On Fri, 2018-02-02 at 15:08 +0100, Roman Pen wrote:
> +static inline struct ibtrs_tag *
> +__ibtrs_get_tag(struct ibtrs_clt *clt, enum ibtrs_clt_con_type con_type)
> +{
> +     size_t max_depth = clt->queue_depth;
> +     struct ibtrs_tag *tag;
> +     int cpu, bit;
> +
> +     cpu = get_cpu();
> +     do {
> +             bit = find_first_zero_bit(clt->tags_map, max_depth);
> +             if (unlikely(bit >= max_depth)) {
> +                     put_cpu();
> +                     return NULL;
> +             }
> +
> +     } while (unlikely(test_and_set_bit_lock(bit, clt->tags_map)));
> +     put_cpu();
> +
> +     tag = GET_TAG(clt, bit);
> +     WARN_ON(tag->mem_id != bit);
> +     tag->cpu_id = cpu;
> +     tag->con_type = con_type;
> +
> +     return tag;
> +}
> +
> +static inline void __ibtrs_put_tag(struct ibtrs_clt *clt,
> +                                struct ibtrs_tag *tag)
> +{
> +     clear_bit_unlock(tag->mem_id, clt->tags_map);
> +}
> +
> +struct ibtrs_tag *ibtrs_clt_get_tag(struct ibtrs_clt *clt,
> +                                 enum ibtrs_clt_con_type con_type,
> +                                 int can_wait)
> +{
> +     struct ibtrs_tag *tag;
> +     DEFINE_WAIT(wait);
> +
> +     tag = __ibtrs_get_tag(clt, con_type);
> +     if (likely(tag) || !can_wait)
> +             return tag;
> +
> +     do {
> +             prepare_to_wait(&clt->tags_wait, &wait, TASK_UNINTERRUPTIBLE);
> +             tag = __ibtrs_get_tag(clt, con_type);
> +             if (likely(tag))
> +                     break;
> +
> +             io_schedule();
> +     } while (1);
> +
> +     finish_wait(&clt->tags_wait, &wait);
> +
> +     return tag;
> +}
> +EXPORT_SYMBOL(ibtrs_clt_get_tag);
> +
> +void ibtrs_clt_put_tag(struct ibtrs_clt *clt, struct ibtrs_tag *tag)
> +{
> +     if (WARN_ON(!test_bit(tag->mem_id, clt->tags_map)))
> +             return;
> +
> +     __ibtrs_put_tag(clt, tag);
> +
> +     /*
> +      * Putting a tag is a barrier, so we will observe
> +      * new entry in the wait list, no worries.
> +      */
> +     if (waitqueue_active(&clt->tags_wait))
> +             wake_up(&clt->tags_wait);
> +}
> +EXPORT_SYMBOL(ibtrs_clt_put_tag);

Do these functions have any advantage over the code in lib/sbitmap.c? If not,
please call the sbitmap functions instead of adding an additional tag allocator.

Thanks,

Bart.

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