cluster/dht: Fix dht_link to follow files under migration

Currently if a file is under migration, a hardlink to that file
is lost post migration of the file. This is due to the fact that
the hard link is created against the cached subvol of the source
and as the source is under migration, it shifts to a linkto file
post migration. Thus losing the hardlink.

This change follows the stat information that triggers a phase1/2
detection for a file under migration, to create the link on the new
subvol that the source file is migrating to. Thereby preserving the
hard link post migration.

NOTES:
The test case added create a ~1GB file, so that we can catch the file
during migration, smaller files may not capture this state and the
test may fail.
Even if migration of the file fails, we would only be left with stale
linkto files on the subvol that the source was migrating to, which is
not a problem.
This change would create a double linkto, i.e new target hashed subvol
would point to old source cached subol, which would point to the real
cached subvol. This double redirection although not handled directly in
DHT, works as lookup searches everywhere on hitting linkto files. The
downside is that it never heals the new target hashed subvol linkto
file, which is another bug to be resolved (does not cause functional
impact).

Change-Id: I871e6885b15e65e05bfe70a0b0180605493cb534
BUG: 1161311
Signed-off-by: Shyam <srangana@redhat.com>
Reviewed-on: http://review.gluster.org/9105
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: N Balachandran <nbalacha@redhat.com>
Reviewed-by: susant palai <spalai@redhat.com>
Reviewed-by: venkatesh somyajulu <vsomyaju@redhat.com>
Reviewed-by: Raghavendra G <rgowdapp@redhat.com>
Tested-by: Raghavendra G <rgowdapp@redhat.com>

0 files changed, 0 insertions, 0 deletions