summaryrefslogtreecommitdiffstats
path: root/drivers/xen/xenbus/xenbus_probe_backend.c
blob: 2ba699897e6dd9fced51a6f8a9cf975a3e2bef4c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
/******************************************************************************
 * Talks to Xen Store to figure out what devices we have (backend half).
 *
 * Copyright (C) 2005 Rusty Russell, IBM Corporation
 * Copyright (C) 2005 Mike Wray, Hewlett-Packard
 * Copyright (C) 2005, 2006 XenSource Ltd
 * Copyright (C) 2007 Solarflare Communications, Inc.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation; or, when distributed
 * separately from the Linux kernel or incorporated into other
 * software packages, subject to the following license:
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this source file (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#define DPRINTK(fmt, ...)				\
	pr_debug("(%s:%d) " fmt "\n",			\
		 __func__, __LINE__, ##__VA_ARGS__)

#include <linux/kernel.h>
#include <linux/err.h>
#include <linux/string.h>
#include <linux/ctype.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/notifier.h>
#include <linux/export.h>
#include <linux/semaphore.h>

#include <asm/page.h>
#include <asm/xen/hypervisor.h>
#include <asm/hypervisor.h>
#include <xen/xenbus.h>
#include <xen/features.h>

#include "xenbus.h"

/* backend/<type>/<fe-uuid>/<id> => <type>-<fe-domid>-<id> */
static int backend_bus_id(char bus_id[XEN_BUS_ID_SIZE], const char *nodename)
{
	int domid, err;
	const char *devid, *type, *frontend;
	unsigned int typelen;

	type = strchr(nodename, '/');
	if (!type)
		return -EINVAL;
	type++;
	typelen = strcspn(type, "/");
	if (!typelen || type[typelen] != '/')
		return -EINVAL;

	devid = strrchr(nodename, '/') + 1;

	err = xenbus_gather(XBT_NIL, nodename, "frontend-id", "%i", &domid,
			    "frontend", NULL, &frontend,
			    NULL);
	if (err)
		return err;
	if (strlen(frontend) == 0)
		err = -ERANGE;
	if (!err && !xenbus_exists(XBT_NIL, frontend, ""))
		err = -ENOENT;
	kfree(frontend);

	if (err)
		return err;

	if (snprintf(bus_id, XEN_BUS_ID_SIZE, "%.*s-%i-%s",
		     typelen, type, domid, devid) >= XEN_BUS_ID_SIZE)
		return -ENOSPC;
	return 0;
}

static int xenbus_uevent_backend(struct device *dev,
				 struct kobj_uevent_env *env)
{
	struct xenbus_device *xdev;
	struct xenbus_driver *drv;
	struct xen_bus_type *bus;

	DPRINTK("");

	if (dev == NULL)
		return -ENODEV;

	xdev = to_xenbus_device(dev);
	bus = container_of(xdev->dev.bus, struct xen_bus_type, bus);

	if (add_uevent_var(env, "MODALIAS=xen-backend:%s", xdev->devicetype))
		return -ENOMEM;

	/* stuff we want to pass to /sbin/hotplug */
	if (add_uevent_var(env, "XENBUS_TYPE=%s", xdev->devicetype))
		return -ENOMEM;

	if (add_uevent_var(env, "XENBUS_PATH=%s", xdev->nodename))
		return -ENOMEM;

	if (add_uevent_var(env, "XENBUS_BASE_PATH=%s", bus->root))
		return -ENOMEM;

	if (dev->driver) {
		drv = to_xenbus_driver(dev->driver);
		if (drv && drv->uevent)
			return drv->uevent(xdev, env);
	}

	return 0;
}

/* backend/<typename>/<frontend-uuid>/<name> */
static int xenbus_probe_backend_unit(struct xen_bus_type *bus,
				     const char *dir,
				     const char *type,
				     const char *name)
{
	char *nodename;
	int err;

	nodename = kasprintf(GFP_KERNEL, "%s/%s", dir, name);
	if (!nodename)
		return -ENOMEM;

	DPRINTK("%s\n", nodename);

	err = xenbus_probe_node(bus, type, nodename);
	kfree(nodename);
	return err;
}

/* backend/<typename>/<frontend-domid> */
static int xenbus_probe_backend(struct xen_bus_type *bus, const char *type,
				const char *domid)
{
	char *nodename;
	int err = 0;
	char **dir;
	unsigned int i, dir_n = 0;

