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Commit 4f3bf19c authored by Christian Borntraeger's avatar Christian Borntraeger Committed by Rusty Russell
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virtio_blk: Dont waste major numbers 



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: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent 135da0b0

drivers/block/virtio_blk.c

+16 −12
Original line number Diff line number Diff line
@@ -7,8 +7,11 @@ 
#include <linux/scatterlist.h>



#define VIRTIO_MAX_SG	(3+MAX_PHYS_SEGMENTS)

#define PART_BITS 4



static unsigned char virtblk_index = 'a';

static int major, minor;



struct virtio_blk

{

	spinlock_t lock;
@@ -171,10 +174,13 @@ static struct block_device_operations virtblk_fops = { 
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;
@@ -198,17 +204,11 @@ static int virtblk_probe(struct virtio_device *vdev) 
		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);
@@ -219,10 +219,12 @@ static int virtblk_probe(struct virtio_device *vdev) 


	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);
@@ -258,8 +260,6 @@ static int virtblk_probe(struct virtio_device *vdev) 


out_put_disk:

	put_disk(vblk->disk);

out_unregister_blkdev:

	unregister_blkdev(major, "virtblk");

out_mempool:

	mempool_destroy(vblk->pool);

out_free_vq:
@@ -304,11 +304,15 @@ 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);