[Bugs] [Bug 1262197] DHT: Few files are missing after remove-brick operation

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=1262197



--- Comment #4 from Vijay Bellur <vbellur at redhat.com> ---
COMMIT: http://review.gluster.org/12156 committed in release-3.7 by Raghavendra
G (rgowdapp at redhat.com) 
------
commit 23e522eea17e15b37d395e2005139dd3d5a9e3a1
Author: Susant Palai <spalai at redhat.com>
Date:   Fri Sep 4 05:14:05 2015 -0400

    dht/remove-brick: Avoid data loss for hard link migration

    Problem: If the hashed subvol of a file has reached cluster.min-free-disk,
    for a create opertaion a linkto file will be created on the hashed and
    the data file will be created on some other brick.

    For creation of the linkfile we populate the dictionary with linkto key
    and value as the cached subvol. After successful linkto file creation,
    the linkto-key-value pair is not deleted form the dictionary and hence,
    the data file will also have linkto xattr which points to itself.This looks
    something like this.

      client-0                                    client-1
    -------T file                               rwx------file
    linkto.xattr=client-1                       linkto.xattr=client-1

    Now coming to the data loss part. Hardlink migration highly depend on this
    linkto xattr on the data file. This value should be the new hashed subvol
    of the first hardlink encountered post fix-layout. But when it tries to
    read the linkto xattr it gets the same target as where it is sitting.

    Now the source and destination are same for migration. At the end of
    migration the source file is truncated and deleted, which in this case
    is the destination and also the only data file it self resulting in
    data loss.

    BUG: 1262197
    Change-Id: I5338a5704ac60ca9afb278977e178319266a0cc0
    Signed-off-by: Susant Palai <spalai at redhat.com>
    Reviewed-on: http://review.gluster.org/12105
    Reviewed-by: N Balachandran <nbalacha at redhat.com>
    Tested-by: NetBSD Build System <jenkins at build.gluster.org>
    Reviewed-by: Raghavendra G <rgowdapp at redhat.com>
    Signed-off-by: Susant Palai <spalai at redhat.com>
    Reviewed-on: http://review.gluster.org/12156
    Tested-by: Gluster Build System <jenkins at build.gluster.com>

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