	DPRINTK("");

	nodename = kasprintf(GFP_KERNEL, "%s/%s/%s", bus->root, type, domid);
	if (!nodename)
		return -ENOMEM;

	dir = xenbus_directory(XBT_NIL, nodename, "", &dir_n);
	if (IS_ERR(dir)) {
		kfree(nodename);
		return PTR_ERR(dir);
	}

	for (i = 0; i < dir_n; i++) {
		err = xenbus_probe_backend_unit(bus, nodename, type, dir[i]);
		if (err)
			break;
	}
	kfree(dir);
	kfree(nodename);
	return err;
}

static void frontend_changed(struct xenbus_watch *watch,
			     const char *path, const char *token)
{
	xenbus_otherend_changed(watch, path, token, 0);
}

static struct xen_bus_type xenbus_backend = {
	.root = "backend",
	.levels = 3,		/* backend/type/<frontend>/<id> */
	.get_bus_id = backend_bus_id,
	.probe = xenbus_probe_backend,
	.otherend_changed = frontend_changed,
	.bus = {
		.name		= "xen-backend",
		.match		= xenbus_match,
		.uevent		= xenbus_uevent_backend,
		.probe		= xenbus_dev_probe,
		.remove		= xenbus_dev_remove,
		.dev_groups	= xenbus_dev_groups,
	},
};

static void backend_changed(struct xenbus_watch *watch,
			    const char *path, const char *token)
{
	DPRINTK("");

	xenbus_dev_changed(path, &xenbus_backend);
}

static struct xenbus_watch be_watch = {
	.node = "backend",
	.callback = backend_changed,
};

static int read_frontend_details(struct xenbus_device *xendev)
{
	return xenbus_read_otherend_details(xendev, "frontend-id", "frontend");
}

int xenbus_dev_is_online(struct xenbus_device *dev)
{
	return !!xenbus_read_unsigned(dev->nodename, "online", 0);
}
EXPORT_SYMBOL_GPL(xenbus_dev_is_online);

int __xenbus_register_backend(struct xenbus_driver *drv, struct module *owner,
			      const char *mod_name)
{
	drv->read_otherend_details = read_frontend_details;

	return xenbus_register_driver_common(drv, &xenbus_backend,
					     owner, mod_name);
}
EXPORT_SYMBOL_GPL(__xenbus_register_backend);

static int backend_probe_and_watch(struct notifier_block *notifier,
				   unsigned long event,
				   void *data)
{
	/* Enumerate devices in xenstore and watch for changes. */
	xenbus_probe_devices(&xenbus_backend);
	register_xenbus_watch(&be_watch);

	return NOTIFY_DONE;
}

static int backend_reclaim_memory(struct device *dev, void *data)
{
	const struct xenbus_driver *drv;
	struct xenbus_device *xdev;

	if (!dev->driver)
		return 0;
	drv = to_xenbus_driver(dev->driver);
	if (drv && drv->reclaim_memory) {
		xdev = to_xenbus_device(dev);
		if (down_trylock(&xdev->reclaim_sem))
			return 0;
		drv->reclaim_memory(xdev);
		up(&xdev->reclaim_sem);
	}
	return 0;
}

/*
 * Returns 0 always because we are using shrinker to only detect memory
 * pressure.
 */
static unsigned long backend_shrink_memory_count(struct shrinker *shrinker,
				struct shrink_control *sc)
{
	bus_for_each_dev(&xenbus_backend.bus, NULL, NULL,
			backend_reclaim_memory);
	return 0;
}

static struct shrinker backend_memory_shrinker = {
	.count_objects = backend_shrink_memory_count,
	.seeks = DEFAULT_SEEKS,
};

static int __init xenbus_probe_backend_init(void)
{
	static struct notifier_block xenstore_notifier = {
		.notifier_call = backend_probe_and_watch
	};
	int err;

	DPRINTK("");

	/* Register ourselves with the kernel bus subsystem */
	err = bus_register(&xenbus_backend.bus);
	if (err)
		return err;

	register_xenstore_notifier(&xenstore_notifier);

	if (register_shrinker(&backend_memory_shrinker))
		pr_warn("shrinker registration failed\n");

	return 0;
}
subsys_initcall(xenbus_probe_backend_init);