mds: print the path depth to help debug mds issue

From the path depth we can get more useful info, such as whether
the path_traverse() acquired any locks, etc.

Fixes: https://tracker.ceph.com/issues/67280
Signed-off-by: Xiubo Li <[email protected]>

Author: lxbsz

src/mds/MDCache.cc

@@ -8335,7 +8335,8 @@ int MDCache::path_traverse(const MDRequestRef& mdr, MDSContextFactory& cf,
 
   if (mds->logger) mds->logger->inc(l_mds_traverse);
 
-  dout(7) << "traverse: opening base ino " << path.get_ino() << " snap " << snapid << dendl;
+  dout(7) << "traverse: opening base ino " << path.get_ino() << " snap " << snapid
+          << " path depth " << path.depth() << dendl;
   CInode *cur = get_inode(path.get_ino());
   if (!cur) {
     if (MDS_INO_IS_MDSDIR(path.get_ino())) {