2 * The Virtio 9p transport driver
4 * This is a block based transport driver based on the lguest block driver
7 * Copyright (C) 2007, 2008 Eric Van Hensbergen, IBM Corporation
9 * Based on virtio console driver
10 * Copyright (C) 2006, 2007 Rusty Russell, IBM Corporation
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.
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.
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
29 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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>
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"
54 #define VIRTQUEUE_NUM 128
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);
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?)
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.
81 struct p9_client *client;
82 struct virtio_device *vdev;
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.
89 unsigned long p9_max_pages;
90 /* Scatterlist: can be too big for stack. */
91 struct scatterlist sg[VIRTQUEUE_NUM];
93 * tag name to identify a mount null terminated
97 struct list_head chan_list;
100 static struct list_head virtio_chan_list;
102 /* How many bytes left in this page. */
103 static unsigned int rest_of_page(void *data)
105 return PAGE_SIZE - offset_in_page(data);
109 * p9_virtio_close - reclaim resources of a channel
110 * @client: client instance
112 * This reclaims a channel by freeing its resources and
113 * reseting its inuse flag.
117 static void p9_virtio_close(struct p9_client *client)
119 struct virtio_chan *chan = client->trans;
121 mutex_lock(&virtio_9p_lock);
124 mutex_unlock(&virtio_9p_lock);
128 * req_done - callback which signals activity from the server
129 * @vq: virtio queue activity was received on
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
136 * Bugs: could do with some additional sanity checking, but appears to work.
140 static void req_done(struct virtqueue *vq)
142 struct virtio_chan *chan = vq->vdev->priv;
144 struct p9_req_t *req;
145 bool need_wakeup = false;
148 p9_debug(P9_DEBUG_TRANS, ": request done\n");
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;
159 p9_client_cb(chan->client, req, REQ_STATUS_RCVD);
162 spin_unlock_irqrestore(&chan->lock, flags);
163 /* Wakeup if anyone waiting for VirtIO ring space. */
165 wake_up(chan->vc_wq);
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
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.
182 static int pack_sg_list(struct scatterlist *sg, int start,
183 int limit, char *data, int count)
189 s = rest_of_page(data);
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);
200 sg_mark_end(&sg[index - 1]);
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)
210 /* Reply won't come, so drop req ref */
211 static int p9_virtio_cancelled(struct p9_client *client, struct p9_req_t *req)
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
228 pack_sg_list_p(struct scatterlist *sg, int start, int limit,
229 struct page **pdata, int nr_pages, size_t offs, int count)
235 BUG_ON(nr_pages > (limit - start));
237 * if the first page doesn't start at
238 * page boundary find the offset
241 s = PAGE_SIZE - data_off;
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);
254 sg_mark_end(&sg[index - 1]);
255 return index - start;
259 * p9_virtio_request - issue a request
260 * @client: client instance issuing the request
261 * @req: request to be issued
266 p9_virtio_request(struct p9_client *client, struct p9_req_t *req)
269 int in, out, out_sgs, in_sgs;
271 struct virtio_chan *chan = client->trans;
272 struct scatterlist *sgs[2];
274 p9_debug(P9_DEBUG_TRANS, "9p debug: virtio request\n");
276 req->status = REQ_STATUS_SENT;
278 spin_lock_irqsave(&chan->lock, flags);
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);
285 sgs[out_sgs++] = chan->sg;
287 in = pack_sg_list(chan->sg, out,
288 VIRTQUEUE_NUM, req->rc.sdata, req->rc.capacity);
290 sgs[out_sgs + in_sgs++] = chan->sg + out;
292 err = virtqueue_add_sgs(chan->vq, sgs, out_sgs, in_sgs, req,
