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TOMOYO Linux Cross Reference
Linux/net/9p/trans_virtio.c

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  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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 30 
 31 #include <linux/in.h>
 32 #include <linux/module.h>
 33 #include <linux/net.h>
 34 #include <linux/ipv6.h>
 35 #include <linux/errno.h>
 36 #include <linux/kernel.h>
 37 #include <linux/un.h>
 38 #include <linux/uaccess.h>
 39 #include <linux/inet.h>
 40 #include <linux/idr.h>
 41 #include <linux/file.h>
 42 #include <linux/highmem.h>
 43 #include <linux/slab.h>
 44 #include <net/9p/9p.h>
 45 #include <linux/parser.h>
 46 #include <net/9p/client.h>
 47 #include <net/9p/transport.h>
 48 #include <linux/scatterlist.h>
 49 #include <linux/swap.h>
 50 #include <linux/virtio.h>
 51 #include <linux/virtio_9p.h>
 52 #include "trans_common.h"
 53 
 54 #define VIRTQUEUE_NUM   128
 55 
 56 /* a single mutex to manage channel initialization and attachment */
 57 static DEFINE_MUTEX(virtio_9p_lock);
 58 static DECLARE_WAIT_QUEUE_HEAD(vp_wq);
 59 static atomic_t vp_pinned = ATOMIC_INIT(0);
 60 
 61 /**
 62  * struct virtio_chan - per-instance transport information
 63  * @initialized: whether the channel is initialized
 64  * @inuse: whether the channel is in use
 65  * @lock: protects multiple elements within this structure
 66  * @client: client instance
 67  * @vdev: virtio dev associated with this channel
 68  * @vq: virtio queue associated with this channel
 69  * @sg: scatter gather list which is used to pack a request (protected?)
 70  *
 71  * We keep all per-channel information in a structure.
 72  * This structure is allocated within the devices dev->mem space.
 73  * A pointer to the structure will get put in the transport private.
 74  *
 75  */
 76 
 77 struct virtio_chan {
 78         bool inuse;
 79 
 80         spinlock_t lock;
 81 
 82         struct p9_client *client;
 83         struct virtio_device *vdev;
 84         struct virtqueue *vq;
 85         int ring_bufs_avail;
 86         wait_queue_head_t *vc_wq;
 87         /* This is global limit. Since we don't have a global structure,
 88          * will be placing it in each channel.
 89          */
 90         unsigned long p9_max_pages;
 91         /* Scatterlist: can be too big for stack. */
 92         struct scatterlist sg[VIRTQUEUE_NUM];
 93 
 94         int tag_len;
 95         /*
 96          * tag name to identify a mount Non-null terminated
 97          */
 98         char *tag;
 99 
100         struct list_head chan_list;
101 };
102 
103 static struct list_head virtio_chan_list;
104 
105 /* How many bytes left in this page. */
106 static unsigned int rest_of_page(void *data)
107 {
108         return PAGE_SIZE - ((unsigned long)data % PAGE_SIZE);
109 }
110 
111 /**
112  * p9_virtio_close - reclaim resources of a channel
113  * @client: client instance
114  *
115  * This reclaims a channel by freeing its resources and
116  * reseting its inuse flag.
117  *
118  */
119 
120 static void p9_virtio_close(struct p9_client *client)
121 {
122         struct virtio_chan *chan = client->trans;
123 
124         mutex_lock(&virtio_9p_lock);
125         if (chan)
126                 chan->inuse = false;
127         mutex_unlock(&virtio_9p_lock);
128 }
129 
130 /**
131  * req_done - callback which signals activity from the server
132  * @vq: virtio queue activity was received on
133  *
134  * This notifies us that the server has triggered some activity
135  * on the virtio channel - most likely a response to request we
136  * sent.  Figure out which requests now have responses and wake up
137  * those threads.
138  *
139  * Bugs: could do with some additional sanity checking, but appears to work.
