Re: [PATCH] symlink nesting level change

[Andrew Morton <akpm@osdl.org>]

On Wed, 3 May 2006 04:08:49 +0100
Al Viro <viro@ftp.linux.org.uk> wrote:

> No.  It's way past time to bump it to 8.  Everyone had been warned - for
> months now.
> 
> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
> ----
> --- a/include/linux/namei.h	2006-03-31 20:08:42.000000000 -0500
> +++ b/include/linux/namei.h	2006-05-02 23:06:46.000000000 -0400
> @@ -11,7 +11,7 @@
>  	struct file *file;
>  };
>  
> -enum { MAX_NESTED_LINKS = 5 };
> +enum { MAX_NESTED_LINKS = 8 };
>  
>  struct nameidata {
>  	struct dentry	*dentry;

It's a non-back-compatible change which means that people will install
2.6.18+, will set stuff up which uses more that five nested links and some
will discover that they can no longer run their software on older kernels.

It'll only hurt a very small number of people, but for those people, it
will hurt a lot.  And I can't really think of anything we can do to help
them, apart from making the new behaviour runtime-controllable, defaulting
to "off", but add a once-off printk when we hit MAX_NESTED_LINKS, pointing
them at a document which tells them how to turn on the new behaviour and
which explains the problems.  Which sucks.

But I guess as major distros are 2.6.16-based, this is a good time to make
this change.