On Tue, 9 Jul 2024 16:30:53 +0000 Frank van der Linden <fvdl@xxxxxxxxxx> wrote:
> In addition to the number of allocations and releases, system
> management software may like to be aware of the size of CMA
> areas, and how many pages are available in it. This information
> is currently not available, so export it in total_page and
> available_pages, respectively.
>
> The name 'available_pages' was picked over 'free_pages' because
> 'free' implies that the pages are unused. But they might not
> be, they just haven't been used by cma_alloc
>
> The number of available pages is tracked regardless of
> CONFIG_CMA_SYSFS, allowing for a few minor shortcuts in
> the code, avoiding bitmap operations.
>
> ...
>
> @@ -382,7 +383,7 @@ static void cma_debug_show_areas(struct cma *cma)
> {
> unsigned long next_zero_bit, next_set_bit, nr_zero;
> unsigned long start = 0;
> - unsigned long nr_part, nr_total = 0;
> + unsigned long nr_part;
> unsigned long nbits = cma_bitmap_maxno(cma);
>
> spin_lock_irq(&cma->lock);
> @@ -394,12 +395,12 @@ static void cma_debug_show_areas(struct cma *cma)
> next_set_bit = find_next_bit(cma->bitmap, nbits, next_zero_bit);
> nr_zero = next_set_bit - next_zero_bit;
> nr_part = nr_zero << cma->order_per_bit;
> - pr_cont("%s%lu@%lu", nr_total ? "+" : "", nr_part,
> + pr_cont("%s%lu@%lu", start ? "+" : "", nr_part,
> next_zero_bit);
> - nr_total += nr_part;
> start = next_zero_bit + nr_zero;
> }
Can you please explain the above change?
> - pr_cont("=> %lu free of %lu total pages\n", nr_total, cma->count);
> + pr_cont("=> %lu free of %lu total pages\n", cma->available_count,
> + cma->count);
> spin_unlock_irq(&cma->lock);
> }
>
> @@ -446,6 +447,10 @@ struct page *cma_alloc(struct cma *cma, unsigned long count,
>
> for (;;) {
> spin_lock_irq(&cma->lock);
> + if (count > cma->available_count) {
Right here would be a nice place for a comment?
> + spin_unlock_irq(&cma->lock);
> + break;
> + }
> bitmap_no = bitmap_find_next_zero_area_off(cma->bitmap,
> bitmap_maxno, start, bitmap_count, mask,
> offset);
