net/9p/trans_virtio.c - kernel/msm-4.9 - Gitiles

 /*
  * The Virtio 9p transport driver
  *
  * This is a block based transport driver based on the lguest block driver
  * code.
  *
  *  Copyright (C) 2007, 2008 Eric Van Hensbergen, IBM Corporation
  *
  *  Based on virtio console driver
  *  Copyright (C) 2006, 2007 Rusty Russell, IBM Corporation
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License version 2
  *  as published by the Free Software Foundation.
  *
  *  This program is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  *  GNU General Public License for more details.
  *
  *  You should have received a copy of the GNU General Public License
  *  along with this program; if not, write to:
  *  Free Software Foundation
  *  51 Franklin Street, Fifth Floor
  *  Boston, MA  02111-1301  USA
  *
  */

 #include <linux/in.h>
 #include <linux/module.h>
 #include <linux/net.h>
 #include <linux/ipv6.h>
 #include <linux/errno.h>
 #include <linux/kernel.h>
 #include <linux/un.h>
 #include <linux/uaccess.h>
 #include <linux/inet.h>
 #include <linux/idr.h>
 #include <linux/file.h>
 #include <linux/slab.h>
 #include <net/9p/9p.h>
 #include <linux/parser.h>
 #include <net/9p/client.h>
 #include <net/9p/transport.h>
 #include <linux/scatterlist.h>
 #include <linux/virtio.h>
 #include <linux/virtio_9p.h>

 #define VIRTQUEUE_NUM	128

 /* a single mutex to manage channel initialization and attachment */
 static DEFINE_MUTEX(virtio_9p_lock);

 /**
  * struct virtio_chan - per-instance transport information
  * @initialized: whether the channel is initialized
  * @inuse: whether the channel is in use
  * @lock: protects multiple elements within this structure
  * @client: client instance
  * @vdev: virtio dev associated with this channel
  * @vq: virtio queue associated with this channel
  * @sg: scatter gather list which is used to pack a request (protected?)
  *
  * We keep all per-channel information in a structure.
  * This structure is allocated within the devices dev->mem space.
  * A pointer to the structure will get put in the transport private.
  *
  */

 struct virtio_chan {
 	bool inuse;

 	spinlock_t lock;

 	struct p9_client *client;
 	struct virtio_device *vdev;
 	struct virtqueue *vq;
 	int ring_bufs_avail;
 	wait_queue_head_t *vc_wq;

 	/* Scatterlist: can be too big for stack. */
 	struct scatterlist sg[VIRTQUEUE_NUM];

 	int tag_len;
 	/*
 	 * tag name to identify a mount Non-null terminated
 	 */
 	char *tag;

 	struct list_head chan_list;
 };

 static struct list_head virtio_chan_list;

 /* How many bytes left in this page. */
 static unsigned int rest_of_page(void *data)
 {
 	return PAGE_SIZE - ((unsigned long)data % PAGE_SIZE);
 }

 /**
  * p9_virtio_close - reclaim resources of a channel
  * @client: client instance
  *
  * This reclaims a channel by freeing its resources and
  * reseting its inuse flag.
  *
  */

 static void p9_virtio_close(struct p9_client *client)
 {
 	struct virtio_chan *chan = client->trans;

 	mutex_lock(&virtio_9p_lock);
 	if (chan)
 		chan->inuse = false;
 	mutex_unlock(&virtio_9p_lock);
 }

 /**
  * req_done - callback which signals activity from the server
  * @vq: virtio queue activity was received on
  *
  * This notifies us that the server has triggered some activity
  * on the virtio channel - most likely a response to request we
  * sent.  Figure out which requests now have responses and wake up
  * those threads.
  *
  * Bugs: could do with some additional sanity checking, but appears to work.
  *
  */

 static void req_done(struct virtqueue *vq)
 {
 	struct virtio_chan *chan = vq->vdev->priv;
 	struct p9_fcall *rc;
 	unsigned int len;
 	struct p9_req_t *req;
 	unsigned long flags;

