sched/topology: Remove sched_domain_topology_level::flags

JIRA: https://issues.redhat.com/browse/RHEL-110301

commit 1eec89a
Author: K Prateek Nayak <kprateek.nayak@amd.com>
Date:   Fri Jul 11 11:20:30 2025 +0530

    sched/topology: Remove sched_domain_topology_level::flags

    Support for overlapping domains added in commit e3589f6 ("sched:
    Allow for overlapping sched_domain spans") also allowed forcefully
    setting SD_OVERLAP for !NUMA domains via FORCE_SD_OVERLAP sched_feat().

    Since NUMA domains had to be presumed overlapping to ensure correct
    behavior, "sched_domain_topology_level::flags" was introduced. NUMA
    domains added the SDTL_OVERLAP flag would ensure SD_OVERLAP was always
    added during build_sched_domains() for these domains, even when
    FORCE_SD_OVERLAP was off.

    Condition for adding the SD_OVERLAP flag at the aforementioned commit
    was as follows:

        if (tl->flags & SDTL_OVERLAP || sched_feat(FORCE_SD_OVERLAP))
                sd->flags |= SD_OVERLAP;

    The FORCE_SD_OVERLAP debug feature was removed in commit af85596
    ("sched/topology: Remove FORCE_SD_OVERLAP") which left the NUMA domains
    as the exclusive users of SDTL_OVERLAP, SD_OVERLAP, and SD_NUMA flags.

    Get rid of SDTL_OVERLAP and SD_OVERLAP as they have become redundant
    and instead rely on SD_NUMA to detect the only overlapping domain
    currently supported. Since SDTL_OVERLAP was the only user of
    "tl->flags", get rid of "sched_domain_topology_level::flags" too.

    Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Link: https://lkml.kernel.org/r/ba4dbdf8-bc37-493d-b2e0-2efb00ea3e19@amd.com

Signed-off-by: Phil Auld <pauld@redhat.com>

Author: auldp

include/linux/sched/sd_flags.h

@@ -153,14 +153,6 @@ SD_FLAG(SD_ASYM_PACKING, SDF_NEEDS_GROUPS)
  */
 SD_FLAG(SD_PREFER_SIBLING, SDF_NEEDS_GROUPS)
 
-/*
- * sched_groups of this level overlap
- *
- * SHARED_PARENT: Set for all NUMA levels above NODE.
- * NEEDS_GROUPS: Overlaps can only exist with more than one group.
- */
-SD_FLAG(SD_OVERLAP, SDF_SHARED_PARENT | SDF_NEEDS_GROUPS)
-
 /*
  * Cross-node balancing
  *

include/linux/sched/topology.h

@@ -175,8 +175,6 @@ bool cpus_share_resources(int this_cpu, int that_cpu);
 typedef const struct cpumask *(*sched_domain_mask_f)(int cpu);
 typedef int (*sched_domain_flags_f)(void);
 
-#define SDTL_OVERLAP	0x01
-
 struct sd_data {
 	struct sched_domain *__percpu *sd;
 	struct sched_domain_shared *__percpu *sds;
@@ -187,7 +185,6 @@ struct sd_data {
 struct sched_domain_topology_level {
 	sched_domain_mask_f mask;
 	sched_domain_flags_f sd_flags;
-	int		    flags;
 	int		    numa_level;
 	struct sd_data      data;
 	char                *name;

kernel/sched/fair.c

@@ -9926,9 +9926,9 @@ void update_group_capacity(struct sched_domain *sd, int cpu)
 	min_capacity = ULONG_MAX;
 	max_capacity = 0;
 
-	if (child->flags & SD_OVERLAP) {
+	if (child->flags & SD_NUMA) {
 		/*
-		 * SD_OVERLAP domains cannot assume that child groups
+		 * SD_NUMA domains cannot assume that child groups
 		 * span the current group.
 		 */
 
