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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 .is_filter = true,
30 .filtered_child_is_backing = true,
31 .bdrv_child_perm = bdrv_default_perms,
32 };
33
34 static void no_perm_default_perms(BlockDriverState *bs, BdrvChild *c,
35 BdrvChildRole role,
36 BlockReopenQueue *reopen_queue,
37 uint64_t perm, uint64_t shared,
38 uint64_t *nperm, uint64_t *nshared)
39 {
40 *nperm = 0;
41 *nshared = BLK_PERM_ALL;
42 }
43
44 static BlockDriver bdrv_no_perm = {
45 .format_name = "no-perm",
46 .supports_backing = true,
47 .bdrv_child_perm = no_perm_default_perms,
48 };
49
50 static void exclusive_write_perms(BlockDriverState *bs, BdrvChild *c,
51 BdrvChildRole role,
52 BlockReopenQueue *reopen_queue,
53 uint64_t perm, uint64_t shared,
54 uint64_t *nperm, uint64_t *nshared)
55 {
56 *nperm = BLK_PERM_WRITE;
57 *nshared = BLK_PERM_ALL & ~BLK_PERM_WRITE;
58 }
59
60 static BlockDriver bdrv_exclusive_writer = {
61 .format_name = "exclusive-writer",
62 .is_filter = true,
63 .filtered_child_is_backing = true,
64 .bdrv_child_perm = exclusive_write_perms,
65 };
66
67 static BlockDriverState *no_perm_node(const char *name)
68 {
69 return bdrv_new_open_driver(&bdrv_no_perm, name, BDRV_O_RDWR, &error_abort);
70 }
71
72 static BlockDriverState *pass_through_node(const char *name)
73 {
74 return bdrv_new_open_driver(&bdrv_pass_through, name,
75 BDRV_O_RDWR, &error_abort);
76 }
77
78 static BlockDriverState *exclusive_writer_node(const char *name)
79 {
80 return bdrv_new_open_driver(&bdrv_exclusive_writer, name,
81 BDRV_O_RDWR, &error_abort);
82 }
83
84 /*
85 * test_update_perm_tree
86 *
87 * When checking node for a possibility to update permissions, it's subtree
88 * should be correctly checked too. New permissions for each node should be
89 * calculated and checked in context of permissions of other nodes. If we
90 * check new permissions of the node only in context of old permissions of
91 * its neighbors, we can finish up with wrong permission graph.
92 *
93 * This test firstly create the following graph:
94 * +--------+
95 * | root |
96 * +--------+
97 * |
98 * | perm: write, read
99 * | shared: except write
100 * v
101 * +--------------------+ +----------------+
102 * | passthrough filter |--------->| null-co node |
103 * +--------------------+ +----------------+
104 *
105 *
106 * and then, tries to append filter under node. Expected behavior: fail.
107 * Otherwise we'll get the following picture, with two BdrvChild'ren, having
108 * write permission to one node, without actually sharing it.
109 *
110 * +--------+
111 * | root |
112 * +--------+
113 * |
114 * | perm: write, read
115 * | shared: except write
116 * v
117 * +--------------------+
118 * | passthrough filter |
119 * +--------------------+
120 * | |
121 * perm: write, read | | perm: write, read
122 * shared: except write | | shared: except write
123 * v v
124 * +----------------+
125 * | null co node |
126 * +----------------+
127 */
128 static void test_update_perm_tree(void)
129 {
130 int ret;
131
132 BlockBackend *root = blk_new(qemu_get_aio_context(),
133 BLK_PERM_WRITE | BLK_PERM_CONSISTENT_READ,
134 BLK_PERM_ALL & ~BLK_PERM_WRITE);
135 BlockDriverState *bs = no_perm_node("node");
136 BlockDriverState *filter = pass_through_node("filter");
137
138 blk_insert_bs(root, bs, &error_abort);
139
140 bdrv_graph_wrlock(NULL);
141 bdrv_attach_child(filter, bs, "child", &child_of_bds,
142 BDRV_CHILD_DATA, &error_abort);
143 bdrv_graph_wrunlock();
144
145 aio_context_acquire(qemu_get_aio_context());
146 ret = bdrv_append(filter, bs, NULL);
147 g_assert_cmpint(ret, <, 0);
148 aio_context_release(qemu_get_aio_context());
149
150 bdrv_unref(filter);
151 blk_unref(root);
152 }
153
154 /*
155 * test_should_update_child
156 *
157 * Test that bdrv_replace_node, and concretely should_update_child
158 * do the right thing, i.e. not creating loops on the graph.
