On 2017/10/28 15:42, Christoph Hellwig wrote: > On Sat, Oct 28, 2017 at 03:20:07PM +0800, Guan Junxiong wrote: >> Think of some current advanced features of DM-Multipath combined with multipath-tools >> such as path-latency priority grouping, intermittent IO error accounting for path >> degradation, delayed or immediate or follow-over failback feature. >> Those features, which is significant in some scenario, need to use per-controller block devices. >> Therefore, I think it is worthy adding a CONFIG_NVME_MULTIPATHING knob to >> hide or show per-controller block devices. >> >> How about let me to add this this CONFIG_NVME_MULTIPATHING knob? > > There is defintively not going to be a run-time nob, sorry. You've > spent this work on dm-multipath after the nvme group pretty clearly > said that this is not what we are going to support, and we have not > interest in supporting this. Especially as proper path discovery, > asymetic namespaces states and similar can only be supported properly > with the in-kernel code. > Does it mean some extra works such as: 1) showing the path topology of nvme multipath device 2) daemon to implement immediate and delayed failback 3) detecting sub-healthy path due to shaky link 4) grouping paths besides ANA ... and so on, need to integrate into the user-space tool such as nvme-cli or a new invented user-space tool named "nvme-mpath" ? Which do you prefer? And the kernel also needs to export more setting and getting methods. Regards Guan .
