[LU-16218] allow lfs setstripe --comp-flags to separate prefrd and prefwr

Related — Mon, 22 Jan 2024 17:16:18 +0000

The initial implementation of "lfs setstripe ... --comp-flags=prefer" only allowed specifying a single "prefer" argument for a given mirror component, which would set both the "LCME_FL_PREF_RD" and "LCME_FL_PREF_WR" flags at the same time. This was done simply because there wasn't any good use case to expose two separate flag options to userspace (documentation, ease of use).

The client code checks PREF_RD appropriately when selecting a mirror to read, and the MDS/LOD checks PREF_WR appropriately when selecting a mirror to write, so it should be straight forward to add "--comp-flags [prefwr|prefrd]" parsing in "lfs setstripe" (comp_str2flags()) to set only the individual flags on a mirror. The "lfs getstripe" command (lcme_flags2str() should still print "prefer" if both flags are set (both for simplicity and compatibility), but should print either "prefrd" or "prefwr" if only one flag is set.

The lfs-getstripe.1, lfs-setstripe.1, and lfs-mirror-create.1 man pages should also be updated to document these new options.

Whamcloud Community JIRA

[LU-16218] allow lfs setstripe --comp-flags to separate prefrd and prefwr