159 *
160 * The test does the following:
161 * 1. initial graph:
162 *
163 * +------+ +--------+
164 * | root | | filter |
165 * +------+ +--------+
166 * | |
167 * root| target|
168 * v v
169 * +------+ +--------+
170 * | node |<---------| target |
171 * +------+ backing +--------+
172 *
173 * 2. Append @filter above @node. If should_update_child works correctly,
174 * it understands, that backing child of @target should not be updated,
175 * as it will create a loop on node graph. Resulting picture should
176 * be the left one, not the right:
177 *
178 * +------+ +------+
179 * | root | | root |
180 * +------+ +------+
181 * | |
182 * root| root|
183 * v v
184 * +--------+ target +--------+ target
185 * | filter |--------------+ | filter |--------------+
186 * +--------+ | +--------+ |
187 * | | | ^ v
188 * backing| | backing| | +--------+
189 * v v | +-----------| target |
190 * +------+ +--------+ v backing +--------+
191 * | node |<---------| target | +------+
192 * +------+ backing +--------+ | node |
193 * +------+
194 *
195 * (good picture) (bad picture)
196 *
197 */
198 static void test_should_update_child(void)
199 {
200 BlockBackend *root = blk_new(qemu_get_aio_context(), 0, BLK_PERM_ALL);
201 BlockDriverState *bs = no_perm_node("node");
202 BlockDriverState *filter = no_perm_node("filter");
203 BlockDriverState *target = no_perm_node("target");
204
205 blk_insert_bs(root, bs, &error_abort);
206
207 bdrv_set_backing_hd(target, bs, &error_abort);
208
209 g_assert(target->backing->bs == bs);
210 bdrv_graph_wrlock(NULL);
211 bdrv_attach_child(filter, target, "target", &child_of_bds,
212 BDRV_CHILD_DATA, &error_abort);
213 bdrv_graph_wrunlock();
214 aio_context_acquire(qemu_get_aio_context());
215 bdrv_append(filter, bs, &error_abort);
216 aio_context_release(qemu_get_aio_context());
217 g_assert(target->backing->bs == bs);
218
219 bdrv_unref(filter);
220 bdrv_unref(bs);
221 blk_unref(root);
222 }
223
224 /*
225 * test_parallel_exclusive_write
226 *
227 * Check that when we replace node, old permissions of the node being removed
228 * doesn't break the replacement.
229 */
230 static void test_parallel_exclusive_write(void)
231 {
232 BlockDriverState *top = exclusive_writer_node("top");
233 BlockDriverState *base = no_perm_node("base");
234 BlockDriverState *fl1 = pass_through_node("fl1");
235 BlockDriverState *fl2 = pass_through_node("fl2");
236
237 /*
238 * bdrv_attach_child() eats child bs reference, so we need two @base
239 * references for two filters:
240 */
241 bdrv_ref(base);
242
243 bdrv_graph_wrlock(NULL);
244 bdrv_attach_child(top, fl1, "backing", &child_of_bds,
245 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
246 &error_abort);
247 bdrv_attach_child(fl1, base, "backing", &child_of_bds,
248 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
249 &error_abort);
250 bdrv_attach_child(fl2, base, "backing", &child_of_bds,
251 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
252 &error_abort);
253 bdrv_graph_wrunlock();
254
255 bdrv_replace_node(fl1, fl2, &error_abort);
256
257 bdrv_unref(fl2);
258 bdrv_unref(top);
259 }
260
261 /*
262 * write-to-selected node may have several DATA children, one of them may be
263 * "selected". Exclusive write permission is taken on selected child.
