[lvm-devel] false error messages when merging

[Mike Snitzer]

On Mon, Feb 08 2010 at  5:03pm -0500,
Mike Snitzer <snitzer at redhat.com> wrote:

> On Mon, Feb 08 2010 at  4:29pm -0500,
> Mike Snitzer <snitzer at redhat.com> wrote:
> 
> > On Mon, Feb 08 2010 at  3:49pm -0500,
> > Mikulas Patocka <mpatocka at redhat.com> wrote:
> > 
> > > Hi
> > > 
> > > LVM2.2.02.60 writes false error messages about tree node not found when 
> > > activating delayed merging. But it starts merging anyway.
> > > 
> > > [slunicko:~]# lvs
> > >   LV   VG   Attr   LSize  Origin Snap%  Move Log Copy%  Convert
> > >   m    vg1  -wi-a- 16.00m
> > > [slunicko:~]# lvcreate -s -n s -c 4k -L 24M vg1/m
> > >   Logical volume "s" created
> > > [slunicko:~]# mount -t ext2 /dev/vg1/s /mnt/test
> > > [slunicko:~]# lvconvert --merge /dev/vg1/s
> > >   Can't merge when snapshot is open
> > >   Merging of snapshot s will start next activation.
> > > [slunicko:~]# umount /mnt/test
> > > [slunicko:~]# lvchange -an vg1/m
> > > [slunicko:~]# lvchange -ay vg1/m
> > >   failed to find tree node for m
> > >   failed to find tree node for s
> > > [slunicko:~]#
> > > ... the merging starts on backgound fine
> > 
> > I can reproduce your "failed to find tree node for" scenario using
> > the steps you provided.
> ...
> > All this being said, I'm not sure what's going on with your scenario but
> > I'll get to the bottom of it.
> 
> So this "failed to find tree node for" message was introduced with my
> optimization for not issuing more ioctls than is needed for checking
> open_count: http://sources.redhat.com/git/?p=lvm2.git;a=commit;h=1199b48c
> 
> I'll dig deeper to see what I can do about the noise.

The following patch eliminates the false error entirely.  I'm leaning
toward removing the message (rather than switch to log_debug()) because
it is valid (and expected) to not have a node in the tree (for both the
merging origin and the merging snapshot) in the case of when we're
activating a merging origin.

diff --git a/lib/activate/dev_manager.c b/lib/activate/dev_manager.c
index 6023574..6fbc392 100644
--- a/lib/activate/dev_manager.c
+++ b/lib/activate/dev_manager.c
@@ -264,10 +264,9 @@ static const struct dm_info *_cached_info(struct dm_pool *mem,
 		return NULL;
 	}
 
-	if (!(dnode = dm_tree_find_node_by_uuid(dtree, dlid))) {
-		log_error("failed to find tree node for %s", lv->name);
+	/* An activating merging origin won't have a node in the tree yet */
+	if (!(dnode = dm_tree_find_node_by_uuid(dtree, dlid)))
 		return NULL;
-	}
 
 	if (!(dinfo = dm_tree_node_get_info(dnode))) {
 		log_error("failed to get info from tree node for %s", lv->name);