aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/md/dm-log-userspace-transfer.c
blob: 049eaf12aaab93465889a3dd5fe01e78955fb514 (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
/*
 * Copyright (C) 2006-2009 Red Hat, Inc.
 *
 * This file is released under the LGPL.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <linux/workqueue.h>
#include <linux/connector.h>
#include <linux/device-mapper.h>
#include <linux/dm-log-userspace.h>

#include "dm-log-userspace-transfer.h"

static uint32_t dm_ulog_seq;

/*
 * Netlink/Connector is an unreliable protocol.  How long should
 * we wait for a response before assuming it was lost and retrying?
 * (If we do receive a response after this time, it will be discarded
 * and the response to the resent request will be waited for.
 */
#define DM_ULOG_RETRY_TIMEOUT (15 * HZ)

/*
 * Pre-allocated space for speed
 */
#define DM_ULOG_PREALLOCED_SIZE 512
static struct cn_msg *prealloced_cn_msg;
static struct dm_ulog_request *prealloced_ulog_tfr;

static struct cb_id ulog_cn_id = {
	.idx = CN_IDX_DM,
	.val = CN_VAL_DM_USERSPACE_LOG
};

static DEFINE_MUTEX(dm_ulog_lock);

struct receiving_pkg {
	struct list_head list;
	struct completion complete;

	uint32_t seq;

	int error;
	size_t *data_size;
	char *data;
};

static DEFINE_SPINLOCK(receiving_list_lock);
static struct list_head receiving_list;

static int dm_ulog_sendto_server(struct dm_ulog_request *tfr)
{
	int r;
	struct cn_msg *msg = prealloced_cn_msg;

	memset(msg, 0, sizeof(struct cn_msg));

	msg->id.idx = ulog_cn_id.idx;
	msg->id.val = ulog_cn_id.val;
	msg->ack = 0;
	msg->seq = tfr->seq;
	msg->len = sizeof(struct dm_ulog_request) + tfr->data_size;

	r = cn_netlink_send(msg, 0, gfp_any());

	return r;
}

/*
 * Parameters for this function can be either msg or tfr, but not
 * both.  This function fills in the reply for a waiting request.
 * If just msg is given, then the reply is simply an ACK from userspace
 * that the request was received.
 *
 * Returns: 0 on success, -ENOENT on failure
 */
static int fill_pkg(struct cn_msg *msg, struct dm_ulog_request *tfr)
{
	uint32_t rtn_seq = (msg) ? msg->seq : (tfr) ? tfr->seq : 0;
	struct receiving_pkg *pkg;

	/*
	 * The 'receiving_pkg' entries in this list are statically
	 * allocated on the stack in 'dm_consult_userspace'.
	 * Each process that is waiting for a reply from the user
	 * space server will have an entry in this list.
	 *
	 * We are safe to do it this way because the stack space
	 * is unique to each process, but still addressable by
	 * other processes.
	 */
	list_for_each_entry(pkg, &receiving_list, list) {
		if (rtn_seq != pkg->seq)
			continue;

		if (msg) {
			pkg->error = -msg->ack;
			/*
			 * If we are trying again, we will need to know our
			 * storage capacity.  Otherwise, along with the
			 * error code, we make explicit that we have no data.
			 */
			if (pkg->error != -EAGAIN)
				*(pkg->data_size) = 0;
		} else if (tfr->data_size > *(pkg->data_size)) {
			DMERR("Insufficient space to receive package [%u] "
			      "(%u vs %zu)", tfr->request_type,
			      tfr->data_size, *(pkg->data_size));

			*(pkg->data_size) = 0;
			pkg->error = -ENOSPC;
		} else {
			pkg->error = tfr->error;
			memcpy(pkg->data, tfr->data, tfr->data_size);
			*(pkg->data_size) = tfr->data_size;
		}
		complete(&pkg->complete);
		return 0;
	}

	return -ENOENT;
}

/*
 * This is the connector callback that delivers data
 * that was sent from userspace.
 */
static void cn_ulog_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
{
	struct dm_ulog_request *tfr = (struct dm_ulog_request *)(msg + 1);

	if (!cap_raised(nsp->eff_cap, CAP_SYS_ADMIN))
		return;

	spin_lock(&receiving_list_lock);
	if (msg->len == 0)
		fill_pkg(msg, NULL);
	else if (msg->len < sizeof(*tfr))
		DMERR("Incomplete message received (expected %u, got %u): [%u]",
		      (unsigned)sizeof(*tfr), msg->len, msg->seq);
	else
		fill_pkg(NULL, tfr);
	spin_unlock(&receiving_list_lock);
}

