[PATCH v7 17/19] fs/resctrl: Control visibility of global per-CPU kernel mode group files

[Babu Moger <babu.moger@amd.com>]

The kmode_cpus and kmode_cpus_list files are specific to the global per-CPU
kernel mode. These files are created in a hidden state when an rdtgroup is
created.

Introduce resctrl_kmode_global_files_show() to control the visibility of
these files for individual resource groups. Show the files only for the
group backing the active global per-CPU kernel mode and hide them for all
other groups.

Suggested-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Babu Moger <babu.moger@amd.com>
---
v7: Updated the prototype rdtgroup_kmode_global_files_show().
    Moved the patch after both rdtgroup_kmode_global_activate() and
    rdtgroup_kmode_global_deactivate() is Introduced, so the change is
    symmetrical.
    Updated the changelog.

v6: Helper named for the global per-CPU files instead of unhiding every
    hidden file on the group.
    https://lore.kernel.org/lkml/34aa4824-810b-4c81-8188-f2f37e1dc277@intel.com/
---
 fs/resctrl/rdtgroup.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index 1ad169e714a4..86bd6a66812b 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -1136,6 +1136,24 @@ static int resctrl_kernel_mode_show(struct kernfs_open_file *of,
 	return 0;
 }
 
+/* Show or hide kmode_cpus and kmode_cpus_list on @kn. */
+static void resctrl_kmode_global_files_show(struct rdtgroup *rdtgrp, bool show)
+{
+	struct kernfs_node *kn_file;
+
+	kn_file = kernfs_find_and_get(rdtgrp->kn, "kmode_cpus");
+	if (kn_file) {
+		kernfs_show(kn_file, show);
+		kernfs_put(kn_file);
+	}
+
+	kn_file = kernfs_find_and_get(rdtgrp->kn, "kmode_cpus_list");
+	if (kn_file) {
+		kernfs_show(kn_file, show);
+		kernfs_put(kn_file);
+	}
+}
+
 /*
  * resctrl_kmode_global_online_cpu() - Program kernel mode association for @cpu
  * @cpu: CPU that has just been brought online
@@ -1194,6 +1212,7 @@ static void rdtgroup_kmode_global_deactivate(struct rdtgroup *rdtgrp)
 
 	resctrl_configure_kmode_global(&rdtgrp->kmode_cpu_mask, rdtgrp, false);
 	cpumask_clear(&rdtgrp->kmode_cpu_mask);
+	resctrl_kmode_global_files_show(rdtgrp, false);
 
 	resctrl_kmode.rdtgrp = NULL;
 	resctrl_kmode.active = RESCTRL_INHERIT_USER;
@@ -1214,6 +1233,7 @@ static void rdtgroup_kmode_global_activate(struct rdtgroup *rdtgrp,
 
 	cpumask_copy(&rdtgrp->kmode_cpu_mask, cpu_online_mask);
 	resctrl_configure_kmode_global(&rdtgrp->kmode_cpu_mask, rdtgrp, true);
+	resctrl_kmode_global_files_show(rdtgrp, true);
 }
 
 static int resctrl_kmode_parse_state(char *val, enum kmode_state *state)
-- 
2.43.0