posix-aio-compat.c

   1 /*
   2  * QEMU posix-aio emulation
   3  *
   4  * Copyright IBM, Corp. 2008
   5  *
   6  * Authors:
   7  *  Anthony Liguori   <aliguori@us.ibm.com>
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2.  See
  10  * the COPYING file in the top-level directory.
  11  *
  12  */
  13
  14 #include <sys/ioctl.h>
  15 #include <sys/types.h>
  16 #include <pthread.h>
  17 #include <unistd.h>
  18 #include <errno.h>
  19 #include <time.h>
  20 #include <signal.h>
  21 #include <string.h>
  22 #include <stdlib.h>
  23 #include <stdio.h>
  24
  25 #include "qemu-queue.h"
  26 #include "osdep.h"
  27 #include "qemu-common.h"
  28 #include "trace.h"
  29 #include "block_int.h"
  30
  31 #include "block/raw-posix-aio.h"
  32
  33
  34 struct qemu_paiocb {
  35     BlockDriverAIOCB common;
  36     int aio_fildes;
  37     union {
  38         struct iovec *aio_iov;
  39         void *aio_ioctl_buf;
  40     };
  41     int aio_niov;
  42     size_t aio_nbytes;
  43 #define aio_ioctl_cmd   aio_nbytes /* for QEMU_AIO_IOCTL */
  44     int ev_signo;
  45     off_t aio_offset;
  46
  47     QTAILQ_ENTRY(qemu_paiocb) node;
  48     int aio_type;
  49     ssize_t ret;
  50     int active;
  51     struct qemu_paiocb *next;
  52
  53     int async_context_id;
  54 };
  55
  56 typedef struct PosixAioState {
  57     int rfd, wfd;
  58     struct qemu_paiocb *first_aio;
  59 } PosixAioState;
  60
  61
  62 static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
  63 static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
  64 static pthread_t thread_id;
  65 static pthread_attr_t attr;
  66 static int max_threads = 64;
  67 static int cur_threads = 0;
  68 static int idle_threads = 0;
  69 static QTAILQ_HEAD(, qemu_paiocb) request_list;
  70
  71 #ifdef CONFIG_PREADV
  72 static int preadv_present = 1;
  73 #else
  74 static int preadv_present = 0;
  75 #endif
  76
  77 static void die2(int err, const char *what)
  78 {
  79     fprintf(stderr, "%s failed: %s\n", what, strerror(err));
  80     abort();
  81 }
  82
  83 static void die(const char *what)
  84 {
  85     die2(errno, what);
  86 }
  87
  88 static void mutex_lock(pthread_mutex_t *mutex)
  89 {
  90     int ret = pthread_mutex_lock(mutex);
  91     if (ret) die2(ret, "pthread_mutex_lock");
  92 }
  93
  94 static void mutex_unlock(pthread_mutex_t *mutex)
  95 {
  96     int ret = pthread_mutex_unlock(mutex);
  97     if (ret) die2(ret, "pthread_mutex_unlock");
  98 }
  99
 100 static int cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
 101                            struct timespec *ts)
 102 {
 103     int ret = pthread_cond_timedwait(cond, mutex, ts);
 104     if (ret && ret != ETIMEDOUT) die2(ret, "pthread_cond_timedwait");
 105     return ret;
 106 }
 107
 108 static void cond_signal(pthread_cond_t *cond)
 109 {
 110     int ret = pthread_cond_signal(cond);
 111     if (ret) die2(ret, "pthread_cond_signal");
 112 }
 113
 114 static void thread_create(pthread_t *thread, pthread_attr_t *attr,
 115                           void *(*start_routine)(void*), void *arg)
 116 {
 117     int ret = pthread_create(thread, attr, start_routine, arg);
 118     if (ret) die2(ret, "pthread_create");
 119 }
 120
 121 static ssize_t handle_aiocb_ioctl(struct qemu_paiocb *aiocb)
 122 {
 123     int ret;
 124
 125     ret = ioctl(aiocb->aio_fildes, aiocb->aio_ioctl_cmd, aiocb->aio_ioctl_buf);
 126     if (ret == -1)
 127         return -errno;
 128
 129     /*
 130      * This looks weird, but the aio code only consideres a request
 131      * successfull if it has written the number full number of bytes.
 132      *
 133      * Now we overload aio_nbytes as aio_ioctl_cmd for the ioctl command,
 134      * so in fact we return the ioctl command here to make posix_aio_read()
 135      * happy..
