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 struct iovec *iov, 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 && iov) { 209 ret = qemu_co_sendv(s->sock, iov, request->len, offset); 210 if (ret != request->len) { 211 return -EIO; 212 } 213 } 214 qemu_aio_set_fd_handler(s->sock, nbd_reply_ready, NULL, 215 nbd_have_request, s); 216 s->send_coroutine = NULL; 217 qemu_co_mutex_unlock(&s->send_mutex); 218 return rc; 219 } 220 221 static void nbd_co_receive_reply(BDRVNBDState *s, struct nbd_request *request, 222 struct nbd_reply *reply, 223 struct iovec *iov, int offset) 224 { 225 int ret; 226 227 /* Wait until we're woken up by the read handler. TODO: perhaps 228 * peek at the next reply and avoid yielding if it's ours? */ 229 qemu_coroutine_yield(); 230 *reply = s->reply; 231 if (reply->handle != request->handle) { 232 reply->error = EIO; 233 } else { 234 if (iov && reply->error == 0) { 235 ret = qemu_co_recvv(s->sock, iov, request->len, offset); 236 if (ret != request->len) { 237 reply->error = EIO; 238 } 239 } 240 241 /* Tell the read handler to read another header. */ 242 s->reply.handle = 0; 243 } 244 } 245 246 static void nbd_coroutine_end(BDRVNBDState *s, struct nbd_request *request) 247 { 248 int i = HANDLE_TO_INDEX(s, request->handle); 249 s->recv_coroutine[i] = NULL; 250 if (s->in_flight-- == MAX_NBD_REQUESTS) { 251 qemu_co_mutex_unlock(&s->free_sema); 252 } 253 } 254 255 static int nbd_establish_connection(BlockDriverState *bs) 256 { 257 BDRVNBDState *s = bs->opaque; 258 int sock; 259 int ret; 260 off_t size; 261 size_t blocksize; 262 263 if (s->host_spec[0] == '/') { 264 sock = unix_socket_outgoing(s->host_spec); 265 } else { 266 sock = tcp_socket_outgoing_spec(s->host_spec); 267 } 268 269 /* Failed to establish connection */ 270 if (sock < 0) { 271 logout("Failed to establish connection to NBD server\n"); 272 return -errno; 273 } 274 275 /* NBD handshake */ 276 ret = nbd_receive_negotiate(sock, s->export_name, &s->nbdflags, &size, 277 &blocksize); 278 if (ret < 0) { 279 logout("Failed to negotiate with the NBD server\n"); 280 closesocket(sock); 281 return ret; 282 } 283 284 /* Now that we're connected, set the socket to be non-blocking and 285 * kick the reply mechanism. */ 286 socket_set_nonblock(sock); 287 qemu_aio_set_fd_handler(sock, nbd_reply_ready, NULL, 288 nbd_have_request, s); 289 290 s->sock = sock; 291 s->size = size; 292 s->blocksize = blocksize; 293 294 logout("Established connection with NBD server\n"); 295 return 0; 296 } 297 298 static void nbd_teardown_connection(BlockDriverState *bs) 299 { 300 BDRVNBDState *s = bs->opaque; 301 struct nbd_request request; 302 303 request.type = NBD_CMD_DISC; 304 request.from = 0; 305 request.len = 0; 306 nbd_send_request(s->sock, &request); 307 308 qemu_aio_set_fd_handler(s->sock, NULL, NULL, NULL, NULL); 309 closesocket(s->sock); 310 } 311 312 static int nbd_open(BlockDriverState *bs, const char* filename, int flags) 313 { 314 BDRVNBDState *s = bs->opaque; 315 int result; 316 317 qemu_co_mutex_init(&s->send_mutex); 318 qemu_co_mutex_init(&s->free_sema); 319 320 /* Pop the config into our state object. Exit if invalid. */ 321 result = nbd_config(s, filename, flags); 322 if (result != 0) { 323 return result; 324 } 325 326 /* establish TCP connection, return error if it fails 327 * TODO: Configurable retry-until-timeout behaviour. 328 */ 329 result = nbd_establish_connection(bs); 330 331 return result; 332 } 333 334 static int nbd_co_readv_1(BlockDriverState *bs, int64_t sector_num, 335 int nb_sectors, QEMUIOVector *qiov, 336 int offset) 337 { 338 BDRVNBDState *s = bs->opaque; 339 struct nbd_request request; 340 struct nbd_reply reply; 341 ssize_t ret; 342 343 request.type = NBD_CMD_READ; 344 request.from = sector_num * 512; 345 request.len = nb_sectors * 512; 346 347 nbd_coroutine_start(s, &request); 348 ret = nbd_co_send_request(s, &request, NULL, 0); 349 if (ret < 0) { 350 reply.error = -ret; 351 } else { 352 nbd_co_receive_reply(s, &request, &reply, qiov->iov, offset); 353 } 354 nbd_coroutine_end(s, &request); 355 return -reply.error; 356 357 } 358 359 