On Fri, May 11, 2018 at 5:05 AM, Keith Busch <keith.busch@xxxxxxxxxxxxxxx> wrote: > On Fri, May 11, 2018 at 04:52:11AM +0800, Ming Lei wrote: >> Hi Keith, >> >> On Tue, May 8, 2018 at 11:30 PM, Keith Busch <keith.busch@xxxxxxxxx> wrote: >> > On Sat, Apr 28, 2018 at 11:50:17AM +0800, Ming Lei wrote: >> >> This sync may be raced with one timed-out request, which may be handled >> >> as BLK_EH_HANDLED or BLK_EH_RESET_TIMER, so the above sync queues can't >> >> work reliably. >> > >> > Ming, >> > >> > As proposed, that scenario is impossible to encounter. Resetting the >> > controller inline with the timeout reaps all the commands, and then >> > sets the controller state to RESETTING. While blk-mq may not allow the >> > driver to complete those requests, having the driver sync with the queues >> > will hold the controller in the reset state until blk-mq is done with >> > its timeout work; therefore, it is impossible for the NVMe driver to >> > return "BLK_EH_RESET_TIMER", and all commands will be completed through >> > nvme_timeout's BLK_EH_HANDLED exactly as desired. >> >> That isn't true for multiple namespace case, each request queue has its >> own timeout work, and all these timeout work can be triggered concurrently. > > The controller state is most certainly not per queue/namespace. It's > global to the controller. Once the reset is triggered, nvme_timeout can > only return EH_HANDLED. One exception is PCI error recovery, in which EH_RESET_TIMER still may be returned any time. Also the two timeout can happen at the same time from more than one NS, just before resetting is started(before updating to NVME_CTRL_RESETTING). OR one timeout is from admin queue, another one is from NS, both happen at the same time, still before updating to NVME_CTRL_RESETTING. In above two situations, one timeout can be handled as EH_HANDLED, and another can be handled as EH_RESET_TIMER. So it isn't enough to drain timeout by blk_sync_queue() simply. Thanks, Ming Lei
