Archipelago » qemu

/*

 * QEMU posix-aio emulation

 *

 * Copyright IBM, Corp. 2008

 *

 * Authors:

 *  Anthony Liguori   <aliguori@us.ibm.com>

 *

 * This work is licensed under the terms of the GNU GPL, version 2.  See

 * the COPYING file in the top-level directory.

 *

 */

#include <sys/ioctl.h>

#include <sys/types.h>

#include <pthread.h>

#include <unistd.h>

#include <errno.h>

#include <time.h>

#include <string.h>

#include <stdlib.h>

#include <stdio.h>

#include "qemu-queue.h"

#include "osdep.h"

#include "sysemu.h"

#include "qemu-common.h"

#include "trace.h"

#include "block_int.h"

#include "block/raw-posix-aio.h"

static void do_spawn_thread(void);

struct qemu_paiocb {

    BlockDriverAIOCB common;

    int aio_fildes;

    union {

        struct iovec *aio_iov;

        void *aio_ioctl_buf;

    };

    int aio_niov;

    size_t aio_nbytes;

#define aio_ioctl_cmd   aio_nbytes /* for QEMU_AIO_IOCTL */

    off_t aio_offset;

    QTAILQ_ENTRY(qemu_paiocb) node;

    int aio_type;

    ssize_t ret;

    int active;

    struct qemu_paiocb *next;

};

typedef struct PosixAioState {

    int rfd, wfd;

    struct qemu_paiocb *first_aio;

} PosixAioState;

static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;

static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;

static pthread_t thread_id;

static pthread_attr_t attr;

static int max_threads = 64;

static int cur_threads = 0;

static int idle_threads = 0;

static int new_threads = 0;     /* backlog of threads we need to create */

static int pending_threads = 0; /* threads created but not running yet */

static QEMUBH *new_thread_bh;

static QTAILQ_HEAD(, qemu_paiocb) request_list;

#ifdef CONFIG_PREADV

static int preadv_present = 1;

#else

static int preadv_present = 0;

#endif

static void die2(int err, const char *what)

{

    fprintf(stderr, "%s failed: %s\n", what, strerror(err));

    abort();

}

static void die(const char *what)

{

    die2(errno, what);

}

static void mutex_lock(pthread_mutex_t *mutex)

{

    int ret = pthread_mutex_lock(mutex);

    if (ret) die2(ret, "pthread_mutex_lock");

}

static void mutex_unlock(pthread_mutex_t *mutex)

{

    int ret = pthread_mutex_unlock(mutex);

    if (ret) die2(ret, "pthread_mutex_unlock");

}

static int cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,

                           struct timespec *ts)

{

    int ret = pthread_cond_timedwait(cond, mutex, ts);

    if (ret && ret != ETIMEDOUT) die2(ret, "pthread_cond_timedwait");

    return ret;

}

static void cond_signal(pthread_cond_t *cond)

{

    int ret = pthread_cond_signal(cond);

    if (ret) die2(ret, "pthread_cond_signal");

}

static void thread_create(pthread_t *thread, pthread_attr_t *attr,

                          void *(*start_routine)(void*), void *arg)

{

    int ret = pthread_create(thread, attr, start_routine, arg);

    if (ret) die2(ret, "pthread_create");

}

static ssize_t handle_aiocb_ioctl(struct qemu_paiocb *aiocb)

{

    int ret;

    ret = ioctl(aiocb->aio_fildes, aiocb->aio_ioctl_cmd, aiocb->aio_ioctl_buf);

    if (ret == -1)

        return -errno;

    /*

     * This looks weird, but the aio code only considers a request

     * successful if it has written the full number of bytes.

     *

     * Now we overload aio_nbytes as aio_ioctl_cmd for the ioctl command,

     * so in fact we return the ioctl command here to make posix_aio_read()

     * happy..

