cgroup: introduce cgroup_taskset and use it in subsys->can_attach(), cancel_attach() and attach() Currently, there's no way to pass multiple tasks to cgroup_subsys methods necessitating the need for separate per-process and per-task methods. This patch introduces cgroup_taskset which can be used to pass multiple tasks and their associated cgroups to cgroup_subsys methods. Three methods - can_attach(), cancel_attach() and attach() - are converted to use cgroup_taskset. This unifies passed parameters so that all methods have access to all information. Conversions in this patchset are identical and don't introduce any behavior change. -v2: documentation updated as per Paul Menage's suggestion. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com> Acked-by: Paul Menage <paul@paulmenage.org> Acked-by: Li Zefan <lizf@cn.fujitsu.com> Cc: Balbir Singh <bsingharora@gmail.com> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: James Morris <jmorris@namei.org>
diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt index 9c452ef..8a2f302 100644 --- a/Documentation/cgroups/cgroups.txt +++ b/Documentation/cgroups/cgroups.txt
@@ -594,15 +594,25 @@ called multiple times against a cgroup. int can_attach(struct cgroup_subsys *ss, struct cgroup *cgrp, - struct task_struct *task) + struct cgroup_taskset *tset) (cgroup_mutex held by caller) -Called prior to moving a task into a cgroup; if the subsystem -returns an error, this will abort the attach operation. If a NULL -task is passed, then a successful result indicates that *any* -unspecified task can be moved into the cgroup. Note that this isn't -called on a fork. If this method returns 0 (success) then this should -remain valid while the caller holds cgroup_mutex and it is ensured that either +Called prior to moving one or more tasks into a cgroup; if the +subsystem returns an error, this will abort the attach operation. +@tset contains the tasks to be attached and is guaranteed to have at +least one task in it. + +If there are multiple tasks in the taskset, then: + - it's guaranteed that all are from the same thread group + - @tset contains all tasks from the thread group whether or not + they're switching cgroups + - the first task is the leader + +Each @tset entry also contains the task's old cgroup and tasks which +aren't switching cgroup can be skipped easily using the +cgroup_taskset_for_each() iterator. Note that this isn't called on a +fork. If this method returns 0 (success) then this should remain valid +while the caller holds cgroup_mutex and it is ensured that either attach() or cancel_attach() will be called in future. int can_attach_task(struct cgroup *cgrp, struct task_struct *tsk); @@ -613,14 +623,14 @@ can_attach. void cancel_attach(struct cgroup_subsys *ss, struct cgroup *cgrp, - struct task_struct *task, bool threadgroup) + struct cgroup_taskset *tset) (cgroup_mutex held by caller) Called when a task attach operation has failed after can_attach() has succeeded. A subsystem whose can_attach() has some side-effects should provide this function, so that the subsystem can implement a rollback. If not, not necessary. This will be called only about subsystems whose can_attach() operation have -succeeded. +succeeded. The parameters are identical to can_attach(). void pre_attach(struct cgroup *cgrp); (cgroup_mutex held by caller) @@ -629,11 +639,12 @@ attach_task. Needed by cpuset. void attach(struct cgroup_subsys *ss, struct cgroup *cgrp, - struct cgroup *old_cgrp, struct task_struct *task) + struct cgroup_taskset *tset) (cgroup_mutex held by caller) Called after the task has been attached to the cgroup, to allow any post-attachment activity that requires memory allocations or blocking. +The parameters are identical to can_attach(). void attach_task(struct cgroup *cgrp, struct task_struct *tsk); (cgroup_mutex held by caller)
