Merge PR #27782 into master

* refs/pull/27782/head:
	os/bluestore: protect BlueFS::FileReader::buf
	os/bluestore: log 'buffered' in KernelDevice::read_random
	os/bluestore: support RocksDB prefetching at BlueFS
	os/bluestore: call BlueFS::_init_logger earlier.
	tools/ceph-objectstore-tool: dump perf counters on competion.
	os/bluestore: optimize mapping offset to extent in BlueFS.

Reviewed-by: Sage Weil <sage@redhat.com>

diff --cc src/tools/ceph_objectstore_tool.cc
Simple merge