 	P9_DPRINTK(P9_DEBUG_TRANS, ": request done\n");

 	do {
 		spin_lock_irqsave(&chan->lock, flags);
 		rc = virtqueue_get_buf(chan->vq, &len);

 		if (rc != NULL) {
 			if (!chan->ring_bufs_avail) {
 				chan->ring_bufs_avail = 1;
 				wake_up(chan->vc_wq);
 			}
 			spin_unlock_irqrestore(&chan->lock, flags);
 			P9_DPRINTK(P9_DEBUG_TRANS, ": rc %p\n", rc);
 			P9_DPRINTK(P9_DEBUG_TRANS, ": lookup tag %d\n",
 					rc->tag);
 			req = p9_tag_lookup(chan->client, rc->tag);
 			req->status = REQ_STATUS_RCVD;
 			p9_client_cb(chan->client, req);
 		} else {
 			spin_unlock_irqrestore(&chan->lock, flags);
 		}
 	} while (rc != NULL);
 }

 /**
  * pack_sg_list - pack a scatter gather list from a linear buffer
  * @sg: scatter/gather list to pack into
  * @start: which segment of the sg_list to start at
  * @limit: maximum segment to pack data to
  * @data: data to pack into scatter/gather list
  * @count: amount of data to pack into the scatter/gather list
  *
  * sg_lists have multiple segments of various sizes.  This will pack
  * arbitrary data into an existing scatter gather list, segmenting the
  * data as necessary within constraints.
  *
  */

 static int
 pack_sg_list(struct scatterlist *sg, int start, int limit, char *data,
 								int count)
 {
 	int s;
 	int index = start;

 	while (count) {
 		s = rest_of_page(data);
 		if (s > count)
 			s = count;
 		sg_set_buf(&sg[index++], data, s);
 		count -= s;
 		data += s;
 		BUG_ON(index > limit);
 	}

 	return index-start;
 }

 /* We don't currently allow canceling of virtio requests */
 static int p9_virtio_cancel(struct p9_client *client, struct p9_req_t *req)
 {
 	return 1;
 }

 /**
  * p9_virtio_request - issue a request
  * @client: client instance issuing the request
  * @req: request to be issued
  *
  */

 static int
 p9_virtio_request(struct p9_client *client, struct p9_req_t *req)
 {
 	int in, out;
 	struct virtio_chan *chan = client->trans;
 	char *rdata = (char *)req->rc+sizeof(struct p9_fcall);
 	unsigned long flags;
 	int err;

 	P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio request\n");

 req_retry:
 	req->status = REQ_STATUS_SENT;

 	spin_lock_irqsave(&chan->lock, flags);
 	out = pack_sg_list(chan->sg, 0, VIRTQUEUE_NUM, req->tc->sdata,
 								req->tc->size);
 	in = pack_sg_list(chan->sg, out, VIRTQUEUE_NUM-out, rdata,
 								client->msize);

 	err = virtqueue_add_buf(chan->vq, chan->sg, out, in, req->tc);
 	if (err < 0) {
 		if (err == -ENOSPC) {
 			chan->ring_bufs_avail = 0;
 			spin_unlock_irqrestore(&chan->lock, flags);
 			err = wait_event_interruptible(*chan->vc_wq,
 							chan->ring_bufs_avail);
 			if (err  == -ERESTARTSYS)
 				return err;

 			P9_DPRINTK(P9_DEBUG_TRANS, "9p:Retry virtio request\n");
 			goto req_retry;
 		} else {
 			spin_unlock_irqrestore(&chan->lock, flags);
 			P9_DPRINTK(P9_DEBUG_TRANS,
 					"9p debug: "
 					"virtio rpc add_buf returned failure");
 			return -EIO;
 		}
 	}

 	virtqueue_kick(chan->vq);
 	spin_unlock_irqrestore(&chan->lock, flags);

 	P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio request kicked\n");
 	return 0;
 }

 static ssize_t p9_mount_tag_show(struct device *dev,
 				struct device_attribute *attr, char *buf)
 {
 	struct virtio_chan *chan;
 	struct virtio_device *vdev;

 	vdev = dev_to_virtio(dev);
 	chan = vdev->priv;

 	return snprintf(buf, chan->tag_len + 1, "%s", chan->tag);
 }

 static DEVICE_ATTR(mount_tag, 0444, p9_mount_tag_show, NULL);

