LVM access rules concurrency

[Rodrigo Barbieri]

LVM drivers may have several backend configurations with different backend names in the same node. Currently the NFS code it uses employs a lock mechanism based on backend name. This way the lock does not conflict between the two backends, but both are modifying the same /etc/exports file when adding/removing access rules.
Changing to IP address still would not be a good enough fix because the same node may use one backend configuration per network interface. A new mechanism needs to be defined to lock the manila node affecting all backends registered.

[Ben Swartzlander (bswartz)]

Is there a use case for 2 LVM backends on the same host, other than testing? Is the testing configuration important enough that this needs to be fixed?

[Rodrigo Barbieri (rodrigo-barbieri2010)]

if the LVM driver is ever going to be used in production environments, admin may want to optmize traffic by serving each backend through a network interface. This is the only use case I can imagine that would require this fix.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/292370

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/292370
Committed: https://git.openstack.org/cgit/openstack/manila/commit/?id=e49324f671319318ff69ed290e0b136dab60ab13
Submitter: Jenkins
Branch: master

commit e49324f671319318ff69ed290e0b136dab60ab13
Author: vponomaryov <email address hidden>
Date: Mon Mar 14 14:57:06 2016 +0200

    Fix lock decorator usage for LVM and Generic drivers

    DHSS=False mode of LVM and Generic drivers uses not safe locking
    for NFS helper. So, several instances of same driver may suffer
    from race conditions for modification of NFS config files.

    So, make this lock external (inter-process) and add possibility to
    set up "lock_name", that is useful in case of LVM driver. Also,
    make Generic driver use "instance_id" instead of IP address.
    In those both cases we avoid race conditions.

    Change-Id: I0687b1080cb6a0e1d3bf7c87066fa46c06977181
    Closes-Bug: #1550378

[Doug Hellmann (doug-hellmann)]

This issue was fixed in the openstack/manila 2.0.0.0rc1 release candidate.

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/manila 2.0.0 release.