@@ -9941,7 +9941,7 @@ void update_group_capacity(struct sched_domain *sd, int cpu)
 		}
 	} else  {
 		/*
-		 * !SD_OVERLAP domains can assume that child groups
+		 * !SD_NUMA domains can assume that child groups
 		 * span the current group.
 		 */
 

kernel/sched/topology.c

@@ -89,7 +89,7 @@ static int sched_domain_debug_one(struct sched_domain *sd, int cpu, int level,
 			break;
 		}
 
-		if (!(sd->flags & SD_OVERLAP) &&
+		if (!(sd->flags & SD_NUMA) &&
 		    cpumask_intersects(groupmask, sched_group_span(group))) {
 			printk(KERN_CONT "\n");
 			printk(KERN_ERR "ERROR: repeated CPUs\n");
@@ -102,7 +102,7 @@ static int sched_domain_debug_one(struct sched_domain *sd, int cpu, int level,
 				group->sgc->id,
 				cpumask_pr_args(sched_group_span(group)));
 
-		if ((sd->flags & SD_OVERLAP) &&
+		if ((sd->flags & SD_NUMA) &&
 		    !cpumask_equal(group_balance_mask(group), sched_group_span(group))) {
 			printk(KERN_CONT " mask=%*pbl",
 				cpumask_pr_args(group_balance_mask(group)));
@@ -1359,7 +1359,7 @@ void sched_update_asym_prefer_cpu(int cpu, int old_prio, int new_prio)
 		 * "sg->asym_prefer_cpu" to "sg->sgc->asym_prefer_cpu"
 		 * which is shared by all the overlapping groups.
 		 */
-		WARN_ON_ONCE(sd->flags & SD_OVERLAP);
+		WARN_ON_ONCE(sd->flags & SD_NUMA);
 
 		sg = sd->groups;
 		if (cpu != sg->asym_prefer_cpu) {
@@ -2031,7 +2031,6 @@ void sched_init_numa(int offline_node)
 	for (j = 1; j < nr_levels; i++, j++) {
 		tl[i] = SDTL_INIT(sd_numa_mask, cpu_numa_flags, NUMA);
 		tl[i].numa_level = j;
-		tl[i].flags = SDTL_OVERLAP;
 	}
 
 	sched_domain_topology_saved = sched_domain_topology;
@@ -2342,7 +2341,7 @@ static void __sdt_free(const struct cpumask *cpu_map)
 
 			if (sdd->sd) {
 				sd = *per_cpu_ptr(sdd->sd, j);
-				if (sd && (sd->flags & SD_OVERLAP))
+				if (sd && (sd->flags & SD_NUMA))
 					free_sched_groups(sd->groups, 0);
 				kfree(*per_cpu_ptr(sdd->sd, j));
 			}
@@ -2408,9 +2407,13 @@ static bool topology_span_sane(const struct cpumask *cpu_map)
 	id_seen = sched_domains_tmpmask2;
 
 	for_each_sd_topology(tl) {
+		int tl_common_flags = 0;
+
+		if (tl->sd_flags)
+			tl_common_flags = (*tl->sd_flags)();
 
 		/* NUMA levels are allowed to overlap */
-		if (tl->flags & SDTL_OVERLAP)
+		if (tl_common_flags & SD_NUMA)
 			continue;
 
 		cpumask_clear(covered);
@@ -2481,8 +2484,6 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att
 
 			if (tl == sched_domain_topology)
 				*per_cpu_ptr(d.sd, i) = sd;
-			if (tl->flags & SDTL_OVERLAP)
-				sd->flags |= SD_OVERLAP;
 			if (cpumask_equal(cpu_map, sched_domain_span(sd)))
 				break;
 		}
@@ -2495,7 +2496,7 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att
 	for_each_cpu(i, cpu_map) {
 		for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) {
 			sd->span_weight = cpumask_weight(sched_domain_span(sd));
-			if (sd->flags & SD_OVERLAP) {
+			if (sd->flags & SD_NUMA) {
 				if (build_overlap_sched_groups(sd, i))
 					goto error;
 			} else {