cluster/dht: Support for hardlink rebalance when decommissioning

The support for hardlink rebalance is only available for decommissioning
of a node. this can be triggered in two ways
1. remove-brick start
2. if decommission node value is set in vol file, then a normal rebalance
   command

The way we handle it is-
if (nlink > 1)
do
       * if src file doesnt have linkto xattr
                * mark src's linkto to the dst
       * else
                * perform a link on the dst
                * do a look up
                * if nlinks = dst.nlinks
                        * migrate data
                * else
                        * continue crawling
done
Signed-off-by: shishir gowda <shishirng@gluster.com>
Change-Id: If43b5524b872fd1413e9f7aa7f436cb244e30d8d
BUG: 763844
Reviewed-on: http://review.gluster.com/2737
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Amar Tumballi <amarts@redhat.com>

3 files changed, 35 insertions, 2 deletions

diff --git a/libglusterfs/src/syncop.c b/libglusterfs/src/syncop.c
index 7b6f78248..712e5b1f2 100644
--- a/libglusterfs/src/syncop.c
+++ b/libglusterfs/src/syncop.c
@@ -938,6 +938,38 @@ syncop_unlink (xlator_t *subvol, loc_t *loc)
 }
 
 int
+syncop_link_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+                  int32_t op_ret, int32_t op_errno, inode_t *inode,
+                  struct iatt *buf, struct iatt *preparent,
+                  struct iatt *postparent)
+{
+        struct syncargs *args = NULL;
+
+        args = cookie;
+
+        args->op_ret = op_ret;
+        args->op_errno = op_errno;
+
+        __wake (args);
+
+        return 0;
+}
+
+
+int
+syncop_link (xlator_t *subvol, loc_t *oldloc, loc_t *newloc)
+{
+        struct syncargs args = {0, };
+
+        SYNCOP (subvol, (&args), syncop_link_cbk, subvol->fops->link,
+                oldloc, newloc);
+
+        errno = args.op_errno;
+
+        return args.op_ret;
+}
+
+int
 syncop_ftruncate_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
                       int op_ret, int op_errno, struct iatt *prebuf,
                       struct iatt *postbuf)
diff --git a/libglusterfs/src/syncop.h b/libglusterfs/src/syncop.h
index 627fb6197..7d8a2cb02 100644
--- a/libglusterfs/src/syncop.h
+++ b/libglusterfs/src/syncop.h
@@ -217,5 +217,5 @@ int syncop_symlink (xlator_t *subvol, loc_t *loc, char *newpath, dict_t *dict);
 int syncop_readlink (xlator_t *subvol, loc_t *loc, char **buffer, size_t size);
 int syncop_mknod (xlator_t *subvol, loc_t *loc, mode_t mode, dev_t rdev,
                   dict_t *dict);
-
+int syncop_link (xlator_t *subvol, loc_t *oldloc, loc_t *newloc);
 #endif /* _SYNCOP_H */
diff --git a/libglusterfs/src/xlator.c b/libglusterfs/src/xlator.c
index 428357633..01475f5a1 100644
--- a/libglusterfs/src/xlator.c
+++ b/libglusterfs/src/xlator.c
@@ -567,7 +567,8 @@ loc_copy (loc_t *dst, loc_t *src)
         if (src->parent)
                 dst->parent = inode_ref (src->parent);
 
-        dst->path = gf_strdup (src->path);
+        if (src->path)
+                dst->path = gf_strdup (src->path);
 
         if (!dst->path)
                 goto out;