use fine-grained locks

[pille]

it would be nice to evaluate all locks and fine-tune them.
maybe different actions hold different locks resulting in actions being able to be done at the same time.
the most basic approach would be read/write which may allow for list or info actions during a running create. this would also create the need to handle incomplete data. e.g. the running backup should be ignored. it would be a good idea to state that one is currently running, though.

maybe it's possible to make long-runnig tasks like a check non-blocking.

[ThomasWaldmann]

well, doing a (full) check while things are changing doesn't sound like doable / advisable (and especially not check --repair).

[pille]

i don't know the details, but old data-blocks should not change. at least not in append-only mode.
it's perfectly fine to skip new blocks. check --repair clearly is out of scope, as it's not read-only.