css_id should be committed after a css is brought online fully. This is currently done form cgroup_populate_dir() but we're gonna reorder operations such that cgroup_populate_dir() is called before css is onlined. Let's move css_id commit from cgroup_populate_dir() to online_css().
This change makes it possible for cgroup creation to fail after css_id is committed; however, as css is already fully initialized, the cleanup isn't different from the cgroup being removed. Signed-off-by: Tejun Heo <[email protected]> --- kernel/cgroup.c | 53 +++++++++++++++++++++++++---------------------------- 1 file changed, 25 insertions(+), 28 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index a65be0c..6a3ad20 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -4244,7 +4244,7 @@ static struct cftype cgroup_base_files[] = { static int cgroup_populate_dir(struct cgroup *cgrp, unsigned long subsys_mask) { struct cgroup_subsys *ss; - int i, ret = 0; + int i, ret; /* process cftsets of each subsystem */ for_each_subsys(ss, i) { @@ -4255,29 +4255,14 @@ static int cgroup_populate_dir(struct cgroup *cgrp, unsigned long subsys_mask) list_for_each_entry(set, &ss->cftsets, node) { ret = cgroup_addrm_files(cgrp, set->cfts, true); - if (ret < 0) - goto err; + if (ret < 0) { + cgroup_clear_dir(cgrp, subsys_mask); + return ret; + } } } - /* This cgroup is ready now */ - for_each_root_subsys(cgrp->root, ss) { - struct cgroup_subsys_state *css = cgroup_css(cgrp, ss); - struct css_id *id = rcu_dereference_protected(css->id, true); - - /* - * Update id->css pointer and make this css visible from - * CSS ID functions. This pointer will be dereferened - * from RCU-read-side without locks. - */ - if (id) - rcu_assign_pointer(id->css, css); - } - return 0; -err: - cgroup_clear_dir(cgrp, subsys_mask); - return ret; } /* @@ -4356,18 +4341,30 @@ static void init_css(struct cgroup_subsys_state *css, struct cgroup_subsys *ss, static int online_css(struct cgroup_subsys_state *css) { struct cgroup_subsys *ss = css->ss; - int ret = 0; + struct css_id *id = rcu_dereference_protected(css->id, true); + int ret; lockdep_assert_held(&cgroup_mutex); - if (ss->css_online) + if (ss->css_online) { ret = ss->css_online(css); - if (!ret) { - css->flags |= CSS_ONLINE; - css->cgroup->nr_css++; - rcu_assign_pointer(css->cgroup->subsys[ss->subsys_id], css); + if (ret) + return ret; } - return ret; + + css->flags |= CSS_ONLINE; + css->cgroup->nr_css++; + rcu_assign_pointer(css->cgroup->subsys[ss->subsys_id], css); + + /* + * Update id->css pointer and make this css visible from CSS ID + * functions. This pointer will be dereferened from RCU-read-side + * without locks. + */ + if (id) + rcu_assign_pointer(id->css, css); + + return 0; } /* if the CSS is online, invoke ->css_offline() on it and mark it offline */ @@ -5678,7 +5675,7 @@ static int alloc_css_id(struct cgroup_subsys_state *child_css) child_id->stack[depth] = child_id->id; /* * child_id->css pointer will be set after this cgroup is available - * see cgroup_populate_dir() + * see online_css() */ rcu_assign_pointer(child_css->id, child_id); -- 1.8.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
