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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_attach_child(filter, bs, "child", &child_of_bds,
141 BDRV_CHILD_DATA, &error_abort);
142
143 ret = bdrv_append(filter, bs, NULL);
144 g_assert_cmpint(ret, <, 0);
145
146 bdrv_unref(filter);
147 blk_unref(root);
148 }
149
150 /*
151 * test_should_update_child
152 *
153 * Test that bdrv_replace_node, and concretely should_update_child
154 * do the right thing, i.e. not creating loops on the graph.
155 *
156 * The test does the following:
157 * 1. initial graph:
158 *
159 * +------+ +--------+
160 * | root | | filter |
161 * +------+ +--------+
162 * | |
163 * root| target|
164 * v v
165 * +------+ +--------+
166 * | node |<---------| target |
167 * +------+ backing +--------+
168 *
169 * 2. Append @filter above @node. If should_update_child works correctly,
170 * it understands, that backing child of @target should not be updated,
171 * as it will create a loop on node graph. Resulting picture should
172 * be the left one, not the right:
173 *
174 * +------+ +------+
175 * | root | | root |
176 * +------+ +------+
177 * | |
178 * root| root|
179 * v v
180 * +--------+ target +--------+ target
181 * | filter |--------------+ | filter |--------------+
182 * +--------+ | +--------+ |
183 * | | | ^ v
184 * backing| | backing| | +--------+
185 * v v | +-----------| target |
186 * +------+ +--------+ v backing +--------+
187 * | node |<---------| target | +------+
188 * +------+ backing +--------+ | node |
189 * +------+
190 *
191 * (good picture) (bad picture)
192 *
193 */
194 static void test_should_update_child(void)
195 {
196 BlockBackend *root = blk_new(qemu_get_aio_context(), 0, BLK_PERM_ALL);
197 BlockDriverState *bs = no_perm_node("node");
198 BlockDriverState *filter = no_perm_node("filter");
199 BlockDriverState *target = no_perm_node("target");
200
201 blk_insert_bs(root, bs, &error_abort);
202
203 bdrv_set_backing_hd(target, bs, &error_abort);
204
205 g_assert(target->backing->bs == bs);
206 bdrv_attach_child(filter, target, "target", &child_of_bds,
207 BDRV_CHILD_DATA, &error_abort);
208 bdrv_append(filter, bs, &error_abort);
209 g_assert(target->backing->bs == bs);
210
211 bdrv_unref(filter);
212 bdrv_unref(bs);
213 blk_unref(root);
214 }
215
216 /*
217 * test_parallel_exclusive_write
218 *
219 * Check that when we replace node, old permissions of the node being removed
220 * doesn't break the replacement.
221 */
222 static void test_parallel_exclusive_write(void)
223 {
224 BlockDriverState *top = exclusive_writer_node("top");
225 BlockDriverState *base = no_perm_node("base");
226 BlockDriverState *fl1 = pass_through_node("fl1");
227 BlockDriverState *fl2 = pass_through_node("fl2");
228
229 /*
230 * bdrv_attach_child() eats child bs reference, so we need two @base
231 * references for two filters:
232 */
233 bdrv_ref(base);
234
235 bdrv_attach_child(top, fl1, "backing", &child_of_bds,
236 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
237 &error_abort);
238 bdrv_attach_child(fl1, base, "backing", &child_of_bds,
239 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
240 &error_abort);
241 bdrv_attach_child(fl2, base, "backing", &child_of_bds,
242 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
243 &error_abort);
244
245 bdrv_replace_node(fl1, fl2, &error_abort);
246
247 bdrv_unref(fl2);
248 bdrv_unref(top);
249 }
250
251 /*
252 * write-to-selected node may have several DATA children, one of them may be
253 * "selected". Exclusive write permission is taken on selected child.
254 *
255 * We don't realize write handler itself, as we need only to test how permission
256 * update works.
257 */
258 typedef struct BDRVWriteToSelectedState {
259 BdrvChild *selected;
260 } BDRVWriteToSelectedState;
261
262 static void write_to_selected_perms(BlockDriverState *bs, BdrvChild *c,
263 BdrvChildRole role,
264 BlockReopenQueue *reopen_queue,
265 uint64_t perm, uint64_t shared,
266 uint64_t *nperm, uint64_t *nshared)
267 {
268 BDRVWriteToSelectedState *s = bs->opaque;
269
270 if (s->selected && c == s->selected) {
271 *nperm = BLK_PERM_WRITE;
272 *nshared = BLK_PERM_ALL & ~BLK_PERM_WRITE;
273 } else {
274 *nperm = 0;
275 *nshared = BLK_PERM_ALL;
276 }
277 }
278
279 static BlockDriver bdrv_write_to_selected = {
280 .format_name = "write-to-selected",
281 .instance_size = sizeof(BDRVWriteToSelectedState),
282 .bdrv_child_perm = write_to_selected_perms,
283 };
284
285
286 /*
287 * The following test shows that topological-sort order is required for
288 * permission update, simple DFS is not enough.
289 *
290 * Consider the block driver (write-to-selected) which has two children: one is
291 * selected so we have exclusive write access to it and for the other one we
292 * don't need any specific permissions.
293 *
294 * And, these two children has a common base child, like this:
295 * (additional "top" on top is used in test just because the only public
296 * function to update permission should get a specific child to update.
