From d51f39b05ce0008118c45945e681b20484990571 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Fri, 16 May 2014 13:22:48 -0400 Subject: [PATCH] cgroup: remove cgroup->parent cgroup->parent is redundant as cgroup->self.parent can also be used to determine the parent cgroup and we're moving towards using cgroup_subsys_states as the fundamental structural blocks. This patch introduces cgroup_parent() which follows cgroup->self.parent and removes cgroup->parent. Signed-off-by: Tejun Heo Acked-by: Li Zefan --- include/linux/cgroup.h | 1 - kernel/cgroup.c | 52 ++++++++++++++++++++++++------------------ 2 files changed, 30 insertions(+), 23 deletions(-) diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 2549493d518d..fd538f4c2bb6 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -178,7 +178,6 @@ struct cgroup { struct list_head sibling; /* my parent's children */ struct list_head children; /* my children */ - struct cgroup *parent; /* my parent */ struct kernfs_node *kn; /* cgroup kernfs entry */ struct kernfs_node *populated_kn; /* kn for "cgroup.subtree_populated" */ diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 929bbbc539e9..8c67a739aea4 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -218,6 +218,15 @@ static void cgroup_idr_remove(struct idr *idr, int id) spin_unlock_bh(&cgroup_idr_lock); } +static struct cgroup *cgroup_parent(struct cgroup *cgrp) +{ + struct cgroup_subsys_state *parent_css = cgrp->self.parent; + + if (parent_css) + return container_of(parent_css, struct cgroup, self); + return NULL; +} + /** * cgroup_css - obtain a cgroup's css for the specified subsystem * @cgrp: the cgroup of interest @@ -260,9 +269,9 @@ static struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp, if (!(cgrp->root->subsys_mask & (1 << ss->id))) return NULL; - while (cgrp->parent && - !(cgrp->parent->child_subsys_mask & (1 << ss->id))) - cgrp = cgrp->parent; + while (cgroup_parent(cgrp) && + !(cgroup_parent(cgrp)->child_subsys_mask & (1 << ss->id))) + cgrp = cgroup_parent(cgrp); return cgroup_css(cgrp, ss); } @@ -307,7 +316,7 @@ bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor) while (cgrp) { if (cgrp == ancestor) return true; - cgrp = cgrp->parent; + cgrp = cgroup_parent(cgrp); } return false; } @@ -454,7 +463,7 @@ static void cgroup_update_populated(struct cgroup *cgrp, bool populated) if (cgrp->populated_kn) kernfs_notify(cgrp->populated_kn); - cgrp = cgrp->parent; + cgrp = cgroup_parent(cgrp); } while (cgrp); } @@ -2018,7 +2027,7 @@ static int cgroup_migrate_prepare_dst(struct cgroup *dst_cgrp, * Except for the root, child_subsys_mask must be zero for a cgroup * with tasks so that child cgroups don't compete against tasks. */ - if (dst_cgrp && cgroup_on_dfl(dst_cgrp) && dst_cgrp->parent && + if (dst_cgrp && cgroup_on_dfl(dst_cgrp) && cgroup_parent(dst_cgrp) && dst_cgrp->child_subsys_mask) return -EBUSY; @@ -2427,7 +2436,7 @@ static int cgroup_controllers_show(struct seq_file *seq, void *v) { struct cgroup *cgrp = seq_css(seq)->cgroup; - cgroup_print_ss_mask(seq, cgrp->parent->child_subsys_mask); + cgroup_print_ss_mask(seq, cgroup_parent(cgrp)->child_subsys_mask); return 0; } @@ -2610,8 +2619,8 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of, /* unavailable or not enabled on the parent? */ if (!(cgrp_dfl_root.subsys_mask & (1 << ssid)) || - (cgrp->parent && - !(cgrp->parent->child_subsys_mask & (1 << ssid)))) { + (cgroup_parent(cgrp) && + !(cgroup_parent(cgrp)->child_subsys_mask & (1 << ssid)))) { ret = -ENOENT; goto out_unlock; } @@ -2640,7 +2649,7 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of, * Except for the root, child_subsys_mask must be zero for a cgroup * with tasks so that child cgroups don't compete against tasks. */ - if (enable && cgrp->parent && !list_empty(&cgrp->cset_links)) { + if (enable && cgroup_parent(cgrp) && !list_empty(&cgrp->cset_links)) { ret = -EBUSY; goto out_unlock; } @@ -2898,9 +2907,9 @@ static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[], continue; if ((cft->flags & CFTYPE_INSANE) && cgroup_sane_behavior(cgrp)) continue; - if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent) + if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgroup_parent(cgrp)) continue; - if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgrp->parent) + if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgroup_parent(cgrp)) continue; if (is_add) { @@ -4092,14 +4101,14 @@ static void css_free_work_fn(struct work_struct *work) atomic_dec(&cgrp->root->nr_cgrps); cgroup_pidlist_destroy_all(cgrp); - if (cgrp->parent) { + if (cgroup_parent(cgrp)) { /* * We get a ref to the parent, and put the ref when * this cgroup is being freed, so it's guaranteed * that the parent won't be destroyed before its * children. */ - cgroup_put(cgrp->parent); + cgroup_put(cgroup_parent(cgrp)); kernfs_put(cgrp->kn); kfree(cgrp); } else { @@ -4163,8 +4172,8 @@ static void init_and_link_css(struct cgroup_subsys_state *css, css->ss = ss; css->flags = 0; - if (cgrp->parent) { - css->parent = cgroup_css(cgrp->parent, ss); + if (cgroup_parent(cgrp)) { + css->parent = cgroup_css(cgroup_parent(cgrp), ss); css_get(css->parent); } @@ -4218,7 +4227,7 @@ static void offline_css(struct cgroup_subsys_state *css) */ static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss) { - struct cgroup *parent = cgrp->parent; + struct cgroup *parent = cgroup_parent(cgrp); struct cgroup_subsys_state *css; int err; @@ -4251,7 +4260,7 @@ static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss) goto err_clear_dir; if (ss->broken_hierarchy && !ss->warned_broken_hierarchy && - parent->parent) { + cgroup_parent(parent)) { pr_warn("%s (%d) created nested cgroup for controller \"%s\" which has incomplete hierarchy support. Nested cgroups may change behavior in the future.\n", current->comm, current->pid, ss->name); if (!strcmp(ss->name, "memory")) @@ -4309,7 +4318,6 @@ static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, init_cgroup_housekeeping(cgrp); - cgrp->parent = parent; cgrp->self.parent = &parent->self; cgrp->root = root; @@ -4336,7 +4344,7 @@ static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, cgrp->serial_nr = cgroup_serial_nr_next++; /* allocation complete, commit to creation */ - list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children); + list_add_tail_rcu(&cgrp->sibling, &cgroup_parent(cgrp)->children); atomic_inc(&root->nr_cgrps); cgroup_get(parent); @@ -4531,8 +4539,8 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) */ kernfs_remove(cgrp->kn); - set_bit(CGRP_RELEASABLE, &cgrp->parent->flags); - check_for_release(cgrp->parent); + set_bit(CGRP_RELEASABLE, &cgroup_parent(cgrp)->flags); + check_for_release(cgroup_parent(cgrp)); /* put the base reference */ percpu_ref_kill(&cgrp->self.refcnt);