| 1 | /* |
| 2 | * L2/refcount table cache for the QCOW2 format |
| 3 | * |
| 4 | * Copyright (c) 2010 Kevin Wolf <kwolf@redhat.com> |
| 5 | * |
| 6 | * Permission is hereby granted, free of charge, to any person obtaining a copy |
| 7 | * of this software and associated documentation files (the "Software"), to deal |
| 8 | * in the Software without restriction, including without limitation the rights |
| 9 | * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell |
| 10 | * copies of the Software, and to permit persons to whom the Software is |
| 11 | * furnished to do so, subject to the following conditions: |
| 12 | * |
| 13 | * The above copyright notice and this permission notice shall be included in |
| 14 | * all copies or substantial portions of the Software. |
| 15 | * |
| 16 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| 17 | * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| 18 | * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL |
| 19 | * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| 20 | * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
| 21 | * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN |
| 22 | * THE SOFTWARE. |
| 23 | */ |
| 24 | |
| 25 | #include "qemu/osdep.h" |
| 26 | #include "block/block-io.h" |
| 27 | #include "qemu/memalign.h" |
| 28 | #include "qcow2.h" |
| 29 | #include "trace.h" |
| 30 | |
| 31 | typedef struct Qcow2CachedTable { |
| 32 | int64_t offset; |
| 33 | uint64_t lru_counter; |
| 34 | int ref; |
| 35 | bool dirty; |
| 36 | } Qcow2CachedTable; |
| 37 | |
| 38 | struct Qcow2Cache { |
| 39 | Qcow2CachedTable *entries; |
| 40 | struct Qcow2Cache *depends; |
| 41 | int size; |
| 42 | int table_size; |
| 43 | bool depends_on_flush; |
| 44 | void *table_array; |
| 45 | uint64_t lru_counter; |
| 46 | uint64_t cache_clean_lru_counter; |
| 47 | }; |
| 48 | |
| 49 | static inline void *qcow2_cache_get_table_addr(Qcow2Cache *c, int table) |
| 50 | { |
| 51 | return (uint8_t *) c->table_array + (size_t) table * c->table_size; |
| 52 | } |
| 53 | |
| 54 | static inline int qcow2_cache_get_table_idx(Qcow2Cache *c, void *table) |
| 55 | { |
| 56 | ptrdiff_t table_offset = (uint8_t *) table - (uint8_t *) c->table_array; |
| 57 | int idx = table_offset / c->table_size; |
| 58 | assert(idx >= 0 && idx < c->size && table_offset % c->table_size == 0); |
| 59 | return idx; |
| 60 | } |
| 61 | |
| 62 | static inline const char *qcow2_cache_get_name(BDRVQcow2State *s, Qcow2Cache *c) |
| 63 | { |
| 64 | if (c == s->refcount_block_cache) { |
| 65 | return "refcount block"; |
| 66 | } else if (c == s->l2_table_cache) { |
| 67 | return "L2 table"; |
| 68 | } else { |
| 69 | /* Do not abort, because this is not critical */ |
| 70 | return "unknown"; |
| 71 | } |
| 72 | } |
| 73 | |
| 74 | static void qcow2_cache_table_release(Qcow2Cache *c, int i, int num_tables) |
| 75 | { |
| 76 | /* Using MADV_DONTNEED to discard memory is a Linux-specific feature */ |
