ceph: fix cache revoke race

handle following sequence of events:

- non-auth MDS revokes Fc cap. queue invalidate work
- auth MDS issues Fc cap through request reply. i_rdcache_gen gets
  increased.
- invalidate work runs. it finds i_rdcache_revoking != i_rdcache_gen,
  so it does nothing.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>

fs/ceph/caps.c

@@ -816,7 +816,7 @@ int __ceph_caps_revoking_other(struct ceph_inode_info *ci,
 
 	for (p = rb_first(&ci->i_caps); p; p = rb_next(p)) {
 		cap = rb_entry(p, struct ceph_cap, ci_node);
-		if (cap != ocap && __cap_is_valid(cap) &&
+		if (cap != ocap &&
 		    (cap->implemented & ~cap->issued & mask))
 			return 1;
 	}