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 1b7f9d5..34256ad 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h
@@ -457,6 +457,28 @@ void cgroup_release_and_wakeup_rmdir(struct cgroup_subsys_state *css); /* + * Control Group taskset, used to pass around set of tasks to cgroup_subsys + * methods. + */ +struct cgroup_taskset; +struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset); +struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset); +struct cgroup *cgroup_taskset_cur_cgroup(struct cgroup_taskset *tset); +int cgroup_taskset_size(struct cgroup_taskset *tset); + +/** + * cgroup_taskset_for_each - iterate cgroup_taskset + * @task: the loop cursor + * @skip_cgrp: skip if task's cgroup matches this, %NULL to iterate through all + * @tset: taskset to iterate + */ +#define cgroup_taskset_for_each(task, skip_cgrp, tset) \ + for ((task) = cgroup_taskset_first((tset)); (task); \ + (task) = cgroup_taskset_next((tset))) \ + if (!(skip_cgrp) || \ + cgroup_taskset_cur_cgroup((tset)) != (skip_cgrp)) + +/* * Control Group subsystem type. * See Documentation/cgroups/cgroups.txt for details */ @@ -467,14 +489,14 @@ int (*pre_destroy)(struct cgroup_subsys *ss, struct cgroup *cgrp); void (*destroy)(struct cgroup_subsys *ss, struct cgroup *cgrp); int (*can_attach)(struct cgroup_subsys *ss, struct cgroup *cgrp, - struct task_struct *tsk); + struct cgroup_taskset *tset); int (*can_attach_task)(struct cgroup *cgrp, struct task_struct *tsk); void (*cancel_attach)(struct cgroup_subsys *ss, struct cgroup *cgrp, - struct task_struct *tsk); + struct cgroup_taskset *tset); void (*pre_attach)(struct cgroup *cgrp); void (*attach_task)(struct cgroup *cgrp, struct task_struct *tsk); void (*attach)(struct cgroup_subsys *ss, struct cgroup *cgrp, - struct cgroup *old_cgrp, struct task_struct *tsk); + struct cgroup_taskset *tset); void (*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);
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 0f2d005..41ee01e 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c
@@ -1757,11 +1757,85 @@ } EXPORT_SYMBOL_GPL(cgroup_path); +/* + * Control Group taskset + */ struct task_and_cgroup { struct task_struct *task; struct cgroup *cgrp; }; +struct cgroup_taskset { + struct task_and_cgroup single; + struct flex_array *tc_array; + int tc_array_len; + int idx; + struct cgroup *cur_cgrp; +}; + +/** + * cgroup_taskset_first - reset taskset and return the first task + * @tset: taskset of interest + * + * @tset iteration is initialized and the first task is returned. + */ +struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset) +{ + if (tset->tc_array) { + tset->idx = 0; + return cgroup_taskset_next(tset); + } else { + tset->cur_cgrp = tset->single.cgrp; + return tset->single.task; + } +} +EXPORT_SYMBOL_GPL(cgroup_taskset_first); + +/** + * cgroup_taskset_next - iterate to the next task in taskset + * @tset: taskset of interest + * + * Return the next task in @tset. Iteration must have been initialized + * with cgroup_taskset_first(). + */ +struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset) +{ + struct task_and_cgroup *tc; + + if (!tset->tc_array || tset->idx >= tset->tc_array_len) + return