• U
    [PATCH] Implement AT_SYMLINK_FOLLOW flag for linkat · 45c9b11a
    Ulrich Drepper 提交于
    When the linkat() syscall was added the flag parameter was added in the
    last minute but it wasn't used so far.  The following patch should change
    that.  My tests show that this is all that's needed.
    
    If OLDNAME is a symlink setting the flag causes linkat to follow the
    symlink and create a hardlink with the target.  This is actually the
    behavior POSIX demands for link() as well but Linux wisely does not do
    this.  With this flag (which will most likely be in the next POSIX
    revision) the programmer can choose the behavior, defaulting to the safe
    variant.  As a side effect it is now possible to implement a
    POSIX-compliant link(2) function for those who are interested.
    
      touch file
      ln -s file symlink
    
      linkat(fd, "symlink", fd, "newlink", 0)
        -> newlink is hardlink of symlink
    
      linkat(fd, "symlink", fd, "newlink", AT_SYMLINK_FOLLOW)
        -> newlink is hardlink of file
    
    The value of AT_SYMLINK_FOLLOW is determined by the definition we already
    use in glibc.
    Signed-off-by: NUlrich Drepper <drepper@redhat.com>
    Acked-by: NAl Viro <viro@zeniv.linux.org.uk>
    Signed-off-by: NAndrew Morton <akpm@osdl.org>
    Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
    45c9b11a
namei.c 66.5 KB