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 int i; 154 155 if (s->reply.handle == 0) { 156 /* No reply already in flight. Fetch a header. */ 157 if (nbd_receive_reply(s->sock, &s->reply) < 0) { 158 s->reply.handle = 0; 159 goto fail; 160 } 161 } 162 163 /* There's no need for a mutex on the receive side, because the 164 * handler acts as a synchronization point and ensures that only 165 * one coroutine is called until the reply finishes. */ 166 i = HANDLE_TO_INDEX(s, s->reply.handle); 167 if (s->recv_coroutine[i]) { 168 qemu_coroutine_enter(s->recv_coroutine[i], NULL); 169 return; 170 } 171 172 fail: 173 for (i = 0; i < MAX_NBD_REQUESTS; i++) { 174 if (s->recv_coroutine[i]) { 175 qemu_coroutine_enter(s->recv_coroutine[i], NULL); 176 } 177 } 178 } 179 180 static void nbd_restart_write(void *opaque) 181 { 182 BDRVNBDState *s = opaque; 183 qemu_coroutine_enter(s->send_coroutine, NULL); 184 } 185 186 static int nbd_co_send_request(BDRVNBDState *s, struct nbd_request *request, 187 struct iovec *iov, int offset) 188 { 189 int rc, ret; 190 191 qemu_co_mutex_lock(&s->send_mutex); 192 s->send_coroutine = qemu_coroutine_self(); 193 qemu_aio_set_fd_handler(s->sock, nbd_reply_ready, nbd_restart_write, 194 nbd_have_request, NULL, s); 195 rc = nbd_send_request(s->sock, request); 196 if (rc != -1 && iov) { 197 ret = qemu_co_sendv(s->sock, iov, request->len, offset); 198 if (ret != request->len) { 199 errno = -EIO; 200 rc = -1; 201 } 202 } 203 qemu_aio_set_fd_handler(s->sock, nbd_reply_ready, NULL, 204 nbd_have_request, NULL, s); 205 s->send_coroutine = NULL; 206 qemu_co_mutex_unlock(&s->send_mutex); 207 return rc; 208 } 209 210 static void nbd_co_receive_reply(BDRVNBDState *s, struct nbd_request *request, 211 struct nbd_reply *reply, 212 struct iovec *iov, int offset) 213 { 214 int ret; 215 216 /* Wait until we're woken up by the read handler. TODO: perhaps 217 * peek at the next reply and avoid yielding if it's ours? */ 218 qemu_coroutine_yield(); 219 *reply = s->reply; 220 if (reply->handle != request->handle) { 221 reply->error = EIO; 222 } else { 223 if (iov && reply->error == 0) { 224 ret = qemu_co_recvv(s->sock, iov, request->len, offset); 225 if (ret != request->len) { 226 reply->error = EIO; 227 } 228 } 229 230 /* Tell the read handler to read another header. */ 231 s->reply.handle = 0; 232 } 233 } 234 235 static void nbd_coroutine_end(BDRVNBDState *s, struct nbd_request *request) 236 { 237 int i = HANDLE_TO_INDEX(s, request->handle); 238 s->recv_coroutine[i] = NULL; 239 if (s->in_flight-- == MAX_NBD_REQUESTS) { 240 qemu_co_mutex_unlock(&s->free_sema); 241 } 242 } 243 244 static int nbd_establish_connection(BlockDriverState *bs) 245 { 246 BDRVNBDState *s = bs->opaque; 247 int sock; 248 int ret; 249 off_t size; 250 size_t blocksize; 251 252 if (s->host_spec[0] == '/') { 253 sock = unix_socket_outgoing(s->host_spec); 254 } else { 255 sock = tcp_socket_outgoing_spec(s->host_spec); 256 } 257 258 /* Failed to establish connection */ 259 if (sock == -1) { 260 logout("Failed to establish connection to NBD server\n"); 261 return -errno; 262 } 263 264 /* NBD handshake */ 265 ret = nbd_receive_negotiate(sock, s->export_name, &s->nbdflags, &size, 266 &blocksize); 267 if (ret == -1) { 268 logout("Failed to negotiate with the NBD server\n"); 269 closesocket(sock); 270 return -errno; 271 } 272 273 /* Now that we're connected, set the socket to be non-blocking and 274 * kick the reply mechanism. */ 275 socket_set_nonblock(sock); 276 qemu_aio_set_fd_handler(s->sock, nbd_reply_ready, NULL, 277 nbd_have_request, NULL, s); 278 279 s->sock = sock; 280 s->size = size; 281 s->blocksize = blocksize; 282 283 logout("Established connection with NBD server\n"); 284 return 0; 285 } 286 287 static void nbd_teardown_connection(BlockDriverState *bs) 288 { 289 BDRVNBDState *s = bs->opaque; 290 struct nbd_request request; 291 292 request.type = NBD_CMD_DISC; 293 request.from = 0; 294 request.len = 0; 295 nbd_send_request(s->sock, &request); 296 297 qemu_aio_set_fd_handler(s->sock, NULL, NULL, NULL, NULL, NULL); 298 closesocket(s->sock); 299 } 300 301 static int nbd_open(BlockDriverState *bs, const char* filename, int flags) 302 { 303 BDRVNBDState *s = bs->opaque; 304 int result; 305 306 qemu_co_mutex_init(&s->send_mutex); 307 qemu_co_mutex_init(&s->free_sema); 308 309 /* Pop the config into our state object. Exit if invalid. */ 310 result = nbd_config(s, filename, flags); 311 if (result != 0) { 312 return result; 313 } 314 315 /* establish TCP connection, return error if it fails 316 * TODO: Configurable retry-until-timeout behaviour. 