264 *
265 * We don't realize write handler itself, as we need only to test how permission
266 * update works.
267 */
268 typedef struct BDRVWriteToSelectedState {
269 BdrvChild *selected;
270 } BDRVWriteToSelectedState;
271
272 static void write_to_selected_perms(BlockDriverState *bs, BdrvChild *c,
273 BdrvChildRole role,
274 BlockReopenQueue *reopen_queue,
275 uint64_t perm, uint64_t shared,
276 uint64_t *nperm, uint64_t *nshared)
277 {
278 BDRVWriteToSelectedState *s = bs->opaque;
279
280 if (s->selected && c == s->selected) {
281 *nperm = BLK_PERM_WRITE;
282 *nshared = BLK_PERM_ALL & ~BLK_PERM_WRITE;
283 } else {
284 *nperm = 0;
285 *nshared = BLK_PERM_ALL;
286 }
287 }
288
289 static BlockDriver bdrv_write_to_selected = {
290 .format_name = "write-to-selected",
291 .instance_size = sizeof(BDRVWriteToSelectedState),
292 .bdrv_child_perm = write_to_selected_perms,
293 };
294
295
296 /*
297 * The following test shows that topological-sort order is required for
298 * permission update, simple DFS is not enough.
299 *
300 * Consider the block driver (write-to-selected) which has two children: one is
301 * selected so we have exclusive write access to it and for the other one we
302 * don't need any specific permissions.
303 *
304 * And, these two children has a common base child, like this:
305 * (additional "top" on top is used in test just because the only public
306 * function to update permission should get a specific child to update.
307 * Making bdrv_refresh_perms() public just for this test isn't worth it)
308 *
309 * ┌─────┐ ┌───────────────────┐ ┌─────┐
310 * │ fl2 │ ◀── │ write-to-selected │ ◀── │ top │
311 * └─────┘ └───────────────────┘ └─────┘
312 * │ │
313 * │ │ w
314 * │ ▼
315 * │ ┌──────┐
316 * │ │ fl1 │
317 * │ └──────┘
318 * │ │
319 * │ │ w
320 * │ ▼
321 * │ ┌──────┐
322 * └───────▶ │ base │
323 * └──────┘
324 *
325 * So, exclusive write is propagated.
326 *
327 * Assume, we want to select fl2 instead of fl1.
328 * So, we set some option for write-to-selected driver and do permission update.
329 *
330 * With simple DFS, if permission update goes first through
331 * write-to-selected -> fl1 -> base branch it will succeed: it firstly drop
332 * exclusive write permissions and than apply them for another BdrvChildren.
333 * But if permission update goes first through write-to-selected -> fl2 -> base
334 * branch it will fail, as when we try to update fl2->base child, old not yet
335 * updated fl1->base child will be in conflict.
336 *
337 * With topological-sort order we always update parents before children, so fl1
338 * and fl2 are both updated when we update base and there is no conflict.
