diff options
| author | Michal Koutný <mkoutny@suse.com> | 2025-03-11 13:36:21 +0100 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2025-03-11 09:22:54 -1000 |
| commit | a0ab1453226d862cf30fdccc5a8e753f79c5bc99 (patch) | |
| tree | 2544a736dc28fd50299db71867828af70f00ff60 | |
| parent | 77bbb259db53ab5f0c971cf0180c28c897a06b9f (diff) | |
cgroup: Print message when /proc/cgroups is read on v2-only system
As a followup to commits 6c2920926b10e ("cgroup: replace
unified-hierarchy.txt with a proper cgroup v2 documentation") and
ab03125268679 ("cgroup: Show # of subsystem CSSes in cgroup.stat"),
add a runtime message to users who read status of controllers in
/proc/cgroups on v2-only system. The detection is based on a)
no controllers are attached to v1, b) default hierarchy is mounted (the
latter is for setups that never mount v2 but read /proc/cgroups upon
boot when controllers default to v2, so that this code may be backported
to older kernels).
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Acked-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
| -rw-r--r-- | kernel/cgroup/cgroup-internal.h | 1 | ||||
| -rw-r--r-- | kernel/cgroup/cgroup-v1.c | 7 | ||||
| -rw-r--r-- | kernel/cgroup/cgroup.c | 2 |
3 files changed, 9 insertions, 1 deletions
diff --git a/kernel/cgroup/cgroup-internal.h b/kernel/cgroup/cgroup-internal.h index c964dd7ff967..95ab39e1ec8f 100644 --- a/kernel/cgroup/cgroup-internal.h +++ b/kernel/cgroup/cgroup-internal.h @@ -168,6 +168,7 @@ struct cgroup_mgctx { extern struct cgroup_subsys *cgroup_subsys[]; extern struct list_head cgroup_roots; +extern bool cgrp_dfl_visible; /* iterate across the hierarchies */ #define for_each_root(root) \ diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c index e28d5f0d20ed..11ea8d24ac72 100644 --- a/kernel/cgroup/cgroup-v1.c +++ b/kernel/cgroup/cgroup-v1.c @@ -673,6 +673,7 @@ struct cftype cgroup1_base_files[] = { int proc_cgroupstats_show(struct seq_file *m, void *v) { struct cgroup_subsys *ss; + bool cgrp_v1_visible = false; int i; seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n"); @@ -684,12 +685,18 @@ int proc_cgroupstats_show(struct seq_file *m, void *v) for_each_subsys(ss, i) { if (cgroup1_subsys_absent(ss)) continue; + cgrp_v1_visible |= ss->root != &cgrp_dfl_root; + seq_printf(m, "%s\t%d\t%d\t%d\n", ss->legacy_name, ss->root->hierarchy_id, atomic_read(&ss->root->nr_cgrps), cgroup_ssid_enabled(i)); } + if (cgrp_dfl_visible && !cgrp_v1_visible) + pr_info_once("/proc/cgroups lists only v1 controllers, use cgroup.controllers of root cgroup for v2 info\n"); + + return 0; } diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 805764cf14e2..a810952d75c8 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -171,7 +171,7 @@ EXPORT_SYMBOL_GPL(cgrp_dfl_root); * The default hierarchy always exists but is hidden until mounted for the * first time. This is for backward compatibility. */ -static bool cgrp_dfl_visible; +bool cgrp_dfl_visible; /* some controllers are not supported in the default hierarchy */ static u16 cgrp_dfl_inhibit_ss_mask; |