[PATCH 4/4] brd: add miscdevice to control creation and deletion of ram disks
From: Hannes Frederic Sowa
Date: Sat Oct 20 2012 - 14:32:33 EST
This patch adds the miscdevice /dev/brd-control with two ioctls:
1) BRD_CTL_ADD: Instantiates a new ram disk with a given size as
parameter. This parameter is filled in with the new minor id
on return.
2) BRD_CTL_DEL: Deletes a ram disk. Takes the minor id as parameter.
Cc: Nick Piggin <npiggin@xxxxxxxxx>
Signed-off-by: Hannes Frederic Sowa <hannes@xxxxxxxxxxxxxxxxxxx>
---
Documentation/ioctl/ioctl-number.txt | 1 +
drivers/block/brd.c | 170 ++++++++++++++++++++++++++++++++---
include/linux/Kbuild | 1 +
include/linux/brd.h | 12 +++
include/linux/miscdevice.h | 1 +
5 files changed, 173 insertions(+), 12 deletions(-)
create mode 100644 include/linux/brd.h
diff --git a/Documentation/ioctl/ioctl-number.txt b/Documentation/ioctl/ioctl-number.txt
index 849b771..b8827eb 100644
--- a/Documentation/ioctl/ioctl-number.txt
+++ b/Documentation/ioctl/ioctl-number.txt
@@ -326,4 +326,5 @@ Code Seq#(hex) Include File Comments
<mailto:raph@xxxxxx>
0xF6 all LTTng Linux Trace Toolkit Next Generation
<mailto:mathieu.desnoyers@xxxxxxxxxxxx>
+0xF7 00-01 drivers/block/brd.c block ram device control driver
0xFD all linux/dm-ioctl.h
diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index 1d0016b..5ad25af 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -20,6 +20,9 @@
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/idr.h>
+#include <linux/kernel.h>
+#include <linux/miscdevice.h>
+#include <linux/brd.h>
#include <asm/uaccess.h>
@@ -478,7 +481,7 @@ __setup("ramdisk_size=", ramdisk_size);
*/
static DEFINE_MUTEX(brd_devices_mutex);
-static struct brd_device *brd_alloc(int i)
+static struct brd_device *brd_alloc(int i, unsigned int size_kb)
{
struct brd_device *brd;
struct gendisk *disk;
@@ -511,7 +514,7 @@ static struct brd_device *brd_alloc(int i)
disk->queue = brd->brd_queue;
disk->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO;
sprintf(disk->disk_name, "ram%d", i);
- set_capacity(disk, rd_size * 2);
+ set_capacity(disk, size_kb * 2);
return brd;
@@ -584,7 +587,7 @@ static struct brd_device *brd_new(int id)
err = brd_new_specific_id(id);
if (err < 0)
return ERR_PTR(err);
- brd = brd_alloc(id);
+ brd = brd_alloc(id, rd_size);
if (!brd) {
p = ERR_PTR(-ENOMEM);
goto out;
@@ -605,6 +608,139 @@ out:
return p;
}
+static int brd_control_add(unsigned int size_kb)
+{
+ int val, err;
+ struct brd_device *brd, *p;
+
+ lockdep_assert_held(&brd_devices_mutex);
+
+ val = brd_new_id(0);
+ if (val < 0)
+ return val;
+ if (val >= (MINORMASK >> part_shift)) {
+ err = -EINVAL;
+ goto out;
+ }
+ brd = brd_alloc(val, size_kb);
+ if (!brd) {
+ err = -ENOMEM;
+ goto out;
+ }
+ p = idr_replace(&brd_idr, brd, val);
+ if (IS_ERR(p)) {
+ err = PTR_ERR(p);
+ goto out2;
+ }
+ if (p != DUMMY) {
+ WARN_ON(1);
+ err = -EBUSY;
+ goto out2;
+ }
+ add_disk(brd->brd_disk);
+ return val;
+out2:
+ brd_free(brd);
+out:
+ idr_remove(&brd_idr, val);
+ return err;
+}
+
+static int brd_control_del(unsigned int val)
+{
+ int err = 0;
+ struct brd_device *brd;
+ struct block_device *bdev;
+
+ lockdep_assert_held(&brd_devices_mutex);
+
+ brd = idr_find(&brd_idr, val);
+ if (!brd)
+ return -ENODEV;
+
+ mutex_lock(&brd_mutex);
+ bdev = bdget_disk(brd->brd_disk, 0);
+ if (!bdev) {
+ err = -ENODEV;
+ goto out;
+ }
+ mutex_lock(&bdev->bd_mutex);
+ err = brd_blkdev_in_use(bdev);
+ if (err) {
+ err = -EBUSY;
+ } else {
+ idr_remove(&brd_idr, val);
+ brd_del_one(brd);
+ err = 0;
+ }
+ mutex_unlock(&bdev->bd_mutex);
+out:
+ mutex_unlock(&brd_mutex);
+ return err;
+}
+
+static long brd_control_ioctl(struct file *file, unsigned int cmd,
+ unsigned long param)
+{
+ int err = -ENOSYS;
+ int val;
+ unsigned int size_kb;