     */

    return aiocb->aio_nbytes;

}

static ssize_t handle_aiocb_flush(struct qemu_paiocb *aiocb)

{

    int ret;

    ret = qemu_fdatasync(aiocb->aio_fildes);

    if (ret == -1)

        return -errno;

    return 0;

}

#ifdef CONFIG_PREADV

static ssize_t

qemu_preadv(int fd, const struct iovec *iov, int nr_iov, off_t offset)

{

    return preadv(fd, iov, nr_iov, offset);

}

static ssize_t

qemu_pwritev(int fd, const struct iovec *iov, int nr_iov, off_t offset)

{

    return pwritev(fd, iov, nr_iov, offset);

}

#else

static ssize_t

qemu_preadv(int fd, const struct iovec *iov, int nr_iov, off_t offset)

{

    return -ENOSYS;

}

static ssize_t

qemu_pwritev(int fd, const struct iovec *iov, int nr_iov, off_t offset)

{

    return -ENOSYS;

}

#endif

static ssize_t handle_aiocb_rw_vector(struct qemu_paiocb *aiocb)

{

    ssize_t len;

    do {

        if (aiocb->aio_type & QEMU_AIO_WRITE)

            len = qemu_pwritev(aiocb->aio_fildes,

                               aiocb->aio_iov,

                               aiocb->aio_niov,

                               aiocb->aio_offset);

         else

            len = qemu_preadv(aiocb->aio_fildes,

                              aiocb->aio_iov,

                              aiocb->aio_niov,

                              aiocb->aio_offset);

    } while (len == -1 && errno == EINTR);

    if (len == -1)

        return -errno;

    return len;

}

/*

 * Read/writes the data to/from a given linear buffer.

 *

 * Returns the number of bytes handles or -errno in case of an error. Short

 * reads are only returned if the end of the file is reached.

 */

static ssize_t handle_aiocb_rw_linear(struct qemu_paiocb *aiocb, char *buf)

{

    ssize_t offset = 0;

    ssize_t len;

    while (offset < aiocb->aio_nbytes) {

         if (aiocb->aio_type & QEMU_AIO_WRITE)

             len = pwrite(aiocb->aio_fildes,

                          (const char *)buf + offset,

                          aiocb->aio_nbytes - offset,

                          aiocb->aio_offset + offset);

         else

             len = pread(aiocb->aio_fildes,

                         buf + offset,

                         aiocb->aio_nbytes - offset,

                         aiocb->aio_offset + offset);

         if (len == -1 && errno == EINTR)

             continue;

         else if (len == -1) {

             offset = -errno;

             break;

         } else if (len == 0)

             break;

         offset += len;

    }

    return offset;

}

static ssize_t handle_aiocb_rw(struct qemu_paiocb *aiocb)

{

    ssize_t nbytes;

    char *buf;

    if (!(aiocb->aio_type & QEMU_AIO_MISALIGNED)) {

        /*

         * If there is just a single buffer, and it is properly aligned

         * we can just use plain pread/pwrite without any problems.

         */

        if (aiocb->aio_niov == 1)

             return handle_aiocb_rw_linear(aiocb, aiocb->aio_iov->iov_base);

        /*

         * We have more than one iovec, and all are properly aligned.

         *

         * Try preadv/pwritev first and fall back to linearizing the

         * buffer if it's not supported.

         */

        if (preadv_present) {

            nbytes = handle_aiocb_rw_vector(aiocb);

            if (nbytes == aiocb->aio_nbytes)

                return nbytes;

            if (nbytes < 0 && nbytes != -ENOSYS)

                return nbytes;

            preadv_present = 0;

        }

        /*

         * XXX(hch): short read/write.  no easy way to handle the reminder

         * using these interfaces.  For now retry using plain

         * pread/pwrite?

         */

    }

    /*

     * Ok, we have to do it the hard way, copy all segments into

     * a single aligned buffer.