297 * Making bdrv_refresh_perms() public just for this test isn't worth it)
298 *
299 * ┌─────┐ ┌───────────────────┐ ┌─────┐
300 * │ fl2 │ ◀── │ write-to-selected │ ◀── │ top │
301 * └─────┘ └───────────────────┘ └─────┘
302 * │ │
303 * │ │ w
304 * │ ▼
305 * │ ┌──────┐
306 * │ │ fl1 │
307 * │ └──────┘
308 * │ │
309 * │ │ w
310 * │ ▼
311 * │ ┌──────┐
312 * └───────▶ │ base │
313 * └──────┘
314 *
315 * So, exclusive write is propagated.
316 *
317 * Assume, we want to select fl2 instead of fl1.
318 * So, we set some option for write-to-selected driver and do permission update.
319 *
320 * With simple DFS, if permission update goes first through
321 * write-to-selected -> fl1 -> base branch it will succeed: it firstly drop
322 * exclusive write permissions and than apply them for another BdrvChildren.
323 * But if permission update goes first through write-to-selected -> fl2 -> base
324 * branch it will fail, as when we try to update fl2->base child, old not yet
325 * updated fl1->base child will be in conflict.
326 *
327 * With topological-sort order we always update parents before children, so fl1
328 * and fl2 are both updated when we update base and there is no conflict.
329 */
330 static void test_parallel_perm_update(void)
331 {
332 BlockDriverState *top = no_perm_node("top");
333 BlockDriverState *ws =
334 bdrv_new_open_driver(&bdrv_write_to_selected, "ws", BDRV_O_RDWR,
335 &error_abort);
336 BDRVWriteToSelectedState *s = ws->opaque;
337 BlockDriverState *base = no_perm_node("base");
338 BlockDriverState *fl1 = pass_through_node("fl1");
339 BlockDriverState *fl2 = pass_through_node("fl2");
340 BdrvChild *c_fl1, *c_fl2;
341
342 /*
343 * bdrv_attach_child() eats child bs reference, so we need two @base
344 * references for two filters:
345 */
346 bdrv_ref(base);
347
348 bdrv_attach_child(top, ws, "file", &child_of_bds, BDRV_CHILD_DATA,
349 &error_abort);
350 c_fl1 = bdrv_attach_child(ws, fl1, "first", &child_of_bds,
351 BDRV_CHILD_DATA, &error_abort);
352 c_fl2 = bdrv_attach_child(ws, fl2, "second", &child_of_bds,
353 BDRV_CHILD_DATA, &error_abort);
354 bdrv_attach_child(fl1, base, "backing", &child_of_bds,
355 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
356 &error_abort);
357 bdrv_attach_child(fl2, base, "backing", &child_of_bds,
358 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
359 &error_abort);
360
361 /* Select fl1 as first child to be active */
362 s->selected = c_fl1;
363 bdrv_child_refresh_perms(top, top->children.lh_first, &error_abort);
364
365 assert(c_fl1->perm & BLK_PERM_WRITE);
366 assert(!(c_fl2->perm & BLK_PERM_WRITE));
367
368 /* Now, try to switch active child and update permissions */
369 s->selected = c_fl2;
370 bdrv_child_refresh_perms(top, top->children.lh_first, &error_abort);
371
372 assert(c_fl2->perm & BLK_PERM_WRITE);
373 assert(!(c_fl1->perm & BLK_PERM_WRITE));
374
375 /* Switch once more, to not care about real child order in the list */
376 s->selected = c_fl1;
377 bdrv_child_refresh_perms(top, top->children.lh_first, &error_abort);
378
379 assert(c_fl1->perm & BLK_PERM_WRITE);
380 assert(!(c_fl2->perm & BLK_PERM_WRITE));
381
382 bdrv_unref(top);
383 }
384
385 /*
386 * It's possible that filter required permissions allows to insert it to backing
387 * chain, like:
388 *
389 * 1. [top] -> [filter] -> [base]
390 *
391 * but doesn't allow to add it as a branch:
392 *
393 * 2. [filter] --\
394 * v
395 * [top] -> [base]
396 *
397 * So, inserting such filter should do all graph modifications and only then
398 * update permissions. If we try to go through intermediate state [2] and update
399 * permissions on it we'll fail.
400 *
401 * Let's check that bdrv_append() can append such a filter.
402 */
403 static void test_append_greedy_filter(void)
404 {
405 BlockDriverState *top = exclusive_writer_node("top");
406 BlockDriverState *base = no_perm_node("base");
407 BlockDriverState *fl = exclusive_writer_node("fl1");
408
409 bdrv_attach_child(top, base, "backing", &child_of_bds,
410 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
411 &error_abort);
412
413 bdrv_append(fl, base, &error_abort);
414 bdrv_unref(fl);
415 bdrv_unref(top);
416 }
417
418 int main(int argc, char *argv[])
419 {
420 bdrv_init();
421 qemu_init_main_loop(&error_abort);
422
423 g_test_init(&argc, &argv, NULL);
424
425 g_test_add_func("/bdrv-graph-mod/update-perm-tree", test_update_perm_tree);
426 g_test_add_func("/bdrv-graph-mod/should-update-child",
427 test_should_update_child);
428 g_test_add_func("/bdrv-graph-mod/parallel-perm-update",
429 test_parallel_perm_update);
430 g_test_add_func("/bdrv-graph-mod/parallel-exclusive-write",
431 test_parallel_exclusive_write);
432 g_test_add_func("/bdrv-graph-mod/append-greedy-filter",
433 test_append_greedy_filter);
434
435 return g_test_run();
436 }