[I/OAT]: Utility functions for offloading sk_buff to iovec copies

Provides for pinning user space pages in memory, copying to iovecs,
and copying from sk_buffs including fragmented and chained sk_buffs.

Signed-off-by: Chris Leech <christopher.leech@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 127 insertions, 0 deletions

diff --git a/net/core/user_dma.c b/net/core/user_dma.c
new file mode 100644
index 000000000000..9eee91bcbf3f
--- /dev/null
+++ b/net/core/user_dma.c
@@ -0,0 +1,127 @@
+/*
+ * Copyright(c) 2004 - 2006 Intel Corporation. All rights reserved.
+ * Portions based on net/core/datagram.c and copyrighted by their authors.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc., 59
+ * Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+ *
+ * The full GNU General Public License is included in this distribution in the
+ * file called COPYING.
+ */
+
+/*
+ * This code allows the net stack to make use of a DMA engine for
+ * skb to iovec copies.
+ */
+
+#include <linux/dmaengine.h>
+#include <linux/socket.h>
+#include <linux/rtnetlink.h> /* for BUG_TRAP */
+#include <net/tcp.h>
+
+/**
+ *      dma_skb_copy_datagram_iovec - Copy a datagram to an iovec.
+ *      @skb - buffer to copy
+ *      @offset - offset in the buffer to start copying from
+ *      @iovec - io vector to copy to
+ *      @len - amount of data to copy from buffer to iovec
+ *      @pinned_list - locked iovec buffer data
+ *
+ *      Note: the iovec is modified during the copy.
+ */
+int dma_skb_copy_datagram_iovec(struct dma_chan *chan,
+                        struct sk_buff *skb, int offset, struct iovec *to,
+                        size_t len, struct dma_pinned_list *pinned_list)
+{
+        int start = skb_headlen(skb);
+        int i, copy = start - offset;
+        dma_cookie_t cookie = 0;
+
+        /* Copy header. */
+        if (copy > 0) {
+                if (copy > len)
+                        copy = len;
+                cookie = dma_memcpy_to_iovec(chan, to, pinned_list,
+                                            skb->data + offset, copy);
+                if (cookie < 0)
+                        goto fault;
+                len -= copy;
+                if (len == 0)
+                        goto end;
+                offset += copy;
+        }
+
+        /* Copy paged appendix. Hmm... why does this look so complicated? */
+        for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
+                int end;
+
+                BUG_TRAP(start <= offset + len);
+
+                end = start + skb_shinfo(skb)->frags[i].size;
+                copy = end - offset;
+                if ((copy = end - offset) > 0) {
+                        skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
+                        struct page *page = frag->page;
+
+                        if (copy > len)
+                                copy = len;
+
+                        cookie = dma_memcpy_pg_to_iovec(chan, to, pinned_list, page,
+                                        frag->page_offset + offset - start, copy);
+                        if (cookie < 0)
+                                goto fault;
+                        len -= copy;
+                        if (len == 0)
+                                goto end;
+                        offset += copy;
+                }
+                start = end;
+        }
+
+        if (skb_shinfo(skb)->frag_list) {
+                struct sk_buff *list = skb_shinfo(skb)->frag_list;
+
+                for (; list; list = list->next) {
+                        int end;
+
+                        BUG_TRAP(start <= offset + len);
+
+                        end = start + list->len;
+                        copy = end - offset;
+                        if (copy > 0) {
+                                if (copy > len)
+                                        copy = len;
+                                cookie = dma_skb_copy_datagram_iovec(chan, list,
+                                                offset - start, to, copy,
+                                                pinned_list);
+                                if (cookie < 0)
+                                        goto fault;
+                                len -= copy;
+                                if (len == 0)
+                                        goto end;
+                                offset += copy;
+                        }
+                        start = end;
+                }
+        }
+
+end:
+        if (!len) {
+                skb->dma_cookie = cookie;
+                return cookie;
+        }
+
+fault:
+        return -EFAULT;
+}