linux-kernel - Re: [PATCHv22 13/16] drivers: add Contiguous Memory Allocator

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Date:	Tue, 21 Feb 2012 21:30:07 +0000 (UTC)
From:	Aaro Koskinen <aaro.koskinen@....fi>
To:	Marek Szyprowski <m.szyprowski@...sung.com>
cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-media@...r.kernel.org, linux-mm@...ck.org,
	linaro-mm-sig@...ts.linaro.org,
	Michal Nazarewicz <mina86@...a86.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Russell King <linux@....linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Daniel Walker <dwalker@...eaurora.org>,
	Mel Gorman <mel@....ul.ie>, Arnd Bergmann <arnd@...db.de>,
	Jesse Barker <jesse.barker@...aro.org>,
	Jonathan Corbet <corbet@....net>,
	Shariq Hasnain <shariq.hasnain@...aro.org>,
	Chunsang Jeong <chunsang.jeong@...aro.org>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Benjamin Gaignard <benjamin.gaignard@...aro.org>,
	Rob Clark <rob.clark@...aro.org>,
	Ohad Ben-Cohen <ohad@...ery.com>
Subject: Re: [PATCHv22 13/16] drivers: add Contiguous Memory Allocator

Hi,

On Fri, 17 Feb 2012, Marek Szyprowski wrote:
> +/**
> + * dma_release_from_contiguous() - release allocated pages
> + * @dev:   Pointer to device for which the pages were allocated.
> + * @pages: Allocated pages.
> + * @count: Number of allocated pages.
> + *
> + * This function releases memory allocated by dma_alloc_from_contiguous().
> + * It returns false when provided pages do not belong to contiguous area and
> + * true otherwise.
> + */
> +bool dma_release_from_contiguous(struct device *dev, struct page *pages,
> +				 int count)
> +{
> +	struct cma *cma = dev_get_cma_area(dev);
> +	unsigned long pfn;
> +
> +	if (!cma || !pages)
> +		return false;
> +
> +	pr_debug("%s(page %p)\n", __func__, (void *)pages);
> +
> +	pfn = page_to_pfn(pages);
> +
> +	if (pfn < cma->base_pfn || pfn >= cma->base_pfn + cma->count)
> +		return false;
> +
> +	VM_BUG_ON(pfn + count > cma->base_pfn);

Are you sure the VM_BUG_ON() condition is correct here?

> +	mutex_lock(&cma_mutex);
> +	bitmap_clear(cma->bitmap, pfn - cma->base_pfn, count);
> +	free_contig_range(pfn, count);
> +	mutex_unlock(&cma_mutex);
> +
> +	return true;
> +}

A.
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