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)
303 p9_debug(P9_DEBUG_TRANS, "Retry virtio request\n");
306 spin_unlock_irqrestore(&chan->lock, flags);
307 p9_debug(P9_DEBUG_TRANS,
308 "virtio rpc add_sgs returned failure\n");
312 virtqueue_kick(chan->vq);
313 spin_unlock_irqrestore(&chan->lock, flags);
315 p9_debug(P9_DEBUG_TRANS, "virtio request kicked\n");
319 static int p9_get_mapped_pages(struct virtio_chan *chan,
320 struct page ***pages,
321 struct iov_iter *data,
329 if (!iov_iter_count(data))
332 if (!iov_iter_is_kvec(data)) {
335 * We allow only p9_max_pages pinned. We wait for the
336 * Other zc request to finish here
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)
344 n = iov_iter_get_pages_alloc(data, pages, count, offs);
348 nr_pages = DIV_ROUND_UP(n + *offs, PAGE_SIZE);
349 atomic_add(nr_pages, &vp_pinned);
352 /* kernel buffer, no need to pin pages */
357 /* we'd already checked that it's non-empty */
359 len = iov_iter_single_seg_count(data);
361 p = data->kvec->iov_base + data->iov_offset;
364 iov_iter_advance(data, 0);
369 nr_pages = DIV_ROUND_UP((unsigned long)p + len, PAGE_SIZE) -
370 (unsigned long)p / PAGE_SIZE;
372 *pages = kmalloc_array(nr_pages, sizeof(struct page *),
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);
383 (*pages)[index] = kmap_to_page(p);
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
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)
406 int in, out, err, out_sgs, in_sgs;
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];
416 p9_debug(P9_DEBUG_TRANS, "virtio request\n");
420 int n = p9_get_mapped_pages(chan, &out_pages, uodata,
421 outlen, &offs, &need_drop);
426 out_nr_pages = DIV_ROUND_UP(n + offs, PAGE_SIZE);
428 __le32 v = cpu_to_le32(n);
429 memcpy(&req->tc.sdata[req->tc.size - 4], &v, 4);
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.
436 sz = cpu_to_le32(req->tc.size + outlen);
437 memcpy(&req->tc.sdata[0], &sz, sizeof(sz));
439 int n = p9_get_mapped_pages(chan, &in_pages, uidata,
440 inlen, &offs, &need_drop);
445 in_nr_pages = DIV_ROUND_UP(n + offs, PAGE_SIZE);
447 __le32 v = cpu_to_le32(n);
448 memcpy(&req->tc.sdata[req->tc.size - 4], &v, 4);
452 req->status = REQ_STATUS_SENT;
454 spin_lock_irqsave(&chan->lock, flags);
456 out_sgs = in_sgs = 0;
459 out = pack_sg_list(chan->sg, 0,
460 VIRTQUEUE_NUM, req->tc.sdata, req->tc.size);
463 sgs[out_sgs++] = chan->sg;
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);
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.
478 in = pack_sg_list(chan->sg, out,
479 VIRTQUEUE_NUM, req->rc.sdata, in_hdr_len);
481 sgs[out_sgs + in_sgs++] = chan->sg + out;
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);
489 BUG_ON(out_sgs + in_sgs > ARRAY_SIZE(sgs));
490 err = virtqueue_add_sgs(chan->vq, sgs, out_sgs, in_sgs, req,
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)
501 p9_debug(P9_DEBUG_TRANS, "Retry virtio request\n");
502 goto req_retry_pinned;
504 spin_unlock_irqrestore(&chan->lock, flags);
505 p9_debug(P9_DEBUG_TRANS,
506 "virtio rpc add_sgs returned failure\n");
511 virtqueue_kick(chan->vq);
512 spin_unlock_irqrestore(&chan->lock, flags);
514 p9_debug(P9_DEBUG_TRANS, "virtio request kicked\n");
515 err = wait_event_killable(req->wq, req->status >= REQ_STATUS_RCVD);
517 * Non kernel buffers are pinned, unpin them
522 p9_release_pages(in_pages, in_nr_pages);
523 atomic_sub(in_nr_pages, &vp_pinned);
526 p9_release_pages(out_pages, out_nr_pages);
527 atomic_sub(out_nr_pages, &vp_pinned);
529 /* wakeup anybody waiting for slots to pin pages */
535 /* reply won't come */
541 static ssize_t p9_mount_tag_show(struct device *dev,
542 struct device_attribute *attr, char *buf)
544 struct virtio_chan *chan;
545 struct virtio_device *vdev;
548 vdev = dev_to_virtio(dev);
550 tag_len = strlen(chan->tag);
552 memcpy(buf, chan->tag, tag_len + 1);
557 static DEVICE_ATTR(mount_tag, 0444, p9_mount_tag_show, NULL);
560 * p9_virtio_probe - probe for existence of 9P virtio channels
561 * @vdev: virtio device to probe
563 * This probes for existing virtio channels.
