Use dentry_path() to create full path to inode object
[pohmelfs.git] / drivers / xen / xenbus / xenbus_dev_frontend.c
blob89f76252a16f20e2638ee578faf4e3cbb4a316c6
1 /*
2 * Driver giving user-space access to the kernel's xenbus connection
3 * to xenstore.
5 * Copyright (c) 2005, Christian Limpach
6 * Copyright (c) 2005, Rusty Russell, IBM Corporation
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License version 2
10 * as published by the Free Software Foundation; or, when distributed
11 * separately from the Linux kernel or incorporated into other
12 * software packages, subject to the following license:
14 * Permission is hereby granted, free of charge, to any person obtaining a copy
15 * of this source file (the "Software"), to deal in the Software without
16 * restriction, including without limitation the rights to use, copy, modify,
17 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
18 * and to permit persons to whom the Software is furnished to do so, subject to
19 * the following conditions:
21 * The above copyright notice and this permission notice shall be included in
22 * all copies or substantial portions of the Software.
24 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
25 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
26 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
27 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
28 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
29 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
30 * IN THE SOFTWARE.
32 * Changes:
33 * 2008-10-07 Alex Zeffertt Replaced /proc/xen/xenbus with xenfs filesystem
34 * and /proc/xen compatibility mount point.
35 * Turned xenfs into a loadable module.
38 #include <linux/kernel.h>
39 #include <linux/errno.h>
40 #include <linux/uio.h>
41 #include <linux/notifier.h>
42 #include <linux/wait.h>
43 #include <linux/fs.h>
44 #include <linux/poll.h>
45 #include <linux/mutex.h>
46 #include <linux/sched.h>
47 #include <linux/spinlock.h>
48 #include <linux/mount.h>
49 #include <linux/pagemap.h>
50 #include <linux/uaccess.h>
51 #include <linux/init.h>
52 #include <linux/namei.h>
53 #include <linux/string.h>
54 #include <linux/slab.h>
55 #include <linux/miscdevice.h>
56 #include <linux/module.h>
58 #include "xenbus_comms.h"
60 #include <xen/xenbus.h>
61 #include <xen/xen.h>
62 #include <asm/xen/hypervisor.h>
64 MODULE_LICENSE("GPL");
67 * An element of a list of outstanding transactions, for which we're
68 * still waiting a reply.
70 struct xenbus_transaction_holder {
71 struct list_head list;
72 struct xenbus_transaction handle;
76 * A buffer of data on the queue.
78 struct read_buffer {
79 struct list_head list;
80 unsigned int cons;
81 unsigned int len;
82 char msg[];
85 struct xenbus_file_priv {
87 * msgbuffer_mutex is held while partial requests are built up
88 * and complete requests are acted on. It therefore protects
89 * the "transactions" and "watches" lists, and the partial
90 * request length and buffer.
92 * reply_mutex protects the reply being built up to return to
93 * usermode. It nests inside msgbuffer_mutex but may be held
94 * alone during a watch callback.
96 struct mutex msgbuffer_mutex;
98 /* In-progress transactions */
99 struct list_head transactions;
101 /* Active watches. */
102 struct list_head watches;
104 /* Partial request. */
105 unsigned int len;
106 union {
107 struct xsd_sockmsg msg;
108 char buffer[XENSTORE_PAYLOAD_MAX];
109 } u;
111 /* Response queue. */
112 struct mutex reply_mutex;
113 struct list_head read_buffers;
114 wait_queue_head_t read_waitq;
118 /* Read out any raw xenbus messages queued up. */
119 static ssize_t xenbus_file_read(struct file *filp,
120 char __user *ubuf,
121 size_t len, loff_t *ppos)
123 struct xenbus_file_priv *u = filp->private_data;
124 struct read_buffer *rb;
125 unsigned i;
126 int ret;
128 mutex_lock(&u->reply_mutex);
129 again:
130 while (list_empty(&u->read_buffers)) {
131 mutex_unlock(&u->reply_mutex);
132 if (filp->f_flags & O_NONBLOCK)
133 return -EAGAIN;
135 ret = wait_event_interruptible(u->read_waitq,
136 !list_empty(&u->read_buffers));
137 if (ret)
138 return ret;
139 mutex_lock(&u->reply_mutex);
142 rb = list_entry(u->read_buffers.next, struct read_buffer, list);
143 i = 0;
144 while (i < len) {
145 unsigned sz = min((unsigned)len - i, rb->len - rb->cons);
147 ret = copy_to_user(ubuf + i, &rb->msg[rb->cons], sz);
149 i += sz - ret;
150 rb->cons += sz - ret;
152 if (ret != 0) {
153 if (i == 0)
154 i = -EFAULT;
155 goto out;
158 /* Clear out buffer if it has been consumed */
159 if (rb->cons == rb->len) {
160 list_del(&rb->list);
161 kfree(rb);
162 if (list_empty(&u->read_buffers))
163 break;
164 rb = list_entry(u->read_buffers.next,
165 struct read_buffer, list);
168 if (i == 0)
169 goto again;
171 out:
172 mutex_unlock(&u->reply_mutex);
173 return i;
177 * Add a buffer to the queue. Caller must hold the appropriate lock
178 * if the queue is not local. (Commonly the caller will build up
179 * multiple queued buffers on a temporary local list, and then add it
180 * to the appropriate list under lock once all the buffers have een
181 * successfully allocated.)
