Re: [libvirt] [PATCH v3 REBASE 03/16] qemu: introduce QEMU_DOMAIN_JOB_STATUS_POSTCOPY
On 28.08.2017 17:55, Jiri Denemark wrote:
On Thu, Aug 24, 2017 at 09:56:40 +0300, Nikolay Shirokovskiy wrote:
> Current code consults job.current->stats.status to check for postcopy
> state. First it is more correct to check for both job.current->status
> and job.current->stats.status.code because on some paths on failures
> we change only the former. Second if qemu supports migration events
> then stats can change unexpectedly.
I'm not sure I understand what you're trying to say. Could you explain
this a bit more?
This place looks dangerous to me:
@@ -3836,7 +3840,7 @@ qemuMigrationRun(virQEMUDriverPtr driver,
else if (rc == -1)
goto cleanup;
- if (priv->job.current->stats.status == QEMU_MONITOR_MIGRATION_STATUS_POSTCOPY)
+ if (priv->job.current->status == QEMU_DOMAIN_JOB_STATUS_POSTCOPY)
inPostCopy = true;
It makes decisions based on current state of migration and consult stats.status for
this purpose. Such a check can be mistaken because in the code above this hunk if error
occurs we change only current->status
value. Also after patch 6 we can update stats.status during fetching migrations
stats but not change current->status.
However in a more detail analysis it looks like this code do not have undesired
effects and only look dangerous (at least to me). So I guess I'd better say it is
easier
to reason about if we have postcopy as one of the status states.
> Let's introduce QEMU_DOMAIN_JOB_STATUS_POSTCOPY state for
job.current->status.
>
> This patch removes all state checking usage of stats except for
> qemuDomainGetJobStatsInternal. This place will be handled separately.
> ---
> src/qemu/qemu_domain.c | 1 +
> src/qemu/qemu_domain.h | 1 +
> src/qemu/qemu_driver.c | 5 +++--
> src/qemu/qemu_migration.c | 18 +++++++++++-------
> src/qemu/qemu_process.c | 4 ++--
> 5 files changed, 18 insertions(+), 11 deletions(-)
ACK
Jirka