[PATCH v5 08/12] cpuset: introduce local_partition_enable()

[Ridong Chen <ridong.chen@linux.dev>]

From: Ridong Chen <chenridong@xiaomi.com>

Factor the local partition enablement out of
update_parent_effective_cpumask() into local_partition_enable(). It
computes the effective exclusive CPUs of the cpuset, validates them
with validate_local_partition() and then calls partition_enable() to
set up the partition, the same way as remote_partition_enable() does
for a remote partition.

As validate_local_partition() already rejects a root partition under an
isolated parent, the PERR_ISOPARENT check in update_prstate() is no
longer needed and is removed.

Signed-off-by: Ridong Chen <chenridong@xiaomi.com>
---
 kernel/cgroup/cpuset.c | 84 +++++++++++++++++++++++-------------------
 1 file changed, 46 insertions(+), 38 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 78ca3c39c029..45605c6ab6a2 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -2016,10 +2016,9 @@ static bool is_user_xcpus_exclusive(struct cpuset *cs)
  * Important: The caller must ensure that @cs's cpu mask is updated before
  * invoking this function when exclusive CPU validation is required.
  */
-static enum prs_errcode __maybe_unused
-validate_local_partition(struct cpuset *cs, int new_prs,
-			 struct cpumask *excpus, bool excl_check,
-			 struct tmpmasks *tmp)
+static enum prs_errcode validate_local_partition(struct cpuset *cs, int new_prs,
+						 struct cpumask *excpus, bool excl_check,
+						 struct tmpmasks *tmp)
 {
 	struct cpuset *parent = parent_cs(cs);
 
@@ -2044,6 +2043,47 @@ validate_local_partition(struct cpuset *cs, int new_prs,
 				  tmp ? tmp->delmask : NULL);
 }
 
+/**
+ * local_partition_enable - Enable local partition for a cpuset
+ * @cs: Target cpuset to become a local partition root
+ * @new_prs: New partition root state to apply
+ * @tmp: Temporary masks for CPU calculations
+ *
+ * Return: 0 on success, error code on failure
+ */
+static int local_partition_enable(struct cpuset *cs,
+				  int new_prs, struct tmpmasks *tmp)
+{
+	struct cpuset *parent = parent_cs(cs);
+	enum prs_errcode err;
+
+	lockdep_assert_cpuset_lock_held();
+	WARN_ON_ONCE(is_remote_partition(cs));	/* For local partition only */
+
+	compute_excpus(cs, tmp->new_cpus);
+	err = validate_local_partition(cs, new_prs, tmp->new_cpus, false, NULL);
+	if (err)
+		return err;
+
+	/*
+	 * This function will only be called when all the preliminary
+	 * checks have passed. At this point, the following condition
+	 * should hold.
+	 *
+	 * (new effective_xcpus & cpu_active_mask) ⊆ parent->effective_cpus
+	 *
+	 * Warn if it is not the case.
+	 */
+	cpumask_and(tmp->addmask, tmp->new_cpus, cpu_active_mask);
+	WARN_ON_ONCE(!cpumask_subset(tmp->addmask, parent->effective_cpus));
+
+	partition_enable(cs, parent, new_prs, tmp->new_cpus);
+
+	cpuset_update_tasks_cpumask(parent, tmp->addmask);
+	update_sibling_cpumasks(parent, cs, tmp);
+	return 0;
+}
+
 /**
  * update_parent_effective_cpumask - update effective_cpus mask of parent cpuset
  * @cs:      The cpuset that requests change in partition root state
@@ -2142,27 +2182,7 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
 		nocpu = tasks_nocpu_error(parent, cs, tmp->delmask);
 	}
 
-	if ((cmd == partcmd_enable) || (cmd == partcmd_enablei)) {
-		new_prs = (cmd == partcmd_enable) ? PRS_ROOT : PRS_ISOLATED;
-
-		part_error = validate_partition(cs, parent, new_prs,
-						tmp->delmask, NULL);
-		if (part_error)
-			return part_error;
-
-		/*
-		 * This function will only be called when all the preliminary
-		 * checks have passed. At this point, the following condition
-		 * should hold.
-		 *
-		 * (cs->effective_xcpus & cpu_active_mask) ⊆ parent->effective_cpus
-		 *
-		 * Warn if it is not the case.
-		 */
-		cpumask_and(tmp->new_cpus, tmp->delmask, cpu_active_mask);
-		WARN_ON_ONCE(!cpumask_subset(tmp->new_cpus, parent->effective_cpus));
-		deleting = true;
-	} else if (cmd == partcmd_disable) {
+	if (cmd == partcmd_disable) {
 		/*
 		 * May need to add cpus back to parent's effective_cpus
 		 * (and maybe removed from subpartitions_cpus/isolated_cpus)
@@ -3112,7 +3132,6 @@ static int update_prstate(struct cpuset *cs, int new_prs)
 	int err = PERR_NONE, old_prs = cs->partition_root_state;
 	struct cpuset *parent = parent_cs(cs);
 	struct tmpmasks tmpmask;
-	int parent_prs = parent->partition_root_state;
 	bool isolcpus_updated = false;
 	bool disable_partition = false;
 
@@ -3155,18 +3174,7 @@ static int update_prstate(struct cpuset *cs, int new_prs)
 		 * Otherwise, enable a remote partition.
 		 */
 		if (is_partition_valid(parent)) {
-			enum partition_cmd cmd = (new_prs == PRS_ROOT)
-					       ? partcmd_enable : partcmd_enablei;
-
-			/*
-			 * It is not allowed to create a root partition under
-			 * an isolated parent partition.
-			 */
-			if ((new_prs == PRS_ROOT) && (parent_prs == PRS_ISOLATED)) {
-				err = PERR_ISOPARENT;
-				goto out;
-			}
-			err = update_parent_effective_cpumask(cs, cmd, NULL, &tmpmask);
+			err = local_partition_enable(cs, new_prs, &tmpmask);
 		} else {
 			err = remote_partition_enable(cs, new_prs, &tmpmask);
 		}
-- 
2.34.1