Description of problem:
IO operation is getting hanged while trying to write on same rbd image ( mandatory exclusive feature enabled )  one after the other from 3 different VMs.

Version-Release number of selected component (if applicable):
ceph version 0.94.1 (e4bfad3a3c51054df7e537a724c8d0bf9be972ff)
librbd1-0.94.1-10.el7cp.x86_64

How reproducible:
2 out of 2 times

Steps to Reproduce:
1. Create a rbd image,take snap and clone it with --image-features 5 (Exclusive lock enabled)

rbd image 'snap1':
        size 13240 MB in 3310 objects
        order 22 (4096 kB objects)
        block_name_prefix: rbd_data.a0f202eb141f2
        format: 2
        features: layering, exclusive
        flags: 
        parent: Tanay-RBD/Anfield@1
        overlap: 13240 MB

2. Attach the same rbd image on 3 different VMs as a spare disk.
3. write a small 10 mb file from all 3 different VMs one after the other.

while true; do dd if=10M of=/dev/vdb bs=1M count=10; echo "Sleeping now"; sleep 45; done

4. When the write complete on 1st VM and starts sleeping( it was taking around 4-5 seconds to complete the write) start the same command on 2nd Vm and so on for 3rd vm.

Actual results:
The lock was getting changed when the VM2 tries to write the file and same for VM3 and VM1

TG1     client.663435 (VM1)
TG2     client.663762 (VM2)
TEST    client.662967 (VM3)

It was working smoothly for 20 odd iterations, but after that the IO didn't continue and the lock got stuck  with VM1 forever, hence the IO is stalled on all the 3 Vms.

And i could see all the clients got blacklisted.

ceph osd blacklist ls
listed 3 entries
10.12.27.45:0/1005465 2015-05-26 04:06:34.530285
10.12.27.45:0/2005465 2015-05-26 04:02:37.331390
10.12.27.45:0/1005376 2015-05-26 04:03:16.993895

Expected results:
The IO should have continued and the lock changing should have happened forever among the 3 VMs.

Additional info:
After a while the the blacklisting is showing no entries.
listed 0 entries

Didn't see any log message on MON and OSD's.