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Message-Id: <20251216012845.2437419-1-chenridong@huaweicloud.com>
Date: Tue, 16 Dec 2025 01:28:45 +0000
From: Chen Ridong <chenridong@...weicloud.com>
To: longman@...hat.com,
tj@...nel.org,
hannes@...xchg.org,
mkoutny@...e.com
Cc: cgroups@...r.kernel.org,
linux-kernel@...r.kernel.org,
lujialin4@...wei.com,
chenridong@...weicloud.com
Subject: [PATCH -next] cpuset: add cpuset1_online_css helper for v1-specific operations
From: Chen Ridong <chenridong@...wei.com>
This commit introduces the cpuset1_online_css helper to centralize
v1-specific handling during cpuset online. It performs operations such as
updating the CS_SPREAD_PAGE, CS_SPREAD_SLAB, and CGRP_CPUSET_CLONE_CHILDREN
flags, which are unique to the cpuset v1 control group interface.
The helper is now placed in cpuset-v1.c to maintain clear separation
between v1 and v2 logic.
Signed-off-by: Chen Ridong <chenridong@...wei.com>
---
kernel/cgroup/cpuset-internal.h | 2 ++
kernel/cgroup/cpuset-v1.c | 46 +++++++++++++++++++++++++++++++++
kernel/cgroup/cpuset.c | 39 +---------------------------
3 files changed, 49 insertions(+), 38 deletions(-)
diff --git a/kernel/cgroup/cpuset-internal.h b/kernel/cgroup/cpuset-internal.h
index 01976c8e7d49..d3bde90ac6f3 100644
--- a/kernel/cgroup/cpuset-internal.h
+++ b/kernel/cgroup/cpuset-internal.h
@@ -293,6 +293,7 @@ void cpuset1_hotplug_update_tasks(struct cpuset *cs,
struct cpumask *new_cpus, nodemask_t *new_mems,
bool cpus_updated, bool mems_updated);
int cpuset1_validate_change(struct cpuset *cur, struct cpuset *trial);
+void cpuset1_online_css(struct cgroup_subsys_state *css);
#else
static inline void fmeter_init(struct fmeter *fmp) {}
static inline void cpuset1_update_task_spread_flags(struct cpuset *cs,
@@ -303,6 +304,7 @@ static inline void cpuset1_hotplug_update_tasks(struct cpuset *cs,
bool cpus_updated, bool mems_updated) {}
static inline int cpuset1_validate_change(struct cpuset *cur,
struct cpuset *trial) { return 0; }
+static inline void cpuset1_online_css(struct cgroup_subsys_state *css) {}
#endif /* CONFIG_CPUSETS_V1 */
#endif /* __CPUSET_INTERNAL_H */
diff --git a/kernel/cgroup/cpuset-v1.c b/kernel/cgroup/cpuset-v1.c
index 12e76774c75b..1d83c2b26ff0 100644
--- a/kernel/cgroup/cpuset-v1.c
+++ b/kernel/cgroup/cpuset-v1.c
@@ -499,6 +499,52 @@ static int cpuset_write_u64(struct cgroup_subsys_state *css, struct cftype *cft,
return retval;
}
+/* v1-specific operation — caller must hold cpuset_full_lock. */
+void cpuset1_online_css(struct cgroup_subsys_state *css)
+{
+ struct cpuset *tmp_cs;
+ struct cgroup_subsys_state *pos_css;
+ struct cpuset *cs = css_cs(css);
+ struct cpuset *parent = parent_cs(cs);
+
+ if (is_spread_page(parent))
+ set_bit(CS_SPREAD_PAGE, &cs->flags);
+ if (is_spread_slab(parent))
+ set_bit(CS_SPREAD_SLAB, &cs->flags);
+
+ if (!test_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags))
+ return;
+
+ /*
+ * Clone @parent's configuration if CGRP_CPUSET_CLONE_CHILDREN is
+ * set. This flag handling is implemented in cgroup core for
+ * historical reasons - the flag may be specified during mount.
+ *
+ * Currently, if any sibling cpusets have exclusive cpus or mem, we
+ * refuse to clone the configuration - thereby refusing the task to
+ * be entered, and as a result refusing the sys_unshare() or
+ * clone() which initiated it. If this becomes a problem for some
+ * users who wish to allow that scenario, then this could be
+ * changed to grant parent->cpus_allowed-sibling_cpus_exclusive
+ * (and likewise for mems) to the new cgroup.
+ */
+ rcu_read_lock();
+ cpuset_for_each_child(tmp_cs, pos_css, parent) {
+ if (is_mem_exclusive(tmp_cs) || is_cpu_exclusive(tmp_cs)) {
+ rcu_read_unlock();
+ return;
+ }
+ }
+ rcu_read_unlock();
+
+ cpuset_callback_lock_irq();
+ cs->mems_allowed = parent->mems_allowed;
+ cs->effective_mems = parent->mems_allowed;
+ cpumask_copy(cs->cpus_allowed, parent->cpus_allowed);
+ cpumask_copy(cs->effective_cpus, parent->cpus_allowed);
+ cpuset_callback_unlock_irq();
+}
+
/*
* for the common functions, 'private' gives the type of file
*/
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index fea577b4016a..ba645ba09a25 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -3611,17 +3611,11 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)
{
struct cpuset *cs = css_cs(css);
struct cpuset *parent = parent_cs(cs);
- struct cpuset *tmp_cs;
- struct cgroup_subsys_state *pos_css;
if (!parent)
return 0;
cpuset_full_lock();
- if (is_spread_page(parent))
- set_bit(CS_SPREAD_PAGE, &cs->flags);
- if (is_spread_slab(parent))
- set_bit(CS_SPREAD_SLAB, &cs->flags);
/*
* For v2, clear CS_SCHED_LOAD_BALANCE if parent is isolated
*/
@@ -3636,39 +3630,8 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)
cs->effective_mems = parent->effective_mems;
}
spin_unlock_irq(&callback_lock);
+ cpuset1_online_css(css);
- if (!test_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags))
- goto out_unlock;
-
- /*
- * Clone @parent's configuration if CGRP_CPUSET_CLONE_CHILDREN is
- * set. This flag handling is implemented in cgroup core for
- * historical reasons - the flag may be specified during mount.
- *
- * Currently, if any sibling cpusets have exclusive cpus or mem, we
- * refuse to clone the configuration - thereby refusing the task to
- * be entered, and as a result refusing the sys_unshare() or
- * clone() which initiated it. If this becomes a problem for some
- * users who wish to allow that scenario, then this could be
- * changed to grant parent->cpus_allowed-sibling_cpus_exclusive
- * (and likewise for mems) to the new cgroup.
- */
- rcu_read_lock();
- cpuset_for_each_child(tmp_cs, pos_css, parent) {
- if (is_mem_exclusive(tmp_cs) || is_cpu_exclusive(tmp_cs)) {
- rcu_read_unlock();
- goto out_unlock;
- }
- }
- rcu_read_unlock();
-
- spin_lock_irq(&callback_lock);
- cs->mems_allowed = parent->mems_allowed;
- cs->effective_mems = parent->mems_allowed;
- cpumask_copy(cs->cpus_allowed, parent->cpus_allowed);
- cpumask_copy(cs->effective_cpus, parent->cpus_allowed);
- spin_unlock_irq(&callback_lock);
-out_unlock:
cpuset_full_unlock();
return 0;
}
--
2.34.1
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