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 "sysemu.h"
  28 #include "qemu-common.h"
  29 #include "trace.h"
  30 #include "block_int.h"
  31
  32 #include "block/raw-posix-aio.h"
  33
  34
  35 struct qemu_paiocb {
  36     BlockDriverAIOCB common;
  37     int aio_fildes;
  38     union {
  39         struct iovec *aio_iov;
  40         void *aio_ioctl_buf;
  41     };
  42     int aio_niov;
  43     size_t aio_nbytes;
  44 #define aio_ioctl_cmd   aio_nbytes /* for QEMU_AIO_IOCTL */
  45     int ev_signo;
  46     off_t aio_offset;
  47
  48     QTAILQ_ENTRY(qemu_paiocb) node;
  49     int aio_type;
  50     ssize_t ret;
  51     int active;
  52     struct qemu_paiocb *next;
  53
  54     int async_context_id;
  55 };
  56
  57 typedef struct PosixAioState {
  58     int rfd, wfd;
  59     struct qemu_paiocb *first_aio;
  60 } PosixAioState;
  61
  62
  63 static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
  64 static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
  65 static pthread_t thread_id;
  66 static pthread_attr_t attr;
  67 static int max_threads = 64;
  68 static int cur_threads = 0;
  69 static int idle_threads = 0;
  70 static QTAILQ_HEAD(, qemu_paiocb) request_list;
  71
  72 #ifdef CONFIG_PREADV
  73 static int preadv_present = 1;
  74 #else
  75 static int preadv_present = 0;
  76 #endif
  77
  78 static void die2(int err, const char *what)
  79 {
  80     fprintf(stderr, "%s failed: %s\n", what, strerror(err));
  81     abort();
  82 }
  83
  84 static void die(const char *what)
  85 {
  86     die2(errno, what);
  87 }
  88
  89 static void mutex_lock(pthread_mutex_t *mutex)
  90 {
  91     int ret = pthread_mutex_lock(mutex);
  92     if (ret) die2(ret, "pthread_mutex_lock");
  93 }
  94
  95 static void mutex_unlock(pthread_mutex_t *mutex)
  96 {
  97     int ret = pthread_mutex_unlock(mutex);
  98     if (ret) die2(ret, "pthread_mutex_unlock");
  99 }
 100
 101 static int cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
 102                            struct timespec *ts)
 103 {
 104     int ret = pthread_cond_timedwait(cond, mutex, ts);
 105     if (ret && ret != ETIMEDOUT) die2(ret, "pthread_cond_timedwait");
 106     return ret;
 107 }
 108
 109 static void cond_signal(pthread_cond_t *cond)
 110 {
 111     int ret = pthread_cond_signal(cond);
 112     if (ret) die2(ret, "pthread_cond_signal");
 113 }
 114
 115 static void thread_create(pthread_t *thread, pthread_attr_t *attr,
 116                           void *(*start_routine)(void*), void *arg)
 117 {
 118     int ret = pthread_create(thread, attr, start_routine, arg);
 119     if (ret) die2(ret, "pthread_create");
 120 }
 121
 122 static ssize_t handle_aiocb_ioctl(struct qemu_paiocb *aiocb)
 123 {
 124     int ret;
 125
 126     ret = ioctl(aiocb->aio_fildes, aiocb->aio_ioctl_cmd, aiocb->aio_ioctl_buf);
 127     if (ret == -1)
 128         return -errno;
 129
 130     /*
 131      * This looks weird, but the aio code only consideres a request
 132      * successful if it has written the number full number of bytes.
 133      *
 134      * Now we overload aio_nbytes as aio_ioctl_cmd for the ioctl command,
 135      * so in fact we return the ioctl command here to make posix_aio_read()
 136      * happy..
