[LU-14084] change 'lfs migrate' to use 'MIGRATION_NONBLOCK' by default

• Type: Improvement
• Resolution: Unresolved
• Priority: Minor
• Assignee: WC Triage
• Reporter: Andreas Dilger

Description

Since Lustre 2.8 (patch https://review.whamcloud.com/16238 "LU-6785 utils: compatibility fix for lfs migrate") "lfs migrate" has used "--block" as the default (i.e. block writes to a file during migration) for compatibility with pre-2.8.0 servers (or earlier for EE releases).

Since very few servers are this old, it would be better to change the default to try and get the file lease first unless a new migration_flags = MIGRATION_BLOCK flag is set, and only try the grouplock if the lease fails and migration_flags = MIGRATION_NONBLOCK is not set.

This will also solve the problem that "lfs migrate" without the "--non-block" option fails for DoM files until patch https://review.whamcloud.com/39406 "LU-13645 ldlm: group locks for DOM IBIT lock" is landed (which is having some headwind itself):

lfs migrate: cannot get group lock: Invalid argument

This would also be less complex/risky to backport to 2.12.

It would also be useful to consolidate the migrate_block() and migrate_nonblock() code if possible, instead of having two nearly-identical functions.

Issue Links

• is related to: LU-13645 Various data corruptions possible in lustre.
• is related to: LU-6785 Interop 2.7.0<->master sanity test_56w: cannot swap layouts: Device or resource busy