On Apr 11, 2017, at 3:38 AM, Jan Kara <jack@xxxxxxx> wrote: > > Hi, > > when testing my fix for 0-day reports with writeback throttling I came > across somewhat unexpected behavior with user interface of writeback > throttling. So currently if CFQ is used as an IO scheduler, we disable > writeback throttling because they don't go well together. However when user > has CONFIG_BLK_WBT_SQ=y and switches IO scheduler to NOOP or DEADLINE > writeback throttling still stays disabled. This is somewhat unexpected > especially because the switching of IO scheduler from CFQ to something else > can have happened behind user's back by some udev rule or so. So basically > CONFIG_DEFAULT_CFQ=y and CONFIG_BLK_WBT_SQ=y don't make sense together. > > So do people thing we should enable WBT if CONFIG_BLK_WBT_SQ=y and IO > scheduler is switched from CFQ to something else? Yes, I think so. We should have consistent behavior in that area, regardless of the starting point. -- Jens Axboe
