net/9p/trans_virtio.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * The Virtio 9p transport driver
   4  *
   5  * This is a block based transport driver based on the lguest block driver
   6  * code.
   7  *
   8  *  Copyright (C) 2007, 2008 Eric Van Hensbergen, IBM Corporation
   9  *
  10  *  Based on virtio console driver
  11  *  Copyright (C) 2006, 2007 Rusty Russell, IBM Corporation
  12  */
  13
  14 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  15
  16 #include <linux/in.h>
  17 #include <linux/module.h>
  18 #include <linux/net.h>
  19 #include <linux/ipv6.h>
  20 #include <linux/errno.h>
  21 #include <linux/kernel.h>
  22 #include <linux/un.h>
  23 #include <linux/uaccess.h>
  24 #include <linux/inet.h>
  25 #include <linux/file.h>
  26 #include <linux/highmem.h>
  27 #include <linux/slab.h>
  28 #include <net/9p/9p.h>
  29 #include <linux/parser.h>
  30 #include <net/9p/client.h>
  31 #include <net/9p/transport.h>
  32 #include <linux/scatterlist.h>
  33 #include <linux/swap.h>
  34 #include <linux/virtio.h>
  35 #include <linux/virtio_9p.h>
  36 #include "trans_common.h"
  37
  38 #define VIRTQUEUE_NUM   128
  39
  40 /* a single mutex to manage channel initialization and attachment */
  41 static DEFINE_MUTEX(virtio_9p_lock);
  42 static DECLARE_WAIT_QUEUE_HEAD(vp_wq);
  43 static atomic_t vp_pinned = ATOMIC_INIT(0);
  44
  45 /**
  46  * struct virtio_chan - per-instance transport information
  47  * @inuse: whether the channel is in use
  48  * @lock: protects multiple elements within this structure
  49  * @client: client instance
  50  * @vdev: virtio dev associated with this channel
  51  * @vq: virtio queue associated with this channel
  52  * @ring_bufs_avail: flag to indicate there is some available in the ring buf
  53  * @vc_wq: wait queue for waiting for thing to be added to ring buf
  54  * @p9_max_pages: maximum number of pinned pages
  55  * @sg: scatter gather list which is used to pack a request (protected?)
  56  * @chan_list: linked list of channels
  57  *
  58  * We keep all per-channel information in a structure.
  59  * This structure is allocated within the devices dev->mem space.
  60  * A pointer to the structure will get put in the transport private.
  61  *
  62  */
  63
  64 struct virtio_chan {
  65         bool inuse;
  66
  67         spinlock_t lock;
  68
  69         struct p9_client *client;
  70         struct virtio_device *vdev;
  71         struct virtqueue *vq;
  72         int ring_bufs_avail;
  73         wait_queue_head_t *vc_wq;
  74         /* This is global limit. Since we don't have a global structure,
  75          * will be placing it in each channel.
  76          */
  77         unsigned long p9_max_pages;
  78         /* Scatterlist: can be too big for stack. */
  79         struct scatterlist sg[VIRTQUEUE_NUM];
  80         /**
  81          * @tag: name to identify a mount null terminated
  82          */
  83         char *tag;
  84
  85         struct list_head chan_list;
  86 };
  87
  88 static struct list_head virtio_chan_list;
  89
  90 /* How many bytes left in this page. */
  91 static unsigned int rest_of_page(void *data)
  92 {
  93         return PAGE_SIZE - offset_in_page(data);
  94 }
  95
  96 /**
  97  * p9_virtio_close - reclaim resources of a channel
  98  * @client: client instance
  99  *
 100  * This reclaims a channel by freeing its resources and
 101  * resetting its inuse flag.
 102  *
 103  */
 104
 105 static void p9_virtio_close(struct p9_client *client)
 106 {
 107         struct virtio_chan *chan = client->trans;
 108
 109         mutex_lock(&virtio_9p_lock);
 110         if (chan)
 111                 chan->inuse = false;
 112         mutex_unlock(&virtio_9p_lock);
 113 }
 114
 115 /**
 116  * req_done - callback which signals activity from the server
 117  * @vq: virtio queue activity was received on
 118  *
 119  * This notifies us that the server has triggered some activity
 120  * on the virtio channel - most likely a response to request we
 121  * sent.  Figure out which requests now have responses and wake up
 122  * those threads.