| 77 | #ifdef CONFIG_LINUX |
| 78 | void *t = qcow2_cache_get_table_addr(c, i); |
| 79 | int align = qemu_real_host_page_size(); |
| 80 | size_t mem_size = (size_t) c->table_size * num_tables; |
| 81 | size_t offset = QEMU_ALIGN_UP((uintptr_t) t, align) - (uintptr_t) t; |
| 82 | size_t length = QEMU_ALIGN_DOWN(mem_size - offset, align); |
| 83 | if (mem_size > offset && length > 0) { |
| 84 | madvise((uint8_t *) t + offset, length, MADV_DONTNEED); |
| 85 | } |
| 86 | #endif |
| 87 | } |
| 88 | |
| 89 | static inline bool can_clean_entry(Qcow2Cache *c, int i) |
| 90 | { |
| 91 | Qcow2CachedTable *t = &c->entries[i]; |
| 92 | return t->ref == 0 && !t->dirty && t->offset != 0 && |
| 93 | t->lru_counter <= c->cache_clean_lru_counter; |
| 94 | } |
| 95 | |
| 96 | void qcow2_cache_clean_unused(Qcow2Cache *c) |
| 97 | { |
| 98 | int i = 0; |
| 99 | while (i < c->size) { |
| 100 | int to_clean = 0; |
| 101 | |
| 102 | /* Skip the entries that we don't need to clean */ |
| 103 | while (i < c->size && !can_clean_entry(c, i)) { |
| 104 | i++; |
| 105 | } |
| 106 | |
| 107 | /* And count how many we can clean in a row */ |
| 108 | while (i < c->size && can_clean_entry(c, i)) { |
| 109 | c->entries[i].offset = 0; |
| 110 | c->entries[i].lru_counter = 0; |
| 111 | i++; |
| 112 | to_clean++; |
| 113 | } |
| 114 | |
| 115 | if (to_clean > 0) { |
| 116 | qcow2_cache_table_release(c, i - to_clean, to_clean); |
| 117 | } |
| 118 | } |
| 119 | |
| 120 | c->cache_clean_lru_counter = c->lru_counter; |
| 121 | } |
| 122 | |
| 123 | Qcow2Cache *qcow2_cache_create(BlockDriverState *bs, int num_tables, |
| 124 | unsigned table_size) |
| 125 | { |
| 126 | BDRVQcow2State *s = bs->opaque; |
| 127 | Qcow2Cache *c; |
| 128 | |
| 129 | assert(num_tables > 0); |
| 130 | assert(is_power_of_2(table_size)); |
| 131 | assert(table_size >= (1 << MIN_CLUSTER_BITS)); |
| 132 | assert(table_size <= s->cluster_size); |
| 133 | |
| 134 | c = g_new0(Qcow2Cache, 1); |
| 135 | c->size = num_tables; |
| 136 | c->table_size = table_size; |
| 137 | c->entries = g_try_new0(Qcow2CachedTable, num_tables); |
| 138 | c->table_array = qemu_try_blockalign(bs->file->bs, |
| 139 | (size_t) num_tables * c->table_size); |
| 140 | |
| 141 | if (!c->entries || !c->table_array) { |
| 142 | qemu_vfree(c->table_array); |
| 143 | g_free(c->entries); |
| 144 | g_free(c); |
| 145 | c = NULL; |
| 146 | } |
| 147 | |
| 148 | return c; |
| 149 | } |
| 150 | |
| 151 | int qcow2_cache_destroy(Qcow2Cache *c) |
| 152 | { |
| 153 | int i; |
| 154 | |
| 155 | for (i = 0; i < c->size; i++) { |
| 156 | assert(c->entries[i].ref == 0); |
| 157 | } |
| 158 | |
| 159 | qemu_vfree(c->table_array); |
| 160 | g_free(c->entries); |
| 161 | g_free(c); |
| 162 | |
| 163 | return 0; |
| 164 | } |
| 165 | |
| 166 | static int GRAPH_RDLOCK |
| 167 | qcow2_cache_flush_dependency(BlockDriverState *bs, Qcow2Cache *c) |
| 168 | { |
