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Sourcecode: fio version File versions

splice.c

/*
 * splice engine
 *
 * IO engine that transfers data by doing splices to/from pipes and
 * the files.
 *
 */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <assert.h>
#include <sys/poll.h>
#include <sys/mman.h>

#include "../fio.h"

#ifdef FIO_HAVE_SPLICE

struct spliceio_data {
      int pipe[2];
      int vmsplice_to_user;
      int vmsplice_to_user_map;
};

/*
 * vmsplice didn't use to support splicing to user space, this is the old
 * variant of getting that job done. Doesn't make a lot of sense, but it
 * uses splices to move data from the source into a pipe.
 */
static int fio_splice_read_old(struct thread_data *td, struct io_u *io_u)
{
      struct spliceio_data *sd = td->io_ops->data;
      struct fio_file *f = io_u->file;
      int ret, ret2, buflen;
      off_t offset;
      void *p;

      offset = io_u->offset;
      buflen = io_u->xfer_buflen;
      p = io_u->xfer_buf;
      while (buflen) {
            int this_len = buflen;

            if (this_len > SPLICE_DEF_SIZE)
                  this_len = SPLICE_DEF_SIZE;

            ret = splice(f->fd, &offset, sd->pipe[1], NULL, this_len, SPLICE_F_MORE);
            if (ret < 0) {
                  if (errno == ENODATA || errno == EAGAIN)
                        continue;

                  return -errno;
            }

            buflen -= ret;

            while (ret) {
                  ret2 = read(sd->pipe[0], p, ret);
                  if (ret2 < 0)
                        return -errno;

                  ret -= ret2;
                  p += ret2;
            }
      }

      return io_u->xfer_buflen;
}

/*
 * We can now vmsplice into userspace, so do the transfer by splicing into
 * a pipe and vmsplicing that into userspace.
 */
static int fio_splice_read(struct thread_data *td, struct io_u *io_u)
{
      struct spliceio_data *sd = td->io_ops->data;
      struct fio_file *f = io_u->file;
      struct iovec iov;
      int ret , buflen, mmap_len;
      off_t offset;
      void *p, *map;

      ret = 0;
      offset = io_u->offset;
      mmap_len = buflen = io_u->xfer_buflen;

      if (sd->vmsplice_to_user_map) {
            map = mmap(io_u->xfer_buf, buflen, PROT_READ, MAP_PRIVATE|OS_MAP_ANON, 0, 0);
            if (map == MAP_FAILED) {
                  td_verror(td, errno, "mmap io_u");
                  return -1;
            }

            p = map;
      } else {
            map = NULL;
            p = io_u->xfer_buf;
      }

      while (buflen) {
            int this_len = buflen;
            int flags = 0;

            if (this_len > SPLICE_DEF_SIZE) {
                  this_len = SPLICE_DEF_SIZE;
                  flags = SPLICE_F_MORE;
            }

            ret = splice(f->fd, &offset, sd->pipe[1], NULL, this_len,flags);
            if (ret < 0) {
                  if (errno == ENODATA || errno == EAGAIN)
                        continue;

                  td_verror(td, errno, "splice-from-fd");
                  break;
            }

            buflen -= ret;
            iov.iov_base = p;
            iov.iov_len = ret;

            while (iov.iov_len) {
                  ret = vmsplice(sd->pipe[0], &iov, 1, SPLICE_F_MOVE);
                  if (ret < 0) {
                        if (errno == EFAULT &&
                            sd->vmsplice_to_user_map) {
                              sd->vmsplice_to_user_map = 0;
                              munmap(map, mmap_len);
                              map = NULL;
                              p = io_u->xfer_buf;
                              iov.iov_base = p;
                              continue;
                        }
                        if (errno == EBADF) {
                              ret = -EBADF;
                              break;
                        }
                        td_verror(td, errno, "vmsplice");
                        break;
                  } else if (!ret) {
                        td_verror(td, ENODATA, "vmsplice");
                        ret = -1;
                        break;
                  }

                  iov.iov_len -= ret;
                  iov.iov_base += ret;
                  p += ret;
            }
            if (ret < 0)
                  break;
      }

      if (sd->vmsplice_to_user_map && munmap(map, mmap_len) < 0) {
            td_verror(td, errno, "munnap io_u");
            return -1;
      }
      if (ret < 0)
            return ret;

