Re: [PATCH v2 07/10] mmap locking API: add mmap_read_release() and mmap_read_unlock_non_owner()

[Davidlohr Bueso]

On Thu, 26 Mar 2020, Michel Lespinasse wrote:

> Add a couple APIs to allow splitting mmap_read_unlock() into two calls:
> - mmap_read_release(), called by the task that had taken the mmap lock;
> - mmap_read_unlock_non_owner(), called from a work queue.
>
> These apis are used by kernel/bpf/stackmap.c only.

I'm not crazy about the idea generalizing such calls into an mm api.
We try to stay away from non-owner semantics in locking - granted
the IS_ENABLED(CONFIG_PREEMPT_RT) warning, but still.

Could this give future users the wrong impression? What about just
using rwsem calls directly in bpf?

Thanks,
Davidlohr