diff options
| -rw-r--r-- | include/linux/cgroup.h | 4 | ||||
| -rw-r--r-- | kernel/cgroup.c | 25 | ||||
| -rw-r--r-- | kernel/events/core.c | 17 | ||||
| -rw-r--r-- | mm/memcontrol.c | 16 |
4 files changed, 26 insertions, 36 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index c86ba7ff7a7e..1ba4fc08f776 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -825,8 +825,8 @@ int css_scan_tasks(struct cgroup_subsys_state *css, int cgroup_attach_task_all(struct task_struct *from, struct task_struct *); int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from); -struct cgroup_subsys_state *css_from_dir(struct dentry *dentry, - struct cgroup_subsys *ss); +struct cgroup_subsys_state *css_tryget_from_dir(struct dentry *dentry, + struct cgroup_subsys *ss); #else /* !CONFIG_CGROUPS */ diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 2de8decfd99f..fc2db071d95e 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -4978,28 +4978,35 @@ static int __init cgroup_disable(char *str) __setup("cgroup_disable=", cgroup_disable); /** - * css_from_dir - get corresponding css from the dentry of a cgroup dir + * css_tryget_from_dir - get corresponding css from the dentry of a cgroup dir * @dentry: directory dentry of interest * @ss: subsystem of interest * - * Must be called under cgroup_mutex or RCU read lock. The caller is - * responsible for pinning the returned css if it needs to be accessed - * outside the critical section. + * If @dentry is a directory for a cgroup which has @ss enabled on it, try + * to get the corresponding css and return it. If such css doesn't exist + * or can't be pinned, an ERR_PTR value is returned. */ -struct cgroup_subsys_state *css_from_dir(struct dentry *dentry, - struct cgroup_subsys *ss) +struct cgroup_subsys_state *css_tryget_from_dir(struct dentry *dentry, + struct cgroup_subsys *ss) { struct cgroup *cgrp; - - cgroup_assert_mutex_or_rcu_locked(); + struct cgroup_subsys_state *css; /* is @dentry a cgroup dir? */ if (!dentry->d_inode || dentry->d_inode->i_op != &cgroup_dir_inode_operations) return ERR_PTR(-EBADF); + rcu_read_lock(); + cgrp = __d_cgrp(dentry); - return cgroup_css(cgrp, ss) ?: ERR_PTR(-ENOENT); + css = cgroup_css(cgrp, ss); + + if (!css || !css_tryget(css)) + css = ERR_PTR(-ENOENT); + + rcu_read_unlock(); + return css; } /** diff --git a/kernel/events/core.c b/kernel/events/core.c index 64903731d834..a3c3ab50271a 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -370,11 +370,6 @@ perf_cgroup_match(struct perf_event *event) event->cgrp->css.cgroup); } -static inline bool perf_tryget_cgroup(struct perf_event *event) -{ - return css_tryget(&event->cgrp->css); -} - static inline void perf_put_cgroup(struct perf_event *event) { css_put(&event->cgrp->css); @@ -593,9 +588,7 @@ static inline int perf_cgroup_connect(int fd, struct perf_event *event, if (!f.file) return -EBADF; - rcu_read_lock(); - - css = css_from_dir(f.file->f_dentry, &perf_event_cgrp_subsys); + css = css_tryget_from_dir(f.file->f_dentry, &perf_event_cgrp_subsys); if (IS_ERR(css)) { ret = PTR_ERR(css); goto out; @@ -604,13 +597,6 @@ static inline int perf_cgroup_connect(int fd, struct perf_event *event, cgrp = container_of(css, struct perf_cgroup, css); event->cgrp = cgrp; - /* must be done before we fput() the file */ - if (!perf_tryget_cgroup(event)) { - event->cgrp = NULL; - ret = -ENOENT; - goto out; - } - /* * all events in a group must monitor * the same cgroup because a task belongs @@ -621,7 +607,6 @@ static inline int perf_cgroup_connect(int fd, struct perf_event *event, ret = -EINVAL; } out: - rcu_read_unlock(); fdput(f); return ret; } diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 04a97bce2270..102ab48ffa13 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -6183,17 +6183,15 @@ static int memcg_write_event_control(struct cgroup_subsys_state *css, * automatically removed on cgroup destruction but the removal is * asynchronous, so take an extra ref on @css. */ - rcu_read_lock(); - + cfile_css = css_tryget_from_dir(cfile.file->f_dentry->d_parent, + &memory_cgrp_subsys); ret = -EINVAL; - cfile_css = css_from_dir(cfile.file->f_dentry->d_parent, - &memory_cgrp_subsys); - if (cfile_css == css && css_tryget(css)) - ret = 0; - - rcu_read_unlock(); - if (ret) + if (IS_ERR(cfile_css)) goto out_put_cfile; + if (cfile_css != css) { + css_put(cfile_css); + goto out_put_cfile; + } ret = event->register_event(memcg, event->eventfd, buffer); if (ret) |