     */

    buf = qemu_blockalign(aiocb->common.bs, aiocb->aio_nbytes);

    if (aiocb->aio_type & QEMU_AIO_WRITE) {

        char *p = buf;

        int i;

        for (i = 0; i < aiocb->aio_niov; ++i) {

            memcpy(p, aiocb->aio_iov[i].iov_base, aiocb->aio_iov[i].iov_len);

            p += aiocb->aio_iov[i].iov_len;

        }

    }

    nbytes = handle_aiocb_rw_linear(aiocb, buf);

    if (!(aiocb->aio_type & QEMU_AIO_WRITE)) {

        char *p = buf;

        size_t count = aiocb->aio_nbytes, copy;

        int i;

        for (i = 0; i < aiocb->aio_niov && count; ++i) {

            copy = count;

            if (copy > aiocb->aio_iov[i].iov_len)

                copy = aiocb->aio_iov[i].iov_len;

            memcpy(aiocb->aio_iov[i].iov_base, p, copy);

            p     += copy;

            count -= copy;

        }

    }

    qemu_vfree(buf);

    return nbytes;

}

static void posix_aio_notify_event(void);

static void *aio_thread(void *unused)

{

    mutex_lock(&lock);

    pending_threads--;

    mutex_unlock(&lock);

    do_spawn_thread();

    while (1) {

        struct qemu_paiocb *aiocb;

        ssize_t ret = 0;

        qemu_timeval tv;

        struct timespec ts;

        qemu_gettimeofday(&tv);

        ts.tv_sec = tv.tv_sec + 10;

        ts.tv_nsec = 0;

        mutex_lock(&lock);

        while (QTAILQ_EMPTY(&request_list) &&

               !(ret == ETIMEDOUT)) {

            idle_threads++;

            ret = cond_timedwait(&cond, &lock, &ts);

            idle_threads--;

        }

        if (QTAILQ_EMPTY(&request_list))

            break;

        aiocb = QTAILQ_FIRST(&request_list);

        QTAILQ_REMOVE(&request_list, aiocb, node);

        aiocb->active = 1;

        mutex_unlock(&lock);

        switch (aiocb->aio_type & QEMU_AIO_TYPE_MASK) {

        case QEMU_AIO_READ:

            ret = handle_aiocb_rw(aiocb);

            if (ret >= 0 && ret < aiocb->aio_nbytes && aiocb->common.bs->growable) {

                /* A short read means that we have reached EOF. Pad the buffer

                 * with zeros for bytes after EOF. */

                QEMUIOVector qiov;

                qemu_iovec_init_external(&qiov, aiocb->aio_iov,

                                         aiocb->aio_niov);

                qemu_iovec_memset_skip(&qiov, 0, aiocb->aio_nbytes - ret, ret);

                ret = aiocb->aio_nbytes;

            }

            break;

        case QEMU_AIO_WRITE:

            ret = handle_aiocb_rw(aiocb);

            break;

        case QEMU_AIO_FLUSH:

            ret = handle_aiocb_flush(aiocb);

            break;

        case QEMU_AIO_IOCTL:

            ret = handle_aiocb_ioctl(aiocb);

            break;

        default:

            fprintf(stderr, "invalid aio request (0x%x)\n", aiocb->aio_type);

            ret = -EINVAL;

            break;

        }

        mutex_lock(&lock);

        aiocb->ret = ret;

        mutex_unlock(&lock);

        posix_aio_notify_event();

    }

    cur_threads--;

    mutex_unlock(&lock);

    return NULL;

}

static void do_spawn_thread(void)

{

    sigset_t set, oldset;

    mutex_lock(&lock);

    if (!new_threads) {

        mutex_unlock(&lock);

        return;

    }

    new_threads--;

    pending_threads++;

    mutex_unlock(&lock);

    /* block all signals */

    if (sigfillset(&set)) die("sigfillset");

    if (sigprocmask(SIG_SETMASK, &set, &oldset)) die("sigprocmask");

    thread_create(&thread_id, &attr, aio_thread, NULL);

    if (sigprocmask(SIG_SETMASK, &oldset, NULL)) die("sigprocmask restore");

}

static void spawn_thread_bh_fn(void *opaque)

{

    do_spawn_thread();

}

static void spawn_thread(void)

{

    cur_threads++;

    new_threads++;

    /* If there are threads being created, they will spawn new workers, so

     * we don't spend time creating many threads in a loop holding a mutex or

     * starving the current vcpu.

