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>

include/linux/ceph/osdmap.h

@@ -66,6 +66,9 @@ struct ceph_pg_mapping {
 			int len;
 			int osds[];
 		} pg_temp;
+		struct {
+			int osd;
+		} primary_temp;
 	};
 };
 
@@ -83,6 +86,8 @@ struct ceph_osdmap {
 	struct ceph_entity_addr *osd_addr;
 
 	struct rb_root pg_temp;
+	struct rb_root primary_temp;
+
 	struct rb_root pg_pools;
 	u32 pool_max;
 

net/ceph/debugfs.c

@@ -93,6 +93,13 @@ static int osdmap_show(struct seq_file *s, void *p)
 				   pg->pg_temp.osds[i]);
 		seq_printf(s, "]\n");
 	}
+	for (n = rb_first(&map->primary_temp); n; n = rb_next(n)) {
+		struct ceph_pg_mapping *pg =
+			rb_entry(n, struct ceph_pg_mapping, node);
+
+		seq_printf(s, "primary_temp %llu.%x %d\n", pg->pgid.pool,
+			   pg->pgid.seed, pg->primary_temp.osd);
+	}
 
 	return 0;
 }

net/ceph/osdmap.c

@@ -343,7 +343,7 @@ static struct crush_map *crush_decode(void *pbyval, void *end)
 
 /*
  * 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 @@ void ceph_osdmap_destroy(struct ceph_osdmap *map)
 		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 @@ struct ceph_osdmap *ceph_osdmap_decode(void **p, void *end)
 		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);