From 8c7f6edbda01f1b1a2e60ad61f14fe38023e433b Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Thu, 13 Sep 2012 12:20:58 -0700 Subject: [PATCH] cgroup: mark subsystems with broken hierarchy support and whine if cgroups are nested for them Currently, cgroup hierarchy support is a mess. cpu related subsystems behave correctly - configuration, accounting and control on a parent properly cover its children. blkio and freezer completely ignore hierarchy and treat all cgroups as if they're directly under the root cgroup. Others show yet different behaviors. These differing interpretations of cgroup hierarchy make using cgroup confusing and it impossible to co-mount controllers into the same hierarchy and obtain sane behavior. Eventually, we want full hierarchy support from all subsystems and probably a unified hierarchy. Users using separate hierarchies expecting completely different behaviors depending on the mounted subsystem is deterimental to making any progress on this front. This patch adds cgroup_subsys.broken_hierarchy and sets it to %true for controllers which are lacking in hierarchy support. The goal of this patch is two-fold. * Move users away from using hierarchy on currently non-hierarchical subsystems, so that implementing proper hierarchy support on those doesn't surprise them. * Keep track of which controllers are broken how and nudge the subsystems to implement proper hierarchy support. For now, start with a single warning message. We can whine louder later on. v2: Fixed a typo spotted by Michal. Warning message updated. v3: Updated memcg part so that it doesn't generate warning in the cases where .use_hierarchy=false doesn't make the behavior different from root.use_hierarchy=true. Fixed a typo spotted by Glauber. v4: Check ->broken_hierarchy after cgroup creation is complete so that ->create() can affect the result per Michal. Dropped unnecessary memcg root handling per Michal. Signed-off-by: Tejun Heo Acked-by: Michal Hocko Acked-by: Li Zefan Acked-by: Serge E. Hallyn Cc: Glauber Costa Cc: Peter Zijlstra Cc: Paul Turner Cc: Johannes Weiner Cc: Thomas Graf Cc: Vivek Goyal Cc: Paul Mackerras Cc: Ingo Molnar Cc: Arnaldo Carvalho de Melo Cc: Neil Horman Cc: Aneesh Kumar K.V --- block/blk-cgroup.c | 8 ++++++++ include/linux/cgroup.h | 15 +++++++++++++++ kernel/cgroup.c | 12 +++++++++++- kernel/cgroup_freezer.c | 8 ++++++++ kernel/events/core.c | 7 +++++++ mm/memcontrol.c | 7 +++++++ net/core/netprio_cgroup.c | 12 +++++++++++- net/sched/cls_cgroup.c | 9 +++++++++ security/device_cgroup.c | 9 +++++++++ 9 files changed, 85 insertions(+), 2 deletions(-) diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index f3b44a65fc7a..cafcd7431189 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -737,6 +737,14 @@ struct cgroup_subsys blkio_subsys = { .subsys_id = blkio_subsys_id, .base_cftypes = blkcg_files, .module = THIS_MODULE, + + /* + * blkio subsystem is utterly broken in terms of hierarchy support. + * It treats all cgroups equally regardless of where they're + * located in the hierarchy - all cgroups are treated as if they're + * right below the root. Fix it and remove the following. + */ + .broken_hierarchy = true, }; EXPORT_SYMBOL_GPL(blkio_subsys); diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index c90eaa803440..68e8df70487e 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -496,6 +496,21 @@ struct cgroup_subsys { */ bool __DEPRECATED_clear_css_refs; + /* + * If %false, this subsystem is properly hierarchical - + * configuration, resource accounting and restriction on a parent + * cgroup cover those of its children. If %true, hierarchy support + * is broken in some ways - some subsystems ignore hierarchy + * completely while others are only implemented half-way. + * + * It's now disallowed to create nested cgroups if the subsystem is + * broken and cgroup core will emit a warning message on such + * cases. Eventually, all subsystems will be made properly + * hierarchical and this will go away. + */ + bool broken_hierarchy; + bool warned_broken_hierarchy; + #define MAX_CGROUP_TYPE_NAMELEN 32 const char *name; diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 79818507e444..b7d9606b17d7 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -3954,8 +3954,9 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry, set_bit(CGRP_CLONE_CHILDREN, &cgrp->flags); for_each_subsys(root, ss) { - struct cgroup_subsys_state *css = ss->create(cgrp); + struct cgroup_subsys_state *css; + css = ss->create(cgrp); if (IS_ERR(css)) { err = PTR_ERR(css); goto err_destroy; @@ -3969,6 +3970,15 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry, /* At error, ->destroy() callback has to free assigned ID. */ if (clone_children(parent) && ss->post_clone) ss->post_clone(cgrp); + + if (ss->broken_hierarchy && !ss->warned_broken_hierarchy && + parent->parent) { + pr_warning("cgroup: %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")) + pr_warning("cgroup: \"memory\" requires setting use_hierarchy to 1 on the root.