140  *
141  */
142 
143 static void req_done(struct virtqueue *vq)
144 {
145         struct virtio_chan *chan = vq->vdev->priv;
146         struct p9_fcall *rc;
147         unsigned int len;
148         struct p9_req_t *req;
149         unsigned long flags;
150 
151         p9_debug(P9_DEBUG_TRANS, ": request done\n");
152 
153         while (1) {
154                 spin_lock_irqsave(&chan->lock, flags);
155                 rc = virtqueue_get_buf(chan->vq, &len);
156                 if (rc == NULL) {
157                         spin_unlock_irqrestore(&chan->lock, flags);
158                         break;
159                 }
160                 chan->ring_bufs_avail = 1;
161                 spin_unlock_irqrestore(&chan->lock, flags);
162                 /* Wakeup if anyone waiting for VirtIO ring space. */
163                 wake_up(chan->vc_wq);
164                 p9_debug(P9_DEBUG_TRANS, ": rc %p\n", rc);
165                 p9_debug(P9_DEBUG_TRANS, ": lookup tag %d\n", rc->tag);
166                 req = p9_tag_lookup(chan->client, rc->tag);
167                 if (len)
168                         p9_client_cb(chan->client, req, REQ_STATUS_RCVD);
169         }
170 }
171 
172 /**
173  * pack_sg_list - pack a scatter gather list from a linear buffer
174  * @sg: scatter/gather list to pack into
175  * @start: which segment of the sg_list to start at
176  * @limit: maximum segment to pack data to
177  * @data: data to pack into scatter/gather list
178  * @count: amount of data to pack into the scatter/gather list
179  *
180  * sg_lists have multiple segments of various sizes.  This will pack
181  * arbitrary data into an existing scatter gather list, segmenting the
182  * data as necessary within constraints.
183  *
184  */
185 
186 static int pack_sg_list(struct scatterlist *sg, int start,
187                         int limit, char *data, int count)
188 {
189         int s;
190         int index = start;
191 
192         while (count) {
193                 s = rest_of_page(data);
194                 if (s > count)
195                         s = count;
196                 BUG_ON(index >= limit);
197                 /* Make sure we don't terminate early. */
198                 sg_unmark_end(&sg[index]);
199                 sg_set_buf(&sg[index++], data, s);
200                 count -= s;
201                 data += s;
202         }
203         if (index-start)
204                 sg_mark_end(&sg[index - 1]);
205         return index-start;
206 }
207 
208 /* We don't currently allow canceling of virtio requests */
209 static int p9_virtio_cancel(struct p9_client *client, struct p9_req_t *req)
210 {
211         return 1;
212 }
213 
214 /**
215  * pack_sg_list_p - Just like pack_sg_list. Instead of taking a buffer,
216  * this takes a list of pages.
217  * @sg: scatter/gather list to pack into
218  * @start: which segment of the sg_list to start at
219  * @pdata: a list of pages to add into sg.
220  * @nr_pages: number of pages to pack into the scatter/gather list
221  * @data: data to pack into scatter/gather list
222  * @count: amount of data to pack into the scatter/gather list
223  */
224 static int
225 pack_sg_list_p(struct scatterlist *sg, int start, int limit,
226                struct page **pdata, int nr_pages, char *data, int count)
227 {
228         int i = 0, s;
229         int data_off;
230         int index = start;
231 
232         BUG_ON(nr_pages > (limit - start));
233         /*
234          * if the first page doesn't start at
235          * page boundary find the offset
236          */
237         data_off = offset_in_page(data);
238         while (nr_pages) {
239                 s = rest_of_page(data);
240                 if (s > count)
241                         s = count;
242                 BUG_ON(index >= limit);
243                 /* Make sure we don't terminate early. */
244                 sg_unmark_end(&sg[index]);
245                 sg_set_page(&sg[index++], pdata[i++], s, data_off);
246                 data_off = 0;
247                 data += s;
248                 count -= s;
249                 nr_pages--;
250         }
251 
252         if (index-start)
253                 sg_mark_end(&sg[index - 1]);
254         return index - start;
255 }
256 
257 /**
258  * p9_virtio_request - issue a request
259  * @client: client instance issuing the request
260  * @req: request to be issued
261  *
262  */
263 
264 static int
265 p9_virtio_request(struct p9_client *client, struct p9_req_t *req)
266 {
267         int err;
268         int in, out, out_sgs, in_sgs;
269         unsigned long flags;
270         struct virtio_chan *chan = client->trans;
271         struct scatterlist *sgs[2];
272 
273         p9_debug(P9_DEBUG_TRANS, "9p debug: virtio request\n");
274 
275         req->status = REQ_STATUS_SENT;
276 req_retry:
277         spin_lock_irqsave(&chan->lock, flags);
278 
279         out_sgs = in_sgs = 0;
280         /* Handle out VirtIO ring buffers */
281         out = pack_sg_list(chan->sg, 0,
282                            VIRTQUEUE_NUM, req->tc->sdata, req->tc->size);
283         if (out)
284                 sgs[out_sgs++] = chan->sg;
