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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 bdrv_graph_wrlock(NULL);
210 g_assert(target->backing->bs == bs);
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
218 bdrv_graph_rdlock_main_loop();
219 g_assert(target->backing->bs == bs);
220 bdrv_graph_rdunlock_main_loop();
221
222 bdrv_unref(filter);
223 bdrv_unref(bs);
224 blk_unref(root);
225 }
226
227 /*
228 * test_parallel_exclusive_write
229 *
230 * Check that when we replace node, old permissions of the node being removed
231 * doesn't break the replacement.
232 */
233 static void test_parallel_exclusive_write(void)
234 {
235 BlockDriverState *top = exclusive_writer_node("top");
236 BlockDriverState *base = no_perm_node("base");
237 BlockDriverState *fl1 = pass_through_node("fl1");
238 BlockDriverState *fl2 = pass_through_node("fl2");
239
240 bdrv_drained_begin(fl1);
241 bdrv_drained_begin(fl2);
242
243 /*
244 * bdrv_attach_child() eats child bs reference, so we need two @base
245 * references for two filters. We also need an additional @fl1 reference so
246 * that it still exists when we want to undrain it.
247 */
248 bdrv_ref(base);
249 bdrv_ref(fl1);
250
251 bdrv_graph_wrlock(NULL);
252 bdrv_attach_child(top, fl1, "backing", &child_of_bds,
253 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
254 &error_abort);
255 bdrv_attach_child(fl1, base, "backing", &child_of_bds,
256 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
257 &error_abort);
258 bdrv_attach_child(fl2, base, "backing", &child_of_bds,
259 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
260 &error_abort);
261
262 bdrv_replace_node(fl1, fl2, &error_abort);
263 bdrv_graph_wrunlock();
264
265 bdrv_drained_end(fl2);
266 bdrv_drained_end(fl1);
267
268 bdrv_unref(fl1);
269 bdrv_unref(fl2);
270 bdrv_unref(top);
271 }
272
273 /*
274 * write-to-selected node may have several DATA children, one of them may be
275 * "selected". Exclusive write permission is taken on selected child.
276 *
277 * We don't realize write handler itself, as we need only to test how permission
278 * update works.
279 */
280 typedef struct BDRVWriteToSelectedState {
281 BdrvChild *selected;
282 } BDRVWriteToSelectedState;
283
284 static void write_to_selected_perms(BlockDriverState *bs, BdrvChild *c,
285 BdrvChildRole role,
286 BlockReopenQueue *reopen_queue,
287 uint64_t perm, uint64_t shared,
288 uint64_t *nperm, uint64_t *nshared)
289 {
290 BDRVWriteToSelectedState *s = bs->opaque;
291
292 if (s->selected && c == s->selected) {
293 *nperm = BLK_PERM_WRITE;
294 *nshared = BLK_PERM_ALL & ~BLK_PERM_WRITE;
295 } else {
296 *nperm = 0;
297 *nshared = BLK_PERM_ALL;
298 }
299 }
300
301 static BlockDriver bdrv_write_to_selected = {
302 .format_name = "write-to-selected",
303 .instance_size = sizeof(BDRVWriteToSelectedState),
304 .bdrv_child_perm = write_to_selected_perms,
305 };
306
307
308 /*
309 * The following test shows that topological-sort order is required for
310 * permission update, simple DFS is not enough.
311 *
312 * Consider the block driver (write-to-selected) which has two children: one is
313 * selected so we have exclusive write access to it and for the other one we
314 * don't need any specific permissions.
315 *
316 * And, these two children has a common base child, like this:
317 * (additional "top" on top is used in test just because the only public
318 * function to update permission should get a specific child to update.
319 * Making bdrv_refresh_perms() public just for this test isn't worth it)
320 *
321 * ┌─────┐ ┌───────────────────┐ ┌─────┐
322 * │ fl2 │ ◀── │ write-to-selected │ ◀── │ top │
323 * └─────┘ └───────────────────┘ └─────┘
324 * │ │
325 * │ │ w
326 * │ ▼
327 * │ ┌──────┐
328 * │ │ fl1 │
329 * │ └──────┘
330 * │ │
331 * │ │ w
332 * │ ▼
333 * │ ┌──────┐
334 * └───────▶ │ base │
335 * └──────┘
336 *
337 * So, exclusive write is propagated.
338 *
339 * Assume, we want to select fl2 instead of fl1.
340 * So, we set some option for write-to-selected driver and do permission update.
341 *
342 * With simple DFS, if permission update goes first through
343 * write-to-selected -> fl1 -> base branch it will succeed: it firstly drop
344 * exclusive write permissions and than apply them for another BdrvChildren.
345 * But if permission update goes first through write-to-selected -> fl2 -> base
346 * branch it will fail, as when we try to update fl2->base child, old not yet
347 * updated fl1->base child will be in conflict.
