summaryrefslogtreecommitdiffstats
path: root/fs/afs/vl_alias.c
blob: 89cadd9a69e12b2e710e743d32f0dcd80aba3863 (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
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
// SPDX-License-Identifier: GPL-2.0-or-later
/* AFS cell alias detection
 *
 * Copyright (C) 2020 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/namei.h>
#include <keys/rxrpc-type.h>
#include "internal.h"

/*
 * Sample a volume.
 */
static struct afs_volume *afs_sample_volume(struct afs_cell *cell, struct key *key,
					    const char *name, unsigned int namelen)
{
	struct afs_volume *volume;
	struct afs_fs_context fc = {
		.type		= 0, /* Explicitly leave it to the VLDB */
		.volnamesz	= namelen,
		.volname	= name,
		.net		= cell->net,
		.cell		= cell,
		.key		= key, /* This might need to be something */
	};

	volume = afs_create_volume(&fc);
	_leave(" = %p", volume);
	return volume;
}

/*
 * Compare the address lists of a pair of fileservers.
 */
static int afs_compare_fs_alists(const struct afs_server *server_a,
				 const struct afs_server *server_b)
{
	const struct afs_addr_list *la, *lb;
	int a = 0, b = 0, addr_matches = 0;

	la = rcu_dereference(server_a->addresses);
	lb = rcu_dereference(server_b->addresses);

	while (a < la->nr_addrs && b < lb->nr_addrs) {
		unsigned long pa = (unsigned long)la->addrs[a].peer;
		unsigned long pb = (unsigned long)lb->addrs[b].peer;
		long diff = pa - pb;

		if (diff < 0) {
			a++;
		} else if (diff > 0) {
			b++;
		} else {
			addr_matches++;
			a++;
			b++;
		}
	}

	return addr_matches;
}

/*
 * Compare the fileserver lists of two volumes.  The server lists are sorted in
 * order of ascending UUID.
 */
static int afs_compare_volume_slists(const struct afs_volume *vol_a,
				     const struct afs_volume *vol_b)
{
	const struct afs_server_list *la, *lb;
	int i, a = 0, b = 0, uuid_matches = 0, addr_matches = 0;

	la = rcu_dereference(vol_a->servers);
	lb = rcu_dereference(vol_b->servers);

	for (i = 0; i < AFS_MAXTYPES; i++)
		if (la->vids[i] != lb->vids[i])
			return 0;

	while (a < la->nr_servers && b < lb->nr_servers) {
		const struct afs_server *server_a = la->servers[a].server;
		const struct afs_server *server_b = lb->servers[b].server;
		int diff = memcmp(&server_a->uuid, &server_b->uuid, sizeof(uuid_t));

		if (diff < 0) {
			a++;
		} else if (diff > 0) {
			b++;
		} else {
			uuid_matches++;
			addr_matches += afs_compare_fs_alists(server_a, server_b);
			a++;
			b++;
		}
	}

	_leave(" = %d [um %d]", addr_matches, uuid_matches);
	return addr_matches;
}

/*
 * Compare root.cell volumes.
 */
static int afs_compare_cell_roots(struct afs_cell *cell)
{
	struct afs_cell *p;

	_enter("");

	rcu_read_lock();

	hlist_for_each_entry_rcu(p, &cell->net->proc_cells, proc_link) {
		if (p == cell || p->alias_of)
			continue;
		if (!p->root_volume)
			continue; /* Ignore cells that don't have a root.cell volume. */

		if (afs_compare_volume_slists(cell->root_volume, p->root_volume) != 0)
			goto is_alias;
	}

	rcu_read_unlock();
	_leave(" = 0");
	return 0;

is_alias:
	rcu_read_unlock();
	cell->alias_of = afs_use_cell(p, afs_cell_trace_use_alias);
	return 1;
}

/*
 * Query the new cell for a volume from a cell we're already using.
 */
static int afs_query_for_alias_one(struct afs_cell *cell, struct key *key,
				   struct afs_cell *p)
{
	struct afs_volume *volume, *pvol = NULL;
	int ret;

	/* Arbitrarily pick a volume from the list. */
	read_seqlock_excl(&p->volume_lock);
	if (!RB_EMPTY_ROOT(&p->volumes))
		pvol = afs_get_volume(rb_entry(p->volumes.rb_node,
					       struct afs_volume, cell_node),
				      afs_volume_trace_get_query_alias);
	read_sequnlock_excl(&p->volume_lock);
	if (!pvol)
		return 0;

	_enter("%s:%s", cell->name, pvol->name);

	/* And see if it's in the new cell. */
	volume = afs_sample_volume(cell, key, pvol->name, pvol->name_len);
	if (IS_ERR(volume)) {
		afs_put_volume(cell->net, pvol, afs_volume_trace_put_query_alias);
		if (PTR_ERR(volume) != -ENOMEDIUM)
			return PTR_ERR(volume);
		/* That volume is not in the new cell, so not an alias */
		return 0;
	}

	/* The new cell has a like-named volume also - compare volume ID,
	 * server and address lists.
	 */
	ret = 0;
	if (pvol->vid == volume->vid) {
		rcu_read_lock();
		if (afs_compare_volume_slists(volume, pvol))
			ret = 1;
		rcu_read_unlock();
	}

	afs_put_volume(cell->net, volume, afs_volume_trace_put_query_alias);
	afs_put_volume(cell->net, pvol, afs_volume_trace_put_query_alias);
	return ret;
}