285 
286         in = pack_sg_list(chan->sg, out,
287                           VIRTQUEUE_NUM, req->rc->sdata, req->rc->capacity);
288         if (in)
289                 sgs[out_sgs + in_sgs++] = chan->sg + out;
290 
291         err = virtqueue_add_sgs(chan->vq, sgs, out_sgs, in_sgs, req->tc,
292                                 GFP_ATOMIC);
293         if (err < 0) {
294                 if (err == -ENOSPC) {
295                         chan->ring_bufs_avail = 0;
296                         spin_unlock_irqrestore(&chan->lock, flags);
297                         err = wait_event_killable(*chan->vc_wq,
298                                                   chan->ring_bufs_avail);
299                         if (err  == -ERESTARTSYS)
300                                 return err;
301 
302                         p9_debug(P9_DEBUG_TRANS, "Retry virtio request\n");
303                         goto req_retry;
304                 } else {
305                         spin_unlock_irqrestore(&chan->lock, flags);
306                         p9_debug(P9_DEBUG_TRANS,
307                                  "virtio rpc add_sgs returned failure\n");
308                         return -EIO;
309                 }
310         }
311         virtqueue_kick(chan->vq);
312         spin_unlock_irqrestore(&chan->lock, flags);
313 
314         p9_debug(P9_DEBUG_TRANS, "virtio request kicked\n");
315         return 0;
316 }
317 
318 static int p9_get_mapped_pages(struct virtio_chan *chan,
319                                struct page **pages, char *data,
320                                int nr_pages, int write, int kern_buf)
321 {
322         int err;
323         if (!kern_buf) {
324                 /*
325                  * We allow only p9_max_pages pinned. We wait for the
326                  * Other zc request to finish here
327                  */
328                 if (atomic_read(&vp_pinned) >= chan->p9_max_pages) {
329                         err = wait_event_killable(vp_wq,
330                               (atomic_read(&vp_pinned) < chan->p9_max_pages));
331                         if (err == -ERESTARTSYS)
332                                 return err;
333                 }
334                 err = p9_payload_gup(data, &nr_pages, pages, write);
335                 if (err < 0)
336                         return err;
337                 atomic_add(nr_pages, &vp_pinned);
338         } else {
339                 /* kernel buffer, no need to pin pages */
340                 int s, index = 0;
341                 int count = nr_pages;
342                 while (nr_pages) {
343                         s = rest_of_page(data);
344                         if (is_vmalloc_addr(data))
345                                 pages[index++] = vmalloc_to_page(data);
346                         else
347                                 pages[index++] = kmap_to_page(data);
348                         data += s;
349                         nr_pages--;
350                 }
351                 nr_pages = count;
352         }
353         return nr_pages;
354 }
355 
356 /**
357  * p9_virtio_zc_request - issue a zero copy request
358  * @client: client instance issuing the request
359  * @req: request to be issued
360  * @uidata: user bffer that should be ued for zero copy read
361  * @uodata: user buffer that shoud be user for zero copy write
362  * @inlen: read buffer size
363  * @olen: write buffer size
364  * @hdrlen: reader header size, This is the size of response protocol data
365  *
366  */
367 static int
368 p9_virtio_zc_request(struct p9_client *client, struct p9_req_t *req,
369                      char *uidata, char *uodata, int inlen,
370                      int outlen, int in_hdr_len, int kern_buf)
371 {
372         int in, out, err, out_sgs, in_sgs;
373         unsigned long flags;
374         int in_nr_pages = 0, out_nr_pages = 0;
375         struct page **in_pages = NULL, **out_pages = NULL;
376         struct virtio_chan *chan = client->trans;
377         struct scatterlist *sgs[4];
378 
379         p9_debug(P9_DEBUG_TRANS, "virtio request\n");
380 
381         if (uodata) {
382                 __le32 sz;
383                 out_nr_pages = p9_nr_pages(uodata, outlen);
384                 out_pages = kmalloc(sizeof(struct page *) * out_nr_pages,
385                                     GFP_NOFS);
386                 if (!out_pages) {
387                         err = -ENOMEM;
388                         goto err_out;
389                 }
390                 out_nr_pages = p9_get_mapped_pages(chan, out_pages, uodata,
391                                                    out_nr_pages, 0, kern_buf);
392                 if (out_nr_pages < 0) {
393                         err = out_nr_pages;
394                         kfree(out_pages);
395                         out_pages = NULL;
396                         goto err_out;
397                 }
398                 /* The size field of the message must include the length of the
399                  * header and the length of the data.  We didn't actually know
400                  * the length of the data until this point so add it in now.
