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    SubjectRe: silent semantic changes with reiser4

    On Thu, 26 Aug 2004, Denis Vlasenko wrote:
    > Is it possible to sufficiently hide "dirs inside files"
    > so that old tools will be unable to see them?

    Certainly possible.

    > I just checked:
    > ls -d /foo does lstat64("/foo", ...)
    > ls -d /foo/ does lstat64("/foo", ...)
    > but
    > ls -d /foo/. does lstat64("/foo/.", ...)
    > Will it work out if "dir inside file" will only be visible when referred as "file/."?

    That would likely be the _easiest_ approach for the kernel, and does solve
    the problem with some apps knowingly removing the trailing '/'.

    Note that we could try this out with existing filesystems with very
    minimal changes:

    - make directory bind mounts work on top of files ("graft_tree()")
    - make open_namei() and friend _not_ do the mount-point following for the
    last component if it's a non-directory.
    - probably some trivial fixups I haven't thought about. There might be
    some places that use "S_ISDIR()" to check for whether something can be
    looked up, but the main path walking already just checks whether there
    is a ".lookup" operation or not.

    This would already allow people to "try out" how different applications
    would react to a file that can show up both as a directory and a file. The
    patch might end up being less than 25 lines or so, the difficulty is in
    finding all the right places.

    Al, anything I missed?

    (And yes, it's a quick hack, but it's a quick hack that would probably
    mimic a good part of what we would have to do internally in the VFS layer
    to support this notion anyway).

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      Last update: 2009-11-18 23:46    [W:2.911 / U:0.348 seconds]
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