183 static int queue_reply(struct list_head *queue, const void *data, size_t len)
185 struct read_buffer *rb;
187 if (len == 0)
188 return 0;
190 rb = kmalloc(sizeof(*rb) + len, GFP_KERNEL);
191 if (rb == NULL)
192 return -ENOMEM;
194 rb->cons = 0;
195 rb->len = len;
197 memcpy(rb->msg, data, len);
199 list_add_tail(&rb->list, queue);
200 return 0;
204 * Free all the read_buffer s on a list.
205 * Caller must have sole reference to list.
207 static void queue_cleanup(struct list_head *list)
209 struct read_buffer *rb;
211 while (!list_empty(list)) {
212 rb = list_entry(list->next, struct read_buffer, list);
213 list_del(list->next);
214 kfree(rb);
218 struct watch_adapter {
219 struct list_head list;
220 struct xenbus_watch watch;
221 struct xenbus_file_priv *dev_data;
222 char *token;
225 static void free_watch_adapter(struct watch_adapter *watch)
227 kfree(watch->watch.node);
228 kfree(watch->token);
229 kfree(watch);
232 static struct watch_adapter *alloc_watch_adapter(const char *path,
233 const char *token)
235 struct watch_adapter *watch;
237 watch = kzalloc(sizeof(*watch), GFP_KERNEL);
238 if (watch == NULL)
239 goto out_fail;
241 watch->watch.node = kstrdup(path, GFP_KERNEL);
242 if (watch->watch.node == NULL)
243 goto out_free;
245 watch->token = kstrdup(token, GFP_KERNEL);
246 if (watch->token == NULL)
247 goto out_free;
249 return watch;
251 out_free:
252 free_watch_adapter(watch);
254 out_fail:
255 return NULL;
258 static void watch_fired(struct xenbus_watch *watch,
259 const char **vec,
260 unsigned int len)
262 struct watch_adapter *adap;
263 struct xsd_sockmsg hdr;
264 const char *path, *token;
265 int path_len, tok_len, body_len, data_len = 0;
266 int ret;
267 LIST_HEAD(staging_q);
269 adap = container_of(watch, struct watch_adapter, watch);
271 path = vec[XS_WATCH_PATH];
272 token = adap->token;
274 path_len = strlen(path) + 1;
275 tok_len = strlen(token) + 1;
276 if (len > 2)
277 data_len = vec[len] - vec[2] + 1;
278 body_len = path_len + tok_len + data_len;
280 hdr.type = XS_WATCH_EVENT;
281 hdr.len = body_len;
283 mutex_lock(&adap->dev_data->reply_mutex);
285 ret = queue_reply(&staging_q, &hdr, sizeof(hdr));
286 if (!ret)
287 ret = queue_reply(&staging_q, path, path_len);
288 if (!ret)
289 ret = queue_reply(&staging_q, token, tok_len);
290 if (!ret && len > 2)
291 ret = queue_reply(&staging_q, vec[2], data_len);
293 if (!ret) {
294 /* success: pass reply list onto watcher */
295 list_splice_tail(&staging_q, &adap->dev_data->read_buffers);
296 wake_up(&adap->dev_data->read_waitq);
297 } else
298 queue_cleanup(&staging_q);
300 mutex_unlock(&adap->dev_data->reply_mutex);
303 static int xenbus_write_transaction(unsigned msg_type,
304 struct xenbus_file_priv *u)
306 int rc;
307 void *reply;
308 struct xenbus_transaction_holder *trans = NULL;
309 LIST_HEAD(staging_q);
311 if (msg_type == XS_TRANSACTION_START) {
312 trans = kmalloc(sizeof(*trans), GFP_KERNEL);
313 if (!trans) {
314 rc = -ENOMEM;
315 goto out;
319 reply = xenbus_dev_request_and_reply(&u->u.msg);
320 if (IS_ERR(reply)) {
321 kfree(trans);
322 rc = PTR_ERR(reply);