     *

     * If there are no idle threads, ask the main thread to create one, so we

     * inherit the correct affinity instead of the vcpu affinity.

     */

    if (!pending_threads) {

        qemu_bh_schedule(new_thread_bh);

    }

}

static void qemu_paio_submit(struct qemu_paiocb *aiocb)

{

    aiocb->ret = -EINPROGRESS;

    aiocb->active = 0;

    mutex_lock(&lock);

    if (idle_threads == 0 && cur_threads < max_threads)

        spawn_thread();

    QTAILQ_INSERT_TAIL(&request_list, aiocb, node);

    mutex_unlock(&lock);

    cond_signal(&cond);

}

static ssize_t qemu_paio_return(struct qemu_paiocb *aiocb)

{

    ssize_t ret;

    mutex_lock(&lock);

    ret = aiocb->ret;

    mutex_unlock(&lock);

    return ret;

}

static int qemu_paio_error(struct qemu_paiocb *aiocb)

{

    ssize_t ret = qemu_paio_return(aiocb);

    if (ret < 0)

        ret = -ret;

    else

        ret = 0;

    return ret;

}

static int posix_aio_process_queue(void *opaque)

{

    PosixAioState *s = opaque;

    struct qemu_paiocb *acb, **pacb;

    int ret;

    int result = 0;

    for(;;) {

        pacb = &s->first_aio;

        for(;;) {

            acb = *pacb;

            if (!acb)

                return result;

            ret = qemu_paio_error(acb);

            if (ret == ECANCELED) {

                /* remove the request */

                *pacb = acb->next;

                qemu_aio_release(acb);

                result = 1;

            } else if (ret != EINPROGRESS) {

                /* end of aio */

                if (ret == 0) {

                    ret = qemu_paio_return(acb);

                    if (ret == acb->aio_nbytes)

                        ret = 0;

                    else

                        ret = -EINVAL;

                } else {

                    ret = -ret;

                }

                trace_paio_complete(acb, acb->common.opaque, ret);

                /* remove the request */

                *pacb = acb->next;

                /* call the callback */

                acb->common.cb(acb->common.opaque, ret);

                qemu_aio_release(acb);

                result = 1;

                break;

            } else {

                pacb = &acb->next;

            }

        }

    }

    return result;

}

static void posix_aio_read(void *opaque)

{

    PosixAioState *s = opaque;

    ssize_t len;

    /* read all bytes from signal pipe */

    for (;;) {

        char bytes[16];

        len = read(s->rfd, bytes, sizeof(bytes));

        if (len == -1 && errno == EINTR)

            continue; /* try again */

        if (len == sizeof(bytes))

            continue; /* more to read */

        break;

    }

    posix_aio_process_queue(s);

}

static int posix_aio_flush(void *opaque)

{

    PosixAioState *s = opaque;

    return !!s->first_aio;

}

static PosixAioState *posix_aio_state;

static void posix_aio_notify_event(void)

{

    char byte = 0;

    ssize_t ret;

    ret = write(posix_aio_state->wfd, &byte, sizeof(byte));

    if (ret < 0 && errno != EAGAIN)

        die("write()");

}

static void paio_remove(struct qemu_paiocb *acb)

{

    struct qemu_paiocb **pacb;

    /* remove the callback from the queue */

    pacb = &posix_aio_state->first_aio;

    for(;;) {

        if (*pacb == NULL) {

            fprintf(stderr, "paio_remove: aio request not found!\n");

            break;

