On 01/20/2015 06:41 AM, Ilya Dryomov wrote: > If the clone is resized down to 0, it becomes standalone. If such > resize is carried over while an image is mapped we would detect this > and call rbd_dev_parent_put() which means "let go of all parent state, > including the spec(s) of parent images(s)". This leads to a mismatch > between "rbd info" and sysfs parent fields, so a fix is in order. > > # rbd create --image-format 2 --size 1 foo > # rbd snap create foo@snap > # rbd snap protect foo@snap > # rbd clone foo@snap bar > # DEV=$(rbd map bar) > # rbd resize --allow-shrink --size 0 bar > # rbd resize --size 1 bar > # rbd info bar | grep parent > parent: rbd/foo@snap > > Before: > > # cat /sys/bus/rbd/devices/0/parent > (no parent image) > > After: > > # cat /sys/bus/rbd/devices/0/parent > pool_id 0 > pool_name rbd > image_id 10056b8b4567 > image_name foo > snap_id 2 > snap_name snap > overlap 0 > > Signed-off-by: Ilya Dryomov <[email protected]>
Hmm. Interesting. I think that a parent with an overlap of 0 is of no real use. So in the last patch I was suggesting it should just go away. But now, looking at it from this perspective, the fact that an image *came from* a particular parent, but which has no more overlap, could be useful information. The parent shouldn't simply go away without the user requesting that. I haven't completely followed through the logic of keeping the reference around but I understand what you're doing and it looks OK to me. Reviewed-by: Alex Elder <[email protected]> > --- > drivers/block/rbd.c | 30 ++++++++++-------------------- > 1 file changed, 10 insertions(+), 20 deletions(-) > > diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c > index b85d52005a21..e818c2a6ffb1 100644 > --- a/drivers/block/rbd.c > +++ b/drivers/block/rbd.c > @@ -4273,32 +4273,22 @@ static int rbd_dev_v2_parent_info(struct rbd_device > *rbd_dev) > } > > /* > - * We always update the parent overlap. If it's zero we > - * treat it specially. > + * We always update the parent overlap. If it's zero we issue > + * a warning, as we will proceed as if there was no parent. > */ > - rbd_dev->parent_overlap = overlap; > if (!overlap) { > - > - /* A null parent_spec indicates it's the initial probe */ > - > if (parent_spec) { > - /* > - * The overlap has become zero, so the clone > - * must have been resized down to 0 at some > - * point. Treat this the same as a flatten. > - */ > - rbd_dev_parent_put(rbd_dev); > - pr_info("%s: clone image now standalone\n", > - rbd_dev->disk->disk_name); > + /* refresh, careful to warn just once */ > + if (rbd_dev->parent_overlap) > + rbd_warn(rbd_dev, > + "clone now standalone (overlap became 0)"); > } else { > - /* > - * For the initial probe, if we find the > - * overlap is zero we just pretend there was > - * no parent image. > - */ > - rbd_warn(rbd_dev, "ignoring parent with overlap 0"); > + /* initial probe */ > + rbd_warn(rbd_dev, "clone is standalone (overlap 0)"); > } > } > + rbd_dev->parent_overlap = overlap; > + > out: > ret = 0; > out_err: > -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
