked on to a list.
Hi Paul,
my tree may be a bit crufty, but I had to #include <linux/kmod.h> in
order for this to compile on s390.
thanks,
-serge
> Signed-off-by: Paul Menage <menage@google.com>
> ---
>
> include/linux/container.h | 11 -
> kernel/container.c | 425 +++++++++++++++++++++++++++++++++++++++++-----
> 2 files changed, 393 insertions(+), 43 deletions(-)
>
> Index: container-2.6.22-rc6-mm1/include/linux/container.h
> ============================================================ =======
> --- container-2.6.22-rc6-mm1.orig/include/linux/container.h
> +++ container-2.6.22-rc6-mm1/include/linux/container.h
> @@ -77,10 +77,11 @@ static inline void css_get(struct contai
> * css_get()
> */
>
> +extern void __css_put(struct container_subsys_state *css);
> static inline void css_put(struct container_subsys_state *css)
> {
> if (!test_bit(CSS_ROOT, &css->flags))
> - atomic_dec(&css->refcnt);
> + __css_put(css);
> }
>
> struct container {
> @@ -112,6 +113,13 @@ struct container {
> * tasks in this container. Protected by css_group_lock
> */
> struct list_head css_groups;
> +
> + /*
> + * Linked list running through all containers that can
> + * potentially be reaped by the release agent. Protected by
> + * release_list_lock
> + */
> + struct list_head release_list;
> };
>
> /* A css_group is a structure holding pointers to a set of
> @@ -285,7 +293,6 @@ struct task_struct *container_iter_next(
> struct container_iter *it);
> void container_iter_end(struct container *cont, struct container_iter *it);
>
> -
> #else /* !CONFIG_CONTAINERS */
>
> static inline int container_init_early(void) { return 0; }
> Index: container-2.6.22-rc6-mm1/kernel/container.c
> ============================================================ =======
> --- container-2.6.22-rc6-mm1.orig/kernel/container.c
> +++ container-2.6.22-rc6-mm1/kernel/container.c
> @@ -44,6 +44,8 @@
> #include <linux/sort.h>
> #include <asm/atomic.h>
>
> +static DEFINE_MUTEX(container_mutex);
> +
> /* Generate an array of container subsystem pointers */
> #define SUBSYS(_x) &_x ## _subsys,
>
> @@ -82,6 +84,13 @@ struct containerfs_root {
>
> /* Hierarchy-specific flags */
> unsigned long flags;
> +
> + /* 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. We ensure that it's always a valid
> + * NUL-terminated string */
> + char release_agent_path[PATH_MAX];
> };
>
>
> @@ -109,7 +118,13 @@ static int need_forkexit_callback;
>
> /* bits in struct container flags field */
> enum {
> + /* Container is dead */
> CONT_REMOVED,
> + /* Container has previously had a child container or a task,
> + * but no longer (only if CONT_NOTIFY_ON_RELEASE is set) */
> + CONT_RELEASABLE,
> + /* Container requires release notifications to userspace */
> + CONT_NOTIFY_ON_RELEASE,
> };
>
> /* convenient tests for these bits */
> @@ -123,6 +138,19 @@ enum {
> ROOT_NOPREFIX, /* mounted subsystems have no named prefix */
> };
>
> +inline int container_is_releasable(const struct container *cont)
> +{
> + const int bits =
> + (1 << CONT_RELEASABLE) |
> + (1 << CONT_NOTIFY_ON_RELEASE);
> + return (cont->flags & bits) == bits;
> +}
> +
> +inline int notify_on_release(const struct container *cont)
> +{
> + return test_bit(CONT_NOTIFY_ON_RELEASE, &cont->flags);
> +}
> +
> /*
> * for_each_subsys() allows you to iterate on each subsystem attached to
> * an active hierarchy
> @@ -134,6 +162,14 @@ list_for_each_entry(_ss, &_root->subsys_
> #define for_each_root(_root) \
> list_for_each_entry(_root, &roots, root_list)
>
> +/* the list of containers eligible for automatic release. Protected by
> + * release_list_lock */
> +static LIST_HEAD(release_list);
> +static DEFINE_SPINLOCK(release_list_lock);
> +static void container_release_agent(struct work_struct *work);
> +static DECLARE_WORK(release_agent_work, container_release_agent);
> +static void check_for_release(struct container *cont);
> +
> /* Link structure for associating css_group objects with containers */
