Motivation:

log->tmp_fileid (src/log/log_private.h) is a shared counter that hands out unique temporary-file ids when threads prepare log files. Its only use (src/log/log.c, _wti_log_allocfile) is a sequentially consistent _wt_atomic_add_uint32:

tmp_id = __wt_atomic_add_uint32(&log->tmp_fileid, 1);

Uniqueness comes from the atomic RMW being indivisible, which holds at any memory order; the counter gates no other memory. Relaxed ordering is therefore sufficient, and it matches the log->fileid counter which was made relaxed in WT-16301.

This is a code-quality micro-optimization, not a bug: sequential consistency is a safe superset, so the current code is correct.

Tasks:

• Change the tmp_fileid increment to __wt_atomic_add_uint32_relaxed.
• Remove the FIXME referencing this ticket added in WT-16301.

Definition of Done:

• log->tmp_fileid uses relaxed ordering.
• No functional or behavioral change.