| 169 | int ret; |
| 170 | |
| 171 | ret = qcow2_cache_flush(bs, c->depends); |
| 172 | if (ret < 0) { |
| 173 | return ret; |
| 174 | } |
| 175 | |
| 176 | c->depends = NULL; |
| 177 | c->depends_on_flush = false; |
| 178 | |
| 179 | return 0; |
| 180 | } |
| 181 | |
| 182 | static int GRAPH_RDLOCK |
| 183 | qcow2_cache_entry_flush(BlockDriverState *bs, Qcow2Cache *c, int i) |
| 184 | { |
| 185 | BDRVQcow2State *s = bs->opaque; |
| 186 | int ret = 0; |
| 187 | |
| 188 | if (!c->entries[i].dirty || !c->entries[i].offset) { |
| 189 | return 0; |
| 190 | } |
| 191 | |
| 192 | trace_qcow2_cache_entry_flush(qemu_coroutine_self(), |
| 193 | c == s->l2_table_cache, i); |
| 194 | |
| 195 | if (c->depends) { |
| 196 | ret = qcow2_cache_flush_dependency(bs, c); |
| 197 | } else if (c->depends_on_flush) { |
| 198 | ret = bdrv_flush(bs->file->bs); |
| 199 | if (ret >= 0) { |
| 200 | c->depends_on_flush = false; |
| 201 | } |
| 202 | } |
| 203 | |
| 204 | if (ret < 0) { |
| 205 | return ret; |
| 206 | } |
| 207 | |
| 208 | if (c == s->refcount_block_cache) { |
| 209 | ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_REFCOUNT_BLOCK, |
| 210 | c->entries[i].offset, c->table_size, false); |
| 211 | } else if (c == s->l2_table_cache) { |
| 212 | ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_ACTIVE_L2, |
| 213 | c->entries[i].offset, c->table_size, false); |
| 214 | } else { |
| 215 | ret = qcow2_pre_write_overlap_check(bs, 0, |
| 216 | c->entries[i].offset, c->table_size, false); |
| 217 | } |
| 218 | |
| 219 | if (ret < 0) { |
| 220 | return ret; |
| 221 | } |
| 222 | |
| 223 | if (c == s->refcount_block_cache) { |
| 224 | BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_UPDATE_PART); |
| 225 | } else if (c == s->l2_table_cache) { |
| 226 | BLKDBG_EVENT(bs->file, BLKDBG_L2_UPDATE); |
| 227 | } |
| 228 | |
| 229 | ret = bdrv_pwrite(bs->file, c->entries[i].offset, c->table_size, |
| 230 | qcow2_cache_get_table_addr(c, i), 0); |
| 231 | if (ret < 0) { |
| 232 | return ret; |
| 233 | } |
| 234 | |
| 235 | c->entries[i].dirty = false; |
| 236 | |
| 237 | return 0; |
| 238 | } |
| 239 | |
| 240 | int qcow2_cache_write(BlockDriverState *bs, Qcow2Cache *c) |
| 241 | { |
| 242 | BDRVQcow2State *s = bs->opaque; |
| 243 | int result = 0; |
| 244 | int ret; |
| 245 | int i; |
| 246 | |
| 247 | trace_qcow2_cache_flush(qemu_coroutine_self(), c == s->l2_table_cache); |
| 248 | |
| 249 | for (i = 0; i < c->size; i++) { |
| 250 | ret = qcow2_cache_entry_flush(bs, c, i); |
| 251 | if (ret < 0 && result != -ENOSPC) { |
| 252 | result = ret; |
| 253 | } |
| 254 | } |
| 255 | |
| 256 | return result; |
| 257 | } |
| 258 | |
| 259 | int qcow2_cache_flush(BlockDriverState *bs, Qcow2Cache *c) |
| 260 | { |
| 261 | int result = qcow2_cache_write(bs, c); |
| 262 | |
| 263 | if (result == 0) { |
| 264 | int ret = bdrv_flush(bs->file->bs); |
| 265 | if (ret < 0) { |
| 266 | result = ret; |
