On 10/10/18 1:37 PM, Aaron Lindsay wrote:
> In some cases it may be helpful to modify state before saving it for
> migration, and then modify the state back after it has been saved. The
> existing pre_save function provides half of this functionality. This
> patch adds a post_save function to provide the second half.
>
> Signed-off-by: Aaron Lindsay <aclin...@gmail.com>
> ---
> docs/devel/migration.rst | 9 +++++++--
> include/migration/vmstate.h | 1 +
> migration/vmstate.c | 10 +++++++++-
> 3 files changed, 17 insertions(+), 3 deletions(-)
Hmm, maybe. I believe the common practice is for pre_save to copy state into a
separate member on the side, so that conversion back isn't necessary.
Ccing in the migration maintainers for a second opinion.
r~
>
> diff --git a/docs/devel/migration.rst b/docs/devel/migration.rst
> index 687570754d..2a2533c9b3 100644
> --- a/docs/devel/migration.rst
> +++ b/docs/devel/migration.rst
> @@ -419,8 +419,13 @@ The functions to do that are inside a vmstate
> definition, and are called:
>
> This function is called before we save the state of one device.
>
> -Example: You can look at hpet.c, that uses the three function to
> -massage the state that is transferred.
> +- ``void (*post_save)(void *opaque);``
> +
> + This function is called after we save the state of one device
> + (even upon failure, unless the call to pre_save returned and error).
> +
> +Example: You can look at hpet.c, that uses the first three functions
> +to massage the state that is transferred.
>
> The ``VMSTATE_WITH_TMP`` macro may be useful when the migration
> data doesn't match the stored device data well; it allows an
> diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
> index 2b501d0466..f6053b94e4 100644
> --- a/include/migration/vmstate.h
> +++ b/include/migration/vmstate.h
> @@ -185,6 +185,7 @@ struct VMStateDescription {
> int (*pre_load)(void *opaque);
> int (*post_load)(void *opaque, int version_id);
> int (*pre_save)(void *opaque);
> + void (*post_save)(void *opaque);
> bool (*needed)(void *opaque);
> VMStateField *fields;
> const VMStateDescription **subsections;
> diff --git a/migration/vmstate.c b/migration/vmstate.c
> index 0bc240a317..9afc9298f3 100644
> --- a/migration/vmstate.c
> +++ b/migration/vmstate.c
> @@ -387,6 +387,9 @@ int vmstate_save_state_v(QEMUFile *f, const
> VMStateDescription *vmsd,
> if (ret) {
> error_report("Save of field %s/%s failed",
> vmsd->name, field->name);
> + if (vmsd->post_save) {
> + vmsd->post_save(opaque);
> + }
> return ret;
> }
>
> @@ -412,7 +415,12 @@ int vmstate_save_state_v(QEMUFile *f, const
> VMStateDescription *vmsd,
> json_end_array(vmdesc);
> }
>
> - return vmstate_subsection_save(f, vmsd, opaque, vmdesc);
> + ret = vmstate_subsection_save(f, vmsd, opaque, vmdesc);
> +
> + if (vmsd->post_save) {
> + vmsd->post_save(opaque);
> + }
> + return ret;
> }
>
> static const VMStateDescription *
>
