linux/net/9p/trans_virtio.c
Eric Van Hensbergen 91b8534fa8 9p: make rpc code common and rework flush code
This code moves the rpc function to the common client base,
reorganizes the flush code to be more simple and stable, and
makes the necessary adjustments to the underlying transports
to adapt to the new structure.

This reduces the overall amount of code duplication between the
transports and should make adding new transports more straightforward.

Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
2008-10-17 11:04:42 -05:00

390 lines
9.8 KiB
C

/*
* 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 <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);
/* global which tracks highest initialized channel */
static int chan_index;
/**
* 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
* @vdev: virtio dev associated with this channel
* @vq: virtio queue associated with this channel
* @tagpool: accounting for tag ids (and request slots)
* @reqs: array of request slots
* @max_tag: current number of request_slots allocated
* @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.
*
*/
static struct virtio_chan {
bool initialized;
bool inuse;
spinlock_t lock;
struct p9_client *client;
struct virtio_device *vdev;
struct virtqueue *vq;
/* Scatterlist: can be too big for stack. */
struct scatterlist sg[VIRTQUEUE_NUM];
} channels[MAX_9P_CHAN];
/* 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
* @trans: transport state
*
* 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);
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;
P9_DPRINTK(P9_DEBUG_TRANS, ": request done\n");
while ((rc = chan->vq->vq_ops->get_buf(chan->vq, &len)) != NULL) {
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);
p9_client_cb(chan->client, req);
}
}
/**
* 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
* @t: transport state
* @tc: &p9_fcall request to transmit
* @rc: &p9_fcall to put reponse into
*
*/
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);
P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio request\n");
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);
req->status = REQ_STATUS_SENT;
if (chan->vq->vq_ops->add_buf(chan->vq, chan->sg, out, in, req->tc)) {
P9_DPRINTK(P9_DEBUG_TRANS,
"9p debug: virtio rpc add_buf returned failure");
return -EIO;
}
chan->vq->vq_ops->kick(chan->vq);
P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio request kicked\n");
return 0;
}
/**
* p9_virtio_probe - probe for existence of 9P virtio channels
* @vdev: virtio device to probe
*
* This probes for existing virtio channels. At present only
* a single channel is in use, so in the future more work may need
* to be done here.
*
*/
static int p9_virtio_probe(struct virtio_device *vdev)
{
int err;
struct virtio_chan *chan;
int index;
mutex_lock(&virtio_9p_lock);
index = chan_index++;
chan = &channels[index];
mutex_unlock(&virtio_9p_lock);
if (chan_index > MAX_9P_CHAN) {
printk(KERN_ERR "9p: virtio: Maximum channels exceeded\n");
BUG();
err = -ENOMEM;
goto fail;
}
chan->vdev = vdev;
/* We expect one virtqueue, for requests. */
chan->vq = vdev->config->find_vq(vdev, 0, req_done);
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;
chan->initialized = true;
return 0;
out_free_vq:
vdev->config->del_vq(chan->vq);
fail:
mutex_lock(&virtio_9p_lock);
chan_index--;
mutex_unlock(&virtio_9p_lock);
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.
*
* Bugs: doesn't allow identification of a specific channel
* to allocate, channels are allocated sequentially. This was
* a pragmatic decision to get things rolling, but ideally some
* way of identifying the channel to attach to would be nice
* if we are going to support multiple channels.
*
*/
static int
p9_virtio_create(struct p9_client *client, const char *devname, char *args)
{
struct virtio_chan *chan = channels;
int index = 0;
mutex_lock(&virtio_9p_lock);
while (index < MAX_9P_CHAN) {
if (chan->initialized && !chan->inuse) {
chan->inuse = true;
break;
} else {
index++;
chan = &channels[index];
}
}
mutex_unlock(&virtio_9p_lock);
if (index >= MAX_9P_CHAN) {
printk(KERN_ERR "9p: no channels available\n");
return -ENODEV;
}
client->trans = (void *)chan;
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);
if (chan->initialized) {
vdev->config->del_vq(chan->vq);
chan->initialized = false;
}
}
#define VIRTIO_ID_9P 9
static struct virtio_device_id id_table[] = {
{ VIRTIO_ID_9P, VIRTIO_DEV_ANY_ID },
{ 0 },
};
/* The standard "struct lguest_driver": */
static struct virtio_driver p9_virtio_drv = {
.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)
{
int count;
for (count = 0; count < MAX_9P_CHAN; count++)
channels[count].initialized = false;
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");