| 267 | } |
| 268 | } |
| 269 | |
| 270 | return result; |
| 271 | } |
| 272 | |
| 273 | int qcow2_cache_set_dependency(BlockDriverState *bs, Qcow2Cache *c, |
| 274 | Qcow2Cache *dependency) |
| 275 | { |
| 276 | int ret; |
| 277 | |
| 278 | if (dependency->depends) { |
| 279 | ret = qcow2_cache_flush_dependency(bs, dependency); |
| 280 | if (ret < 0) { |
| 281 | return ret; |
| 282 | } |
| 283 | } |
| 284 | |
| 285 | if (c->depends && (c->depends != dependency)) { |
| 286 | ret = qcow2_cache_flush_dependency(bs, c); |
| 287 | if (ret < 0) { |
| 288 | return ret; |
| 289 | } |
| 290 | } |
| 291 | |
| 292 | c->depends = dependency; |
| 293 | return 0; |
| 294 | } |
| 295 | |
| 296 | void qcow2_cache_depends_on_flush(Qcow2Cache *c) |
| 297 | { |
| 298 | c->depends_on_flush = true; |
| 299 | } |
| 300 | |
| 301 | int qcow2_cache_empty(BlockDriverState *bs, Qcow2Cache *c) |
| 302 | { |
| 303 | int ret, i; |
| 304 | |
| 305 | ret = qcow2_cache_flush(bs, c); |
| 306 | if (ret < 0) { |
| 307 | return ret; |
| 308 | } |
| 309 | |
| 310 | for (i = 0; i < c->size; i++) { |
| 311 | assert(c->entries[i].ref == 0); |
| 312 | c->entries[i].offset = 0; |
| 313 | c->entries[i].lru_counter = 0; |
| 314 | } |
| 315 | |
| 316 | qcow2_cache_table_release(c, 0, c->size); |
| 317 | |
| 318 | c->lru_counter = 0; |
| 319 | |
| 320 | return 0; |
| 321 | } |
| 322 | |
| 323 | static int GRAPH_RDLOCK |
| 324 | qcow2_cache_do_get(BlockDriverState *bs, Qcow2Cache *c, uint64_t offset, |
| 325 | void **table, bool read_from_disk) |
| 326 | { |
| 327 | BDRVQcow2State *s = bs->opaque; |
| 328 | int i; |
| 329 | int ret; |
| 330 | int lookup_index; |
| 331 | uint64_t min_lru_counter = UINT64_MAX; |
| 332 | int min_lru_index = -1; |
| 333 | |
| 334 | assert(offset != 0); |
| 335 | |
| 336 | trace_qcow2_cache_get(qemu_coroutine_self(), c == s->l2_table_cache, |
| 337 | offset, read_from_disk); |
| 338 | |
| 339 | if (!QEMU_IS_ALIGNED(offset, c->table_size)) { |
| 340 | qcow2_signal_corruption(bs, true, -1, -1, "Cannot get entry from %s " |
| 341 | "cache: Offset %#" PRIx64 " is unaligned", |
| 342 | qcow2_cache_get_name(s, c), offset); |
| 343 | return -EIO; |
| 344 | } |
| 345 | |
| 346 | /* Check if the table is already cached */ |
| 347 | i = lookup_index = (offset / c->table_size * 4) % c->size; |
| 348 | do { |
| 349 | const Qcow2CachedTable *t = &c->entries[i]; |
| 350 | if (t->offset == offset) { |
| 351 | goto found; |
| 352 | } |
| 353 | if (t->ref == 0 && t->lru_counter < min_lru_counter) { |
| 354 | min_lru_counter = t->lru_counter; |
| 355 | min_lru_index = i; |
| 356 | } |
| 357 | if (++i == c->size) { |
| 358 | i = 0; |
| 359 | } |
| 360 | } while (i != lookup_index); |
| 361 | |
| 362 | if (min_lru_index == -1) { |
| 363 | /* This can't happen in current synchronous code, but leave the check |
| 364 | * here as a reminder for whoever starts using AIO with the cache */ |
| 365 | abort(); |
