Re: [PATCH 1/4] qemu-file: Don't do IO after shutdown

[Juan Quintela <quintela@redhat.com>]

"Dr. David Alan Gilbert" <dgilbert@redhat.com> wrote:
> * Dr. David Alan Gilbert (dgilbert@redhat.com) wrote:
>> * Juan Quintela (quintela@redhat.com) wrote:
>> > Be sure that we are not doing neither read/write after shutdown of the
>> > QEMUFile.
>> > 
>> > Signed-off-by: Juan Quintela <quintela@redhat.com>
>> > ---
>> >  migration/qemu-file.c | 13 +++++++++++++
>> >  1 file changed, 13 insertions(+)
>> > 
>> > diff --git a/migration/qemu-file.c b/migration/qemu-file.c
>> > index 26fb25ddc1..1e5543a279 100644
>> > --- a/migration/qemu-file.c
>> > +++ b/migration/qemu-file.c
>> > @@ -53,6 +53,8 @@ struct QEMUFile {
>> >  
>> >      int last_error;
>> >      Error *last_error_obj;
>> > +    /* has the file has been shutdown */
>> > +    bool shutdown;
>> >  };
>> >  
>> >  /*
>> > @@ -61,6 +63,7 @@ struct QEMUFile {
>> >   */
>> >  int qemu_file_shutdown(QEMUFile *f)
>> >  {
>> > +    f->shutdown = true;
>> >      if (!f->ops->shut_down) {
>> >          return -ENOSYS;
>> >      }
>> > @@ -214,6 +217,9 @@ void qemu_fflush(QEMUFile *f)
>> >          return;
>> >      }
>> >  
>> > +    if (f->shutdown) {
>> > +        return;
>> > +    }
>> 
>> OK, I did wonder if you need to free the iovec.
>> 
>> >      if (f->iovcnt > 0) {
>> >          expect = iov_size(f->iov, f->iovcnt);
>> >          ret = f->ops->writev_buffer(f->opaque, f->iov, f->iovcnt, f->pos,
>> > @@ -328,6 +334,10 @@ static ssize_t qemu_fill_buffer(QEMUFile *f)
>> >      f->buf_index = 0;
>> >      f->buf_size = pending;
>> >  
>> > +    if (f->shutdown) {
>> > +        return 0;
>> > +    }
>> 
>> I also wondered if perhaps an error would be reasonable here; but I'm
>> not sure what a read(2) does after a shutdown(2).
>> 
>> Still,
>> 
>> 
>> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>
> Actually, it turns out this breaks an assumption - 'shutdown' must cause
> reads/writes/etc to fail and for the qemu_file to go into error state.
> There's a few places we loop doing IO until we either change migration
> state or the file goes into error.
>
>
> diff --git a/migration/qemu-file.c b/migration/qemu-file.c
> index 1e5543a279..bbb2b63927 100644
> --- a/migration/qemu-file.c
> +++ b/migration/qemu-file.c
> @@ -63,11 +63,18 @@ struct QEMUFile {
>   */
>  int qemu_file_shutdown(QEMUFile *f)
>  {
> +    int ret;
> +
>      f->shutdown = true;
>      if (!f->ops->shut_down) {
>          return -ENOSYS;
>      }
> -    return f->ops->shut_down(f->opaque, true, true, NULL);
> +    ret = f->ops->shut_down(f->opaque, true, true, NULL);
> +
> +    if (!f->last_error) {
> +        qemu_file_set_error(f, -EIO);
> +    }
> +    return ret;
>  }
>  
>  /*
>
>
> seems to fix it for me.

will gve it a try later.

Thanks.