osd/PGLog: assert out on performing overflowed log trimming

Performing overflowed log-trim can be a sign of big trouble, e.g.,
the **complete_to** iterator will now point to an invalid position
of the original pg-log list when the trimming is done, and hence
randomly trigger **Segmentation fault**s as below:
```
2018-03-07 17:38:46.109018 7f274a4ed700 -1 *** Caught signal (Segmentation fault) **
1: (()+0xa51f31) [0x7f278290bf31]
2: (()+0xf370) [0x7f277fb4f370]
3: (PrimaryLogPG::recover_got(hobject_t, eversion_t)+0x266) [0x7f2782512786]
4: (PrimaryLogPG::on_local_recover(hobject_t const&, ObjectRecoveryInfo const&, std::shared_ptr<ObjectContext>, bool, ObjectStore::Tran
saction*)+0x2a4) [0x7f278251f3b4]
5: (ReplicatedBackend::handle_push(pg_shard_t, PushOp const&, PushReplyOp*, ObjectStore::Transaction*)+0x2e2) [0x7f2782690f82]
6: (ReplicatedBackend::_do_push(boost::intrusive_ptr<OpRequest>)+0x194) [0x7f2782691224]
7: (ReplicatedBackend::_handle_message(boost::intrusive_ptr<OpRequest>)+0x2f1) [0x7f278269fd41]
8: (PGBackend::handle_message(boost::intrusive_ptr<OpRequest>)+0x50) [0x7f27825c2470]
```

The root cause of why PGs are starting to trim more log entries than
we expect is still lost to me, but setting the trap here should generally
do no harm and hopefully expose the above problem a little bit more offen.
We'll see.

Signed-off-by: xie xingguo <xie.xingguo@zte.com.cn>

diff --git a/src/osd/PGLog.cc b/src/osd/PGLog.cc
index 22476bcec6ad97f845ab58fedc0da2cbe46a2085..4445a9cf1a479790e80992979c6bfae4643b9184 100644 (file)
--- a/src/osd/PGLog.cc
+++ b/src/osd/PGLog.cc
@@ -52,9 +52,10 @@ void PGLog::IndexedLog::trim(
 {
   if (complete_to != log.end() &&
       complete_to->version <= s) {
-    generic_dout(0) << " bad trim to " << s << " when complete_to is "
-                   << complete_to->version
-                   << " on " << *this << dendl;
+    generic_derr << " bad trim to " << s << " when complete_to is "
+                << complete_to->version
+                << " on " << *this << dendl;
+    assert(0 == "out of order trim");
   }
 
   assert(s <= can_rollback_to);