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         int tag_len;
  82         /*
  83          * tag name to identify a mount Non-null terminated
  84          */
  85         char *tag;
  86
  87         struct list_head chan_list;
  88 };
  89
  90 static struct list_head virtio_chan_list;
  91
  92 /* How many bytes left in this page. */
  93 static unsigned int rest_of_page(void *data)
  94 {
  95         return PAGE_SIZE - ((unsigned long)data % PAGE_SIZE);
  96 }
  97
  98 /**
  99  * p9_virtio_close - reclaim resources of a channel
 100  * @client: client instance
 101  *
 102  * This reclaims a channel by freeing its resources and
 103  * reseting its inuse flag.
 104  *
 105  */
 106
 107 static void p9_virtio_close(struct p9_client *client)
 108 {
 109         struct virtio_chan *chan = client->trans;
 110
 111         mutex_lock(&virtio_9p_lock);
 112         if (chan)
 113                 chan->inuse = false;
 114         mutex_unlock(&virtio_9p_lock);
 115 }
 116
 117 /**
 118  * req_done - callback which signals activity from the server
 119  * @vq: virtio queue activity was received on
 120  *
 121  * This notifies us that the server has triggered some activity
 122  * on the virtio channel - most likely a response to request we
 123  * sent.  Figure out which requests now have responses and wake up
 124  * those threads.
 125  *
 126  * Bugs: could do with some additional sanity checking, but appears to work.
 127  *
 128  */
 129
 130 static void req_done(struct virtqueue *vq)
 131 {
 132         struct virtio_chan *chan = vq->vdev->priv;
 133         struct p9_fcall *rc;
 134         unsigned int len;
 135         struct p9_req_t *req;
 136
 137         P9_DPRINTK(P9_DEBUG_TRANS, ": request done\n");
 138
 139         while ((rc = chan->vq->vq_ops->get_buf(chan->vq, &len)) != NULL) {
 140                 P9_DPRINTK(P9_DEBUG_TRANS, ": rc %p\n", rc);
 141                 P9_DPRINTK(P9_DEBUG_TRANS, ": lookup tag %d\n", rc->tag);
 142                 req = p9_tag_lookup(chan->client, rc->tag);
 143                 req->status = REQ_STATUS_RCVD;
 144                 p9_client_cb(chan->client, req);
 145         }
 146 }
 147
 148 /**
 149  * pack_sg_list - pack a scatter gather list from a linear buffer
 150  * @sg: scatter/gather list to pack into
 151  * @start: which segment of the sg_list to start at
 152  * @limit: maximum segment to pack data to
 153  * @data: data to pack into scatter/gather list
 154  * @count: amount of data to pack into the scatter/gather list
 155  *
 156  * sg_lists have multiple segments of various sizes.  This will pack
 157  * arbitrary data into an existing scatter gather list, segmenting the
 158  * data as necessary within constraints.