 /**
  * p9_virtio_probe - probe for existence of 9P virtio channels
  * @vdev: virtio device to probe
  *
  * This probes for existing virtio channels.
  *
  */

 static int p9_virtio_probe(struct virtio_device *vdev)
 {
 	__u16 tag_len;
 	char *tag;
 	int err;
 	struct virtio_chan *chan;

 	chan = kmalloc(sizeof(struct virtio_chan), GFP_KERNEL);
 	if (!chan) {
 		printk(KERN_ERR "9p: Failed to allocate virtio 9P channel\n");
 		err = -ENOMEM;
 		goto fail;
 	}

 	chan->vdev = vdev;

 	/* We expect one virtqueue, for requests. */
 	chan->vq = virtio_find_single_vq(vdev, req_done, "requests");
 	if (IS_ERR(chan->vq)) {
 		err = PTR_ERR(chan->vq);
 		goto out_free_vq;
 	}
 	chan->vq->vdev->priv = chan;
 	spin_lock_init(&chan->lock);

 	sg_init_table(chan->sg, VIRTQUEUE_NUM);

 	chan->inuse = false;
 	if (virtio_has_feature(vdev, VIRTIO_9P_MOUNT_TAG)) {
 		vdev->config->get(vdev,
 				offsetof(struct virtio_9p_config, tag_len),
 				&tag_len, sizeof(tag_len));
 	} else {
 		err = -EINVAL;
 		goto out_free_vq;
 	}
 	tag = kmalloc(tag_len, GFP_KERNEL);
 	if (!tag) {
 		err = -ENOMEM;
 		goto out_free_vq;
 	}
 	vdev->config->get(vdev, offsetof(struct virtio_9p_config, tag),
 			tag, tag_len);
 	chan->tag = tag;
 	chan->tag_len = tag_len;
 	err = sysfs_create_file(&(vdev->dev.kobj), &dev_attr_mount_tag.attr);
 	if (err) {
 		goto out_free_tag;
 	}
 	chan->vc_wq = kmalloc(sizeof(wait_queue_head_t), GFP_KERNEL);
 	if (!chan->vc_wq) {
 		err = -ENOMEM;
 		goto out_free_tag;
 	}
 	init_waitqueue_head(chan->vc_wq);
 	chan->ring_bufs_avail = 1;

 	mutex_lock(&virtio_9p_lock);
 	list_add_tail(&chan->chan_list, &virtio_chan_list);
 	mutex_unlock(&virtio_9p_lock);
 	return 0;

 out_free_tag:
 	kfree(tag);
 out_free_vq:
 	vdev->config->del_vqs(vdev);
 	kfree(chan);
 fail:
 	return err;
 }


 /**
  * p9_virtio_create - allocate a new virtio channel
  * @client: client instance invoking this transport
  * @devname: string identifying the channel to connect to (unused)
  * @args: args passed from sys_mount() for per-transport options (unused)
  *
  * This sets up a transport channel for 9p communication.  Right now
  * we only match the first available channel, but eventually we couldlook up
  * alternate channels by matching devname versus a virtio_config entry.
  * We use a simple reference count mechanism to ensure that only a single
  * mount has a channel open at a time.
  *
  */

 static int
 p9_virtio_create(struct p9_client *client, const char *devname, char *args)
 {
 	struct virtio_chan *chan;
 	int ret = -ENOENT;
 	int found = 0;

 	mutex_lock(&virtio_9p_lock);
 	list_for_each_entry(chan, &virtio_chan_list, chan_list) {
 		if (!strncmp(devname, chan->tag, chan->tag_len) &&
 		    strlen(devname) == chan->tag_len) {
 			if (!chan->inuse) {
 				chan->inuse = true;
 				found = 1;
 				break;
 			}
 			ret = -EBUSY;
 		}
 	}
 	mutex_unlock(&virtio_9p_lock);

 	if (!found) {
 		printk(KERN_ERR "9p: no channels available\n");
 		return ret;
 	}

 	client->trans = (void *)chan;
 	client->status = Connected;
 	chan->client = client;

 	return 0;
 }

 /**
  * p9_virtio_remove - clean up resources associated with a virtio device
  * @vdev: virtio device to remove
  *
  */

 static void p9_virtio_remove(struct virtio_device *vdev)
 {
 	struct virtio_chan *chan = vdev->priv;

