From 6f60eade2433cb3a38687d5f8a4f44b92c6c51bf Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Fri, 18 Sep 2015 17:54:23 -0400 Subject: cgroup: generalize obtaining the handles of and notifying cgroup files cgroup core handles creations and removals of cgroup interface files as described by cftypes. There are cases where the handle for a given file instance is necessary, for example, to generate a file modified event. Currently, this is handled by explicitly matching the callback method pointer and storing the file handle manually in cgroup_add_file(). While this simple approach works for cgroup core files, it can't for controller interface files. This patch generalizes cgroup interface file handle handling. struct cgroup_file is defined and each cftype can optionally tell cgroup core to store the file handle by setting ->file_offset. A file handle remains accessible as long as the containing css is accessible. Both "cgroup.procs" and "cgroup.events" are converted to use the new generic mechanism instead of hooking directly into cgroup_add_file(). Also, cgroup_file_notify() which takes a struct cgroup_file and generates a file modified event on it is added and replaces explicit kernfs_notify() invocations. This generalizes cgroup file handle handling and allows controllers to generate file modified notifications. Signed-off-by: Tejun Heo Cc: Li Zefan Cc: Johannes Weiner --- include/linux/cgroup-defs.h | 26 ++++++++++++++++++++++++-- include/linux/cgroup.h | 13 +++++++++++++ 2 files changed, 37 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h index 10d814bcd487..df589a097539 100644 --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -83,6 +83,17 @@ enum { __CFTYPE_NOT_ON_DFL = (1 << 17), /* not on default hierarchy */ }; +/* + * cgroup_file is the handle for a file instance created in a cgroup which + * is used, for example, to generate file changed notifications. This can + * be obtained by setting cftype->file_offset. + */ +struct cgroup_file { + /* do not access any fields from outside cgroup core */ + struct list_head node; /* anchored at css->files */ + struct kernfs_node *kn; +}; + /* * Per-subsystem/per-cgroup state maintained by the system. This is the * fundamental structural building block that controllers deal with. @@ -123,6 +134,9 @@ struct cgroup_subsys_state { */ u64 serial_nr; + /* all cgroup_files associated with this css */ + struct list_head files; + /* percpu_ref killing and RCU release */ struct rcu_head rcu_head; struct work_struct destroy_work; @@ -226,8 +240,8 @@ struct cgroup { int populated_cnt; struct kernfs_node *kn; /* cgroup kernfs entry */ - struct kernfs_node *procs_kn; /* kn for "cgroup.procs" */ - struct kernfs_node *events_kn; /* kn for "cgroup.events" */ + struct cgroup_file procs_file; /* handle for "cgroup.procs" */ + struct cgroup_file events_file; /* handle for "cgroup.events" */ /* * The bitmask of subsystems enabled on the child cgroups. @@ -335,6 +349,14 @@ struct cftype { /* CFTYPE_* flags */ unsigned int flags; + /* + * If non-zero, should contain the offset from the start of css to + * a struct cgroup_file field. cgroup will record the handle of + * the created file into it. The recorded handle can be used as + * long as the containing css remains accessible. + */ + unsigned int file_offset; + /* * Fields used for internal bookkeeping. Initialized automatically * during registration. diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 355bf2ed8867..fb717f2cba5b 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -490,6 +490,19 @@ static inline void pr_cont_cgroup_path(struct cgroup *cgrp) pr_cont_kernfs_path(cgrp->kn); } +/** + * cgroup_file_notify - generate a file modified event for a cgroup_file + * @cfile: target cgroup_file + * + * @cfile must have been obtained by setting cftype->file_offset. + */ +static inline void cgroup_file_notify(struct cgroup_file *cfile) +{ + /* might not have been created due to one of the CFTYPE selector flags */ + if (cfile->kn) + kernfs_notify(cfile->kn); +} + #else /* !CONFIG_CGROUPS */ struct cgroup_subsys_state; -- cgit v1.2.3