Re: Regression bisected to "crypto: af_alg: Convert af_alg_sendpage() to use MSG_SPLICE_PAGES"

[David Howells <dhowells@redhat.com>]

The problem is caused by this bit in af_alg_sendmsg():

		/* use the existing memory in an allocated page */
		if (ctx->merge) {
			sgl = list_entry(ctx->tsgl_list.prev,
					 struct af_alg_tsgl, list);
			sg = sgl->sg + sgl->cur - 1;
			len = min_t(size_t, len,
				    PAGE_SIZE - sg->offset - sg->length);

			err = memcpy_from_msg(page_address(sg_page(sg)) +
					      sg->offset + sg->length,
					      msg, len);
			if (err)
				goto unlock;

			sg->length += len;
			ctx->merge = (sg->offset + sg->length) &
				     (PAGE_SIZE - 1);

			ctx->used += len;
			copied += len;
			size -= len;
			continue;
		}

it doesn't exist in the old af_alg_sendpage() code.  It merges data supplied
by sendmsg() into the last page in the list if there's space.  So we need a
flag to keep track of whether the last page is appendable-to or not.

David