Re: [Qemu-devel] [Qemu-block] [PATCH v2 2/3] block/parallals: Do not update header or truncate image when INMIGRATE

[Jeff Cody <jcody@redhat.com>]

On Mon, Nov 06, 2017 at 03:23:43PM -0500, Jeff Cody wrote:
> On Fri, Nov 03, 2017 at 02:08:13PM +0300, Denis V. Lunev wrote:
> > On 11/03/2017 02:05 PM, Stefan Hajnoczi wrote:
> > > On Mon, Oct 30, 2017 at 02:10:27PM +0100, Jeff Cody wrote:
> > >> If we write or modify the image file while the QEMU run state is
> > >> INMIGRATE, then the BDRV_O_INACTIVE BDS flag is set.  This will cause
> > >> an assert, since the image is marked inactive.  Make sure we obey this
> > >> flag.
> > >>
> > >> Signed-off-by: Jeff Cody <jcody@redhat.com>
> > >> ---
> > >>  block/parallels.c | 7 ++-----
> > >>  1 file changed, 2 insertions(+), 5 deletions(-)
> > >>
> > >> diff --git a/block/parallels.c b/block/parallels.c
> > >> index 2b6c6e5709..7b7a3efa1d 100644
> > >> --- a/block/parallels.c
> > >> +++ b/block/parallels.c
> > >> @@ -708,7 +708,7 @@ static int parallels_open(BlockDriverState *bs, QDict *options, int flags,
> > >>          s->prealloc_mode = PRL_PREALLOC_MODE_FALLOCATE;
> > >>      }
> > >>  
> > >> -    if (flags & BDRV_O_RDWR) {
> > >> +    if ((flags & BDRV_O_RDWR) && !(flags & BDRV_O_INACTIVE)) {
> > >>          s->header->inuse = cpu_to_le32(HEADER_INUSE_MAGIC);
> > >>          ret = parallels_update_header(bs);
> > >>          if (ret < 0) {
> > > Where do we ensure that HEADER_INUSE_MAGIC is set on the destination?
> > good point. it should be set in invalidate_cache following QCOW2 scheme.
> > Thus we should add that callback with this patch.
> > 
> 
> 
> Do we (intentionally) support migration with parallels?  I guess so, since
> it doesn't have migration blockers.

Hmm, I hit send prematurely...

Despite not having migration blockers, obviously nobody is using migration
with parallels; from v2.6.0 to now, attempting to do so causes QEMU to
assert due to the bug fixed in this patch.

Rather than implement .bdrv_invalidate_cache() in this series, I am going to
set a migration blocker in a separate patch (in this series), so that
migration is not supported.  Whenever .bdrv_invalidate_cache() is
implemented, then the blocker can be removed.

-Jeff