Re: [PATCH vfs 1/2] lib: implement ptrset

[Azat Khuzhin <a3at.mail@gmail.com>]

On Thu, Nov 13, 2014 at 05:09:27PM -0500, Tejun Heo wrote:
> +int ptrset_add(void *ptr, struct ptrset *set, gfp_t gfp)
> +{
> +	struct ptrset_elem *elem;
> +	struct rb_node *parent, **slot;
> +
> +	elem = kmalloc(sizeof(*elem), gfp);
> +	if (!elem && !in_interrupt())	/* see ptrset_preload() */
> +		elem = this_cpu_xchg(ptrset_preload_elem, NULL);
> +	if (!elem)
> +		return -ENOMEM;
> +	elem->ptr = ptr;
> +
> +	if (ptrset_find_slot(elem->ptr, set, &slot, &parent)) {
> +		kfree(elem);
> +		return -EEXIST;
> +	}

Maybe allocation *after* ptrset_find_slot() will be better?
This will avoid extra kmalloc/kfree if such ptr already exist (and also
will avoid ENOMEM for such cases).