The pseudo disk driver that I used to stress the kernel I/O stack
(anything above block layer, AIO/DIO/BIO).
- Ken
diff -Nur zero/blknull.c blknull/blknull.c
--- zero/blknull.c 1969-12-31 16:00:00.000000000 -0800
+++ blknull/blknull.c 2005-03-03 19:04:07.000000000 -0800
@@ -0,0 +1,97 @@
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/major.h>
+#include <linux/fs.h>
+#include <linux/bio.h>
+#include <linux/blkpg.h>
+#include <linux/spinlock.h>
+
+#include <linux/blkdev.h>
+#include <linux/genhd.h>
+
+#define BLK_NULL_MAJOR 60
+#define BLK_NULL_NAME "blknull"
+
+
+MODULE_AUTHOR("Ken Chen");
+MODULE_DESCRIPTION("null block driver");
+MODULE_LICENSE("GPL");
+
+
+spinlock_t driver_lock;
+struct request_queue *q;
+struct gendisk *disk;
+
+
+static int null_open(struct inode *inode, struct file *filp)
+{
+ return 0;
+}
+
+static int null_release(struct inode *inode, struct file *filp)
+{
+ return 0;
+}
+
+static struct block_device_operations null_fops = {
+ .owner = THIS_MODULE,
+ .open = null_open,
+ .release = null_release,
+};
+
+static void do_null_request(request_queue_t *q)
+{
+ struct request *req;
+
+ while (!blk_queue_plugged(q)) {
+ req = elv_next_request(q);
+ if (!req)
+ break;
+
+ blkdev_dequeue_request(req);
+
+ end_that_request_first(req, 1, req->nr_sectors);
+ end_that_request_last(req);
+ }
+}
+
+static int __init init_blk_null_module(void)
+{
+
+ if (register_blkdev(BLK_NULL_MAJOR, BLK_NULL_NAME)) {
+ printk(KERN_ERR "Unable to register null blk device\n");
+ return 0;
+ }
+
+ spin_lock_init(&driver_lock);
+ q = blk_init_queue(do_null_request, &driver_lock);
+ if (q) {
+ disk = alloc_disk(1);
+
+ if (disk) {
+ disk->major = BLK_NULL_MAJOR;
+ disk->first_minor = 0;
+ disk->fops = &null_fops;
+ disk->capacity = 1<<30;
+ disk->queue = q;
+ memcpy(disk->disk_name, BLK_NULL_NAME,
sizeof(BLK_NULL_NAME));
+ add_disk(disk);
+ return 1;
+ }
+
+ blk_cleanup_queue(q);
+ }
+ unregister_blkdev(BLK_NULL_MAJOR, BLK_NULL_NAME);
+ return 0;
+}
+
+static void __exit exit_blk_null_module(void)
+{
+ del_gendisk(disk);
+ blk_cleanup_queue(q);
+ unregister_blkdev(BLK_NULL_MAJOR, BLK_NULL_NAME);
+}
+
+module_init(init_blk_null_module);
+module_exit(exit_blk_null_module);
diff -Nur zero/Makefile blknull/Makefile
--- zero/Makefile 1969-12-31 16:00:00.000000000 -0800
+++ blknull/Makefile 2005-03-03 18:42:55.000000000 -0800
@@ -0,0 +1 @@
+obj-m := blknull.o
-
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