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DEFINITIONS
This source file includes following definitions.
- p9_lookup_tag
- rest_of_page
- p9_virtio_close
- req_done
- pack_sg_list
- p9_virtio_rpc
- p9_virtio_probe
- p9_virtio_create
- p9_virtio_remove
- p9_virtio_init
- p9_virtio_cleanup
/*
* The Guest 9p transport driver
*
* This is a block based transport driver based on the lguest block driver
* code.
*
*/
/*
* Copyright (C) 2007 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/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;
#define P9_INIT_MAXTAG 16
/**
* enum p9_req_status_t - virtio request status
* @REQ_STATUS_IDLE: request slot unused
* @REQ_STATUS_SENT: request sent to server
* @REQ_STATUS_RCVD: response received from server
* @REQ_STATUS_FLSH: request has been flushed
*
* The @REQ_STATUS_IDLE state is used to mark a request slot as unused
* but use is actually tracked by the idpool structure which handles tag
* id allocation.
*
*/
enum p9_req_status_t {
REQ_STATUS_IDLE,
REQ_STATUS_SENT,
REQ_STATUS_RCVD,
REQ_STATUS_FLSH,
};
/**
* struct p9_req_t - virtio request slots
* @status: status of this request slot
* @wq: wait_queue for the client to block on for this request
*
* The virtio transport uses an array to track outstanding requests
* instead of a list. While this may incurr overhead during initial
* allocation or expansion, it makes request lookup much easier as the
* tag id is a index into an array. (We use tag+1 so that we can accomodate
* the -1 tag for the T_VERSION request).
* This also has the nice effect of only having to allocate wait_queues
* once, instead of constantly allocating and freeing them. Its possible
* other resources could benefit from this scheme as well.
*
*/
struct p9_req_t {
int status;
wait_queue_head_t *wq;
};
/**
* 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 virtio_device *vdev;
struct virtqueue *vq;
struct p9_idpool *tagpool;
struct p9_req_t *reqs;
int max_tag;
/* Scatterlist: can be too big for stack. */
struct scatterlist sg[VIRTQUEUE_NUM];
} channels[MAX_9P_CHAN];
/**
* p9_lookup_tag - Lookup requests by tag
* @c: virtio channel to lookup tag within
* @tag: numeric id for transaction
*
* this is a simple array lookup, but will grow the
* request_slots as necessary to accomodate transaction
* ids which did not previously have a slot.
*
* Bugs: there is currently no upper limit on request slots set
* here, but that should be constrained by the id accounting.
*/
static struct p9_req_t *p9_lookup_tag(struct virtio_chan *c, u16 tag)
{
/* This looks up the original request by tag so we know which
* buffer to read the data into */
tag++;
while (tag >= c->max_tag) {
int old_max = c->max_tag;
int count;
if (c->max_tag)
c->max_tag *= 2;
else
c->max_tag = P9_INIT_MAXTAG;
c->reqs = krealloc(c->reqs, sizeof(struct p9_req_t)*c->max_tag,
GFP_ATOMIC);
if (!c->reqs) {
printk(KERN_ERR "Couldn't grow tag array\n");
BUG();
}
for (count = old_max; count < c->max_tag; count++) {
c->reqs[count].status = REQ_STATUS_IDLE;
c->reqs[count].wq = kmalloc(sizeof(wait_queue_head_t),
GFP_ATOMIC);
if (!c->reqs[count].wq) {
printk(KERN_ERR "Couldn't grow tag array\n");
BUG();
}
init_waitqueue_head(c->reqs[count].wq);
}
}
return &c->reqs[tag];
}
/* 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_trans *trans)
{
struct virtio_chan *chan = trans->priv;
int count;
unsigned long flags;
spin_lock_irqsave(&chan->lock, flags);
p9_idpool_destroy(chan->tagpool);
for (count = 0; count < chan->max_tag; count++)
kfree(chan->reqs[count].wq);
kfree(chan->reqs);
chan->max_tag = 0;
