Vladimir Sementsov-Ogievskiy <[email protected]> writes:
> All other handlers now have _errp() variants. Should we go this way
> for .post_save()? Actually it's rather strange, when the vmstate do
> successful preparations in .pre_save(), then successfully save all
> sections and subsections, end then fail when all the state is
> successfully transferred to the target.
>
> Happily, we have only three .post_save() realizations, all always
> successful. Let's make this a rule.
>
> Also note, that we call .post_save() in two places, and handle
> its (theoretical) failure inconsistently. Fix that too.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <[email protected]>
> ---
> docs/devel/migration/main.rst | 2 +-
> hw/ppc/spapr_pci.c | 3 +--
> include/migration/vmstate.h | 10 +++++++++-
> migration/savevm.c | 3 +--
> migration/vmstate.c | 12 +++---------
> target/arm/machine.c | 4 +---
> 6 files changed, 16 insertions(+), 18 deletions(-)
>
> diff --git a/docs/devel/migration/main.rst b/docs/devel/migration/main.rst
> index 234d280249..2de7050764 100644
> --- a/docs/devel/migration/main.rst
> +++ b/docs/devel/migration/main.rst
> @@ -439,7 +439,7 @@ 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.
>
> -- ``int (*post_save)(void *opaque);``
> +- ``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 an error).
> diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> index ea998bdff1..1dc3b02659 100644
> --- a/hw/ppc/spapr_pci.c
> +++ b/hw/ppc/spapr_pci.c
> @@ -2093,14 +2093,13 @@ static int spapr_pci_pre_save(void *opaque)
> return 0;
> }
>
> -static int spapr_pci_post_save(void *opaque)
> +static void spapr_pci_post_save(void *opaque)
> {
> SpaprPhbState *sphb = opaque;
>
> g_free(sphb->msi_devs);
> sphb->msi_devs = NULL;
> sphb->msi_devs_num = 0;
> - return 0;
> }
>
> static int spapr_pci_post_load(void *opaque, int version_id)
> diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
> index 3695afd483..15578b3e28 100644
> --- a/include/migration/vmstate.h
> +++ b/include/migration/vmstate.h
> @@ -223,7 +223,15 @@ struct VMStateDescription {
> bool (*post_load_errp)(void *opaque, int version_id, Error **errp);
> int (*pre_save)(void *opaque);
> bool (*pre_save_errp)(void *opaque, Error **errp);
> - int (*post_save)(void *opaque);
> +
> + /*
> + * post_save() rarely used to free some temporary resources.
> + * It's is called if .pre_save[_errp]() call was successful
> + * (or .pre_save[_errp] handler absent), regardless success
> + * or failure during fields and subsections save. If
> + * .pre_save[_errp]() fails, .post_save() is not called.
> + */
I would not mention usage directly and maybe also simplify the language
a bit. If there's doubt on the exact flow, people can read the code:
/*
* Unless .pre_save() fails, post_save() is called after saving
* fields and subsections. It should not fail because at this point
* the state has potentially already been transferred.
*/
> + void (*post_save)(void *opaque);
> bool (*needed)(void *opaque);
> bool (*dev_unplug_pending)(void *opaque);
>
> diff --git a/migration/savevm.c b/migration/savevm.c
> index 3a16c467b2..c5236e71ba 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -321,14 +321,13 @@ static int configuration_pre_save(void *opaque)
> return 0;
> }
>
> -static int configuration_post_save(void *opaque)
> +static void configuration_post_save(void *opaque)
> {
> SaveState *state = opaque;
>
> g_free(state->capabilities);
> state->capabilities = NULL;
> state->caps_count = 0;
> - return 0;
> }
>
> static int configuration_pre_load(void *opaque)
> diff --git a/migration/vmstate.c b/migration/vmstate.c
> index 651c3fe011..5111e7a141 100644
> --- a/migration/vmstate.c
> +++ b/migration/vmstate.c
> @@ -550,10 +550,7 @@ static int vmstate_save_state_v(QEMUFile *f, const
> VMStateDescription *vmsd,
> if (ret) {
> error_prepend(errp, "Save of field %s/%s failed: ",
> vmsd->name, field->name);
> - if (vmsd->post_save) {
> - vmsd->post_save(opaque);
> - }
> - return ret;
> + goto out;
> }
>
> /* Compressed arrays only care about the first element */
> @@ -578,12 +575,9 @@ static int vmstate_save_state_v(QEMUFile *f, const
> VMStateDescription *vmsd,
>
> ret = vmstate_subsection_save(f, vmsd, opaque, vmdesc, errp);
>
> +out:
> if (vmsd->post_save) {
> - int ps_ret = vmsd->post_save(opaque);
> - if (!ret && ps_ret) {
> - ret = ps_ret;
> - error_setg(errp, "post-save failed: %s", vmsd->name);
> - }
> + vmsd->post_save(opaque);
Nice cleanup.
> }
> return ret;
> }
> diff --git a/target/arm/machine.c b/target/arm/machine.c
> index bbaae34449..de810220e2 100644
> --- a/target/arm/machine.c
> +++ b/target/arm/machine.c
> @@ -993,15 +993,13 @@ static int cpu_pre_save(void *opaque)
> return 0;
> }
>
> -static int cpu_post_save(void *opaque)
> +static void cpu_post_save(void *opaque)
> {
> ARMCPU *cpu = opaque;
>
> if (!kvm_enabled()) {
> pmu_op_finish(&cpu->env);
> }
> -
> - return 0;
> }
>
> static int cpu_pre_load(void *opaque)