> struct cg_container_link {
> /*
> @@ -188,11 +224,8 @@ static int use_task_css_group_links;
> /*
> * unlink a css_group from the list and free it
> */
> -static void release_css_group(struct kref *k)
> +static void unlink_css_group(struct css_group *cg)
> {
> - struct css_group *cg = container_of(k, struct css_group, ref);
> - int i;
> -
> write_lock(&css_group_lock);
> list_del(&cg->list);
> css_group_count--;
> @@ -205,11 +238,39 @@ static void release_css_group(struct kre
> kfree(link);
> }
> write_unlock(&css_group_lock);
> - for (i = 0; i < CONTAINER_SUBSYS_COUNT; i++)
> - atomic_dec(&cg->subsys[i]->container->count);
> +}
> +
> +static void __release_css_group(struct kref *k, int taskexit)
> +{
> + int i;
> + struct css_group *cg = container_of(k, struct css_group, ref);
> +
> + unlink_css_group(cg);
> +
> + rcu_read_lock();
> + for (i = 0; i < CONTAINER_SUBSYS_COUNT; i++) {
> + struct container *cont = cg->subsys[i]->container;
> + if (atomic_dec_and_test(&cont->count) &&
> + notify_on_release(cont)) {
> + if (taskexit)
> + set_bit(CONT_RELEASABLE, &cont->flags);
> + check_for_release(cont);
> + }
> + }
> + rcu_read_unlock();
> kfree(cg);
> }
>
> +static void release_css_group(struct kref *k)
> +{
> + __release_css_group(k, 0);
> +}
> +
> +static void release_css_group_taskexit(struct kref *k)
> +{
> + __release_css_group(k, 1);
> +}
> +
> /*
> * refcounted get/put for css_group objects
> */
> @@ -223,6 +284,11 @@ static inline void put_css_group(struct
> kref_put(&cg->ref, release_css_group);
> }
>
> +static inline void put_css_group_taskexit(struct css_group *cg)
> +{
> + kref_put(&cg->ref, release_css_group_taskexit);
> +}
> +
> /*
> * find_existing_css_group() is a helper for
> * find_css_group(), and checks to see whether an existing
> @@ -464,8 +530,6 @@ static struct css_group *find_css_group(
> * update of a tasks container pointer by attach_task()
> */
>
> -static DEFINE_MUTEX(container_mutex);
> -
> /**
> * container_lock - lock out any changes to container structures
> *
> @@ -524,6 +588,13 @@ static void container_diput(struct dentr
> if (S_ISDIR(inode->i_mode)) {
> struct container *cont = dentry->d_fsdata;
> BUG_ON(!(container_is_removed(cont)));
> + /* It's possible for external users to be holding css
> + * reference counts on a container; css_put() needs to
> + * be able to access the container after decrementing
> + * the reference count in order to know if it needs to
> + * queue the container to be handled by the release
> + * agent */
> + synchronize_rcu();
> kfree(cont);
> }
> iput(inode);
> @@ -668,6 +739,8 @@ static int container_show_options(struct
> seq_printf(seq, ",%s", ss->name);
> if (test_bit(ROOT_NOPREFIX, &root->flags))
> seq_puts(seq, ",noprefix");
> + if (strlen(root->release_agent_path))
> + seq_printf(seq, ",release_agent=%s", root->release_agent_path);
> mutex_unlock(&container_mutex);
> return 0;
> }
> @@ -675,6 +748,7 @@ static int container_show_options(struct
> struct container_sb_opts {
> unsigned long subsys_bits;
> unsigned long flags;
> + char *release_agent;
> };
>
> /* Convert a hierarchy specifier into a bitmask of subsystems and
> @@ -686,6 +760,7 @@ static int parse_containerfs_options(cha
>
> opts->subsys_bits = 0;
> opts->flags = 0;
> + opts->release_agent = NULL;
>
> while ((token = strsep(&o, ",")) != NULL) {
> if (!*token)
> @@ -694,6 +769,15 @@ static int parse_containerfs_options(cha
> opts->subsys_bits = (1 << CONTAINER_SUBSYS_COUNT) - 1;
> } else if (!strcmp(token, "noprefix")) {
> set_bit(ROOT_NOPREFIX, &opts->flags);
> + } else if (!strncmp(token, "release_agent=", 14)) {
> + /* Specifying two release agents is forbidden */
> + if (opts->release_agent)
> + return -EINVAL;
> + opts->release_agent = kzalloc(PATH_MAX, GFP_KERNEL);
> + if (!opts->release_agent)
> + return -ENOMEM;
> + strnc
...
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