 123  *
 124  * Bugs: could do with some additional sanity checking, but appears to work.
 125  *
 126  */
 127
 128 static void req_done(struct virtqueue *vq)
 129 {
 130         struct virtio_chan *chan = vq->vdev->priv;
 131         unsigned int len;
 132         struct p9_req_t *req;
 133         bool need_wakeup = false;
 134         unsigned long flags;
 135
 136         p9_debug(P9_DEBUG_TRANS, ": request done\n");
 137
 138         spin_lock_irqsave(&chan->lock, flags);
 139         while ((req = virtqueue_get_buf(chan->vq, &len)) != NULL) {
 140                 if (!chan->ring_bufs_avail) {
 141                         chan->ring_bufs_avail = 1;
 142                         need_wakeup = true;
 143                 }
 144
 145                 if (len) {
 146                         req->rc.size = len;
 147                         p9_client_cb(chan->client, req, REQ_STATUS_RCVD);
 148                 }
 149         }
 150         spin_unlock_irqrestore(&chan->lock, flags);
 151         /* Wakeup if anyone waiting for VirtIO ring space. */
 152         if (need_wakeup)
 153                 wake_up(chan->vc_wq);
 154 }
 155
 156 /**
 157  * pack_sg_list - pack a scatter gather list from a linear buffer
 158  * @sg: scatter/gather list to pack into
 159  * @start: which segment of the sg_list to start at
 160  * @limit: maximum segment to pack data to
 161  * @data: data to pack into scatter/gather list
 162  * @count: amount of data to pack into the scatter/gather list
 163  *
 164  * sg_lists have multiple segments of various sizes.  This will pack
 165  * arbitrary data into an existing scatter gather list, segmenting the
 166  * data as necessary within constraints.
 167  *
 168  */
 169
 170 static int pack_sg_list(struct scatterlist *sg, int start,
 171                         int limit, char *data, int count)
 172 {
 173         int s;
 174         int index = start;
 175
 176         while (count) {
 177                 s = rest_of_page(data);
 178                 if (s > count)
 179                         s = count;
 180                 BUG_ON(index >= limit);
 181                 /* Make sure we don't terminate early. */
 182                 sg_unmark_end(&sg[index]);
 183                 sg_set_buf(&sg[index++], data, s);
 184                 count -= s;
 185                 data += s;
 186         }
 187         if (index-start)
 188                 sg_mark_end(&sg[index - 1]);
 189         return index-start;
 190 }
 191
 192 /* We don't currently allow canceling of virtio requests */
 193 static int p9_virtio_cancel(struct p9_client *client, struct p9_req_t *req)
 194 {
 195         return 1;
 196 }
 197
 198 /* Reply won't come, so drop req ref */
 199 static int p9_virtio_cancelled(struct p9_client *client, struct p9_req_t *req)
 200 {
 201         p9_req_put(client, req);
 202         return 0;
 203 }
 204
 205 /**
 206  * pack_sg_list_p - Just like pack_sg_list. Instead of taking a buffer,
 207  * this takes a list of pages.
 208  * @sg: scatter/gather list to pack into
 209  * @start: which segment of the sg_list to start at
 210  * @limit: maximum number of pages in sg list.
 211  * @pdata: a list of pages to add into sg.
