mds/Locker: use ceph_abort_msg() instead of ceph_assert()

This ceph_assert() always fails, but depending on the configuration
value `ceph_assert_supresssions`, execution may continue, but the
`dir` variable is left uninitialized.  This leads to a compiler
warning:

 /home/jenkins-build/build/workspace/ceph-api/src/mds/Locker.cc:451:22: error: variable 'dir' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]

clang then suggests to nullptr-initialize the variable:

 /home/jenkins-build/build/workspace/ceph-api/src/mds/Locker.cc:447:11: note: initialize the variable 'dir' to silence this warning
   447 |         CDir *dir;
       |                  ^
       |                   = nullptr

This, however, is a very bad idea because all this does is suppress
the warning; it still crashes the process.

Since there's no recovery from this problem, let's switch to
ceph_abort_msg() which is [[noreturn]] and the compiler can deduce
that `dir` is always initialized when it's used.

Signed-off-by: Max Kellermann <[email protected]>

Author: MaxKellermann

src/mds/Locker.cc

@@ -451,7 +451,7 @@ bool Locker::acquire_locks(const MDRequestRef& mdr,
 	} else if (CDentry *dn = dynamic_cast<CDentry*>(object)) {
 	  dir = dn->get_dir();
 	} else {
-	  ceph_assert(0 == "unknown type of lock parent");
+	  ceph_abort_msg("unknown type of lock parent");
 	}
 	if (dir->get_inode() == mdr->lock_cache->get_dir_inode()) {
 	  // forcibly auth pin if there is lock cache on parent dir