 136      */
 137     return aiocb->aio_nbytes;
 138 }
 139
 140 static ssize_t handle_aiocb_flush(struct qemu_paiocb *aiocb)
 141 {
 142     int ret;
 143
 144     ret = qemu_fdatasync(aiocb->aio_fildes);
 145     if (ret == -1)
 146         return -errno;
 147     return 0;
 148 }
 149
 150 #ifdef CONFIG_PREADV
 151
 152 static ssize_t
 153 qemu_preadv(int fd, const struct iovec *iov, int nr_iov, off_t offset)
 154 {
 155     return preadv(fd, iov, nr_iov, offset);
 156 }
 157
 158 static ssize_t
 159 qemu_pwritev(int fd, const struct iovec *iov, int nr_iov, off_t offset)
 160 {
 161     return pwritev(fd, iov, nr_iov, offset);
 162 }
 163
 164 #else
 165
 166 static ssize_t
 167 qemu_preadv(int fd, const struct iovec *iov, int nr_iov, off_t offset)
 168 {
 169     return -ENOSYS;
 170 }
 171
 172 static ssize_t
 173 qemu_pwritev(int fd, const struct iovec *iov, int nr_iov, off_t offset)
 174 {
 175     return -ENOSYS;
 176 }
 177
 178 #endif
 179
 180 static ssize_t handle_aiocb_rw_vector(struct qemu_paiocb *aiocb)
 181 {
 182     size_t offset = 0;
 183     ssize_t len;
 184
 185     do {
 186         if (aiocb->aio_type & QEMU_AIO_WRITE)
 187             len = qemu_pwritev(aiocb->aio_fildes,
 188                                aiocb->aio_iov,
 189                                aiocb->aio_niov,
 190                                aiocb->aio_offset + offset);
 191          else
 192             len = qemu_preadv(aiocb->aio_fildes,
 193                               aiocb->aio_iov,
 194                               aiocb->aio_niov,
 195                               aiocb->aio_offset + offset);
 196     } while (len == -1 && errno == EINTR);
 197
 198     if (len == -1)
 199         return -errno;
 200     return len;
 201 }
 202
 203 static ssize_t handle_aiocb_rw_linear(struct qemu_paiocb *aiocb, char *buf)
 204 {
 205     ssize_t offset = 0;
 206     ssize_t len;
 207
 208     while (offset < aiocb->aio_nbytes) {
 209          if (aiocb->aio_type & QEMU_AIO_WRITE)
 210              len = pwrite(aiocb->aio_fildes,
 211                           (const char *)buf + offset,
 212                           aiocb->aio_nbytes - offset,
 213                           aiocb->aio_offset + offset);
 214          else
 215              len = pread(aiocb->aio_fildes,
 216                          buf + offset,
 217                          aiocb->aio_nbytes - offset,
 218                          aiocb->aio_offset + offset);
 219
 220          if (len == -1 && errno == EINTR)
 221              continue;
 222          else if (len == -1) {
 223              offset = -errno;
 224              break;
 225          } else if (len == 0)
 226              break;
 227
 228          offset += len;
 229     }
 230
 231     return offset;
 232 }
 233
 234 static ssize_t handle_aiocb_rw(struct qemu_paiocb *aiocb)
 235 {
 236     ssize_t nbytes;
 237     char *buf;
 238
 239     if (!(aiocb->aio_type & QEMU_AIO_MISALIGNED)) {
 240         /*
 241          * If there is just a single buffer, and it is properly aligned
 242          * we can just use plain pread/pwrite without any problems.
 243          */
 244         if (aiocb->aio_niov == 1)
 245              return handle_aiocb_rw_linear(aiocb, aiocb->aio_iov->iov_base);
 246
 247         /*
 248          * We have more than one iovec, and all are properly aligned.
 249          *
 250          * Try preadv/pwritev first and fall back to linearizing the
 251          * buffer if it's not supported.
 252          */
 253         if (preadv_present) {
 254             nbytes = handle_aiocb_rw_vector(aiocb);
 255             if (nbytes == aiocb->aio_nbytes)
 256                 return nbytes;
 257             if (nbytes < 0 && nbytes != -ENOSYS)
 258                 return nbytes;
 259             preadv_present = 0;
 260         }
 261
 262         /*
 263          * XXX(hch): short read/write.  no easy way to handle the reminder
 264          * using these interfaces.  For now retry using plain
 265          * pread/pwrite?
