block/nbd-client.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 "nbd-client.h"
  30 #include "qemu/sockets.h"
  31
  32 #define HANDLE_TO_INDEX(bs, handle) ((handle) ^ ((uint64_t)(intptr_t)bs))
  33 #define INDEX_TO_HANDLE(bs, index)  ((index)  ^ ((uint64_t)(intptr_t)bs))
  34
  35 static void nbd_recv_coroutines_enter_all(NbdClientSession *s)
  36 {
  37     int i;
  38
  39     for (i = 0; i < MAX_NBD_REQUESTS; i++) {
  40         if (s->recv_coroutine[i]) {
  41             qemu_coroutine_enter(s->recv_coroutine[i], NULL);
  42         }
  43     }
  44 }
  45
  46 static void nbd_teardown_connection(BlockDriverState *bs)
  47 {
  48     NbdClientSession *client = nbd_get_client_session(bs);
  49
  50     /* finish any pending coroutines */
  51     shutdown(client->sock, 2);
  52     nbd_recv_coroutines_enter_all(client);
  53
  54     nbd_client_detach_aio_context(bs);
  55     closesocket(client->sock);
  56     client->sock = -1;
  57 }
  58
  59 static void nbd_reply_ready(void *opaque)
  60 {
  61     BlockDriverState *bs = opaque;
  62     NbdClientSession *s = nbd_get_client_session(bs);
  63     uint64_t i;
  64     int ret;
  65
  66     if (s->reply.handle == 0) {
  67         /* No reply already in flight.  Fetch a header.  It is possible
  68          * that another thread has done the same thing in parallel, so
  69          * the socket is not readable anymore.
  70          */
  71         ret = nbd_receive_reply(s->sock, &s->reply);
  72         if (ret == -EAGAIN) {
  73             return;
  74         }
  75         if (ret < 0) {
  76             s->reply.handle = 0;
  77             goto fail;
  78         }
  79     }
  80
  81     /* There's no need for a mutex on the receive side, because the
  82      * handler acts as a synchronization point and ensures that only
  83      * one coroutine is called until the reply finishes.  */
  84     i = HANDLE_TO_INDEX(s, s->reply.handle);
  85     if (i >= MAX_NBD_REQUESTS) {
  86         goto fail;
  87     }
  88
  89     if (s->recv_coroutine[i]) {
  90         qemu_coroutine_enter(s->recv_coroutine[i], NULL);
  91         return;
  92     }
  93
  94 fail:
  95     nbd_teardown_connection(bs);
  96 }
  97
  98 static void nbd_restart_write(void *opaque)
  99 {
 100     BlockDriverState *bs = opaque;
 101
 102     qemu_coroutine_enter(nbd_get_client_session(bs)->send_coroutine, NULL);
 103 }
 104
 105 static int nbd_co_send_request(BlockDriverState *bs,
 106                                struct nbd_request *request,
 107                                QEMUIOVector *qiov, int offset)
 108 {
 109     NbdClientSession *s = nbd_get_client_session(bs);
 110     AioContext *aio_context;
 111     int rc, ret, i;
 112
 113     qemu_co_mutex_lock(&s->send_mutex);
 114
 115     for (i = 0; i < MAX_NBD_REQUESTS; i++) {
 116         if (s->recv_coroutine[i] == NULL) {
 117             s->recv_coroutine[i] = qemu_coroutine_self();
 118             break;
 119         }
 120     }
 121
 122     assert(i < MAX_NBD_REQUESTS);
 123     request->handle = INDEX_TO_HANDLE(s, i);
 124     s->send_coroutine = qemu_coroutine_self();
 125     aio_context = bdrv_get_aio_context(bs);
 126
 127     aio_set_fd_handler(aio_context, s->sock, false,
 128                        nbd_reply_ready, nbd_restart_write, bs);
 129     if (qiov) {
 130         if (!s->is_unix) {
 131             socket_set_cork(s->sock, 1);
 132         }
 133         rc = nbd_send_request(s->sock, request);
 134         if (rc >= 0) {
 135             ret = qemu_co_sendv(s->sock, qiov->iov, qiov->niov,
 136                                 offset, request->len);
 137             if (ret != request->len) {
 138                 rc = -EIO;
 139             }
 140         }
 141         if (!s->is_unix) {
 142             socket_set_cork(s->sock, 0);
 143         }
 144     } else {
 145         rc = nbd_send_request(s->sock, request);
 146     }
 147     aio_set_fd_handler(aio_context, s->sock, false,
 148                        nbd_reply_ready, NULL, bs);
 149     s->send_coroutine = NULL;
 150     qemu_co_mutex_unlock(&s->send_mutex);
 151     return rc;
 152 }
 153
 154 static void nbd_co_receive_reply(NbdClientSession *s,
 155     struct nbd_request *request, struct nbd_reply *reply,
