From 5153faac18d293fc7abb19ff7034683fbcd82dc7 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Thu, 24 Oct 2019 12:03:51 -0700 Subject: cgroup: remove cgroup_enable_task_cg_lists() optimization cgroup_enable_task_cg_lists() is used to lazyily initialize task cgroup associations on the first use to reduce fork / exit overheads on systems which don't use cgroup. Unfortunately, locking around it has never been actually correct and its value is dubious given how the vast majority of systems use cgroup right away from boot. This patch removes the optimization. For now, replace the cg_list based branches with WARN_ON_ONCE()'s to be on the safe side. We can simplify the logic further in the future. Signed-off-by: Tejun Heo Reported-by: Oleg Nesterov Signed-off-by: Tejun Heo --- include/linux/cgroup.h | 1 - 1 file changed, 1 deletion(-) (limited to 'include/linux/cgroup.h') diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 3ba3e6da13a6..f6b048902d6c 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -150,7 +150,6 @@ struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset, struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset, struct cgroup_subsys_state **dst_cssp); -void cgroup_enable_task_cg_lists(void); void css_task_iter_start(struct cgroup_subsys_state *css, unsigned int flags, struct css_task_iter *it); struct task_struct *css_task_iter_next(struct css_task_iter *it); -- cgit v1.2.3 From 67c0496e87d193b8356d2af49ab95e8a1b954b3c Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 4 Nov 2019 15:54:30 -0800 Subject: kernfs: convert kernfs_node->id from union kernfs_node_id to u64 kernfs_node->id is currently a union kernfs_node_id which represents either a 32bit (ino, gen) pair or u64 value. I can't see much value in the usage of the union - all that's needed is a 64bit ID which the current code is already limited to. Using a union makes the code unnecessarily complicated and prevents using 64bit ino without adding practical benefits. This patch drops union kernfs_node_id and makes kernfs_node->id a u64. ino is stored in the lower 32bits and gen upper. Accessors - kernfs[_id]_ino() and kernfs[_id]_gen() - are added to retrieve the ino and gen. This simplifies ID handling less cumbersome and will allow using 64bit inos on supported archs. This patch doesn't make any functional changes. Signed-off-by: Tejun Heo Reviewed-by: Greg Kroah-Hartman Cc: Namhyung Kim Cc: Jens Axboe Cc: Alexei Starovoitov --- include/linux/cgroup.h | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-) (limited to 'include/linux/cgroup.h') diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index f6b048902d6c..815fff49d555 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -616,7 +616,7 @@ static inline bool cgroup_is_populated(struct cgroup *cgrp) /* returns ino associated with a cgroup */ static inline ino_t cgroup_ino(struct cgroup *cgrp) { - return cgrp->kn->id.ino; + return kernfs_ino(cgrp->kn); } /* cft/css accessors for cftype->write() operation */ @@ -687,13 +687,12 @@ static inline void cgroup_kthread_ready(void) current->no_cgroup_migration = 0; } -static inline union kernfs_node_id *cgroup_get_kernfs_id(struct cgroup *cgrp) +static inline u64 cgroup_get_kernfs_id(struct cgroup *cgrp) { - return &cgrp->kn->id; + return cgrp->kn->id; } -void cgroup_path_from_kernfs_id(const union kernfs_node_id *id, - char *buf, size_t buflen); +void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen); #else /* !CONFIG_CGROUPS */ struct cgroup_subsys_state; @@ -718,9 +717,9 @@ static inline int cgroup_init_early(void) { return 0; } static inline int cgroup_init(void) { return 0; } static inline void cgroup_init_kthreadd(void) {} static inline void cgroup_kthread_ready(void) {} -static inline union kernfs_node_id *cgroup_get_kernfs_id(struct cgroup *cgrp) +static inline union u64 cgroup_get_kernfs_id(struct cgroup *cgrp) { - return NULL; + return 0; } static inline struct cgroup *cgroup_parent(struct cgroup *cgrp) @@ -739,8 +738,8 @@ static inline bool task_under_cgroup_hierarchy(struct task_struct *task, return true; } -static inline void cgroup_path_from_kernfs_id(const union kernfs_node_id *id, - char *buf, size_t buflen) {} +static inline void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen) +{} #endif /* !CONFIG_CGROUPS */ #ifdef CONFIG_CGROUPS -- cgit v1.2.3 From 743210386c0354a2f8ef3d697353c7d8477fa81d Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 4 Nov 2019 15:54:30 -0800 Subject: cgroup: use cgrp->kn->id as the cgroup ID cgroup ID is currently allocated using a dedicated per-hierarchy idr and used internally and exposed through tracepoints and bpf. This is confusing because there are tracepoints and other interfaces which use the cgroupfs ino as IDs. The preceding changes made kn->id exposed as ino as 64bit ino on supported archs or ino+gen (low 32bits as ino, high gen). There's no reason for cgroup to use different IDs. The kernfs IDs are unique and userland can easily discover them and map them back to paths using standard file operations. This patch replaces cgroup IDs with kernfs IDs. * cgroup_id() is added and all cgroup ID users are converted to use it. * kernfs_node creation is moved to earlier during cgroup init so that cgroup_id() is available during init. * While at it, s/cgroup/cgrp/ in psi helpers for consistency. * Fallback ID value is changed to 1 to be consistent with root cgroup ID. Signed-off-by: Tejun Heo Reviewed-by: Greg Kroah-Hartman Cc: Namhyung Kim --- include/linux/cgroup.h | 17 +++++++---------- 1 file changed, 7 insertions(+), 10 deletions(-) (limited to 'include/linux/cgroup.h') diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 815fff49d555..d7ddebd0cdec 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -304,6 +304,11 @@ void css_task_iter_end(struct css_task_iter *it); * Inline functions. */ +static inline u64 cgroup_id(struct cgroup *cgrp) +{ + return cgrp->kn->id; +} + /** * css_get - obtain a reference on the specified css * @css: target css @@ -565,7 +570,7 @@ static inline bool cgroup_is_descendant(struct cgroup *cgrp, { if (cgrp->root != ancestor->root || cgrp->level < ancestor->level) return false; - return cgrp->ancestor_ids[ancestor->level] == ancestor->id; + return cgrp->ancestor_ids[ancestor->level] == cgroup_id(ancestor); } /** @@ -687,17 +692,13 @@ static inline void cgroup_kthread_ready(void) current->no_cgroup_migration = 0; } -static inline u64 cgroup_get_kernfs_id(struct cgroup *cgrp) -{ - return cgrp->kn->id; -} - void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen); #else /* !CONFIG_CGROUPS */ struct cgroup_subsys_state; struct cgroup; +static inline u64 cgroup_id(struct cgroup *cgrp) { return 1; } static inline void css_get(struct cgroup_subsys_state *css) {} static inline void css_put(struct cgroup_subsys_state *css) {} static inline int cgroup_attach_task_all(struct task_struct *from, @@ -717,10 +718,6 @@ static inline int cgroup_init_early(void) { return 0; } static inline int cgroup_init(void) { return 0; } static inline void cgroup_init_kthreadd(void) {} static inline void cgroup_kthread_ready(void) {} -static inline union u64 cgroup_get_kernfs_id(struct cgroup *cgrp) -{ - return 0; -} static inline struct cgroup *cgroup_parent(struct cgroup *cgrp) { -- cgit v1.2.3