fscache's Remove drops the in-memory entry, releases the lock, and only then
unlinks - blocking until every outstanding reader closes. A Get landing in that
window re-creates the file at the same path under a fresh entry, and the deferred
unlink deletes those new bytes. The entry survives pointing at nothing, and since
a present entry is treated as a hit, every later Get for that key returns ENOENT
for the rest of the process's life. Only a restart, which rebuilds the map from
disk, cleared it.
Get now drops such an entry and retries once, so a vanished data file costs one
re-fetch instead of poisoning the key permanently. This also covers a file
disappearing for reasons unrelated to that race, such as external deletion or a
restored backup.
Specs cover an in-process entry, one adopted at startup, and the deferred-removal
race itself.
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