 212  * @nr_pages: number of pages to pack into the scatter/gather list
 213  * @offs: amount of data in the beginning of first page _not_ to pack
 214  * @count: amount of data to pack into the scatter/gather list
 215  */
 216 static int
 217 pack_sg_list_p(struct scatterlist *sg, int start, int limit,
 218                struct page **pdata, int nr_pages, size_t offs, int count)
 219 {
 220         int i = 0, s;
 221         int data_off = offs;
 222         int index = start;
 223
 224         BUG_ON(nr_pages > (limit - start));
 225         /*
 226          * if the first page doesn't start at
 227          * page boundary find the offset
 228          */
 229         while (nr_pages) {
 230                 s = PAGE_SIZE - data_off;
 231                 if (s > count)
 232                         s = count;
 233                 BUG_ON(index >= limit);
 234                 /* Make sure we don't terminate early. */
 235                 sg_unmark_end(&sg[index]);
 236                 sg_set_page(&sg[index++], pdata[i++], s, data_off);
 237                 data_off = 0;
 238                 count -= s;
 239                 nr_pages--;
 240         }
 241
 242         if (index-start)
 243                 sg_mark_end(&sg[index - 1]);
 244         return index - start;
 245 }
 246
 247 /**
 248  * p9_virtio_request - issue a request
 249  * @client: client instance issuing the request
 250  * @req: request to be issued
 251  *
 252  */
 253
 254 static int
 255 p9_virtio_request(struct p9_client *client, struct p9_req_t *req)
 256 {
 257         int err;
 258         int in, out, out_sgs, in_sgs;
 259         unsigned long flags;
 260         struct virtio_chan *chan = client->trans;
 261         struct scatterlist *sgs[2];
 262
 263         p9_debug(P9_DEBUG_TRANS, "9p debug: virtio request\n");
 264
 265         WRITE_ONCE(req->status, REQ_STATUS_SENT);
 266 req_retry:
 267         spin_lock_irqsave(&chan->lock, flags);
 268
 269         out_sgs = in_sgs = 0;
 270         /* Handle out VirtIO ring buffers */
 271         out = pack_sg_list(chan->sg, 0,
 272                            VIRTQUEUE_NUM, req->tc.sdata, req->tc.size);
 273         if (out)
 274                 sgs[out_sgs++] = chan->sg;
 275
 276         in = pack_sg_list(chan->sg, out,
 277                           VIRTQUEUE_NUM, req->rc.sdata, req->rc.capacity);
 278         if (in)
 279                 sgs[out_sgs + in_sgs++] = chan->sg + out;
 280
 281         err = virtqueue_add_sgs(chan->vq, sgs, out_sgs, in_sgs, req,
 282                                 GFP_ATOMIC);
 283         if (err < 0) {
 284                 if (err == -ENOSPC) {
 285                         chan->ring_bufs_avail = 0;
 286                         spin_unlock_irqrestore(&chan->lock, flags);
 287                         err = wait_event_killable(*chan->vc_wq,
 288                                                   chan->ring_bufs_avail);
 289                         if (err  == -ERESTARTSYS)
 290                                 return err;
 291
 292                         p9_debug(P9_DEBUG_TRANS, "Retry virtio request\n");
 293                         goto req_retry;
 294                 } else {
 295                         spin_unlock_irqrestore(&chan->lock, flags);
 296                         p9_debug(P9_DEBUG_TRANS,
 297                                  "virtio rpc add_sgs returned failure\n");
 298                         return -EIO;
 299                 }
 300         }
 301         virtqueue_kick(chan->vq);
 302         spin_unlock_irqrestore(&chan->lock, flags);
 303
 304         p9_debug(P9_DEBUG_TRANS, "virtio request kicked\n");
 305         return 0;
 306 }
 307
 308 static int p9_get_mapped_pages(struct virtio_chan *chan,
 309                                struct page ***pages,
 310                                struct iov_iter *data,
 311                                int count,
 312                                size_t *offs,
 313                                int *need_drop)
 314 {
 315         int nr_pages;
 316         int err;
 317
 318         if (!iov_iter_count(data))
 319                 return 0;
 320
 321         if (!iov_iter_is_kvec(data)) {
 322                 int n;
 323                 /*
 324                  * We allow only p9_max_pages pinned. We wait for the
 325                  * Other zc request to finish here
 326                  */
 327                 if (atomic_read(&vp_pinned) >= chan->p9_max_pages) {
 328                         err = wait_event_killable(vp_wq,
 329                               (atomic_read(&vp_pinned) < chan->p9_max_pages));
 330                         if (err == -ERESTARTSYS)
 331                                 return err;
 332                 }
 333                 n = iov_iter_get_pages_alloc2(data, pages, count, offs);
 334                 if (n < 0)
 335                         return n;
 336                 *need_drop = 1;
 337                 nr_pages = DIV_ROUND_UP(n + *offs, PAGE_SIZE);
