Messages in this thread | | | From | "Stephen C. Tweedie" <> | Date | Tue, 23 Nov 1999 23:15:43 +0000 (GMT) | Subject | Re: Transparent mounts |
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Hi,
On Wed, 17 Nov 1999 15:26:44 -0800 (PST), Dan Hollis <goemon@anime.net> said:
> I dont know how BSD handles namespace collisions, but this could be > handled by hashing the duplicate filenames in some way.
It handles partially in user space. For lookups it is easy: you look up in the top layer before passing the request down, and if you see a whiteout directory entry (indicating the file has been deleted in the top layer but is still there underneath), you return ENOENT.
For readdir(), the entire directory stream for all layers in order is passed up to libc, which then removes duplicates. That's a little gross, but it is a lot less gross than most of the possible in-kernel alternatives. It's a reasonable way to do it.
--Stephen
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