drbd: make suspend_io() / resume_io() must be thread and recursion safe

Avoid to prematurely resume application IO: don't set/clear a single
bit, but inc/dec an atomic counter.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
3 files changed