 	BUG_ON(chan->inuse);
 	vdev->config->del_vqs(vdev);

 	mutex_lock(&virtio_9p_lock);
 	list_del(&chan->chan_list);
 	mutex_unlock(&virtio_9p_lock);
 	sysfs_remove_file(&(vdev->dev.kobj), &dev_attr_mount_tag.attr);
 	kfree(chan->tag);
 	kfree(chan->vc_wq);
 	kfree(chan);

 }

 static struct virtio_device_id id_table[] = {
 	{ VIRTIO_ID_9P, VIRTIO_DEV_ANY_ID },
 	{ 0 },
 };

 static unsigned int features[] = {
 	VIRTIO_9P_MOUNT_TAG,
 };

 /* The standard "struct lguest_driver": */
 static struct virtio_driver p9_virtio_drv = {
 	.feature_table  = features,
 	.feature_table_size = ARRAY_SIZE(features),
 	.driver.name    = KBUILD_MODNAME,
 	.driver.owner	= THIS_MODULE,
 	.id_table	= id_table,
 	.probe		= p9_virtio_probe,
 	.remove		= p9_virtio_remove,
 };

 static struct p9_trans_module p9_virtio_trans = {
 	.name = "virtio",
 	.create = p9_virtio_create,
 	.close = p9_virtio_close,
 	.request = p9_virtio_request,
 	.cancel = p9_virtio_cancel,
 	.maxsize = PAGE_SIZE*16,
 	.def = 0,
 	.owner = THIS_MODULE,
 };

 /* The standard init function */
 static int __init p9_virtio_init(void)
 {
 	INIT_LIST_HEAD(&virtio_chan_list);

 	v9fs_register_trans(&p9_virtio_trans);
 	return register_virtio_driver(&p9_virtio_drv);
 }

 static void __exit p9_virtio_cleanup(void)
 {
 	unregister_virtio_driver(&p9_virtio_drv);
 	v9fs_unregister_trans(&p9_virtio_trans);
 }

 module_init(p9_virtio_init);
 module_exit(p9_virtio_cleanup);

 MODULE_DEVICE_TABLE(virtio, id_table);
 MODULE_AUTHOR("Eric Van Hensbergen <ericvh@gmail.com>");
 MODULE_DESCRIPTION("Virtio 9p Transport");
 MODULE_LICENSE("GPL");
	/*
	* The Virtio 9p transport driver
	*
	* This is a block based transport driver based on the lguest block driver
	* code.
	*
	* Copyright (C) 2007, 2008 Eric Van Hensbergen, IBM Corporation
	*
	* Based on virtio console driver
	* Copyright (C) 2006, 2007 Rusty Russell, IBM Corporation
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2
	* as published by the Free Software Foundation.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to:
	* Free Software Foundation
	* 51 Franklin Street, Fifth Floor
	* Boston, MA 02111-1301 USA
	*
	*/

	#include <linux/in.h>
	#include <linux/module.h>
	#include <linux/net.h>
	#include <linux/ipv6.h>
	#include <linux/errno.h>
	#include <linux/kernel.h>
	#include <linux/un.h>
	#include <linux/uaccess.h>
	#include <linux/inet.h>
	#include <linux/idr.h>
	#include <linux/file.h>
	#include <linux/slab.h>
	#include <net/9p/9p.h>
	#include <linux/parser.h>
	#include <net/9p/client.h>
	#include <net/9p/transport.h>
	#include <linux/scatterlist.h>
	#include <linux/virtio.h>
	#include <linux/virtio_9p.h>

	#define VIRTQUEUE_NUM 128

	/* a single mutex to manage channel initialization and attachment */
	static DEFINE_MUTEX(virtio_9p_lock);

