net/9p/trans_virtio.c

   1 /*
   2  * The Virtio 9p transport driver
   3  *
   4  * This is a block based transport driver based on the lguest block driver
   5  * code.
   6  *
   7  *  Copyright (C) 2007, 2008 Eric Van Hensbergen, IBM Corporation
   8  *
   9  *  Based on virtio console driver
  10  *  Copyright (C) 2006, 2007 Rusty Russell, IBM Corporation
  11  *
  12  *  This program is free software; you can redistribute it and/or modify
  13  *  it under the terms of the GNU General Public License version 2
  14  *  as published by the Free Software Foundation.
  15  *
  16  *  This program is distributed in the hope that it will be useful,
  17  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19  *  GNU General Public License for more details.
  20  *
  21  *  You should have received a copy of the GNU General Public License
  22  *  along with this program; if not, write to:
  23  *  Free Software Foundation
  24  *  51 Franklin Street, Fifth Floor
  25  *  Boston, MA  02111-1301  USA
  26  *
  27  */
  28
  29 #include <linux/in.h>
  30 #include <linux/module.h>
  31 #include <linux/net.h>
  32 #include <linux/ipv6.h>
  33 #include <linux/errno.h>
  34 #include <linux/kernel.h>
  35 #include <linux/un.h>
  36 #include <linux/uaccess.h>
  37 #include <linux/inet.h>
  38 #include <linux/idr.h>
  39 #include <linux/file.h>
  40 #include <net/9p/9p.h>
  41 #include <linux/parser.h>
  42 #include <net/9p/client.h>
  43 #include <net/9p/transport.h>
  44 #include <linux/scatterlist.h>
  45 #include <linux/virtio.h>
  46 #include <linux/virtio_9p.h>
  47
  48 #define VIRTQUEUE_NUM   128
  49
  50 /* a single mutex to manage channel initialization and attachment */
  51 static DEFINE_MUTEX(virtio_9p_lock);
  52
  53 /**
  54  * struct virtio_chan - per-instance transport information
  55  * @initialized: whether the channel is initialized
  56  * @inuse: whether the channel is in use
  57  * @lock: protects multiple elements within this structure
  58  * @client: client instance
  59  * @vdev: virtio dev associated with this channel
  60  * @vq: virtio queue associated with this channel
  61  * @sg: scatter gather list which is used to pack a request (protected?)
  62  *
  63  * We keep all per-channel information in a structure.
  64  * This structure is allocated within the devices dev->mem space.
  65  * A pointer to the structure will get put in the transport private.
  66  *
  67  */
  68
  69 struct virtio_chan {
  70         bool inuse;
  71
  72         spinlock_t lock;
  73
  74         struct p9_client *client;
  75         struct virtio_device *vdev;
  76         struct virtqueue *vq;
  77
  78         /* Scatterlist: can be too big for stack. */
  79         struct scatterlist sg[VIRTQUEUE_NUM];
  80
  81         struct list_head chan_list;
  82 };
  83
  84 static struct list_head virtio_chan_list;
  85
  86 /* How many bytes left in this page. */
  87 static unsigned int rest_of_page(void *data)
  88 {
  89         return PAGE_SIZE - ((unsigned long)data % PAGE_SIZE);
  90 }
  91
  92 /**
  93  * p9_virtio_close - reclaim resources of a channel
  94  * @client: client instance
  95  *
  96  * This reclaims a channel by freeing its resources and
  97  * reseting its inuse flag.
  98  *
  99  */
 100
 101 static void p9_virtio_close(struct p9_client *client)
 102 {
 103         struct virtio_chan *chan = client->trans;
 104
 105         mutex_lock(&virtio_9p_lock);
 106         if (chan)
 107                 chan->inuse = false;
 108         mutex_unlock(&virtio_9p_lock);
 109 }
 110
 111 /**
 112  * req_done - callback which signals activity from the server
 113  * @vq: virtio queue activity was received on
 114  *
 115  * This notifies us that the server has triggered some activity
 116  * on the virtio channel - most likely a response to request we
 117  * sent.  Figure out which requests now have responses and wake up
 118  * those threads.
 119  *
 120  * Bugs: could do with some additional sanity checking, but appears to work.