 156     QEMUIOVector *qiov, int offset)
 157 {
 158     int ret;
 159
 160     /* Wait until we're woken up by the read handler.  TODO: perhaps
 161      * peek at the next reply and avoid yielding if it's ours?  */
 162     qemu_coroutine_yield();
 163     *reply = s->reply;
 164     if (reply->handle != request->handle) {
 165         reply->error = EIO;
 166     } else {
 167         if (qiov && reply->error == 0) {
 168             ret = qemu_co_recvv(s->sock, qiov->iov, qiov->niov,
 169                                 offset, request->len);
 170             if (ret != request->len) {
 171                 reply->error = EIO;
 172             }
 173         }
 174
 175         /* Tell the read handler to read another header.  */
 176         s->reply.handle = 0;
 177     }
 178 }
 179
 180 static void nbd_coroutine_start(NbdClientSession *s,
 181    struct nbd_request *request)
 182 {
 183     /* Poor man semaphore.  The free_sema is locked when no other request
 184      * can be accepted, and unlocked after receiving one reply.  */
 185     if (s->in_flight >= MAX_NBD_REQUESTS - 1) {
 186         qemu_co_mutex_lock(&s->free_sema);
 187         assert(s->in_flight < MAX_NBD_REQUESTS);
 188     }
 189     s->in_flight++;
 190
 191     /* s->recv_coroutine[i] is set as soon as we get the send_lock.  */
 192 }
 193
 194 static void nbd_coroutine_end(NbdClientSession *s,
 195     struct nbd_request *request)
 196 {
 197     int i = HANDLE_TO_INDEX(s, request->handle);
 198     s->recv_coroutine[i] = NULL;
 199     if (s->in_flight-- == MAX_NBD_REQUESTS) {
 200         qemu_co_mutex_unlock(&s->free_sema);
 201     }
 202 }
 203
 204 static int nbd_co_readv_1(BlockDriverState *bs, int64_t sector_num,
 205                           int nb_sectors, QEMUIOVector *qiov,
 206                           int offset)
 207 {
 208     NbdClientSession *client = nbd_get_client_session(bs);
 209     struct nbd_request request = { .type = NBD_CMD_READ };
 210     struct nbd_reply reply;
 211     ssize_t ret;
 212
 213     request.from = sector_num * 512;
 214     request.len = nb_sectors * 512;
 215
 216     nbd_coroutine_start(client, &request);
 217     ret = nbd_co_send_request(bs, &request, NULL, 0);
 218     if (ret < 0) {
 219         reply.error = -ret;
 220     } else {
 221         nbd_co_receive_reply(client, &request, &reply, qiov, offset);
 222     }
 223     nbd_coroutine_end(client, &request);
 224     return -reply.error;
 225
 226 }
 227
 228 static int nbd_co_writev_1(BlockDriverState *bs, int64_t sector_num,
 229                            int nb_sectors, QEMUIOVector *qiov,
 230                            int offset)
 231 {
 232     NbdClientSession *client = nbd_get_client_session(bs);
 233     struct nbd_request request = { .type = NBD_CMD_WRITE };
 234     struct nbd_reply reply;
 235     ssize_t ret;
 236
 237     if (!bdrv_enable_write_cache(bs) &&
 238         (client->nbdflags & NBD_FLAG_SEND_FUA)) {
 239         request.type |= NBD_CMD_FLAG_FUA;
 240     }
 241
 242     request.from = sector_num * 512;
 243     request.len = nb_sectors * 512;
 244
 245     nbd_coroutine_start(client, &request);
 246     ret = nbd_co_send_request(bs, &request, qiov, offset);
 247     if (ret < 0) {
 248         reply.error = -ret;
 249     } else {
 250         nbd_co_receive_reply(client, &request, &reply, NULL, 0);
 251     }
 252     nbd_coroutine_end(client, &request);
 253     return -reply.error;
 254 }
 255
 256 /* qemu-nbd has a limit of slightly less than 1M per request.  Try to
 257  * remain aligned to 4K. */
 258 #define NBD_MAX_SECTORS 2040
 259
 260 int nbd_client_co_readv(BlockDriverState *bs, int64_t sector_num,
 261                         int nb_sectors, QEMUIOVector *qiov)
 262 {
 263     int offset = 0;
 264     int ret;
 265     while (nb_sectors > NBD_MAX_SECTORS) {
 266         ret = nbd_co_readv_1(bs, sector_num, NBD_MAX_SECTORS, qiov, offset);
 267         if (ret < 0) {
 268             return ret;
 269         }
 270         offset += NBD_MAX_SECTORS * 512;
 271         sector_num += NBD_MAX_SECTORS;
 272         nb_sectors -= NBD_MAX_SECTORS;
 273     }
 274     return nbd_co_readv_1(bs, sector_num, nb_sectors, qiov, offset);
 275 }
 276
 277 int nbd_client_co_writev(BlockDriverState *bs, int64_t sector_num,
