On Thu 15-08-13 12:02:29, Tejun Heo wrote:
> cgroup_event is only available in memcg now. Let's brand it that way.
> While at it, add a comment encouraging deprecation of the feature and
> remove the respective section from cgroup documentation.
>
> This patch is cosmetic.
>
> v2: Index in cgroups.txt updated accordingly as suggested by Li Zefan.
OK, Documentation/cgroups/memory.txt contains a documentation for all
interfaces so this can go.
>
> Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
> Cc: Li Zefan <lizefan@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxx>
> ---
> Documentation/cgroups/cgroups.txt | 20 --------------
> mm/memcontrol.c | 57 +++++++++++++++++++++++++--------------
> 2 files changed, 37 insertions(+), 40 deletions(-)
>
> diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt
> index 638bf17..821de56 100644
> --- a/Documentation/cgroups/cgroups.txt
> +++ b/Documentation/cgroups/cgroups.txt
> @@ -24,7 +24,6 @@ CONTENTS:
> 2.1 Basic Usage
> 2.2 Attaching processes
> 2.3 Mounting hierarchies by name
> - 2.4 Notification API
> 3. Kernel API
> 3.1 Overview
> 3.2 Synchronization
> @@ -472,25 +471,6 @@ you give a subsystem a name.
> The name of the subsystem appears as part of the hierarchy description
> in /proc/mounts and /proc/<pid>/cgroups.
>
> -2.4 Notification API
> ---------------------
> -
> -There is mechanism which allows to get notifications about changing
> -status of a cgroup.
> -
> -To register a new notification handler you need to:
> - - create a file descriptor for event notification using eventfd(2);
> - - open a control file to be monitored (e.g. memory.usage_in_bytes);
> - - write "<event_fd> <control_fd> <args>" to cgroup.event_control.
> - Interpretation of args is defined by control file implementation;
> -
> -eventfd will be woken up by control file implementation or when the
> -cgroup is removed.
> -
> -To unregister a notification handler just close eventfd.
> -
> -NOTE: Support of notifications should be implemented for the control
> -file. See documentation for the subsystem.
>
> 3. Kernel API
> =============
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 8663d6c..2f0a8e1 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -243,7 +243,7 @@ struct mem_cgroup_eventfd_list {
> /*
> * cgroup_event represents events which userspace want to receive.
> */
> -struct cgroup_event {
> +struct mem_cgroup_event {
> /*
> * memcg which the event belongs to.
> */
> @@ -5973,14 +5973,27 @@ static void kmem_cgroup_css_offline(struct mem_cgroup *memcg)
> #endif
>
> /*
> + * DO NOT USE IN NEW FILES.
> + *
> + * "cgroup.event_control" implementation.
> + *
> + * This is way over-engineered. It tries to support fully configureable
> + * events for each user. Such level of flexibility is completely
> + * unnecessary especially in the light of the planned unified hierarchy.
> + *
> + * Please deprecate this and replace with something simpler if at all
> + * possible.
> + */
> +
> +/*
> * Unregister event and free resources.
> *
> * Gets called from workqueue.
> */
> -static void cgroup_event_remove(struct work_struct *work)
> +static void memcg_event_remove(struct work_struct *work)
> {
> - struct cgroup_event *event = container_of(work, struct cgroup_event,
> - remove);
> + struct mem_cgroup_event *event =
> + container_of(work, struct mem_cgroup_event, remove);
> struct mem_cgroup *memcg = event->memcg;
>
> remove_wait_queue(event->wqh, &event->wait);
> @@ -6000,11 +6013,11 @@ static void cgroup_event_remove(struct work_struct *work)
> *
> * Called with wqh->lock held and interrupts disabled.