 266          */
 267     }
 268
 269     /*
 270      * Ok, we have to do it the hard way, copy all segments into
 271      * a single aligned buffer.
 272      */
 273     buf = qemu_blockalign(aiocb->common.bs, aiocb->aio_nbytes);
 274     if (aiocb->aio_type & QEMU_AIO_WRITE) {
 275         char *p = buf;
 276         int i;
 277
 278         for (i = 0; i < aiocb->aio_niov; ++i) {
 279             memcpy(p, aiocb->aio_iov[i].iov_base, aiocb->aio_iov[i].iov_len);
 280             p += aiocb->aio_iov[i].iov_len;
 281         }
 282     }
 283
 284     nbytes = handle_aiocb_rw_linear(aiocb, buf);
 285     if (!(aiocb->aio_type & QEMU_AIO_WRITE)) {
 286         char *p = buf;
 287         size_t count = aiocb->aio_nbytes, copy;
 288         int i;
 289
 290         for (i = 0; i < aiocb->aio_niov && count; ++i) {
 291             copy = count;
 292             if (copy > aiocb->aio_iov[i].iov_len)
 293                 copy = aiocb->aio_iov[i].iov_len;
 294             memcpy(aiocb->aio_iov[i].iov_base, p, copy);
 295             p     += copy;
 296             count -= copy;
 297         }
 298     }
 299     qemu_vfree(buf);
 300
 301     return nbytes;
 302 }
 303
 304 static void *aio_thread(void *unused)
 305 {
 306     pid_t pid;
 307
 308     pid = getpid();
 309
 310     while (1) {
 311         struct qemu_paiocb *aiocb;
 312         ssize_t ret = 0;
 313         qemu_timeval tv;
 314         struct timespec ts;
 315
 316         qemu_gettimeofday(&tv);
 317         ts.tv_sec = tv.tv_sec + 10;
 318         ts.tv_nsec = 0;
 319
 320         mutex_lock(&lock);
 321
 322         while (QTAILQ_EMPTY(&request_list) &&
 323                !(ret == ETIMEDOUT)) {
 324             ret = cond_timedwait(&cond, &lock, &ts);
 325         }
 326
 327         if (QTAILQ_EMPTY(&request_list))
 328             break;
 329
 330         aiocb = QTAILQ_FIRST(&request_list);
 331         QTAILQ_REMOVE(&request_list, aiocb, node);
 332         aiocb->active = 1;
 333         idle_threads--;
 334         mutex_unlock(&lock);
 335
 336         switch (aiocb->aio_type & QEMU_AIO_TYPE_MASK) {
 337         case QEMU_AIO_READ:
 338         case QEMU_AIO_WRITE:
 339             ret = handle_aiocb_rw(aiocb);
 340             break;
 341         case QEMU_AIO_FLUSH:
 342             ret = handle_aiocb_flush(aiocb);
 343             break;
 344         case QEMU_AIO_IOCTL:
 345             ret = handle_aiocb_ioctl(aiocb);
 346             break;
 347         default:
 348             fprintf(stderr, "invalid aio request (0x%x)\n", aiocb->aio_type);
 349             ret = -EINVAL;
 350             break;
 351         }
 352
 353         mutex_lock(&lock);
 354         aiocb->ret = ret;
 355         idle_threads++;
 356         mutex_unlock(&lock);
 357
 358         if (kill(pid, aiocb->ev_signo)) die("kill failed");
 359     }
 360
 361     idle_threads--;
 362     cur_threads--;
 363     mutex_unlock(&lock);
 364
 365     return NULL;
 366 }
 367
 368 static void spawn_thread(void)
 369 {
 370     sigset_t set, oldset;
 371
 372     cur_threads++;
 373     idle_threads++;
 374
 375     /* block all signals */
 376     if (sigfillset(&set)) die("sigfillset");
 377     if (sigprocmask(SIG_SETMASK, &set, &oldset)) die("sigprocmask");
 378
 379     thread_create(&thread_id, &attr, aio_thread, NULL);
 380
 381     if (sigprocmask(SIG_SETMASK, &oldset, NULL)) die("sigprocmask restore");
 382 }
 383
 384 static void qemu_paio_submit(struct qemu_paiocb *aiocb)
 385 {
 386     aiocb->ret = -EINPROGRESS;
 387     aiocb->active = 0;
 388     mutex_lock(&lock);
 389     if (idle_threads == 0 && cur_threads < max_threads)
 390         spawn_thread();
 391     QTAILQ_INSERT_TAIL(&request_list, aiocb, node);
 392     mutex_unlock(&lock);
 393     cond_signal(&cond);
 394 }
 395
