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 "system/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_drain_all_begin(); 141 bdrv_graph_wrlock(); 142 bdrv_attach_child(filter, bs, "child", &child_of_bds, 143 BDRV_CHILD_DATA, &error_abort); 144 bdrv_graph_wrunlock(); 145 bdrv_drain_all_end(); 146 147 ret = bdrv_append(filter, bs, NULL); 148 g_assert_cmpint(ret, <, 0); 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_drain_all_begin(); 210 bdrv_graph_wrlock(); 211 g_assert(target->backing->bs == bs); 212 bdrv_attach_child(filter, target, "target", &child_of_bds, 213 BDRV_CHILD_DATA, &error_abort); 214 bdrv_graph_wrunlock(); 215 bdrv_drain_all_end(); 216 bdrv_append(filter, bs, &error_abort); 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_drain_all_begin(); 252 bdrv_graph_wrlock(); 253 bdrv_attach_child(top, fl1, "backing", &child_of_bds, 254 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY, 255 &error_abort); 256 bdrv_attach_child(fl1, base, "backing", &child_of_bds, 257 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY, 258 &error_abort); 259 bdrv_attach_child(fl2, base, "backing", &child_of_bds, 260 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY, 261 &error_abort); 262 263 bdrv_replace_node(fl1, fl2, &error_abort); 264 bdrv_graph_wrunlock(); 265 bdrv_drain_all_end(); 266 267 bdrv_drained_end(fl2); 268 bdrv_drained_end(fl1); 269 270 bdrv_unref(fl1); 271 bdrv_unref(fl2); 272 bdrv_unref(top); 273 } 274 275 /* 276 * write-to-selected node may have several DATA children, one of them may be 277 * "selected". Exclusive write permission is taken on selected child. 278 * 279 * We don't realize write handler itself, as we need only to test how permission 280 * update works. 281 */ 282 typedef struct BDRVWriteToSelectedState { 283 BdrvChild *selected; 284 } BDRVWriteToSelectedState; 285 286 static void write_to_selected_perms(BlockDriverState *bs, BdrvChild *c, 287 BdrvChildRole role, 288 BlockReopenQueue *reopen_queue, 289 uint64_t perm, uint64_t shared, 290 uint64_t *nperm, uint64_t *nshared) 291 { 292 BDRVWriteToSelectedState *s = bs->opaque; 293 294 if (s->selected && c == s->selected) { 295 *nperm = BLK_PERM_WRITE; 296 *nshared = BLK_PERM_ALL & ~BLK_PERM_WRITE; 297 } else { 298 *nperm = 0; 299 *nshared = BLK_PERM_ALL; 300 } 301 } 302 303 static BlockDriver bdrv_write_to_selected = { 304 .format_name = "write-to-selected", 305 .instance_size = sizeof(BDRVWriteToSelectedState), 306 .bdrv_child_perm = write_to_selected_perms, 307 }; 308 309 310 /* 311 * The following test shows that topological-sort order is required for 312 * permission update, simple DFS is not enough. 313 * 314 * Consider the block driver (write-to-selected) which has two children: one is 315 * selected so we have exclusive write access to it and for the other one we 316 * don't need any specific permissions. 317 * 318 * And, these two children has a common base child, like this: 319 * (additional "top" on top is used in test just because the only public 320 * function to update permission should get a specific child to update. 321 * Making bdrv_refresh_perms() public just for this test isn't worth it) 322 * 323 * ┌─────┐ ┌───────────────────┐ ┌─────┐ 324 * │ fl2 │ ◀── │ write-to-selected │ ◀── │ top │ 325 * └─────┘ └───────────────────┘ └─────┘ 326 * │ │ 327 * │ │ w 328 * │ ▼ 329 * │ ┌──────┐ 330 * │ │ fl1 │ 331 * │ └──────┘ 332 * │ │ 333 * │ │ w 334 * │ ▼ 335 * │ ┌──────┐ 336 * └───────▶ │ base │ 337 * └──────┘ 338 * 339 * So, exclusive write is propagated. 340 * 341 * Assume, we want to select fl2 instead of fl1. 342 * So, we set some option for write-to-selected driver and do permission update. 343 * 344 * With simple DFS, if permission update goes first through 345 * write-to-selected -> fl1 -> base branch it will succeed: it firstly drop 346 * exclusive write permissions and than apply them for another BdrvChildren. 347 * But if permission update goes first through write-to-selected -> fl2 -> base 348 * branch it will fail, as when we try to update fl2->base child, old not yet 349 * updated fl1->base child will be in conflict. 