Re: [PATCH v5 05/10] mm/cma: Introduce cma_alloc_at() API

[David Hildenbrand (Arm)]

>  /* This part must be outside protection */> diff --git a/mm/cma.c b/mm/cma.c
> index a10ea37a261d..1e1ebae79090 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -936,6 +936,141 @@ struct page *cma_alloc_frozen_compound(struct cma *cma, unsigned int order)
>  	return __cma_alloc_frozen(cma, 1 << order, order, gfp);
>  }
>  
> +static int cma_range_alloc_at(struct cma *cma, struct cma_memrange *cmr,
> +			      unsigned long offset, unsigned long count,
> +			      struct page **pagep, gfp_t gfp)
> +{
> +	struct page *page = NULL;
> +	unsigned long pfn;
> +	int ret = -EBUSY;
> +
> +	spin_lock_irq(&cma->lock);
> +
> +	/*
> +	 * If the request is larger than the available number of pages, stop
> +	 * right away.
> +	 */
> +	if (count > cma->available_count)
> +		goto unlock;
> +
> +	ret = bitmap_allocate(cmr->bitmap, offset, count);
> +	if (ret < 0)
> +		goto unlock;
> +
> +	pfn = cmr->base_pfn + offset;
> +	page = pfn_to_page(pfn);
> +
> +	/*
> +	 * Do not hand out page ranges that are not contiguous, so
> +	 * callers can just iterate the pages without having to worry
> +	 * about these corner cases.
> +	 */
> +	if (!page_range_contiguous(page, count)) {
> +		pr_warn_ratelimited("%s: %s: skipping non-contiguous area [0x%lx-0x%lx]",
> +				    __func__, cma->name, pfn, pfn + count - 1);
> +		ret = -EBUSY;
> +		goto clear;
> +	}
> +
> +	cma->available_count -= count;
> +
> +	/*
> +	 * It's safe to drop the lock here. We've marked this region for
> +	 * our exclusive use. If the migration fails we will take the
> +	 * lock again and unmark it.
> +	 */
> +	spin_unlock_irq(&cma->lock);
> +
> +	mutex_lock(&cma->alloc_mutex);
> +	ret = alloc_contig_frozen_range(pfn, pfn + count, ACR_FLAGS_CMA, gfp);
> +	mutex_unlock(&cma->alloc_mutex);
> +

There is quite some code duplication with cma_range_alloc(). Please try harder
to factor common code out and reuse it.



> +	if (ret < 0)
> +		goto free;
> +
> +	*pagep = page;
> +
> +	return 0;
> +
> +free:
> +	/* we need to reacquire the lock to clean up the internal state */
> +	spin_lock_irq(&cma->lock);
> +	cma->available_count += count;
> +clear:
> +	bitmap_clear(cmr->bitmap, offset, count);
> +unlock:
> +	spin_unlock_irq(&cma->lock);
> +	return ret;
> +}
> +
> +static struct page *__cma_alloc_at_frozen(struct cma *cma, unsigned long offset,
> +					  unsigned long count, gfp_t gfp)
> +{
> +	const char *name = cma ? cma->name : NULL;
> +	struct page *page = NULL;
> +	int ret = -ENOMEM, r;
> +	unsigned long i;
> +
> +	if (!cma || !cma->count)
> +		return page;
> +
> +	pr_debug("%s(cma %p, name: %s, offset %lu, count %lu)\n", __func__,
> +		 (void *)cma, cma->name, offset, count);
> +
> +	if (!count)
> +		return page;
> +
> +	trace_cma_alloc_at_start(name, offset, count, cma->available_count,
> +				 cma->count);
> +
> +	for (r = 0; r < cma->nranges; r++) {
> +		page = NULL;
> +
> +		ret = cma_range_alloc_at(cma, &cma->ranges[r], offset, count,
> +					 &page, gfp);
> +		if (ret != -EBUSY || page)
> +			break;
> +	}
> +
> +	/*
> +	 * CMA can allocate multiple page blocks, which results in different
> +	 * blocks being marked with different tags. Reset the tags to ignore
> +	 * those page blocks.
> +	 */
> +	if (page) {
> +		for (i = 0; i < count; i++)
> +			page_kasan_tag_reset(page + i);
> +	}
> +
> +	if (ret && !(gfp & __GFP_NOWARN)) {
> +		pr_err_ratelimited("%s: %s: alloc failed, request: %lu, %lu pages, ret: %d\n",
> +				   __func__, cma->name, offset, count, ret);
> +		cma_debug_show_areas(cma);
> +	}
> +
> +	pr_debug("%s(): returned %p\n", __func__, page);
> +	trace_cma_alloc_at_finish(name, page ? page_to_pfn(page) : 0, page,
> +				  count, ret);
> +
> +	if (page) {
> +		count_vm_event(CMA_ALLOC_SUCCESS);
> +		cma_sysfs_account_success_pages(cma, count);
> +	} else {
> +		count_vm_event(CMA_ALLOC_FAIL);
> +		cma_sysfs_account_fail_pages(cma, count);
> +	}

Also here, way too much code duplication with __cma_alloc_frozen().

There must be a better way :)

(I really prefer this direction of the patch set)


-- 
Cheers,

David