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.
