Re: vode to pathname

From: Robert Watson (rwatson_at_FreeBSD.org)
Date: 08/25/05

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    Date: Thu, 25 Aug 2005 06:17:32 +0100 (BST)
To: Dag-Erling Smørgrav <des@des.no>

    On Wed, 24 Aug 2005, Dag-Erling Smørgrav wrote:

    > "Kamal R. Prasad" <kamalpr@yahoo.com> writes:
    >> So the question is, how do I get hold of pathname given
    >> vnode*/(inode, devno, generation no) -without relying on the name
    >> cache (on freebsd)?
    >
    > You can't. The semantics of Unix file systems are such that the mapping
    > from file name to file is one-way. Furthermore, a file can be
    > associated with more than one file name, or even none at all (if it has
    > been unlinked but is still held open by a process).

    In fact, there's another troublesome edge case -- different files can also
    return the same name, if you have a way to generate names from linked
    files, due to mountpoint covering. Covered vnodes can still be accessed
    after the mount, if they have been opened, or if the cwd of a process is a
    directory (other than the mountpoint vnode) of the covered file system,
    and an identically named node can exist in the covering file system.

    Robert N M Watson

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