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

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