	/**
	* struct virtio_chan - per-instance transport information
	* @initialized: whether the channel is initialized
	* @inuse: whether the channel is in use
	* @lock: protects multiple elements within this structure
	* @client: client instance
	* @vdev: virtio dev associated with this channel
	* @vq: virtio queue associated with this channel
	* @sg: scatter gather list which is used to pack a request (protected?)
	*
	* We keep all per-channel information in a structure.
	* This structure is allocated within the devices dev->mem space.
	* A pointer to the structure will get put in the transport private.
	*
	*/

	struct virtio_chan {
	bool inuse;

	spinlock_t lock;

	struct p9_client *client;
	struct virtio_device *vdev;
	struct virtqueue *vq;
	int ring_bufs_avail;
	wait_queue_head_t *vc_wq;

	/* Scatterlist: can be too big for stack. */
	struct scatterlist sg[VIRTQUEUE_NUM];

	int tag_len;
	/*
	* tag name to identify a mount Non-null terminated
	*/
	char *tag;

	struct list_head chan_list;
	};

	static struct list_head virtio_chan_list;

	/* How many bytes left in this page. */
	static unsigned int rest_of_page(void *data)
	{
	return PAGE_SIZE - ((unsigned long)data % PAGE_SIZE);
	}

	/**
	* p9_virtio_close - reclaim resources of a channel
	* @client: client instance
	*
	* This reclaims a channel by freeing its resources and
	* reseting its inuse flag.
	*
	*/

	static void p9_virtio_close(struct p9_client *client)
	{
	struct virtio_chan *chan = client->trans;

	mutex_lock(&virtio_9p_lock);
	if (chan)
	chan->inuse = false;
	mutex_unlock(&virtio_9p_lock);
	}

	/**
	* req_done - callback which signals activity from the server
	* @vq: virtio queue activity was received on
	*
	* This notifies us that the server has triggered some activity
	* on the virtio channel - most likely a response to request we
	* sent. Figure out which requests now have responses and wake up
	* those threads.
	*
	* Bugs: could do with some additional sanity checking, but appears to work.
	*
	*/

	static void req_done(struct virtqueue *vq)
	{
	struct virtio_chan *chan = vq->vdev->priv;
	struct p9_fcall *rc;
	unsigned int len;
	struct p9_req_t *req;
	unsigned long flags;

	P9_DPRINTK(P9_DEBUG_TRANS, ": request done\n");

	do {
	spin_lock_irqsave(&chan->lock, flags);
	rc = virtqueue_get_buf(chan->vq, &len);

	if (rc != NULL) {
	if (!chan->ring_bufs_avail) {
	chan->ring_bufs_avail = 1;
	wake_up(chan->vc_wq);
	}
	spin_unlock_irqrestore(&chan->lock, flags);
	P9_DPRINTK(P9_DEBUG_TRANS, ": rc %p\n", rc);
	P9_DPRINTK(P9_DEBUG_TRANS, ": lookup tag %d\n",
	rc->tag);
	req = p9_tag_lookup(chan->client, rc->tag);
	req->status = REQ_STATUS_RCVD;
	p9_client_cb(chan->client, req);
	} else {
	spin_unlock_irqrestore(&chan->lock, flags);
	}
	} while (rc != NULL);
	}

	/**
	* pack_sg_list - pack a scatter gather list from a linear buffer
	* @sg: scatter/gather list to pack into
	* @start: which segment of the sg_list to start at
	* @limit: maximum segment to pack data to
	* @data: data to pack into scatter/gather list
	* @count: amount of data to pack into the scatter/gather list
	*
	* sg_lists have multiple segments of various sizes. This will pack
	* arbitrary data into an existing scatter gather list, segmenting the
	* data as necessary within constraints.
	*
	*/

	static int
	pack_sg_list(struct scatterlist sg, int start, int limit, char data,
	int count)
	{
	int s;
	int index = start;

	while (count) {
	s = rest_of_page(data);
	if (s > count)
	s = count;
	sg_set_buf(&sg[index++], data, s);
	count -= s;
	data += s;
	BUG_ON(index > limit);
	}

	return index-start;
	}

	/* We don't currently allow canceling of virtio requests */
	static int p9_virtio_cancel(struct p9_client client, struct p9_req_t req)
	{
	return 1;
	}

