[LU-18076] add mechanisms to get client UUID from mountpoint

• Type: Improvement
• Resolution: Unresolved
• Priority: Minor
• Labels: easy
• Severity: 3
• Assignee: Emoly Liu
• Reporter: Andreas Dilger

Description

The client mountpoint UUID is used in some parts of the code to uniquely identify the client mountpoint to the server, in case there are multiple (distinct) mounts of the same filesystem on a single client. This mountpoint UUID is shown in the client llite.*.uuid file, all mdc.*.uuid, and osc.*.uuid parameters, as well as on the server in obdfilter,mdt.*.exports.*.export

It would be useful to have a mechanism to get the client mountpoint UUID directly from the mountpoint, rather than only from llite.*.uuid. Otherwise, it is necessary to get this indirectly via "lfs getname" to find the mount instance, and then "llite.INSTANCE.uuid" to get the UUID.

The lfs getname command should add a "-u" option to print the mountpoint UUID that can be fetched from the mountpoint (or any file) via a new OBD_IOC_GETUUID = _IOR('f', 127, char[UUID_MAX]) ioctl (for both files and directories), and there should also be a virtual MOUNTPOINT/.lustre/uuid file that prints the UUID for that specific mountpoint.

Issue Links

• is related to: LU-13118 change client instance to respect ASLR