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 <string.h>
  21 #include <stdlib.h>
  22 #include <stdio.h>
  23
  24 #include "qemu-queue.h"
  25 #include "osdep.h"
  26 #include "sysemu.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 static void do_spawn_thread(void);
  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     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
  54 typedef struct PosixAioState {
  55     int rfd, wfd;
  56     struct qemu_paiocb *first_aio;
  57 } PosixAioState;
  58
  59
  60 static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
  61 static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
  62 static pthread_t thread_id;
  63 static pthread_attr_t attr;
  64 static int max_threads = 64;
  65 static int cur_threads = 0;
  66 static int idle_threads = 0;
  67 static int new_threads = 0;     /* backlog of threads we need to create */
  68 static int pending_threads = 0; /* threads created but not running yet */
  69 static QEMUBH *new_thread_bh;
  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     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);
 191          else
 192             len = qemu_preadv(aiocb->aio_fildes,
 193                               aiocb->aio_iov,
 194                               aiocb->aio_niov,
 195                               aiocb->aio_offset);
 196     } while (len == -1 && errno == EINTR);
 197
 198     if (len == -1)
 199         return -errno;
 200     return len;
 201 }
 202
 203 /*
 204  * Read/writes the data to/from a given linear buffer.
 205  *
 206  * Returns the number of bytes handles or -errno in case of an error. Short
 207  * reads are only returned if the end of the file is reached.
 208  */
 209 static ssize_t handle_aiocb_rw_linear(struct qemu_paiocb *aiocb, char *buf)
 210 {
 211     ssize_t offset = 0;
 212     ssize_t len;
 213
 214     while (offset < aiocb->aio_nbytes) {
 215          if (aiocb->aio_type & QEMU_AIO_WRITE)
 216              len = pwrite(aiocb->aio_fildes,
 217                           (const char *)buf + offset,
 218                           aiocb->aio_nbytes - offset,
 219                           aiocb->aio_offset + offset);
 220          else
 221              len = pread(aiocb->aio_fildes,
 222                          buf + offset,
 223                          aiocb->aio_nbytes - offset,
 224                          aiocb->aio_offset + offset);
 225
 226          if (len == -1 && errno == EINTR)
 227              continue;
 228          else if (len == -1) {
 229              offset = -errno;
 230              break;
 231          } else if (len == 0)
 232              break;
 233
 234          offset += len;
 235     }
 236
 237     return offset;
 238 }
 239
 240 static ssize_t handle_aiocb_rw(struct qemu_paiocb *aiocb)
 241 {
 242     ssize_t nbytes;
 243     char *buf;
 244
 245     if (!(aiocb->aio_type & QEMU_AIO_MISALIGNED)) {
 246         /*
 247          * If there is just a single buffer, and it is properly aligned
 248          * we can just use plain pread/pwrite without any problems.
 249          */
 250         if (aiocb->aio_niov == 1)
 251              return handle_aiocb_rw_linear(aiocb, aiocb->aio_iov->iov_base);
 252
 253         /*
 254          * We have more than one iovec, and all are properly aligned.
 255          *
 256          * Try preadv/pwritev first and fall back to linearizing the
 257          * buffer if it's not supported.
 258          */
 259         if (preadv_present) {
 260             nbytes = handle_aiocb_rw_vector(aiocb);
 261             if (nbytes == aiocb->aio_nbytes)
 262                 return nbytes;
 263             if (nbytes < 0 && nbytes != -ENOSYS)
 264                 return nbytes;
 265             preadv_present = 0;
 266         }
 267
 268         /*
 269          * XXX(hch): short read/write.  no easy way to handle the reminder
 270          * using these interfaces.  For now retry using plain
 271          * pread/pwrite?
 272          */
 273     }
 274
 275     /*
 276      * Ok, we have to do it the hard way, copy all segments into
 277      * a single aligned buffer.
