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nbd: Don't create all MAX_NBD devices by default all the time

PATCH In review Lars Marowsky-Bree 2 participants 3 messages Apr 14, 2005 – Apr 15, 2005

Subsystems (2)
Block layer Network block device (NBD)
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Lars Marowsky-Bree

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#0 lore raw

PATCH 1/1 nbd: Don't create all MAX_NBD devices by default all the time

From: Lars Marowsky-Bree <[email protected]>

This patches adds the "nbds_max" parameter to the nbd kernel module, which limits the number of nbds allocated. Previously, always all 128 entries were allocated unconditionally, which used to waste resources and needlessly flood the hotplug system with events. (Defaults to 16 now.)

Signed-off-by Lars Marowsky-Bree <[email protected]>
---
 nbd.c |   16 +++++++++++++---
1 files changed, 13 insertions(+), 3 deletions(-)
drivers/block/nbd.c +13 -3
Index: linux-2.6.11/drivers/block/nbd.c
===================================================================
@@ -78,6 +78,7 @@
 #define DBG_RX          0x0200
 #define DBG_TX          0x0400
 static unsigned int debugflags;
+static unsigned int nbds_max;
 #endif /* NDEBUG */
 
 static struct nbd_device nbd_dev[MAX_NBD];

@@ -647,7 +648,13 @@ static int __init nbd_init(void)
 		return -EIO;
 	}
 
-	for (i = 0; i < MAX_NBD; i++) {
+	if (nbds_max > MAX_NBD) {
+		printk(KERN_CRIT "nbd: cannot allocate more than %u nbds; %u requested.\n", MAX_NBD,
+				nbds_max);
+		return -EINVAL;
+	}
+
+	for (i = 0; i < nbds_max; i++) {
 		struct gendisk *disk = alloc_disk(1);
 		if (!disk)
 			goto out;

@@ -673,7 +680,7 @@ static int __init nbd_init(void)
 	dprintk(DBG_INIT, "nbd: debugflags=0x%x\n", debugflags);
 
 	devfs_mk_dir("nbd");
-	for (i = 0; i < MAX_NBD; i++) {
+	for (i = 0; i < nbds_max; i++) {
 		struct gendisk *disk = nbd_dev[i].disk;
 		nbd_dev[i].file = NULL;
 		nbd_dev[i].magic = LO_MAGIC;

@@ -706,8 +713,9 @@ out:
 static void __exit nbd_cleanup(void)
 {
 	int i;
-	for (i = 0; i < MAX_NBD; i++) {
+	for (i = 0; i < nbds_max; i++) {
 		struct gendisk *disk = nbd_dev[i].disk;
+		nbd_dev[i].magic = 0;
 		if (disk) {
 			del_gendisk(disk);
 			blk_cleanup_queue(disk->queue);

@@ -725,6 +733,8 @@ module_exit(nbd_cleanup);
 MODULE_DESCRIPTION("Network Block Device");
 MODULE_LICENSE("GPL");
 
+module_param(nbds_max, int, 16);
+MODULE_PARM_DESC(nbds_max, "How many network block devices to initialize.");
 #ifndef NDEBUG
 module_param(debugflags, int, 0644);
 MODULE_PARM_DESC(debugflags, "flags for controlling debug output");
Signature · 3 lines
High Availability & Clustering
SUSE Labs, Research and Development
SUSE LINUX Products GmbH - A Novell Business
#1 lore raw
Quoted 8 lines · Lars Marowsky-Bree

From: Lars Marowsky-Bree <[email protected]>

This patches adds the "nbds_max" parameter to the nbd kernel module, which limits the number of nbds allocated. Previously, always all 128 entries were allocated unconditionally, which used to waste resources and needlessly flood the hotplug system with events. (Defaults to 16 now.)

...

Quoted 2 lines

+module_param(nbds_max, int, 16);

This is permissions in sysfs (or 0 if no file is to be created).

Quoted 4 lines

+MODULE_PARM_DESC(nbds_max, "How many network block devices to initialize.");
#ifndef NDEBUG
module_param(debugflags, int, 0644); MODULE_PARM_DESC(debugflags, "flags for controlling debug output");

author
#2 lore raw
Quoted 1 line · Domen Puncer

This is permissions in sysfs (or 0 if no file is to be created).

Duh. Should have caught that. Try this one.

drivers/block/nbd.c +13 -3
Index: linux-2.6.11/drivers/block/nbd.c
===================================================================
@@ -78,6 +78,7 @@
 #define DBG_RX          0x0200
 #define DBG_TX          0x0400
 static unsigned int debugflags;
+static unsigned int nbds_max = 16;
 #endif /* NDEBUG */
 
 static struct nbd_device nbd_dev[MAX_NBD];

@@ -647,7 +648,13 @@ static int __init nbd_init(void)
 		return -EIO;
 	}
 
-	for (i = 0; i < MAX_NBD; i++) {
+	if (nbds_max > MAX_NBD) {
+		printk(KERN_CRIT "nbd: cannot allocate more than %u nbds; %u requested.\n", MAX_NBD,
+				nbds_max);
+		return -EINVAL;
+	}
+
+	for (i = 0; i < nbds_max; i++) {
 		struct gendisk *disk = alloc_disk(1);
 		if (!disk)
 			goto out;

@@ -673,7 +680,7 @@ static int __init nbd_init(void)
 	dprintk(DBG_INIT, "nbd: debugflags=0x%x\n", debugflags);
 
 	devfs_mk_dir("nbd");
-	for (i = 0; i < MAX_NBD; i++) {
+	for (i = 0; i < nbds_max; i++) {
 		struct gendisk *disk = nbd_dev[i].disk;
 		nbd_dev[i].file = NULL;
 		nbd_dev[i].magic = LO_MAGIC;

@@ -706,8 +713,9 @@ out:
 static void __exit nbd_cleanup(void)
 {
 	int i;
-	for (i = 0; i < MAX_NBD; i++) {
+	for (i = 0; i < nbds_max; i++) {
 		struct gendisk *disk = nbd_dev[i].disk;
+		nbd_dev[i].magic = 0;
 		if (disk) {
 			del_gendisk(disk);
 			blk_cleanup_queue(disk->queue);

@@ -725,6 +733,8 @@ module_exit(nbd_cleanup);
 MODULE_DESCRIPTION("Network Block Device");
 MODULE_LICENSE("GPL");
 
+module_param(nbds_max, int, 0444);
+MODULE_PARM_DESC(nbds_max, "How many network block devices to initialize.");
 #ifndef NDEBUG
 module_param(debugflags, int, 0644);
 MODULE_PARM_DESC(debugflags, "flags for controlling debug output");

Sincerely,
Lars Marowsky-Brée <[email protected]>

Signature · 3 lines
High Availability & Clustering
SUSE Labs, Research and Development
SUSE LINUX Products GmbH - A Novell Business