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(); 141 bdrv_attach_child(filter, bs, "child", &child_of_bds, 142 BDRV_CHILD_DATA, &error_abort); 143 bdrv_graph_wrunlock(); 144 145 ret = bdrv_append(filter, bs, NULL); 146 g_assert_cmpint(ret, <, 0); 147 148 bdrv_unref(filter); 149 blk_unref(root); 150 } 151 152 /* 153 * test_should_update_child 154 * 155 * Test that bdrv_replace_node, and concretely should_update_child 156 * do the right thing, i.e. not creating loops on the graph. 157 * 158 * The test does the following: 159 * 1. initial graph: 160 * 161 * +------+ +--------+ 162 * | root | | filter | 163 * +------+ +--------+ 164 * | | 165 * root| target| 166 * v v 167 * +------+ +--------+ 168 * | node |<---------| target | 169 * +------+ backing +--------+ 170 * 171 * 2. Append @filter above @node. If should_update_child works correctly, 172 * it understands, that backing child of @target should not be updated, 173 * as it will create a loop on node graph. Resulting picture should 174 * be the left one, not the right: 175 * 176 * +------+ +------+ 177 * | root | | root | 178 * +------+ +------+ 179 * | | 180 * root| root| 181 * v v 182 * +--------+ target +--------+ target 183 * | filter |--------------+ | filter |--------------+ 184 * +--------+ | +--------+ | 185 * | | | ^ v 186 * backing| | backing| | +--------+ 187 * v v | +-----------| target | 188 * +------+ +--------+ v backing +--------+ 189 * | node |<---------| target | +------+ 190 * +------+ backing +--------+ | node | 191 * +------+ 192 * 193 * (good picture) (bad picture) 194 * 195 */ 196 static void test_should_update_child(void) 197 { 198 BlockBackend *root = blk_new(qemu_get_aio_context(), 0, BLK_PERM_ALL); 199 BlockDriverState *bs = no_perm_node("node"); 200 BlockDriverState *filter = no_perm_node("filter"); 201 BlockDriverState *target = no_perm_node("target"); 202 203 blk_insert_bs(root, bs, &error_abort); 204 205 bdrv_set_backing_hd(target, bs, &error_abort); 206 207 bdrv_graph_wrlock(); 208 g_assert(target->backing->bs == bs); 209 bdrv_attach_child(filter, target, "target", &child_of_bds, 210 BDRV_CHILD_DATA, &error_abort); 211 bdrv_graph_wrunlock(); 212 bdrv_append(filter, bs, &error_abort); 213 214 bdrv_graph_rdlock_main_loop(); 215 g_assert(target->backing->bs == bs); 216 bdrv_graph_rdunlock_main_loop(); 217 218 bdrv_unref(filter); 219 bdrv_unref(bs); 220 blk_unref(root); 221 } 222 223 /* 224 * test_parallel_exclusive_write 225 * 226 * Check that when we replace node, old permissions of the node being removed 227 * doesn't break the replacement. 228 */ 229 static void test_parallel_exclusive_write(void) 230 { 231 BlockDriverState *top = exclusive_writer_node("top"); 232 BlockDriverState *base = no_perm_node("base"); 233 BlockDriverState *fl1 = pass_through_node("fl1"); 234 BlockDriverState *fl2 = pass_through_node("fl2"); 235 236 bdrv_drained_begin(fl1); 237 bdrv_drained_begin(fl2); 238 239 /* 240 * bdrv_attach_child() eats child bs reference, so we need two @base 241 * references for two filters. We also need an additional @fl1 reference so 242 * that it still exists when we want to undrain it. 243 */ 244 bdrv_ref(base); 245 bdrv_ref(fl1); 246 247 bdrv_graph_wrlock(); 248 bdrv_attach_child(top, fl1, "backing", &child_of_bds, 249 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY, 250 &error_abort); 251 bdrv_attach_child(fl1, base, "backing", &child_of_bds, 252 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY, 253 &error_abort); 254 bdrv_attach_child(fl2, base, "backing", &child_of_bds, 255 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY, 256 &error_abort); 257 258 bdrv_replace_node(fl1, fl2, &error_abort); 259 bdrv_graph_wrunlock(); 260 261 bdrv_drained_end(fl2); 262 bdrv_drained_end(fl1); 263 264 bdrv_unref(fl1); 265 bdrv_unref(fl2); 266 bdrv_unref(top); 267 } 268 269 /* 270 * write-to-selected node may have several DATA children, one of them may be 271 * "selected". Exclusive write permission is taken on selected child. 