OpenNebula

Ceph image loses recent changes if image has been non persitent.

Steps to reproduce:

1) create persitent empty datablock (id 42), mount it in vm and add some files:

mkfs.ext4 /dev/vdb
mkdir /mnt/d1
mount /dev/vdb /mnt/d1/; cd /mnt/d1/; touch test1; touch test2; touch test3

Verify in ceph cluster: rbd -p one --id libvirt du

NAME         PROVISIONED    USED
one-42             1024M  73728k

2) terminate vm

3) make image none persitent & boot vm with it

Verify in ceph cluster: rbd -p one --id libvirt du

NAME         PROVISIONED    USED
one-42@snap        1024M 73728k <-- snapshot of original
one-42             1024M      0 <-- original image
one-42-623-1       1024M      0 <-- new vm none persitent image, child of snapshot

4) so far all ok with created files, terminate vm

Verify in ceph cluster: rbd -p one --id libvirt du

NAME         PROVISIONED    USED
one-42@snap        1024M 73728k <-- snapshot of original still present 
one-42             1024M      0

5) make image presitent again and boot vm with it. remove some files:

rm test2 test3

Verify in ceph cluster: rbd -p one --id libvirt du

NAME         PROVISIONED    USED
one-42@snap        1024M 73728k <-- old snapshot of original (with 3 files)
one-42             1024M 12288k <-- running presistent image (now with 1 file)

6) terminate vm and make image non persitent

7) boot new vm with image that had 1 file, and list dir: ls -al /mnt/d1

drwxr-xr-x  3 root root  4096 Oct 23 16:10 .
drwxr-xr-x 22 root root  4096 Oct  5 21:50 ..
drwx------  2 root root 16384 Oct 23 16:08 lost+found
-rw-r--r--  1 root root     0 Oct 23 16:10 test1
-rw-r--r--  1 root root     0 Oct 23 16:10 *test2* <-- deleted file in step 5
-rw-r--r--  1 root root     0 Oct 23 16:10 *test3* <-- deleted file in step 5

Verify in ceph cluster: rbd -p one --id libvirt du

NAME         PROVISIONED    USED
one-42@snap        1024M 73728k <- old snapshot with 3 files
one-42             1024M 12288k <-- original image with 1 file
one-42-625-1       1024M  4096k <-- latest image, clone of snapshot 1st line with 3 files

Verify that new clone is in fact from snapshot:
rbd --id libvirt children one/one-42@snap

one/one-42-625-1

So now whenever I boot image as non persitent, old snapshot (3 files) for image cloning is used. When I boot it as persitent original/latest image (1 file) is used.

I think rbd snapshot needs to be removed after we terminate last running vm with none persitent image.