 278                          int nb_sectors, QEMUIOVector *qiov)
 279 {
 280     int offset = 0;
 281     int ret;
 282     while (nb_sectors > NBD_MAX_SECTORS) {
 283         ret = nbd_co_writev_1(bs, sector_num, NBD_MAX_SECTORS, qiov, offset);
 284         if (ret < 0) {
 285             return ret;
 286         }
 287         offset += NBD_MAX_SECTORS * 512;
 288         sector_num += NBD_MAX_SECTORS;
 289         nb_sectors -= NBD_MAX_SECTORS;
 290     }
 291     return nbd_co_writev_1(bs, sector_num, nb_sectors, qiov, offset);
 292 }
 293
 294 int nbd_client_co_flush(BlockDriverState *bs)
 295 {
 296     NbdClientSession *client = nbd_get_client_session(bs);
 297     struct nbd_request request = { .type = NBD_CMD_FLUSH };
 298     struct nbd_reply reply;
 299     ssize_t ret;
 300
 301     if (!(client->nbdflags & NBD_FLAG_SEND_FLUSH)) {
 302         return 0;
 303     }
 304
 305     if (client->nbdflags & NBD_FLAG_SEND_FUA) {
 306         request.type |= NBD_CMD_FLAG_FUA;
 307     }
 308
 309     request.from = 0;
 310     request.len = 0;
 311
 312     nbd_coroutine_start(client, &request);
 313     ret = nbd_co_send_request(bs, &request, NULL, 0);
 314     if (ret < 0) {
 315         reply.error = -ret;
 316     } else {
 317         nbd_co_receive_reply(client, &request, &reply, NULL, 0);
 318     }
 319     nbd_coroutine_end(client, &request);
 320     return -reply.error;
 321 }
 322
 323 int nbd_client_co_discard(BlockDriverState *bs, int64_t sector_num,
 324                           int nb_sectors)
 325 {
 326     NbdClientSession *client = nbd_get_client_session(bs);
 327     struct nbd_request request = { .type = NBD_CMD_TRIM };
 328     struct nbd_reply reply;
 329     ssize_t ret;
 330
 331     if (!(client->nbdflags & NBD_FLAG_SEND_TRIM)) {
 332         return 0;
 333     }
 334     request.from = sector_num * 512;
 335     request.len = nb_sectors * 512;
 336
 337     nbd_coroutine_start(client, &request);
 338     ret = nbd_co_send_request(bs, &request, NULL, 0);
 339     if (ret < 0) {
 340         reply.error = -ret;
 341     } else {
 342         nbd_co_receive_reply(client, &request, &reply, NULL, 0);
 343     }
 344     nbd_coroutine_end(client, &request);
 345     return -reply.error;
 346
 347 }
 348
 349 void nbd_client_detach_aio_context(BlockDriverState *bs)
 350 {
 351     aio_set_fd_handler(bdrv_get_aio_context(bs),
 352                        nbd_get_client_session(bs)->sock,
 353                        false, NULL, NULL, NULL);
 354 }
 355
 356 void nbd_client_attach_aio_context(BlockDriverState *bs,
 357                                    AioContext *new_context)
 358 {
 359     aio_set_fd_handler(new_context, nbd_get_client_session(bs)->sock,
 360                        false, nbd_reply_ready, NULL, bs);
 361 }
 362
 363 void nbd_client_close(BlockDriverState *bs)
 364 {
 365     NbdClientSession *client = nbd_get_client_session(bs);
 366     struct nbd_request request = {
 367         .type = NBD_CMD_DISC,
 368         .from = 0,
 369         .len = 0
 370     };
 371
 372     if (client->sock == -1) {
 373         return;
 374     }
 375
 376     nbd_send_request(client->sock, &request);
 377
 378     nbd_teardown_connection(bs);
 379 }
 380
 381 int nbd_client_init(BlockDriverState *bs, int sock, const char *export,
 382                     Error **errp)
 383 {
 384     NbdClientSession *client = nbd_get_client_session(bs);
 385     int ret;
 386
 387     /* NBD handshake */
 388     logout("session init %s\n", export);
 389     qemu_set_block(sock);
 390     ret = nbd_receive_negotiate(sock, export,
 391                                 &client->nbdflags, &client->size, errp);
 392     if (ret < 0) {
 393         logout("Failed to negotiate with the NBD server\n");
 394         closesocket(sock);
 395         return ret;
 396     }
 397
 398     qemu_co_mutex_init(&client->send_mutex);
 399     qemu_co_mutex_init(&client->free_sema);
 400     client->sock = sock;
 401
 402     /* Now that we're connected, set the socket to be non-blocking and
 403      * kick the reply mechanism.  */
 404     qemu_set_nonblock(sock);
 405     nbd_client_attach_aio_context(bs, bdrv_get_aio_context(bs));
 406
 407     logout("Established connection with NBD server\n");
 408     return 0;
 409 }