[Bugs] [Bug 1219075] Named lookup heal of pre-existing files, before ctr was ON

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=1219075



--- Comment #4 from Anand Avati <aavati at redhat.com> ---
COMMIT: http://review.gluster.org/10615 committed in release-3.7 by Vijay
Bellur (vbellur at redhat.com) 
------
commit 268b7fcb307e14cce5bcd28495f24333710ba82c
Author: Joseph Fernandes <josferna at redhat.com>
Date:   Fri Apr 24 19:22:44 2015 +0530

    ctr/xlator: Named lookup heal of pre-existing files, before ctr was ON.

    Problem: The CTR xlator records file meta (heat/hardlinks)
    into the data. This works fine for files which are created
    after ctr xlator is switched ON. But for files which were
    created before CTR xlator is ON, CTR xlator is not able to
    record either of the meta i.e heat or hardlinks. Thus making
    those files immune to promotions/demotions.

    Solution: The solution that is implemented in this patch is
    do ctr-db heal of all those pre-existent files, using named lookup.
    For this purpose we use the inode-xlator context variable option
    in gluster.
    The inode-xlator context variable for ctr xlator will have the
    following,
        a. A Lock for the context variable
        b. A hardlink list: This list represents the successful looked
           up hardlinks.
    These are the scenarios when the hardlink list is updated:
    1) Named-Lookup: Whenever a named lookup happens on a file, in the
       wind path we copy all required hardlink and inode information to
       ctr_db_record structure, which resides in the frame->local variable.
       We dont update the database in wind. During the unwind, we read the
       information from the ctr_db_record and ,
       Check if the inode context variable is created, if not we create it.
       Check if the hard link is there in the hardlink list.
          If its not there we add it to the list and send a update to the
          database using libgfdb.
          Please note: The database transaction can fail(and we ignore) as
there
          already might be a record in the db. This update to the db is to heal
          if its not there.
          If its there in the list we ignore it.
    2) Inode Forget: Whenever an inode forget hits we clear the hardlink list
in
       the inode context variable and delete the inode context variable.
       Please note: An inode forget may happen for two reason,
       a. when the inode is delete.
       b. the in-memory inode is evicted from the inode table due to cache
limits.
    3) create: whenever a create happens we create the inode context variable
and
       add the hardlink. The database updation is done as usual by ctr.
    4) link: whenever a hardlink is created for the inode, we create the inode
context
       variable, if not present, and add the hardlink to the list.
    5) unlink: whenever a unlink happens we delete the hardlink from the list.
    6) mknod: same as create.
    7) rename: whenever a rename happens we update the hardlink in list. if the
hardlink
       was not present for updation, we add the hardlink to the list.

    What is pending:
    1) This solution will only work for named lookups.
    2) We dont track afr-self-heal/dht-rebalancer traffic for healing.

    > http://review.gluster.org/#/c/10370/
    > Cherry picked from commit cb11dd91a6cc296e4a3808364077f4eacb810e48
    > Change-Id: Ia4bbaf84128ad6ce8c3ddd70bcfa82894c79585f
    > BUG: 1212037
    > Signed-off-by: Joseph Fernandes <josferna at redhat.com>
    > Signed-off-by: Dan Lambright <dlambrig at redhat.com>
    > Reviewed-on: http://review.gluster.org/10370
    > Reviewed-by: Jeff Darcy <jdarcy at redhat.com>
    > Tested-by: Gluster Build System <jenkins at build.gluster.com>
    > Tested-by: NetBSD Build System
    > Reviewed-by: Vijay Bellur <vbellur at redhat.com>

    Change-Id: I367aa46c3f4b8f912248fb8be75866507f2538df
    BUG: 1219075
    Signed-off-by: Joseph Fernandes <josferna at redhat.com>
    Signed-off-by: Dan Lambright <dlambrig at redhat.com>
    Reviewed-on: http://review.gluster.org/10370
    Reviewed-by: Jeff Darcy <jdarcy at redhat.com>
    Reviewed-by: Vijay Bellur <vbellur at redhat.com>
    Signed-off-by: Joseph Fernandes <josferna at redhat.com>
    Reviewed-on: http://review.gluster.org/10615
    Tested-by: Vijay Bellur <vbellur at redhat.com>

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