NULL; + + tc = flex_array_get(tset->tc_array, tset->idx++); + tset->cur_cgrp = tc->cgrp; + return tc->task; +} +EXPORT_SYMBOL_GPL(cgroup_taskset_next); + +/** + * cgroup_taskset_cur_cgroup - return the matching cgroup for the current task + * @tset: taskset of interest + * + * Return the cgroup for the current (last returned) task of @tset. This + * function must be preceded by either cgroup_taskset_first() or + * cgroup_taskset_next(). + */ +struct cgroup *cgroup_taskset_cur_cgroup(struct cgroup_taskset *tset) +{ + return tset->cur_cgrp; +} +EXPORT_SYMBOL_GPL(cgroup_taskset_cur_cgroup); + +/** + * cgroup_taskset_size - return the number of tasks in taskset + * @tset: taskset of interest + */ +int cgroup_taskset_size(struct cgroup_taskset *tset) +{ + return tset->tc_array ? tset->tc_array_len : 1; +} +EXPORT_SYMBOL_GPL(cgroup_taskset_size); + + /* * cgroup_task_migrate - move a task from one cgroup to another. * @@ -1842,6 +1916,7 @@ struct cgroup_subsys *ss, *failed_ss = NULL; struct cgroup *oldcgrp; struct cgroupfs_root *root = cgrp->root; + struct cgroup_taskset tset = { }; /* @tsk either already exited or can't exit until the end */ if (tsk->flags & PF_EXITING) @@ -1852,9 +1927,12 @@ if (cgrp == oldcgrp) return 0; + tset.single.task = tsk; + tset.single.cgrp = oldcgrp; + for_each_subsys(root, ss) { if (ss->can_attach) { - retval = ss->can_attach(ss, cgrp, tsk); + retval = ss->can_attach(ss, cgrp, &tset); if (retval) { /* * Remember on which subsystem the can_attach() @@ -1885,7 +1963,7 @@ if (ss->attach_task) ss->attach_task(cgrp, tsk); if (ss->attach) - ss->attach(ss, cgrp, oldcgrp, tsk); + ss->attach(ss, cgrp, &tset); } synchronize_rcu(); @@ -1907,7 +1985,7 @@ */ break; if (ss->cancel_attach) - ss->cancel_attach(ss, cgrp, tsk); + ss->cancel_attach(ss, cgrp, &tset); } } return retval; @@ -2023,6 +2101,7 @@ struct task_struct *tsk; struct task_and_cgroup *tc; struct flex_array *group; + struct cgroup_taskset tset = { }; /* * we need to make sure we have css_sets for all the tasks we're * going to move -before- we actually start moving them, so that in @@ -2089,6 +2168,8 @@ } while_each_thread(leader, tsk); /* remember the number of threads in the array for later. */ group_size = i; + tset.tc_array = group; + tset.tc_array_len = group_size; read_unlock(&tasklist_lock); /* methods shouldn't be called if no task is actually migrating */ @@ -2101,7 +2182,7 @@ */ for_each_subsys(root, ss) { if (ss->can_attach) { - retval = ss->can_attach(ss, cgrp, leader); + retval = ss->can_attach(ss, cgrp, &tset); if (retval) { failed_ss = ss; goto out_cancel_attach; @@ -2183,10 +2264,8 @@ * being moved, this call will need to be reworked to communicate that. */ for_each_subsys(root, ss) { - if (ss->attach) { - tc = flex_array_get(group, 0); - ss->attach(ss, cgrp, tc->cgrp, tc->task); - } + if (ss->attach) + ss->attach(ss, cgrp, &tset); } /* @@ -2208,11 +2287,11 @@ for_each_subsys(root, ss) { if (ss == failed_ss) { if (cancel_failed_ss && ss->cancel_attach) - ss->cancel_attach(ss, cgrp, leader); + ss->cancel_attach(ss, cgrp, &tset); break; } if (ss->cancel_attach) - ss->cancel_attach(ss, cgrp, leader); + ss->cancel_attach(ss, cgrp, &tset); } } out_put_tasks:
diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c index e411a60..e95c6fb 100644 --- a/kernel/cgroup_freezer.c +++ b/kernel/cgroup_freezer.c
@@ -159,7 +159,7 @@ */ static int freezer_can_attach(struct cgroup_subsys *ss, struct cgroup *new_cgroup, - struct task_struct *task) + struct cgroup_taskset *tset) { struct freezer *freezer;
