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Message-ID: <47029555-aba6-4d85-ace3-0580ec606e5d@redhat.com>
Date: Wed, 17 Dec 2025 14:05:39 -0500
From: Waiman Long <llong@...hat.com>
To: Chen Ridong <chenridong@...weicloud.com>, tj@...nel.org,
hannes@...xchg.org, mkoutny@...e.com
Cc: cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
lujialin4@...wei.com
Subject: Re: [PATCH -next 6/6] cpuset: remove v1-specific code from
generate_sched_domains
On 12/17/25 3:49 AM, Chen Ridong wrote:
> From: Chen Ridong <chenridong@...wei.com>
>
> Following the introduction of cpuset1_generate_sched_domains() for v1
> in the previous patch, v1-specific logic can now be removed from the
> generic generate_sched_domains(). This patch cleans up the v1-only
> code and ensures uf_node is only visible when CONFIG_CPUSETS_V1=y.
>
> Signed-off-by: Chen Ridong <chenridong@...wei.com>
> ---
> kernel/cgroup/cpuset-internal.h | 10 +--
> kernel/cgroup/cpuset-v1.c | 2 +-
> kernel/cgroup/cpuset.c | 144 +++++---------------------------
> 3 files changed, 27 insertions(+), 129 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset-internal.h b/kernel/cgroup/cpuset-internal.h
> index bd767f8cb0ed..ef7b7c5afd4c 100644
> --- a/kernel/cgroup/cpuset-internal.h
> +++ b/kernel/cgroup/cpuset-internal.h
> @@ -175,14 +175,14 @@ struct cpuset {
> /* Handle for cpuset.cpus.partition */
> struct cgroup_file partition_file;
>
> - /* Used to merge intersecting subsets for generate_sched_domains */
> - struct uf_node node;
> -
> #ifdef CONFIG_CPUSETS_V1
> struct fmeter fmeter; /* memory_pressure filter */
>
> /* for custom sched domain */
> int relax_domain_level;
> +
> + /* Used to merge intersecting subsets for generate_sched_domains */
> + struct uf_node node;
> #endif
> };
>
> @@ -315,8 +315,6 @@ void cpuset1_hotplug_update_tasks(struct cpuset *cs,
> int cpuset1_validate_change(struct cpuset *cur, struct cpuset *trial);
> void cpuset1_init(struct cpuset *cs);
> void cpuset1_online_css(struct cgroup_subsys_state *css);
> -void update_domain_attr_tree(struct sched_domain_attr *dattr,
> - struct cpuset *root_cs);
> int cpuset1_generate_sched_domains(cpumask_var_t **domains,
> struct sched_domain_attr **attributes);
>
> @@ -331,8 +329,6 @@ static inline int cpuset1_validate_change(struct cpuset *cur,
> struct cpuset *trial) { return 0; }
> static inline void cpuset1_init(struct cpuset *cs) {}
> static inline void cpuset1_online_css(struct cgroup_subsys_state *css) {}
> -static inline void update_domain_attr_tree(struct sched_domain_attr *dattr,
> - struct cpuset *root_cs) {}
> static inline int cpuset1_generate_sched_domains(cpumask_var_t **domains,
> struct sched_domain_attr **attributes) { return 0; };
>
> diff --git a/kernel/cgroup/cpuset-v1.c b/kernel/cgroup/cpuset-v1.c
> index 5c0bded46a7c..0226350e704f 100644
> --- a/kernel/cgroup/cpuset-v1.c
> +++ b/kernel/cgroup/cpuset-v1.c
> @@ -560,7 +560,7 @@ update_domain_attr(struct sched_domain_attr *dattr, struct cpuset *c)
> dattr->relax_domain_level = c->relax_domain_level;
> }
>
> -void update_domain_attr_tree(struct sched_domain_attr *dattr,
> +static void update_domain_attr_tree(struct sched_domain_attr *dattr,
> struct cpuset *root_cs)
> {
> struct cpuset *cp;
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 6bb0b201c34b..3e3468d928f3 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -789,18 +789,13 @@ static int generate_sched_domains(cpumask_var_t **domains,
> {
> struct cpuset *cp; /* top-down scan of cpusets */
> struct cpuset **csa; /* array of all cpuset ptrs */
> - int csn; /* how many cpuset ptrs in csa so far */
> int i, j; /* indices for partition finding loops */
> cpumask_var_t *doms; /* resulting partition; i.e. sched domains */
> struct sched_domain_attr *dattr; /* attributes for custom domains */
> int ndoms = 0; /* number of sched domains in result */
> - int nslot; /* next empty doms[] struct cpumask slot */
> struct cgroup_subsys_state *pos_css;
> - bool root_load_balance = is_sched_load_balance(&top_cpuset);
> - bool cgrpv2 = cpuset_v2();
> - int nslot_update;
>
> - if (!cgrpv2)
> + if (!cpuset_v2())
> return cpuset1_generate_sched_domains(domains, attributes);
>
> doms = NULL;
> @@ -808,70 +803,25 @@ static int generate_sched_domains(cpumask_var_t **domains,
> csa = NULL;
>
> /* Special case for the 99% of systems with one, full, sched domain */
> - if (root_load_balance && cpumask_empty(subpartitions_cpus)) {
> -single_root_domain:
> + if (cpumask_empty(subpartitions_cpus)) {
> ndoms = 1;
> - doms = alloc_sched_domains(ndoms);
> - if (!doms)
> - goto done;
> -
> - dattr = kmalloc(sizeof(struct sched_domain_attr), GFP_KERNEL);
> - if (dattr) {
> - *dattr = SD_ATTR_INIT;
> - update_domain_attr_tree(dattr, &top_cpuset);
> - }
> - cpumask_and(doms[0], top_cpuset.effective_cpus,
> - housekeeping_cpumask(HK_TYPE_DOMAIN));
> -
> - goto done;
> + goto generate_doms;
That is not correct. The code under the generate_doms label will need to
access csa[0] which is not allocated yet and may cause panic. You either
need to keep the current code or move it after the csa allocation and
assign top_cpuset to csa[0].
> }
>
> csa = kmalloc_array(nr_cpusets(), sizeof(cp), GFP_KERNEL);
> if (!csa)
> goto done;
> - csn = 0;
>
> + /* Find how many partitions and cache them to csa[] */
> rcu_read_lock();
> - if (root_load_balance)
> - csa[csn++] = &top_cpuset;
> cpuset_for_each_descendant_pre(cp, pos_css, &top_cpuset) {
The cpuset_for_each_descendant_pre() macro will visit the root
(top_cpuset) first and so it should be OK to remove the above 2 lines of
code.
Cheers,
Longman
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