 137      */
 138     return aiocb->aio_nbytes;
 139 }
 140
 141 static ssize_t handle_aiocb_flush(struct qemu_paiocb *aiocb)
 142 {
 143     int ret;
 144
 145     ret = qemu_fdatasync(aiocb->aio_fildes);
 146     if (ret == -1)
 147         return -errno;
 148     return 0;
 149 }
 150
 151 #ifdef CONFIG_PREADV
 152
 153 static ssize_t
 154 qemu_preadv(int fd, const struct iovec *iov, int nr_iov, off_t offset)
 155 {
 156     return preadv(fd, iov, nr_iov, offset);
 157 }
 158
 159 static ssize_t
 160 qemu_pwritev(int fd, const struct iovec *iov, int nr_iov, off_t offset)
 161 {
 162     return pwritev(fd, iov, nr_iov, offset);
 163 }
 164
 165 #else
 166
 167 static ssize_t
 168 qemu_preadv(int fd, const struct iovec *iov, int nr_iov, off_t offset)
 169 {
 170     return -ENOSYS;
 171 }
 172
 173 static ssize_t
 174 qemu_pwritev(int fd, const struct iovec *iov, int nr_iov, off_t offset)
 175 {
 176     return -ENOSYS;
 177 }
 178
 179 #endif
 180
 181 static ssize_t handle_aiocb_rw_vector(struct qemu_paiocb *aiocb)
 182 {
 183     size_t offset = 0;
 184     ssize_t len;
 185
 186     do {
 187         if (aiocb->aio_type & QEMU_AIO_WRITE)
 188             len = qemu_pwritev(aiocb->aio_fildes,
 189                                aiocb->aio_iov,
 190                                aiocb->aio_niov,
 191                                aiocb->aio_offset + offset);
 192          else
 193             len = qemu_preadv(aiocb->aio_fildes,
 194                               aiocb->aio_iov,
 195                               aiocb->aio_niov,
 196                               aiocb->aio_offset + offset);
 197     } while (len == -1 && errno == EINTR);
 198
 199     if (len == -1)
 200         return -errno;
 201     return len;
 202 }
 203
 204 static ssize_t handle_aiocb_rw_linear(struct qemu_paiocb *aiocb, char *buf)
 205 {
 206     ssize_t offset = 0;
 207     ssize_t len;
 208
 209     while (offset < aiocb->aio_nbytes) {
 210          if (aiocb->aio_type & QEMU_AIO_WRITE)
 211              len = pwrite(aiocb->aio_fildes,
 212                           (const char *)buf + offset,
 213                           aiocb->aio_nbytes - offset,
 214                           aiocb->aio_offset + offset);
 215          else
 216              len = pread(aiocb->aio_fildes,
 217                          buf + offset,
 218                          aiocb->aio_nbytes - offset,
 219                          aiocb->aio_offset + offset);
 220
 221          if (len == -1 && errno == EINTR)
 222              continue;
 223          else if (len == -1) {
 224              offset = -errno;
 225              break;
 226          } else if (len == 0)
 227              break;
 228
 229          offset += len;
 230     }
 231
 232     return offset;
 233 }
 234
 235 static ssize_t handle_aiocb_rw(struct qemu_paiocb *aiocb)
 236 {
 237     ssize_t nbytes;
 238     char *buf;
 239
 240     if (!(aiocb->aio_type & QEMU_AIO_MISALIGNED)) {
 241         /*
 242          * If there is just a single buffer, and it is properly aligned
 243          * we can just use plain pread/pwrite without any problems.
 244          */
 245         if (aiocb->aio_niov == 1)
 246              return handle_aiocb_rw_linear(aiocb, aiocb->aio_iov->iov_base);
 247
 248         /*
 249          * We have more than one iovec, and all are properly aligned.
 250          *
 251          * Try preadv/pwritev first and fall back to linearizing the
 252          * buffer if it's not supported.
 253          */
 254         if (preadv_present) {
 255             nbytes = handle_aiocb_rw_vector(aiocb);
 256             if (nbytes == aiocb->aio_nbytes)
 257                 return nbytes;
 258             if (nbytes < 0 && nbytes != -ENOSYS)
 259                 return nbytes;
 260             preadv_present = 0;
 261         }
 262
 263         /*
 264          * XXX(hch): short read/write.  no easy way to handle the reminder
 265          * using these interfaces.  For now retry using plain
 266          * pread/pwrite?
 267          */
 268     }
 269
 270     /*
 271      * Ok, we have to do it the hard way, copy all segments into
 272      * a single aligned buffer.
