clone3: allow spawning processes into cgroups
This adds support for creating a process in a different cgroup than its parent. Callers can limit and account processes and threads right from the moment they are spawned: - A service manager can directly spawn new services into dedicated cgroups. - A process can be directly created in a frozen cgroup and will be frozen as well. - The initial accounting jitter experienced by process supervisors and daemons is eliminated with this. - Threaded applications or even thread implementations can choose to create a specific cgroup layout where each thread is spawned directly into a dedicated cgroup. This feature is limited to the unified hierarchy. Callers need to pass a directory file descriptor for the target cgroup. The caller can choose to pass an O_PATH file descriptor. All usual migration restrictions apply, i.e. there can be no processes in inner nodes. In general, creating a process directly in a target cgroup adheres to all migration restrictions. One of the biggest advantages of this feature is that CLONE_INTO_GROUP does not need to grab the write side of the cgroup cgroup_threadgroup_rwsem. This global lock makes moving tasks/threads around super expensive. With clone3() this lock is avoided. Cc: Tejun Heo <tj@kernel.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Li Zefan <lizefan@huawei.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: cgroups@vger.kernel.org Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Christian Brauner
Tejun Heo
parent
f3553220d4
commit
ef2c41cf38
@ -628,8 +628,9 @@ struct cgroup_subsys {
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void (*cancel_attach)(struct cgroup_taskset *tset);
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void (*attach)(struct cgroup_taskset *tset);
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void (*post_attach)(void);
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int (*can_fork)(struct task_struct *task);
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void (*cancel_fork)(struct task_struct *task);
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int (*can_fork)(struct task_struct *task,
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struct css_set *cset);
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void (*cancel_fork)(struct task_struct *task, struct css_set *cset);
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void (*fork)(struct task_struct *task);
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void (*exit)(struct task_struct *task);
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void (*release)(struct task_struct *task);
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@ -27,6 +27,8 @@
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#include <linux/cgroup-defs.h>
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struct kernel_clone_args;
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#ifdef CONFIG_CGROUPS
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/*
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@ -119,9 +121,12 @@ int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
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struct pid *pid, struct task_struct *tsk);
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void cgroup_fork(struct task_struct *p);
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extern int cgroup_can_fork(struct task_struct *p);
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extern void cgroup_cancel_fork(struct task_struct *p);
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extern void cgroup_post_fork(struct task_struct *p);
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extern int cgroup_can_fork(struct task_struct *p,
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struct kernel_clone_args *kargs);
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extern void cgroup_cancel_fork(struct task_struct *p,
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struct kernel_clone_args *kargs);
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extern void cgroup_post_fork(struct task_struct *p,
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struct kernel_clone_args *kargs);
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void cgroup_exit(struct task_struct *p);
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void cgroup_release(struct task_struct *p);
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void cgroup_free(struct task_struct *p);
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@ -705,9 +710,12 @@ static inline int cgroupstats_build(struct cgroupstats *stats,
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struct dentry *dentry) { return -EINVAL; }
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static inline void cgroup_fork(struct task_struct *p) {}
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static inline int cgroup_can_fork(struct task_struct *p) { return 0; }
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static inline void cgroup_cancel_fork(struct task_struct *p) {}
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static inline void cgroup_post_fork(struct task_struct *p) {}
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static inline int cgroup_can_fork(struct task_struct *p,
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struct kernel_clone_args *kargs) { return 0; }
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static inline void cgroup_cancel_fork(struct task_struct *p,
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struct kernel_clone_args *kargs) {}
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static inline void cgroup_post_fork(struct task_struct *p,
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struct kernel_clone_args *kargs) {}
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static inline void cgroup_exit(struct task_struct *p) {}
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static inline void cgroup_release(struct task_struct *p) {}
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static inline void cgroup_free(struct task_struct *p) {}
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@ -13,6 +13,7 @@
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struct task_struct;
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struct rusage;
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union thread_union;
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struct css_set;
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/* All the bits taken by the old clone syscall. */
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#define CLONE_LEGACY_FLAGS 0xffffffffULL
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@ -29,6 +30,9 @@ struct kernel_clone_args {
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pid_t *set_tid;
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/* Number of elements in *set_tid */
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size_t set_tid_size;
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int cgroup;
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struct cgroup *cgrp;
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struct css_set *cset;
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};
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/*
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@ -35,6 +35,7 @@
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/* Flags for the clone3() syscall. */
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#define CLONE_CLEAR_SIGHAND 0x100000000ULL /* Clear any signal handler and reset to SIG_DFL. */
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#define CLONE_INTO_CGROUP 0x200000000ULL /* Clone into a specific cgroup given the right permissions. */
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/*
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* cloning flags intersect with CSIGNAL so can be used with unshare and clone3
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@ -81,6 +82,8 @@
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* @set_tid_size: This defines the size of the array referenced
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* in @set_tid. This cannot be larger than the
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* kernel's limit of nested PID namespaces.
