test-bdrv-graph-mod.c (15777B)
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 * | passtrough 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 * | passtrough 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 }