Message-Id: <20251025064844.495525-15-chenridong@huaweicloud.com>
Date: Sat, 25 Oct 2025 06:48:36 +0000
From: Chen Ridong <chenridong@...weicloud.com>
To: longman@...hat.com,
	tj@...nel.org,
	hannes@...xchg.org,
	mkoutny@...e.com
Cc: cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	lujialin4@...wei.com,
	chenridong@...wei.com
Subject: [PATCH RFC v2 14/22] cpuset: remove update_parent_effective_cpumask

From: Chen Ridong <chenridong@...wei.com>

Clean up by removing the update_parent_effective_cpumask() function.
Its logic has now been fully replaced and centralized by the new
helper functions.

Signed-off-by: Chen Ridong <chenridong@...wei.com>
---
 kernel/cgroup/cpuset.c | 266 -----------------------------------------
 1 file changed, 266 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 49df38237c1d..21dd9e0f16ee 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -2085,272 +2085,6 @@ static int local_partition_update(struct cpuset *cs, struct tmpmasks *tmp)
 	return __local_partition_update(cs, NULL, tmp->new_cpus, tmp, true);
 }
 
-/**
- * update_parent_effective_cpumask - update effective_cpus mask of parent cpuset
- * @cs:      The cpuset that requests change in partition root state
- * @cmd:     Partition root state change command
- * @newmask: Optional new cpumask for partcmd_update
- * @tmp:     Temporary addmask and delmask
- * Return:   0 or a partition root state error code
- *
- * For partcmd_enable*, the cpuset is being transformed from a non-partition
- * root to a partition root. The effective_xcpus (cpus_allowed if
- * effective_xcpus not set) mask of the given cpuset will be taken away from
- * parent's effective_cpus. The function will return 0 if all the CPUs listed
- * in effective_xcpus can be granted or an error code will be returned.
- *
- * For partcmd_disable, the cpuset is being transformed from a partition
- * root back to a non-partition root. Any CPUs in effective_xcpus will be
- * given back to parent's effective_cpus. 0 will always be returned.
- *
- * For partcmd_update, if the optional newmask is specified, the cpu list is
- * to be changed from effective_xcpus to newmask. Otherwise, effective_xcpus is
- * assumed to remain the same. The cpuset should either be a valid or invalid
- * partition root. The partition root state may change from valid to invalid
- * or vice versa. An error code will be returned if transitioning from
- * invalid to valid violates the exclusivity rule.
- *
- * For partcmd_invalidate, the current partition will be made invalid.
- *
- * The partcmd_enable* and partcmd_disable commands are used by
- * update_prstate(). An error code may be returned and the caller will check
- * for error.
- *
- * The partcmd_update command is used by update_cpumasks_hier() with newmask
- * NULL and update_cpumask() with newmask set. The partcmd_invalidate is used
- * by update_cpumask() with NULL newmask. In both cases, the callers won't
- * check for error and so partition_root_state and prs_err will be updated
- * directly.
- */
-static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
-					   struct cpumask *newmask,
-					   struct tmpmasks *tmp)
-{
-	struct cpuset *parent = parent_cs(cs);
-	int adding;	/* Adding cpus to parent's effective_cpus	*/
-	int deleting;	/* Deleting cpus from parent's effective_cpus	*/
-	int old_prs, new_prs;
-	int part_error = PERR_NONE;	/* Partition error? */
-	int isolcpus_updated = 0;
-	struct cpumask *xcpus = user_xcpus(cs);
-	bool nocpu;
-
-	lockdep_assert_held(&cpuset_mutex);
-	WARN_ON_ONCE(is_remote_partition(cs));	/* For local partition only */
-
-	/*
-	 * new_prs will only be changed for the partcmd_update and
-	 * partcmd_invalidate commands.
-	 */
-	adding = deleting = false;
-	old_prs = new_prs = cs->partition_root_state;
-
-	/*
-	 * The parent must be a partition root.
-	 * The new cpumask, if present, or the current cpus_allowed must
-	 * not be empty.
-	 */
-	if (!is_partition_valid(parent)) {
-		return is_partition_invalid(parent)
-		       ? PERR_INVPARENT : PERR_NOTPART;
-	}
-	if (!newmask && xcpus_empty(cs))
-		return PERR_CPUSEMPTY;
-
-	nocpu = tasks_nocpu_error(parent, cs, xcpus);
-
-	if (newmask) {
-		/*
-		 * Empty cpumask is not allowed
-		 */
-		if (cpumask_empty(newmask)) {
-			part_error = PERR_CPUSEMPTY;
-			goto write_error;
-		}
-
-		/* Check newmask again, whether cpus are available for parent/cs */
-		nocpu |= tasks_nocpu_error(parent, cs, newmask);
-
-		/*
-		 * partcmd_update with newmask:
-		 *
-		 * Compute add/delete mask to/from effective_cpus
-		 *
-		 * For valid partition:
-		 *   addmask = exclusive_cpus & ~newmask
-		 *			      & parent->effective_xcpus
-		 *   delmask = newmask & ~exclusive_cpus
-		 *		       & parent->effective_xcpus
-		 *
-		 * For invalid partition:
-		 *   delmask = newmask & parent->effective_xcpus
-		 */
-		if (is_partition_invalid(cs)) {
-			adding = false;
-			deleting = cpumask_and(tmp->delmask,
-					newmask, parent->effective_xcpus);
-		} else {
-			cpumask_andnot(tmp->addmask, xcpus, newmask);
-			adding = cpumask_and(tmp->addmask, tmp->addmask,
-					     parent->effective_xcpus);
-
-			cpumask_andnot(tmp->delmask, newmask, xcpus);
-			deleting = cpumask_and(tmp->delmask, tmp->delmask,
-					       parent->effective_xcpus);
-		}
-		/*
-		 * The new CPUs to be removed from parent's effective CPUs
-		 * must be present.
-		 */
-		if (deleting) {
-			cpumask_and(tmp->new_cpus, tmp->delmask, cpu_active_mask);
-			WARN_ON_ONCE(!cpumask_subset(tmp->new_cpus, parent->effective_cpus));
-		}
-
-		/*
-		 * Make partition invalid if parent's effective_cpus could
-		 * become empty and there are tasks in the parent.
-		 */
-		if (nocpu && (!adding ||
-		    !cpumask_intersects(tmp->addmask, cpu_active_mask))) {
-			part_error = PERR_NOCPUS;
-			deleting = false;
-			adding = cpumask_and(tmp->addmask,
-					     xcpus, parent->effective_xcpus);
-		}
-	} else {
-		/*
-		 * partcmd_update w/o newmask
-		 *
-		 * delmask = effective_xcpus & parent->effective_cpus
-		 *
-		 * This can be called from:
-		 * 1) update_cpumasks_hier()
-		 * 2) cpuset_hotplug_update_tasks()
-		 *
-		 * Check to see if it can be transitioned from valid to
-		 * invalid partition or vice versa.
-		 *
-		 * A partition error happens when parent has tasks and all
-		 * its effective CPUs will have to be distributed out.
-		 */
-		if (nocpu) {
-			part_error = PERR_NOCPUS;
-			if (is_partition_valid(cs))
-				adding = cpumask_and(tmp->addmask,
-						xcpus, parent->effective_xcpus);
-		} else if (is_partition_invalid(cs) && !cpumask_empty(xcpus) &&
-			   cpumask_subset(xcpus, parent->effective_xcpus)) {
-			struct cgroup_subsys_state *css;
-			struct cpuset *child;
-			bool exclusive = true;
-
-			/*
-			 * Convert invalid partition to valid has to
-			 * pass the cpu exclusivity test.
-			 */
-			rcu_read_lock();
-			cpuset_for_each_child(child, css, parent) {
-				if (child == cs)
-					continue;
-				if (!cpusets_are_exclusive(cs, child)) {
-					exclusive = false;
-					break;
-				}
-			}
-			rcu_read_unlock();
-			if (exclusive)
-				deleting = cpumask_and(tmp->delmask,
-						xcpus, parent->effective_cpus);
-			else
-				part_error = PERR_NOTEXCL;
-		}
-	}
-
-write_error:
-	if (part_error)
-		WRITE_ONCE(cs->prs_err, part_error);
-
-	if (cmd == partcmd_update) {
-		/*
-		 * Check for possible transition between valid and invalid
-		 * partition root.
-		 */
-		switch (cs->partition_root_state) {
-		case PRS_ROOT:
-		case PRS_ISOLATED:
-			if (part_error)
-				new_prs = -old_prs;
-			break;
-		case PRS_INVALID_ROOT:
-		case PRS_INVALID_ISOLATED:
-			if (!part_error)
-				new_prs = -old_prs;
-			break;
-		}
-	}
-
-	if (!adding && !deleting && (new_prs == old_prs))
-		return 0;
-
-	/*
-	 * Transitioning between invalid to valid or vice versa may require
-	 * changing CS_CPU_EXCLUSIVE. In the case of partcmd_update,
-	 * validate_change() has already been successfully called and
-	 * CPU lists in cs haven't been updated yet. So defer it to later.
-	 */
-	if ((old_prs != new_prs) && (cmd != partcmd_update))  {
-		int err = update_partition_exclusive_flag(cs, new_prs);
-
-		if (err)
-			return err;
-	}
-
-	/*
-	 * Change the parent's effective_cpus & effective_xcpus (top cpuset
-	 * only).
-	 *
-	 * Newly added CPUs will be removed from effective_cpus and
-	 * newly deleted ones will be added back to effective_cpus.
-	 */
-	spin_lock_irq(&callback_lock);
-	if (old_prs != new_prs)
-		cs->partition_root_state = new_prs;
-
-	/*
-	 * Adding to parent's effective_cpus means deletion CPUs from cs
-	 * and vice versa.
-	 */
-	if (adding)
-		isolcpus_updated += partition_xcpus_del(old_prs, parent,
-							tmp->addmask);
-	if (deleting)
-		isolcpus_updated += partition_xcpus_add(new_prs, parent,
-							tmp->delmask);
-
-	spin_unlock_irq(&callback_lock);
-	update_unbound_workqueue_cpumask(isolcpus_updated);
-
-	if ((old_prs != new_prs) && (cmd == partcmd_update))
-		update_partition_exclusive_flag(cs, new_prs);
-
-	if (adding || deleting) {
-		cpuset_update_tasks_cpumask(parent, tmp->addmask);
-		update_sibling_cpumasks(parent, cs, tmp);
-	}
-
-	/*
-	 * For partcmd_update without newmask, it is being called from
-	 * cpuset_handle_hotplug(). Update the load balance flag and
-	 * scheduling domain accordingly.
-	 */
-	if ((cmd == partcmd_update) && !newmask)
-		update_partition_sd_lb(cs, old_prs);
-
-	notify_partition_change(cs, old_prs);
-	return 0;
-}
-
 /**
  * compute_partition_effective_cpumask - compute effective_cpus for partition
  * @cs: partition root cpuset
-- 
2.34.1

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