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* @cgroup: If CLONE_INTO_CGROUP is specified set this to
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* a file descriptor for the cgroup.
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*
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* The structure is versioned by size and thus extensible.
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* New struct members must go at the end of the struct and
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@ -97,11 +100,13 @@ struct clone_args {
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__aligned_u64 tls;
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__aligned_u64 set_tid;
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__aligned_u64 set_tid_size;
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__aligned_u64 cgroup;
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};
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#endif
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#define CLONE_ARGS_SIZE_VER0 64 /* sizeof first published struct */
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#define CLONE_ARGS_SIZE_VER1 80 /* sizeof second published struct */
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#define CLONE_ARGS_SIZE_VER2 88 /* sizeof third published struct */
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/*
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* Scheduling policies
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@ -5881,8 +5881,7 @@ out:
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* @child: pointer to task_struct of forking parent process.
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*
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* A task is associated with the init_css_set until cgroup_post_fork()
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* attaches it to the parent's css_set. Empty cg_list indicates that
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* @child isn't holding reference to its css_set.
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* attaches it to the target css_set.
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*/
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void cgroup_fork(struct task_struct *child)
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{
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@ -5908,24 +5907,154 @@ static struct cgroup *cgroup_get_from_file(struct file *f)
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return cgrp;
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}
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/**
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* cgroup_css_set_fork - find or create a css_set for a child process
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* @kargs: the arguments passed to create the child process
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*
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* This functions finds or creates a new css_set which the child
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* process will be attached to in cgroup_post_fork(). By default,
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* the child process will be given the same css_set as its parent.
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*
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* If CLONE_INTO_CGROUP is specified this function will try to find an
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* existing css_set which includes the requested cgroup and if not create
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* a new css_set that the child will be attached to later. If this function
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* succeeds it will hold cgroup_threadgroup_rwsem on return. If
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* CLONE_INTO_CGROUP is requested this function will grab cgroup mutex
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* before grabbing cgroup_threadgroup_rwsem and will hold a reference
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* to the target cgroup.
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*/
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static int cgroup_css_set_fork(struct kernel_clone_args *kargs)
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__acquires(&cgroup_mutex) __acquires(&cgroup_threadgroup_rwsem)
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{
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int ret;
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struct cgroup *dst_cgrp = NULL;
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struct css_set *cset;
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struct super_block *sb;
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struct file *f;
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if (kargs->flags & CLONE_INTO_CGROUP)
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mutex_lock(&cgroup_mutex);
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cgroup_threadgroup_change_begin(current);
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spin_lock_irq(&css_set_lock);
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cset = task_css_set(current);
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get_css_set(cset);
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spin_unlock_irq(&css_set_lock);
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if (!(kargs->flags & CLONE_INTO_CGROUP)) {
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kargs->cset = cset;
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return 0;
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}
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f = fget_raw(kargs->cgroup);
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if (!f) {
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ret = -EBADF;
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goto err;
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}
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sb = f->f_path.dentry->d_sb;
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dst_cgrp = cgroup_get_from_file(f);
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if (IS_ERR(dst_cgrp)) {
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ret = PTR_ERR(dst_cgrp);
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dst_cgrp = NULL;
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goto err;
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}
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if (cgroup_is_dead(dst_cgrp)) {
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ret = -ENODEV;
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goto err;
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}
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/*
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* Verify that we the target cgroup is writable for us. This is
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* usually done by the vfs layer but since we're not going through
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* the vfs layer here we need to do it "manually".
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*/
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ret = cgroup_may_write(dst_cgrp, sb);
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if (ret)
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goto err;
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ret = cgroup_attach_permissions(cset->dfl_cgrp, dst_cgrp, sb,
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!(kargs->flags & CLONE_THREAD));
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if (ret)
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goto err;
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kargs->cset = find_css_set(cset, dst_cgrp);
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if (!kargs->cset) {
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ret = -ENOMEM;
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goto err;
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}
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put_css_set(cset);
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fput(f);
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kargs->cgrp = dst_cgrp;
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return ret;
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err:
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cgroup_threadgroup_change_end(current);
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mutex_unlock(&cgroup_mutex);
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if (f)
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fput(f);
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if (dst_cgrp)
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cgroup_put(dst_cgrp);
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put_css_set(cset);
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if (kargs->cset)
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put_css_set(kargs->cset);
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return ret;
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}
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/**
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* cgroup_css_set_put_fork - drop references we took during fork
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* @kargs: the arguments passed to create the child process
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*
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* Drop references to the prepared css_set and target cgroup if
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* CLONE_INTO_CGROUP was requested.