272 * 273 * We don't realize write handler itself, as we need only to test how permission 274 * update works. 275 */ 276 typedef struct BDRVWriteToSelectedState { 277 BdrvChild *selected; 278 } BDRVWriteToSelectedState; 279 280 static void write_to_selected_perms(BlockDriverState *bs, BdrvChild *c, 281 BdrvChildRole role, 282 BlockReopenQueue *reopen_queue, 283 uint64_t perm, uint64_t shared, 284 uint64_t *nperm, uint64_t *nshared) 285 { 286 BDRVWriteToSelectedState *s = bs->opaque; 287 288 if (s->selected && c == s->selected) { 289 *nperm = BLK_PERM_WRITE; 290 *nshared = BLK_PERM_ALL & ~BLK_PERM_WRITE; 291 } else { 292 *nperm = 0; 293 *nshared = BLK_PERM_ALL; 294 } 295 } 296 297 static BlockDriver bdrv_write_to_selected = { 298 .format_name = "write-to-selected", 299 .instance_size = sizeof(BDRVWriteToSelectedState), 300 .bdrv_child_perm = write_to_selected_perms, 301 }; 302 303 304 /* 305 * The following test shows that topological-sort order is required for 306 * permission update, simple DFS is not enough. 307 * 308 * Consider the block driver (write-to-selected) which has two children: one is 309 * selected so we have exclusive write access to it and for the other one we 310 * don't need any specific permissions. 311 * 312 * And, these two children has a common base child, like this: 313 * (additional "top" on top is used in test just because the only public 314 * function to update permission should get a specific child to update. 315 * Making bdrv_refresh_perms() public just for this test isn't worth it) 316 * 317 * ┌─────┐ ┌───────────────────┐ ┌─────┐ 318 * │ fl2 │ ◀── │ write-to-selected │ ◀── │ top │ 319 * └─────┘ └───────────────────┘ └─────┘ 320 * │ │ 321 * │ │ w 322 * │ ▼ 323 * │ ┌──────┐ 324 * │ │ fl1 │ 325 * │ └──────┘ 326 * │ │ 327 * │ │ w 328 * │ ▼ 329 * │ ┌──────┐ 330 * └───────▶ │ base │ 331 * └──────┘ 332 * 333 * So, exclusive write is propagated. 334 * 335 * Assume, we want to select fl2 instead of fl1. 336 * So, we set some option for write-to-selected driver and do permission update. 337 * 338 * With simple DFS, if permission update goes first through 339 * write-to-selected -> fl1 -> base branch it will succeed: it firstly drop 340 * exclusive write permissions and than apply them for another BdrvChildren. 341 * But if permission update goes first through write-to-selected -> fl2 -> base 342 * branch it will fail, as when we try to update fl2->base child, old not yet 343 * updated fl1->base child will be in conflict. 344 * 345 * With topological-sort order we always update parents before children, so fl1 346 * and fl2 are both updated when we update base and there is no conflict. 