+
+ if (rd_nr)
+ return -EINVAL;
+
+ mutex_lock(&brd_devices_mutex);
+ switch (cmd) {
+ case BRD_CTL_ADD:
+ err = get_user(size_kb, (unsigned int __user *)param);
+ if (err < 0)
+ break;
+ val = brd_control_add(size_kb);
+ if (val < 0) {
+ err = val;
+ break;
+ }
+ err = put_user(val << part_shift, (unsigned int __user *)param);
+ if (err < 0) {
+ brd_control_del(val);
+ break;
+ }
+ err = 0;
+ break;
+ case BRD_CTL_DEL:
+ err = get_user(val, (unsigned int __user *)param);
+ if (err < 0)
+ break;
+ if ((val & max_part) != 0) {
+ err = -EINVAL;
+ break;
+ }
+ val >>= part_shift;
+ err = brd_control_del(val);
+ break;
+ }
+ mutex_unlock(&brd_devices_mutex);
+ return err;
+}
+
+static const struct file_operations brd_ctl_fops = {
+ .open = nonseekable_open,
+ .unlocked_ioctl = brd_control_ioctl,
+ .owner = THIS_MODULE,
+ .llseek = noop_llseek,
+#ifdef CONFIG_COMPAT
+ .compat_ioctl = brd_control_ioctl,
+#endif
+};
+
+static struct miscdevice brd_misc = {
+ .minor = BRD_CTRL_MINOR,
+ .name = "brd-control",
+ .fops = &brd_ctl_fops,
+};
+MODULE_ALIAS_MISCDEV(BRD_CTRL_MINOR);
+MODULE_ALIAS("devname:brd-control");
+
static int brd_add_disk_idr(int id, void *p, void *data)
{
struct brd_device *brd = (struct brd_device *)p;
@@ -691,14 +827,21 @@ static int __init brd_init(void)
range = 1UL << MINORBITS;
}
- if (register_blkdev(RAMDISK_MAJOR, "ramdisk"))
- return -EIO;
+ err = misc_register(&brd_misc);
+ if (err)
+ return err;
+
+ err = register_blkdev(RAMDISK_MAJOR, "ramdisk");
+ if (err) {
+ err = -EIO;
+ goto out;
+ }
for (i = 0; i < nr; i++) {
brd = brd_new(i);
if (IS_ERR(brd)) {
err = PTR_RET(brd);
- goto out_free;
+ goto out2;
}
}
@@ -712,13 +855,15 @@ static int __init brd_init(void)
printk(KERN_INFO "brd: module loaded\n");
return 0;
-out_free:
+out2:
+ unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
+out:
+ misc_deregister(&brd_misc);
+
idr_for_each(&brd_idr, brd_free_idr, NULL);
idr_remove_all(&brd_idr);
idr_destroy(&brd_idr);
- unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
-
return err;
}
@@ -728,12 +873,13 @@ static void __exit brd_exit(void)
range = rd_nr ? rd_nr << part_shift : 1UL << MINORBITS;
+ blk_unregister_region(MKDEV(RAMDISK_MAJOR, 0), range);
+ unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
+ misc_deregister(&brd_misc);
+
idr_for_each(&brd_idr, brd_del_one_idr, NULL);
idr_remove_all(&brd_idr);
idr_destroy(&brd_idr);
-
- blk_unregister_region(MKDEV(RAMDISK_MAJOR, 0), range);
- unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
}
module_init(brd_init);
diff --git a/include/linux/Kbuild b/include/linux/Kbuild
index fa21760..05b0d3f 100644
--- a/include/linux/Kbuild
+++ b/include/linux/Kbuild
@@ -78,6 +78,7 @@ header-y += blk_types.h
header-y += blkpg.h
header-y += blktrace_api.h
header-y += bpqether.h
+header-y += brd.h
header-y += bsg.h
header-y += can.h
header-y += capability.h
diff --git a/include/linux/brd.h b/include/linux/brd.h
new file mode 100644
index 0000000..8a789136
--- /dev/null
+++ b/include/linux/brd.h
@@ -0,0 +1,12 @@
+#ifndef __LINUX_BRD_H__
+#define __LINUX_BRD_H__
+
+#include <linux/ioctl.h>
+
+#define BRD_CTL_IOCTL_MAGIC 0xF7
+
+/* /dev/brd-control ioctl commands */
+#define BRD_CTL_ADD _IOWR(BRD_CTL_IOCTL_MAGIC, 0, unsigned int)
+#define BRD_CTL_DEL _IOR(BRD_CTL_IOCTL_MAGIC, 1, unsigned int)
+
+#endif /* __LINUX_BRD_H__ */
diff --git a/include/linux/miscdevice.h b/include/linux/miscdevice.h
index e0deeb2..45df076 100644
--- a/include/linux/miscdevice.h
+++ b/include/linux/miscdevice.h
@@ -44,6 +44,7 @@
#define MAPPER_CTRL_MINOR 236
#define LOOP_CTRL_MINOR 237
#define VHOST_NET_MINOR 238
+#define BRD_CTRL_MINOR 239
#define MISC_DYNAMIC_MINOR 255
struct device;
--
1.7.12.4
--
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