[libvirt PATCH 10/30] qemu_block: change qemuBlockCommit to return job pointer

[Peter Krempa]

On Tue, Dec 13, 2022 at 10:06:41 +0100, Peter Krempa wrote:
> On Thu, Dec 08, 2022 at 14:30:46 +0100, Pavel Hrdina wrote:
> > The created job will be needed by external snapshot delete code so
> > rework qemuBlockCommit to return that pointer.
> > 
> > Signed-off-by: Pavel Hrdina <phrdina at redhat.com>
> > ---
> >  src/qemu/qemu_block.c  | 42 +++++++++++++++++++++++-------------------
> >  src/qemu/qemu_block.h  |  2 +-
> >  src/qemu/qemu_driver.c |  5 ++++-
> >  3 files changed, 28 insertions(+), 21 deletions(-)
> > 
> > diff --git a/src/qemu/qemu_block.c b/src/qemu/qemu_block.c
> > index 24c82377b0..0a0d942e71 100644
> > --- a/src/qemu/qemu_block.c
> > +++ b/src/qemu/qemu_block.c
> > @@ -3201,8 +3201,12 @@ qemuBlockExportAddNBD(virDomainObj *vm,
> >  /* The autofinalize argument controls if the qemu block job will be automatically
> >   * finalized. This is used when deleting external snapshots where we need to
> >   * disable automatic finalization for some use-case. The default value passed
> > - * to this argument should be VIR_TRISTATE_BOOL_YES.*/
> > -int
> > + * to this argument should be VIR_TRISTATE_BOOL_YES.
> > + *
> > + * Returns qemuBlockJobData pointer on success, NULL on error. Caller is responsible
> > + * to call virObjectUnref on the pointer.
> > + */
> 
> See, you are adding and adding to this but you didn't start off properly
> ;)
> 
> > +qemuBlockJobData *
> >  qemuBlockCommit(virDomainObj *vm,
> >                  virDomainDiskDef *disk,
> >                  virStorageSource *baseSource,
> 
> [...]
> 
> > @@ -3367,7 +3371,7 @@ qemuBlockCommit(virDomainObj *vm,
> >      }
> >      qemuBlockJobStarted(job, vm);
> >  
> > -    return 0;
> > +    return job;
> 
> [...]
> 
> >  
> >   error:
> >      if (clean_access) {
> 
> [...]
> 
> > diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> > index 12fca22616..53533062e1 100644
> > --- a/src/qemu/qemu_driver.c
> > +++ b/src/qemu/qemu_driver.c
> > @@ -14999,6 +14999,7 @@ qemuDomainBlockCommit(virDomainPtr dom,
> >      virStorageSource *topSource;
> >      virStorageSource *baseSource = NULL;
> >      virStorageSource *top_parent = NULL;
> > +    g_autoptr(qemuBlockJobData) job = NULL;
> 
> [2]
> 
> >  
> >      virCheckFlags(VIR_DOMAIN_BLOCK_COMMIT_SHALLOW |
> >                    VIR_DOMAIN_BLOCK_COMMIT_ACTIVE |
> > @@ -15030,9 +15031,11 @@ qemuDomainBlockCommit(virDomainPtr dom,
> >                                                          base, disk->dst, NULL)))
> >          goto endjob;
> >  
> > -    ret = qemuBlockCommit(vm, disk, baseSource, topSource, top_parent,
> > +    job = qemuBlockCommit(vm, disk, baseSource, topSource, top_parent,
> >                            bandwidth, VIR_ASYNC_JOB_NONE, VIR_TRISTATE_BOOL_YES,
> >                            flags);
> > +    if (job)
> > +        ret = 0;
> >  
> >   endjob:
> 
> 
> Okay so this somehow isn't adding up for me. Prior to this patch before
> you returned the job [1] there wasn't anything to unref it [2]. So how
> come it's now needed if you don't increase reference count?
> 
> Looking back at the refactoring patches moving the code out I think I
> see the problem there.
> 
> Either way qemuBlockJobStartupFinalize() is the proper function to call
> rather than automatically unref it.

Once you fix patch 2/30 to call qemuBlockJobStartupFinalize in both
cases, this patch will also need to call it directly to finalize the
job once the pointer is handed over. And I mean explicitly calling
qemuBlockJobStartupFinalize even in the success code path even when for
now it just unrefs the object.

With that change:

Reviewed-by: Peter Krempa <pkrempa at redhat.com>