/**
 * dm_consult_userspace
 * @uuid: log's universal unique identifier (must be DM_UUID_LEN in size)
 * @luid: log's local unique identifier
 * @request_type:  found in include/linux/dm-log-userspace.h
 * @data: data to tx to the server
 * @data_size: size of data in bytes
 * @rdata: place to put return data from server
 * @rdata_size: value-result (amount of space given/amount of space used)
 *
 * rdata_size is undefined on failure.
 *
 * Memory used to communicate with userspace is zero'ed
 * before populating to ensure that no unwanted bits leak
 * from kernel space to user-space.  All userspace log communications
 * between kernel and user space go through this function.
 *
 * Returns: 0 on success, -EXXX on failure
 **/
int dm_consult_userspace(const char *uuid, uint64_t luid, int request_type,
			 char *data, size_t data_size,
			 char *rdata, size_t *rdata_size)
{
	int r = 0;
	size_t dummy = 0;
	int overhead_size = sizeof(struct dm_ulog_request) + sizeof(struct cn_msg);
	struct dm_ulog_request *tfr = prealloced_ulog_tfr;
	struct receiving_pkg pkg;

	/*
	 * Given the space needed to hold the 'struct cn_msg' and
	 * 'struct dm_ulog_request' - do we have enough payload
	 * space remaining?
	 */
	if (data_size > (DM_ULOG_PREALLOCED_SIZE - overhead_size)) {
		DMINFO("Size of tfr exceeds preallocated size");
		return -EINVAL;
	}

	if (!rdata_size)
		rdata_size = &dummy;
resend:
	/*
	 * We serialize the sending of requests so we can
	 * use the preallocated space.
	 */
	mutex_lock(&dm_ulog_lock);

	memset(tfr, 0, DM_ULOG_PREALLOCED_SIZE - sizeof(struct cn_msg));
	memcpy(tfr->uuid, uuid, DM_UUID_LEN);
	tfr->version = DM_ULOG_REQUEST_VERSION;
	tfr->luid = luid;
	tfr->seq = dm_ulog_seq++;

	/*
	 * Must be valid request type (all other bits set to
	 * zero).  This reserves other bits for possible future
	 * use.
	 */
	tfr->request_type = request_type & DM_ULOG_REQUEST_MASK;

	tfr->data_size = data_size;
	if (data && data_size)
		memcpy(tfr->data, data, data_size);

	memset(&pkg, 0, sizeof(pkg));
	init_completion(&pkg.complete);
	pkg.seq = tfr->seq;
	pkg.data_size = rdata_size;
	pkg.data = rdata;
	spin_lock(&receiving_list_lock);
	list_add(&(pkg.list), &receiving_list);
	spin_unlock(&receiving_list_lock);

	r = dm_ulog_sendto_server(tfr);

	mutex_unlock(&dm_ulog_lock);

	if (r) {
		DMERR("Unable to send log request [%u] to userspace: %d",
		      request_type, r);
		spin_lock(&receiving_list_lock);
		list_del_init(&(pkg.list));
		spin_unlock(&receiving_list_lock);

		goto out;
	}

	r = wait_for_completion_timeout(&(pkg.complete), DM_ULOG_RETRY_TIMEOUT);
	spin_lock(&receiving_list_lock);
	list_del_init(&(pkg.list));
	spin_unlock(&receiving_list_lock);
	if (!r) {
		DMWARN("[%s] Request timed out: [%u/%u] - retrying",
		       (strlen(uuid) > 8) ?
		       (uuid + (strlen(uuid) - 8)) : (uuid),
		       request_type, pkg.seq);
		goto resend;
	}

	r = pkg.error;
	if (r == -EAGAIN)
		goto resend;

out:
	return r;
}

int dm_ulog_tfr_init(void)
{
	int r;
	void *prealloced;

	INIT_LIST_HEAD(&receiving_list);

	prealloced = kmalloc(DM_ULOG_PREALLOCED_SIZE, GFP_KERNEL);
	if (!prealloced)
		return -ENOMEM;

	prealloced_cn_msg = prealloced;
	prealloced_ulog_tfr = prealloced + sizeof(struct cn_msg);

	r = cn_add_callback(&ulog_cn_id, "dmlogusr", cn_ulog_callback);
	if (r) {
		cn_del_callback(&ulog_cn_id);
		return r;
	}

	return 0;
}

void dm_ulog_tfr_exit(void)
{
	cn_del_callback(&ulog_cn_id);
	kfree(prealloced_cn_msg);
}