Cédric Le Goater <c...@redhat.com> writes:
> This prepares ground for the changes coming next which add an Error**
> argument to the .save_setup() handler. Callers of qemu_savevm_state_setup()
> now handle the error and fail earlier setting the migration state from
> MIGRATION_STATUS_SETUP to MIGRATION_STATUS_FAILED.
>
> In qemu_savevm_state(), move the cleanup to preserve the error
> reported by .save_setup() handlers.
>
> Since the previous behavior was to ignore errors at this step of
> migration, this change should be examined closely to check that
> cleanups are still correctly done.
>
> Signed-off-by: Cédric Le Goater <c...@redhat.com>
> ---
>
> Changes in v4:
>
> - Merged cleanup change in qemu_savevm_state()
>
> Changes in v3:
>
> - Set migration state to MIGRATION_STATUS_FAILED
> - Fixed error handling to be done under lock in bg_migration_thread()
> - Made sure an error is always set in case of failure in
> qemu_savevm_state_setup()
>
> migration/savevm.h | 2 +-
> migration/migration.c | 27 ++++++++++++++++++++++++---
> migration/savevm.c | 26 +++++++++++++++-----------
> 3 files changed, 40 insertions(+), 15 deletions(-)
>
> diff --git a/migration/savevm.h b/migration/savevm.h
> index
> 74669733dd63a080b765866c703234a5c4939223..9ec96a995c93a42aad621595f0ed58596c532328
> 100644
> --- a/migration/savevm.h
> +++ b/migration/savevm.h
> @@ -32,7 +32,7 @@
> bool qemu_savevm_state_blocked(Error **errp);
> void qemu_savevm_non_migratable_list(strList **reasons);
> int qemu_savevm_state_prepare(Error **errp);
> -void qemu_savevm_state_setup(QEMUFile *f);
> +int qemu_savevm_state_setup(QEMUFile *f, Error **errp);
> bool qemu_savevm_state_guest_unplug_pending(void);
> int qemu_savevm_state_resume_prepare(MigrationState *s);
> void qemu_savevm_state_header(QEMUFile *f);
> diff --git a/migration/migration.c b/migration/migration.c
> index
> a49fcd53ee19df1ce0182bc99d7e064968f0317b..6d1544224e96f5edfe56939a9c8395d88ef29581
> 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -3408,6 +3408,8 @@ static void *migration_thread(void *opaque)
> int64_t setup_start = qemu_clock_get_ms(QEMU_CLOCK_HOST);
> MigThrError thr_error;
> bool urgent = false;
> + Error *local_err = NULL;
> + int ret;
>
> thread = migration_threads_add("live_migration", qemu_get_thread_id());
>
> @@ -3451,9 +3453,17 @@ static void *migration_thread(void *opaque)
> }
>
> bql_lock();
> - qemu_savevm_state_setup(s->to_dst_file);
> + ret = qemu_savevm_state_setup(s->to_dst_file, &local_err);
> bql_unlock();
>
> + if (ret) {
> + migrate_set_error(s, local_err);
> + error_free(local_err);
> + migrate_set_state(&s->state, MIGRATION_STATUS_SETUP,
> + MIGRATION_STATUS_FAILED);
> + goto out;
> + }
> +
> qemu_savevm_wait_unplug(s, MIGRATION_STATUS_SETUP,
> MIGRATION_STATUS_ACTIVE);
This^ should be before the new block it seems:
GOOD:
migrate_set_state new state setup
migrate_set_state new state wait-unplug
migrate_fd_cancel
migrate_set_state new state cancelling
migrate_fd_cleanup
migrate_set_state new state cancelled
migrate_fd_cancel
ok 1 /x86_64/failover-virtio-net/migrate/abort/wait-unplug
BAD:
migrate_set_state new state setup
migrate_fd_cancel
migrate_set_state new state cancelling
migrate_fd_cleanup
migrate_set_state new state cancelled
qemu-system-x86_64: ram_save_setup failed: Input/output error
**
ERROR:../tests/qtest/virtio-net-failover.c:1203:test_migrate_abort_wait_unplug:
assertion failed (status == "cancelling"): ("cancelled" == "cancelling")
Otherwise migration_iteration_finish() will schedule the cleanup BH and
that will run concurrently with migrate_fd_cancel() issued by the test
and bad things happens.
=====
PS: I guess the next level in our Freestyle Concurrency video-game is to
make migrate_fd_cancel() stop setting state and poking files and only
set a flag that's tested in the other parts of the code.
