On 7/26/07, David Miller <[EMAIL PROTECTED]> wrote:
> From: Shannon Nelson <[EMAIL PROTECTED]>
> Date: Tue, 24 Jul 2007 17:36:06 -0700
>
> > (repost - original eaten by vger?)
> >
> > Al Viro pointed out that dma_memcpy_to_kernel_iovec() really was
> > unreachable and thus unused. The code originally was there to support
> > in-kernel dma needs, but since it remains unused, we'll pull it out.
> >
> > Signed-off-by: Shannon Nelson <[EMAIL PROTECTED]>
>
> Applied, thanks Shannon.
NET_DMA on kernel buffer is pretty useful in ndb, iSCSI target and
initiators which uses kernel buffer to receive data. Are there any
other issues with dma-memcpy on kernel buffers, if not then following
patch makes dma_memcpy_to_kernel_iovec() reachable from tcp_recvmsg.
I tested this patch and it work fine with unh iSCSI target.
comments?
--pravin.
Index: linux-2.6.23-rc1/net/ipv4/tcp.c
===================================================================
--- linux-2.6.23-rc1.orig/net/ipv4/tcp.c 2007-07-23 02:11:00.000000000
+0530
+++ linux-2.6.23-rc1/net/ipv4/tcp.c 2007-07-30 17:43:51.000000000 +0530
@@ -1115,7 +1115,7 @@
int target; /* Read at least this many bytes */
long timeo;
struct task_struct *user_recv = NULL;
- int copied_early = 0;
+ int copied_early = 0, kernel_dma = 0;
struct sk_buff *skb;
lock_sock(sk);
@@ -1154,6 +1154,9 @@
!sysctl_tcp_low_latency &&
__get_cpu_var(softnet_data).net_dma) {
preempt_enable_no_resched();
+ if (segment_eq(get_fs(), KERNEL_DS))
+ kernel_dma = 1;
+ else
tp->ucopy.pinned_list =
dma_pin_iovec_pages(msg->msg_iov, len);
} else {
@@ -1362,7 +1365,7 @@
if (!(flags & MSG_TRUNC)) {
#ifdef CONFIG_NET_DMA
- if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list)
+ if (!tp->ucopy.dma_chan && (kernel_dma ||
tp->ucopy.pinned_list))
tp->ucopy.dma_chan = get_softnet_dma();
if (tp->ucopy.dma_chan) {
> -
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