 396 static ssize_t qemu_paio_return(struct qemu_paiocb *aiocb)
 397 {
 398     ssize_t ret;
 399
 400     mutex_lock(&lock);
 401     ret = aiocb->ret;
 402     mutex_unlock(&lock);
 403
 404     return ret;
 405 }
 406
 407 static int qemu_paio_error(struct qemu_paiocb *aiocb)
 408 {
 409     ssize_t ret = qemu_paio_return(aiocb);
 410
 411     if (ret < 0)
 412         ret = -ret;
 413     else
 414         ret = 0;
 415
 416     return ret;
 417 }
 418
 419 static int posix_aio_process_queue(void *opaque)
 420 {
 421     PosixAioState *s = opaque;
 422     struct qemu_paiocb *acb, **pacb;
 423     int ret;
 424     int result = 0;
 425     int async_context_id = get_async_context_id();
 426
 427     for(;;) {
 428         pacb = &s->first_aio;
 429         for(;;) {
 430             acb = *pacb;
 431             if (!acb)
 432                 return result;
 433
 434             /* we're only interested in requests in the right context */
 435             if (acb->async_context_id != async_context_id) {
 436                 pacb = &acb->next;
 437                 continue;
 438             }
 439
 440             ret = qemu_paio_error(acb);
 441             if (ret == ECANCELED) {
 442                 /* remove the request */
 443                 *pacb = acb->next;
 444                 qemu_aio_release(acb);
 445                 result = 1;
 446             } else if (ret != EINPROGRESS) {
 447                 /* end of aio */
 448                 if (ret == 0) {
 449                     ret = qemu_paio_return(acb);
 450                     if (ret == acb->aio_nbytes)
 451                         ret = 0;
 452                     else
 453                         ret = -EINVAL;
 454                 } else {
 455                     ret = -ret;
 456                 }
 457                 /* remove the request */
 458                 *pacb = acb->next;
 459                 /* call the callback */
 460                 acb->common.cb(acb->common.opaque, ret);
 461                 qemu_aio_release(acb);
 462                 result = 1;
 463                 break;
 464             } else {
 465                 pacb = &acb->next;
 466             }
 467         }
 468     }
 469
 470     return result;
 471 }
 472
 473 static void posix_aio_read(void *opaque)
 474 {
 475     PosixAioState *s = opaque;
 476     ssize_t len;
 477
 478     /* read all bytes from signal pipe */
 479     for (;;) {
 480         char bytes[16];
 481
 482         len = read(s->rfd, bytes, sizeof(bytes));
 483         if (len == -1 && errno == EINTR)
 484             continue; /* try again */
 485         if (len == sizeof(bytes))
 486             continue; /* more to read */
 487         break;
 488     }
 489
 490     posix_aio_process_queue(s);
 491 }
 492
 493 static int posix_aio_flush(void *opaque)
 494 {
 495     PosixAioState *s = opaque;
 496     return !!s->first_aio;
 497 }
 498
 499 static PosixAioState *posix_aio_state;
 500
 501 static void aio_signal_handler(int signum)
 502 {
 503     if (posix_aio_state) {
 504         char byte = 0;
 505         ssize_t ret;
 506
 507         ret = write(posix_aio_state->wfd, &byte, sizeof(byte));
 508         if (ret < 0 && errno != EAGAIN)
 509             die("write()");
 510     }
 511
 512     qemu_service_io();
 513 }
 514
 515 static void paio_remove(struct qemu_paiocb *acb)
 516 {
 517     struct qemu_paiocb **pacb;
 518
 519     /* remove the callback from the queue */
 520     pacb = &posix_aio_state->first_aio;
 521     for(;;) {
 522         if (*pacb == NULL) {
 523             fprintf(stderr, "paio_remove: aio request not found!\n");
 524             break;
 525         } else if (*pacb == acb) {
 526             *pacb = acb->next;
 527             qemu_aio_release(acb);
 528             break;
 529         }
 530         pacb = &(*pacb)->next;
