Re: file as a directory

[Amit Gud <amitgud1@gmail.com>]

On Mon, 22 Nov 2004 20:05:25 +0100 (MET), Jan Engelhardt
<jengelh@linux01.gwdg.de> wrote:
> >>(Hint - "file as directory" broke a number of programs that didn't
> >>expect that a file *could* be a directory, when run on a reiser4
> >>filesystem...)
> >
> >It broke extraordinarily few.
> 
> (The fewer the better.)
> 
> That's good news, and frankly, I did not expect anything else. That's because
> either programs definitely know that "it" is a file/directory because they just
> mkdir'ed or so, or they implement correct error checks, e.g. the user just
> created a directory and we check back (i.e. race protection).
> 

Correct me if I'm wrong, but the best way I know whether a file should
be treated as directory or as a file (atleast how I've implemented it)
depends upon the context (how the file is accessed) in the user-space
and this context is reflected in the kernel space in the flags of the
struct nameidata. So ...

----
        /* check if the archive is a path component or if last
component with slash */
	flags = (nd->flags & LOOKUP_CONTINUE) || (nd->flags & LOOKUP_DIRECTORY);
        if(flags)
               /* directory */
        else
               /* file */

----

> What I am worried about is the opendir() libc call, which AFAIK does this:
>   fd = open("directory", myflags | O_DIRECTORY)
> 

No more worries! Am I missing something?

AG
--
May the source be with you.