Merge PR #22486 into master

* refs/pull/22486/head:
	mds: avoid traversing all dirfrags when trying to get wrlocks

Reviewed-by: Zheng Yan <zyan@redhat.com>

diff --cc src/mds/CDir.cc
Simple merge

diff --cc src/mds/CDir.h
Simple merge

diff --cc src/mds/CInode.cc
Simple merge

diff --cc src/mds/CInode.h
Simple merge

diff --cc src/mds/MDCache.cc
Simple merge

diff --cc src/mds/Migrator.cc
index 55b1ff9418a10ced41ea30a5d75e80d3906e4529,76e84ba47fcf1a6382583685b97b5d11858010f9..fa4852df2be43aee99d5591cb1679bf4c3d7b415
--- 1/src/mds/Migrator.cc
--- 2/src/mds/Migrator.cc
+++ b/src/mds/Migrator.cc
@@@ -860,10 -860,10 +860,10 @@@ void Migrator::export_dir(CDir *dir, md
      }
    }
  
 -  mds->hit_export_target(ceph_clock_now(), dest, -1);
 +  mds->hit_export_target(dest, -1);
  
    dir->auth_pin(this);
-   dir->state_set(CDir::STATE_EXPORTING);
+   dir->mark_exporting();
  
    MDRequestRef mdr = mds->mdcache->request_start_internal(CEPH_MDS_OP_EXPORTDIR);
    mdr->more()->export_dir = dir;