flan
0d04c2cd1c
A reboot mid-backup orphaned the entire tree, permanently. The sidecar is the record of which snapshots a run pinned -- and /run is tmpfs. A reboot or crash between the recursive snapshot and its cleanup destroyed that record, leaving one snapshot per descendant dataset (250+ on a real pool) with nothing pointing at them. Nothing would ever have found them. gc_stale_snapshots() identifies leftovers by NAME, so it works when the record is gone. It runs after the sidecar reclaim -- the recorded path stays authoritative and the collector only mops up what the record lost. It deletes data on a name match, which is a weaker claim than a recorded fact, so the selection is a pure function with the harshest tests here. A snapshot is collected only if the name is exactly <dataset>@<task>-<YYYYMMDDHHMMSS>, it is not the current run's, NOTHING IS MOUNTED FROM IT (this, not the age guard, is what protects a concurrent backup), and it is over an hour old. Checked against the real pool: of 4728 snapshots including 2341 periodic ones, it selects exactly the orphans of the task being run and nothing else.