Commit e467cde2 authored by Rusty Russell's avatar Rusty Russell
Browse files

Block driver using virtio. 



The block driver uses scatter-gather lists with sg[0] being the
request information (struct virtio_blk_outhdr) with the type, sector
and inbuf id.  The next N sg entries are the bio itself, then the last
sg is the status byte.  Whether the N entries are in or out depends on
whether it's a read or a write.

We accept the normal (SCSI) ioctls: they get handed through to the other
side which can then handle it or reply that it's unsupported.  It's
not clear that this actually works in general, since I don't know
if blk_pc_request() requests have an accurate rq_data_dir().

Although we try to reply -ENOTTY on unsupported commands, ioctl(fd,
CDROMEJECT) returns success to userspace.  This needs a separate
patch.

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Cc: Jens Axboe <jens.axboe@oracle.com>
parent 296f96fc

drivers/block/Kconfig

+6 −0
Original line number Diff line number Diff line
@@ -425,4 +425,10 @@ config XEN_BLKDEV_FRONTEND 
	  block device driver.  It communicates with a back-end driver

	  in another domain which drives the actual block device.



config VIRTIO_BLK

	tristate "Virtio block driver (EXPERIMENTAL)"

	depends on EXPERIMENTAL && VIRTIO

	---help---

	  This is the virtual block driver for lguest.  Say Y or M.



endif # BLK_DEV

drivers/block/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -25,6 +25,7 @@ obj-$(CONFIG_SUNVDC) += sunvdc.o 
obj-$(CONFIG_BLK_DEV_UMEM)	+= umem.o

obj-$(CONFIG_BLK_DEV_NBD)	+= nbd.o

obj-$(CONFIG_BLK_DEV_CRYPTOLOOP) += cryptoloop.o

obj-$(CONFIG_VIRTIO_BLK)	+= virtio_blk.o



obj-$(CONFIG_VIODASD)		+= viodasd.o

obj-$(CONFIG_BLK_DEV_SX8)	+= sx8.o

drivers/block/virtio_blk.c

0 → 100644
+308 −0
Original line number Diff line number Diff line 
//#define DEBUG

#include <linux/spinlock.h>

#include <linux/blkdev.h>

#include <linux/hdreg.h>

#include <linux/virtio.h>

#include <linux/virtio_blk.h>

#include <linux/virtio_blk.h>



static unsigned char virtblk_index = 'a';

struct virtio_blk

{

	spinlock_t lock;



	struct virtio_device *vdev;

	struct virtqueue *vq;



	/* The disk structure for the kernel. */

	struct gendisk *disk;



	/* Request tracking. */

	struct list_head reqs;



	mempool_t *pool;



	/* Scatterlist: can be too big for stack. */

	struct scatterlist sg[3+MAX_PHYS_SEGMENTS];

};



struct virtblk_req

{

	struct list_head list;

	struct request *req;

	struct virtio_blk_outhdr out_hdr;

	struct virtio_blk_inhdr in_hdr;

};



static bool blk_done(struct virtqueue *vq)

{

	struct virtio_blk *vblk = vq->vdev->priv;

	struct virtblk_req *vbr;

	unsigned int len;

	unsigned long flags;



	spin_lock_irqsave(&vblk->lock, flags);

	while ((vbr = vblk->vq->vq_ops->get_buf(vblk->vq, &len)) != NULL) {

		int uptodate;

		switch (vbr->in_hdr.status) {

		case VIRTIO_BLK_S_OK:

			uptodate = 1;

			break;

		case VIRTIO_BLK_S_UNSUPP:

			uptodate = -ENOTTY;

			break;

		default:

			uptodate = 0;

			break;

		}



		end_dequeued_request(vbr->req, uptodate);

		list_del(&vbr->list);

		mempool_free(vbr, vblk->pool);

	}

	/* In case queue is stopped waiting for more buffers. */

	blk_start_queue(vblk->disk->queue);

	spin_unlock_irqrestore(&vblk->lock, flags);

	return true;

}



static bool do_req(struct request_queue *q, struct virtio_blk *vblk,

		   struct request *req)

{

	unsigned long num, out, in;

	struct virtblk_req *vbr;



	vbr = mempool_alloc(vblk->pool, GFP_ATOMIC);

	if (!vbr)

		/* When another request finishes we'll try again. */

		return false;



	vbr->req = req;

	if (blk_fs_request(vbr->req)) {

		vbr->out_hdr.type = 0;

		vbr->out_hdr.sector = vbr->req->sector;

		vbr->out_hdr.ioprio = vbr->req->ioprio;

	} else if (blk_pc_request(vbr->req)) {

		vbr->out_hdr.type = VIRTIO_BLK_T_SCSI_CMD;

		vbr->out_hdr.sector = 0;

		vbr->out_hdr.ioprio = vbr->req->ioprio;

