Replace parjob's return-0 stub with a real multi-host allocator: for each
candidate plan, walk buckets in the given (descending) order, claiming a
distinct host per bucket via a fresh host_iter excluding hosts already
claimed elsewhere in the same plan attempt. On a bucket failure, reverse
every earlier successful claim's provisional debit via
sched_ctx_uncommit_host() before advancing to the next plan (Req 4.2, 4.4,
4.5, 4.6, 4.7).
Fix parjob_prepare_allocation() to compute each bucket's want from that
bucket's own slot count (ctx->nslots) instead of a fixed value, and reset
ctx->alloc_req.host at the top of each bucket's scan so host_iter's
pre-filter can't inherit a stale want from a differently-sized prior
bucket (safe: sched_try_alloc_on_host_() always repopulates it from the
real per-bucket want before its own authoritative check runs).
Add a maxTasks<=1 guard matching Req 4 AC1's precondition, needed because
a snapshot-restored job with unpopulated maxTasks==0 (pre-existing,
tracked separately as bug-1767) would otherwise reach parjob's now-real
allocator instead of being silently ignored as before.
On full success, merges every claimed bucket into one xce_job_alloc_t via
make_job_alloc()'s existing runtime-sized host array, satisfying task
4.3's multi-host commit scope as well.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XYdtrEWWZfKRRGED7raEYg
Rongsong Shen
3d5e1c32c0