libceph: primary_temp infrastructure

Add primary_temp mappings infrastructure.  struct ceph_pg_mapping is
overloaded, primary_temp mappings are stored in an rb-tree, rooted at
ceph_osdmap, in a manner similar to pg_temp mappings.

Dump primary_temp mappings to /sys/kernel/debug/ceph/<client>/osdmap,
one 'primary_temp <pgid> <osd>' per line, e.g:

    primary_temp 2.6 4

Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Alex Elder <elder@linaro.org>
diff --git a/net/ceph/osdmap.c b/net/ceph/osdmap.c
index c67a309..c0fc517 100644
--- a/net/ceph/osdmap.c
+++ b/net/ceph/osdmap.c
@@ -343,7 +343,7 @@
 
 /*
  * rbtree of pg_mapping for handling pg_temp (explicit mapping of pgid
- * to a set of osds)
+ * to a set of osds) and primary_temp (explicit primary setting)
  */
 static int pgid_cmp(struct ceph_pg l, struct ceph_pg r)
 {
@@ -633,6 +633,13 @@
 		rb_erase(&pg->node, &map->pg_temp);
 		kfree(pg);
 	}
+	while (!RB_EMPTY_ROOT(&map->primary_temp)) {
+		struct ceph_pg_mapping *pg =
+			rb_entry(rb_first(&map->primary_temp),
+				 struct ceph_pg_mapping, node);
+		rb_erase(&pg->node, &map->primary_temp);
+		kfree(pg);
+	}
 	while (!RB_EMPTY_ROOT(&map->pg_pools)) {
 		struct ceph_pg_pool_info *pi =
 			rb_entry(rb_first(&map->pg_pools),
@@ -966,6 +973,7 @@
 		return ERR_PTR(-ENOMEM);
 
 	map->pg_temp = RB_ROOT;
+	map->primary_temp = RB_ROOT;
 	mutex_init(&map->crush_scratch_mutex);
 
 	ret = osdmap_decode(p, end, map);