[PATCH mpam mpam/snapshot+extras/v6.18-rc1 v2 3/3] fs/resctrl: Migrate IOMMU groups when removing resource groups

[Zeng Heng]

When deleting a control group, monitor group, or unmounting the resctrl
filesystem, migrate all associated IOMMU groups to the appropriate
destination:
  * Control group deletion: move IOMMU groups to the default group
  * Monitor group deletion: move IOMMU groups to the parent control group
  * Filesystem unmount: move all IOMMU groups to the default group

Without this migration, IOMMU groups remain bound to stale PARTID/PMG
values of the destroyed group, causing them to "disappear" from the
resctrl interface.

Add rdt_move_group_iommus() to handle this migration, mirroring the
existing rdt_move_group_tasks() pattern for task migration.

When deleting a control group or unmounting the resctrl file system, it
is necessary to move its all iommu_groups back to the default group. When
removing a monitor group, need to move its iommu_groups back to the parent
control group.

Otherwise, these iommu_groups remain bound to the old PARTID and PMG, and
they will appear to "disappear" from the resctrl fs.

Signed-off-by: Zeng Heng <zengheng4@xxxxxxxxxx>
---
 fs/resctrl/rdtgroup.c | 47 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index e92b5dcb6f2e..351e430bde1a 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -3292,6 +3292,44 @@ static void rdt_move_group_tasks(struct rdtgroup *from, struct rdtgroup *to,
 	read_unlock(&tasklist_lock);
 }
 
+static int rdt_move_group_iommus(struct rdtgroup *from, struct rdtgroup *to)
+{
+	struct kset *iommu_groups;
+	struct iommu_group *group;
+	int err = 0, iommu_group_id;
+	struct kobject *group_kobj = NULL;
+
+	if (!IS_ENABLED(CONFIG_RESCTRL_IOMMU))
+		return 0;
+
+	if (from == to)
+		return 0;
+
+	iommu_groups = iommu_get_group_kset();
+
+	while ((group_kobj = kset_get_next_obj(iommu_groups, group_kobj))) {
+		/* iommu_group_get_from_kobj() wants to drop a reference */
+		kobject_get(group_kobj);
+
+		group = iommu_group_get_from_kobj(group_kobj);
+		if (!group)
+			continue;
+
+		if (!from || iommu_matches_rdtgroup(group, from)) {
+			err = kstrtoint(group_kobj->name, 0, &iommu_group_id);
+			if (err)
+				break;
+
+			err = rdtgroup_move_iommu(iommu_group_id, to);
+			if (err)
+				break;
+		}
+	}
+
+	kset_put(iommu_groups);
+	return err;
+}
+
 static void free_all_child_rdtgrp(struct rdtgroup *rdtgrp)
 {
 	struct rdtgroup *sentry, *stmp;
@@ -3320,6 +3358,9 @@ static void rmdir_all_sub(void)
 	/* Move all tasks to the default resource group */
 	rdt_move_group_tasks(NULL, &rdtgroup_default, NULL);
 
+	/* Move all iommu_groups to the default resource group */
+	rdt_move_group_iommus(NULL, &rdtgroup_default);
+
 	list_for_each_entry_safe(rdtgrp, tmp, &rdt_all_groups, rdtgroup_list) {
 		/* Free any child rmids */
 		free_all_child_rdtgrp(rdtgrp);
@@ -4189,6 +4230,9 @@ static int rdtgroup_rmdir_mon(struct rdtgroup *rdtgrp, cpumask_var_t tmpmask)
 	/* Give any tasks back to the parent group */
 	rdt_move_group_tasks(rdtgrp, prdtgrp, tmpmask);
 
+	/* Give any iommu_groups back to the parent group */
+	rdt_move_group_iommus(rdtgrp, prdtgrp);
+
 	/*
 	 * Update per cpu closid/rmid of the moved CPUs first.
 	 * Note: the closid will not change, but the arch code still needs it.
@@ -4239,6 +4283,9 @@ static int rdtgroup_rmdir_ctrl(struct rdtgroup *rdtgrp, cpumask_var_t tmpmask)
 	/* Give any tasks back to the default group */
 	rdt_move_group_tasks(rdtgrp, &rdtgroup_default, tmpmask);
 
+	/* Give any iommu_groups back to the default group */
+	rdt_move_group_iommus(rdtgrp, &rdtgroup_default);
+
 	/* Give any CPUs back to the default group */
 	cpumask_or(&rdtgroup_default.cpu_mask,
 		   &rdtgroup_default.cpu_mask, &rdtgrp->cpu_mask);
-- 
2.25.1