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