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*/
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static void cgroup_css_set_put_fork(struct kernel_clone_args *kargs)
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__releases(&cgroup_threadgroup_rwsem) __releases(&cgroup_mutex)
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{
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cgroup_threadgroup_change_end(current);
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if (kargs->flags & CLONE_INTO_CGROUP) {
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struct cgroup *cgrp = kargs->cgrp;
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struct css_set *cset = kargs->cset;
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mutex_unlock(&cgroup_mutex);
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if (cset) {
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put_css_set(cset);
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kargs->cset = NULL;
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}
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if (cgrp) {
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cgroup_put(cgrp);
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kargs->cgrp = NULL;
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}
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}
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}
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/**
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* cgroup_can_fork - called on a new task before the process is exposed
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* @child: the child process
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*
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* This prepares a new css_set for the child process which the child will
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* be attached to in cgroup_post_fork().
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* This calls the subsystem can_fork() callbacks. If the cgroup_can_fork()
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* callback returns an error, the fork aborts with that error code. This
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* allows for a cgroup subsystem to conditionally allow or deny new forks.
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*/
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int cgroup_can_fork(struct task_struct *child)
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__acquires(&cgroup_threadgroup_rwsem) __releases(&cgroup_threadgroup_rwsem)
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int cgroup_can_fork(struct task_struct *child, struct kernel_clone_args *kargs)
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{
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struct cgroup_subsys *ss;
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int i, j, ret;
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cgroup_threadgroup_change_begin(current);
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ret = cgroup_css_set_fork(kargs);
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if (ret)
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return ret;
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do_each_subsys_mask(ss, i, have_canfork_callback) {
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ret = ss->can_fork(child);
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ret = ss->can_fork(child, kargs->cset);
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if (ret)
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goto out_revert;
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} while_each_subsys_mask();
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@ -5937,32 +6066,34 @@ out_revert:
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if (j >= i)
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break;
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if (ss->cancel_fork)
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ss->cancel_fork(child);
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ss->cancel_fork(child, kargs->cset);
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}
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cgroup_threadgroup_change_end(current);
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cgroup_css_set_put_fork(kargs);
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return ret;
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}
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/**
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* cgroup_cancel_fork - called if a fork failed after cgroup_can_fork()
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* @child: the child process
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*
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* This calls the cancel_fork() callbacks if a fork failed *after*
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* cgroup_can_fork() succeded.
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*/
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void cgroup_cancel_fork(struct task_struct *child)
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__releases(&cgroup_threadgroup_rwsem)
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* cgroup_cancel_fork - called if a fork failed after cgroup_can_fork()
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* @child: the child process
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* @kargs: the arguments passed to create the child process
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*
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* This calls the cancel_fork() callbacks if a fork failed *after*
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* cgroup_can_fork() succeded and cleans up references we took to
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* prepare a new css_set for the child process in cgroup_can_fork().
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*/
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void cgroup_cancel_fork(struct task_struct *child,
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struct kernel_clone_args *kargs)
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{
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struct cgroup_subsys *ss;
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int i;
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for_each_subsys(ss, i)
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if (ss->cancel_fork)
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ss->cancel_fork(child);
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ss->cancel_fork(child, kargs->cset);
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cgroup_threadgroup_change_end(current);
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cgroup_css_set_put_fork(kargs);
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}
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/**
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@ -5972,22 +6103,27 @@ void cgroup_cancel_fork(struct task_struct *child)
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* Attach the child process to its css_set calling the subsystem fork()
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* callbacks.
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*/
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void cgroup_post_fork(struct task_struct *child)
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__releases(&cgroup_threadgroup_rwsem)
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void cgroup_post_fork(struct task_struct *child,
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struct kernel_clone_args *kargs)
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__releases(&cgroup_threadgroup_rwsem) __releases(&cgroup_mutex)
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{
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struct cgroup_subsys *ss;
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struct css_set *cset;
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int i;
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cset = kargs->cset;
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kargs->cset = NULL;
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spin_lock_irq(&css_set_lock);
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/* init tasks are special, only link regular threads */
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if (likely(child->pid)) {
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WARN_ON_ONCE(!list_empty(&child->cg_list));
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cset = task_css_set(current); /* current is @child's parent */
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get_css_set(cset);
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cset->nr_tasks++;
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css_set_move_task(child, NULL, cset, false);
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} else {
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put_css_set(cset);
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cset = NULL;
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}
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/*
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@ -6020,7 +6156,16 @@ void cgroup_post_fork(struct task_struct *child)
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ss->fork(child);
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} while_each_subsys_mask();
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cgroup_threadgroup_change_end(current);
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/* Make the new cset the root_cset of the new cgroup namespace. */
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if (kargs->flags & CLONE_NEWCGROUP) {
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struct css_set *rcset = child->nsproxy->cgroup_ns->root_cset;
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get_css_set(cset);
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child->nsproxy->cgroup_ns->root_cset = cset;
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put_css_set(rcset);
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}
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cgroup_css_set_put_fork(kargs);
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}
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/**
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@ -33,6 +33,7 @@
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#include <linux/atomic.h>
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#include <linux/cgroup.h>
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#include <linux/slab.h>
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#include <linux/sched/task.h>
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#define PIDS_MAX (PID_MAX_LIMIT + 1ULL)
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#define PIDS_MAX_STR "max"
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@ -214,13 +215,16 @@ static void pids_cancel_attach(struct cgroup_taskset *tset)
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* task_css_check(true) in pids_can_fork() and pids_cancel_fork() relies
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* on cgroup_threadgroup_change_begin() held by the copy_process().