 278      */
 279     buf = qemu_blockalign(aiocb->common.bs, aiocb->aio_nbytes);
 280     if (aiocb->aio_type & QEMU_AIO_WRITE) {
 281         char *p = buf;
 282         int i;
 283
 284         for (i = 0; i < aiocb->aio_niov; ++i) {
 285             memcpy(p, aiocb->aio_iov[i].iov_base, aiocb->aio_iov[i].iov_len);
 286             p += aiocb->aio_iov[i].iov_len;
 287         }
 288     }
 289
 290     nbytes = handle_aiocb_rw_linear(aiocb, buf);
 291     if (!(aiocb->aio_type & QEMU_AIO_WRITE)) {
 292         char *p = buf;
 293         size_t count = aiocb->aio_nbytes, copy;
 294         int i;
 295
 296         for (i = 0; i < aiocb->aio_niov && count; ++i) {
 297             copy = count;
 298             if (copy > aiocb->aio_iov[i].iov_len)
 299                 copy = aiocb->aio_iov[i].iov_len;
 300             memcpy(aiocb->aio_iov[i].iov_base, p, copy);
 301             p     += copy;
 302             count -= copy;
 303         }
 304     }
 305     qemu_vfree(buf);
 306
 307     return nbytes;
 308 }
 309
 310 static void posix_aio_notify_event(void);
 311
 312 static void *aio_thread(void *unused)
 313 {
 314     mutex_lock(&lock);
 315     pending_threads--;
 316     mutex_unlock(&lock);
 317     do_spawn_thread();
 318
 319     while (1) {
 320         struct qemu_paiocb *aiocb;
 321         ssize_t ret = 0;
 322         qemu_timeval tv;
 323         struct timespec ts;
 324
 325         qemu_gettimeofday(&tv);
 326         ts.tv_sec = tv.tv_sec + 10;
 327         ts.tv_nsec = 0;
 328
 329         mutex_lock(&lock);
 330
 331         while (QTAILQ_EMPTY(&request_list) &&
 332                !(ret == ETIMEDOUT)) {
 333             idle_threads++;
 334             ret = cond_timedwait(&cond, &lock, &ts);
 335             idle_threads--;
 336         }
 337
 338         if (QTAILQ_EMPTY(&request_list))
 339             break;
 340
 341         aiocb = QTAILQ_FIRST(&request_list);
 342         QTAILQ_REMOVE(&request_list, aiocb, node);
 343         aiocb->active = 1;
 344         mutex_unlock(&lock);
 345
 346         switch (aiocb->aio_type & QEMU_AIO_TYPE_MASK) {
 347         case QEMU_AIO_READ:
 348             ret = handle_aiocb_rw(aiocb);
 349             if (ret >= 0 && ret < aiocb->aio_nbytes && aiocb->common.bs->growable) {
 350                 /* A short read means that we have reached EOF. Pad the buffer
 351                  * with zeros for bytes after EOF. */
 352                 QEMUIOVector qiov;
 353
 354                 qemu_iovec_init_external(&qiov, aiocb->aio_iov,
 355                                          aiocb->aio_niov);
 356                 qemu_iovec_memset_skip(&qiov, 0, aiocb->aio_nbytes - ret, ret);
 357
 358                 ret = aiocb->aio_nbytes;
 359             }
 360             break;
 361         case QEMU_AIO_WRITE:
 362             ret = handle_aiocb_rw(aiocb);
 363             break;
 364         case QEMU_AIO_FLUSH:
 365             ret = handle_aiocb_flush(aiocb);
 366             break;
 367         case QEMU_AIO_IOCTL:
 368             ret = handle_aiocb_ioctl(aiocb);
 369             break;
 370         default:
 371             fprintf(stderr, "invalid aio request (0x%x)\n", aiocb->aio_type);
 372             ret = -EINVAL;
 373             break;
 374         }
 375
 376         mutex_lock(&lock);
 377         aiocb->ret = ret;
 378         mutex_unlock(&lock);
 379
 380         posix_aio_notify_event();
 381     }
 382
 383     cur_threads--;
 384     mutex_unlock(&lock);
 385
 386     return NULL;
 387 }
 388
 389 static void do_spawn_thread(void)
 390 {
 391     sigset_t set, oldset;
 392
 393     mutex_lock(&lock);
 394     if (!new_threads) {
 395         mutex_unlock(&lock);
 396         return;
 397     }
 398
 399     new_threads--;
 400     pending_threads++;
 401
 402     mutex_unlock(&lock);
 403
 404     /* block all signals */
 405     if (sigfillset(&set)) die("sigfillset");
 406     if (sigprocmask(SIG_SETMASK, &set, &oldset)) die("sigprocmask");
 407
 408     thread_create(&thread_id, &attr, aio_thread, NULL);
 409
 410     if (sigprocmask(SIG_SETMASK, &oldset, NULL)) die("sigprocmask restore");
 411 }
 412
 413 static void spawn_thread_bh_fn(void *opaque)
 414 {
 415     do_spawn_thread();
 416 }
 417
 418 static void spawn_thread(void)
 419 {
 420     cur_threads++;
 421     new_threads++;
 422     /* If there are threads being created, they will spawn new workers, so
 423      * we don't spend time creating many threads in a loop holding a mutex or
 424      * starving the current vcpu.