401                  */
402                 sz = cpu_to_le32(req->tc->size + outlen);
403                 memcpy(&req->tc->sdata[0], &sz, sizeof(sz));
404         }
405         if (uidata) {
406                 in_nr_pages = p9_nr_pages(uidata, inlen);
407                 in_pages = kmalloc(sizeof(struct page *) * in_nr_pages,
408                                    GFP_NOFS);
409                 if (!in_pages) {
410                         err = -ENOMEM;
411                         goto err_out;
412                 }
413                 in_nr_pages = p9_get_mapped_pages(chan, in_pages, uidata,
414                                                   in_nr_pages, 1, kern_buf);
415                 if (in_nr_pages < 0) {
416                         err = in_nr_pages;
417                         kfree(in_pages);
418                         in_pages = NULL;
419                         goto err_out;
420                 }
421         }
422         req->status = REQ_STATUS_SENT;
423 req_retry_pinned:
424         spin_lock_irqsave(&chan->lock, flags);
425 
426         out_sgs = in_sgs = 0;
427 
428         /* out data */
429         out = pack_sg_list(chan->sg, 0,
430                            VIRTQUEUE_NUM, req->tc->sdata, req->tc->size);
431 
432         if (out)
433                 sgs[out_sgs++] = chan->sg;
434 
435         if (out_pages) {
436                 sgs[out_sgs++] = chan->sg + out;
437                 out += pack_sg_list_p(chan->sg, out, VIRTQUEUE_NUM,
438                                       out_pages, out_nr_pages, uodata, outlen);
439         }
440                 
441         /*
442          * Take care of in data
443          * For example TREAD have 11.
444          * 11 is the read/write header = PDU Header(7) + IO Size (4).
445          * Arrange in such a way that server places header in the
446          * alloced memory and payload onto the user buffer.
447          */
448         in = pack_sg_list(chan->sg, out,
449                           VIRTQUEUE_NUM, req->rc->sdata, in_hdr_len);
450         if (in)
451                 sgs[out_sgs + in_sgs++] = chan->sg + out;
452 
453         if (in_pages) {
454                 sgs[out_sgs + in_sgs++] = chan->sg + out + in;
455                 in += pack_sg_list_p(chan->sg, out + in, VIRTQUEUE_NUM,
456                                      in_pages, in_nr_pages, uidata, inlen);
457         }
458 
459         BUG_ON(out_sgs + in_sgs > ARRAY_SIZE(sgs));
460         err = virtqueue_add_sgs(chan->vq, sgs, out_sgs, in_sgs, req->tc,
461                                 GFP_ATOMIC);
462         if (err < 0) {
463                 if (err == -ENOSPC) {
464                         chan->ring_bufs_avail = 0;
465                         spin_unlock_irqrestore(&chan->lock, flags);
466                         err = wait_event_killable(*chan->vc_wq,
467                                                   chan->ring_bufs_avail);
468                         if (err  == -ERESTARTSYS)
469                                 goto err_out;
470 
471                         p9_debug(P9_DEBUG_TRANS, "Retry virtio request\n");
472                         goto req_retry_pinned;
473                 } else {
474                         spin_unlock_irqrestore(&chan->lock, flags);
475                         p9_debug(P9_DEBUG_TRANS,
476                                  "virtio rpc add_sgs returned failure\n");
477                         err = -EIO;
478                         goto err_out;
479                 }
480         }
481         virtqueue_kick(chan->vq);
482         spin_unlock_irqrestore(&chan->lock, flags);
483         p9_debug(P9_DEBUG_TRANS, "virtio request kicked\n");
484         err = wait_event_killable(*req->wq, req->status >= REQ_STATUS_RCVD);
485         /*
486          * Non kernel buffers are pinned, unpin them
487          */
488 err_out:
489         if (!kern_buf) {
490                 if (in_pages) {
491                         p9_release_pages(in_pages, in_nr_pages);
492                         atomic_sub(in_nr_pages, &vp_pinned);
493                 }
494                 if (out_pages) {
495                         p9_release_pages(out_pages, out_nr_pages);
496                         atomic_sub(out_nr_pages, &vp_pinned);
497                 }
498                 /* wakeup anybody waiting for slots to pin pages */
499                 wake_up(&vp_wq);
500         }
501         kfree(in_pages);
502         kfree(out_pages);
503         return err;
504 }
505 
506 static ssize_t p9_mount_tag_show(struct device *dev,
507                                 struct device_attribute *attr, char *buf)
508 {
509         struct virtio_chan *chan;
510         struct virtio_device *vdev;
511 
512         vdev = dev_to_virtio(dev);
513         chan = vdev->priv;
514 
515         return snprintf(buf, chan->tag_len + 1, "%s", chan->tag);
516 }
517 
518 static DEVICE_ATTR(mount_tag, 0444, p9_mount_tag_show, NULL);
519 
520 /**
521  * p9_virtio_probe - probe for existence of 9P virtio channels
522  * @vdev: virtio device to probe
523  *
524  * This probes for existing virtio channels.