350 * 351 * With topological-sort order we always update parents before children, so fl1 352 * and fl2 are both updated when we update base and there is no conflict. 353 */ 354 static void test_parallel_perm_update(void) 355 { 356 BlockDriverState *top = no_perm_node("top"); 357 BlockDriverState *ws = 358 bdrv_new_open_driver(&bdrv_write_to_selected, "ws", BDRV_O_RDWR, 359 &error_abort); 360 BDRVWriteToSelectedState *s = ws->opaque; 361 BlockDriverState *base = no_perm_node("base"); 362 BlockDriverState *fl1 = pass_through_node("fl1"); 363 BlockDriverState *fl2 = pass_through_node("fl2"); 364 BdrvChild *c_fl1, *c_fl2; 365 366 /* 367 * bdrv_attach_child() eats child bs reference, so we need two @base 368 * references for two filters: 369 */ 370 bdrv_ref(base); 371 372 bdrv_drain_all_begin(); 373 bdrv_graph_wrlock(); 374 bdrv_attach_child(top, ws, "file", &child_of_bds, BDRV_CHILD_DATA, 375 &error_abort); 376 c_fl1 = bdrv_attach_child(ws, fl1, "first", &child_of_bds, 377 BDRV_CHILD_DATA, &error_abort); 378 c_fl2 = bdrv_attach_child(ws, fl2, "second", &child_of_bds, 379 BDRV_CHILD_DATA, &error_abort); 380 bdrv_attach_child(fl1, base, "backing", &child_of_bds, 381 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY, 382 &error_abort); 383 bdrv_attach_child(fl2, base, "backing", &child_of_bds, 384 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY, 385 &error_abort); 386 bdrv_graph_wrunlock(); 387 bdrv_drain_all_end(); 388 389 /* Select fl1 as first child to be active */ 390 s->selected = c_fl1; 391 392 bdrv_graph_rdlock_main_loop(); 393 394 bdrv_child_refresh_perms(top, top->children.lh_first, &error_abort); 395 396 assert(c_fl1->perm & BLK_PERM_WRITE); 397 assert(!(c_fl2->perm & BLK_PERM_WRITE)); 398 399 /* Now, try to switch active child and update permissions */ 400 s->selected = c_fl2; 401 bdrv_child_refresh_perms(top, top->children.lh_first, &error_abort); 402 403 assert(c_fl2->perm & BLK_PERM_WRITE); 404 assert(!(c_fl1->perm & BLK_PERM_WRITE)); 405 406 /* Switch once more, to not care about real child order in the list */ 407 s->selected = c_fl1; 408 bdrv_child_refresh_perms(top, top->children.lh_first, &error_abort); 409 410 assert(c_fl1->perm & BLK_PERM_WRITE); 411 assert(!(c_fl2->perm & BLK_PERM_WRITE)); 412 413 bdrv_graph_rdunlock_main_loop(); 414 bdrv_unref(top); 415 } 416 417 /* 418 * It's possible that filter required permissions allows to insert it to backing 419 * chain, like: 420 * 421 * 1. [top] -> [filter] -> [base] 422 * 423 * but doesn't allow to add it as a branch: 424 * 425 * 2. [filter] --\ 426 * v 427 * [top] -> [base] 428 * 429 * So, inserting such filter should do all graph modifications and only then 430 * update permissions. If we try to go through intermediate state [2] and update 431 * permissions on it we'll fail. 432 * 433 * Let's check that bdrv_append() can append such a filter. 434 */ 435 static void test_append_greedy_filter(void) 436 { 437 BlockDriverState *top = exclusive_writer_node("top"); 438 BlockDriverState *base = no_perm_node("base"); 439 BlockDriverState *fl = exclusive_writer_node("fl1"); 440 441 bdrv_drain_all_begin(); 442 bdrv_graph_wrlock(); 443 bdrv_attach_child(top, base, "backing", &child_of_bds, 444 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY, 445 &error_abort); 446 bdrv_graph_wrunlock(); 447 bdrv_drain_all_end(); 448 449 bdrv_append(fl, base, &error_abort); 450 bdrv_unref(fl); 451 bdrv_unref(top); 452 } 453 454 int main(int argc, char *argv[]) 455 { 456 bdrv_init(); 457 qemu_init_main_loop(&error_abort); 458 459 g_test_init(&argc, &argv, NULL); 460 461 g_test_add_func("/bdrv-graph-mod/update-perm-tree", test_update_perm_tree); 462 g_test_add_func("/bdrv-graph-mod/should-update-child", 463 test_should_update_child); 464 g_test_add_func("/bdrv-graph-mod/parallel-perm-update", 465 test_parallel_perm_update); 466 g_test_add_func("/bdrv-graph-mod/parallel-exclusive-write", 467 test_parallel_exclusive_write); 468 g_test_add_func("/bdrv-graph-mod/append-greedy-filter", 469 test_append_greedy_filter); 470 471 return g_test_run(); 472 } 473