Re: [PATCH] Add SELinux module to 2.5.74-bk1

[Andrew Morton <akpm@osdl.org>]

James Morris <jmorris@intercode.com.au> wrote:
>
> +int hashtab_replace(struct hashtab *h, void *key, void *datum,
>  +		    void (*destroy)(void *k, void *d, void *args),
>  +		    void *args)
>  +{
> ...
>  +		newnode = kmalloc(sizeof(*newnode), GFP_KERNEL);

>From an API perspective, the GFP_KERNEL is a problem.  Particularly as this
code seems to require that the caller perform the locking?

The GFP_KERNEL means that the locking _has_ to be via a sleeping lock
rather than a spinlock, and interrupt-time insertions are not possible.

Would be better to pass in the gfp_flags.


Comparing the complexity (size) of this code with the q-n-d hash tables
which are currently used one does wonder how useful it all will be.  The
additional indirections are not needed with q-n-d hashes.

But if it doesn't significantly add to the overall selinux patch then I
guess it makes sense.


A slab cache for hashtab_nodes would probably save a bit of space.


otoh: It would be faster and more space-efficient to require that the
clients of ths code embed a hastab_node inside their structures and just
pass the address of that hastab_node into here.  When they do a lookup they
retreive their original struct with container_of.  That fixes the GFP_KERNEL
thing too.