[LU-5969] Create an LGPL version of liblustreapi

• Type: Improvement
• Resolution: Unresolved
• Priority: Major
• Affects Version/s: Lustre 2.7.0
• Assignee: Hongchao Zhang
• Reporter: Frank Zago (Inactive)

Description

Cray would like to have an LGPL version of the liblustreapi
library. We believe that there is also a desire in the
community to do that move also.

A starting point would be to create that new library with the existing
code already licensed under the LGPL (such as HSM and layout), and
start from there.

We should take this opportunity to do some cleanup in the library, and
start a new one, independent of the older code. Some of the things
that we propose are:

• prefix all API functions with lustre_, as opposed to llapi_

• have a better API to work with the copytool and changelog
  readers. As these programs know which filesystem they are dealing
  with, there could be an lustre_open_fs / lustre_close_fs type of
  API, which would prevent calls to function such as get_root_path for
  every request. The HSM API already has something similar, and should
  be reused.

• every function must have a test. Currently the liblustreapi is only
  tested indirectly with program like lfs, and that's not good enough.

• every function must have a comment describing what it does, its
  parameters and return code. This is done for some but not all
  functions the existing library.

As a test of the viability for this plan, we'd like to first port the
posix tool to this new API. Currently, besides the API already in some
LGPLed source files, the following functions and their dependencies are needed:

       get_param
       get_root_path
       libcfs_ukuc_get_rfd
       libcfs_ukuc_msg_get
       libcfs_ukuc_start
       libcfs_ukuc_stop
       llapi_chomp_string
       llapi_create_volatile_idx
       llapi_error
       llapi_error_callback_set
       llapi_fd2fid
       llapi_fid2path
       llapi_file_open_pool
       llapi_get_agent_uuid
       llapi_get_mdt_index_by_fid
       llapi_msg_set_level
       llapi_open_by_fid
       llapi_parse_size
       llapi_search_fsname
       llapi_search_mounts

Cray would like to do the preliminary implementation of this new library, and would like to know if the copyright holders of the above mentioned functions agree to relicense their code under the LGPL. Otherwise they will have to be recoded.

The second phase would be to also port Robinhood to it, since the most
of the API should be there already, except for the changelog
processing.

Issue Links

• is duplicated by: LU-5712 Derive LGPL library from libcfs
• is related to: LU-6202 clean up ioctl handling
• is related to: LU-8282 missing trailing newline when getting Lustre version param
• is related to: LU-9897 Tracking of lustre library improvements.
• is related to: LU-1707 Add llapi_* function to return the OST/MDT count for a path.
• is related to: LU-3602 make utility functions availalbe to user space
• is related to: LU-6613 lib-dlc.h is under LGPLv3