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1 /*
2 * Block node graph modifications tests
3 *
4 * Copyright (c) 2019-2021 Virtuozzo International GmbH. All rights reserved.
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with this program. If not, see <http://www.gnu.org/licenses/>.
18 *
19 */
20
21 #include "qemu/osdep.h"
22 #include "qapi/error.h"
23 #include "qemu/main-loop.h"
24 #include "block/block_int.h"
25 #include "sysemu/block-backend.h"
26
27 static BlockDriver bdrv_pass_through = {
28 .format_name = "pass-through",
29 .bdrv_child_perm = bdrv_default_perms,
30 };
31
32 static void no_perm_default_perms(BlockDriverState *bs, BdrvChild *c,
33 BdrvChildRole role,
34 BlockReopenQueue *reopen_queue,
35 uint64_t perm, uint64_t shared,
36 uint64_t *nperm, uint64_t *nshared)
37 {
38 *nperm = 0;
39 *nshared = BLK_PERM_ALL;
40 }
41
42 static BlockDriver bdrv_no_perm = {
43 .format_name = "no-perm",
44 .supports_backing = true,
45 .bdrv_child_perm = no_perm_default_perms,
46 };
47
48 static void exclusive_write_perms(BlockDriverState *bs, BdrvChild *c,
49 BdrvChildRole role,
50 BlockReopenQueue *reopen_queue,
51 uint64_t perm, uint64_t shared,
52 uint64_t *nperm, uint64_t *nshared)
53 {
54 *nperm = BLK_PERM_WRITE;
55 *nshared = BLK_PERM_ALL & ~BLK_PERM_WRITE;
56 }
57
58 static BlockDriver bdrv_exclusive_writer = {
59 .format_name = "exclusive-writer",
60 .bdrv_child_perm = exclusive_write_perms,
61 };
62
63 static BlockDriverState *no_perm_node(const char *name)
64 {
65 return bdrv_new_open_driver(&bdrv_no_perm, name, BDRV_O_RDWR, &error_abort);
66 }
67
68 static BlockDriverState *pass_through_node(const char *name)
69 {
70 return bdrv_new_open_driver(&bdrv_pass_through, name,
71 BDRV_O_RDWR, &error_abort);
72 }
73
74 static BlockDriverState *exclusive_writer_node(const char *name)
75 {
76 return bdrv_new_open_driver(&bdrv_exclusive_writer, name,
77 BDRV_O_RDWR, &error_abort);
78 }
79
80 /*
81 * test_update_perm_tree
82 *
83 * When checking node for a possibility to update permissions, it's subtree
84 * should be correctly checked too. New permissions for each node should be
85 * calculated and checked in context of permissions of other nodes. If we
86 * check new permissions of the node only in context of old permissions of
87 * its neighbors, we can finish up with wrong permission graph.
88 *
89 * This test firstly create the following graph:
90 * +--------+
91 * | root |
92 * +--------+
93 * |
94 * | perm: write, read
95 * | shared: except write
96 * v
97 * +-------------------+ +----------------+
98 * | passtrough filter |---------->| null-co node |
99 * +-------------------+ +----------------+
100 *
101 *
102 * and then, tries to append filter under node. Expected behavior: fail.
103 * Otherwise we'll get the following picture, with two BdrvChild'ren, having
104 * write permission to one node, without actually sharing it.
105 *
106 * +--------+
107 * | root |
108 * +--------+
109 * |
110 * | perm: write, read
111 * | shared: except write
112 * v
113 * +-------------------+
114 * | passtrough filter |
115 * +-------------------+
116 * | |
117 * perm: write, read | | perm: write, read
118 * shared: except write | | shared: except write
119 * v v
120 * +----------------+
121 * | null co node |
122 * +----------------+
123 */
124 static void test_update_perm_tree(void)
125 {
126 int ret;
127
128 BlockBackend *root = blk_new(qemu_get_aio_context(),
129 BLK_PERM_WRITE | BLK_PERM_CONSISTENT_READ,
130 BLK_PERM_ALL & ~BLK_PERM_WRITE);
131 BlockDriverState *bs = no_perm_node("node");
132 BlockDriverState *filter = pass_through_node("filter");
133
134 blk_insert_bs(root, bs, &error_abort);
135
136 bdrv_attach_child(filter, bs, "child", &child_of_bds,
137 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY, &error_abort);
138
139 ret = bdrv_append(filter, bs, NULL);
140 g_assert_cmpint(ret, <, 0);
141
142 bdrv_unref(filter);
143 blk_unref(root);
144 }
145
146 /*
147 * test_should_update_child
148 *
149 * Test that bdrv_replace_node, and concretely should_update_child
150 * do the right thing, i.e. not creating loops on the graph.