	/**
	* p9_virtio_request - issue a request
	* @client: client instance issuing the request
	* @req: request to be issued
	*
	*/

	static int
	p9_virtio_request(struct p9_client client, struct p9_req_t req)
	{
	int in, out;
	struct virtio_chan *chan = client->trans;
	char rdata = (char )req->rc+sizeof(struct p9_fcall);
	unsigned long flags;
	int err;

	P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio request\n");

	req_retry:
	req->status = REQ_STATUS_SENT;

	spin_lock_irqsave(&chan->lock, flags);
	out = pack_sg_list(chan->sg, 0, VIRTQUEUE_NUM, req->tc->sdata,
	req->tc->size);
	in = pack_sg_list(chan->sg, out, VIRTQUEUE_NUM-out, rdata,
	client->msize);

	err = virtqueue_add_buf(chan->vq, chan->sg, out, in, req->tc);
	if (err < 0) {
	if (err == -ENOSPC) {
	chan->ring_bufs_avail = 0;
	spin_unlock_irqrestore(&chan->lock, flags);
	err = wait_event_interruptible(*chan->vc_wq,
	chan->ring_bufs_avail);
	if (err == -ERESTARTSYS)
	return err;

	P9_DPRINTK(P9_DEBUG_TRANS, "9p:Retry virtio request\n");
	goto req_retry;
	} else {
	spin_unlock_irqrestore(&chan->lock, flags);
	P9_DPRINTK(P9_DEBUG_TRANS,
	"9p debug: "
	"virtio rpc add_buf returned failure");
	return -EIO;
	}
	}

	virtqueue_kick(chan->vq);
	spin_unlock_irqrestore(&chan->lock, flags);

	P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio request kicked\n");
	return 0;
	}

	static ssize_t p9_mount_tag_show(struct device *dev,
	struct device_attribute attr, char buf)
	{
	struct virtio_chan *chan;
	struct virtio_device *vdev;

	vdev = dev_to_virtio(dev);
	chan = vdev->priv;

	return snprintf(buf, chan->tag_len + 1, "%s", chan->tag);
	}

	static DEVICE_ATTR(mount_tag, 0444, p9_mount_tag_show, NULL);

	/**
	* p9_virtio_probe - probe for existence of 9P virtio channels
	* @vdev: virtio device to probe
	*
	* This probes for existing virtio channels.
	*
	*/

	static int p9_virtio_probe(struct virtio_device *vdev)
	{
	__u16 tag_len;
	char *tag;
	int err;
	struct virtio_chan *chan;

	chan = kmalloc(sizeof(struct virtio_chan), GFP_KERNEL);
	if (!chan) {
	printk(KERN_ERR "9p: Failed to allocate virtio 9P channel\n");
	err = -ENOMEM;
	goto fail;
	}

	chan->vdev = vdev;

	/* We expect one virtqueue, for requests. */
	chan->vq = virtio_find_single_vq(vdev, req_done, "requests");
	if (IS_ERR(chan->vq)) {
	err = PTR_ERR(chan->vq);
	goto out_free_vq;
	}
	chan->vq->vdev->priv = chan;
	spin_lock_init(&chan->lock);

	sg_init_table(chan->sg, VIRTQUEUE_NUM);

	chan->inuse = false;
	if (virtio_has_feature(vdev, VIRTIO_9P_MOUNT_TAG)) {
	vdev->config->get(vdev,
	offsetof(struct virtio_9p_config, tag_len),
	&tag_len, sizeof(tag_len));
	} else {
	err = -EINVAL;
	goto out_free_vq;
	}
	tag = kmalloc(tag_len, GFP_KERNEL);
	if (!tag) {
	err = -ENOMEM;
	goto out_free_vq;
	}
	vdev->config->get(vdev, offsetof(struct virtio_9p_config, tag),
	tag, tag_len);
	chan->tag = tag;
	chan->tag_len = tag_len;
	err = sysfs_create_file(&(vdev->dev.kobj), &dev_attr_mount_tag.attr);
	if (err) {
	goto out_free_tag;
	}
	chan->vc_wq = kmalloc(sizeof(wait_queue_head_t), GFP_KERNEL);
	if (!chan->vc_wq) {
	err = -ENOMEM;
	goto out_free_tag;
	}
	init_waitqueue_head(chan->vc_wq);
	chan->ring_bufs_avail = 1;

	mutex_lock(&virtio_9p_lock);
	list_add_tail(&chan->chan_list, &virtio_chan_list);
	mutex_unlock(&virtio_9p_lock);
	return 0;

	out_free_tag:
	kfree(tag);
	out_free_vq:
	vdev->config->del_vqs(vdev);
	kfree(chan);
	fail:
	return err;
	}