| 366 | } |
| 367 | |
| 368 | /* Cache miss: write a table back and replace it */ |
| 369 | i = min_lru_index; |
| 370 | trace_qcow2_cache_get_replace_entry(qemu_coroutine_self(), |
| 371 | c == s->l2_table_cache, i); |
| 372 | |
| 373 | ret = qcow2_cache_entry_flush(bs, c, i); |
| 374 | if (ret < 0) { |
| 375 | return ret; |
| 376 | } |
| 377 | |
| 378 | trace_qcow2_cache_get_read(qemu_coroutine_self(), |
| 379 | c == s->l2_table_cache, i); |
| 380 | c->entries[i].offset = 0; |
| 381 | if (read_from_disk) { |
| 382 | if (c == s->l2_table_cache) { |
| 383 | BLKDBG_EVENT(bs->file, BLKDBG_L2_LOAD); |
| 384 | } |
| 385 | |
| 386 | ret = bdrv_pread(bs->file, offset, c->table_size, |
| 387 | qcow2_cache_get_table_addr(c, i), 0); |
| 388 | if (ret < 0) { |
| 389 | return ret; |
| 390 | } |
| 391 | } |
| 392 | |
| 393 | c->entries[i].offset = offset; |
| 394 | |
| 395 | /* And return the right table */ |
| 396 | found: |
| 397 | c->entries[i].ref++; |
| 398 | *table = qcow2_cache_get_table_addr(c, i); |
| 399 | |
| 400 | trace_qcow2_cache_get_done(qemu_coroutine_self(), |
| 401 | c == s->l2_table_cache, i); |
| 402 | |
| 403 | return 0; |
| 404 | } |
| 405 | |
| 406 | int qcow2_cache_get(BlockDriverState *bs, Qcow2Cache *c, uint64_t offset, |
| 407 | void **table) |
| 408 | { |
| 409 | return qcow2_cache_do_get(bs, c, offset, table, true); |
| 410 | } |
| 411 | |
| 412 | int qcow2_cache_get_empty(BlockDriverState *bs, Qcow2Cache *c, uint64_t offset, |
| 413 | void **table) |
| 414 | { |
| 415 | return qcow2_cache_do_get(bs, c, offset, table, false); |
| 416 | } |
| 417 | |
| 418 | void qcow2_cache_put(Qcow2Cache *c, void **table) |
| 419 | { |
| 420 | int i = qcow2_cache_get_table_idx(c, *table); |
| 421 | |
| 422 | c->entries[i].ref--; |
| 423 | *table = NULL; |
| 424 | |
| 425 | if (c->entries[i].ref == 0) { |
| 426 | c->entries[i].lru_counter = ++c->lru_counter; |
| 427 | } |
| 428 | |
| 429 | assert(c->entries[i].ref >= 0); |
| 430 | } |
| 431 | |
| 432 | void qcow2_cache_entry_mark_dirty(Qcow2Cache *c, void *table) |
| 433 | { |
| 434 | int i = qcow2_cache_get_table_idx(c, table); |
| 435 | assert(c->entries[i].offset != 0); |
| 436 | c->entries[i].dirty = true; |
| 437 | } |
| 438 | |
| 439 | void *qcow2_cache_is_table_offset(Qcow2Cache *c, uint64_t offset) |
| 440 | { |
| 441 | int i; |
| 442 | |
| 443 | for (i = 0; i < c->size; i++) { |
| 444 | if (c->entries[i].offset == offset) { |
| 445 | return qcow2_cache_get_table_addr(c, i); |
| 446 | } |
| 447 | } |
| 448 | return NULL; |
| 449 | } |
| 450 | |
| 451 | void qcow2_cache_discard(Qcow2Cache *c, void *table) |
| 452 | { |
| 453 | int i = qcow2_cache_get_table_idx(c, table); |
| 454 | |
| 455 | assert(c->entries[i].ref == 0); |
| 456 | |
| 457 | c->entries[i].offset = 0; |
| 458 | c->entries[i].lru_counter = 0; |
| 459 | c->entries[i].dirty = false; |
| 460 | |
| 461 | qcow2_cache_table_release(c, i, 1); |
| 462 | } |