On Fri, Dec 09, 2016 at 02:18:01PM +0100, Jason A. Donenfeld wrote: > Hi Herbert, > > The scatterwalk_map_and_copy function copies ordinary buffers to and > from scatterlists. These buffers can, of course, be on the stack, and > this remains the most popular use of this function -- getting info > between stack buffers and DMA regions. It's mostly used for adding or > checking MACs, in the majority of call sites. Its implementation is > relatively straightforward. It maps the DMA region(s) to a vaddr, and > then just calls vanilla memcpy. Pretty uncontroversial. > > However, around ~4.1 an optimization was added to prevent copying when > unnecessary (when the src and dst are the same). The optimization > looks like this: > > if (sg_page(sg) == virt_to_page(buf) && > sg->offset == offset_in_page(buf)) > return; > > There are two problems with this: This code no longer exists in the current tree. Cheers, -- Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
