1 /* 2 * QEMU Block driver for NBD 3 * 4 * Copyright (C) 2008 Bull S.A.S. 5 * Author: Laurent Vivier <Laurent.Vivier@bull.net> 6 * 7 * Some parts: 8 * Copyright (C) 2007 Anthony Liguori <anthony@codemonkey.ws> 9 * 10 * Permission is hereby granted, free of charge, to any person obtaining a copy 11 * of this software and associated documentation files (the "Software"), to deal 12 * in the Software without restriction, including without limitation the rights 13 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 14 * copies of the Software, and to permit persons to whom the Software is 15 * furnished to do so, subject to the following conditions: 16 * 17 * The above copyright notice and this permission notice shall be included in 18 * all copies or substantial portions of the Software. 19 * 20 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 21 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 22 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 23 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 24 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 25 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN 26 * THE SOFTWARE. 27 */ 28 29 #include "qemu-common.h" 30 #include "nbd.h" 31 #include "block_int.h" 32 #include "module.h" 33 #include "qemu_socket.h" 34 35 #include <sys/types.h> 36 #include <unistd.h> 37 38 #define EN_OPTSTR ":exportname=" 39 40 /* #define DEBUG_NBD */ 41 42 #if defined(DEBUG_NBD) 43 #define logout(fmt, ...) \ 44 fprintf(stderr, "nbd\t%-24s" fmt, __func__, ##__VA_ARGS__) 45 #else 46 #define logout(fmt, ...) ((void)0) 47 #endif 48 49 #define MAX_NBD_REQUESTS 16 50 #define HANDLE_TO_INDEX(bs, handle) ((handle) ^ ((uint64_t)(intptr_t)bs)) 51 #define INDEX_TO_HANDLE(bs, index) ((index) ^ ((uint64_t)(intptr_t)bs)) 52 53 typedef struct BDRVNBDState { 54 int sock; 55 uint32_t nbdflags; 56 off_t size; 57 size_t blocksize; 58 char *export_name; /* An NBD server may export several devices */ 59 60 CoMutex send_mutex; 61 CoMutex free_sema; 62 Coroutine *send_coroutine; 63 int in_flight; 64 65 Coroutine *recv_coroutine[MAX_NBD_REQUESTS]; 66 struct nbd_reply reply; 67 68 /* If it begins with '/', this is a UNIX domain socket. Otherwise, 69 * it's a string of the form <hostname|ip4|\[ip6\]>:port 70 */ 71 char *host_spec; 72 } BDRVNBDState; 73 74 static int nbd_config(BDRVNBDState *s, const char *filename, int flags) 75 { 76 char *file; 77 char *export_name; 78 const char *host_spec; 79 const char *unixpath; 80 int err = -EINVAL; 81 82 file = g_strdup(filename); 83 84 export_name = strstr(file, EN_OPTSTR); 85 if (export_name) { 86 if (export_name[strlen(EN_OPTSTR)] == 0) { 87 goto out; 88 } 89 export_name[0] = 0; /* truncate 'file' */ 90 export_name += strlen(EN_OPTSTR); 91 s->export_name = g_strdup(export_name); 92 } 93 94 /* extract the host_spec - fail if it's not nbd:... */ 95 if (!strstart(file, "nbd:", &host_spec)) { 96 goto out; 97 } 98 99 /* are we a UNIX or TCP socket? */ 100 if (strstart(host_spec, "unix:", &unixpath)) { 101 if (unixpath[0] != '/') { /* We demand an absolute path*/ 102 goto out; 103 } 104 s->host_spec = g_strdup(unixpath); 105 } else { 106 s->host_spec = g_strdup(host_spec); 107 } 108 109 err = 0; 110 111 out: 112 g_free(file); 113 if (err != 0) { 114 g_free(s->export_name); 115 g_free(s->host_spec); 116 } 117 return err; 118 } 119 120 static void nbd_coroutine_start(BDRVNBDState *s, struct nbd_request *request) 121 { 122 int i; 123 124 /* Poor