	} else {

		/* We don't put anything else in the queue. */

		BUG();

	}



	if (blk_barrier_rq(vbr->req))

		vbr->out_hdr.type |= VIRTIO_BLK_T_BARRIER;



	/* We have to zero this, otherwise blk_rq_map_sg gets upset. */

	memset(vblk->sg, 0, sizeof(vblk->sg));

	sg_set_buf(&vblk->sg[0], &vbr->out_hdr, sizeof(vbr->out_hdr));

	num = blk_rq_map_sg(q, vbr->req, vblk->sg+1);

	sg_set_buf(&vblk->sg[num+1], &vbr->in_hdr, sizeof(vbr->in_hdr));



	if (rq_data_dir(vbr->req) == WRITE) {

		vbr->out_hdr.type |= VIRTIO_BLK_T_OUT;

		out = 1 + num;

		in = 1;

	} else {

		vbr->out_hdr.type |= VIRTIO_BLK_T_IN;

		out = 1;

		in = 1 + num;

	}



	if (vblk->vq->vq_ops->add_buf(vblk->vq, vblk->sg, out, in, vbr)) {

		mempool_free(vbr, vblk->pool);

		return false;

	}



	list_add_tail(&vbr->list, &vblk->reqs);

	return true;

}



static void do_virtblk_request(struct request_queue *q)

{

	struct virtio_blk *vblk = NULL;

	struct request *req;

	unsigned int issued = 0;



	while ((req = elv_next_request(q)) != NULL) {

		vblk = req->rq_disk->private_data;

		BUG_ON(req->nr_phys_segments > ARRAY_SIZE(vblk->sg));



		/* If this request fails, stop queue and wait for something to

		   finish to restart it. */

		if (!do_req(q, vblk, req)) {

			blk_stop_queue(q);

			break;

		}

		blkdev_dequeue_request(req);

		issued++;

	}



	if (issued)

		vblk->vq->vq_ops->kick(vblk->vq);

}



static int virtblk_ioctl(struct inode *inode, struct file *filp,

			 unsigned cmd, unsigned long data)

{

	return scsi_cmd_ioctl(filp, inode->i_bdev->bd_disk->queue,

			      inode->i_bdev->bd_disk, cmd,

			      (void __user *)data);

}



static struct block_device_operations virtblk_fops = {

	.ioctl = virtblk_ioctl,

	.owner = THIS_MODULE,

};



static int virtblk_probe(struct virtio_device *vdev)

{

	struct virtio_blk *vblk;

	int err, major;

	void *token;

	unsigned int len;

	u64 cap;

	u32 v;



	vdev->priv = vblk = kmalloc(sizeof(*vblk), GFP_KERNEL);

	if (!vblk) {

		err = -ENOMEM;

		goto out;

	}



	INIT_LIST_HEAD(&vblk->reqs);

	spin_lock_init(&vblk->lock);

	vblk->vdev = vdev;



	/* We expect one virtqueue, for output. */

	vblk->vq = vdev->config->find_vq(vdev, blk_done);

	if (IS_ERR(vblk->vq)) {

		err = PTR_ERR(vblk->vq);

		goto out_free_vblk;

	}



	vblk->pool = mempool_create_kmalloc_pool(1,sizeof(struct virtblk_req));

	if (!vblk->pool) {

		err = -ENOMEM;

		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);

	if (!vblk->disk) {

		err = -ENOMEM;

		goto out_unregister_blkdev;

	}



	vblk->disk->queue = blk_init_queue(do_virtblk_request, &vblk->lock);

	if (!vblk->disk->queue) {

		err = -ENOMEM;

		goto out_put_disk;

	}



	sprintf(vblk->disk->disk_name, "vd%c", virtblk_index++);

	vblk->disk->major = major;

	vblk->disk->first_minor = 0;

	vblk->disk->private_data = vblk;

	vblk->disk->fops = &virtblk_fops;



	/* If barriers are supported, tell block layer that queue is ordered */

	token = vdev->config->find(vdev, VIRTIO_CONFIG_BLK_F, &len);

	if (virtio_use_bit(vdev, token, len, VIRTIO_BLK_F_BARRIER))

		blk_queue_ordered(vblk->disk->queue, QUEUE_ORDERED_TAG, NULL);



	err = virtio_config_val(vdev, VIRTIO_CONFIG_BLK_F_CAPACITY, &cap);

	if (err) {

		dev_err(&vdev->dev, "Bad/missing capacity in config\n");

		goto out_put_disk;

	}



	/* If capacity is too big, truncate with warning. */

	if ((sector_t)cap != cap) {

		dev_warn(&vdev->dev, "Capacity %llu too large: truncating\n",

			 (unsigned long long)cap);

		cap = (sector_t)-1;

