Merge pull request #17711 from batrick/bp20594

luminous: mds: support limiting cache by memory

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

diff --cc src/client/Client.cc
Simple merge

diff --cc src/common/legacy_config_opts.h
Simple merge

diff --cc src/common/options.cc
Simple merge

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

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

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