317 */ 318 result = nbd_establish_connection(bs); 319 320 return result; 321 } 322 323 static int nbd_co_readv_1(BlockDriverState *bs, int64_t sector_num, 324 int nb_sectors, QEMUIOVector *qiov, 325 int offset) 326 { 327 BDRVNBDState *s = bs->opaque; 328 struct nbd_request request; 329 struct nbd_reply reply; 330 331 request.type = NBD_CMD_READ; 332 request.from = sector_num * 512; 333 request.len = nb_sectors * 512; 334 335 nbd_coroutine_start(s, &request); 336 if (nbd_co_send_request(s, &request, NULL, 0) == -1) { 337 reply.error = errno; 338 } else { 339 nbd_co_receive_reply(s, &request, &reply, qiov->iov, offset); 340 } 341 nbd_coroutine_end(s, &request); 342 return -reply.error; 343 344 } 345 346 static int nbd_co_writev_1(BlockDriverState *bs, int64_t sector_num, 347 int nb_sectors, QEMUIOVector *qiov, 348 int offset) 349 { 350 BDRVNBDState *s = bs->opaque; 351 struct nbd_request request; 352 struct nbd_reply reply; 353 354 request.type = NBD_CMD_WRITE; 355 if (!bdrv_enable_write_cache(bs) && (s->nbdflags & NBD_FLAG_SEND_FUA)) { 356 request.type |= NBD_CMD_FLAG_FUA; 357 } 358 359 request.from = sector_num * 512; 360 request.len = nb_sectors * 512; 361 362 nbd_coroutine_start(s, &request); 363 if (nbd_co_send_request(s, &request, qiov->iov, offset) == -1) { 364 reply.error = errno; 365 } else { 366 nbd_co_receive_reply(s, &request, &reply, NULL, 0); 367 } 368 nbd_coroutine_end(s, &request); 369 return -reply.error; 370 } 371 372 /* qemu-nbd has a limit of slightly less than 1M per request. Try to 373 * remain aligned to 4K. */ 374 #define NBD_MAX_SECTORS 2040 375 376 static int nbd_co_readv(BlockDriverState *bs, int64_t sector_num, 377 int nb_sectors, QEMUIOVector *qiov) 378 { 379 int offset = 0; 380 int ret; 381 while (nb_sectors > NBD_MAX_SECTORS) { 382 ret = nbd_co_readv_1(bs, sector_num, NBD_MAX_SECTORS, qiov, offset); 383 if (ret < 0) { 384 return ret; 385 } 386 offset += NBD_MAX_SECTORS * 512; 387 sector_num += NBD_MAX_SECTORS; 388 nb_sectors -= NBD_MAX_SECTORS; 389 } 390 return nbd_co_readv_1(bs, sector_num, nb_sectors, qiov, offset); 391 } 392 393 static int nbd_co_writev(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_writev_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_writev_1(bs, sector_num, nb_sectors, qiov, offset); 408 } 409 410 static int nbd_co_flush(BlockDriverState *bs) 411 { 412 BDRVNBDState *s = bs->opaque; 413 struct nbd_request request; 414 struct nbd_reply reply; 415 416 if (!(s->nbdflags & NBD_FLAG_SEND_FLUSH)) { 417 return 0; 418 } 419 420 request.type = NBD_CMD_FLUSH; 421 if (s->nbdflags & NBD_FLAG_SEND_FUA) { 422 request.type |= NBD_CMD_FLAG_FUA; 423 } 424 425 request.from = 0; 426 request.len = 0; 427 428 nbd_coroutine_start(s, &request); 429 if (nbd_co_send_request(s, &request, NULL, 0) == -1) { 430 reply.error = errno; 431 } else { 432 nbd_co_receive_reply(s, &request, &reply, NULL, 0); 433 } 434 nbd_coroutine_end(s, &request); 435 return -reply.error; 436 } 437 438 static int nbd_co_discard(BlockDriverState *bs, int64_t sector_num, 439 int nb_sectors) 440 { 441 BDRVNBDState *s = bs->opaque; 442 struct nbd_request request; 443 struct nbd_reply reply; 444 445 if (!(s->nbdflags & NBD_FLAG_SEND_TRIM)) { 446 return 0; 447 } 448 request.type = NBD_CMD_TRIM; 449 request.from = sector_num * 512;; 450 request.len = nb_sectors * 512; 451 452 nbd_coroutine_start(s, &request); 453 if (nbd_co_send_request(s, &request, NULL, 0) == -1) { 454 reply.error = errno; 455 } else { 456 nbd_co_receive_reply(s, &request, &reply, NULL, 0); 457 } 458 nbd_coroutine_end(s, &request); 459 return -reply.error; 460 } 461 462 static void nbd_close(BlockDriverState *bs) 463 { 464 BDRVNBDState *s = bs->opaque; 465 g_free(s->export_name); 466 g_free(s->host_spec); 467 468 nbd_teardown_connection(bs); 469 } 470 471 static int64_t nbd_getlength(BlockDriverState *bs) 472 { 473 BDRVNBDState *s = bs->opaque; 474 475 return s->size; 476 } 477 478 static BlockDriver bdrv_nbd = { 479 .format_name = "nbd", 480 .instance_size = sizeof(BDRVNBDState), 481 .bdrv_file_open = nbd_open, 482 .bdrv_co_readv = nbd_co_readv, 483 .bdrv_co_writev = nbd_co_writev, 484 .bdrv_close = nbd_close, 485 .bdrv_co_flush_to_os = nbd_co_flush, 486 .bdrv_co_discard = nbd_co_discard, 487 .bdrv_getlength = nbd_getlength, 488 .protocol_name = "nbd", 489 }; 490 491 static void bdrv_nbd_init(void) 492 { 493 bdrv_register(&bdrv_nbd); 494 } 495 496 block_init(bdrv_nbd_init); 497