Re: Union mount and overlayfs bake off?

From: Miklos Szeredi
Date: Thu Jun 30 2011 - 08:44:22 EST


David Howells <dhowells@xxxxxxxxxx> writes:

> I've been dealing with some of Al's issues with the unionmount
> patches, but I know he's got more - I just can't remember them all.

A couple of questions I have:

1) What happens to the union in a cloned namespace (CLONE_NEWNS)?

2) What's the overhead for non-unioned filesystems if CONFIG_UNION_MOUNTS
is enabled? Does it show up in any microbenchmarks?

3) Is there a future strategy for making atomic operations really atomic?
E.g. what happens if power is lost in the middle of a copy-up? Or if
whiteout of source fails after a successful rename()?

4) Have you looked at overlayfs? Do you have any thoughts about the
relative merrits of each solution?

Thanks,
Miklos
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