[Sheepdog] [PATCH 2/2] always delete data objects when deleting an cloned vdi

[MORITA Kazutaka]

At Fri, 04 May 2012 09:49:08 +0800,
levin li wrote:
> 
> On 05/04/2012 03:46 AM, MORITA Kazutaka wrote:
> > At Mon, 23 Apr 2012 14:18:06 +0800,
> > Li Wenpeng wrote:
> >> From: levin li<xingke.lwp at taobao.com>
> >>
> >> When deleting a cloned vdi, sheep find the root vdi and then
> >> traverse the vdi chain(such as base -->  snapshot -->  clone) to
> >> check wheter there's an undeleted vdi in the chain, if some vdi
> >> in the chain isn't deleted, sheep just mark the cloned vdi as
> >> deleted by clear its vdi name.
> >>
> >> But in fact a cloned vdi may created its own objects by copy-on-write,
> >> these objects can be deleted when deleting the vdi, so we make
> >> the cloned vdi to be deleted as the root vdi, then we can deleting
> >> its data objects, in delete_one() we check whether the object belongs
> >> to itself to determine whether to delete the object.
> >>
> >> Signed-off-by: levin li<xingke.lwp at taobao.com>
> >> ---
> >>   sheep/vdi.c |   14 ++++++++++++++
> >>   1 files changed, 14 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/sheep/vdi.c b/sheep/vdi.c
> >> index d2a522d..c8085c8 100644
> >> --- a/sheep/vdi.c
> >> +++ b/sheep/vdi.c
> >> @@ -478,6 +478,12 @@ static void delete_one(struct work *work)
> >>   		if (!inode->data_vdi_id[i])
> >>   			continue;
> >>
> >> +		if (inode->data_vdi_id[i] != inode->vdi_id) {
> >> +			dprintf("object %" PRIx64 " is base's data, would not be deleted.\n",
> >> +					vid_to_data_oid(inode->data_vdi_id[i], i));
> >> +			continue;
> >> +		}
> >> +
> >>   		ret = remove_object(dw->entries, dw->nr_vnodes, dw->nr_zones, dw->epoch,
> >>   			      vid_to_data_oid(inode->data_vdi_id[i], i),
> >>   			      inode->nr_copies);
> >> @@ -587,6 +593,14 @@ next:
> >>   			  vid_to_vdi_oid(vid), (char *)inode,
> >>   			  SD_INODE_HEADER_SIZE, 0, sys->nr_sobjs);
> >>
> >> +	if (vid == inode->vdi_id&&  inode->snap_id == 1
> > What does 'inode->snap_id == 1' mean here?  I think this patch is not
> > correct at all.
> >
> > Thanks,
> >
> > Kazutaka
> >
> When inode->snap_ctime is zero, it means this can not be a snapshot.
> 
> Further more, in the current vdi chain, the base vdi that we see by
> 'collie vdi list' has parent id which may point to the snapshot vdi 
> which is the previous base vdi, in the case that an snapshot exist, the 
> snap_id of the current base vdi must be greater than 1.
> 
> But the cloned vdi always has a snap_id to be 1, so we can determine that
> if inode->snap_id == 1 && inode->parent_vdi_id != 0 && 
> !inode->snap_ctime, then
> the vdi must be a cloned vdi.

For example:

 $ collie cluster format
 $ collie vdi create base 1G
 $ collie vdi snapshot base
 $ collie vdi clone base cloned
 $ collie vdi clone -s 1 base cloned
 $ collie vdi snapshot cloned
 $ collie vdi list
    Name        Id    Size    Used  Shared    Creation time   VDI id  Tag
  s base         1  1.0 GB  0.0 MB  0.0 MB 2012-05-07 03:50   54c278
    base         2  1.0 GB  0.0 MB  0.0 MB 2012-05-07 03:50   54c279
  s cloned       1  1.0 GB  0.0 MB  0.0 MB 2012-05-07 03:50   c876b2
    cloned       2  1.0 GB  0.0 MB  0.0 MB 2012-05-07 03:51   c876b3

The snap_id of the vdi c876b2 is 1, but its snap_ctime is not zero
because the vdi is a snapshot.  The snap_ctime of the vdi c876b3 is
zero, but its snap_is 2.  So, with your code, no vdi is detected as a
clonend vdi against the above example.

Kazutaka