On 09/25/2017 09:09 AM, Sagi Grimberg wrote: > > > On 25/09/17 08:59, Hannes Reinecke wrote: >> On 09/25/2017 07:37 AM, Sagi Grimberg wrote: >>> >>>> So why exposing it then in the first time? I know you don't want >>>> dm-mpath in >>>> NVMe (neither do I) but we have to have something until your patchset >>>> and ANA >>>> is merged. And with this patch it's trivial to build a path checker >>>> that just >>>> looks at the state attribute in sysfs. >>> >>> Can't we just not use path-checkers for nvme (we already have one in >>> nvme)? >> >> Really? For NVMe? >> How would you do that, then? > > Quick and dirty is to have a path-checker that returns path-up always, > when the path go down, nvme will detect it and fast-fail the io. > Well, yes; that's the trivial part. But how do you know the path has become LIVE again?
>> Anyway: the entire point is that you don't _need_ a path checker for >> NVMe. >> The primary reason for path checkers is to check with the transport >> layer if the remote endpoint is reachable. >> (I know, that's not quite what they're doing now, but that's beside the >> point). >> For NVMf we do have KATO, so the NVMe subsystem knows exactly if the >> connection is live or not. So it should be perfectly sufficient to check >> the connection state instead of running a path checker of sorts. >> But for doing so we need something in sysfs which we could check. >> >> Mind you, I wouldn't be adverse to have some common sysfs attribute, >> with some common values (eg path up, path down, path blocked), and have >> NVMf translating the internal state into that. > > We could have such an interface I assume. But it would suck to maintain > yet another state (we are already having enough trouble to have a > coherent controller state machine). Weell ... we could be using a notifier chain for that. I think I should post my patchset. Cheers, Hannes -- Dr. Hannes Reinecke Teamlead Storage & Networking h...@suse.de +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton HRB 21284 (AG Nürnberg)
