The following patches fix two problems I have been seeing in Red Hat bugzillas. The patches are made over scsi-misc, but except for 0006-block-and-drivers-separate-failfast-into-multiple-b.patch they could also apply over scsi-rc-fixes or linus's tree. 0006-block-and-drivers-separate-failfast-into-multiple-b.patch has a patch to convert the scsi dh modules so that is why it does not apply to the other kernels. The first problem is that when a transport problem is detected and the classes/drivers block the scsi_devices, there is IO in the driver and IO in the scsi_device queues. For fibre we have the fast IO fail tmo infrastructure to allow us to get IO in the driver up to multipath, but IO in the queues remains until the dev_loss_tmo fires. The difference between the timers can be minutes, so it looks like hang to the application. iSCSI has something similar to FC's fast io fail tmo, but it is called the replacment timeout. With this we will fail all IO that is in the driver or queued or any incoming IO. The first 5 patches try to provide common behavior: 0001-scsi-add-transport-host-byte-errors-v2.patch 0002-iscsi-class-libiscsi-and-qla4xxx-convert-to-new-tr.patch 0003-fc-class-Add-support-for-new-transport-errors.patch 0004-qla2xxx-use-new-host-byte-transport-errors.patch 0005-lpfc-start-to-use-new-trasnport-errors.patch Basically, when we block a device we fail IO with DID_TRANSPORT_DISRUPTED. When the fast io transport timer fires we fail IO with DID_TRANSPORT_FAILFAST. I converted qla2xxx and tried to convert lpfc (I was not sure about some of the errors). zfcp and mpt need to be converted, but it looked like they would be ok with the patches below. I could only test qla2xxx and lpfc though. The second problem is that multipath is not really good at handling a lot of errors. It just retries all errors on a different path, so for transport errors it makes a lot of sense to send them up to us pretty quickly. But device errors or driver errors or weird ones inbetween the scsi layer is better at handling them because the multipath layer does not know anything about scsi details. The patches: 0006-block-and-drivers-separate-failfast-into-multiple-b.patch 0007-scsi-Support-fail-fast-bits.patch are really simple and just break up the FAILFAST bits into device, driver and transport bits, so the upper layer can ask the lower layers to only fail fast certain types of errors. For multipath we only set the transport fail fast bit, and I thought in the future maybe something like RAID would set the device failfast error and not want transport errors failed fast to it. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
