wfs.Create defers the filer create to Flush and inserts a local-only
placeholder into the metaCache (dirtyMetadata=true), so a just-created file
exists locally before the filer has it. When the parent directory falls out of
cache (hot-dir read-through, idle evict) and is rebuilt, EnsureVisited wipes the
store and refills from a filer listing that does not yet include the un-flushed
create, then markCachedFn publishes the directory authoritatively cached without
it. lookupEntry then returns an authoritative ENOENT and ReadDir returns nothing
— the file disappears from the mount although the client created it. Under
concurrent read+write churn on one directory this is the ConcurrentReadWrite
flake.
Preserve children the mount flags as local-only (open dirty handle or pending
async flush — the signal lookupEntry already trusts) across the rebuild's wipe
instead of blind-deleting them. Unpinned stale children are still dropped so a
rebuild cannot resurrect a deleted entry.