 273      */
 274     buf = qemu_blockalign(aiocb->common.bs, aiocb->aio_nbytes);
 275     if (aiocb->aio_type & QEMU_AIO_WRITE) {
 276         char *p = buf;
 277         int i;
 278
 279         for (i = 0; i < aiocb->aio_niov; ++i) {
 280             memcpy(p, aiocb->aio_iov[i].iov_base, aiocb->aio_iov[i].iov_len);
 281             p += aiocb->aio_iov[i].iov_len;
 282         }
 283     }
 284
 285     nbytes = handle_aiocb_rw_linear(aiocb, buf);
 286     if (!(aiocb->aio_type & QEMU_AIO_WRITE)) {
 287         char *p = buf;
 288         size_t count = aiocb->aio_nbytes, copy;
 289         int i;
 290
 291         for (i = 0; i < aiocb->aio_niov && count; ++i) {
 292             copy = count;
 293             if (copy > aiocb->aio_iov[i].iov_len)
 294                 copy = aiocb->aio_iov[i].iov_len;
 295             memcpy(aiocb->aio_iov[i].iov_base, p, copy);
 296             p     += copy;
 297             count -= copy;
 298         }
 299     }
 300     qemu_vfree(buf);
 301
 302     return nbytes;
 303 }
 304
 305 static void *aio_thread(void *unused)
 306 {
 307     pid_t pid;
 308
 309     pid = getpid();
 310
 311     while (1) {
 312         struct qemu_paiocb *aiocb;
 313         ssize_t ret = 0;
 314         qemu_timeval tv;
 315         struct timespec ts;
 316
 317         qemu_gettimeofday(&tv);
 318         ts.tv_sec = tv.tv_sec + 10;
 319         ts.tv_nsec = 0;
 320
 321         mutex_lock(&lock);
 322
 323         while (QTAILQ_EMPTY(&request_list) &&
 324                !(ret == ETIMEDOUT)) {
 325             ret = cond_timedwait(&cond, &lock, &ts);
 326         }
 327
 328         if (QTAILQ_EMPTY(&request_list))
 329             break;
 330
 331         aiocb = QTAILQ_FIRST(&request_list);
 332         QTAILQ_REMOVE(&request_list, aiocb, node);
 333         aiocb->active = 1;
 334         idle_threads--;
 335         mutex_unlock(&lock);
 336
 337         switch (aiocb->aio_type & QEMU_AIO_TYPE_MASK) {
 338         case QEMU_AIO_READ:
 339         case QEMU_AIO_WRITE:
 340             ret = handle_aiocb_rw(aiocb);
 341             break;
 342         case QEMU_AIO_FLUSH:
 343             ret = handle_aiocb_flush(aiocb);
 344             break;
 345         case QEMU_AIO_IOCTL:
 346             ret = handle_aiocb_ioctl(aiocb);
 347             break;
 348         default:
 349             fprintf(stderr, "invalid aio request (0x%x)\n", aiocb->aio_type);
 350             ret = -EINVAL;
 351             break;
 352         }
 353
 354         mutex_lock(&lock);
 355         aiocb->ret = ret;
 356         idle_threads++;
 357         mutex_unlock(&lock);
 358
 359         if (kill(pid, aiocb->ev_signo)) die("kill failed");
 360     }
 361
 362     idle_threads--;
 363     cur_threads--;
 364     mutex_unlock(&lock);
 365
 366     return NULL;
 367 }
 368
 369 static void spawn_thread(void)
 370 {
 371     sigset_t set, oldset;
 372
 373     cur_threads++;
 374     idle_threads++;
 375
 376     /* block all signals */
 377     if (sigfillset(&set)) die("sigfillset");
 378     if (sigprocmask(SIG_SETMASK, &set, &oldset)) die("sigprocmask");
 379
 380     thread_create(&thread_id, &attr, aio_thread, NULL);
 381
 382     if (sigprocmask(SIG_SETMASK, &oldset, NULL)) die("sigprocmask restore");
 383 }
 384
 385 static void qemu_paio_submit(struct qemu_paiocb *aiocb)
 386 {
 387     aiocb->ret = -EINPROGRESS;
 388     aiocb->active = 0;
 389     mutex_lock(&lock);
 390     if (idle_threads == 0 && cur_threads < max_threads)
 391         spawn_thread();
 392     QTAILQ_INSERT_TAIL(&request_list, aiocb, node);
 393     mutex_unlock(&lock);
 394     cond_signal(&cond);
 395 }
 396
 397 static ssize_t qemu_paio_return(struct qemu_paiocb *aiocb)
 398 {
 399     ssize_t ret;
 400
 401     mutex_lock(&lock);