 121  *
 122  */
 123
 124 static void req_done(struct virtqueue *vq)
 125 {
 126         struct virtio_chan *chan = vq->vdev->priv;
 127         struct p9_fcall *rc;
 128         unsigned int len;
 129         struct p9_req_t *req;
 130
 131         P9_DPRINTK(P9_DEBUG_TRANS, ": request done\n");
 132
 133         while ((rc = chan->vq->vq_ops->get_buf(chan->vq, &len)) != NULL) {
 134                 P9_DPRINTK(P9_DEBUG_TRANS, ": rc %p\n", rc);
 135                 P9_DPRINTK(P9_DEBUG_TRANS, ": lookup tag %d\n", rc->tag);
 136                 req = p9_tag_lookup(chan->client, rc->tag);
 137                 req->status = REQ_STATUS_RCVD;
 138                 p9_client_cb(chan->client, req);
 139         }
 140 }
 141
 142 /**
 143  * pack_sg_list - pack a scatter gather list from a linear buffer
 144  * @sg: scatter/gather list to pack into
 145  * @start: which segment of the sg_list to start at
 146  * @limit: maximum segment to pack data to
 147  * @data: data to pack into scatter/gather list
 148  * @count: amount of data to pack into the scatter/gather list
 149  *
 150  * sg_lists have multiple segments of various sizes.  This will pack
 151  * arbitrary data into an existing scatter gather list, segmenting the
 152  * data as necessary within constraints.
 153  *
 154  */
 155
 156 static int
 157 pack_sg_list(struct scatterlist *sg, int start, int limit, char *data,
 158                                                                 int count)
 159 {
 160         int s;
 161         int index = start;
 162
 163         while (count) {
 164                 s = rest_of_page(data);
 165                 if (s > count)
 166                         s = count;
 167                 sg_set_buf(&sg[index++], data, s);
 168                 count -= s;
 169                 data += s;
 170                 BUG_ON(index > limit);
 171         }
 172
 173         return index-start;
 174 }
 175
 176 /* We don't currently allow canceling of virtio requests */
 177 static int p9_virtio_cancel(struct p9_client *client, struct p9_req_t *req)
 178 {
 179         return 1;
 180 }
 181
 182 /**
 183  * p9_virtio_request - issue a request
 184  * @client: client instance issuing the request
 185  * @req: request to be issued
 186  *
 187  */
 188
 189 static int
 190 p9_virtio_request(struct p9_client *client, struct p9_req_t *req)
 191 {
 192         int in, out;
 193         struct virtio_chan *chan = client->trans;
 194         char *rdata = (char *)req->rc+sizeof(struct p9_fcall);
 195
 196         P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio request\n");
 197
 198         out = pack_sg_list(chan->sg, 0, VIRTQUEUE_NUM, req->tc->sdata,
 199                                                                 req->tc->size);
 200         in = pack_sg_list(chan->sg, out, VIRTQUEUE_NUM-out, rdata,
 201                                                                 client->msize);
 202
 203         req->status = REQ_STATUS_SENT;
 204
 205         if (chan->vq->vq_ops->add_buf(chan->vq, chan->sg, out, in, req->tc) < 0) {
 206                 P9_DPRINTK(P9_DEBUG_TRANS,
 207                         "9p debug: virtio rpc add_buf returned failure");
 208                 return -EIO;
 209         }
 210
 211         chan->vq->vq_ops->kick(chan->vq);
 212
 213         P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio request kicked\n");
 214         return 0;
 215 }
 216
 217 /**
 218  * p9_virtio_probe - probe for existence of 9P virtio channels
 219  * @vdev: virtio device to probe
 220  *
 221  * This probes for existing virtio channels.
 222  *
 223  */
 224
 225 static int p9_virtio_probe(struct virtio_device *vdev)
 226 {
 227         int err;
 228         struct virtio_chan *chan;
 229
 230         chan = kmalloc(sizeof(struct virtio_chan), GFP_KERNEL);
 231         if (!chan) {
 232                 printk(KERN_ERR "9p: Failed to allocate virtio 9P channel\n");
 233                 err = -ENOMEM;
 234                 goto fail;
 235         }
 236
 237         chan->vdev = vdev;
 238
 239         /* We expect one virtqueue, for requests. */
 240         chan->vq = virtio_find_single_vq(vdev, req_done, "requests");
 241         if (IS_ERR(chan->vq)) {
 242                 err = PTR_ERR(chan->vq);
 243                 goto out_free_vq;
 244         }
 245         chan->vq->vdev->priv = chan;
 246         spin_lock_init(&chan->lock);
 247
 248         sg_init_table(chan->sg, VIRTQUEUE_NUM);
 249
 250         chan->inuse = false;
 251         mutex_lock(&virtio_9p_lock);
 252         list_add_tail(&chan->chan_list, &virtio_chan_list);
 253         mutex_unlock(&virtio_9p_lock);
 254         return 0;
 255
 256 out_free_vq:
 257         vdev->config->del_vqs(vdev);
 258         kfree(chan);
 259 fail:
 260         return err;
 261 }
 262
 263
 264 /**
 265  * p9_virtio_create - allocate a new virtio channel
 266  * @client: client instance invoking this transport
 267  * @devname: string identifying the channel to connect to (unused)
 268  * @args: args passed from sys_mount() for per-transport options (unused)
 269  *
 270  * This sets up a transport channel for 9p communication.  Right now
 271  * we only match the first available channel, but eventually we couldlook up
 272  * alternate channels by matching devname versus a virtio_config entry.
