linux-kernel - [PATCH v5] nubus: Don't list slot resources by default

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Date:   Tue, 16 May 2023 11:22:05 +1000
From:   Finn Thain <fthain@...ux-m68k.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     "Brad Boyer" <flar@...andria.com>, linux-m68k@...ts.linux-m68k.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v5] nubus: Don't list slot resources by default

Some Nubus card ROMs contain many slot resources. A single Radius video
card produced well over a thousand entries under /proc/bus/nubus/.
Populating /proc/bus/nubus/ on a slow machine with several such cards
installed takes long enough that the user may think that the system is
wedged. All those procfs entries also consume significant RAM though
they are not normally needed (except by developers).
Omit these resources from /proc/bus/nubus/ by default and add a kernel
parameter to enable them when needed.
On the test machine, this saved 300 kB and 10 seconds.

Cc: Brad Boyer <flar@...andria.com>
Reviewed-by: Brad Boyer <flar@...andria.com>
Tested-by: Stan Johnson <userm57@...oo.com>
Signed-off-by: Finn Thain <fthain@...ux-m68k.org>
---
Changed since v4:
 - Renamed the new global variable and adopted module_param_named().
Changed since v3:
 - Better commentary.
Changed since v2:
 - Added commentary.
 - Moved declaration to nubus.h.
Changed since v1:
 - Expanded to cover all slot resources in procfs.
---
 drivers/nubus/nubus.c | 13 ++++++++++---
 drivers/nubus/proc.c  |  8 ++++----
 include/linux/nubus.h |  1 +
 3 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/drivers/nubus/nubus.c b/drivers/nubus/nubus.c
index f70ba58dbc55..ab0f32b901c8 100644
--- a/drivers/nubus/nubus.c
+++ b/drivers/nubus/nubus.c
@@ -32,6 +32,13 @@
 
 /* Globals */
 
+/* The "nubus.populate_procfs" parameter makes slot resources available in
+ * procfs. It's deprecated and disabled by default because procfs is no longer
+ * thought to be suitable for that and some board ROMs make it too expensive.
+ */
+bool nubus_populate_procfs;
+module_param_named(populate_procfs, nubus_populate_procfs, bool, 0);
+
 LIST_HEAD(nubus_func_rsrcs);
 
 /* Meaning of "bytelanes":
@@ -572,9 +579,9 @@ nubus_get_functional_resource(struct nubus_board *board, int slot,
 			nubus_proc_add_rsrc(dir.procdir, &ent);
 			break;
 		default:
-			/* Local/Private resources have their own
-			   function */
-			nubus_get_private_resource(fres, dir.procdir, &ent);
+			if (nubus_populate_procfs)
+				nubus_get_private_resource(fres, dir.procdir,
+							   &ent);
 		}
 	}
 
diff --git a/drivers/nubus/proc.c b/drivers/nubus/proc.c
index 2c320a84fd72..e7a347db708c 100644
--- a/drivers/nubus/proc.c
+++ b/drivers/nubus/proc.c
@@ -55,7 +55,7 @@ struct proc_dir_entry *nubus_proc_add_board(struct nubus_board *board)
 {
 	char name[2];
 
-	if (!proc_bus_nubus_dir)
+	if (!proc_bus_nubus_dir || !nubus_populate_procfs)
 		return NULL;
 	snprintf(name, sizeof(name), "%x", board->slot);
 	return proc_mkdir(name, proc_bus_nubus_dir);
@@ -72,7 +72,7 @@ struct proc_dir_entry *nubus_proc_add_rsrc_dir(struct proc_dir_entry *procdir,
 	char name[9];
 	int lanes = board->lanes;
 
-	if (!procdir)
+	if (!procdir || !nubus_populate_procfs)
 		return NULL;
 	snprintf(name, sizeof(name), "%x", ent->type);
 	remove_proc_subtree(name, procdir);
@@ -157,7 +157,7 @@ void nubus_proc_add_rsrc_mem(struct proc_dir_entry *procdir,
 	char name[9];
 	struct nubus_proc_pde_data *pded;
 
-	if (!procdir)
+	if (!procdir || !nubus_populate_procfs)
 		return;
 
 	snprintf(name, sizeof(name), "%x", ent->type);
@@ -176,7 +176,7 @@ void nubus_proc_add_rsrc(struct proc_dir_entry *procdir,
 	char name[9];
 	unsigned char *data = (unsigned char *)ent->data;
 
-	if (!procdir)
+	if (!procdir || !nubus_populate_procfs)
 		return;
 
 	snprintf(name, sizeof(name), "%x", ent->type);
diff --git a/include/linux/nubus.h b/include/linux/nubus.h
index 392fc6c53e96..bdcd85e622d8 100644
--- a/include/linux/nubus.h
+++ b/include/linux/nubus.h
@@ -93,6 +93,7 @@ extern struct bus_type nubus_bus_type;
 
 /* Generic NuBus interface functions, modelled after the PCI interface */
 #ifdef CONFIG_PROC_FS
+extern bool nubus_populate_procfs;
 void nubus_proc_init(void);
 struct proc_dir_entry *nubus_proc_add_board(struct nubus_board *board);
 struct proc_dir_entry *nubus_proc_add_rsrc_dir(struct proc_dir_entry *procdir,
-- 
2.37.5