Re: [ndctl RFC PATCH] ndctl/namespace: create namespaces greedily

On Wed, 2019-08-28 at 13:47 -0700, Scargall, Steve wrote: > Hi Jeff, > > The issue is more of repetition. On an 8-socket system, should a > user really be expected to type 'ndctl create-namespace' eight times > vs. running 'ndctl create-namespace --region=all' once? SAP HANA is > an example app the requires one namespace per region. Scripting is a > viable solution, but that requires somebody to write the script and do > all the error checking & handling. Each OEM/ISV/SysAdmin would have > their own script. Pushing the logic to ndctl seems to be a reasonable > approach and let the user handle any errors returned by ndctl. A scripted solution can indeed be really simple - e.g.: # while read -r region; do ndctl create-namespace --region="$region"; done < <(ndctl list --bus=nfit_test.0 -R | jq -r '.[].dev') { "dev":"namespace5.0", "mode":"fsdax", "map":"dev", "size":"62.00 MiB (65.01 MB)", "uuid":"c8014457-c268-4f22-8eae-6386fbf08ceb", "sector_size":512, "align":2097152, "blockdev":"pmem5" } { "dev":"namespace4.0", "mode":"fsdax", "map":"dev", "size":"30.00 MiB (31.46 MB)", "uuid":"f9498ef6-cdd6-46c7-95f1-86469546ecb9", "sector_size":512, "align":2097152, "blockdev":"pmem4" } > The ndctl-man-page implies the 'ndctl create-namespace --region=all' > feature exists today: > > -r, --region= > > A regionX device name, or a region id number. The keyword > all can be specified to carry out the operation on every region in the > system, optionally filtered by bus id (see --bus= option). > This is true, but unfortunately, the implementation has treated create- namespace as an exception to this since the start, and I agree with Jeff that changing its behavior now can cause other Hyrum's law-esqe [1] breakage. I think however it should be easy to make a compromise, and retain the legacy behavior of create-namespace, while creating a new create- namespace-greedy command with the new semantics.