afr/cluster: PGFID heal support

Summary:
  PGFID healing enables heals which might otherwise fail due
  due to the lack of a entry heal to succeed by performing
  the entry healing within the same heal flow.

  It does this by leveraging the PGFID tracking feature of
  the POSIX xlator, and examining lookup replies for the
  PGFID attribute.  If detected, the pgfid will be decoded
  and stored for later use in case the heal fails for whatever
  reason.  Cascading heal failures are handled through
  recursion.

  This feature is critical for a couple reasons:
      1. General healing predictability - When the SHD
         attempts to heal a given GFID, it should be able
         to do so without having to wait for some other
         dependent heal to take place.
      2. Reliability - In some cases the parent directory
         may require healing, but the req'd entry in the
         indices/xattrop directory may not exist
         (e.g. bugs/crashes etc).  Prior to PGFID heal support
         some sort of external script would be required to
         queue up these heals by using FS specific utilities
         to lookup the parent directory by hardlink or
         worse...do a costly full heal to clean them up.
      3. Performance - In combination with multi-threaded SHD
         this feature will make SHD healing _much_ faster as
         directories with large amount of files to be healed
         will no longer have to wait for an entry heal to
         come along, the first file in that directory queued
         for healing will trigger an entry heal for the directory
         and this will allow the other files in that directory
         to be (immediatelly) healed in parallel.

Test Plan:
- run prove tests/basic/afr/shd_pgfid_heal.t
- run prove tests/basic/afr/shd*.t
- run prove tests/basic/afr/gfid*.t

Differential Revision: https://phabricator.fb.com/D2546133

Change-Id: I25f586047f8bcafa900c0cc9ee8f0e2128688c73
Signed-off-by: Jeff Darcy <jdarcy@fb.com>
Reviewed-on: https://review.gluster.org/17929
Smoke: Gluster Build System <jenkins@build.gluster.org>
Tested-by: Jeff Darcy <jeff@pl.atyp.us>
CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
Reviewed-by: Jeff Darcy <jeff@pl.atyp.us>

0 files changed, 0 insertions, 0 deletions