Re: [PATCH 17/27] tools/libxl: Support converting a legacy stream to a v2 stream

[Ian Campbell <ian.campbell@citrix.com>]

On Mon, 2015-06-15 at 14:44 +0100, Andrew Cooper wrote:
> When a legacy stream is found, it needs to be converted to a v2 stream for the
> reading logic.  This is done by exec()ing the python conversion utility.
> 
> One complication is that the caller of this interface needs to assume
> ownership of the output fd, to prevent it being closed while still in use in a
> datacopier.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> CC: Ian Campbell <Ian.Campbell@citrix.com>
> CC: Ian Jackson <Ian.Jackson@eu.citrix.com>
> CC: Wei Liu <wei.liu2@citrix.com>
> ---
>  tools/libxl/Makefile                |    1 +
>  tools/libxl/libxl_convert_callout.c |  146 +++++++++++++++++++++++++++++++++++
>  tools/libxl/libxl_internal.h        |   32 ++++++++
>  3 files changed, 179 insertions(+)
>  create mode 100644 tools/libxl/libxl_convert_callout.c
> 
> diff --git a/tools/libxl/Makefile b/tools/libxl/Makefile
> index c71c5fe..ca0ae3e 100644
> --- a/tools/libxl/Makefile
> +++ b/tools/libxl/Makefile
> @@ -96,6 +96,7 @@ LIBXL_OBJS = flexarray.o libxl.o libxl_create.o libxl_dm.o libxl_pci.o \
>  			libxl_json.o libxl_aoutils.o libxl_numa.o libxl_vnuma.o \
>  			libxl_stream_read.o \
>  			libxl_save_callout.o _libxl_save_msgs_callout.o \
> +			libxl_convert_callout.o \

Could we arrange for this to be x86 only, please (both here while
compiling and at runtime)

>  			libxl_qmp.o libxl_event.o libxl_fork.o $(LIBXL_OBJS-y)
>  LIBXL_OBJS += libxl_genid.o
>  LIBXL_OBJS += _libxl_types.o libxl_flask.o _libxl_types_internal.o
> diff --git a/tools/libxl/libxl_convert_callout.c b/tools/libxl/libxl_convert_callout.c
> new file mode 100644
> index 0000000..9050bb9
> --- /dev/null
> +++ b/tools/libxl/libxl_convert_callout.c

> +
> +static void helper_failed(libxl__egc *egc,
> +                          libxl__conversion_helper_state *chs, int rc);
> +static void helper_exited(libxl__egc *egc, libxl__ev_child *ch,
> +                          pid_t pid, int status);
> +static void helper_done(libxl__egc *egc,
> +                        libxl__conversion_helper_state *chs);

A lot of this stuff looks a lot like the contents of
libxl_save_callout.c, is there no scope for sharing any of it?

Since we only support N->N+1 we could perhaps tolerate the duplication
if we agreed upon a reasonable schedule to remove all this compat stuff,
e.g. in 4.7 or 4.8.

Ian?