diff --git a/kernel/cpuset.c b/kernel/cpuset.c index 9fe58c4..512bd59 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c
@@ -1371,10 +1371,10 @@ } /* Called by cgroups to determine if a cpuset is usable; cgroup_mutex held */ -static int cpuset_can_attach(struct cgroup_subsys *ss, struct cgroup *cont, - struct task_struct *tsk) +static int cpuset_can_attach(struct cgroup_subsys *ss, struct cgroup *cgrp, + struct cgroup_taskset *tset) { - struct cpuset *cs = cgroup_cs(cont); + struct cpuset *cs = cgroup_cs(cgrp); if (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed)) return -ENOSPC; @@ -1387,7 +1387,7 @@ * set_cpus_allowed_ptr() on all attached tasks before cpus_allowed may * be changed. */ - if (tsk->flags & PF_THREAD_BOUND) + if (cgroup_taskset_first(tset)->flags & PF_THREAD_BOUND) return -EINVAL; return 0; @@ -1437,12 +1437,14 @@ cpuset_update_task_spread_flag(cs, tsk); } -static void cpuset_attach(struct cgroup_subsys *ss, struct cgroup *cont, - struct cgroup *oldcont, struct task_struct *tsk) +static void cpuset_attach(struct cgroup_subsys *ss, struct cgroup *cgrp, + struct cgroup_taskset *tset) { struct mm_struct *mm; - struct cpuset *cs = cgroup_cs(cont); - struct cpuset *oldcs = cgroup_cs(oldcont); + struct task_struct *tsk = cgroup_taskset_first(tset); + struct cgroup *oldcgrp = cgroup_taskset_cur_cgroup(tset); + struct cpuset *cs = cgroup_cs(cgrp); + struct cpuset *oldcs = cgroup_cs(oldcgrp); /* * Change mm, possibly for multiple threads in a threadgroup. This is
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 6aff93c..81640e7 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c
@@ -5298,8 +5298,9 @@ static int mem_cgroup_can_attach(struct cgroup_subsys *ss, struct cgroup *cgroup, - struct task_struct *p) + struct cgroup_taskset *tset) { + struct task_struct *p = cgroup_taskset_first(tset); int ret = 0; struct mem_cgroup *memcg = mem_cgroup_from_cont(cgroup); @@ -5337,7 +5338,7 @@ static void mem_cgroup_cancel_attach(struct cgroup_subsys *ss, struct cgroup *cgroup, - struct task_struct *p) + struct cgroup_taskset *tset) { mem_cgroup_clear_mc(); } @@ -5454,9 +5455,9 @@ static void mem_cgroup_move_task(struct cgroup_subsys *ss, struct cgroup *cont, - struct cgroup *old_cont, - struct task_struct *p) + struct cgroup_taskset *tset) { + struct task_struct *p = cgroup_taskset_first(tset); struct mm_struct *mm = get_task_mm(p); if (mm) { @@ -5471,19 +5472,18 @@ #else /* !CONFIG_MMU */ static int mem_cgroup_can_attach(struct cgroup_subsys *ss, struct cgroup *cgroup, - struct task_struct *p) + struct cgroup_taskset *tset) { return 0; } static void mem_cgroup_cancel_attach(struct cgroup_subsys *ss, struct cgroup *cgroup, - struct task_struct *p) + struct cgroup_taskset *tset) { } static void mem_cgroup_move_task(struct cgroup_subsys *ss, struct cgroup *cont, - struct cgroup *old_cont, - struct task_struct *p) + struct cgroup_taskset *tset) { } #endif
diff --git a/security/device_cgroup.c b/security/device_cgroup.c index 4450fbe..8b5b5d8 100644 --- a/security/device_cgroup.c +++ b/security/device_cgroup.c
@@ -62,11 +62,12 @@ struct cgroup_subsys devices_subsys; static int devcgroup_can_attach(struct cgroup_subsys *ss, - struct cgroup *new_cgroup, struct task_struct *task) + struct cgroup *new_cgrp, struct cgroup_taskset *set) { - if (current != task && !capable(CAP_SYS_ADMIN)) - return -EPERM; + struct task_struct *task = cgroup_taskset_first(set); + if (current != task && !capable(CAP_SYS_ADMIN)) + return -EPERM; return 0; }