The main items are:
- support for asynchronous create and unlink (Jeff Layton). Creates
and unlinks are satisfied locally, without waiting for a reply from
the MDS, provided the client has been granted appropriate caps (new
in v15.y.z ("Octopus") release). This can be a big help for metadata
heavy workloads such as tar and rsync. Opt-in with the new nowsync
mount option.
- multiple blk-mq queues for rbd (Hannes Reinecke and myself). When
the driver was converted to blk-mq, we settled on a single blk-mq
queue because of a global lock in libceph and some other technical
debt. These have since been addressed, so allocate a queue per CPU
to enhance parallelism.
- don't hold onto caps that aren't actually needed (Zheng Yan). This
has been our long-standing behavior, but it causes issues with some
active/standby applications (synchronous I/O, stalls if the standby
goes down, etc).
- .snap directory timestamps consistent with ceph-fuse (Luis Henriques)
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