• Eric W. Biederman's avatar
    proc: remove/Fix proc generic d_revalidate · 3790ee4b
    Eric W. Biederman authored
    Ultimately to implement /proc perfectly we need an implementation of
    d_revalidate because files and directories can be removed behind the back
    of the VFS, and d_revalidate is the only way we can let the VFS know that
    this has happened.
    
    Unfortunately the linux VFS can not cope with anything in the path to a
    mount point going away.  So a proper d_revalidate method that calls d_drop
    also needs to call have_submounts which is moderately expensive, so you
    really don't want a d_revalidate method that unconditionally calls it, but
    instead only calls it when the backing object has really gone away.
    
    proc generic entries only disappear on module_unload (when not counting the
    fledgling network namespace) so it is quite rare that we actually encounter
    that case and has not actually caused us real world trouble yet.
    
    So until we get a proper test for keeping dentries in the dcache fix the
    current d_revalidate method by completely removing it.  This returns us to
    the current status quo.
    
    So with CONFIG_NETNS=n things should look as they have always looked.
    
    For CONFIG_NETNS=y things work most of the time but there are a few rare
    corner cases that don't behave properly.  As the network namespace is
    barely present in 2.6.24 this should not be a problem.
    Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
    Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
    Cc: Pavel Emelyanov <xemul@openvz.org>
    Cc: "David S. Miller" <davem@davemloft.net>
    Cc: Herbert Xu <herbert@gondor.apana.org.au>
    Cc: Alexey Dobriyan <adobriyan@gmail.com>
    Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
    Cc: "Denis V. Lunev" <den@openvz.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    3790ee4b
generic.c 17 KB