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Date: Thu, 21 Mar 2013 10:28:49 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [RFC 04/12] Add stdio_writev_buffer function
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To: Orit Wasserman <owasserm@redhat.com>
Cc: mst@redhat.com, chegu_vinod@hp.com, qemu-devel@nongnu.org, quintela@redhat.com

Il 21/03/2013 10:09, Orit Wasserman ha scritto:
> Signed-off-by: Orit Wasserman <owasserm@redhat.com>
> ---
>  savevm.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/savevm.c b/savevm.c
> index 41dc87f..fa07a86 100644
> --- a/savevm.c
> +++ b/savevm.c
> @@ -241,6 +241,11 @@ static int stdio_get_fd(void *opaque)
>      return fileno(s->stdio_file);
>  }
>  
> +static int stdio_writev_buffer(void *opaque, struct iovec *iov, int iovcnt)
> +{
> +    return iov_writev(stdio_get_fd(opaque), iov, iovcnt);
> +}
> +
>  static int stdio_put_buffer(void *opaque, const uint8_t *buf, int64_t pos, int size)
>  {
>      QEMUFileStdio *s = opaque;
> @@ -321,6 +326,7 @@ static const QEMUFileOps stdio_pipe_read_ops = {
>  static const QEMUFileOps stdio_pipe_write_ops = {
>      .get_fd =     stdio_get_fd,
>      .put_buffer = stdio_put_buffer,
> +    .writev_buffer = stdio_writev_buffer,
>      .close =      stdio_pclose
>  };
>  
> 

This may cause subtle bugs if the FILE* is written before opening the
QEMUFile, but not flushed.  It doesn't happen in QEMU, but it is not too
clean.  If you let qemu_fflush pick one of stdio_put_buffer or
stdio_writev_buffer, the problem disappears.

Paolo