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

[bugzilla at redhat.com]

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

            Bug ID: 1219075
           Summary: Named lookup heal of pre-existing files, before ctr
                    was ON
           Product: GlusterFS
           Version: 3.7.0
         Component: tiering
          Assignee: bugs at gluster.org
          Reporter: josferna at redhat.com
        QA Contact: bugs at gluster.org
                CC: bugs at gluster.org



Description of problem:

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.

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