>
> @@ -3530,6 +3540,9 @@ static void *bg_migration_thread(void *opaque)
> MigThrError thr_error;
> QEMUFile *fb;
> bool early_fail = true;
> + bool setup_fail = true;
> + Error *local_err = NULL;
> + int ret;
>
> rcu_register_thread();
> object_ref(OBJECT(s));
> @@ -3563,9 +3576,16 @@ static void *bg_migration_thread(void *opaque)
>
> bql_lock();
> qemu_savevm_state_header(s->to_dst_file);
> - qemu_savevm_state_setup(s->to_dst_file);
> + ret = qemu_savevm_state_setup(s->to_dst_file, &local_err);
> + if (ret) {
> + migrate_set_error(s, local_err);
> + error_free(local_err);
> + goto fail;
> + }
> bql_unlock();
>
> + setup_fail = false;
> +
> qemu_savevm_wait_unplug(s, MIGRATION_STATUS_SETUP,
> MIGRATION_STATUS_ACTIVE);
>
> @@ -3632,7 +3652,8 @@ static void *bg_migration_thread(void *opaque)
>
> fail:
> if (early_fail) {
> - migrate_set_state(&s->state, MIGRATION_STATUS_ACTIVE,
> + migrate_set_state(&s->state,
> + setup_fail ? MIGRATION_STATUS_SETUP :
> MIGRATION_STATUS_ACTIVE,
> MIGRATION_STATUS_FAILED);
> bql_unlock();
> }
> diff --git a/migration/savevm.c b/migration/savevm.c
> index
> ee31ffb5e88cea723039c754c30ce2c8a0ef35f3..63fdbb5ad7d4dbfaef1d2094350bf302cc677602
> 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -1310,11 +1310,11 @@ int qemu_savevm_state_prepare(Error **errp)
> return 0;
> }
>
> -void qemu_savevm_state_setup(QEMUFile *f)
> +int qemu_savevm_state_setup(QEMUFile *f, Error **errp)
> {
> + ERRP_GUARD();
> MigrationState *ms = migrate_get_current();
> SaveStateEntry *se;
> - Error *local_err = NULL;
> int ret = 0;
>
> json_writer_int64(ms->vmdesc, "page_size", qemu_target_page_size());
> @@ -1323,10 +1323,9 @@ void qemu_savevm_state_setup(QEMUFile *f)
> trace_savevm_state_setup();
> QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
> if (se->vmsd && se->vmsd->early_setup) {
> - ret = vmstate_save(f, se, ms->vmdesc, &local_err);
> + ret = vmstate_save(f, se, ms->vmdesc, errp);
> if (ret) {
> - migrate_set_error(ms, local_err);
> - error_report_err(local_err);
> + migrate_set_error(ms, *errp);
> qemu_file_set_error(f, ret);
> break;
> }
> @@ -1346,18 +1345,19 @@ void qemu_savevm_state_setup(QEMUFile *f)
> ret = se->ops->save_setup(f, se->opaque);
> save_section_footer(f, se);
> if (ret < 0) {
> + error_setg(errp, "failed to setup SaveStateEntry with id(name): "
> + "%d(%s): %d", se->section_id, se->idstr, ret);
> qemu_file_set_error(f, ret);
> break;
> }
> }
>
> if (ret) {
> - return;
> + return ret;
> }
>
> - if (precopy_notify(PRECOPY_NOTIFY_SETUP, &local_err)) {
> - error_report_err(local_err);
> - }
> + /* TODO: Should we check that errp is set in case of failure ? */
> + return precopy_notify(PRECOPY_NOTIFY_SETUP, errp);
> }
>
> int qemu_savevm_state_resume_prepare(MigrationState *s)
> @@ -1728,7 +1728,10 @@ static int qemu_savevm_state(QEMUFile *f, Error **errp)
> ms->to_dst_file = f;
>
> qemu_savevm_state_header(f);
> - qemu_savevm_state_setup(f);
> + ret = qemu_savevm_state_setup(f, errp);
> + if (ret) {
> + goto cleanup;
> + }
>
> while (qemu_file_get_error(f) == 0) {
> if (qemu_savevm_state_iterate(f, false) > 0) {
> @@ -1741,10 +1744,11 @@ static int qemu_savevm_state(QEMUFile *f, Error
> **errp)
> qemu_savevm_state_complete_precopy(f, false, false);
> ret = qemu_file_get_error(f);
> }
> - qemu_savevm_state_cleanup();
> if (ret != 0) {
> error_setg_errno(errp, -ret, "Error while writing VM state");
> }
> +cleanup:
> + qemu_savevm_state_cleanup();
>
> if (ret != 0) {
> status = MIGRATION_STATUS_FAILED;