348 *
349 * With topological-sort order we always update parents before children, so fl1
350 * and fl2 are both updated when we update base and there is no conflict.
351 */
352 static void test_parallel_perm_update(void)
353 {
354 BlockDriverState *top = no_perm_node("top");
355 BlockDriverState *ws =
356 bdrv_new_open_driver(&bdrv_write_to_selected, "ws", BDRV_O_RDWR,
357 &error_abort);
358 BDRVWriteToSelectedState *s = ws->opaque;
359 BlockDriverState *base = no_perm_node("base");
360 BlockDriverState *fl1 = pass_through_node("fl1");
361 BlockDriverState *fl2 = pass_through_node("fl2");
362 BdrvChild *c_fl1, *c_fl2;
363
364 /*
365 * bdrv_attach_child() eats child bs reference, so we need two @base
366 * references for two filters:
367 */
368 bdrv_ref(base);
369
370 bdrv_graph_wrlock(NULL);
371 bdrv_attach_child(top, ws, "file", &child_of_bds, BDRV_CHILD_DATA,
372 &error_abort);
373 c_fl1 = bdrv_attach_child(ws, fl1, "first", &child_of_bds,
374 BDRV_CHILD_DATA, &error_abort);
375 c_fl2 = bdrv_attach_child(ws, fl2, "second", &child_of_bds,
376 BDRV_CHILD_DATA, &error_abort);
377 bdrv_attach_child(fl1, base, "backing", &child_of_bds,
378 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
379 &error_abort);
380 bdrv_attach_child(fl2, base, "backing", &child_of_bds,
381 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
382 &error_abort);
383 bdrv_graph_wrunlock();
384
385 /* Select fl1 as first child to be active */
386 s->selected = c_fl1;
387
388 bdrv_graph_rdlock_main_loop();
389
390 bdrv_child_refresh_perms(top, top->children.lh_first, &error_abort);
391
392 assert(c_fl1->perm & BLK_PERM_WRITE);
393 assert(!(c_fl2->perm & BLK_PERM_WRITE));
394
395 /* Now, try to switch active child and update permissions */
396 s->selected = c_fl2;
397 bdrv_child_refresh_perms(top, top->children.lh_first, &error_abort);
398
399 assert(c_fl2->perm & BLK_PERM_WRITE);
400 assert(!(c_fl1->perm & BLK_PERM_WRITE));
401
402 /* Switch once more, to not care about real child order in the list */
403 s->selected = c_fl1;
404 bdrv_child_refresh_perms(top, top->children.lh_first, &error_abort);
405
406 assert(c_fl1->perm & BLK_PERM_WRITE);
407 assert(!(c_fl2->perm & BLK_PERM_WRITE));
408
409 bdrv_graph_rdunlock_main_loop();
410 bdrv_unref(top);
411 }
412
413 /*
414 * It's possible that filter required permissions allows to insert it to backing
415 * chain, like:
416 *
417 * 1. [top] -> [filter] -> [base]
418 *
419 * but doesn't allow to add it as a branch:
420 *
421 * 2. [filter] --\
422 * v
423 * [top] -> [base]
424 *
425 * So, inserting such filter should do all graph modifications and only then
426 * update permissions. If we try to go through intermediate state [2] and update
427 * permissions on it we'll fail.
428 *
429 * Let's check that bdrv_append() can append such a filter.
430 */
431 static void test_append_greedy_filter(void)
432 {
433 BlockDriverState *top = exclusive_writer_node("top");
434 BlockDriverState *base = no_perm_node("base");
435 BlockDriverState *fl = exclusive_writer_node("fl1");
436
437 bdrv_graph_wrlock(NULL);
438 bdrv_attach_child(top, base, "backing", &child_of_bds,
439 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
440 &error_abort);
441 bdrv_graph_wrunlock();
442
443 aio_context_acquire(qemu_get_aio_context());
444 bdrv_append(fl, base, &error_abort);
445 aio_context_release(qemu_get_aio_context());
446 bdrv_unref(fl);
447 bdrv_unref(top);
448 }
449
450 int main(int argc, char *argv[])
451 {
452 bdrv_init();
453 qemu_init_main_loop(&error_abort);
454
455 g_test_init(&argc, &argv, NULL);
456
457 g_test_add_func("/bdrv-graph-mod/update-perm-tree", test_update_perm_tree);
458 g_test_add_func("/bdrv-graph-mod/should-update-child",
459 test_should_update_child);
460 g_test_add_func("/bdrv-graph-mod/parallel-perm-update",
461 test_parallel_perm_update);
462 g_test_add_func("/bdrv-graph-mod/parallel-exclusive-write",
463 test_parallel_exclusive_write);
464 g_test_add_func("/bdrv-graph-mod/append-greedy-filter",
465 test_append_greedy_filter);
466
467 return g_test_run();
468 }