static int nbd_co_writev_1(BlockDriverState *bs, int64_t sector_num, 360 int nb_sectors, QEMUIOVector *qiov, 361 int offset) 362 { 363 BDRVNBDState *s = bs->opaque; 364 struct nbd_request request; 365 struct nbd_reply reply; 366 ssize_t ret; 367 368 request.type = NBD_CMD_WRITE; 369 if (!bdrv_enable_write_cache(bs) && (s->nbdflags & NBD_FLAG_SEND_FUA)) { 370 request.type |= NBD_CMD_FLAG_FUA; 371 } 372 373 request.from = sector_num * 512; 374 request.len = nb_sectors * 512; 375 376 nbd_coroutine_start(s, &request); 377 ret = nbd_co_send_request(s, &request, qiov->iov, offset); 378 if (ret < 0) { 379 reply.error = -ret; 380 } else { 381 nbd_co_receive_reply(s, &request, &reply, NULL, 0); 382 } 383 nbd_coroutine_end(s, &request); 384 return -reply.error; 385 } 386 387 /* qemu-nbd has a limit of slightly less than 1M per request. Try to 388 * remain aligned to 4K. */ 389 #define NBD_MAX_SECTORS 2040 390 391 static int nbd_co_readv(BlockDriverState *bs, int64_t sector_num, 392 int nb_sectors, QEMUIOVector *qiov) 393 { 394 int offset = 0; 395 int ret; 396 while (nb_sectors > NBD_MAX_SECTORS) { 397 ret = nbd_co_readv_1(bs, sector_num, NBD_MAX_SECTORS, qiov, offset); 398 if (ret < 0) { 399 return ret; 400 } 401 offset += NBD_MAX_SECTORS * 512; 402 sector_num += NBD_MAX_SECTORS; 403 nb_sectors -= NBD_MAX_SECTORS; 404 } 405 return nbd_co_readv_1(bs, sector_num, nb_sectors, qiov, offset); 406 } 407 408 static int nbd_co_writev(BlockDriverState *bs, int64_t sector_num, 409 int nb_sectors, QEMUIOVector *qiov) 410 { 411 int offset = 0; 412 int ret; 413 while (nb_sectors > NBD_MAX_SECTORS) { 414 ret = nbd_co_writev_1(bs, sector_num, NBD_MAX_SECTORS, qiov, offset); 415 if (ret < 0) { 416 return ret; 417 } 418 offset += NBD_MAX_SECTORS * 512; 419 sector_num += NBD_MAX_SECTORS; 420 nb_sectors -= NBD_MAX_SECTORS; 421 } 422 return nbd_co_writev_1(bs, sector_num, nb_sectors, qiov, offset); 423 } 424 425 static int nbd_co_flush(BlockDriverState *bs) 426 { 427 BDRVNBDState *s = bs->opaque; 428 struct nbd_request request; 429 struct nbd_reply reply; 430 ssize_t ret; 431 432 if (!(s->nbdflags & NBD_FLAG_SEND_FLUSH)) { 433 return 0; 434 } 435 436 request.type = NBD_CMD_FLUSH; 437 if (s->nbdflags & NBD_FLAG_SEND_FUA) { 438 request.type |= NBD_CMD_FLAG_FUA; 439 } 440 441 request.from = 0; 442 request.len = 0; 443 444 nbd_coroutine_start(s, &request); 445 ret = nbd_co_send_request(s, &request, NULL, 0); 446 if (ret < 0) { 447 reply.error = -ret; 448 } else { 449 nbd_co_receive_reply(s, &request, &reply, NULL, 0); 450 } 451 nbd_coroutine_end(s, &request); 452 return -reply.error; 453 } 454 455 static int nbd_co_discard(BlockDriverState *bs, int64_t sector_num, 456 int nb_sectors) 457 { 458 BDRVNBDState *s = bs->opaque; 459 struct nbd_request request; 460 struct nbd_reply reply; 461 ssize_t ret; 462 463 if (!(s->nbdflags & NBD_FLAG_SEND_TRIM)) { 464 return 0; 465 } 466 request.type = NBD_CMD_TRIM; 467 request.from = sector_num * 512;; 468 request.len = nb_sectors * 512; 469 470 nbd_coroutine_start(s, &request); 471 ret = nbd_co_send_request(s, &request, NULL, 0); 472 if (ret < 0) { 473 reply.error = -ret; 474 } else { 475 nbd_co_receive_reply(s, &request, &reply, NULL, 0); 476 } 477 nbd_coroutine_end(s, &request); 478 return -reply.error; 479 } 480 481 static void nbd_close(BlockDriverState *bs) 482 { 483 BDRVNBDState *s = bs->opaque; 484 g_free(s->export_name); 485 g_free(s->host_spec); 486 487 nbd_teardown_connection(bs); 488 } 489 490 static int64_t nbd_getlength(BlockDriverState *bs) 491 { 492 BDRVNBDState *s = bs->opaque; 493 494 return s->size; 495 } 496 497 static BlockDriver bdrv_nbd = { 498 .format_name = "nbd", 499 .instance_size = sizeof(BDRVNBDState), 500 .bdrv_file_open = nbd_open, 501 .bdrv_co_readv = nbd_co_readv, 502 .bdrv_co_writev = nbd_co_writev, 503 .bdrv_close = nbd_close, 504 .bdrv_co_flush_to_os = nbd_co_flush, 505 .bdrv_co_discard = nbd_co_discard, 506 .bdrv_getlength = nbd_getlength, 507 .protocol_name = "nbd", 508 }; 509 510 static void bdrv_nbd_init(void) 511 { 512 bdrv_register(&bdrv_nbd); 513 } 514 515 block_init(bdrv_nbd_init); 516