	}

	set_capacity(vblk->disk, cap);



	err = virtio_config_val(vdev, VIRTIO_CONFIG_BLK_F_SIZE_MAX, &v);

	if (!err)

		blk_queue_max_segment_size(vblk->disk->queue, v);

	else if (err != -ENOENT) {

		dev_err(&vdev->dev, "Bad SIZE_MAX in config\n");

		goto out_put_disk;

	}



	err = virtio_config_val(vdev, VIRTIO_CONFIG_BLK_F_SEG_MAX, &v);

	if (!err)

		blk_queue_max_hw_segments(vblk->disk->queue, v);

	else if (err != -ENOENT) {

		dev_err(&vdev->dev, "Bad SEG_MAX in config\n");

		goto out_put_disk;

	}



	add_disk(vblk->disk);

	return 0;



out_put_disk:

	put_disk(vblk->disk);

out_unregister_blkdev:

	unregister_blkdev(major, "virtblk");

out_mempool:

	mempool_destroy(vblk->pool);

out_free_vq:

	vdev->config->del_vq(vblk->vq);

out_free_vblk:

	kfree(vblk);

out:

	return err;

}



static void virtblk_remove(struct virtio_device *vdev)

{

	struct virtio_blk *vblk = vdev->priv;

	int major = vblk->disk->major;



	BUG_ON(!list_empty(&vblk->reqs));

	blk_cleanup_queue(vblk->disk->queue);

	put_disk(vblk->disk);

	unregister_blkdev(major, "virtblk");

	mempool_destroy(vblk->pool);

	kfree(vblk);

}



static struct virtio_device_id id_table[] = {

	{ VIRTIO_ID_BLOCK, VIRTIO_DEV_ANY_ID },

	{ 0 },

};



static struct virtio_driver virtio_blk = {

	.driver.name =	KBUILD_MODNAME,

	.driver.owner =	THIS_MODULE,

	.id_table =	id_table,

	.probe =	virtblk_probe,

	.remove =	__devexit_p(virtblk_remove),

};



static int __init init(void)

{

	return register_virtio_driver(&virtio_blk);

}



static void __exit fini(void)

{

	unregister_virtio_driver(&virtio_blk);

}

module_init(init);

module_exit(fini);



MODULE_DEVICE_TABLE(virtio, id_table);

MODULE_DESCRIPTION("Virtio block driver");

MODULE_LICENSE("GPL");

include/linux/Kbuild

+1 −0
Original line number Diff line number Diff line
@@ -344,6 +344,7 @@ unifdef-y += utsname.h 
unifdef-y += videodev2.h

unifdef-y += videodev.h

unifdef-y += virtio_config.h

unifdef-y += virtio_blk.h

unifdef-y += virtio_net.h

unifdef-y += wait.h

unifdef-y += wanrouter.h

include/linux/virtio_blk.h

0 → 100644
+51 −0
Original line number Diff line number Diff line 
#ifndef _LINUX_VIRTIO_BLK_H

#define _LINUX_VIRTIO_BLK_H

#include <linux/virtio_config.h>



/* The ID for virtio_block */

#define VIRTIO_ID_BLOCK	2



/* Feature bits */

#define VIRTIO_CONFIG_BLK_F	0x40

#define VIRTIO_BLK_F_BARRIER	1	/* Does host support barriers? */



/* The capacity (in 512-byte sectors). */

#define VIRTIO_CONFIG_BLK_F_CAPACITY	0x41

/* The maximum segment size. */

#define VIRTIO_CONFIG_BLK_F_SIZE_MAX	0x42

/* The maximum number of segments. */

#define VIRTIO_CONFIG_BLK_F_SEG_MAX	0x43



/* These two define direction. */

#define VIRTIO_BLK_T_IN		0

#define VIRTIO_BLK_T_OUT	1



/* This bit says it's a scsi command, not an actual read or write. */

#define VIRTIO_BLK_T_SCSI_CMD	2



/* Barrier before this op. */

#define VIRTIO_BLK_T_BARRIER	0x80000000



/* This is the first element of the read scatter-gather list. */

struct virtio_blk_outhdr

{

	/* VIRTIO_BLK_T* */

	__u32 type;

	/* io priority. */

	__u32 ioprio;

	/* Sector (ie. 512 byte offset) */

	__u64 sector;

	/* Where to put reply. */

	__u64 id;

};



#define VIRTIO_BLK_S_OK		0

#define VIRTIO_BLK_S_IOERR	1

#define VIRTIO_BLK_S_UNSUPP	2



/* This is the first element of the write scatter-gather list */

struct virtio_blk_inhdr

{

	unsigned char status;

};

#endif /* _LINUX_VIRTIO_BLK_H */

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