mds: prevent trim count from underflowing

Fixes: http://tracker.ceph.com/issues/21807
Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>

diff --git a/src/mds/MDCache.cc b/src/mds/MDCache.cc
index 17e3c4323aa6cc33ae0357b5e1e6e8570a06dde5..17068a64ca2deb9c2033d97634feb950e0bd0f07 100644 (file)
--- a/src/mds/MDCache.cc
+++ b/src/mds/MDCache.cc
@@ -6457,8 +6457,8 @@ void MDCache::trim_lru(uint64_t count, map<mds_rank_t, MCacheExpire*> &expiremap
       unexpirables.push_back(dn);
     } else {
       trimmed++;
+      if (count > 0) count--;
     }
-    count--;
   }
 
   for (auto &dn : unexpirables) {