From 1d870b1ca80c3568d79d5e9df496d503bc351d91 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Wed, 5 Oct 2011 11:43:48 +1100 Subject: [PATCH] cgroups: allow subsystems to cancel a fork Let the subsystem's fork callback return an error value so that they can cancel a fork. This is going to be used by the task counter subsystem to implement the limit. Suggested-by: Oleg Nesterov Signed-off-by: Frederic Weisbecker Cc: Paul Menage Cc: Li Zefan Cc: Johannes Weiner Cc: Aditya Kali Cc: Oleg Nesterov Cc: Kay Sievers Cc: Tim Hockin Cc: Tejun Heo Acked-by: Kirill A. Shutemov Signed-off-by: Andrew Morton --- include/linux/cgroup.h | 20 ++++++++++++++------ kernel/cgroup.c | 23 +++++++++++++++++++---- kernel/cgroup_freezer.c | 6 ++++-- kernel/exit.c | 2 +- kernel/fork.c | 7 +++++-- 5 files changed, 43 insertions(+), 15 deletions(-) diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index b62cf5e2fdc4..9c8151ebde7f 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -17,10 +17,11 @@ #include #include +struct cgroup_subsys; + #ifdef CONFIG_CGROUPS struct cgroupfs_root; -struct cgroup_subsys; struct inode; struct cgroup; struct css_id; @@ -32,9 +33,11 @@ extern int cgroup_lock_is_held(void); extern bool cgroup_lock_live_group(struct cgroup *cgrp); extern void cgroup_unlock(void); extern void cgroup_fork(struct task_struct *p); -extern void cgroup_fork_callbacks(struct task_struct *p); +extern int cgroup_fork_callbacks(struct task_struct *p, + struct cgroup_subsys **failed_ss); extern void cgroup_post_fork(struct task_struct *p); -extern void cgroup_exit(struct task_struct *p, int run_callbacks); +extern void cgroup_exit(struct task_struct *p, int run_callbacks, + struct cgroup_subsys *failed_ss); extern int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry); extern int cgroup_load_subsys(struct cgroup_subsys *ss); @@ -479,7 +482,7 @@ struct cgroup_subsys { struct task_struct *tsk); void (*attach)(struct cgroup_subsys *ss, struct cgroup *cgrp, struct cgroup *old_cgrp, struct task_struct *tsk); - void (*fork)(struct cgroup_subsys *ss, struct task_struct *task); + int (*fork)(struct cgroup_subsys *ss, struct task_struct *task); void (*exit)(struct cgroup_subsys *ss, struct cgroup *cgrp, struct cgroup *old_cgrp, struct task_struct *task); int (*populate)(struct cgroup_subsys *ss, @@ -636,9 +639,14 @@ struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id); static inline int cgroup_init_early(void) { return 0; } static inline int cgroup_init(void) { return 0; } static inline void cgroup_fork(struct task_struct *p) {} -static inline void cgroup_fork_callbacks(struct task_struct *p) {} +static inline int cgroup_fork_callbacks(struct task_struct *p, + struct cgroup_subsys **failed_ss) +{ + return 0; +} static inline void cgroup_post_fork(struct task_struct *p) {} -static inline void cgroup_exit(struct task_struct *p, int callbacks) {} +static inline void cgroup_exit(struct task_struct *p, int callbacks, + struct cgroup_subsys *failed_ss) {} static inline void cgroup_lock(void) {} static inline void cgroup_unlock(void) {} diff --git a/kernel/cgroup.c b/kernel/cgroup.c index b0686b49dd4b..ca86a607eac2 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -4540,8 +4540,11 @@ void cgroup_fork(struct task_struct *child) * tasklist. No need to take any locks since no-one can * be operating on this task. */ -void cgroup_fork_callbacks(struct task_struct *child) +int cgroup_fork_callbacks(struct task_struct *child, + struct cgroup_subsys **failed_ss) { + int err; + if (need_forkexit_callback) { int i; /* @@ -4551,10 +4554,17 @@ void cgroup_fork_callbacks(struct task_struct *child) */ for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) { struct cgroup_subsys *ss = subsys[i]; - if (ss->fork) - ss->fork(ss, child); + if (ss->fork) { + err = ss->fork(ss, child); + if (err) { + *failed_ss = ss; + return err; + } + } } } + + return 0; } /** @@ -4612,7 +4622,8 @@ void cgroup_post_fork(struct task_struct *child) * which wards off any cgroup_attach_task() attempts, or task is a failed * fork, never visible to cgroup_attach_task. */ -void cgroup_exit(struct task_struct *tsk, int run_callbacks) +void cgroup_exit(struct task_struct *tsk, int run_callbacks, + struct cgroup_subsys *failed_ss) { struct css_set *cg; int i; @@ -4641,6 +4652,10 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks) */ for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) { struct cgroup_subsys *ss = subsys[i]; + + if (ss == failed_ss) + break; + if (ss->exit) { struct cgroup *old_cgrp = rcu_dereference_raw(cg->subsys[i])->cgroup; diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c index ee34627c4408..aaf24da38ea1 100644 --- a/kernel/cgroup_freezer.c +++ b/kernel/cgroup_freezer.c @@ -187,7 +187,7 @@ static int freezer_can_attach_task(struct cgroup *cgrp, struct cgroup *old_cgrp, return 0; } -static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task) +static int freezer_fork(struct cgroup_subsys *ss, struct task_struct *task) { struct freezer *freezer; @@ -207,7 +207,7 @@ static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task) * following check. */ if (!freezer->css.cgroup->parent) - return; + return 0; spin_lock_irq(&freezer->lock); BUG_ON(freezer->state == CGROUP_FROZEN); @@ -216,6 +216,8 @@ static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task) if (freezer->state == CGROUP_FREEZING) freeze_task(task, true); spin_unlock_irq(&freezer->lock); + + return 0; } /* diff --git a/kernel/exit.c b/kernel/exit.c index 7c8624c06efc..674ffe058a4f 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -993,7 +993,7 @@ NORET_TYPE void do_exit(long code) */ perf_event_exit_task(tsk); - cgroup_exit(tsk, 1); + cgroup_exit(tsk, 1, NULL); if (group_dead) disassociate_ctty(1); diff --git a/kernel/fork.c b/kernel/fork.c index dc34b62e3bf1..06750826cb71 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1084,6 +1084,7 @@ static struct task_struct *copy_process(unsigned long clone_flags, int retval; struct task_struct *p; int cgroup_callbacks_done = 0; + struct cgroup_subsys *cgroup_failed_ss = NULL; if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) return ERR_PTR(-EINVAL); @@ -1341,8 +1342,10 @@ static struct task_struct *copy_process(unsigned long clone_flags, /* Now that the task is set up, run cgroup callbacks if * necessary. We need to run them before the task is visible * on the tasklist. */ - cgroup_fork_callbacks(p); + retval = cgroup_fork_callbacks(p, &cgroup_failed_ss); cgroup_callbacks_done = 1; + if (retval) + goto bad_fork_free_pid; /* Need tasklist lock for parent etc handling! */ write_lock_irq(&tasklist_lock); @@ -1443,7 +1446,7 @@ bad_fork_cleanup_cgroup: #endif if (clone_flags & CLONE_THREAD) threadgroup_fork_read_unlock(current); - cgroup_exit(p, cgroup_callbacks_done); + cgroup_exit(p, cgroup_callbacks_done, cgroup_failed_ss); delayacct_tsk_free(p); module_put(task_thread_info(p)->exec_domain->module); bad_fork_cleanup_count: -- 2.39.5