f2fs: turn down IO priority of discard from background

In order to avoid interfering normal r/w IO, let's turn down IO
priority of discard issued from background.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This commit is contained in:
Chao Yu 2018-04-10 15:43:09 +08:00 • committed by Jaegeuk Kim
commit cba608493d