block/nbd.c

   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 typedef struct BDRVNBDState {
  50     int sock;
  51     uint32_t nbdflags;
  52     off_t size;
  53     size_t blocksize;
  54     char *export_name; /* An NBD server may export several devices */
  55
  56     CoMutex mutex;
  57     Coroutine *coroutine;
  58
  59     struct nbd_reply reply;
  60
  61     /* If it begins with  '/', this is a UNIX domain socket. Otherwise,
  62      * it's a string of the form <hostname|ip4|\[ip6\]>:port
  63      */
  64     char *host_spec;
  65 } BDRVNBDState;
  66
  67 static int nbd_config(BDRVNBDState *s, const char *filename, int flags)
  68 {
  69     char *file;
  70     char *export_name;
  71     const char *host_spec;
  72     const char *unixpath;
  73     int err = -EINVAL;
  74
  75     file = g_strdup(filename);
  76
  77     export_name = strstr(file, EN_OPTSTR);
  78     if (export_name) {
  79         if (export_name[strlen(EN_OPTSTR)] == 0) {
  80             goto out;
  81         }
  82         export_name[0] = 0; /* truncate 'file' */
  83         export_name += strlen(EN_OPTSTR);
  84         s->export_name = g_strdup(export_name);
  85     }
  86
  87     /* extract the host_spec - fail if it's not nbd:... */
  88     if (!strstart(file, "nbd:", &host_spec)) {
  89         goto out;
  90     }
  91
  92     /* are we a UNIX or TCP socket? */
  93     if (strstart(host_spec, "unix:", &unixpath)) {
  94         if (unixpath[0] != '/') { /* We demand  an absolute path*/
  95             goto out;
  96         }
  97         s->host_spec = g_strdup(unixpath);
  98     } else {
  99         s->host_spec = g_strdup(host_spec);
 100     }
 101
 102     err = 0;
 103
 104 out:
 105     g_free(file);
 106     if (err != 0) {
 107         g_free(s->export_name);
 108         g_free(s->host_spec);
 109     }
 110     return err;
 111 }
 112
 113 static void nbd_coroutine_start(BDRVNBDState *s, struct nbd_request *request)
 114 {
 115     qemu_co_mutex_lock(&s->mutex);
 116     s->coroutine = qemu_coroutine_self();
 117     request->handle = (uint64_t)(intptr_t)s;
 118 }
 119
 120 static int nbd_have_request(void *opaque)
 121 {
 122     BDRVNBDState *s = opaque;
 123
 124     return !!s->coroutine;
 125 }
 126
 127 static void nbd_reply_ready(void *opaque)
 128 {
 129     BDRVNBDState *s = opaque;
 130
 131     if (s->reply.handle == 0) {
 132         /* No reply already in flight.  Fetch a header.  */
 133         if (nbd_receive_reply(s->sock, &s->reply) < 0) {
 134             s->reply.handle = 0;
 135         }
 136     }
 137
 138     /* There's no need for a mutex on the receive side, because the
 139      * handler acts as a synchronization point and ensures that only
 140      * one coroutine is called until the reply finishes.  */
 141     if (s->coroutine) {
 142         qemu_coroutine_enter(s->coroutine, NULL);
 143     }
 144 }
 145
 146 static void nbd_restart_write(void *opaque)
 147 {
 148     BDRVNBDState *s = opaque;
 149     qemu_coroutine_enter(s->coroutine, NULL);
 150 }
 151
 152 static int nbd_co_send_request(BDRVNBDState *s, struct nbd_request *request,
 153                                struct iovec *iov, int offset)
 154 {
 155     int rc, ret;
 156
 157     qemu_aio_set_fd_handler(s->sock, nbd_reply_ready, nbd_restart_write,
 158                             nbd_have_request, NULL, s);
 159     rc = nbd_send_request(s->sock, request);
 160     if (rc != -1 && iov) {
 161         ret = qemu_co_sendv(s->sock, iov, request->len, offset);
 162         if (ret != request->len) {
 163             errno = -EIO;
 164             rc = -1;
 165         }
 166     }
 167     qemu_aio_set_fd_handler(s->sock, nbd_reply_ready, NULL,
 168                             nbd_have_request, NULL, s);
 169     return rc;
 170 }
 171
 172 static void nbd_co_receive_reply(BDRVNBDState *s, struct nbd_request *request,
 173                                  struct nbd_reply *reply,
 174                                  struct iovec *iov, int offset)
 175 {
 176     int ret;
 177
 178     /* Wait until we're woken up by the read handler.  */
 179     qemu_coroutine_yield();
 180     *reply = s->reply;
 181     if (reply->handle != request->handle) {
 182         reply->error = EIO;
 183     } else {
 184         if (iov && reply->error == 0) {
 185             ret = qemu_co_recvv(s->sock, iov, request->len, offset);
 186             if (ret != request->len) {
 187                 reply->error = EIO;
 188             }
 189         }
 190
 191         /* Tell the read handler to read another header.  */
 192         s->reply.handle = 0;
 193     }
 194 }
 195
 196 static void nbd_coroutine_end(BDRVNBDState *s, struct nbd_request *request)
 197 {
