[openib-general] Re: [PATCH v2 4/7] AMSO1100 Memory Management.

[Andrew Morton]

On Wed, 07 Jun 2006 15:06:55 -0500
Steve Wise <swise at opengridcomputing.com> wrote:

> 
> +void c2_free(struct c2_alloc *alloc, u32 obj)
> +{
> +	spin_lock(&alloc->lock);
> +	clear_bit(obj, alloc->table);
> +	spin_unlock(&alloc->lock);
> +}

The spinlock is unneeded here.


What does all the code in this file do, anyway?  It looks totally generic
(and hence inappropriate for drivers/infiniband/hw/amso1100/) and somewhat
similar to idr trees, perhaps.

> +int c2_array_set(struct c2_array *array, int index, void *value)
> +{
> +	int p = (index * sizeof(void *)) >> PAGE_SHIFT;
> +
> +	/* Allocate with GFP_ATOMIC because we'll be called with locks held. */
> +	if (!array->page_list[p].page)
> +		array->page_list[p].page =
> +		    (void **) get_zeroed_page(GFP_ATOMIC);
> +
> +	if (!array->page_list[p].page)
> +		return -ENOMEM;

This _will_ happen under load.  What will the result of that be, in the
context of thise driver?

This function is incorrectly designed - it should receive a gfp_t argument.
Because you don't *know* that the caller will always hold a spinlock.  And
GFP_KERNEL is far, far stronger than GFP_ATOMIC.

> +static int c2_alloc_mqsp_chunk(gfp_t gfp_mask, struct sp_chunk **head)
> +{
> +	int i;
> +	struct sp_chunk *new_head;
> +
> +	new_head = (struct sp_chunk *) __get_free_page(gfp_mask | GFP_DMA);

Why is __GFP_DMA in there?  Unless you've cornered the ISA bus infiniband
market, it's likely to be wrong.