 531     }
 532 }
 533
 534 static void paio_cancel(BlockDriverAIOCB *blockacb)
 535 {
 536     struct qemu_paiocb *acb = (struct qemu_paiocb *)blockacb;
 537     int active = 0;
 538
 539     mutex_lock(&lock);
 540     if (!acb->active) {
 541         QTAILQ_REMOVE(&request_list, acb, node);
 542         acb->ret = -ECANCELED;
 543     } else if (acb->ret == -EINPROGRESS) {
 544         active = 1;
 545     }
 546     mutex_unlock(&lock);
 547
 548     if (active) {
 549         /* fail safe: if the aio could not be canceled, we wait for
 550            it */
 551         while (qemu_paio_error(acb) == EINPROGRESS)
 552             ;
 553     }
 554
 555     paio_remove(acb);
 556 }
 557
 558 static AIOPool raw_aio_pool = {
 559     .aiocb_size         = sizeof(struct qemu_paiocb),
 560     .cancel             = paio_cancel,
 561 };
 562
 563 BlockDriverAIOCB *paio_submit(BlockDriverState *bs, int fd,
 564         int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
 565         BlockDriverCompletionFunc *cb, void *opaque, int type)
 566 {
 567     struct qemu_paiocb *acb;
 568
 569     acb = qemu_aio_get(&raw_aio_pool, bs, cb, opaque);
 570     if (!acb)
 571         return NULL;
 572     acb->aio_type = type;
 573     acb->aio_fildes = fd;
 574     acb->ev_signo = SIGUSR2;
 575     acb->async_context_id = get_async_context_id();
 576
 577     if (qiov) {
 578         acb->aio_iov = qiov->iov;
 579         acb->aio_niov = qiov->niov;
 580     }
 581     acb->aio_nbytes = nb_sectors * 512;
 582     acb->aio_offset = sector_num * 512;
 583
 584     acb->next = posix_aio_state->first_aio;
 585     posix_aio_state->first_aio = acb;
 586
 587     trace_paio_submit(acb, opaque, sector_num, nb_sectors, type);
 588     qemu_paio_submit(acb);
 589     return &acb->common;
 590 }
 591
 592 BlockDriverAIOCB *paio_ioctl(BlockDriverState *bs, int fd,
 593         unsigned long int req, void *buf,
 594         BlockDriverCompletionFunc *cb, void *opaque)
 595 {
 596     struct qemu_paiocb *acb;
 597
 598     acb = qemu_aio_get(&raw_aio_pool, bs, cb, opaque);
 599     if (!acb)
 600         return NULL;
 601     acb->aio_type = QEMU_AIO_IOCTL;
 602     acb->aio_fildes = fd;
 603     acb->ev_signo = SIGUSR2;
 604     acb->async_context_id = get_async_context_id();
 605     acb->aio_offset = 0;
 606     acb->aio_ioctl_buf = buf;
 607     acb->aio_ioctl_cmd = req;
 608
 609     acb->next = posix_aio_state->first_aio;
 610     posix_aio_state->first_aio = acb;
 611
 612     qemu_paio_submit(acb);
 613     return &acb->common;
 614 }
 615
 616 int paio_init(void)
 617 {
 618     struct sigaction act;
 619     PosixAioState *s;
 620     int fds[2];
 621     int ret;
 622
 623     if (posix_aio_state)
 624         return 0;
 625
 626     s = qemu_malloc(sizeof(PosixAioState));
 627
 628     sigfillset(&act.sa_mask);
 629     act.sa_flags = 0; /* do not restart syscalls to interrupt select() */
 630     act.sa_handler = aio_signal_handler;
 631     sigaction(SIGUSR2, &act, NULL);
 632
 633     s->first_aio = NULL;
 634     if (qemu_pipe(fds) == -1) {
 635         fprintf(stderr, "failed to create pipe\n");
 636         return -1;
 637     }
 638
 639     s->rfd = fds[0];
 640     s->wfd = fds[1];
 641
 642     fcntl(s->rfd, F_SETFL, O_NONBLOCK);
 643     fcntl(s->wfd, F_SETFL, O_NONBLOCK);
 644
 645     qemu_aio_set_fd_handler(s->rfd, posix_aio_read, NULL, posix_aio_flush,
 646         posix_aio_process_queue, s);
 647
 648     ret = pthread_attr_init(&attr);
 649     if (ret)
 650         die2(ret, "pthread_attr_init");
 651
 652     ret = pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
 653     if (ret)
 654         die2(ret, "pthread_attr_setdetachstate");
 655
 656     QTAILQ_INIT(&request_list);
 657
 658     posix_aio_state = s;
 659     return 0;
 660 }