ceph: make object hash a pg_pool property

The object will be hashed to a placement seed (ps) based on the pg_pool's
hash function.  This allows new hashes to be introduced into an existing
object store, or selection of a hash appropriate to the objects that
will be stored in a particular pool.

Signed-off-by: Sage Weil <sage@newdream.net>
diff --git a/fs/ceph/Makefile b/fs/ceph/Makefile
index 8bad70a..bdd3e6f 100644
--- a/fs/ceph/Makefile
+++ b/fs/ceph/Makefile
@@ -13,7 +13,7 @@
 	mon_client.o \
 	osd_client.o osdmap.o crush/crush.o crush/mapper.o crush/hash.o \
 	debugfs.o \
-	ceph_fs.o ceph_strings.o ceph_frag.o
+	ceph_fs.o ceph_strings.o ceph_hash.o ceph_frag.o
 
 else
 #Otherwise we were called directly from the command