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Chris LuandGitHub
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* filer: re-list a folder after deleting it, and put it back if it is not empty The emptiness check inside the delete and the removal of the folder entry are not atomic, so an entry can land between them and be left reachable by its own path but out of every listing. Looking again after the delete catches the ones whose create event has not arrived yet, and does not depend on the event stream or on the observation window holding. * filer: create the directories holding an entry after the entry A parent checked before the insert can be taken by the empty-folder cleaner before the entry lands, which leaves the entry reachable by its own path but out of every listing. Creating the parents afterwards cannot be undone by a delete that was authorised before the insert, and pairs with the cleaner re-listing after its own delete: whichever of the two acts second sees what the other did. Going second means the entry is already stored when the parent fails, so it is taken back out and the caller still sees the error it used to get. * filer: narrow a directory that came back wider than the one it replaced A writer recreating its own missing parent has only the entry it is inserting to go on, so the directory it mints can grant access the deleted one denied - a 0700 folder comes back 0751. The cleaner read the real attributes before deleting, so its restore now puts the original mode back instead of leaving the inferred one in place. It only ever narrows, so a directory deliberately tightened since is left as it is.