Rusty,
currently virtio_blk uses one major number per device. While this works
quite well on most systems it is wasteful and will exhaust major numbers
on larger installations.
This patch allocates a major number on init and will use 16 minor numbers
for each disk. That will allow ~64k virtio_blk disks.
Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
---
drivers/block/virtio_blk.c | 28 ++++++++++++++++------------
1 file changed, 16 insertions(+), 12 deletions(-)
Index: kvm/drivers/block/virtio_blk.c
===================================================================
--- kvm.orig/drivers/block/virtio_blk.c
+++ kvm/drivers/block/virtio_blk.c
@@ -7,10 +7,13 @@
#include <linux/scatterlist.h>
#define VIRTIO_MAX_SG (3+MAX_PHYS_SEGMENTS)
+#define PART_BITS 4
MODULE_LICENSE("GPL");
static unsigned char virtblk_index = 'a';
+static int major, minor;
+
struct virtio_blk
{
spinlock_t lock;
@@ -173,10 +176,13 @@ static struct block_device_operations vi
static int virtblk_probe(struct virtio_device *vdev)
{
struct virtio_blk *vblk;
- int err, major;
+ int err;
u64 cap;
u32 v;
+ if (minor >= 1 << MINORBITS)
+ return -ENOSPC;
+
vdev->priv = vblk = kmalloc(sizeof(*vblk), GFP_KERNEL);
if (!vblk) {
err = -ENOMEM;
@@ -200,17 +206,11 @@ static int virtblk_probe(struct virtio_d
goto out_free_vq;
}
- major = register_blkdev(0, "virtblk");
- if (major < 0) {
- err = major;
- goto out_mempool;
- }
-
/* FIXME: How many partitions? How long is a piece of string? */
- vblk->disk = alloc_disk(1 << 4);
+ vblk->disk = alloc_disk(1 << PART_BITS);
if (!vblk->disk) {
err = -ENOMEM;
- goto out_unregister_blkdev;
+ goto out_mempool;
}
vblk->disk->queue = blk_init_queue(do_virtblk_request, &vblk->lock);
@@ -221,10 +221,12 @@ static int virtblk_probe(struct virtio_d
sprintf(vblk->disk->disk_name, "vd%c", virtblk_index++);
vblk->disk->major = major;
- vblk->disk->first_minor = 0;
+ vblk->disk->first_minor = minor;
vblk->disk->private_data = vblk;
vblk->disk->fops = &virtblk_fops;
+ minor += 1 << PART_BITS;
+
/* If barriers are supported, tell block layer that queue is ordered */
if (vdev->config->feature(vdev, VIRTIO_BLK_F_BARRIER))
blk_queue_ordered(vblk->disk->queue, QUEUE_ORDERED_TAG, NULL);
@@ -260,8 +262,6 @@ static int virtblk_probe(struct virtio_d
out_put_disk:
put_disk(vblk->disk);
-out_unregister_blkdev:
- unregister_blkdev(major, "virtblk");
out_mempool:
mempool_destroy(vblk->pool);
out_free_vq:
@@ -302,11 +302,15 @@ static struct virtio_driver virtio_blk =
static int __init init(void)
{
+ major = register_blkdev(0, "virtblk");
+ if (major < 0)
+ return major;
return register_virtio_driver(&virtio_blk);
}
static void __exit fini(void)
{
+ unregister_blkdev(major, "virtblk");
unregister_virtio_driver(&virtio_blk);
}
module_init(init);
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