 402     ret = aiocb->ret;
 403     mutex_unlock(&lock);
 404
 405     return ret;
 406 }
 407
 408 static int qemu_paio_error(struct qemu_paiocb *aiocb)
 409 {
 410     ssize_t ret = qemu_paio_return(aiocb);
 411
 412     if (ret < 0)
 413         ret = -ret;
 414     else
 415         ret = 0;
 416
 417     return ret;
 418 }
 419
 420 static int posix_aio_process_queue(void *opaque)
 421 {
 422     PosixAioState *s = opaque;
 423     struct qemu_paiocb *acb, **pacb;
 424     int ret;
 425     int result = 0;
 426     int async_context_id = get_async_context_id();
 427
 428     for(;;) {
 429         pacb = &s->first_aio;
 430         for(;;) {
 431             acb = *pacb;
 432             if (!acb)
 433                 return result;
 434
 435             /* we're only interested in requests in the right context */
 436             if (acb->async_context_id != async_context_id) {
 437                 pacb = &acb->next;
 438                 continue;
 439             }
 440
 441             ret = qemu_paio_error(acb);
 442             if (ret == ECANCELED) {
 443                 /* remove the request */
 444                 *pacb = acb->next;
 445                 qemu_aio_release(acb);
 446                 result = 1;
 447             } else if (ret != EINPROGRESS) {
 448                 /* end of aio */
 449                 if (ret == 0) {
 450                     ret = qemu_paio_return(acb);
 451                     if (ret == acb->aio_nbytes)
 452                         ret = 0;
 453                     else
 454                         ret = -EINVAL;
 455                 } else {
 456                     ret = -ret;
 457                 }
 458                 /* remove the request */
 459                 *pacb = acb->next;
 460                 /* call the callback */
 461                 acb->common.cb(acb->common.opaque, ret);
 462                 qemu_aio_release(acb);
 463                 result = 1;
 464                 break;
 465             } else {
 466                 pacb = &acb->next;
 467             }
 468         }
 469     }
 470
 471     return result;
 472 }
 473
 474 static void posix_aio_read(void *opaque)
 475 {
 476     PosixAioState *s = opaque;
 477     ssize_t len;
 478
 479     /* read all bytes from signal pipe */
 480     for (;;) {
 481         char bytes[16];
 482
 483         len = read(s->rfd, bytes, sizeof(bytes));
 484         if (len == -1 && errno == EINTR)
 485             continue; /* try again */
 486         if (len == sizeof(bytes))
 487             continue; /* more to read */
 488         break;
 489     }
 490
 491     posix_aio_process_queue(s);
 492 }
 493
 494 static int posix_aio_flush(void *opaque)
 495 {
 496     PosixAioState *s = opaque;
 497     return !!s->first_aio;
 498 }
 499
 500 static PosixAioState *posix_aio_state;
 501
 502 static void aio_signal_handler(int signum)
 503 {
 504     if (posix_aio_state) {
 505         char byte = 0;
 506         ssize_t ret;
 507
 508         ret = write(posix_aio_state->wfd, &byte, sizeof(byte));
 509         if (ret < 0 && errno != EAGAIN)
 510             die("write()");
 511     }
 512
 513     qemu_service_io();
 514 }
 515
 516 static void paio_remove(struct qemu_paiocb *acb)
 517 {
 518     struct qemu_paiocb **pacb;
 519
 520     /* remove the callback from the queue */
 521     pacb = &posix_aio_state->first_aio;
 522     for(;;) {
 523         if (*pacb == NULL) {
 524             fprintf(stderr, "paio_remove: aio request not found!\n");
 525             break;
 526         } else if (*pacb == acb) {
 527             *pacb = acb->next;
 528             qemu_aio_release(acb);
 529             break;
 530         }
 531         pacb = &(*pacb)->next;
 532     }
 533 }
 534