 338                 atomic_add(nr_pages, &vp_pinned);
 339                 return n;
 340         } else {
 341                 /* kernel buffer, no need to pin pages */
 342                 int index;
 343                 size_t len;
 344                 void *p;
 345
 346                 /* we'd already checked that it's non-empty */
 347                 while (1) {
 348                         len = iov_iter_single_seg_count(data);
 349                         if (likely(len)) {
 350                                 p = data->kvec->iov_base + data->iov_offset;
 351                                 break;
 352                         }
 353                         iov_iter_advance(data, 0);
 354                 }
 355                 if (len > count)
 356                         len = count;
 357
 358                 nr_pages = DIV_ROUND_UP((unsigned long)p + len, PAGE_SIZE) -
 359                            (unsigned long)p / PAGE_SIZE;
 360
 361                 *pages = kmalloc_array(nr_pages, sizeof(struct page *),
 362                                        GFP_NOFS);
 363                 if (!*pages)
 364                         return -ENOMEM;
 365
 366                 *need_drop = 0;
 367                 p -= (*offs = offset_in_page(p));
 368                 for (index = 0; index < nr_pages; index++) {
 369                         if (is_vmalloc_addr(p))
 370                                 (*pages)[index] = vmalloc_to_page(p);
 371                         else
 372                                 (*pages)[index] = kmap_to_page(p);
 373                         p += PAGE_SIZE;
 374                 }
 375                 iov_iter_advance(data, len);
 376                 return len;
 377         }
 378 }
 379
 380 static void handle_rerror(struct p9_req_t *req, int in_hdr_len,
 381                           size_t offs, struct page **pages)
 382 {
 383         unsigned size, n;
 384         void *to = req->rc.sdata + in_hdr_len;
 385
 386         // Fits entirely into the static data?  Nothing to do.
 387         if (req->rc.size < in_hdr_len || !pages)
 388                 return;
 389
 390         // Really long error message?  Tough, truncate the reply.  Might get
 391         // rejected (we can't be arsed to adjust the size encoded in header,
 392         // or string size for that matter), but it wouldn't be anything valid
 393         // anyway.
 394         if (unlikely(req->rc.size > P9_ZC_HDR_SZ))
 395                 req->rc.size = P9_ZC_HDR_SZ;
 396
 397         // data won't span more than two pages
 398         size = req->rc.size - in_hdr_len;
 399         n = PAGE_SIZE - offs;
 400         if (size > n) {
 401                 memcpy_from_page(to, *pages++, offs, n);
 402                 offs = 0;
 403                 to += n;
 404                 size -= n;
 405         }
 406         memcpy_from_page(to, *pages, offs, size);
 407 }
 408
 409 /**
 410  * p9_virtio_zc_request - issue a zero copy request
 411  * @client: client instance issuing the request
 412  * @req: request to be issued
 413  * @uidata: user buffer that should be used for zero copy read
 414  * @uodata: user buffer that should be used for zero copy write
 415  * @inlen: read buffer size
 416  * @outlen: write buffer size
 417  * @in_hdr_len: reader header size, This is the size of response protocol data
 418  *
 419  */
 420 static int
 421 p9_virtio_zc_request(struct p9_client *client, struct p9_req_t *req,
 422                      struct iov_iter *uidata, struct iov_iter *uodata,
 423                      int inlen, int outlen, int in_hdr_len)
 424 {
 425         int in, out, err, out_sgs, in_sgs;
 426         unsigned long flags;
 427         int in_nr_pages = 0, out_nr_pages = 0;
 428         struct page **in_pages = NULL, **out_pages = NULL;
 429         struct virtio_chan *chan = client->trans;
 430         struct scatterlist *sgs[4];
 431         size_t offs = 0;
 432         int need_drop = 0;
 433         int kicked = 0;
 434
 435         p9_debug(P9_DEBUG_TRANS, "virtio request\n");
 436
 437         if (uodata) {
 438                 __le32 sz;
 439                 int n = p9_get_mapped_pages(chan, &out_pages, uodata,
 440                                             outlen, &offs, &need_drop);
 441                 if (n < 0) {
 442                         err = n;
 443                         goto err_out;
 444                 }
 445                 out_nr_pages = DIV_ROUND_UP(n + offs, PAGE_SIZE);
 446                 if (n != outlen) {
 447                         __le32 v = cpu_to_le32(n);
 448                         memcpy(&req->tc.sdata[req->tc.size - 4], &v, 4);
 449                         outlen = n;
 450                 }
 451                 /* The size field of the message must include the length of the
 452                  * header and the length of the data.  We didn't actually know
 453                  * the length of the data until this point so add it in now.