525  *
526  */
527 
528 static int p9_virtio_probe(struct virtio_device *vdev)
529 {
530         __u16 tag_len;
531         char *tag;
532         int err;
533         struct virtio_chan *chan;
534 
535         chan = kmalloc(sizeof(struct virtio_chan), GFP_KERNEL);
536         if (!chan) {
537                 pr_err("Failed to allocate virtio 9P channel\n");
538                 err = -ENOMEM;
539                 goto fail;
540         }
541 
542         chan->vdev = vdev;
543 
544         /* We expect one virtqueue, for requests. */
545         chan->vq = virtio_find_single_vq(vdev, req_done, "requests");
546         if (IS_ERR(chan->vq)) {
547                 err = PTR_ERR(chan->vq);
548                 goto out_free_vq;
549         }
550         chan->vq->vdev->priv = chan;
551         spin_lock_init(&chan->lock);
552 
553         sg_init_table(chan->sg, VIRTQUEUE_NUM);
554 
555         chan->inuse = false;
556         if (virtio_has_feature(vdev, VIRTIO_9P_MOUNT_TAG)) {
557                 virtio_cread(vdev, struct virtio_9p_config, tag_len, &tag_len);
558         } else {
559                 err = -EINVAL;
560                 goto out_free_vq;
561         }
562         tag = kmalloc(tag_len, GFP_KERNEL);
563         if (!tag) {
564                 err = -ENOMEM;
565                 goto out_free_vq;
566         }
567 
568         virtio_cread_bytes(vdev, offsetof(struct virtio_9p_config, tag),
569                            tag, tag_len);
570         chan->tag = tag;
571         chan->tag_len = tag_len;
572         err = sysfs_create_file(&(vdev->dev.kobj), &dev_attr_mount_tag.attr);
573         if (err) {
574                 goto out_free_tag;
575         }
576         chan->vc_wq = kmalloc(sizeof(wait_queue_head_t), GFP_KERNEL);
577         if (!chan->vc_wq) {
578                 err = -ENOMEM;
579                 goto out_free_tag;
580         }
581         init_waitqueue_head(chan->vc_wq);
582         chan->ring_bufs_avail = 1;
583         /* Ceiling limit to avoid denial of service attacks */
584         chan->p9_max_pages = nr_free_buffer_pages()/4;
585 
586         mutex_lock(&virtio_9p_lock);
587         list_add_tail(&chan->chan_list, &virtio_chan_list);
588         mutex_unlock(&virtio_9p_lock);
589 
590         /* Let udev rules use the new mount_tag attribute. */
591         kobject_uevent(&(vdev->dev.kobj), KOBJ_CHANGE);
592 
593         return 0;
594 
595 out_free_tag:
596         kfree(tag);
597 out_free_vq:
598         vdev->config->del_vqs(vdev);
599         kfree(chan);
600 fail:
601         return err;
602 }
603 
604 
605 /**
606  * p9_virtio_create - allocate a new virtio channel
607  * @client: client instance invoking this transport
608  * @devname: string identifying the channel to connect to (unused)
609  * @args: args passed from sys_mount() for per-transport options (unused)
610  *
611  * This sets up a transport channel for 9p communication.  Right now
612  * we only match the first available channel, but eventually we couldlook up
613  * alternate channels by matching devname versus a virtio_config entry.
614  * We use a simple reference count mechanism to ensure that only a single
615  * mount has a channel open at a time.