323 goto out;
326 if (msg_type == XS_TRANSACTION_START) {
327 trans->handle.id = simple_strtoul(reply, NULL, 0);
329 list_add(&trans->list, &u->transactions);
330 } else if (msg_type == XS_TRANSACTION_END) {
331 list_for_each_entry(trans, &u->transactions, list)
332 if (trans->handle.id == u->u.msg.tx_id)
333 break;
334 BUG_ON(&trans->list == &u->transactions);
335 list_del(&trans->list);
337 kfree(trans);
340 mutex_lock(&u->reply_mutex);
341 rc = queue_reply(&staging_q, &u->u.msg, sizeof(u->u.msg));
342 if (!rc)
343 rc = queue_reply(&staging_q, reply, u->u.msg.len);
344 if (!rc) {
345 list_splice_tail(&staging_q, &u->read_buffers);
346 wake_up(&u->read_waitq);
347 } else {
348 queue_cleanup(&staging_q);
350 mutex_unlock(&u->reply_mutex);
352 kfree(reply);
354 out:
355 return rc;
358 static int xenbus_write_watch(unsigned msg_type, struct xenbus_file_priv *u)
360 struct watch_adapter *watch, *tmp_watch;
361 char *path, *token;
362 int err, rc;
363 LIST_HEAD(staging_q);
365 path = u->u.buffer + sizeof(u->u.msg);
366 token = memchr(path, 0, u->u.msg.len);
367 if (token == NULL) {
368 rc = -EILSEQ;
369 goto out;
371 token++;
372 if (memchr(token, 0, u->u.msg.len - (token - path)) == NULL) {
373 rc = -EILSEQ;
374 goto out;
377 if (msg_type == XS_WATCH) {
378 watch = alloc_watch_adapter(path, token);
379 if (watch == NULL) {
380 rc = -ENOMEM;
381 goto out;
384 watch->watch.callback = watch_fired;
385 watch->dev_data = u;
387 err = register_xenbus_watch(&watch->watch);
388 if (err) {
389 free_watch_adapter(watch);
390 rc = err;
391 goto out;
393 list_add(&watch->list, &u->watches);
394 } else {
395 list_for_each_entry_safe(watch, tmp_watch, &u->watches, list) {
396 if (!strcmp(watch->token, token) &&
397 !strcmp(watch->watch.node, path)) {
398 unregister_xenbus_watch(&watch->watch);
399 list_del(&watch->list);
400 free_watch_adapter(watch);
401 break;
406 /* Success. Synthesize a reply to say all is OK. */
408 struct {
409 struct xsd_sockmsg hdr;
410 char body[3];
411 } __packed reply = {
413 .type = msg_type,
414 .len = sizeof(reply.body)
416 "OK"
419 mutex_lock(&u->reply_mutex);
420 rc = queue_reply(&u->read_buffers, &reply, sizeof(reply));
421 wake_up(&u->read_waitq);
422 mutex_unlock(&u->reply_mutex);
425 out:
426 return rc;
429 static ssize_t xenbus_file_write(struct file *filp,
430 const char __user *ubuf,
431 size_t len, loff_t *ppos)
433 struct xenbus_file_priv *u = filp->private_data;
434 uint32_t msg_type;
435 int rc = len;
436 int ret;
437 LIST_HEAD(staging_q);
440 * We're expecting usermode to be writing properly formed
441 * xenbus messages. If they write an incomplete message we
442 * buffer it up. Once it is complete, we act on it.
446 * Make sure concurrent writers can't stomp all over each
447 * other's messages and make a mess of our partial message
448 * buffer. We don't make any attemppt to stop multiple
449 * writers from making a mess of each other's incomplete
450 * messages; we're just trying to guarantee our own internal
451 * consistency and make sure that single writes are handled
452 * atomically.