> */
> -static int cgroup_event_wake(wait_queue_t *wait, unsigned mode,
> - int sync, void *key)
> +static int memcg_event_wake(wait_queue_t *wait, unsigned mode,
> + int sync, void *key)
> {
> - struct cgroup_event *event = container_of(wait,
> - struct cgroup_event, wait);
> + struct mem_cgroup_event *event =
> + container_of(wait, struct mem_cgroup_event, wait);
> struct mem_cgroup *memcg = event->memcg;
> unsigned long flags = (unsigned long)key;
>
> @@ -6033,27 +6046,29 @@ static int cgroup_event_wake(wait_queue_t *wait, unsigned mode,
> return 0;
> }
>
> -static void cgroup_event_ptable_queue_proc(struct file *file,
> +static void memcg_event_ptable_queue_proc(struct file *file,
> wait_queue_head_t *wqh, poll_table *pt)
> {
> - struct cgroup_event *event = container_of(pt,
> - struct cgroup_event, pt);
> + struct mem_cgroup_event *event =
> + container_of(pt, struct mem_cgroup_event, pt);
>
> event->wqh = wqh;
> add_wait_queue(wqh, &event->wait);
> }
>
> /*
> + * DO NOT USE IN NEW FILES.
> + *
> * Parse input and register new cgroup event handler.
> *
> * Input must be in format '<event_fd> <control_fd> <args>'.
> * Interpretation of args is defined by control file implementation.
> */
> -static int cgroup_write_event_control(struct cgroup_subsys_state *css,
> - struct cftype *cft, const char *buffer)
> +static int memcg_write_event_control(struct cgroup_subsys_state *css,
> + struct cftype *cft, const char *buffer)
> {
> struct mem_cgroup *memcg = mem_cgroup_from_css(css);
> - struct cgroup_event *event;
> + struct mem_cgroup_event *event;
> struct cgroup_subsys_state *cfile_css;
> unsigned int efd, cfd;
> struct file *efile;
> @@ -6078,9 +6093,9 @@ static int cgroup_write_event_control(struct cgroup_subsys_state *css,
>
> event->memcg = memcg;
> INIT_LIST_HEAD(&event->list);
> - init_poll_funcptr(&event->pt, cgroup_event_ptable_queue_proc);
> - init_waitqueue_func_entry(&event->wait, cgroup_event_wake);
> - INIT_WORK(&event->remove, cgroup_event_remove);
> + init_poll_funcptr(&event->pt, memcg_event_ptable_queue_proc);
> + init_waitqueue_func_entry(&event->wait, memcg_event_wake);
> + INIT_WORK(&event->remove, memcg_event_remove);
>
> efile = eventfd_fget(efd);
> if (IS_ERR(efile)) {
> @@ -6111,6 +6126,8 @@ static int cgroup_write_event_control(struct cgroup_subsys_state *css,
> * to be done via struct cftype but cgroup core no longer knows
> * about these events. The following is crude but the whole thing
> * is for compatibility anyway.
> + *
> + * DO NOT ADD NEW FILES.
> */
> name = cfile->f_dentry->d_name.name;
>
> @@ -6221,8 +6238,8 @@ static struct cftype mem_cgroup_files[] = {
> .read_u64 = mem_cgroup_hierarchy_read,
> },
> {
> - .name = "cgroup.event_control",
> - .write_string = cgroup_write_event_control,
> + .name = "cgroup.event_control", /* XXX: for compat */
> + .write_string = memcg_write_event_control,
> .flags = CFTYPE_NO_PREFIX,
> .mode = S_IWUGO,
> },
> @@ -6555,7 +6572,7 @@ static void mem_cgroup_invalidate_reclaim_iterators(struct mem_cgroup *memcg)
> static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
> {
> struct mem_cgroup *memcg = mem_cgroup_from_css(css);
> - struct cgroup_event *event, *tmp;
> + struct mem_cgroup_event *event, *tmp;
>
> /*
> * Unregister events and notify userspace.
> --
> 1.8.3.1
>
> --
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--
Michal Hocko
SUSE Labs
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