OpenAFS Master Repository branch, master, updated. openafs-stable-1_8_0pre1-68-g8f46ca0

[Gerrit Code Review]

The following commit has been merged in the master branch:
commit 8f46ca082653116c9c42a69e2535be1bb2f0a2a9
Author: Marcio Barbosa <mbarbosa@sinenomine.net>
Date:   Wed Jun 21 17:42:37 2017 -0300

    ubik: allow remote dbase relabel if up to date
    
    When a site is elected the sync-site, its database is not immediately
    relabeled. The database in question will be relabeled at the end of the
    first write transaction (in udisk_commit). To do so, the dbase->version
    is updated on the sync-site first (1) and then the versions of the
    remote sites are updated through SDISK_SetVersion() (2).
    
    In order to make sure that the remote site holds the same database as
    the sync-site, the SDISK_SetVersion() function checks if the current
    version held by the remote site (ubik_dbVersion) is equal to the
    original version stored by the sync-site (oldversionp). If
    ubik_dbVersion is not equal to oldversionp, SDISK_SetVersion() will
    fail with USYNC.
    
    However, ubik_dbVersion can be updated by the vote thread at any time.
    That is, if the sync site calls VOTE_Beacon() on the remote site between
    events (1) and (2), the remote site will set ubik_dbVersion to the new
    version, while ubik_dbase->version is still set to the old version. As
    a result, ubik_dbVersion will not be equal to oldversionp and
    SDISK_SetVersion() will fail with USYNC. This failure may cause a loss
    of quorum until another election is completed.
    
    To fix this problem, let SDISK_SetVersion() relabel the database when
    ubik_dbase->version is equal to oldversionp. In order to try to only
    affect the scenario described above, also check if ubik_dbVersion is
    equal to newversionp.
    
    Change-Id: I97e6f8cacd1c9bca0b4c72374c058c5fe5b638b3
    Reviewed-on: https://gerrit.openafs.org/12613
    Tested-by: BuildBot <buildbot@rampaginggeek.com>
    Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>

 src/ubik/remote.c |   10 ++++++++--
 1 files changed, 8 insertions(+), 2 deletions(-)

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