Commit e467cde2 authored by Rusty Russell's avatar Rusty Russell

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
...@@ -425,4 +425,10 @@ config XEN_BLKDEV_FRONTEND ...@@ -425,4 +425,10 @@ config XEN_BLKDEV_FRONTEND
block device driver. It communicates with a back-end driver block device driver. It communicates with a back-end driver
in another domain which drives the actual block device. 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 endif # BLK_DEV
...@@ -25,6 +25,7 @@ obj-$(CONFIG_SUNVDC) += sunvdc.o ...@@ -25,6 +25,7 @@ obj-$(CONFIG_SUNVDC) += sunvdc.o
obj-$(CONFIG_BLK_DEV_UMEM) += umem.o obj-$(CONFIG_BLK_DEV_UMEM) += umem.o
obj-$(CONFIG_BLK_DEV_NBD) += nbd.o obj-$(CONFIG_BLK_DEV_NBD) += nbd.o
obj-$(CONFIG_BLK_DEV_CRYPTOLOOP) += cryptoloop.o obj-$(CONFIG_BLK_DEV_CRYPTOLOOP) += cryptoloop.o
obj-$(CONFIG_VIRTIO_BLK) += virtio_blk.o
obj-$(CONFIG_VIODASD) += viodasd.o obj-$(CONFIG_VIODASD) += viodasd.o
obj-$(CONFIG_BLK_DEV_SX8) += sx8.o obj-$(CONFIG_BLK_DEV_SX8) += sx8.o
......
//#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");
...@@ -344,6 +344,7 @@ unifdef-y += utsname.h ...@@ -344,6 +344,7 @@ unifdef-y += utsname.h
unifdef-y += videodev2.h unifdef-y += videodev2.h
unifdef-y += videodev.h unifdef-y += videodev.h
unifdef-y += virtio_config.h unifdef-y += virtio_config.h
unifdef-y += virtio_blk.h
unifdef-y += virtio_net.h unifdef-y += virtio_net.h
unifdef-y += wait.h unifdef-y += wait.h
unifdef-y += wanrouter.h unifdef-y += wanrouter.h
......
#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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