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EXPORT_SYMBOL(sg_alloc_table);

/**

 * sg_alloc_table_from_pages - Allocate and initialize an sg table from

 *			       an array of pages

 * @sgt:	The sg table header to use

 * @pages:	Pointer to an array of page pointers

 * @n_pages:	Number of pages in the pages array

 * @offset:     Offset from start of the first page to the start of a buffer

 * @size:       Number of valid bytes in the buffer (after offset)

 * @gfp_mask:	GFP allocation mask

 *

 *  Description:

 *    Allocate and initialize an sg table from a list of pages. Contiguous

 *    ranges of the pages are squashed into a single scatterlist node. A user

 *    may provide an offset at a start and a size of valid data in a buffer

 *    specified by the page array. The returned sg table is released by

 *    sg_free_table.

 *

 * Returns:

 *   0 on success, negative error on failure

 */

int sg_alloc_table_from_pages(struct sg_table *sgt,

	struct page **pages, unsigned int n_pages,

	unsigned long offset, unsigned long size,

	gfp_t gfp_mask)

{

	unsigned int chunks;

	unsigned int i;

	unsigned int cur_page;

	int ret;

	struct scatterlist *s;

	/* compute number of contiguous chunks */

	chunks = 1;

	for (i = 1; i < n_pages; ++i)

		if (page_to_pfn(pages[i]) != page_to_pfn(pages[i - 1]) + 1)

			++chunks;

	ret = sg_alloc_table(sgt, chunks, gfp_mask);

	if (unlikely(ret))

		return ret;

	/* merging chunks and putting them into the scatterlist */

	cur_page = 0;

	for_each_sg(sgt->sgl, s, sgt->orig_nents, i) {

		unsigned long chunk_size;

		unsigned int j;

		/* look for the end of the current chunk */

		for (j = cur_page + 1; j < n_pages; ++j)

			if (page_to_pfn(pages[j]) !=

			    page_to_pfn(pages[j - 1]) + 1)

				break;

		chunk_size = ((j - cur_page) << PAGE_SHIFT) - offset;

		sg_set_page(s, pages[cur_page], min(size, chunk_size), offset);

		size -= chunk_size;

		offset = 0;

		cur_page = j;

	}