339 */
340 static void test_parallel_perm_update(void)
341 {
342 BlockDriverState *top = no_perm_node("top");
343 BlockDriverState *ws =
344 bdrv_new_open_driver(&bdrv_write_to_selected, "ws", BDRV_O_RDWR,
345 &error_abort);
346 BDRVWriteToSelectedState *s = ws->opaque;
347 BlockDriverState *base = no_perm_node("base");
348 BlockDriverState *fl1 = pass_through_node("fl1");
349 BlockDriverState *fl2 = pass_through_node("fl2");
350 BdrvChild *c_fl1, *c_fl2;
351
352 /*
353 * bdrv_attach_child() eats child bs reference, so we need two @base
354 * references for two filters:
355 */
356 bdrv_ref(base);
357
358 bdrv_graph_wrlock(NULL);
359 bdrv_attach_child(top, ws, "file", &child_of_bds, BDRV_CHILD_DATA,
360 &error_abort);
361 c_fl1 = bdrv_attach_child(ws, fl1, "first", &child_of_bds,
362 BDRV_CHILD_DATA, &error_abort);
363 c_fl2 = bdrv_attach_child(ws, fl2, "second", &child_of_bds,
364 BDRV_CHILD_DATA, &error_abort);
365 bdrv_attach_child(fl1, base, "backing", &child_of_bds,
366 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
367 &error_abort);
368 bdrv_attach_child(fl2, base, "backing", &child_of_bds,
369 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
370 &error_abort);
371 bdrv_graph_wrunlock();
372
373 /* Select fl1 as first child to be active */
374 s->selected = c_fl1;
375
376 bdrv_graph_rdlock_main_loop();
377
378 bdrv_child_refresh_perms(top, top->children.lh_first, &error_abort);
379
380 assert(c_fl1->perm & BLK_PERM_WRITE);
381 assert(!(c_fl2->perm & BLK_PERM_WRITE));
382
383 /* Now, try to switch active child and update permissions */
384 s->selected = c_fl2;
385 bdrv_child_refresh_perms(top, top->children.lh_first, &error_abort);
386
387 assert(c_fl2->perm & BLK_PERM_WRITE);
388 assert(!(c_fl1->perm & BLK_PERM_WRITE));
389
390 /* Switch once more, to not care about real child order in the list */
391 s->selected = c_fl1;
392 bdrv_child_refresh_perms(top, top->children.lh_first, &error_abort);
393
394 assert(c_fl1->perm & BLK_PERM_WRITE);
395 assert(!(c_fl2->perm & BLK_PERM_WRITE));
396
397 bdrv_graph_rdunlock_main_loop();
398 bdrv_unref(top);
399 }
400
401 /*
402 * It's possible that filter required permissions allows to insert it to backing
403 * chain, like:
404 *
405 * 1. [top] -> [filter] -> [base]
406 *
407 * but doesn't allow to add it as a branch:
408 *
409 * 2. [filter] --\
410 * v
411 * [top] -> [base]
412 *
413 * So, inserting such filter should do all graph modifications and only then
414 * update permissions. If we try to go through intermediate state [2] and update
415 * permissions on it we'll fail.
416 *
417 * Let's check that bdrv_append() can append such a filter.
418 */
419 static void test_append_greedy_filter(void)
420 {
421 BlockDriverState *top = exclusive_writer_node("top");
422 BlockDriverState *base = no_perm_node("base");
423 BlockDriverState *fl = exclusive_writer_node("fl1");
424
425 bdrv_graph_wrlock(NULL);
426 bdrv_attach_child(top, base, "backing", &child_of_bds,
427 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
428 &error_abort);
429 bdrv_graph_wrunlock();
430
431 aio_context_acquire(qemu_get_aio_context());
432 bdrv_append(fl, base, &error_abort);
433 aio_context_release(qemu_get_aio_context());
434 bdrv_unref(fl);
435 bdrv_unref(top);
436 }
437
438 int main(int argc, char *argv[])
439 {
440 bdrv_init();
441 qemu_init_main_loop(&error_abort);
442
443 g_test_init(&argc, &argv, NULL);
444
445 g_test_add_func("/bdrv-graph-mod/update-perm-tree", test_update_perm_tree);
446 g_test_add_func("/bdrv-graph-mod/should-update-child",
447 test_should_update_child);
448 g_test_add_func("/bdrv-graph-mod/parallel-perm-update",
449 test_parallel_perm_update);
450 g_test_add_func("/bdrv-graph-mod/parallel-exclusive-write",
451 test_parallel_exclusive_write);
452 g_test_add_func("/bdrv-graph-mod/append-greedy-filter",
453 test_append_greedy_filter);
454
455 return g_test_run();
456 }