ceph: kill ceph_empty_snapc

ceph_empty_snapc->num_snaps == 0 at all times.  Passing such a snapc to
ceph_osdc_alloc_request() (possibly through ceph_osdc_new_request()) is
equivalent to passing NULL, as ceph_osdc_alloc_request() uses it only
for sizing the request message.

Further, in all four cases the subsequent ceph_osdc_build_request() is
passed NULL for snapc, meaning that 0 is encoded for seq and num_snaps
and making ceph_empty_snapc entirely useless.  The two cases where it
actually mattered were removed in commits 860560904962 ("ceph: avoid
sending unnessesary FLUSHSNAP message") and 23078637e054 ("ceph: fix
queuing inode to mdsdir's snaprealm").

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by:  Yan, Zheng <zyan@redhat.com>
diff --git a/fs/ceph/super.c b/fs/ceph/super.c
index e82acc6..715282a 100644
--- a/fs/ceph/super.c
+++ b/fs/ceph/super.c
@@ -1042,19 +1042,14 @@
 
 	ceph_flock_init();
 	ceph_xattr_init();
-	ret = ceph_snap_init();
-	if (ret)
-		goto out_xattr;
 	ret = register_filesystem(&ceph_fs_type);
 	if (ret)
-		goto out_snap;
+		goto out_xattr;
 
 	pr_info("loaded (mds proto %d)\n", CEPH_MDSC_PROTOCOL);
 
 	return 0;
 
-out_snap:
-	ceph_snap_exit();
 out_xattr:
 	ceph_xattr_exit();
 	destroy_caches();
@@ -1066,7 +1061,6 @@
 {
 	dout("exit_ceph\n");
 	unregister_filesystem(&ceph_fs_type);
-	ceph_snap_exit();
 	ceph_xattr_exit();
 	destroy_caches();
 }