151 *
152 * The test does the following:
153 * 1. initial graph:
154 *
155 * +------+ +--------+
156 * | root | | filter |
157 * +------+ +--------+
158 * | |
159 * root| target|
160 * v v
161 * +------+ +--------+
162 * | node |<---------| target |
163 * +------+ backing +--------+
164 *
165 * 2. Append @filter above @node. If should_update_child works correctly,
166 * it understands, that backing child of @target should not be updated,
167 * as it will create a loop on node graph. Resulting picture should
168 * be the left one, not the right:
169 *
170 * +------+ +------+
171 * | root | | root |
172 * +------+ +------+
173 * | |
174 * root| root|
175 * v v
176 * +--------+ target +--------+ target
177 * | filter |--------------+ | filter |--------------+
178 * +--------+ | +--------+ |
179 * | | | ^ v
180 * backing| | backing| | +--------+
181 * v v | +-----------| target |
182 * +------+ +--------+ v backing +--------+
183 * | node |<---------| target | +------+
184 * +------+ backing +--------+ | node |
185 * +------+
186 *
187 * (good picture) (bad picture)
188 *
189 */
190 static void test_should_update_child(void)
191 {
192 BlockBackend *root = blk_new(qemu_get_aio_context(), 0, BLK_PERM_ALL);
193 BlockDriverState *bs = no_perm_node("node");
194 BlockDriverState *filter = no_perm_node("filter");
195 BlockDriverState *target = no_perm_node("target");
196
197 blk_insert_bs(root, bs, &error_abort);
198
199 bdrv_set_backing_hd(target, bs, &error_abort);
200
201 g_assert(target->backing->bs == bs);
202 bdrv_attach_child(filter, target, "target", &child_of_bds,
203 BDRV_CHILD_DATA, &error_abort);
204 bdrv_append(filter, bs, &error_abort);
205 g_assert(target->backing->bs == bs);
206
207 bdrv_unref(filter);
208 bdrv_unref(bs);
209 blk_unref(root);
210 }
211
212 /*
213 * test_parallel_exclusive_write
214 *
215 * Check that when we replace node, old permissions of the node being removed
216 * doesn't break the replacement.
217 */
218 static void test_parallel_exclusive_write(void)
219 {
220 BlockDriverState *top = exclusive_writer_node("top");
221 BlockDriverState *base = no_perm_node("base");
222 BlockDriverState *fl1 = pass_through_node("fl1");
223 BlockDriverState *fl2 = pass_through_node("fl2");
224
225 /*
226 * bdrv_attach_child() eats child bs reference, so we need two @base
227 * references for two filters:
228 */
229 bdrv_ref(base);
230
231 bdrv_attach_child(top, fl1, "backing", &child_of_bds, BDRV_CHILD_DATA,
232 &error_abort);
233 bdrv_attach_child(fl1, base, "backing", &child_of_bds, BDRV_CHILD_FILTERED,
234 &error_abort);
235 bdrv_attach_child(fl2, base, "backing", &child_of_bds, BDRV_CHILD_FILTERED,
236 &error_abort);
237
238 bdrv_replace_node(fl1, fl2, &error_abort);
239
240 bdrv_unref(fl2);
241 bdrv_unref(top);
242 }
243
244 static void write_to_file_perms(BlockDriverState *bs, BdrvChild *c,
245 BdrvChildRole role,
246 BlockReopenQueue *reopen_queue,
247 uint64_t perm, uint64_t shared,
248 uint64_t *nperm, uint64_t *nshared)
249 {
250 if (bs->file && c == bs->file) {
251 *nperm = BLK_PERM_WRITE;
252 *nshared = BLK_PERM_ALL & ~BLK_PERM_WRITE;
253 } else {
254 *nperm = 0;
255 *nshared = BLK_PERM_ALL;
256 }
257 }
258
259 static BlockDriver bdrv_write_to_file = {
260 .format_name = "tricky-perm",
261 .bdrv_child_perm = write_to_file_perms,
262 };
263
264
265 /*
266 * The following test shows that topological-sort order is required for
267 * permission update, simple DFS is not enough.
268 *
269 * Consider the block driver which has two filter children: one active
270 * with exclusive write access and one inactive with no specific
271 * permissions.
272 *
273 * And, these two children has a common base child, like this:
274 *
275 * ┌─────┐ ┌──────┐
276 * │ fl2 │ ◀── │ top │
277 * └─────┘ └──────┘
278 * │ │
279 * │ │ w
280 * │ ▼
281 * │ ┌──────┐
282 * │ │ fl1 │
283 * │ └──────┘
284 * │ │
285 * │ │ w
286 * │ ▼
287 * │ ┌──────┐
288 * └───────▶ │ base │
289 * └──────┘
290 *
291 * So, exclusive write is propagated.
292 *
293 * Assume, we want to make fl2 active instead of fl1.
294 * So, we set some option for top driver and do permission update.