	/**
	* p9_virtio_create - allocate a new virtio channel
	* @client: client instance invoking this transport
	* @devname: string identifying the channel to connect to (unused)
	* @args: args passed from sys_mount() for per-transport options (unused)
	*
	* This sets up a transport channel for 9p communication. Right now
	* we only match the first available channel, but eventually we couldlook up
	* alternate channels by matching devname versus a virtio_config entry.
	* We use a simple reference count mechanism to ensure that only a single
	* mount has a channel open at a time.
	*
	*/

	static int
	p9_virtio_create(struct p9_client client, const char devname, char *args)
	{
	struct virtio_chan *chan;
	int ret = -ENOENT;
	int found = 0;

	mutex_lock(&virtio_9p_lock);
	list_for_each_entry(chan, &virtio_chan_list, chan_list) {
	if (!strncmp(devname, chan->tag, chan->tag_len) &&
	strlen(devname) == chan->tag_len) {
	if (!chan->inuse) {
	chan->inuse = true;
	found = 1;
	break;
	}
	ret = -EBUSY;
	}
	}
	mutex_unlock(&virtio_9p_lock);

	if (!found) {
	printk(KERN_ERR "9p: no channels available\n");
	return ret;
	}

	client->trans = (void *)chan;
	client->status = Connected;
	chan->client = client;

	return 0;
	}

	/**
	* p9_virtio_remove - clean up resources associated with a virtio device
	* @vdev: virtio device to remove
	*
	*/

	static void p9_virtio_remove(struct virtio_device *vdev)
	{
	struct virtio_chan *chan = vdev->priv;

	BUG_ON(chan->inuse);
	vdev->config->del_vqs(vdev);

	mutex_lock(&virtio_9p_lock);
	list_del(&chan->chan_list);
	mutex_unlock(&virtio_9p_lock);
	sysfs_remove_file(&(vdev->dev.kobj), &dev_attr_mount_tag.attr);
	kfree(chan->tag);
	kfree(chan->vc_wq);
	kfree(chan);

	}

	static struct virtio_device_id id_table[] = {
	{ VIRTIO_ID_9P, VIRTIO_DEV_ANY_ID },
	{ 0 },
	};

	static unsigned int features[] = {
	VIRTIO_9P_MOUNT_TAG,
	};

	/* The standard "struct lguest_driver": */
	static struct virtio_driver p9_virtio_drv = {
	.feature_table = features,
	.feature_table_size = ARRAY_SIZE(features),
	.driver.name = KBUILD_MODNAME,
	.driver.owner = THIS_MODULE,
	.id_table = id_table,
	.probe = p9_virtio_probe,
	.remove = p9_virtio_remove,
	};

	static struct p9_trans_module p9_virtio_trans = {
	.name = "virtio",
	.create = p9_virtio_create,
	.close = p9_virtio_close,
	.request = p9_virtio_request,
	.cancel = p9_virtio_cancel,
	.maxsize = PAGE_SIZE*16,
	.def = 0,
	.owner = THIS_MODULE,
	};

	/* The standard init function */
	static int __init p9_virtio_init(void)
	{
	INIT_LIST_HEAD(&virtio_chan_list);

	v9fs_register_trans(&p9_virtio_trans);
	return register_virtio_driver(&p9_virtio_drv);
	}

	static void __exit p9_virtio_cleanup(void)
	{
	unregister_virtio_driver(&p9_virtio_drv);
	v9fs_unregister_trans(&p9_virtio_trans);
	}

	module_init(p9_virtio_init);
	module_exit(p9_virtio_cleanup);

	MODULE_DEVICE_TABLE(virtio, id_table);
	MODULE_AUTHOR("Eric Van Hensbergen <ericvh@gmail.com>");
	MODULE_DESCRIPTION("Virtio 9p Transport");
	MODULE_LICENSE("GPL");