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    SubjectRe: [PATCH 0/7] overlay filesystem v9
    Andy Whitcroft <> writes:

    > On Tue, May 17, 2011 at 02:30:45PM +0200, Miklos Szeredi wrote:
    >> Here's an updated version of the overlay filesystem.
    >> Git tree is here:
    >> git:// overlayfs.v9
    > Ok I pulled this into the Ubuntu kernel and made an Ubuntu Live CD
    > for testing. Overall it worked pretty well, no hangs, no crashes,
    > performance seemed reasonable. We hit one issue with hard links which
    > fail to be possible on overlayfs mounts when the Yama LSM (out of tree)
    > is enabled. This module applies more aggressive checks on hard-links
    > preventing links to files you cannot read.

    Great, thanks for testing.

    > The bug seems to be related to the way we handle user and group owners for
    > the overlayfs inodes, which we do not initialise (and they remain as 0,0).
    > While these ownerships are never exposed to userspace they are exposed
    > to the LSM layer, and the LSM module checks the wrong owner and fails
    > to allow the links.


    > From what I can see it is completly reasonable to initialise the ownership
    > fields in the overlayfs inode from the underlying inode, or for new files
    > ones initialise it in the normal way based on the containing directory.
    > Now I am nothing like a filesystems expert but looking at what other
    > filesystems do I think the patch below is sufficient, but certainly it
    > needs some sanity checking. At least it fixes all the issues I see
    > here.

    Forgot to attach the patch?

    > With this in place I have been able to boot a Natty release live CD
    > image, and upgrade it in place to the latest and greatest of everything.
    > Very nice. Thanks for your work continuing work on overlayfs. It is
    > starting to look good enough to merge.
    > Comments?

    I'd be happier if the LSM module were fixed not to peek inside the inode
    structure. Some filesystems (notably network ones) do not guarantee i_*
    to be up-to-date, relying on these is not a good idea.


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      Last update: 2011-05-19 19:47    [W:0.027 / U:2.284 seconds]
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