Ceph » CephFS

In my cluster with a single MDS, ceph version is 12.2.13, Assert will be encountered when a large number of deletion operations are performed. Now I can't reproduce it, so I didn't catch more logs.
backtrace:

 0> 2020-11-03 15:32:35.316352 7f47dd5aa700 -1 /share/ceph/rpmbuild/BUILD/ceph-12.2.13/src/mds/Server.cc: In function 'bool Server::_dir_is_nonempty(MDRequestRef&, CInode*)' thread 7f47dd5aa700 time 2020-11-03 15:32:35.311722
/share/ceph/rpmbuild/BUILD/ceph-12.2.13/src/mds/Server.cc: 6783: FAILED assert(in->filelock.can_read(mdr->get_client()))

 ceph version 12.2.13-1-560-g87ea0b6 (87ea0b6e94eaa3544572dd676db0e8932f56d7a8) luminous (stable)
 1: (ceph::__ceph_assert_fail(char const*, char const*, int, char const*)+0x110) [0x55c2f7b60640]
 2: (Server::_dir_is_nonempty(boost::intrusive_ptr<MDRequestImpl>&, CInode*)+0x1a8) [0x55c2f7813ab8]
 3: (Server::handle_client_unlink(boost::intrusive_ptr<MDRequestImpl>&)+0x13df) [0x55c2f7843bef]
 4: (Server::dispatch_client_request(boost::intrusive_ptr<MDRequestImpl>&)+0xdb9) [0x55c2f7869479]
 5: (MDSInternalContextBase::complete(int)+0x1fb) [0x55c2f7a9c34b]
 6: (void finish_contexts<MDSInternalContextBase>(CephContext*, std::list<MDSInternalContextBase*, std::allocator<MDSInternalContextBase*> >&, int)+0x16c) [0x55c2f77c10bc]
 7: (MDSCacheObject::finish_waiting(unsigned long, int)+0x46) [0x55c2f7ab66e6]
 8: (Locker::eval_gather(SimpleLock*, bool, bool*, std::list<MDSInternalContextBase*, std::allocator<MDSInternalContextBase*> >*)+0x124f) [0x55c2f798958f]
 9: (Locker::wrlock_finish(SimpleLock*, MutationImpl*, bool*)+0x341) [0x55c2f798b261]
 10: (Locker::_drop_non_rdlocks(MutationImpl*, std::set<CInode*, std::less<CInode*>, std::allocator<CInode*> >*)+0x22c) [0x55c2f798f14c]
 11: (Locker::drop_locks(MutationImpl*, std::set<CInode*, std::less<CInode*>, std::allocator<CInode*> >*)+0x76) [0x55c2f798f586]
 12: (Locker::scatter_writebehind_finish(ScatterLock*, boost::intrusive_ptr<MutationImpl>&)+0xd0) [0x55c2f798f6d0]
 13: (MDSIOContextBase::complete(int)+0xa5) [0x55c2f7a9c4e5]
 14: (MDSLogContextBase::complete(int)+0x3c) [0x55c2f7a9caec]
 15: (Finisher::finisher_thread_entry()+0x198) [0x55c2f7b5f2d8]
 16: (()+0x7e65) [0x7f47e9f64e65]
 17: (clone()+0x6d) [0x7f47e92588ad]
 NOTE: a copy of the executable, or `objdump -rdS <executable>` is needed to interpret this.

I have a suspicion. I'm not sure whether this problem is related to it.
In Server::handle_client_unlink，first, rdlock the filelock of the inode to be deleted, and then in Server::_dir_is_nonempty, confirm that filelock can read through "assert(in->filelock.can_read(mdr->get_client()))".But filelock allows can_rdlock but not allow can_read in two states, like the following two states:

  [LOCK_EXCL]      = { 0,         true,  LOCK_LOCK, 0,    0,   XCL, XCL, 0,   0,   0,  
  [LOCK_EXCL_XSYN] = { LOCK_XSYN, false, LOCK_LOCK, 0,    0,   XCL, 0,   0,   0,   0,

If the filelock is in these two states, will the above assert appears?