295 *
296 * With simple DFS, if permission update goes first through
297 * top->fl1->base branch it will succeed: it firstly drop exclusive write
298 * permissions and than apply them for another BdrvChildren.
299 * But if permission update goes first through top->fl2->base branch it
300 * will fail, as when we try to update fl2->base child, old not yet
301 * updated fl1->base child will be in conflict.
302 *
303 * With topological-sort order we always update parents before children, so fl1
304 * and fl2 are both updated when we update base and there is no conflict.
305 */
306 static void test_parallel_perm_update(void)
307 {
308 BlockDriverState *top = no_perm_node("top");
309 BlockDriverState *tricky =
310 bdrv_new_open_driver(&bdrv_write_to_file, "tricky", BDRV_O_RDWR,
311 &error_abort);
312 BlockDriverState *base = no_perm_node("base");
313 BlockDriverState *fl1 = pass_through_node("fl1");
314 BlockDriverState *fl2 = pass_through_node("fl2");
315 BdrvChild *c_fl1, *c_fl2;
316
317 /*
318 * bdrv_attach_child() eats child bs reference, so we need two @base
319 * references for two filters:
320 */
321 bdrv_ref(base);
322
323 bdrv_attach_child(top, tricky, "file", &child_of_bds, BDRV_CHILD_DATA,
324 &error_abort);
325 c_fl1 = bdrv_attach_child(tricky, fl1, "first", &child_of_bds,
326 BDRV_CHILD_FILTERED, &error_abort);
327 c_fl2 = bdrv_attach_child(tricky, fl2, "second", &child_of_bds,
328 BDRV_CHILD_FILTERED, &error_abort);
329 bdrv_attach_child(fl1, base, "backing", &child_of_bds, BDRV_CHILD_FILTERED,
330 &error_abort);
331 bdrv_attach_child(fl2, base, "backing", &child_of_bds, BDRV_CHILD_FILTERED,
332 &error_abort);
333
334 /* Select fl1 as first child to be active */
335 tricky->file = c_fl1;
336 bdrv_child_refresh_perms(top, top->children.lh_first, &error_abort);
337
338 assert(c_fl1->perm & BLK_PERM_WRITE);
339 assert(!(c_fl2->perm & BLK_PERM_WRITE));
340
341 /* Now, try to switch active child and update permissions */
342 tricky->file = c_fl2;
343 bdrv_child_refresh_perms(top, top->children.lh_first, &error_abort);
344
345 assert(c_fl2->perm & BLK_PERM_WRITE);
346 assert(!(c_fl1->perm & BLK_PERM_WRITE));
347
348 /* Switch once more, to not care about real child order in the list */
349 tricky->file = c_fl1;
350 bdrv_child_refresh_perms(top, top->children.lh_first, &error_abort);
351
352 assert(c_fl1->perm & BLK_PERM_WRITE);
353 assert(!(c_fl2->perm & BLK_PERM_WRITE));
354
355 bdrv_unref(top);
356 }
357
358 /*
359 * It's possible that filter required permissions allows to insert it to backing
360 * chain, like:
361 *
362 * 1. [top] -> [filter] -> [base]
363 *
364 * but doesn't allow to add it as a branch:
365 *
366 * 2. [filter] --\
367 * v
368 * [top] -> [base]
369 *
370 * So, inserting such filter should do all graph modifications and only then
371 * update permissions. If we try to go through intermediate state [2] and update
372 * permissions on it we'll fail.
373 *
374 * Let's check that bdrv_append() can append such a filter.
375 */
376 static void test_append_greedy_filter(void)
377 {
378 BlockDriverState *top = exclusive_writer_node("top");
379 BlockDriverState *base = no_perm_node("base");
380 BlockDriverState *fl = exclusive_writer_node("fl1");
381
382 bdrv_attach_child(top, base, "backing", &child_of_bds, BDRV_CHILD_COW,
383 &error_abort);
384
385 bdrv_append(fl, base, &error_abort);
386 bdrv_unref(fl);
387 bdrv_unref(top);
388 }
389
390 int main(int argc, char *argv[])
391 {
392 bdrv_init();
393 qemu_init_main_loop(&error_abort);
394
395 g_test_init(&argc, &argv, NULL);
396
397 g_test_add_func("/bdrv-graph-mod/update-perm-tree", test_update_perm_tree);
398 g_test_add_func("/bdrv-graph-mod/should-update-child",
399 test_should_update_child);
400 g_test_add_func("/bdrv-graph-mod/parallel-perm-update",
401 test_parallel_perm_update);
402 g_test_add_func("/bdrv-graph-mod/parallel-exclusive-write",
403 test_parallel_exclusive_write);
404 g_test_add_func("/bdrv-graph-mod/append-greedy-filter",
405 test_append_greedy_filter);
406
407 return g_test_run();
408 }