/*
 * Query the new cell for volumes we know exist in cells we're already using.
 */
static int afs_query_for_alias(struct afs_cell *cell, struct key *key)
{
	struct afs_cell *p;

	_enter("%s", cell->name);

	if (mutex_lock_interruptible(&cell->net->proc_cells_lock) < 0)
		return -ERESTARTSYS;

	hlist_for_each_entry(p, &cell->net->proc_cells, proc_link) {
		if (p == cell || p->alias_of)
			continue;
		if (RB_EMPTY_ROOT(&p->volumes))
			continue;
		if (p->root_volume)
			continue; /* Ignore cells that have a root.cell volume. */
		afs_use_cell(p, afs_cell_trace_use_check_alias);
		mutex_unlock(&cell->net->proc_cells_lock);

		if (afs_query_for_alias_one(cell, key, p) != 0)
			goto is_alias;

		if (mutex_lock_interruptible(&cell->net->proc_cells_lock) < 0) {
			afs_unuse_cell(cell->net, p, afs_cell_trace_unuse_check_alias);
			return -ERESTARTSYS;
		}

		afs_unuse_cell(cell->net, p, afs_cell_trace_unuse_check_alias);
	}

	mutex_unlock(&cell->net->proc_cells_lock);
	_leave(" = 0");
	return 0;

is_alias:
	cell->alias_of = p; /* Transfer our ref */
	return 1;
}

/*
 * Look up a VLDB record for a volume.
 */
static char *afs_vl_get_cell_name(struct afs_cell *cell, struct key *key)
{
	struct afs_vl_cursor vc;
	char *cell_name = ERR_PTR(-EDESTADDRREQ);
	bool skipped = false, not_skipped = false;
	int ret;

	if (!afs_begin_vlserver_operation(&vc, cell, key))
		return ERR_PTR(-ERESTARTSYS);

	while (afs_select_vlserver(&vc)) {
		if (!test_bit(AFS_VLSERVER_FL_IS_YFS, &vc.server->flags)) {
			vc.call_error = -EOPNOTSUPP;
			skipped = true;
			continue;
		}
		not_skipped = true;
		cell_name = afs_yfsvl_get_cell_name(&vc);
	}

	ret = afs_end_vlserver_operation(&vc);
	if (skipped && !not_skipped)
		ret = -EOPNOTSUPP;
	return ret < 0 ? ERR_PTR(ret) : cell_name;
}

static int yfs_check_canonical_cell_name(struct afs_cell *cell, struct key *key)
{
	struct afs_cell *master;
	char *cell_name;

	cell_name = afs_vl_get_cell_name(cell, key);
	if (IS_ERR(cell_name))
		return PTR_ERR(cell_name);

	if (strcmp(cell_name, cell->name) == 0) {
		kfree(cell_name);
		return 0;
	}

	master = afs_lookup_cell(cell->net, cell_name, strlen(cell_name),
				 NULL, false);
	kfree(cell_name);
	if (IS_ERR(master))
		return PTR_ERR(master);

	cell->alias_of = master; /* Transfer our ref */
	return 1;
}

static int afs_do_cell_detect_alias(struct afs_cell *cell, struct key *key)
{
	struct afs_volume *root_volume;
	int ret;

	_enter("%s", cell->name);

	ret = yfs_check_canonical_cell_name(cell, key);
	if (ret != -EOPNOTSUPP)
		return ret;

	/* Try and get the root.cell volume for comparison with other cells */
	root_volume = afs_sample_volume(cell, key, "root.cell", 9);
	if (!IS_ERR(root_volume)) {
		cell->root_volume = root_volume;
		return afs_compare_cell_roots(cell);
	}

	if (PTR_ERR(root_volume) != -ENOMEDIUM)
		return PTR_ERR(root_volume);

	/* Okay, this cell doesn't have an root.cell volume.  We need to
	 * locate some other random volume and use that to check.
	 */
	return afs_query_for_alias(cell, key);
}

/*
 * Check to see if a new cell is an alias of a cell we already have.  At this
 * point we have the cell's volume server list.
 *
 * Returns 0 if we didn't detect an alias, 1 if we found an alias and an error
 * if we had problems gathering the data required.  In the case the we did
 * detect an alias, cell->alias_of is set to point to the assumed master.
 */
int afs_cell_detect_alias(struct afs_cell *cell, struct key *key)
{
	struct afs_net *net = cell->net;
	int ret;

	if (mutex_lock_interruptible(&net->cells_alias_lock) < 0)
		return -ERESTARTSYS;

	if (test_bit(AFS_CELL_FL_CHECK_ALIAS, &cell->flags)) {
		ret = afs_do_cell_detect_alias(cell, key);
		if (ret >= 0)
			clear_bit_unlock(AFS_CELL_FL_CHECK_ALIAS, &cell->flags);
	} else {
		ret = cell->alias_of ? 1 : 0;
	}

	mutex_unlock(&net->cells_alias_lock);

	if (ret == 1)
		pr_notice("kAFS: Cell %s is an alias of %s\n",
			  cell->name, cell->alias_of->name);
	return ret;
}