spin_unlock_irqrestore(&chan->lock, flags);
mutex_lock(&virtio_9p_lock);
chan->inuse = false;
mutex_unlock(&virtio_9p_lock);
kfree(trans);
}
/**
* 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;
unsigned long flags;
struct p9_req_t *req;
spin_lock_irqsave(&chan->lock, flags);
while ((rc = chan->vq->vq_ops->get_buf(chan->vq, &len)) != NULL) {
req = p9_lookup_tag(chan, rc->tag);
req->status = REQ_STATUS_RCVD;
wake_up(req->wq);
}
/* In case queue is stopped waiting for more buffers. */
spin_unlock_irqrestore(&chan->lock, flags);
}
/**
* 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;
}
/**
* p9_virtio_rpc - issue a request and wait for a response
* @t: transport state
* @tc: &p9_fcall request to transmit
* @rc: &p9_fcall to put reponse into
*
*/
static int
p9_virtio_rpc(struct p9_trans *t, struct p9_fcall *tc, struct p9_fcall **rc)
{
int in, out;
int n, err, size;
struct virtio_chan *chan = t->priv;
char *rdata;
struct p9_req_t *req;
unsigned long flags;
if (*rc == NULL) {
*rc = kmalloc(sizeof(struct p9_fcall) + t->msize, GFP_KERNEL);
if (!*rc)
return -ENOMEM;
}
rdata = (char *)*rc+sizeof(struct p9_fcall);
n = P9_NOTAG;
if (tc->id != P9_TVERSION) {
n = p9_idpool_get(chan->tagpool);
if (n < 0)
return -ENOMEM;
}
spin_lock_irqsave(&chan->lock, flags);
req = p9_lookup_tag(chan, n);
spin_unlock_irqrestore(&chan->lock, flags);
p9_set_tag(tc, n);
P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio rpc tag %d\n", n);
out = pack_sg_list(chan->sg, 0, VIRTQUEUE_NUM, tc->sdata, tc->size);
in = pack_sg_list(chan->sg, out, VIRTQUEUE_NUM-out, rdata, t->msize);
req->status = REQ_STATUS_SENT;
if (chan->vq->vq_ops->add_buf(chan->vq, chan->sg, out, in, tc)) {
P9_DPRINTK(P9_DEBUG_TRANS,
"9p debug: virtio rpc add_buf returned failure");
return -EIO;
}
chan->vq->vq_ops->kick(chan->vq);
wait_event(*req->wq, req->status == REQ_STATUS_RCVD);
size = le32_to_cpu(*(__le32 *) rdata);
err = p9_deserialize_fcall(rdata, size, *rc, t->extended);
if (err < 0) {
P9_DPRINTK(P9_DEBUG_TRANS,
"9p debug: virtio rpc deserialize returned %d\n", err);
return err;
}
#ifdef CONFIG_NET_9P_DEBUG
if ((p9_debug_level&P9_DEBUG_FCALL) == P9_DEBUG_FCALL) {
char buf[150];
p9_printfcall(buf, sizeof(buf), *rc, t->extended);
printk(KERN_NOTICE ">>> %p %s\n", t, buf);
}
#endif
if (n != P9_NOTAG && p9_idpool_check(n, chan->tagpool))
p9_idpool_put(n, chan->tagpool);
req->status = REQ_STATUS_IDLE;
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
* @devname: string identifying the channel to connect to (unused)
* @args: args passed from sys_mount() for per-transport options (unused)
* @msize: requested maximum packet size
* @extended: 9p2000.u enabled flag
*
* 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 struct p9_trans *
p9_virtio_create(const char *devname, char *args, int msize,
unsigned char extended)
{
struct p9_trans *trans;
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 ERR_PTR(-ENODEV);
}
chan->tagpool = p9_idpool_create();
if (IS_ERR(chan->tagpool)) {
printk(KERN_ERR "9p: couldn't allocate tagpool\n");
return ERR_PTR(-ENOMEM);
}
p9_idpool_get(chan->tagpool); /* reserve tag 0 */
chan->max_tag = 0;
chan->reqs = NULL;
trans = kmalloc(sizeof(struct p9_trans), GFP_KERNEL);
if (!trans) {
printk(KERN_ERR "9p: couldn't allocate transport\n");
return ERR_PTR(-ENOMEM);
}
trans->extended = extended;
trans->msize = msize;
trans->close = p9_virtio_close;
trans->rpc = p9_virtio_rpc;
trans->priv = chan;
return trans;
}
/**
* 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,
.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");