man semaphore. The free_sema is locked when no other request 125 * can be accepted, and unlocked after receiving one reply. */ 126 if (s->in_flight >= MAX_NBD_REQUESTS - 1) { 127 qemu_co_mutex_lock(&s->free_sema); 128 assert(s->in_flight < MAX_NBD_REQUESTS); 129 } 130 s->in_flight++; 131 132 for (i = 0; i < MAX_NBD_REQUESTS; i++) { 133 if (s->recv_coroutine[i] == NULL) { 134 s->recv_coroutine[i] = qemu_coroutine_self(); 135 break; 136 } 137 } 138 139 assert(i < MAX_NBD_REQUESTS); 140 request->handle = INDEX_TO_HANDLE(s, i); 141 } 142 143 static int nbd_have_request(void *opaque) 144 { 145 BDRVNBDState *s = opaque; 146 147 return s->in_flight > 0; 148 } 149 150 static void nbd_reply_ready(void *opaque) 151 { 152 BDRVNBDState *s = opaque; 153 uint64_t i; 154 int ret; 155 156 if (s->reply.handle == 0) { 157 /* No reply already in flight. Fetch a header. It is possible 158 * that another thread has done the same thing in parallel, so 159 * the socket is not readable anymore. 160 */ 161 ret = nbd_receive_reply(s->sock, &s->reply); 162 if (ret == -EAGAIN) { 163 return; 164 } 165 if (ret < 0) { 166 s->reply.handle = 0; 167 goto fail; 168 } 169 } 170 171 /* There's no need for a mutex on the receive side, because the 172 * handler acts as a synchronization point and ensures that only 173 * one coroutine is called until the reply finishes. */ 174 i = HANDLE_TO_INDEX(s, s->reply.handle); 175 if (i >= MAX_NBD_REQUESTS) { 176 goto fail; 177 } 178 179 if (s->recv_coroutine[i]) { 180 qemu_coroutine_enter(s->recv_coroutine[i], NULL); 181 return; 182 } 183 184 fail: 185 for (i = 0; i < MAX_NBD_REQUESTS; i++) { 186 if (s->recv_coroutine[i]) { 187 qemu_coroutine_enter(s->recv_coroutine[i], NULL); 188 } 189 } 190 } 191 192 static void nbd_restart_write(void *opaque) 193 { 194 BDRVNBDState *s = opaque; 195 qemu_coroutine_enter(s->send_coroutine, NULL); 196 } 197 198 static int nbd_co_send_request(BDRVNBDState *s, struct nbd_request *request, 199 QEMUIOVector *qiov, int offset) 200 { 201 int rc, ret; 202 203 qemu_co_mutex_lock(&s->send_mutex); 204 s->send_coroutine = qemu_coroutine_self(); 205 qemu_aio_set_fd_handler(s->sock, nbd_reply_ready, nbd_restart_write, 206 nbd_have_request, s); 207 rc = nbd_send_request(s->sock, request); 208 if (rc >= 0 && qiov) { 209 ret = qemu_co_sendv(s->sock, qiov->iov, qiov->niov, 210 offset, request->len); 211 if (ret != request->len) { 212 return -EIO; 213 } 214 } 215 qemu_aio_set_fd_handler(s->sock, nbd_reply_ready, NULL, 216 nbd_have_request, s); 217 s->send_coroutine = NULL; 218 qemu_co_mutex_unlock(&s->send_mutex); 219 return rc; 220 } 221 222 static void nbd_co_receive_reply(BDRVNBDState *s, struct nbd_request *request, 223 struct nbd_reply *reply, 224 QEMUIOVector *qiov, int offset) 225 { 226 int ret; 227 228 /* Wait until we're woken up by the read handler. TODO: perhaps 229 * peek at the next reply and avoid yielding if it's ours? */ 230 qemu_coroutine_yield(); 231 *reply = s->reply; 232 if (reply->handle != request->handle) { 233 reply->error = EIO; 234 } else { 235 if (qiov && reply->error == 0) { 236 ret = qemu_co_recvv(s->sock, qiov->iov, qiov->niov, 237 offset, request->len); 238 if (ret != request->len) { 239 reply->error = EIO; 240 } 241 } 242 243 /* Tell the read handler to read another header. */ 244 s->reply.handle = 0; 245 } 246 } 247 248 static void nbd_coroutine_end(BDRVNBDState *s, struct nbd_request *request) 249 { 250 int i = HANDLE_TO_INDEX(s, request->handle); 