linux-kernel - [RFC PATCH v3] nubus: Don't list slot resources by default

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Date:   Sun, 26 Mar 2023 14:37:02 +1100
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: [RFC PATCH v3] 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>
Tested-by: Stan Johnson <userm57@...oo.com>
Signed-off-by: Finn Thain <fthain@...ux-m68k.org>
---
 drivers/nubus/nubus.c | 12 +++++++++---
 drivers/nubus/proc.c  |  8 ++++----
 include/linux/nubus.h |  1 +
 3 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/drivers/nubus/nubus.c b/drivers/nubus/nubus.c
index f70ba58dbc55..d2d2b580f646 100644
--- a/drivers/nubus/nubus.c
+++ b/drivers/nubus/nubus.c
@@ -32,6 +32,12 @@
 
 /* Globals */
 
+/* This parameter makes slot resources available in procfs. It's deprecated and
+ * disabled by default as procfs is no longer thought to be suitable for that.
+ */
+bool populate_procfs;
+module_param(populate_procfs, bool, 0);
+
 LIST_HEAD(nubus_func_rsrcs);
 
 /* Meaning of "bytelanes":
@@ -572,9 +578,9 @@ 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 (populate_procfs)
+				nubus_get_private_resource(fres, dir.procdir,
+							   &ent);
 		}
 	}
 
diff --git a/drivers/nubus/proc.c b/drivers/nubus/proc.c
index 2c320a84fd72..1808accb8214 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 || !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 || !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 || !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 || !populate_procfs)
 		return;
 
 	snprintf(name, sizeof(name), "%x", ent->type);
diff --git a/include/linux/nubus.h b/include/linux/nubus.h
index 392fc6c53e96..50c9145808d1 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 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