On 03/22/2017 11:58 AM, Keith Busch wrote: > On Tue, Mar 21, 2017 at 11:03:59PM -0400, Jens Axboe wrote: >> On 03/21/2017 10:14 PM, Ming Lei wrote: >>> When iterating busy requests in timeout handler, >>> if the STARTED flag of one request isn't set, that means >>> the request is being processed in block layer or driver, and >>> isn't submitted to hardware yet. >>> >>> In current implementation of blk_mq_check_expired(), >>> if the request queue becomes dying, un-started requests are >>> handled as being completed/freed immediately. This way is >>> wrong, and can cause rq corruption or double allocation[1][2], >>> when doing I/O and removing&resetting NVMe device at the sametime. >> >> I agree, completing it looks bogus. If the request is in a scheduler or >> on a software queue, this won't end well at all. Looks like it was >> introduced by this patch: >> >> commit eb130dbfc40eabcd4e10797310bda6b9f6dd7e76 >> Author: Keith Busch <keith.busch@xxxxxxxxx> >> Date: Thu Jan 8 08:59:53 2015 -0700 >> >> blk-mq: End unstarted requests on a dying queue >> >> Before that, we just ignored it. Keith? > > The above was intended for a stopped hctx on a dying queue such that > there's nothing in flight to the driver. Nvme had been relying on this > to end unstarted requests so we may progress when a controller dies. > > We've since obviated the need: we restart the hw queues to flush entered > requests to failure, so we don't need that brokenness. Good, thanks for confirming, Keith. I queued up the patch for 4.11 this morning. -- Jens Axboe
