[LU-18357] Support multiple filesets per nodemap

• Type: New Feature
• Resolution: Unresolved
• Priority: Minor
• Labels: nodemap
• Assignee: Marc Vef
• Reporter: Marc Vef

Description

Multiple filesets per nodemap would be beneficial. The filesets consist of one primary path and several alternate path for a given tenant's nodemap. The primary fileset (mostly) corresponds to the current implementation's single available fileset. The new features are outlined below:

• (new) The syntax for setting a fileset via lctl for a nodemap is extended:

lctl set_param nodemap.<name>.fileset=<primary_path>[:alternate_path_1][:alternate_path_2][:alternate_path_3]... 

• (new) A similar syntax is presented when printing the nodemap's fileset: lctl get_param nodemap.<name>.fileset
• (unchanged) If the client-specific mount subdirectory is empty or it corresponds to the primary fileset, the client is presented with the primary fileset as Lustre's root mount point.
• (new) If a client-specific mount subdirectory is not empty and not represented in any fileset, the subdirectory is appended to the primary fileset (if set) and used as Lustre's root mount point.
• (new) If a client-specific mount subdirectory is not empty and is represented in any fileset, it is used as Lustre's root mount point.
• Mounting fails if a path does not exist.