cpuset: remove v1-specific code from generate_sched_domains

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@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

Author: Chen Ridong

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
 };
 
@@ -314,8 +314,6 @@ 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);
 
@@ -330,8 +328,6 @@ 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; };
 

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;

kernel/cgroup/cpuset.c

@@ -789,89 +789,40 @@ 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;
 	dattr = NULL;
 	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;
+		/* !csa will be checked and can be correctly handled */
+		goto generate_doms;
 	}
 
 	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) {
-		if (cp == &top_cpuset)
-			continue;
-
-		if (cgrpv2)
-			goto v2;
-
-		/*
-		 * v1:
-		 * Continue traversing beyond @cp iff @cp has some CPUs and
-		 * isn't load balancing.  The former is obvious.  The
-		 * latter: All child cpusets contain a subset of the
-		 * parent's cpus, so just skip them, and then we call
-		 * update_domain_attr_tree() to calc relax_domain_level of
-		 * the corresponding sched domain.
-		 */
-		if (!cpumask_empty(cp->cpus_allowed) &&
-		    !(is_sched_load_balance(cp) &&
-		      cpumask_intersects(cp->cpus_allowed,
-					 housekeeping_cpumask(HK_TYPE_DOMAIN))))
-			continue;
-
-		if (is_sched_load_balance(cp) &&
-		    !cpumask_empty(cp->effective_cpus))
-			csa[csn++] = cp;
-
-		/* skip @cp's subtree */
-		pos_css = css_rightmost_descendant(pos_css);
-		continue;
-
-v2:
 		/*
 		 * Only valid partition roots that are not isolated and with
-		 * non-empty effective_cpus will be saved into csn[].
+		 * non-empty effective_cpus will be saved into csa[].
 		 */
 		if ((cp->partition_root_state == PRS_ROOT) &&
 		    !cpumask_empty(cp->effective_cpus))
-			csa[csn++] = cp;
+			csa[ndoms++] = cp;
 
 		/*
 		 * Skip @cp's subtree if not a partition root and has no
@@ -882,40 +833,18 @@ static int generate_sched_domains(cpumask_var_t **domains,
 	}
 	rcu_read_unlock();
 
-	/*
-	 * If there are only isolated partitions underneath the cgroup root,
-	 * we can optimize out unneeded sched domains scanning.
-	 */
-	if (root_load_balance && (csn == 1))
-		goto single_root_domain;
-
-	for (i = 0; i < csn; i++)
-		uf_node_init(&csa[i]->node);
-
-	/* Merge overlapping cpusets */
-	for (i = 0; i < csn; i++) {
-		for (j = i + 1; j < csn; j++) {
-			if (cpusets_overlap(csa[i], csa[j])) {
+	for (i = 0; i < ndoms; i++) {
+		for (j = i + 1; j < ndoms; j++) {
+			if (cpusets_overlap(csa[i], csa[j]))
 				/*
 				 * Cgroup v2 shouldn't pass down overlapping
 				 * partition root cpusets.
 				 */
-				WARN_ON_ONCE(cgrpv2);
-				uf_union(&csa[i]->node, &csa[j]->node);
-			}
+				WARN_ON_ONCE(1);
 		}
 	}
 
-	/* Count the total number of domains */
-	for (i = 0; i < csn; i++) {
-		if (uf_find(&csa[i]->node) == &csa[i]->node)
-			ndoms++;
-	}
-
-	/*
-	 * Now we know how many domains to create.
-	 * Convert <csn, csa> to <ndoms, doms> and populate cpu masks.
-	 */
+generate_doms:
 	doms = alloc_sched_domains(ndoms);
 	if (!doms)
 		goto done;
@@ -932,45 +861,19 @@ static int generate_sched_domains(cpumask_var_t **domains,
 	 * to SD_ATTR_INIT. Also non-isolating partition root CPUs are a
 	 * subset of HK_TYPE_DOMAIN housekeeping CPUs.
 	 */
-	if (cgrpv2) {
-		for (i = 0; i < ndoms; i++) {
-			/*
-			 * The top cpuset may contain some boot time isolated
-			 * CPUs that need to be excluded from the sched domain.
-			 */
-			if (csa[i] == &top_cpuset)
-				cpumask_and(doms[i], csa[i]->effective_cpus,
-					    housekeeping_cpumask(HK_TYPE_DOMAIN));
-			else
-				cpumask_copy(doms[i], csa[i]->effective_cpus);
-			if (dattr)
-				dattr[i] = SD_ATTR_INIT;
-		}
-		goto done;
-	}
-
-	for (nslot = 0, i = 0; i < csn; i++) {
-		nslot_update = 0;
-		for (j = i; j < csn; j++) {
-			if (uf_find(&csa[j]->node) == &csa[i]->node) {
-				struct cpumask *dp = doms[nslot];
-
-				if (i == j) {
-					nslot_update = 1;
-					cpumask_clear(dp);
-					if (dattr)
-						*(dattr + nslot) = SD_ATTR_INIT;
-				}
-				cpumask_or(dp, dp, csa[j]->effective_cpus);
-				cpumask_and(dp, dp, housekeeping_cpumask(HK_TYPE_DOMAIN));
-				if (dattr)
-					update_domain_attr_tree(dattr + nslot, csa[j]);
-			}
-		}
-		if (nslot_update)
-			nslot++;
+	for (i = 0; i < ndoms; i++) {
+		/*
+		 * The top cpuset may contain some boot time isolated
+		 * CPUs that need to be excluded from the sched domain.
+		 */
+		if (!csa || csa[i] == &top_cpuset)
+			cpumask_and(doms[i], top_cpuset.effective_cpus,
+				    housekeeping_cpumask(HK_TYPE_DOMAIN));
+		else
+			cpumask_copy(doms[i], csa[i]->effective_cpus);
+		if (dattr)
+			dattr[i] = SD_ATTR_INIT;
 	}
-	BUG_ON(nslot != ndoms);
 
 done:
 	kfree(csa);