251 s->recv_coroutine[i] = NULL; 252 if (s->in_flight-- == MAX_NBD_REQUESTS) { 253 qemu_co_mutex_unlock(&s->free_sema); 254 } 255 } 256 257 static int nbd_establish_connection(BlockDriverState *bs) 258 { 259 BDRVNBDState *s = bs->opaque; 260 int sock; 261 int ret; 262 off_t size; 263 size_t blocksize; 264 265 if (s->host_spec[0] == '/') { 266 sock = unix_socket_outgoing(s->host_spec); 267 } else { 268 sock = tcp_socket_outgoing_spec(s->host_spec); 269 } 270 271 /* Failed to establish connection */ 272 if (sock < 0) { 273 logout("Failed to establish connection to NBD server\n"); 274 return -errno; 275 } 276 277 /* NBD handshake */ 278 ret = nbd_receive_negotiate(sock, s->export_name, &s->nbdflags, &size, 279 &blocksize); 280 if (ret < 0) { 281 logout("Failed to negotiate with the NBD server\n"); 282 closesocket(sock); 283 return ret; 284 } 285 286 /* Now that we're connected, set the socket to be non-blocking and 287 * kick the reply mechanism. */ 288 socket_set_nonblock(sock); 289 qemu_aio_set_fd_handler(sock, nbd_reply_ready, NULL, 290 nbd_have_request, s); 291 292 s->sock = sock; 293 s->size = size; 294 s->blocksize = blocksize; 295 296 logout("Established connection with NBD server\n"); 297 return 0; 298 } 299 300 static void nbd_teardown_connection(BlockDriverState *bs) 301 { 302 BDRVNBDState *s = bs->opaque; 303 struct nbd_request request; 304 305 request.type = NBD_CMD_DISC; 306 request.from = 0; 307 request.len = 0; 308 nbd_send_request(s->sock, &request); 309 310 qemu_aio_set_fd_handler(s->sock, NULL, NULL, NULL, NULL); 311 closesocket(s->sock); 312 } 313 314 static int nbd_open(BlockDriverState *bs, const char* filename, int flags) 315 { 316 BDRVNBDState *s = bs->opaque; 317 int result; 318 319 qemu_co_mutex_init(&s->send_mutex); 320 qemu_co_mutex_init(&s->free_sema); 321 322 /* Pop the config into our state object. Exit if invalid. */ 323 result = nbd_config(s, filename, flags); 324 if (result != 0) { 325 return result; 326 } 327 328 /* establish TCP connection, return error if it fails 329 * TODO: Configurable retry-until-timeout behaviour. 330 */ 331 result = nbd_establish_connection(bs); 332 333 return result; 334 } 335 336 static int nbd_co_readv_1(BlockDriverState *bs, int64_t sector_num, 337 int nb_sectors, QEMUIOVector *qiov, 338 int offset) 339 { 340 BDRVNBDState *s = bs->opaque; 341 struct nbd_request request; 342 struct nbd_reply reply; 343 ssize_t ret; 344 345 request.type = NBD_CMD_READ; 346 request.from = sector_num * 512; 347 request.len = nb_sectors * 512; 348 349 nbd_coroutine_start(s, &request); 350 ret = nbd_co_send_request(s, &request, NULL, 0); 351 if (ret < 0) { 352 reply.error = -ret; 353 } else { 354 nbd_co_receive_reply(s, &request, &reply, qiov, offset); 355 } 356 nbd_coroutine_end(s, &request); 357 return -reply.error; 358 359 } 360 361 static int nbd_co_writev_1(BlockDriverState *bs, int64_t sector_num, 362 int nb_sectors, QEMUIOVector *qiov, 363 int offset) 364 { 365 BDRVNBDState *s = bs->opaque; 366 struct nbd_request request; 367 struct nbd_reply reply; 368 ssize_t ret; 369 370 request.type = NBD_CMD_WRITE; 371 if (!bdrv_enable_write_cache(bs) && (s->nbdflags & NBD_FLAG_SEND_FUA)) { 372 request.type |= NBD_CMD_FLAG_FUA; 373 } 374 375 request.from = sector_num * 512; 376 request.len = nb_sectors * 512; 377 378 nbd_coroutine_start(s, &request); 379 ret = nbd_co_send_request(s, &request, qiov, offset); 380 if (ret < 0) { 381 reply.error = -ret; 382 } else { 383 