From: Sage Weil <sage@redhat.com>
Date: Tue, 30 Oct 2018 20:35:23 +0000 (-0500)
Subject: common/mempool: tolerate sum < 0
X-Git-Tag: v14.1.0~996^2
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=refs%2Fpull%2F14982%2Fhead;p=ceph.git

common/mempool: tolerate sum < 0

If we are adding up the shards, and race with some allocations and
deallocations, we might get a negative sum.  E.g., with 2 shards, intially
[0,0],

- A: read shard 0 (0)
- B: allocate object on shard 0 (now 1)
- C: dallocate object on shard 1 (now -1)
- A: read shard 1 (-1)
- A: sum is -1

Signed-off-by: Sage Weil <sage@redhat.com>
---

diff --git a/src/common/mempool.cc b/src/common/mempool.cc
index cb9de40da09..fd9a42d8f52 100644
--- a/src/common/mempool.cc
+++ b/src/common/mempool.cc
@@ -70,7 +70,10 @@ size_t mempool::pool_t::allocated_bytes() const
   for (size_t i = 0; i < num_shards; ++i) {
     result += shard[i].bytes;
   }
-  ceph_assert(result >= 0);
+  if (result < 0) {
+    // we raced with some unbalanced allocations/deallocations
+    result = 0;
+  }
   return (size_t) result;
 }
 
@@ -80,7 +83,10 @@ size_t mempool::pool_t::allocated_items() const
   for (size_t i = 0; i < num_shards; ++i) {
     result += shard[i].items;
   }
-  ceph_assert(result >= 0);
+  if (result < 0) {
+    // we raced with some unbalanced allocations/deallocations
+    result = 0;
+  }
   return (size_t) result;
 }