 454                  */
 455                 sz = cpu_to_le32(req->tc.size + outlen);
 456                 memcpy(&req->tc.sdata[0], &sz, sizeof(sz));
 457         } else if (uidata) {
 458                 int n = p9_get_mapped_pages(chan, &in_pages, uidata,
 459                                             inlen, &offs, &need_drop);
 460                 if (n < 0) {
 461                         err = n;
 462                         goto err_out;
 463                 }
 464                 in_nr_pages = DIV_ROUND_UP(n + offs, PAGE_SIZE);
 465                 if (n != inlen) {
 466                         __le32 v = cpu_to_le32(n);
 467                         memcpy(&req->tc.sdata[req->tc.size - 4], &v, 4);
 468                         inlen = n;
 469                 }
 470         }
 471         WRITE_ONCE(req->status, REQ_STATUS_SENT);
 472 req_retry_pinned:
 473         spin_lock_irqsave(&chan->lock, flags);
 474
 475         out_sgs = in_sgs = 0;
 476
 477         /* out data */
 478         out = pack_sg_list(chan->sg, 0,
 479                            VIRTQUEUE_NUM, req->tc.sdata, req->tc.size);
 480
 481         if (out)
 482                 sgs[out_sgs++] = chan->sg;
 483
 484         if (out_pages) {
 485                 sgs[out_sgs++] = chan->sg + out;
 486                 out += pack_sg_list_p(chan->sg, out, VIRTQUEUE_NUM,
 487                                       out_pages, out_nr_pages, offs, outlen);
 488         }
 489
 490         /*
 491          * Take care of in data
 492          * For example TREAD have 11.
 493          * 11 is the read/write header = PDU Header(7) + IO Size (4).
 494          * Arrange in such a way that server places header in the
 495          * allocated memory and payload onto the user buffer.