454 mutex_lock(&u->msgbuffer_mutex);
456 /* Get this out of the way early to avoid confusion */
457 if (len == 0)
458 goto out;
460 /* Can't write a xenbus message larger we can buffer */
461 if ((len + u->len) > sizeof(u->u.buffer)) {
462 /* On error, dump existing buffer */
463 u->len = 0;
464 rc = -EINVAL;
465 goto out;
468 ret = copy_from_user(u->u.buffer + u->len, ubuf, len);
470 if (ret != 0) {
471 rc = -EFAULT;
472 goto out;
475 /* Deal with a partial copy. */
476 len -= ret;
477 rc = len;
479 u->len += len;
481 /* Return if we haven't got a full message yet */
482 if (u->len < sizeof(u->u.msg))
483 goto out; /* not even the header yet */
485 /* If we're expecting a message that's larger than we can
486 possibly send, dump what we have and return an error. */
487 if ((sizeof(u->u.msg) + u->u.msg.len) > sizeof(u->u.buffer)) {
488 rc = -E2BIG;
489 u->len = 0;
490 goto out;
493 if (u->len < (sizeof(u->u.msg) + u->u.msg.len))
494 goto out; /* incomplete data portion */
497 * OK, now we have a complete message. Do something with it.
500 msg_type = u->u.msg.type;
502 switch (msg_type) {
503 case XS_WATCH:
504 case XS_UNWATCH:
505 /* (Un)Ask for some path to be watched for changes */
506 ret = xenbus_write_watch(msg_type, u);
507 break;
509 default:
510 /* Send out a transaction */
511 ret = xenbus_write_transaction(msg_type, u);
512 break;
514 if (ret != 0)
515 rc = ret;
517 /* Buffered message consumed */
518 u->len = 0;
520 out:
521 mutex_unlock(&u->msgbuffer_mutex);
522 return rc;
525 static int xenbus_file_open(struct inode *inode, struct file *filp)
527 struct xenbus_file_priv *u;
529 if (xen_store_evtchn == 0)
530 return -ENOENT;
532 nonseekable_open(inode, filp);
534 u = kzalloc(sizeof(*u), GFP_KERNEL);
535 if (u == NULL)
536 return -ENOMEM;
538 INIT_LIST_HEAD(&u->transactions);
539 INIT_LIST_HEAD(&u->watches);
540 INIT_LIST_HEAD(&u->read_buffers);
541 init_waitqueue_head(&u->read_waitq);
543 mutex_init(&u->reply_mutex);
544 mutex_init(&u->msgbuffer_mutex);
546 filp->private_data = u;
548 return 0;
551 static int xenbus_file_release(struct inode *inode, struct file *filp)
553 struct xenbus_file_priv *u = filp->private_data;
554 struct xenbus_transaction_holder *trans, *tmp;
555 struct watch_adapter *watch, *tmp_watch;
556 struct read_buffer *rb, *tmp_rb;
559 * No need for locking here because there are no other users,
560 * by definition.
563 list_for_each_entry_safe(trans, tmp, &u->transactions, list) {
564 xenbus_transaction_end(trans->handle, 1);
565 list_del(&trans->list);
566 kfree(trans);
569 list_for_each_entry_safe(watch, tmp_watch, &u->watches, list) {
570 unregister_xenbus_watch(&watch->watch);
571 list_del(&watch->list);
572 free_watch_adapter(watch);
575 list_for_each_entry_safe(rb, tmp_rb, &u->read_buffers, list) {
576 list_del(&rb->list);
577 kfree(rb);
579 kfree(u);
581 return 0;
584 static unsigned int xenbus_file_poll(struct file *file, poll_table *wait)
586 struct xenbus_file_priv *u = file->private_data;
588 poll_wait(file, &u->read_waitq, wait);
589 if (!list_empty(&u->read_buffers))
590 return POLLIN | POLLRDNORM;
591 return 0;
594 const struct file_operations xen_xenbus_fops = {
595 .read = xenbus_file_read,
596 .write = xenbus_file_write,
597 .open = xenbus_file_open,
598 .release = xenbus_file_release,
599 .poll = xenbus_file_poll,
600 .llseek = no_llseek,
602 EXPORT_SYMBOL_GPL(xen_xenbus_fops);
604 static struct miscdevice xenbus_dev = {
605 .minor = MISC_DYNAMIC_MINOR,
606 .name = "xen/xenbus",
607 .fops = &xen_xenbus_fops,
610 static int __init xenbus_init(void)
612 int err;
614 if (!xen_domain())
615 return -ENODEV;
617 err = misc_register(&xenbus_dev);
618 if (err)
619 printk(KERN_ERR "Could not register xenbus frontend device\n");
620 return err;
623 static void __exit xenbus_exit(void)
625 misc_deregister(&xenbus_dev);
628 module_init(xenbus_init);
629 module_exit(xenbus_exit);