Re: [Qemu-devel] [PATCH 1/4] migration: set f->is_write and flush in add_to_iovec

[Juan Quintela <quintela@redhat.com>]

Paolo Bonzini <pbonzini@redhat.com> wrote:
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  savevm.c | 25 +++++++++----------------
>  1 file changed, 9 insertions(+), 16 deletions(-)
>
> diff --git a/savevm.c b/savevm.c
> index b1d8988..c952c41 100644
> --- a/savevm.c
> +++ b/savevm.c
> @@ -631,6 +631,11 @@ static void add_to_iovec(QEMUFile *f, const uint8_t *buf, int size)
>          f->iov[f->iovcnt].iov_base = (uint8_t *)buf;
>          f->iov[f->iovcnt++].iov_len = size;
>      }
> +
> +    f->is_write = 1;
> +    if (f->buf_index >= IO_BUF_SIZE || f->iovcnt >= MAX_IOV_SIZE) {
> +        qemu_fflush(f);
> +    }
>  }
>  
>  void qemu_put_buffer_async(QEMUFile *f, const uint8_t *buf, int size)
> @@ -645,14 +650,8 @@ void qemu_put_buffer_async(QEMUFile *f, const uint8_t *buf, int size)
>          abort();
>      }
>  
> -    add_to_iovec(f, buf, size);
> -
> -    f->is_write = 1;
>      f->bytes_xfer += size;
> -
> -    if (f->buf_index >= IO_BUF_SIZE || f->iovcnt >= MAX_IOV_SIZE) {
> -        qemu_fflush(f);
> -    }
> +    add_to_iovec(f, buf, size);
>  }
>  
>  void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, int size)
> @@ -674,7 +673,6 @@ void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, int size)
>          if (l > size)
>              l = size;
>          memcpy(f->buf + f->buf_index, buf, l);
> -        f->is_write = 1;
>          f->buf_index += l;

we increase buf_index

>          qemu_put_buffer_async(f, f->buf + (f->buf_index - l), l);

and we call add_to_iovec() here inside.  Notice the torture to get the
old buf_index value.

>          if (qemu_file_get_error(f)) {
> @@ -697,15 +695,10 @@ void qemu_put_byte(QEMUFile *f, int v)
>          abort();
>      }
>  
> -    f->buf[f->buf_index++] = v;
> -    f->is_write = 1;
> +    f->buf[f->buf_index] = v;
>      f->bytes_xfer++;
> -
> -    add_to_iovec(f, f->buf + (f->buf_index - 1), 1);
> -
> -    if (f->buf_index >= IO_BUF_SIZE || f->iovcnt >= MAX_IOV_SIZE) {
> -        qemu_fflush(f);
> -    }
> +    add_to_iovec(f, f->buf + f->buf_index, 1);
> +    f->buf_index++;

And here,  we call add_to_iovec() and then increase buf_index

Is there any good reason for not being consistent?

Once there,  I think that moving the handling of buf_index to inside
add_to_iovec() looks like a good idea?

Later,  Juan.

>  }
>  
>  static void qemu_file_skip(QEMUFile *f, int size)