 198     s->coroutine = NULL;
 199     qemu_co_mutex_unlock(&s->mutex);
 200 }
 201
 202 static int nbd_establish_connection(BlockDriverState *bs)
 203 {
 204     BDRVNBDState *s = bs->opaque;
 205     int sock;
 206     int ret;
 207     off_t size;
 208     size_t blocksize;
 209
 210     if (s->host_spec[0] == '/') {
 211         sock = unix_socket_outgoing(s->host_spec);
 212     } else {
 213         sock = tcp_socket_outgoing_spec(s->host_spec);
 214     }
 215
 216     /* Failed to establish connection */
 217     if (sock == -1) {
 218         logout("Failed to establish connection to NBD server\n");
 219         return -errno;
 220     }
 221
 222     /* NBD handshake */
 223     ret = nbd_receive_negotiate(sock, s->export_name, &s->nbdflags, &size,
 224                                 &blocksize);
 225     if (ret == -1) {
 226         logout("Failed to negotiate with the NBD server\n");
 227         closesocket(sock);
 228         return -errno;
 229     }
 230
 231     /* Now that we're connected, set the socket to be non-blocking and
 232      * kick the reply mechanism.  */
 233     socket_set_nonblock(sock);
 234     qemu_aio_set_fd_handler(s->sock, nbd_reply_ready, NULL,
 235                             nbd_have_request, NULL, s);
 236
 237     s->sock = sock;
 238     s->size = size;
 239     s->blocksize = blocksize;
 240
 241     logout("Established connection with NBD server\n");
 242     return 0;
 243 }
 244
 245 static void nbd_teardown_connection(BlockDriverState *bs)
 246 {
 247     BDRVNBDState *s = bs->opaque;
 248     struct nbd_request request;
 249
 250     request.type = NBD_CMD_DISC;
 251     request.from = 0;
 252     request.len = 0;
 253     nbd_send_request(s->sock, &request);
 254
 255     qemu_aio_set_fd_handler(s->sock, NULL, NULL, NULL, NULL, NULL);
 256     closesocket(s->sock);
 257 }
 258
 259 static int nbd_open(BlockDriverState *bs, const char* filename, int flags)
 260 {
 261     BDRVNBDState *s = bs->opaque;
 262     int result;
 263
 264     qemu_co_mutex_init(&s->mutex);
 265
 266     /* Pop the config into our state object. Exit if invalid. */
 267     result = nbd_config(s, filename, flags);
 268     if (result != 0) {
 269         return result;
 270     }
 271
 272     /* establish TCP connection, return error if it fails
 273      * TODO: Configurable retry-until-timeout behaviour.
 274      */
 275     result = nbd_establish_connection(bs);
 276
 277     return result;
 278 }
 279
 280 static int nbd_co_readv(BlockDriverState *bs, int64_t sector_num,
 281                         int nb_sectors, QEMUIOVector *qiov)
 282 {
 283     BDRVNBDState *s = bs->opaque;
 284     struct nbd_request request;
 285     struct nbd_reply reply;
 286
 287     request.type = NBD_CMD_READ;
 288     request.from = sector_num * 512;
 289     request.len = nb_sectors * 512;
 290
 291     nbd_coroutine_start(s, &request);
 292     if (nbd_co_send_request(s, &request, NULL, 0) == -1) {
 293         reply.error = errno;
 294     } else {
 295         nbd_co_receive_reply(s, &request, &reply, qiov->iov, 0);
 296     }
 297     nbd_coroutine_end(s, &request);
 298     return -reply.error;
 299
 300 }
 301
 302 static int nbd_co_writev(BlockDriverState *bs, int64_t sector_num,
 303                          int nb_sectors, QEMUIOVector *qiov)
 304 {
 305     BDRVNBDState *s = bs->opaque;
 306     struct nbd_request request;
 307     struct nbd_reply reply;
 308
 309     request.type = NBD_CMD_WRITE;
 310     request.from = sector_num * 512;
 311     request.len = nb_sectors * 512;
 312
 313     nbd_coroutine_start(s, &request);
 314     if (nbd_co_send_request(s, &request, qiov->iov, 0) == -1) {
 315         reply.error = errno;
 316     } else {
 317         nbd_co_receive_reply(s, &request, &reply, NULL, 0);
 318     }
 319     nbd_coroutine_end(s, &request);
 320     return -reply.error;
 321 }
 322
 323 static void nbd_close(BlockDriverState *bs)
 324 {
 325     BDRVNBDState *s = bs->opaque;
 326     g_free(s->export_name);
 327     g_free(s->host_spec);
 328
 329     nbd_teardown_connection(bs);
 330 }
 331
 332 static int64_t nbd_getlength(BlockDriverState *bs)
 333 {
 334     BDRVNBDState *s = bs->opaque;
 335
 336     return s->size;
 337 }
 338
 339 static BlockDriver bdrv_nbd = {
 340     .format_name        = "nbd",
 341     .instance_size      = sizeof(BDRVNBDState),
 342     .bdrv_file_open     = nbd_open,
 343     .bdrv_co_readv      = nbd_co_readv,
 344     .bdrv_co_writev     = nbd_co_writev,
 345     .bdrv_close         = nbd_close,
 346     .bdrv_getlength     = nbd_getlength,
 347     .protocol_name      = "nbd",
 348 };
 349
 350 static void bdrv_nbd_init(void)
 351 {
 352     bdrv_register(&bdrv_nbd);
 353 }
 354
 355 block_init(bdrv_nbd_init);