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 } 457