[Bugs] [Bug 1271148] Tier: Do not promote/demote files on which POSIX locks are held

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=1271148



--- Comment #4 from Vijay Bellur <vbellur at redhat.com> ---
COMMIT: http://review.gluster.org/12347 committed in master by Dan Lambright
(dlambrig at redhat.com) 
------
commit bd71446b25aefe066ca18a28d73d777774ab7f87
Author: N Balachandran <nbalacha at redhat.com>
Date:   Tue Oct 13 15:02:00 2015 +0530

    cluster/dht : Do not migrate files with POSIX locks held

    dht_migrate_file does not migrate file locks to the dst file.
    Any locks held on the source file are lost once the migration
    is complete. This issue is magnified in the case of a tier volume
    as file migrations occur more frequently and repeatedly as compared
    to a DHT rebalance.

    The fix makes 2 changes:
    1. Before starting the actual migration process, check if there are
     any locks held on the file. If yes, do not migrate the file.
    2. The rebalance process tries to lock on the entire file just before
     moving into the Phase 2 of the file migration. If the lock acquisition
    fails, the file migration does not proceed.
    If the lock is granted, the file migration proceeds.

    This still leaves a small window where conflicting locks can be granted to
    different clients. If client1 requests a lock on the src file just after
    it is converted to a linkto file and client2 requests a lock on the dst
    data file, they will both be granted, but all FOPs will be redirected
    to the dst data file. This issue will be taken up in a subsequent patch.

    Change-Id: I8c895fc3cced50dd2894259d40a827c7b43d58ac
    BUG: 1271148
    Signed-off-by: N Balachandran <nbalacha at redhat.com>
    Reviewed-on: http://review.gluster.org/12347
    Tested-by: NetBSD Build System <jenkins at build.gluster.org>
    Tested-by: Gluster Build System <jenkins at build.gluster.com>
    Reviewed-by: Dan Lambright <dlambrig at redhat.com>
    Tested-by: Dan Lambright <dlambrig at redhat.com>

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