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    SubjectRe: [PATCH v2] ceph: fix posix ACL hooks
    On Mon, Feb 03, 2014 at 01:31:19PM -0800, Linus Torvalds wrote:

    > If the protocol is path-based (and it happens, and it's actually the
    > *correct* thing to do for a network filesystem, rather than the
    > idiotic "file handle" crap that tries to emulate the unix inode
    > semantics in the protocol), then the inode is simply not sufficient.
    >
    > And no, d_find_alias() is not correct or sufficient either. It can
    > work in practice (and probably does perfectly fine 99.9% of the time),
    > but it can equally well give the *wrong* dentry: yes, the dentry it
    > returns would have been a valid dentry for somebody at some time, but
    > it might be a stale dentry *now*, and it might be the wrong dentry for
    > the current user (because the current user may not have permissions to
    > that particular path, even if the user has permissions through his
    > *own* path).
    >
    > So I really think you're *fundamentally* incorrect when you say
    > "result *is* a function of inode alone".

    Which fs are you talking about? For 9P it *is* a function of inode alone.
    For CIFS there's no wrong dentry to pick - it doesn't have links to start
    with.

    If we really have hardlinks, the result of permission check would better
    be a function of inode itself - as in, "if it gives different results
    for two pathnames reachable for the same user, we have a bug".


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