Re: [PATCH v10 04/12] migration/qemu-file: Add qemu_file_get_to_fd()

[Alex Williamson]

Hey Juan,

I think we're close, please ack this if it looks ok.  Thanks,

Alex

On Thu, 9 Feb 2023 21:20:35 +0200
Avihai Horon <avihaih@nvidia.com> wrote:

> Add new function qemu_file_get_to_fd() that allows reading data from
> QEMUFile and writing it straight into a given fd.
> 
> This will be used later in VFIO migration code.
> 
> Signed-off-by: Avihai Horon <avihaih@nvidia.com>
> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
> Reviewed-by: Cédric Le Goater <clg@redhat.com>
> ---
>  migration/qemu-file.h |  1 +
>  migration/qemu-file.c | 34 ++++++++++++++++++++++++++++++++++
>  2 files changed, 35 insertions(+)
> 
> diff --git a/migration/qemu-file.h b/migration/qemu-file.h
> index fa13d04d78..9d0155a2a1 100644
> --- a/migration/qemu-file.h
> +++ b/migration/qemu-file.h
> @@ -148,6 +148,7 @@ int qemu_file_shutdown(QEMUFile *f);
>  QEMUFile *qemu_file_get_return_path(QEMUFile *f);
>  void qemu_fflush(QEMUFile *f);
>  void qemu_file_set_blocking(QEMUFile *f, bool block);
> +int qemu_file_get_to_fd(QEMUFile *f, int fd, size_t size);
>  
>  void ram_control_before_iterate(QEMUFile *f, uint64_t flags);
>  void ram_control_after_iterate(QEMUFile *f, uint64_t flags);
> diff --git a/migration/qemu-file.c b/migration/qemu-file.c
> index 2d5f74ffc2..102ab3b439 100644
> --- a/migration/qemu-file.c
> +++ b/migration/qemu-file.c
> @@ -940,3 +940,37 @@ QIOChannel *qemu_file_get_ioc(QEMUFile *file)
>  {
>      return file->ioc;
>  }
> +
> +/*
> + * Read size bytes from QEMUFile f and write them to fd.
> + */
> +int qemu_file_get_to_fd(QEMUFile *f, int fd, size_t size)
> +{
> +    while (size) {
> +        size_t pending = f->buf_size - f->buf_index;
> +        ssize_t rc;
> +
> +        if (!pending) {
> +            rc = qemu_fill_buffer(f);
> +            if (rc < 0) {
> +                return rc;
> +            }
> +            if (rc == 0) {
> +                return -EIO;
> +            }
> +            continue;
> +        }
> +
> +        rc = write(fd, f->buf + f->buf_index, MIN(pending, size));
> +        if (rc < 0) {
> +            return -errno;
> +        }
> +        if (rc == 0) {
> +            return -EIO;
> +        }
> +        f->buf_index += rc;
> +        size -= rc;
> +    }
> +
> +    return 0;
> +}