Re: [Qemu-devel] [PATCH 1/3] migration: Allow ram_save_cleanup to be called with empty state

[Fam Zheng <famz@redhat.com>]

On Fri, 09/15 14:56, Peter Xu wrote:
> On Fri, Sep 15, 2017 at 02:49:07PM +0800, Fam Zheng wrote:
> > On Fri, 09/15 14:41, Peter Xu wrote:
> > > On Fri, Sep 15, 2017 at 01:44:02PM +0800, Fam Zheng wrote:
> > > > So that we can do cleanup unconditionally at the end of main().
> > > > 
> > > > Signed-off-by: Fam Zheng <famz@redhat.com>
> > > > ---
> > > >  migration/ram.c | 3 +++
> > > >  1 file changed, 3 insertions(+)
> > > > 
> > > > diff --git a/migration/ram.c b/migration/ram.c
> > > > index e18b3e2d4f..37e6a71241 100644
> > > > --- a/migration/ram.c
> > > > +++ b/migration/ram.c
> > > > @@ -1365,6 +1365,9 @@ static void ram_save_cleanup(void *opaque)
> > > >      RAMState **rsp = opaque;
> > > >      RAMBlock *block;
> > > >  
> > > > +    if (!rsp || !*rsp) {
> > > > +        return;
> > > > +    }
> > > >      /* caller have hold iothread lock or is in a bh, so there is
> > > >       * no writing race against this migration_bitmap
> > > >       */
> > > > -- 
> > > > 2.13.5
> > > > 
> > > 
> > > Instead of take special care on RAM, how about check in
> > > migrate_fd_cancel(), and return directly if migration_is_idle()?
> > 
> > This is not from migrate_fd_cancel(), but from qemu_savevm_state_cleanup(), so
> > that doesn't work.
> 
> Yeh I see the point.  But my logic still stands - we don't need to
> cleanup anything if the migration is not really there.
> 
> I'm thinking whether we can put qemu_savevm_state_cleanup() into
> migrate_fd_cancel() in some way, though I am still not 100% sure on
> the colo part.  Anyway, I feel like a bit confusing we have two
> cleanup functions.

I agree, but I don't know what is the best way to clean this up: savevm and
migration seem a little independent from each other.

Fam