On 9/26/23 7:57 AM, Wenchao Hao wrote: > On 2023/9/26 1:54, Mike Christie wrote: >> On 9/25/23 10:07 AM, Wenchao Hao wrote: >>> On 2023/9/25 22:55, Christoph Hellwig wrote: >>>> Before we add another new error handling mechanism we need to fix the >>>> old one first. Hannes' work on not passing the scsi_cmnd to the various >>>> reset handlers hasn't made a lot of progress in the last five years and >>>> we'll need to urgently fix that first before adding even more >>>> complexity. >>>> >>> I observed Hannes's patches posted about one year ago, it has not been >>> applied yet. I don't know if he is still working on it. >>> >>> My patches do not depend much on that work, I think the conflict can be >>> solved fast between two changes. >> >> I think we want to figure out Hannes's patches first. >> >> For a new EH design we will want to be able to do multiple TMFs in parallel >> on the same host/target right? >> > > It's not necessary to do multiple TMFs in parallel, it's ok to make sure > each TMFs do not affect each other. > > For example, we have two devices: 0:0:0:0 and 0:0:0:1 > > Both of them request device reset, they do not happened in parallel, but > would in serial. If 0:0:0:0 is performing device reset in progress, 0:0:0:1 > just wait 0:0:0:0 to finish. I see. I guess we still get the benefit of not having to stop other devices when doing TMFs. I think we still want a common way to allocate/free and manage resources drivers will use during this time. Maybe have a init_device/target/cmd/eh_priv and exit_device/target/eh_priv (I'm not sure of the name, but something similar to the init_cmd_priv/exit_cmd_priv we have for normal commands. scsi-ml then calls into the new eh with the priv data. Drivers don't have to do the preallocation and worry if it's per device/target/host. I'm not 100% sure about the low level details. Check out how Hannes's is handling tag management for TMFs as well. > >> The problem is that we need to be able to make forward progress in the EH >> path and not fail just because we can't allocate memory for a TMF related >> struct. To accomplish this now, drivers will use mempools, preallocate TMF >> related structs/mem/tags with their scsi_cmnd related structs, preallocate >> per host/target/device related structs or ignore what I wrote above and just >> fail. >> >> Hannes's patches fix up the eh callouts so they don't pass in a scsi_cmnd >> when it's not needed. That seems nice because after that, then for your new >> EH we can begin to standardize on how to handle preallocation of drivers >> resources needed to perform TMFs for your new EH. It could be a per >> device/target/host callout to allow drivers to preallocate, then scsi-ml calls >> into the drivers with that data. It doesn't have to be exactly like that or >> anything close. It would be nice for drivers to not have to think about this >> type of thing and scsi-ml just to handle the resource management for us when >> there are multiple TMFs in progress. >> >