 496          */
 497         in = pack_sg_list(chan->sg, out,
 498                           VIRTQUEUE_NUM, req->rc.sdata, in_hdr_len);
 499         if (in)
 500                 sgs[out_sgs + in_sgs++] = chan->sg + out;
 501
 502         if (in_pages) {
 503                 sgs[out_sgs + in_sgs++] = chan->sg + out + in;
 504                 pack_sg_list_p(chan->sg, out + in, VIRTQUEUE_NUM,
 505                                in_pages, in_nr_pages, offs, inlen);
 506         }
 507
 508         BUG_ON(out_sgs + in_sgs > ARRAY_SIZE(sgs));
 509         err = virtqueue_add_sgs(chan->vq, sgs, out_sgs, in_sgs, req,
 510                                 GFP_ATOMIC);
 511         if (err < 0) {
 512                 if (err == -ENOSPC) {
 513                         chan->ring_bufs_avail = 0;
 514                         spin_unlock_irqrestore(&chan->lock, flags);
 515                         err = wait_event_killable(*chan->vc_wq,
 516                                                   chan->ring_bufs_avail);
 517                         if (err  == -ERESTARTSYS)
 518                                 goto err_out;
 519
 520                         p9_debug(P9_DEBUG_TRANS, "Retry virtio request\n");
 521                         goto req_retry_pinned;
 522                 } else {
 523                         spin_unlock_irqrestore(&chan->lock, flags);
 524                         p9_debug(P9_DEBUG_TRANS,
 525                                  "virtio rpc add_sgs returned failure\n");
 526                         err = -EIO;
 527                         goto err_out;
 528                 }
 529         }
 530         virtqueue_kick(chan->vq);
 531         spin_unlock_irqrestore(&chan->lock, flags);
 532         kicked = 1;
 533         p9_debug(P9_DEBUG_TRANS, "virtio request kicked\n");
 534         err = wait_event_killable(req->wq,
 535                                   READ_ONCE(req->status) >= REQ_STATUS_RCVD);
 536         // RERROR needs reply (== error string) in static data
 537         if (READ_ONCE(req->status) == REQ_STATUS_RCVD &&
 538             unlikely(req->rc.sdata[4] == P9_RERROR))
 539                 handle_rerror(req, in_hdr_len, offs, in_pages);
 540
 541         /*
 542          * Non kernel buffers are pinned, unpin them
 543          */
 544 err_out:
 545         if (need_drop) {
 546                 if (in_pages) {
 547                         p9_release_pages(in_pages, in_nr_pages);
 548                         atomic_sub(in_nr_pages, &vp_pinned);
 549                 }
 550                 if (out_pages) {
 551                         p9_release_pages(out_pages, out_nr_pages);
 552                         atomic_sub(out_nr_pages, &vp_pinned);
 553                 }
 554                 /* wakeup anybody waiting for slots to pin pages */
 555                 wake_up(&vp_wq);
 556         }
 557         kvfree(in_pages);
 558         kvfree(out_pages);
 559         if (!kicked) {
 560                 /* reply won't come */
 561                 p9_req_put(client, req);
 562         }
 563         return err;
 564 }
 565
 566 static ssize_t p9_mount_tag_show(struct device *dev,
 567                                 struct device_attribute *attr, char *buf)
 568 {
 569         struct virtio_chan *chan;
 570         struct virtio_device *vdev;
 571         int tag_len;
 572
 573         vdev = dev_to_virtio(dev);
 574         chan = vdev->priv;
 575         tag_len = strlen(chan->tag);
 576
 577         memcpy(buf, chan->tag, tag_len + 1);
 578
 579         return tag_len + 1;
 580 }
 581
 582 static DEVICE_ATTR(mount_tag, 0444, p9_mount_tag_show, NULL);
 583
 584 /**
 585  * p9_virtio_probe - probe for existence of 9P virtio channels
 586  * @vdev: virtio device to probe
 587  *
 588  * This probes for existing virtio channels.
 589  *
 590  */
 591
 592 static int p9_virtio_probe(struct virtio_device *vdev)
 593 {
 594         __u16 tag_len;
 595         char *tag;
 596         int err;
 597         struct virtio_chan *chan;
 598
 599         if (!vdev->config->get) {
 600                 dev_err(&vdev->dev, "%s failure: config access disabled\n",