\n"); + ss->warned_broken_hierarchy = true; + } } list_add(&cgrp->sibling, &cgrp->parent->children); diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c index 3649fc6b3eaa..b1724ce98981 100644 --- a/kernel/cgroup_freezer.c +++ b/kernel/cgroup_freezer.c @@ -373,4 +373,12 @@ struct cgroup_subsys freezer_subsys = { .can_attach = freezer_can_attach, .fork = freezer_fork, .base_cftypes = files, + + /* + * freezer subsys doesn't handle hierarchy at all. Frozen state + * should be inherited through the hierarchy - if a parent is + * frozen, all its children should be frozen. Fix it and remove + * the following. + */ + .broken_hierarchy = true, }; diff --git a/kernel/events/core.c b/kernel/events/core.c index b7935fcec7d9..f18a0a56e5aa 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -7285,5 +7285,12 @@ struct cgroup_subsys perf_subsys = { .destroy = perf_cgroup_destroy, .exit = perf_cgroup_exit, .attach = perf_cgroup_attach, + + /* + * perf_event cgroup doesn't handle nesting correctly. + * ctx->nr_cgroups adjustments should be propagated through the + * cgroup hierarchy. Fix it and remove the following. + */ + .broken_hierarchy = true, }; #endif /* CONFIG_CGROUP_PERF */ diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 795e525afaba..a72f2ffdc3d0 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -4973,6 +4973,13 @@ mem_cgroup_create(struct cgroup *cont) } else { res_counter_init(&memcg->res, NULL); res_counter_init(&memcg->memsw, NULL); + /* + * Deeper hierachy with use_hierarchy == false doesn't make + * much sense so let cgroup subsystem know about this + * unfortunate state in our controller. + */ + if (parent && parent != root_mem_cgroup) + mem_cgroup_subsys.broken_hierarchy = true; } memcg->last_scanned_node = MAX_NUMNODES; INIT_LIST_HEAD(&memcg->oom_notify); diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c index c75e3f9d060f..34f3615b30ca 100644 --- a/net/core/netprio_cgroup.c +++ b/net/core/netprio_cgroup.c @@ -330,7 +330,17 @@ struct cgroup_subsys net_prio_subsys = { .subsys_id = net_prio_subsys_id, #endif .base_cftypes = ss_files, - .module = THIS_MODULE + .module = THIS_MODULE, + + /* + * net_prio has artificial limit on the number of cgroups and + * disallows nesting making it impossible to co-mount it with other + * hierarchical subsystems. Remove the artificially low PRIOIDX_SZ + * limit and properly nest configuration such that children follow + * their parents' configurations by default and are allowed to + * override and remove the following. + */ + .broken_hierarchy = true, }; static int netprio_device_event(struct notifier_block *unused, diff --git a/net/sched/cls_cgroup.c b/net/sched/cls_cgroup.c index 7743ea8d1d38..907daf99ab2e 100644 --- a/net/sched/cls_cgroup.c +++ b/net/sched/cls_cgroup.c @@ -82,6 +82,15 @@ struct cgroup_subsys net_cls_subsys = { #endif .base_cftypes = ss_files, .module = THIS_MODULE, + + /* + * While net_cls cgroup has the rudimentary hierarchy support of + * inheriting the parent's classid on cgroup creation, it doesn't + * properly propagates config changes in ancestors to their + * descendents. A child should follow the parent's configuration + * but be allowed to override it. Fix it and remove the following. + */ + .broken_hierarchy = true, }; struct cls_cgroup_head { diff --git a/security/device_cgroup.c b/security/device_cgroup.c index 442204cc22d9..4b877a92a7ea 100644 --- a/security/device_cgroup.c +++ b/security/device_cgroup.c @@ -457,6 +457,15 @@ struct cgroup_subsys devices_subsys = { .destroy = devcgroup_destroy, .subsys_id = devices_subsys_id, .base_cftypes = dev_cgroup_files, + + /* + * While devices cgroup has the rudimentary hierarchy support which + * checks the parent's restriction, it doesn't properly propagates + * config changes in ancestors to their descendents. A child + * should only be allowed to add more restrictions to the parent's + * configuration. Fix it and remove the following. + */ + .broken_hierarchy = true, }; int __devcgroup_inode_permission(struct inode *inode, int mask) -- 2.39.5