File:  [Qemu by Fabrice Bellard] / qemu / posix-aio-compat.c
Revision 1.1.1.5 (vendor branch): download - view: text, annotated - select for diffs
Tue Apr 24 18:33:41 2018 UTC (3 years, 1 month ago) by root
Branches: qemu, MAIN
CVS tags: qemu0150, qemu0141, qemu0140, HEAD
qemu 0.14.0

    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: }

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