diff options
| author | Tejun Heo <tj@kernel.org> | 2013-08-08 20:11:24 -0400 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2013-08-08 20:11:24 -0400 |
| commit | 67f4c36f83455b253445b2cb28ac9a2c4f85d99a (patch) | |
| tree | 3c7aecc6fc830799cf36716ea64583cc10cb9d40 | |
| parent | f7d58818ba4249f04a83b73aaac135640050bb4f (diff) | |
cgroup: add cgroup->dummy_css
cgroup subsystem API is being converted to use css
(cgroup_subsys_state) as the main handle, which makes things a bit
awkward for subsystem agnostic core features - the "cgroup.*"
interface files and various iterations - a bit awkward as they don't
have a css to use.
This patch adds cgroup->dummy_css which has NULL ->ss and whose only
role is pointing back to the cgroup. This will be used to support
subsystem agnostic features on the coming css based API.
css_parent() is updated to handle dummy_css's. Note that css will
soon grow its own ->parent field and css_parent() will be made
trivial.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
| -rw-r--r-- | include/linux/cgroup.h | 11 | ||||
| -rw-r--r-- | kernel/cgroup.c | 9 |
2 files changed, 15 insertions, 5 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 5db8138a048..b0d5f53ae5e 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -225,6 +225,9 @@ struct cgroup { struct list_head pidlists; struct mutex pidlist_mutex; + /* dummy css with NULL ->ss, points back to this cgroup */ + struct cgroup_subsys_state dummy_css; + /* For css percpu_ref killing and RCU-protected deletion */ struct rcu_head rcu_head; struct work_struct destroy_work; @@ -668,7 +671,13 @@ struct cgroup_subsys_state *css_parent(struct cgroup_subsys_state *css) { struct cgroup *parent_cgrp = css->cgroup->parent; - return parent_cgrp ? parent_cgrp->subsys[css->ss->subsys_id] : NULL; + if (!parent_cgrp) + return NULL; + + if (css->ss) + return parent_cgrp->subsys[css->ss->subsys_id]; + else + return &parent_cgrp->dummy_css; } /** diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 583f8f66a7e..c049992f1ff 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1365,6 +1365,7 @@ static void init_cgroup_housekeeping(struct cgroup *cgrp) INIT_LIST_HEAD(&cgrp->release_list); INIT_LIST_HEAD(&cgrp->pidlists); mutex_init(&cgrp->pidlist_mutex); + cgrp->dummy_css.cgroup = cgrp; INIT_LIST_HEAD(&cgrp->event_list); spin_lock_init(&cgrp->event_list_lock); simple_xattrs_init(&cgrp->xattrs); @@ -2285,7 +2286,7 @@ static struct cgroup_subsys_state *cgroup_file_css(struct cfent *cfe) if (cft->ss) return cgrp->subsys[cft->ss->subsys_id]; - return NULL; + return &cgrp->dummy_css; } /* A buffer size big enough for numbers or short strings */ @@ -2467,7 +2468,7 @@ static int cgroup_file_open(struct inode *inode, struct file *file) * unpinned either on open failure or release. This ensures that * @css stays alive for all file operations. */ - if (css && !css_tryget(css)) + if (css->ss && !css_tryget(css)) return -ENODEV; if (cft->read_map || cft->read_seq_string) { @@ -2477,7 +2478,7 @@ static int cgroup_file_open(struct inode *inode, struct file *file) err = cft->open(inode, file); } - if (css && err) + if (css->ss && err) css_put(css); return err; } @@ -2491,7 +2492,7 @@ static int cgroup_file_release(struct inode *inode, struct file *file) if (cft->release) ret = cft->release(inode, file); - if (css) + if (css->ss) css_put(css); return ret; } |