[RFC PATCH 29/31] fs/resctrl: Expose emulation controllers in a resource_schemata subdir

[Chen Yu]

The legacy MBA default controller is emulated by other controls (for
ERDT, "MB" is emulated by the MAX control of every memory region).

When a control is emulated (resctrl_ctrl::emul is not empty), do not
expose the control's own properties. Keep the control's own
resource_schemata directory and, underneath it, create a sub-directory
named after each emulation controller that holds that emulation
controller's properties. For example:

  [root@ MB]# tree resource_schemata/
  resource_schemata/
  ├── MB
  │   ├── MB_REGION0_MAX
  │   │   ├── max
  │   │   ├── min
  │   │   ├── resolution
  │   │   ├── scale
  │   │   ├── scope
  │   │   ├── tolerance
  │   │   ├── type
  │   │   └── unit
  │   └── MB_REGION1_MAX
  │       ├── max
  │       ├── min
  │       ├── resolution
  │       ├── scale
  │       ├── scope
  │       ├── tolerance
  │       ├── type
  │       └── unit

Controls without an emulation controller keep exposing their own
properties directly.

Signed-off-by: Chen Yu <yu.c.chen@xxxxxxxxx>
---
 fs/resctrl/rdtgroup.c | 31 +++++++++++++++++++++++++++----
 1 file changed, 27 insertions(+), 4 deletions(-)

diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index c1aac0dcd332..31bea5a9833b 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -2741,13 +2741,36 @@ static int resctrl_mkdir_schemata_dir(struct kernfs_node *kn,
 		if (IS_ERR(kn_ctrl))
 			return PTR_ERR(kn_ctrl);
 
-		ret = rdtgroup_kn_set_ugid(kn_subdir);
+		ret = rdtgroup_kn_set_ugid(kn_ctrl);
 		if (ret)
 			return ret;
 
-		ret = resctrl_add_ctrl_files(kn_ctrl, ctrl);
-		if (ret)
-			return ret;
+		if (!list_empty(&ctrl->emul)) {
+			struct kernfs_node *kn_emul;
+			struct resctrl_ctrl *emul;
+
+			for_each_emul_ctrl(emul, ctrl) {
+				snprintf(ctrl_full_name, sizeof(ctrl_full_name), "%s_%s",
+					 f->name, resctrl_ctrl_name_str(emul->name));
+
+				kn_emul = kernfs_create_dir(kn_ctrl, ctrl_full_name,
+							    kn_ctrl->mode, emul);
+				if (IS_ERR(kn_emul))
+					return PTR_ERR(kn_emul);
+
+				ret = rdtgroup_kn_set_ugid(kn_emul);
+				if (ret)
+					return ret;
+
+				ret = resctrl_add_ctrl_files(kn_emul, emul);
+				if (ret)
+					return ret;
+			}
+		} else {
+			ret = resctrl_add_ctrl_files(kn_ctrl, ctrl);
+			if (ret)
+				return ret;
+		}
 	}
 
 	kernfs_activate(kn_subdir);
-- 
2.43.0