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