 425      *
 426      * If there are no idle threads, ask the main thread to create one, so we
 427      * inherit the correct affinity instead of the vcpu affinity.
 428      */
 429     if (!pending_threads) {
 430         qemu_bh_schedule(new_thread_bh);
 431     }
 432 }
 433
 434 static void qemu_paio_submit(struct qemu_paiocb *aiocb)
 435 {
 436     aiocb->ret = -EINPROGRESS;
 437     aiocb->active = 0;
 438     mutex_lock(&lock);
 439     if (idle_threads == 0 && cur_threads < max_threads)
 440         spawn_thread();
 441     QTAILQ_INSERT_TAIL(&request_list, aiocb, node);
 442     mutex_unlock(&lock);
 443     cond_signal(&cond);
 444 }
 445
 446 static ssize_t qemu_paio_return(struct qemu_paiocb *aiocb)
 447 {
 448     ssize_t ret;
 449
 450     mutex_lock(&lock);
 451     ret = aiocb->ret;
 452     mutex_unlock(&lock);
 453
 454     return ret;
 455 }
 456
 457 static int qemu_paio_error(struct qemu_paiocb *aiocb)
 458 {
 459     ssize_t ret = qemu_paio_return(aiocb);
 460
 461     if (ret < 0)
 462         ret = -ret;
 463     else
 464         ret = 0;
 465
 466     return ret;
 467 }
 468
 469 static int posix_aio_process_queue(void *opaque)
 470 {
 471     PosixAioState *s = opaque;
 472     struct qemu_paiocb *acb, **pacb;
 473     int ret;
 474     int result = 0;
 475
 476     for(;;) {
 477         pacb = &s->first_aio;
 478         for(;;) {
 479             acb = *pacb;
 480             if (!acb)
 481                 return result;
 482
 483             ret = qemu_paio_error(acb);
 484             if (ret == ECANCELED) {
 485                 /* remove the request */
 486                 *pacb = acb->next;
 487                 qemu_aio_release(acb);
 488                 result = 1;
 489             } else if (ret != EINPROGRESS) {
 490                 /* end of aio */
 491                 if (ret == 0) {
 492                     ret = qemu_paio_return(acb);
 493                     if (ret == acb->aio_nbytes)
 494                         ret = 0;
 495                     else
 496                         ret = -EINVAL;
 497                 } else {
 498                     ret = -ret;
 499                 }
 500
 501                 trace_paio_complete(acb, acb->common.opaque, ret);
 502
 503                 /* remove the request */
 504                 *pacb = acb->next;
 505                 /* call the callback */
 506                 acb->common.cb(acb->common.opaque, ret);
 507                 qemu_aio_release(acb);
 508                 result = 1;
 509                 break;
 510             } else {
 511                 pacb = &acb->next;
 512             }
 513         }
 514     }
 515
 516     return result;
 517 }
 518
 519 static void posix_aio_read(void *opaque)
 520 {
 521     PosixAioState *s = opaque;
 522     ssize_t len;
 523
 524     /* read all bytes from signal pipe */
 525     for (;;) {
 526         char bytes[16];
 527
 528         len = read(s->rfd, bytes, sizeof(bytes));
 529         if (len == -1 && errno == EINTR)
 530             continue; /* try again */
 531         if (len == sizeof(bytes))
 532             continue; /* more to read */
 533         break;
 534     }
 535
 536     posix_aio_process_queue(s);
 537 }
 538
 539 static int posix_aio_flush(void *opaque)
 540 {
 541     PosixAioState *s = opaque;
 542     return !!s->first_aio;
 543 }
 544
 545 static PosixAioState *posix_aio_state;
 546
 547 static void posix_aio_notify_event(void)
 548 {
 549     char byte = 0;
 550     ssize_t ret;
 551
 552     ret = write(posix_aio_state->wfd, &byte, sizeof(byte));
 553     if (ret < 0 && errno != EAGAIN)
 554         die("write()");
 555 }
 556
 557 static void paio_remove(struct qemu_paiocb *acb)
 558 {
 559     struct qemu_paiocb **pacb;
 560
 561     /* remove the callback from the queue */
 562     pacb = &posix_aio_state->first_aio;
 563     for(;;) {