567 static int p9_virtio_probe(struct virtio_device *vdev)
572 struct virtio_chan *chan;
574 if (!vdev->config->get) {
575 dev_err(&vdev->dev, "%s failure: config access disabled\n",
580 chan = kmalloc(sizeof(struct virtio_chan), GFP_KERNEL);
582 pr_err("Failed to allocate virtio 9P channel\n");
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);
595 chan->vq->vdev->priv = chan;
596 spin_lock_init(&chan->lock);
598 sg_init_table(chan->sg, VIRTQUEUE_NUM);
601 if (virtio_has_feature(vdev, VIRTIO_9P_MOUNT_TAG)) {
602 virtio_cread(vdev, struct virtio_9p_config, tag_len, &tag_len);
607 tag = kzalloc(tag_len + 1, GFP_KERNEL);
613 virtio_cread_bytes(vdev, offsetof(struct virtio_9p_config, tag),
616 err = sysfs_create_file(&(vdev->dev.kobj), &dev_attr_mount_tag.attr);
620 chan->vc_wq = kmalloc(sizeof(wait_queue_head_t), GFP_KERNEL);
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;
630 virtio_device_ready(vdev);
632 mutex_lock(&virtio_9p_lock);
633 list_add_tail(&chan->chan_list, &virtio_chan_list);
634 mutex_unlock(&virtio_9p_lock);
636 /* Let udev rules use the new mount_tag attribute. */
637 kobject_uevent(&(vdev->dev.kobj), KOBJ_CHANGE);
644 vdev->config->del_vqs(vdev);
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)
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.
667 p9_virtio_create(struct p9_client *client, const char *devname, char *args)
669 struct virtio_chan *chan;
676 mutex_lock(&virtio_9p_lock);
677 list_for_each_entry(chan, &virtio_chan_list, chan_list) {
678 if (!strcmp(devname, chan->tag)) {
687 mutex_unlock(&virtio_9p_lock);
690 pr_err("no channels available for device %s\n", devname);
694 client->trans = (void *)chan;
695 client->status = Connected;
696 chan->client = client;
702 * p9_virtio_remove - clean up resources associated with a virtio device
703 * @vdev: virtio device to remove
707 static void p9_virtio_remove(struct virtio_device *vdev)
709 struct virtio_chan *chan = vdev->priv;
710 unsigned long warning_time;
712 mutex_lock(&virtio_9p_lock);
714 /* Remove self from list so we don't get new users. */
715 list_del(&chan->chan_list);
716 warning_time = jiffies;
718 /* Wait for existing users to close. */
719 while (chan->inuse) {
720 mutex_unlock(&virtio_9p_lock);
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;
727 mutex_lock(&virtio_9p_lock);
730 mutex_unlock(&virtio_9p_lock);
732 vdev->config->reset(vdev);
733 vdev->config->del_vqs(vdev);
735 sysfs_remove_file(&(vdev->dev.kobj), &dev_attr_mount_tag.attr);
736 kobject_uevent(&(vdev->dev.kobj), KOBJ_CHANGE);
743 static struct virtio_device_id id_table[] = {
744 { VIRTIO_ID_9P, VIRTIO_DEV_ANY_ID },
748 static unsigned int features[] = {
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,
763 static struct p9_trans_module p9_virtio_trans = {
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,
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
777 .maxsize = PAGE_SIZE * (VIRTQUEUE_NUM - 3),
779 .owner = THIS_MODULE,
782 /* The standard init function */
783 static int __init p9_virtio_init(void)
785 INIT_LIST_HEAD(&virtio_chan_list);
787 v9fs_register_trans(&p9_virtio_trans);
788 return register_virtio_driver(&p9_virtio_drv);
791 static void __exit p9_virtio_cleanup(void)
793 unregister_virtio_driver(&p9_virtio_drv);
794 v9fs_unregister_trans(&p9_virtio_trans);
797 module_init(p9_virtio_init);
798 module_exit(p9_virtio_cleanup);
800 MODULE_DEVICE_TABLE(virtio, id_table);
801 MODULE_AUTHOR("Eric Van Hensbergen <ericvh@gmail.com>");
802 MODULE_DESCRIPTION("Virtio 9p Transport");
803 MODULE_LICENSE("GPL");