From c5866c9a007deb92717fc0b94ac47b47291748be Mon Sep 17 00:00:00 2001 From: Chen Ridong Date: Wed, 17 Sep 2025 06:04:48 +0000 Subject: [PATCH] cpuset: refactor CPU mask buffer parsing logic The current implementation contains redundant handling for empty mask inputs, as cpulist_parse() already properly handles these cases. This refactoring introduces a new helper function parse_cpuset_cpulist() to consolidate CPU list parsing logic and eliminate special-case checks for empty inputs. Additionally, the effective_xcpus computation for trial cpusets has been simplified. Rather than computing effective_xcpus only when exclusive_cpus is set or when the cpuset forms a valid partition, we now recalculate it on every cpuset.cpus update. This approach ensures consistency and allows removal of redundant effective_xcpus logic in subsequent patches. The trial cpuset's effective_xcpus calculation follows two distinct cases: 1. For member cpusets: effective_xcpus is determined by the intersection of cpuset->exclusive_cpus and the parent's effective_xcpus. 2. For non-member cpusets: effective_xcpus is derived from the intersection of user_xcpus and the parent's effective_xcpus. Signed-off-by: Chen Ridong Reviewed-by: Waiman Long Signed-off-by: Tejun Heo --- kernel/cgroup/cpuset.c | 59 +++++++++++++++++++++--------------------- 1 file changed, 30 insertions(+), 29 deletions(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 2b87a4b09fc95..45784c62d1c69 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -170,6 +170,11 @@ static inline bool is_partition_invalid(const struct cpuset *cs) return cs->partition_root_state < 0; } +static inline bool cs_is_member(const struct cpuset *cs) +{ + return cs->partition_root_state == PRS_MEMBER; +} + /* * Callers should hold callback_lock to modify partition_root_state. */ @@ -1479,7 +1484,13 @@ static int compute_trialcs_excpus(struct cpuset *trialcs, struct cpuset *cs) struct cpuset *parent = parent_cs(trialcs); struct cpumask *excpus = trialcs->effective_xcpus; - cpumask_and(excpus, user_xcpus(trialcs), parent->effective_xcpus); + /* trialcs is member, cpuset.cpus has no impact to excpus */ + if (cs_is_member(cs)) + cpumask_and(excpus, trialcs->exclusive_cpus, + parent->effective_xcpus); + else + cpumask_and(excpus, user_xcpus(trialcs), parent->effective_xcpus); + return rm_siblings_excl_cpus(parent, cs, excpus); } @@ -2349,6 +2360,19 @@ static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs, rcu_read_unlock(); } +static int parse_cpuset_cpulist(const char *buf, struct cpumask *out_mask) +{ + int retval; + + retval = cpulist_parse(buf, out_mask); + if (retval < 0) + return retval; + if (!cpumask_subset(out_mask, top_cpuset.cpus_allowed)) + return -EINVAL; + + return 0; +} + /** * update_cpumask - update the cpus_allowed mask of a cpuset and all tasks in it * @cs: the cpuset to consider @@ -2365,34 +2389,9 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs, bool force = false; int old_prs = cs->partition_root_state; - /* - * An empty cpus_allowed is ok only if the cpuset has no tasks. - * Since cpulist_parse() fails on an empty mask, we special case - * that parsing. The validate_change() call ensures that cpusets - * with tasks have cpus. - */ - if (!*buf) { - cpumask_clear(trialcs->cpus_allowed); - if (cpumask_empty(trialcs->exclusive_cpus)) - cpumask_clear(trialcs->effective_xcpus); - } else { - retval = cpulist_parse(buf, trialcs->cpus_allowed); - if (retval < 0) - return retval; - - if (!cpumask_subset(trialcs->cpus_allowed, - top_cpuset.cpus_allowed)) - return -EINVAL; - - /* - * When exclusive_cpus isn't explicitly set, it is constrained - * by cpus_allowed and parent's effective_xcpus. Otherwise, - * trialcs->effective_xcpus is used as a temporary cpumask - * for checking validity of the partition root. - */ - if (!cpumask_empty(trialcs->exclusive_cpus) || is_partition_valid(cs)) - compute_trialcs_excpus(trialcs, cs); - } + retval = parse_cpuset_cpulist(buf, trialcs->cpus_allowed); + if (retval < 0) + return retval; /* Nothing to do if the cpus didn't change */ if (cpumask_equal(cs->cpus_allowed, trialcs->cpus_allowed)) @@ -2401,6 +2400,8 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs, if (alloc_tmpmasks(&tmp)) return -ENOMEM; + compute_trialcs_excpus(trialcs, cs); + if (old_prs) { if (is_partition_valid(cs) && cpumask_empty(trialcs->effective_xcpus)) { -- 2.47.3