 564         if (*pacb == NULL) {
 565             fprintf(stderr, "paio_remove: aio request not found!\n");
 566             break;
 567         } else if (*pacb == acb) {
 568             *pacb = acb->next;
 569             qemu_aio_release(acb);
 570             break;
 571         }
 572         pacb = &(*pacb)->next;
 573     }
 574 }
 575
 576 static void paio_cancel(BlockDriverAIOCB *blockacb)
 577 {
 578     struct qemu_paiocb *acb = (struct qemu_paiocb *)blockacb;
 579     int active = 0;
 580
 581     trace_paio_cancel(acb, acb->common.opaque);
 582
 583     mutex_lock(&lock);
 584     if (!acb->active) {
 585         QTAILQ_REMOVE(&request_list, acb, node);
 586         acb->ret = -ECANCELED;
 587     } else if (acb->ret == -EINPROGRESS) {
 588         active = 1;
 589     }
 590     mutex_unlock(&lock);
 591
 592     if (active) {
 593         /* fail safe: if the aio could not be canceled, we wait for
 594            it */
 595         while (qemu_paio_error(acb) == EINPROGRESS)
 596             ;
 597     }
 598
 599     paio_remove(acb);
 600 }
 601
 602 static AIOPool raw_aio_pool = {
 603     .aiocb_size         = sizeof(struct qemu_paiocb),
 604     .cancel             = paio_cancel,
 605 };
 606
 607 BlockDriverAIOCB *paio_submit(BlockDriverState *bs, int fd,
 608         int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
 609         BlockDriverCompletionFunc *cb, void *opaque, int type)
 610 {
 611     struct qemu_paiocb *acb;
 612
 613     acb = qemu_aio_get(&raw_aio_pool, bs, cb, opaque);
 614     if (!acb)
 615         return NULL;
 616     acb->aio_type = type;
 617     acb->aio_fildes = fd;
 618
 619     if (qiov) {
 620         acb->aio_iov = qiov->iov;
 621         acb->aio_niov = qiov->niov;
 622     }
 623     acb->aio_nbytes = nb_sectors * 512;
 624     acb->aio_offset = sector_num * 512;
 625
 626     acb->next = posix_aio_state->first_aio;
 627     posix_aio_state->first_aio = acb;
 628
 629     trace_paio_submit(acb, opaque, sector_num, nb_sectors, type);
 630     qemu_paio_submit(acb);
 631     return &acb->common;
 632 }
 633
 634 BlockDriverAIOCB *paio_ioctl(BlockDriverState *bs, int fd,
 635         unsigned long int req, void *buf,
 636         BlockDriverCompletionFunc *cb, void *opaque)
 637 {
 638     struct qemu_paiocb *acb;
 639
 640     acb = qemu_aio_get(&raw_aio_pool, bs, cb, opaque);
 641     if (!acb)
 642         return NULL;
 643     acb->aio_type = QEMU_AIO_IOCTL;
 644     acb->aio_fildes = fd;
 645     acb->aio_offset = 0;
 646     acb->aio_ioctl_buf = buf;
 647     acb->aio_ioctl_cmd = req;
 648
 649     acb->next = posix_aio_state->first_aio;
 650     posix_aio_state->first_aio = acb;
 651
 652     qemu_paio_submit(acb);
 653     return &acb->common;
 654 }
 655
 656 int paio_init(void)
 657 {
 658     PosixAioState *s;
 659     int fds[2];
 660     int ret;
 661
 662     if (posix_aio_state)
 663         return 0;
 664
 665     s = g_malloc(sizeof(PosixAioState));
 666
 667     s->first_aio = NULL;
 668     if (qemu_pipe(fds) == -1) {
 669         fprintf(stderr, "failed to create pipe\n");
 670         g_free(s);
 671         return -1;
 672     }
 673
 674     s->rfd = fds[0];
 675     s->wfd = fds[1];
 676
 677     fcntl(s->rfd, F_SETFL, O_NONBLOCK);
 678     fcntl(s->wfd, F_SETFL, O_NONBLOCK);
 679
 680     qemu_aio_set_fd_handler(s->rfd, posix_aio_read, NULL, posix_aio_flush,
 681         posix_aio_process_queue, s);
 682
 683     ret = pthread_attr_init(&attr);
 684     if (ret)
 685         die2(ret, "pthread_attr_init");
 686
 687     ret = pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
 688     if (ret)
 689         die2(ret, "pthread_attr_setdetachstate");
 690
 691     QTAILQ_INIT(&request_list);
 692     new_thread_bh = qemu_bh_new(spawn_thread_bh_fn, NULL);
 693
 694     posix_aio_state = s;
 695     return 0;
 696 }