ceph: Reconstruct the func ceph_reserve_caps.

Drop ignored return value.  Fix allocation failure case to not leak.

Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
Reviewed-by: Sage Weil <sage@inktank.com>

fs/ceph/super.h

@@ -534,7 +534,7 @@ extern int __ceph_caps_mds_wanted(struct ceph_inode_info *ci);
 extern void ceph_caps_init(struct ceph_mds_client *mdsc);
 extern void ceph_caps_finalize(struct ceph_mds_client *mdsc);
 extern void ceph_adjust_min_caps(struct ceph_mds_client *mdsc, int delta);
-extern int ceph_reserve_caps(struct ceph_mds_client *mdsc,
+extern void ceph_reserve_caps(struct ceph_mds_client *mdsc,
 			     struct ceph_cap_reservation *ctx, int need);
 extern int ceph_unreserve_caps(struct ceph_mds_client *mdsc,
 			       struct ceph_cap_reservation *ctx);