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-rw-r--r--lib/scatterlist.c95
1 files changed, 68 insertions, 27 deletions
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index be7b4dd6b68d..7c1c55f7daaa 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -370,41 +370,49 @@ int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask)
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
+ * __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)
+ * @max_segment: Maximum size of a scatterlist node in bytes (page aligned)
+ * @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.
+ * ranges of the pages are squashed into a single scatterlist node up to the
+ * maximum size specified in @max_segment. An 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)
+int __sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
+ unsigned int n_pages, unsigned int offset,
+ unsigned long size, unsigned int max_segment,
+ gfp_t gfp_mask)
{
- unsigned int chunks;
- unsigned int i;
- unsigned int cur_page;
+ unsigned int chunks, cur_page, seg_len, i;
int ret;
struct scatterlist *s;
+ if (WARN_ON(!max_segment || offset_in_page(max_segment)))
+ return -EINVAL;
+
/* 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;
+ seg_len = 0;
+ for (i = 1; i < n_pages; i++) {
+ seg_len += PAGE_SIZE;
+ if (seg_len >= max_segment ||
+ page_to_pfn(pages[i]) != page_to_pfn(pages[i - 1]) + 1) {
+ chunks++;
+ seg_len = 0;
+ }
+ }
ret = sg_alloc_table(sgt, chunks, gfp_mask);
if (unlikely(ret))
@@ -413,17 +421,21 @@ int sg_alloc_table_from_pages(struct sg_table *sgt,
/* 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;
+ unsigned int j, chunk_size;
/* look for the end of the current chunk */
- for (j = cur_page + 1; j < n_pages; ++j)
- if (page_to_pfn(pages[j]) !=
+ seg_len = 0;
+ for (j = cur_page + 1; j < n_pages; j++) {
+ seg_len += PAGE_SIZE;
+ if (seg_len >= max_segment ||
+ 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);
+ sg_set_page(s, pages[cur_page],
+ min_t(unsigned long, size, chunk_size), offset);
size -= chunk_size;
offset = 0;
cur_page = j;
@@ -431,6 +443,35 @@ int sg_alloc_table_from_pages(struct sg_table *sgt,
return 0;
}
+EXPORT_SYMBOL(__sg_alloc_table_from_pages);
+
+/**
+ * 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 int offset,
+ unsigned long size, gfp_t gfp_mask)
+{
+ return __sg_alloc_table_from_pages(sgt, pages, n_pages, offset, size,
+ SCATTERLIST_MAX_SEGMENT, gfp_mask);
+}
EXPORT_SYMBOL(sg_alloc_table_from_pages);
void __sg_page_iter_start(struct sg_page_iter *piter,