 273  * We use a simple reference count mechanism to ensure that only a single
 274  * mount has a channel open at a time.
 275  *
 276  */
 277
 278 static int
 279 p9_virtio_create(struct p9_client *client, const char *devname, char *args)
 280 {
 281         struct virtio_chan *chan;
 282         int ret = -ENOENT;
 283         int found = 0;
 284
 285         mutex_lock(&virtio_9p_lock);
 286         list_for_each_entry(chan, &virtio_chan_list, chan_list) {
 287                 if (!strcmp(devname, dev_name(&chan->vdev->dev))) {
 288                         if (!chan->inuse) {
 289                                 chan->inuse = true;
 290                                 found = 1;
 291                                 break;
 292                         }
 293                         ret = -EBUSY;
 294                 }
 295         }
 296         mutex_unlock(&virtio_9p_lock);
 297
 298         if (!found) {
 299                 printk(KERN_ERR "9p: no channels available\n");
 300                 return ret;
 301         }
 302
 303         client->trans = (void *)chan;
 304         client->status = Connected;
 305         chan->client = client;
 306
 307         return 0;
 308 }
 309
 310 /**
 311  * p9_virtio_remove - clean up resources associated with a virtio device
 312  * @vdev: virtio device to remove
 313  *
 314  */
 315
 316 static void p9_virtio_remove(struct virtio_device *vdev)
 317 {
 318         struct virtio_chan *chan = vdev->priv;
 319
 320         BUG_ON(chan->inuse);
 321         vdev->config->del_vqs(vdev);
 322
 323         mutex_lock(&virtio_9p_lock);
 324         list_del(&chan->chan_list);
 325         mutex_unlock(&virtio_9p_lock);
 326         kfree(chan);
 327
 328 }
 329
 330 static struct virtio_device_id id_table[] = {
 331         { VIRTIO_ID_9P, VIRTIO_DEV_ANY_ID },
 332         { 0 },
 333 };
 334
 335 /* The standard "struct lguest_driver": */
 336 static struct virtio_driver p9_virtio_drv = {
 337         .driver.name =  KBUILD_MODNAME,
 338         .driver.owner = THIS_MODULE,
 339         .id_table =     id_table,
 340         .probe =        p9_virtio_probe,
 341         .remove =       p9_virtio_remove,
 342 };
 343
 344 static struct p9_trans_module p9_virtio_trans = {
 345         .name = "virtio",
 346         .create = p9_virtio_create,
 347         .close = p9_virtio_close,
 348         .request = p9_virtio_request,
 349         .cancel = p9_virtio_cancel,
 350         .maxsize = PAGE_SIZE*16,
 351         .def = 0,
 352         .owner = THIS_MODULE,
 353 };
 354
 355 /* The standard init function */
 356 static int __init p9_virtio_init(void)
 357 {
 358         INIT_LIST_HEAD(&virtio_chan_list);
 359
 360         v9fs_register_trans(&p9_virtio_trans);
 361         return register_virtio_driver(&p9_virtio_drv);
 362 }
 363
 364 static void __exit p9_virtio_cleanup(void)
 365 {
 366         unregister_virtio_driver(&p9_virtio_drv);
 367         v9fs_unregister_trans(&p9_virtio_trans);
 368 }
 369
 370 module_init(p9_virtio_init);
 371 module_exit(p9_virtio_cleanup);
 372
 373 MODULE_DEVICE_TABLE(virtio, id_table);
 374 MODULE_AUTHOR("Eric Van Hensbergen <ericvh@gmail.com>");
 375 MODULE_DESCRIPTION("Virtio 9p Transport");
 376 MODULE_LICENSE("GPL");