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Re: [Qemu-devel] [PATCH v6 25/28] qmp/migration: new command migrate-rec
From: |
Peter Xu |
Subject: |
Re: [Qemu-devel] [PATCH v6 25/28] qmp/migration: new command migrate-recover |
Date: |
Wed, 14 Feb 2018 12:30:30 +0800 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
On Tue, Feb 13, 2018 at 06:56:51PM +0000, Dr. David Alan Gilbert wrote:
> * Peter Xu (address@hidden) wrote:
> > The first allow-oob=true command. It's used on destination side when
> > the postcopy migration is paused and ready for a recovery. After
> > execution, a new migration channel will be established for postcopy to
> > continue.
> >
> > Signed-off-by: Peter Xu <address@hidden>
> > ---
> > migration/migration.c | 26 ++++++++++++++++++++++++++
> > migration/migration.h | 1 +
> > migration/savevm.c | 3 +++
> > qapi/migration.json | 20 ++++++++++++++++++++
> > 4 files changed, 50 insertions(+)
> >
> > diff --git a/migration/migration.c b/migration/migration.c
> > index cf3a3f416c..bb57ed9ade 100644
> > --- a/migration/migration.c
> > +++ b/migration/migration.c
> > @@ -1422,6 +1422,32 @@ void qmp_migrate_incoming(const char *uri, Error
> > **errp)
> > once = false;
> > }
> >
> > +void qmp_migrate_recover(const char *uri, Error **errp)
> > +{
> > + MigrationIncomingState *mis = migration_incoming_get_current();
> > +
> > + if (mis->state != MIGRATION_STATUS_POSTCOPY_PAUSED) {
> > + error_setg(errp, "Migrate recover can only be run "
> > + "when postcopy is paused.");
> > + return;
> > + }
>
> OK, if it did come back as Paused I don't think it can leave it again
> except this way, so I'm not too worried it being thread safe.
>
> > + if (mis->postcopy_recover_triggered) {
> > + error_setg(errp, "Migrate recovery is triggered already");
> > + return;
> > + }
> > +
> > + /* This will make sure we'll only allow one recover for one pause */
> > + mis->postcopy_recover_triggered = true;
>
> However, does that need to be done with a :
> if (atomic_cmpxchg(mis->postcopy_recovery_triggered, false, true) ==
> true) {
> error_setg(errp, "Migrate recovery is triggered already");
> }
>
> for the slim chance that someone did this command on the main and the
> oob monitor?
Yes, slim chance, but I agree. :)
I wasn't that strict on this, but I should. Since we are at it, maybe
I'll also...
>
> Dave
>
> > + /*
> > + * Note that this call will never start a real migration; it will
> > + * only re-setup the migration stream and poke existing migration
> > + * to continue using that newly established channel.
> > + */
> > + qemu_start_incoming_migration(uri, errp);
> > +}
> > +
> > bool migration_is_blocked(Error **errp)
> > {
> > if (qemu_savevm_state_blocked(errp)) {
> > diff --git a/migration/migration.h b/migration/migration.h
> > index 88f5614b90..581bf4668b 100644
> > --- a/migration/migration.h
> > +++ b/migration/migration.h
> > @@ -65,6 +65,7 @@ struct MigrationIncomingState {
> > QemuSemaphore colo_incoming_sem;
> >
> > /* notify PAUSED postcopy incoming migrations to try to continue */
> > + bool postcopy_recover_triggered;
> > QemuSemaphore postcopy_pause_sem_dst;
> > QemuSemaphore postcopy_pause_sem_fault;
> > };
> > diff --git a/migration/savevm.c b/migration/savevm.c
> > index d40092a2b6..5f41b062ba 100644
> > --- a/migration/savevm.c
> > +++ b/migration/savevm.c
> > @@ -2182,6 +2182,9 @@ static bool
> > postcopy_pause_incoming(MigrationIncomingState *mis)
> > /* Notify the fault thread for the invalidated file handle */
> > postcopy_fault_thread_notify(mis);
> >
> > + /* Clear the triggered bit to allow one recovery */
> > + mis->postcopy_recover_triggered = false;
> > +
... move this set operation above migrate_set_state() since there can
also be a slim chance too that we may be handling migrate-recover even
before setting up postcopy_recover_triggered=false first.
Thanks,
--
Peter Xu
- [Qemu-devel] [PATCH v6 20/28] migration: synchronize dirty bitmap for resume, (continued)
[Qemu-devel] [PATCH v6 23/28] migration: init dst in migration_object_init too, Peter Xu, 2018/02/08
[Qemu-devel] [PATCH v6 22/28] migration: final handshake for the resume, Peter Xu, 2018/02/08
[Qemu-devel] [PATCH v6 25/28] qmp/migration: new command migrate-recover, Peter Xu, 2018/02/08
[Qemu-devel] [PATCH v6 24/28] io: let watcher of the channel run in same ctx, Peter Xu, 2018/02/08
[Qemu-devel] [PATCH v6 26/28] hmp/migration: add migrate_recover command, Peter Xu, 2018/02/08
[Qemu-devel] [PATCH v6 27/28] migration/qmp: add command migrate-pause, Peter Xu, 2018/02/08