 535 static void paio_cancel(BlockDriverAIOCB *blockacb)
 536 {
 537     struct qemu_paiocb *acb = (struct qemu_paiocb *)blockacb;
 538     int active = 0;
 539
 540     mutex_lock(&lock);
 541     if (!acb->active) {
 542         QTAILQ_REMOVE(&request_list, acb, node);
 543         acb->ret = -ECANCELED;
 544     } else if (acb->ret == -EINPROGRESS) {
 545         active = 1;
 546     }
 547     mutex_unlock(&lock);
 548
 549     if (active) {
 550         /* fail safe: if the aio could not be canceled, we wait for
 551            it */
 552         while (qemu_paio_error(acb) == EINPROGRESS)
 553             ;
 554     }
 555
 556     paio_remove(acb);
 557 }
 558
 559 static AIOPool raw_aio_pool = {
 560     .aiocb_size         = sizeof(struct qemu_paiocb),
 561     .cancel             = paio_cancel,
 562 };
 563
 564 BlockDriverAIOCB *paio_submit(BlockDriverState *bs, int fd,
 565         int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
 566         BlockDriverCompletionFunc *cb, void *opaque, int type)
 567 {
 568     struct qemu_paiocb *acb;
 569
 570     acb = qemu_aio_get(&raw_aio_pool, bs, cb, opaque);
 571     if (!acb)
 572         return NULL;
 573     acb->aio_type = type;
 574     acb->aio_fildes = fd;
 575     acb->ev_signo = SIGUSR2;
 576     acb->async_context_id = get_async_context_id();
 577
 578     if (qiov) {
 579         acb->aio_iov = qiov->iov;
 580         acb->aio_niov = qiov->niov;
 581     }
 582     acb->aio_nbytes = nb_sectors * 512;
 583     acb->aio_offset = sector_num * 512;
 584
 585     acb->next = posix_aio_state->first_aio;
 586     posix_aio_state->first_aio = acb;
 587
 588     trace_paio_submit(acb, opaque, sector_num, nb_sectors, type);
 589     qemu_paio_submit(acb);
 590     return &acb->common;
 591 }
 592
 593 BlockDriverAIOCB *paio_ioctl(BlockDriverState *bs, int fd,
 594         unsigned long int req, void *buf,
 595         BlockDriverCompletionFunc *cb, void *opaque)
 596 {
 597     struct qemu_paiocb *acb;
 598
 599     acb = qemu_aio_get(&raw_aio_pool, bs, cb, opaque);
 600     if (!acb)
 601         return NULL;
 602     acb->aio_type = QEMU_AIO_IOCTL;
 603     acb->aio_fildes = fd;
 604     acb->ev_signo = SIGUSR2;
 605     acb->async_context_id = get_async_context_id();
 606     acb->aio_offset = 0;
 607     acb->aio_ioctl_buf = buf;
 608     acb->aio_ioctl_cmd = req;
 609
 610     acb->next = posix_aio_state->first_aio;
 611     posix_aio_state->first_aio = acb;
 612
 613     qemu_paio_submit(acb);
 614     return &acb->common;
 615 }
 616
 617 int paio_init(void)
 618 {
 619     struct sigaction act;
 620     PosixAioState *s;
 621     int fds[2];
 622     int ret;
 623
 624     if (posix_aio_state)
 625         return 0;
 626
 627     s = qemu_malloc(sizeof(PosixAioState));
 628
 629     sigfillset(&act.sa_mask);
 630     act.sa_flags = 0; /* do not restart syscalls to interrupt select() */
 631     act.sa_handler = aio_signal_handler;
 632     sigaction(SIGUSR2, &act, NULL);
 633
 634     s->first_aio = NULL;
 635     if (qemu_pipe(fds) == -1) {
 636         fprintf(stderr, "failed to create pipe\n");
 637         return -1;
 638     }
 639
 640     s->rfd = fds[0];
 641     s->wfd = fds[1];
 642
 643     fcntl(s->rfd, F_SETFL, O_NONBLOCK);
 644     fcntl(s->wfd, F_SETFL, O_NONBLOCK);
 645
 646     qemu_aio_set_fd_handler(s->rfd, posix_aio_read, NULL, posix_aio_flush,
 647         posix_aio_process_queue, s);
 648
 649     ret = pthread_attr_init(&attr);
 650     if (ret)
 651         die2(ret, "pthread_attr_init");
 652
 653     ret = pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
 654     if (ret)
 655         die2(ret, "pthread_attr_setdetachstate");
 656
 657     QTAILQ_INIT(&request_list);
 658
 659     posix_aio_state = s;
 660     return 0;
 661 }