 601                         __func__);
 602                 return -EINVAL;
 603         }
 604
 605         chan = kmalloc(sizeof(struct virtio_chan), GFP_KERNEL);
 606         if (!chan) {
 607                 pr_err("Failed to allocate virtio 9P channel\n");
 608                 err = -ENOMEM;
 609                 goto fail;
 610         }
 611
 612         chan->vdev = vdev;
 613
 614         /* We expect one virtqueue, for requests. */
 615         chan->vq = virtio_find_single_vq(vdev, req_done, "requests");
 616         if (IS_ERR(chan->vq)) {
 617                 err = PTR_ERR(chan->vq);
 618                 goto out_free_chan;
 619         }
 620         chan->vq->vdev->priv = chan;
 621         spin_lock_init(&chan->lock);
 622
 623         sg_init_table(chan->sg, VIRTQUEUE_NUM);
 624
 625         chan->inuse = false;
 626         if (virtio_has_feature(vdev, VIRTIO_9P_MOUNT_TAG)) {
 627                 virtio_cread(vdev, struct virtio_9p_config, tag_len, &tag_len);
 628         } else {
 629                 err = -EINVAL;
 630                 goto out_free_vq;
 631         }
 632         tag = kzalloc(tag_len + 1, GFP_KERNEL);
 633         if (!tag) {
 634                 err = -ENOMEM;
 635                 goto out_free_vq;
 636         }
 637
 638         virtio_cread_bytes(vdev, offsetof(struct virtio_9p_config, tag),
 639                            tag, tag_len);
 640         chan->tag = tag;
 641         err = sysfs_create_file(&(vdev->dev.kobj), &dev_attr_mount_tag.attr);
 642         if (err) {
 643                 goto out_free_tag;
 644         }
 645         chan->vc_wq = kmalloc(sizeof(wait_queue_head_t), GFP_KERNEL);
 646         if (!chan->vc_wq) {
 647                 err = -ENOMEM;
 648                 goto out_remove_file;
 649         }
 650         init_waitqueue_head(chan->vc_wq);
 651         chan->ring_bufs_avail = 1;
 652         /* Ceiling limit to avoid denial of service attacks */
 653         chan->p9_max_pages = nr_free_buffer_pages()/4;
 654
 655         virtio_device_ready(vdev);
 656
 657         mutex_lock(&virtio_9p_lock);
 658         list_add_tail(&chan->chan_list, &virtio_chan_list);
 659         mutex_unlock(&virtio_9p_lock);
 660
 661         /* Let udev rules use the new mount_tag attribute. */
 662         kobject_uevent(&(vdev->dev.kobj), KOBJ_CHANGE);
 663
 664         return 0;
 665
 666 out_remove_file:
 667         sysfs_remove_file(&vdev->dev.kobj, &dev_attr_mount_tag.attr);
 668 out_free_tag:
 669         kfree(tag);
 670 out_free_vq:
 671         vdev->config->del_vqs(vdev);
 672 out_free_chan:
 673         kfree(chan);
 674 fail:
 675         return err;
 676 }
 677
 678
 679 /**
 680  * p9_virtio_create - allocate a new virtio channel
 681  * @client: client instance invoking this transport
 682  * @devname: string identifying the channel to connect to (unused)
 683  * @args: args passed from sys_mount() for per-transport options (unused)
 684  *
 685  * This sets up a transport channel for 9p communication.  Right now
 686  * we only match the first available channel, but eventually we could look up
 687  * alternate channels by matching devname versus a virtio_config entry.
 688  * We use a simple reference count mechanism to ensure that only a single
 689  * mount has a channel open at a time.
 690  *
 691  */
 692
 693 static int
 694 p9_virtio_create(struct p9_client *client, const char *devname, char *args)
 695 {
 696         struct virtio_chan *chan;
 697         int ret = -ENOENT;
 698         int found = 0;
 699
 700         if (devname == NULL)
 701                 return -EINVAL;
 702
 703         mutex_lock(&virtio_9p_lock);
 704         list_for_each_entry(chan, &virtio_chan_list, chan_list) {
 705                 if (!strcmp(devname, chan->tag)) {
 706                         if (!chan->inuse) {
 707                                 chan->inuse = true;
 708                                 found = 1;
 709                                 break;
 710                         }
 711                         ret = -EBUSY;
 712                 }
