[PATCH] mempool_resize and sanity checks

[Balbir Singh]

In mempool_resize(), I plan to replace the calls
to spin_unlock_irqrestore() -> pool_free -> spin_lock_
irqsave with the new sequence. The newer code
has fewer calls to spin_lock_irqsave and spin_unlock_
restore(). I think the new code should execute faster.

I have tested this code on a UP, if somebody could
test the patch on an SMP box and let me know if it
works, I would be thankful. I also have a sample test
case that uses mempool_resize().

I have also added the BUG_ON sanity checks in
mempool_create().

New Code

if (new_min_nr < pool->min_nr) {
        pool->min_nr = new_min_nr;
        /*      
         * Free possible excess elements.
         */      
        INIT_LIST_HEAD(&tmp_pool_to_free);
        while (pool->curr_nr > pool->min_nr) {
                tmp = pool->elements.next;
                if (tmp == &pool->elements)
                        BUG();  
                list_del(tmp);
                list_add(tmp, &tmp_pool_to_free);
                pool->curr_nr--;
        }       
        spin_unlock_irqrestore(&pool->lock, flags);

        list_for_each(tmp, &tmp_pool_to_free) {
                element = tmp;
                pool->free(element, pool->pool_data);
        }       
        return; 
}       

Original Code

if (new_min_nr < pool->min_nr) {
        pool->min_nr = new_min_nr;
        /*
         * Free possible excess elements.
         */
        while (pool->curr_nr > pool->min_nr) {
                tmp = pool->elements.next;
                if (tmp == &pool->elements)
                        BUG();
                list_del(tmp);
                element = tmp;
                pool->curr_nr--;
                spin_unlock_irqrestore(&pool->lock,
flags);

                pool->free(element, pool->pool_data);

                spin_lock_irqsave(&pool->lock, flags);
        }
        spin_unlock_irqrestore(&pool->lock, flags);
        return;
}

Diffs are attached.

Balbir

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