        } else if (*pacb == acb) {

            *pacb = acb->next;

            qemu_aio_release(acb);

            break;

        }

        pacb = &(*pacb)->next;

    }

}

static void paio_cancel(BlockDriverAIOCB *blockacb)

{

    struct qemu_paiocb *acb = (struct qemu_paiocb *)blockacb;

    int active = 0;

    trace_paio_cancel(acb, acb->common.opaque);

    mutex_lock(&lock);

    if (!acb->active) {

        QTAILQ_REMOVE(&request_list, acb, node);

        acb->ret = -ECANCELED;

    } else if (acb->ret == -EINPROGRESS) {

        active = 1;

    }

    mutex_unlock(&lock);

    if (active) {

        /* fail safe: if the aio could not be canceled, we wait for

           it */

        while (qemu_paio_error(acb) == EINPROGRESS)

            ;

    }

    paio_remove(acb);

}

static AIOPool raw_aio_pool = {

    .aiocb_size         = sizeof(struct qemu_paiocb),

    .cancel             = paio_cancel,

};

BlockDriverAIOCB *paio_submit(BlockDriverState *bs, int fd,

        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,

        BlockDriverCompletionFunc *cb, void *opaque, int type)

{

    struct qemu_paiocb *acb;

    acb = qemu_aio_get(&raw_aio_pool, bs, cb, opaque);

    if (!acb)

        return NULL;

    acb->aio_type = type;

    acb->aio_fildes = fd;

    if (qiov) {

        acb->aio_iov = qiov->iov;

        acb->aio_niov = qiov->niov;

    }

    acb->aio_nbytes = nb_sectors * 512;

    acb->aio_offset = sector_num * 512;

    acb->next = posix_aio_state->first_aio;

    posix_aio_state->first_aio = acb;

    trace_paio_submit(acb, opaque, sector_num, nb_sectors, type);

    qemu_paio_submit(acb);

    return &acb->common;

}

BlockDriverAIOCB *paio_ioctl(BlockDriverState *bs, int fd,

        unsigned long int req, void *buf,

        BlockDriverCompletionFunc *cb, void *opaque)

{

    struct qemu_paiocb *acb;

    acb = qemu_aio_get(&raw_aio_pool, bs, cb, opaque);

    if (!acb)

        return NULL;

    acb->aio_type = QEMU_AIO_IOCTL;

    acb->aio_fildes = fd;

    acb->aio_offset = 0;

    acb->aio_ioctl_buf = buf;

    acb->aio_ioctl_cmd = req;

    acb->next = posix_aio_state->first_aio;

    posix_aio_state->first_aio = acb;

    qemu_paio_submit(acb);

    return &acb->common;

}

int paio_init(void)

{

    PosixAioState *s;

    int fds[2];

    int ret;

    if (posix_aio_state)

        return 0;

    s = g_malloc(sizeof(PosixAioState));

    s->first_aio = NULL;

    if (qemu_pipe(fds) == -1) {

        fprintf(stderr, "failed to create pipe\n");

        g_free(s);

        return -1;

    }

    s->rfd = fds[0];

    s->wfd = fds[1];

    fcntl(s->rfd, F_SETFL, O_NONBLOCK);

    fcntl(s->wfd, F_SETFL, O_NONBLOCK);

    qemu_aio_set_fd_handler(s->rfd, posix_aio_read, NULL, posix_aio_flush,

        posix_aio_process_queue, s);

    ret = pthread_attr_init(&attr);

    if (ret)

        die2(ret, "pthread_attr_init");

    ret = pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);

    if (ret)

        die2(ret, "pthread_attr_setdetachstate");

    QTAILQ_INIT(&request_list);

    new_thread_bh = qemu_bh_new(spawn_thread_bh_fn, NULL);

    posix_aio_state = s;

    return 0;

}