347 */ 348 static void test_parallel_perm_update(void) 349 { 350 BlockDriverState *top = no_perm_node("top"); 351 BlockDriverState *ws = 352 bdrv_new_open_driver(&bdrv_write_to_selected, "ws", BDRV_O_RDWR, 353 &error_abort); 354 BDRVWriteToSelectedState *s = ws->opaque; 355 BlockDriverState *base = no_perm_node("base"); 356 BlockDriverState *fl1 = pass_through_node("fl1"); 357 BlockDriverState *fl2 = pass_through_node("fl2"); 358 BdrvChild *c_fl1, *c_fl2; 359 360 /* 361 * bdrv_attach_child() eats child bs reference, so we need two @base 362 * references for two filters: 363 */ 364 bdrv_ref(base); 365 366 bdrv_graph_wrlock(); 367 bdrv_attach_child(top, ws, "file", &child_of_bds, BDRV_CHILD_DATA, 368 &error_abort); 369 c_fl1 = bdrv_attach_child(ws, fl1, "first", &child_of_bds, 370 BDRV_CHILD_DATA, &error_abort); 371 c_fl2 = bdrv_attach_child(ws, fl2, "second", &child_of_bds, 372 BDRV_CHILD_DATA, &error_abort); 373 bdrv_attach_child(fl1, base, "backing", &child_of_bds, 374 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY, 375 &error_abort); 376 bdrv_attach_child(fl2, base, "backing", &child_of_bds, 377 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY, 378 &error_abort); 379 bdrv_graph_wrunlock(); 380 381 /* Select fl1 as first child to be active */ 382 s->selected = c_fl1; 383 384 bdrv_graph_rdlock_main_loop(); 385 386 bdrv_child_refresh_perms(top, top->children.lh_first, &error_abort); 387 388 assert(c_fl1->perm & BLK_PERM_WRITE); 389 assert(!(c_fl2->perm & BLK_PERM_WRITE)); 390 391 /* Now, try to switch active child and update permissions */ 392 s->selected = c_fl2; 393 bdrv_child_refresh_perms(top, top->children.lh_first, &error_abort); 394 395 assert(c_fl2->perm & BLK_PERM_WRITE); 396 assert(!(c_fl1->perm & BLK_PERM_WRITE)); 397 398 /* Switch once more, to not care about real child order in the list */ 399 s->selected = c_fl1; 400 bdrv_child_refresh_perms(top, top->children.lh_first, &error_abort); 401 402 assert(c_fl1->perm & BLK_PERM_WRITE); 403 assert(!(c_fl2->perm & BLK_PERM_WRITE)); 404 405 bdrv_graph_rdunlock_main_loop(); 406 bdrv_unref(top); 407 } 408 409 /* 410 * It's possible that filter required permissions allows to insert it to backing 411 * chain, like: 412 * 413 * 1. [top] -> [filter] -> [base] 414 * 415 * but doesn't allow to add it as a branch: 416 * 417 * 2. [filter] --\ 418 * v 419 * [top] -> [base] 420 * 421 * So, inserting such filter should do all graph modifications and only then 422 * update permissions. If we try to go through intermediate state [2] and update 423 * permissions on it we'll fail. 424 * 425 * Let's check that bdrv_append() can append such a filter. 426 */ 427 static void test_append_greedy_filter(void) 428 { 429 BlockDriverState *top = exclusive_writer_node("top"); 430 BlockDriverState *base = no_perm_node("base"); 431 BlockDriverState *fl = exclusive_writer_node("fl1"); 432 433 bdrv_graph_wrlock(); 434 bdrv_attach_child(top, base, "backing", &child_of_bds, 435 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY, 436 &error_abort); 437 bdrv_graph_wrunlock(); 438 439 bdrv_append(fl, base, &error_abort); 440 bdrv_unref(fl); 441 bdrv_unref(top); 442 } 443 444 int main(int argc, char *argv[]) 445 { 446 bdrv_init(); 447 qemu_init_main_loop(&error_abort); 448 449 g_test_init(&argc, &argv, NULL); 450 451 g_test_add_func("/bdrv-graph-mod/update-perm-tree", test_update_perm_tree); 452 g_test_add_func("/bdrv-graph-mod/should-update-child", 453 test_should_update_child); 454 g_test_add_func("/bdrv-graph-mod/parallel-perm-update", 455 test_parallel_perm_update); 456 g_test_add_func("/bdrv-graph-mod/parallel-exclusive-write", 457 test_parallel_exclusive_write); 458 g_test_add_func("/bdrv-graph-mod/append-greedy-filter", 459 test_append_greedy_filter); 460 461 return g_test_run(); 462 } 463