nbd_co_receive_reply(s, &request, &reply, NULL, 0); 384 } 385 nbd_coroutine_end(s, &request); 386 return -reply.error; 387 } 388 389 /* qemu-nbd has a limit of slightly less than 1M per request. Try to 390 * remain aligned to 4K. */ 391 #define NBD_MAX_SECTORS 2040 392 393 static int nbd_co_readv(BlockDriverState *bs, int64_t sector_num, 394 int nb_sectors, QEMUIOVector *qiov) 395 { 396 int offset = 0; 397 int ret; 398 while (nb_sectors > NBD_MAX_SECTORS) { 399 ret = nbd_co_readv_1(bs, sector_num, NBD_MAX_SECTORS, qiov, offset); 400 if (ret < 0) { 401 return ret; 402 } 403 offset += NBD_MAX_SECTORS * 512; 404 sector_num += NBD_MAX_SECTORS; 405 nb_sectors -= NBD_MAX_SECTORS; 406 } 407 return nbd_co_readv_1(bs, sector_num, nb_sectors, qiov, offset); 408 } 409 410 static int nbd_co_writev(BlockDriverState *bs, int64_t sector_num, 411 int nb_sectors, QEMUIOVector *qiov) 412 { 413 int offset = 0; 414 int ret; 415 while (nb_sectors > NBD_MAX_SECTORS) { 416 ret = nbd_co_writev_1(bs, sector_num, NBD_MAX_SECTORS, qiov, offset); 417 if (ret < 0) { 418 return ret; 419 } 420 offset += NBD_MAX_SECTORS * 512; 421 sector_num += NBD_MAX_SECTORS; 422 nb_sectors -= NBD_MAX_SECTORS; 423 } 424 return nbd_co_writev_1(bs, sector_num, nb_sectors, qiov, offset); 425 } 426 427 static int nbd_co_flush(BlockDriverState *bs) 428 { 429 BDRVNBDState *s = bs->opaque; 430 struct nbd_request request; 431 struct nbd_reply reply; 432 ssize_t ret; 433 434 if (!(s->nbdflags & NBD_FLAG_SEND_FLUSH)) { 435 return 0; 436 } 437 438 request.type = NBD_CMD_FLUSH; 439 if (s->nbdflags & NBD_FLAG_SEND_FUA) { 440 request.type |= NBD_CMD_FLAG_FUA; 441 } 442 443 request.from = 0; 444 request.len = 0; 445 446 nbd_coroutine_start(s, &request); 447 ret = nbd_co_send_request(s, &request, NULL, 0); 448 if (ret < 0) { 449 reply.error = -ret; 450 } else { 451 nbd_co_receive_reply(s, &request, &reply, NULL, 0); 452 } 453 nbd_coroutine_end(s, &request); 454 return -reply.error; 455 } 456 457 static int nbd_co_discard(BlockDriverState *bs, int64_t sector_num, 458 int nb_sectors) 459 { 460 BDRVNBDState *s = bs->opaque; 461 struct nbd_request request; 462 struct nbd_reply reply; 463 ssize_t ret; 464 465 if (!(s->nbdflags & NBD_FLAG_SEND_TRIM)) { 466 return 0; 467 } 468 request.type = NBD_CMD_TRIM; 469 request.from = sector_num * 512;; 470 request.len = nb_sectors * 512; 471 472 nbd_coroutine_start(s, &request); 473 ret = nbd_co_send_request(s, &request, NULL, 0); 474 if (ret < 0) { 475 reply.error = -ret; 476 } else { 477 nbd_co_receive_reply(s, &request, &reply, NULL, 0); 478 } 479 nbd_coroutine_end(s, &request); 480 return -reply.error; 481 } 482 483 static void nbd_close(BlockDriverState *bs) 484 { 485 BDRVNBDState *s = bs->opaque; 486 g_free(s->export_name); 487 g_free(s->host_spec); 488 489 nbd_teardown_connection(bs); 490 } 491 492 static int64_t nbd_getlength(BlockDriverState *bs) 493 { 494 BDRVNBDState *s = bs->opaque; 495 496 return s->size; 497 } 498 499 static BlockDriver bdrv_nbd = { 500 .format_name = "nbd", 501 .instance_size = sizeof(BDRVNBDState), 502 .bdrv_file_open = nbd_open, 503 .bdrv_co_readv = nbd_co_readv, 504 .bdrv_co_writev = nbd_co_writev, 505 .bdrv_close = nbd_close, 506 .bdrv_co_flush_to_os = nbd_co_flush, 507 .bdrv_co_discard = nbd_co_discard, 508 .bdrv_getlength = nbd_getlength, 509 .protocol_name = "nbd", 510 }; 511 512 static void bdrv_nbd_init(void) 513 { 514 bdrv_register(&bdrv_nbd); 515 } 516 517 block_init(bdrv_nbd_init); 518