 713         }
 714         mutex_unlock(&virtio_9p_lock);
 715
 716         if (!found) {
 717                 pr_err("no channels available for device %s\n", devname);
 718                 return ret;
 719         }
 720
 721         client->trans = (void *)chan;
 722         client->status = Connected;
 723         chan->client = client;
 724
 725         return 0;
 726 }
 727
 728 /**
 729  * p9_virtio_remove - clean up resources associated with a virtio device
 730  * @vdev: virtio device to remove
 731  *
 732  */
 733
 734 static void p9_virtio_remove(struct virtio_device *vdev)
 735 {
 736         struct virtio_chan *chan = vdev->priv;
 737         unsigned long warning_time;
 738
 739         mutex_lock(&virtio_9p_lock);
 740
 741         /* Remove self from list so we don't get new users. */
 742         list_del(&chan->chan_list);
 743         warning_time = jiffies;
 744
 745         /* Wait for existing users to close. */
 746         while (chan->inuse) {
 747                 mutex_unlock(&virtio_9p_lock);
 748                 msleep(250);
 749                 if (time_after(jiffies, warning_time + 10 * HZ)) {
 750                         dev_emerg(&vdev->dev,
 751                                   "p9_virtio_remove: waiting for device in use.\n");
 752                         warning_time = jiffies;
 753                 }
 754                 mutex_lock(&virtio_9p_lock);
 755         }
 756
 757         mutex_unlock(&virtio_9p_lock);
 758
 759         virtio_reset_device(vdev);
 760         vdev->config->del_vqs(vdev);
 761
 762         sysfs_remove_file(&(vdev->dev.kobj), &dev_attr_mount_tag.attr);
 763         kobject_uevent(&(vdev->dev.kobj), KOBJ_CHANGE);
 764         kfree(chan->tag);
 765         kfree(chan->vc_wq);
 766         kfree(chan);
 767
 768 }
 769
 770 static struct virtio_device_id id_table[] = {
 771         { VIRTIO_ID_9P, VIRTIO_DEV_ANY_ID },
 772         { 0 },
 773 };
 774
 775 static unsigned int features[] = {
 776         VIRTIO_9P_MOUNT_TAG,
 777 };
 778
 779 /* The standard "struct lguest_driver": */
 780 static struct virtio_driver p9_virtio_drv = {
 781         .feature_table  = features,
 782         .feature_table_size = ARRAY_SIZE(features),
 783         .driver.name    = KBUILD_MODNAME,
 784         .id_table       = id_table,
 785         .probe          = p9_virtio_probe,
 786         .remove         = p9_virtio_remove,
 787 };
 788
 789 static struct p9_trans_module p9_virtio_trans = {
 790         .name = "virtio",
 791         .create = p9_virtio_create,
 792         .close = p9_virtio_close,
 793         .request = p9_virtio_request,
 794         .zc_request = p9_virtio_zc_request,
 795         .cancel = p9_virtio_cancel,
 796         .cancelled = p9_virtio_cancelled,
 797         /*
 798          * We leave one entry for input and one entry for response
 799          * headers. We also skip one more entry to accommodate, address
 800          * that are not at page boundary, that can result in an extra
 801          * page in zero copy.
 802          */
 803         .maxsize = PAGE_SIZE * (VIRTQUEUE_NUM - 3),
 804         .pooled_rbuffers = false,
 805         .def = 1,
 806         .owner = THIS_MODULE,
 807 };
 808
 809 /* The standard init function */
 810 static int __init p9_virtio_init(void)
 811 {
 812         int rc;
 813
 814         INIT_LIST_HEAD(&virtio_chan_list);
 815
 816         v9fs_register_trans(&p9_virtio_trans);
 817         rc = register_virtio_driver(&p9_virtio_drv);
 818         if (rc)
 819                 v9fs_unregister_trans(&p9_virtio_trans);
 820
 821         return rc;
 822 }
 823
 824 static void __exit p9_virtio_cleanup(void)
 825 {
 826         unregister_virtio_driver(&p9_virtio_drv);
 827         v9fs_unregister_trans(&p9_virtio_trans);
 828 }
 829
 830 module_init(p9_virtio_init);
 831 module_exit(p9_virtio_cleanup);
 832 MODULE_ALIAS_9P("virtio");
 833
 834 MODULE_DEVICE_TABLE(virtio, id_table);
 835 MODULE_AUTHOR("Eric Van Hensbergen <ericvh@gmail.com>");
 836 MODULE_DESCRIPTION("Virtio 9p Transport");
 837 MODULE_LICENSE("GPL");