 159  *
 160  */
 161
 162 static int
 163 pack_sg_list(struct scatterlist *sg, int start, int limit, char *data,
 164                                                                 int count)
 165 {
 166         int s;
 167         int index = start;
 168
 169         while (count) {
 170                 s = rest_of_page(data);
 171                 if (s > count)
 172                         s = count;
 173                 sg_set_buf(&sg[index++], data, s);
 174                 count -= s;
 175                 data += s;
 176                 BUG_ON(index > limit);
 177         }
 178
 179         return index-start;
 180 }
 181
 182 /* We don't currently allow canceling of virtio requests */
 183 static int p9_virtio_cancel(struct p9_client *client, struct p9_req_t *req)
 184 {
 185         return 1;
 186 }
 187
 188 /**
 189  * p9_virtio_request - issue a request
 190  * @client: client instance issuing the request
 191  * @req: request to be issued
 192  *
 193  */
 194
 195 static int
 196 p9_virtio_request(struct p9_client *client, struct p9_req_t *req)
 197 {
 198         int in, out;
 199         struct virtio_chan *chan = client->trans;
 200         char *rdata = (char *)req->rc+sizeof(struct p9_fcall);
 201
 202         P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio request\n");
 203
 204         out = pack_sg_list(chan->sg, 0, VIRTQUEUE_NUM, req->tc->sdata,
 205                                                                 req->tc->size);
 206         in = pack_sg_list(chan->sg, out, VIRTQUEUE_NUM-out, rdata,
 207                                                                 client->msize);
 208
 209         req->status = REQ_STATUS_SENT;
 210
 211         if (chan->vq->vq_ops->add_buf(chan->vq, chan->sg, out, in, req->tc) < 0) {
 212                 P9_DPRINTK(P9_DEBUG_TRANS,
 213                         "9p debug: virtio rpc add_buf returned failure");
 214                 return -EIO;
 215         }
 216
 217         chan->vq->vq_ops->kick(chan->vq);
 218
 219         P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio request kicked\n");
 220         return 0;
 221 }
 222
 223 /**
 224  * p9_virtio_probe - probe for existence of 9P virtio channels
 225  * @vdev: virtio device to probe
 226  *
 227  * This probes for existing virtio channels.
 228  *
 229  */
 230
 231 static int p9_virtio_probe(struct virtio_device *vdev)
 232 {
 233         __u16 tag_len;
 234         char *tag;
 235         int err;
 236         struct virtio_chan *chan;
 237
 238         chan = kmalloc(sizeof(struct virtio_chan), GFP_KERNEL);
 239         if (!chan) {
 240                 printk(KERN_ERR "9p: Failed to allocate virtio 9P channel\n");
 241                 err = -ENOMEM;
 242                 goto fail;
 243         }
 244
 245         chan->vdev = vdev;
 246
 247         /* We expect one virtqueue, for requests. */
 248         chan->vq = virtio_find_single_vq(vdev, req_done, "requests");
 249         if (IS_ERR(chan->vq)) {
 250                 err = PTR_ERR(chan->vq);
 251                 goto out_free_vq;
 252         }
 253         chan->vq->vdev->priv = chan;
 254         spin_lock_init(&chan->lock);
 255
 256         sg_init_table(chan->sg, VIRTQUEUE_NUM);
 257
 258         chan->inuse = false;
 259         if (virtio_has_feature(vdev, VIRTIO_9P_MOUNT_TAG)) {
 260                 vdev->config->get(vdev,
 261                                 offsetof(struct virtio_9p_config, tag_len),
 262                                 &tag_len, sizeof(tag_len));
 263         } else {
 264                 err = -EINVAL;
 265                 goto out_free_vq;
 266         }
 267         tag = kmalloc(tag_len, GFP_KERNEL);
 268         if (!tag) {
 269                 err = -ENOMEM;
 270                 goto out_free_vq;
 271         }
 272         vdev->config->get(vdev, offsetof(struct virtio_9p_config, tag),
 273                         tag, tag_len);
 274         chan->tag = tag;
 275         chan->tag_len = tag_len;
 276         mutex_lock(&virtio_9p_lock);
 277         list_add_tail(&chan->chan_list, &virtio_chan_list);
 278         mutex_unlock(&virtio_9p_lock);
 279         return 0;
 280
 281 out_free_vq:
 282         vdev->config->del_vqs(vdev);
 283         kfree(chan);
 284 fail:
 285         return err;
 286 }
 287
 288
 289 /**
 290  * p9_virtio_create - allocate a new virtio channel
 291  * @client: client instance invoking this transport
 292  * @devname: string identifying the channel to connect to (unused)
 293  * @args: args passed from sys_mount() for per-transport options (unused)
 294  *
 295  * This sets up a transport channel for 9p communication.  Right now
 296  * we only match the first available channel, but eventually we couldlook up
 297  * alternate channels by matching devname versus a virtio_config entry.