616  *
617  */
618 
619 static int
620 p9_virtio_create(struct p9_client *client, const char *devname, char *args)
621 {
622         struct virtio_chan *chan;
623         int ret = -ENOENT;
624         int found = 0;
625 
626         if (devname == NULL)
627                 return -EINVAL;
628 
629         mutex_lock(&virtio_9p_lock);
630         list_for_each_entry(chan, &virtio_chan_list, chan_list) {
631                 if (!strncmp(devname, chan->tag, chan->tag_len) &&
632                     strlen(devname) == chan->tag_len) {
633                         if (!chan->inuse) {
634                                 chan->inuse = true;
635                                 found = 1;
636                                 break;
637                         }
638                         ret = -EBUSY;
639                 }
640         }
641         mutex_unlock(&virtio_9p_lock);
642 
643         if (!found) {
644                 pr_err("no channels available\n");
645                 return ret;
646         }
647 
648         client->trans = (void *)chan;
649         client->status = Connected;
650         chan->client = client;
651 
652         return 0;
653 }
654 
655 /**
656  * p9_virtio_remove - clean up resources associated with a virtio device
657  * @vdev: virtio device to remove
658  *
659  */
660 
661 static void p9_virtio_remove(struct virtio_device *vdev)
662 {
663         struct virtio_chan *chan = vdev->priv;
664 
665         if (chan->inuse)
666                 p9_virtio_close(chan->client);
667         vdev->config->del_vqs(vdev);
668 
669         mutex_lock(&virtio_9p_lock);
670         list_del(&chan->chan_list);
671         mutex_unlock(&virtio_9p_lock);
672         sysfs_remove_file(&(vdev->dev.kobj), &dev_attr_mount_tag.attr);
673         kobject_uevent(&(vdev->dev.kobj), KOBJ_CHANGE);
674         kfree(chan->tag);
675         kfree(chan->vc_wq);
676         kfree(chan);
677 
678 }
679 
680 static struct virtio_device_id id_table[] = {
681         { VIRTIO_ID_9P, VIRTIO_DEV_ANY_ID },
682         { 0 },
683 };
684 
685 static unsigned int features[] = {
686         VIRTIO_9P_MOUNT_TAG,
687 };
688 
689 /* The standard "struct lguest_driver": */
690 static struct virtio_driver p9_virtio_drv = {
691         .feature_table  = features,
692         .feature_table_size = ARRAY_SIZE(features),
693         .driver.name    = KBUILD_MODNAME,
694         .driver.owner   = THIS_MODULE,
695         .id_table       = id_table,
696         .probe          = p9_virtio_probe,
697         .remove         = p9_virtio_remove,
698 };
699 
700 static struct p9_trans_module p9_virtio_trans = {
701         .name = "virtio",
702         .create = p9_virtio_create,
703         .close = p9_virtio_close,
704         .request = p9_virtio_request,
705         .zc_request = p9_virtio_zc_request,
706         .cancel = p9_virtio_cancel,
707         /*
708          * We leave one entry for input and one entry for response
709          * headers. We also skip one more entry to accomodate, address
710          * that are not at page boundary, that can result in an extra
711          * page in zero copy.
712          */
713         .maxsize = PAGE_SIZE * (VIRTQUEUE_NUM - 3),
714         .def = 1,
715         .owner = THIS_MODULE,
716 };
717 
718 /* The standard init function */
719 static int __init p9_virtio_init(void)
720 {
721         int rc;
722 
723         INIT_LIST_HEAD(&virtio_chan_list);
724 
725         v9fs_register_trans(&p9_virtio_trans);
726         rc = register_virtio_driver(&p9_virtio_drv);
727         if (rc)
728                 v9fs_unregister_trans(&p9_virtio_trans);
729 
730         return rc;
731 }
732 
733 static void __exit p9_virtio_cleanup(void)
734 {
735         unregister_virtio_driver(&p9_virtio_drv);
736         v9fs_unregister_trans(&p9_virtio_trans);
737 }
738 
739 module_init(p9_virtio_init);
740 module_exit(p9_virtio_cleanup);
741 
742 MODULE_DEVICE_TABLE(virtio, id_table);
743 MODULE_AUTHOR("Eric Van Hensbergen <ericvh@gmail.com>");
744 MODULE_DESCRIPTION("Virtio 9p Transport");
745 MODULE_LICENSE("GPL");
746 

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