Hi,

On 03/30/2016 09:09 PM, Boris BREZILLON wrote:

[...]

+int sg_alloc_table_from_buf(struct sg_table *sgt, const void *buf, size_t len,
+			    const struct sg_constraints *constraints,
+			    gfp_t gfp_mask)
+{
+	struct sg_constraints cons = { };
+	size_t remaining, chunk_len;
+	const void *sg_buf;
+	int i, ret;
+
+	if (constraints)
+		cons = *constraints;
+
+	ret = sg_check_constraints(&cons, buf, len);
+	if (ret)
+		return ret;
+
+	sg_buf = buf;
+	remaining = len;
+	i = 0;
+	sg_for_each_chunk_in_buf(sg_buf, remaining, chunk_len, &cons)
+		i++;
+
+	ret = sg_alloc_table(sgt, i, gfp_mask);
+	if (ret)
+		return ret;
+
+	sg_buf = buf;
+	remaining = len;
+	i = 0;
+	sg_for_each_chunk_in_buf(sg_buf, remaining, chunk_len, &cons) {
+		if (is_vmalloc_addr(sg_buf)) {
+			struct page *vm_page;
+
+			vm_page = vmalloc_to_page(sg_buf);
+			if (!vm_page) {
+				ret = -ENOMEM;
+				goto err_free_table;
+			}
+
+			sg_set_page(&sgt->sgl[i], vm_page, chunk_len,
+				    offset_in_page(sg_buf));
+		} else {
+			sg_set_buf(&sgt->sgl[i], sg_buf, chunk_len);
+		}
+

If the buf address is in PKMAP_BASE - PAGE_OFFSET-1 region (I have
observed that JFFS2 FS provides buffers in above region to MTD layer),
if CONFIG_DEBUG_SG is set then sg_set_buf() will throw a BUG_ON() as
virt_addr_is_valid() will return false. Is there a sane way to handle
buffers of PKMAP_BASE region with sg_*  APIs?
Or, is the function sg_alloc_table_from_buf() not to be used with such
buffers?


-- 
Regards
Vignesh