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*/
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static int pids_can_fork(struct task_struct *task)
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static int pids_can_fork(struct task_struct *task, struct css_set *cset)
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{
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struct cgroup_subsys_state *css;
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struct pids_cgroup *pids;
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int err;
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css = task_css_check(current, pids_cgrp_id, true);
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if (cset)
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css = cset->subsys[pids_cgrp_id];
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else
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css = task_css_check(current, pids_cgrp_id, true);
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pids = css_pids(css);
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err = pids_try_charge(pids, 1);
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if (err) {
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@ -235,12 +239,15 @@ static int pids_can_fork(struct task_struct *task)
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return err;
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}
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static void pids_cancel_fork(struct task_struct *task)
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static void pids_cancel_fork(struct task_struct *task, struct css_set *cset)
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{
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struct cgroup_subsys_state *css;
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struct pids_cgroup *pids;
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css = task_css_check(current, pids_cgrp_id, true);
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if (cset)
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css = cset->subsys[pids_cgrp_id];
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else
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css = task_css_check(current, pids_cgrp_id, true);
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pids = css_pids(css);
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pids_uncharge(pids, 1);
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}
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@ -2180,7 +2180,7 @@ static __latent_entropy struct task_struct *copy_process(
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* between here and cgroup_post_fork() if an organisation operation is in
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* progress.
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*/
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retval = cgroup_can_fork(p);
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retval = cgroup_can_fork(p, args);
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if (retval)
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goto bad_fork_put_pidfd;
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@ -2287,7 +2287,7 @@ static __latent_entropy struct task_struct *copy_process(
|
||||
write_unlock_irq(&tasklist_lock);
|
||||
|
||||
proc_fork_connector(p);
|
||||
cgroup_post_fork(p);
|
||||
cgroup_post_fork(p, args);
|
||||
perf_event_fork(p);
|
||||
|
||||
trace_task_newtask(p, clone_flags);
|
||||
@ -2298,7 +2298,7 @@ static __latent_entropy struct task_struct *copy_process(
|
||||
bad_fork_cancel_cgroup:
|
||||
spin_unlock(¤t->sighand->siglock);
|
||||
write_unlock_irq(&tasklist_lock);
|
||||
cgroup_cancel_fork(p);
|
||||
cgroup_cancel_fork(p, args);
|
||||
bad_fork_put_pidfd:
|
||||
if (clone_flags & CLONE_PIDFD) {
|
||||
fput(pidfile);
|
||||
@ -2627,6 +2627,9 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
|
||||
!valid_signal(args.exit_signal)))
|
||||
return -EINVAL;
|
||||
|
||||
if ((args.flags & CLONE_INTO_CGROUP) && args.cgroup < 0)
|
||||
return -EINVAL;
|
||||
|
||||
*kargs = (struct kernel_clone_args){
|
||||
.flags = args.flags,
|
||||
.pidfd = u64_to_user_ptr(args.pidfd),
|
||||
@ -2637,6 +2640,7 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
|
||||
.stack_size = args.stack_size,
|
||||
.tls = args.tls,
|
||||
.set_tid_size = args.set_tid_size,
|
||||
.cgroup = args.cgroup,
|
||||
};
|
||||
|
||||
if (args.set_tid &&
|
||||
@ -2680,7 +2684,8 @@ static inline bool clone3_stack_valid(struct kernel_clone_args *kargs)
|
||||
static bool clone3_args_valid(struct kernel_clone_args *kargs)
|
||||
{
|
||||
/* Verify that no unknown flags are passed along. */
|
||||
if (kargs->flags & ~(CLONE_LEGACY_FLAGS | CLONE_CLEAR_SIGHAND))
|
||||
if (kargs->flags &
|
||||
~(CLONE_LEGACY_FLAGS | CLONE_CLEAR_SIGHAND | CLONE_INTO_CGROUP))
|
||||
return false;
|
||||
|
||||
/*
|
||||
|
||||
Loading…
Reference in New Issue
Block a user