      return io_u->xfer_buflen;
}

/*
 * For splice writing, we can vmsplice our data buffer directly into a
 * pipe and then splice that to a file.
 */
static int fio_splice_write(struct thread_data *td, struct io_u *io_u)
{
      struct spliceio_data *sd = td->io_ops->data;
      struct iovec iov = {
            .iov_base = io_u->xfer_buf,
            .iov_len = io_u->xfer_buflen,
      };
      struct pollfd pfd = { .fd = sd->pipe[1], .events = POLLOUT, };
      struct fio_file *f = io_u->file;
      off_t off = io_u->offset;
      int ret, ret2;

      while (iov.iov_len) {
            if (poll(&pfd, 1, -1) < 0)
                  return errno;

            ret = vmsplice(sd->pipe[1], &iov, 1, SPLICE_F_NONBLOCK);
            if (ret < 0)
                  return -errno;

            iov.iov_len -= ret;
            iov.iov_base += ret;

            while (ret) {
                  ret2 = splice(sd->pipe[0], NULL, f->fd, &off, ret, 0);
                  if (ret2 < 0)
                        return -errno;

                  ret -= ret2;
            }
      }

      return io_u->xfer_buflen;
}

static int fio_spliceio_queue(struct thread_data *td, struct io_u *io_u)
{
      struct spliceio_data *sd = td->io_ops->data;
      int uninitialized_var(ret);

      fio_ro_check(td, io_u);

      if (io_u->ddir == DDIR_READ) {
            if (sd->vmsplice_to_user) {
                  ret = fio_splice_read(td, io_u);
                  /*
                   * This kernel doesn't support vmsplice to user
                   * space. Reset the vmsplice_to_user flag, so that
                   * we retry below and don't hit this path again.
                   */
                  if (ret == -EBADF)
                        sd->vmsplice_to_user = 0;
            }
            if (!sd->vmsplice_to_user)
                  ret = fio_splice_read_old(td, io_u);
      } else if (io_u->ddir == DDIR_WRITE)
            ret = fio_splice_write(td, io_u);
      else
            ret = fsync(io_u->file->fd);

      if (ret != (int) io_u->xfer_buflen) {
            if (ret >= 0) {
                  io_u->resid = io_u->xfer_buflen - ret;
                  io_u->error = 0;
                  return FIO_Q_COMPLETED;
            } else
                  io_u->error = errno;
      }

      if (io_u->error) {
            td_verror(td, io_u->error, "xfer");
            if (io_u->error == EINVAL)
                  log_err("fio: looks like splice doesn't work on this"
                              " file system\n");
      }

      return FIO_Q_COMPLETED;
}

static void fio_spliceio_cleanup(struct thread_data *td)
{
      struct spliceio_data *sd = td->io_ops->data;

      if (sd) {
            close(sd->pipe[0]);
            close(sd->pipe[1]);
            free(sd);
      }
}

static int fio_spliceio_init(struct thread_data *td)
{
      struct spliceio_data *sd = malloc(sizeof(*sd));

      if (pipe(sd->pipe) < 0) {
            td_verror(td, errno, "pipe");
            free(sd);
            return 1;
      }

      /*
       * Assume this work, we'll reset this if it doesn't
       */
      sd->vmsplice_to_user = 1;

      /*
       * Works with "real" vmsplice to user, eg mapping pages directly.
       * Reset if we fail.
       */
      sd->vmsplice_to_user_map = 1;

      /*
       * And if vmsplice_to_user works, we definitely need aligned
       * buffers. Just set ->odirect to force that.
       */
      if (td_read(td))
            td->o.odirect = 1;

      td->io_ops->data = sd;
      return 0;
}

static struct ioengine_ops ioengine = {
      .name       = "splice",
      .version    = FIO_IOOPS_VERSION,
      .init       = fio_spliceio_init,
      .queue            = fio_spliceio_queue,
      .cleanup    = fio_spliceio_cleanup,
      .open_file  = generic_open_file,
      .close_file = generic_close_file,
      .get_file_size    = generic_get_file_size,
      .flags            = FIO_SYNCIO | FIO_PIPEIO,
};

#else /* FIO_HAVE_SPLICE */

/*
 * When we have a proper configure system in place, we simply wont build
 * and install this io engine. For now install a crippled version that
 * just complains and fails to load.
 */
static int fio_spliceio_init(struct thread_data fio_unused *td)
{
      fprintf(stderr, "fio: splice not available\n");
      return 1;
}

static struct ioengine_ops ioengine = {
      .name       = "splice",
      .version    = FIO_IOOPS_VERSION,
      .init       = fio_spliceio_init,
};

#endif

static void fio_init fio_spliceio_register(void)
{
      register_ioengine(&ioengine);
}

static void fio_exit fio_spliceio_unregister(void)
{
      unregister_ioengine(&ioengine);
}

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