 298  * We use a simple reference count mechanism to ensure that only a single
 299  * mount has a channel open at a time.
 300  *
 301  */
 302
 303 static int
 304 p9_virtio_create(struct p9_client *client, const char *devname, char *args)
 305 {
 306         struct virtio_chan *chan;
 307         int ret = -ENOENT;
 308         int found = 0;
 309
 310         mutex_lock(&virtio_9p_lock);
 311         list_for_each_entry(chan, &virtio_chan_list, chan_list) {
 312                 if (!strncmp(devname, chan->tag, chan->tag_len)) {
 313                         if (!chan->inuse) {
 314                                 chan->inuse = true;
 315                                 found = 1;
 316                                 break;
 317                         }
 318                         ret = -EBUSY;
 319                 }
 320         }
 321         mutex_unlock(&virtio_9p_lock);
 322
 323         if (!found) {
 324                 printk(KERN_ERR "9p: no channels available\n");
 325                 return ret;
 326         }
 327
 328         client->trans = (void *)chan;
 329         client->status = Connected;
 330         chan->client = client;
 331
 332         return 0;
 333 }
 334
 335 /**
 336  * p9_virtio_remove - clean up resources associated with a virtio device
 337  * @vdev: virtio device to remove
 338  *
 339  */
 340
 341 static void p9_virtio_remove(struct virtio_device *vdev)
 342 {
 343         struct virtio_chan *chan = vdev->priv;
 344
 345         BUG_ON(chan->inuse);
 346         vdev->config->del_vqs(vdev);
 347
 348         mutex_lock(&virtio_9p_lock);
 349         list_del(&chan->chan_list);
 350         mutex_unlock(&virtio_9p_lock);
 351         kfree(chan->tag);
 352         kfree(chan);
 353
 354 }
 355
 356 static struct virtio_device_id id_table[] = {
 357         { VIRTIO_ID_9P, VIRTIO_DEV_ANY_ID },
 358         { 0 },
 359 };
 360
 361 static unsigned int features[] = {
 362         VIRTIO_9P_MOUNT_TAG,
 363 };
 364
 365 /* The standard "struct lguest_driver": */
 366 static struct virtio_driver p9_virtio_drv = {
 367         .feature_table  = features,
 368         .feature_table_size = ARRAY_SIZE(features),
 369         .driver.name    = KBUILD_MODNAME,
 370         .driver.owner   = THIS_MODULE,
 371         .id_table       = id_table,
 372         .probe          = p9_virtio_probe,
 373         .remove         = p9_virtio_remove,
 374 };
 375
 376 static struct p9_trans_module p9_virtio_trans = {
 377         .name = "virtio",
 378         .create = p9_virtio_create,
 379         .close = p9_virtio_close,
 380         .request = p9_virtio_request,
 381         .cancel = p9_virtio_cancel,
 382         .maxsize = PAGE_SIZE*16,
 383         .def = 0,
 384         .owner = THIS_MODULE,
 385 };
 386
 387 /* The standard init function */
 388 static int __init p9_virtio_init(void)
 389 {
 390         INIT_LIST_HEAD(&virtio_chan_list);
 391
 392         v9fs_register_trans(&p9_virtio_trans);
 393         return register_virtio_driver(&p9_virtio_drv);
 394 }
 395
 396 static void __exit p9_virtio_cleanup(void)
 397 {
 398         unregister_virtio_driver(&p9_virtio_drv);
 399         v9fs_unregister_trans(&p9_virtio_trans);
 400 }
 401
 402 module_init(p9_virtio_init);
 403 module_exit(p9_virtio_cleanup);
 404
 405 MODULE_DEVICE_TABLE(virtio, id_table);
 406 MODULE_AUTHOR("Eric Van Hensbergen <ericvh@gmail.com>");
 407 MODULE_DESCRIPTION("Virtio 9p Transport");
 408 MODULE_LICENSE("GPL");