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Subject[PATCH v1 6/8] dmaengine: enhance network subsystem to support DMA device hotplug
Date
Enhance network subsystem to correctly update DMA channel reference counts,
so it won't break DMA device hotplug logic.

Signed-off-by: Jiang Liu <liuj97@gmail.com>
---
include/net/netdma.h | 26 ++++++++++++++++++++++++++
net/ipv4/tcp.c | 10 +++-------
net/ipv4/tcp_input.c | 5 +----
net/ipv4/tcp_ipv4.c | 4 +---
net/ipv6/tcp_ipv6.c | 4 +---
5 files changed, 32 insertions(+), 17 deletions(-)
diff --git a/include/net/netdma.h b/include/net/netdma.h
index 8ba8ce2..6d71724 100644
--- a/include/net/netdma.h
+++ b/include/net/netdma.h
@@ -24,6 +24,32 @@
#include <linux/dmaengine.h>
#include <linux/skbuff.h>

+static inline bool
+net_dma_capable(void)
+{
+ struct dma_chan *chan = net_dma_find_channel();
+ dma_put_channel(chan);
+
+ return !!chan;
+}
+
+static inline struct dma_chan *
+net_dma_get_channel(struct tcp_sock *tp)
+{
+ if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list)
+ tp->ucopy.dma_chan = net_dma_find_channel();
+ return tp->ucopy.dma_chan;
+}
+
+static inline void
+net_dma_put_channel(struct tcp_sock *tp)
+{
+ if (tp->ucopy.dma_chan) {
+ dma_put_channel(tp->ucopy.dma_chan);
+ tp->ucopy.dma_chan = NULL;
+ }
+}
+
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);
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 8bb6ade..aea4032 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1451,8 +1451,7 @@ int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
available = TCP_SKB_CB(skb)->seq + skb->len - (*seq);
if ((available < target) &&
(len > sysctl_tcp_dma_copybreak) && !(flags & MSG_PEEK) &&
- !sysctl_tcp_low_latency &&
- net_dma_find_channel()) {
+ !sysctl_tcp_low_latency && net_dma_capable()) {
preempt_enable_no_resched();
tp->ucopy.pinned_list =
dma_pin_iovec_pages(msg->msg_iov, len);
@@ -1666,10 +1665,7 @@ do_prequeue:

if (!(flags & MSG_TRUNC)) {
#ifdef CONFIG_NET_DMA
- if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list)
- tp->ucopy.dma_chan = net_dma_find_channel();
-
- if (tp->ucopy.dma_chan) {
+ if (net_dma_get_channel(tp)) {
tp->ucopy.dma_cookie = dma_skb_copy_datagram_iovec(
tp->ucopy.dma_chan, skb, offset,
msg->msg_iov, used,
@@ -1758,7 +1754,7 @@ skip_copy:

#ifdef CONFIG_NET_DMA
tcp_service_net_dma(sk, true); /* Wait for queue to drain */
- tp->ucopy.dma_chan = NULL;
+ net_dma_put_channel(tp);

if (tp->ucopy.pinned_list) {
dma_unpin_iovec_pages(tp->ucopy.pinned_list);
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 9944c1d..3878916 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5227,10 +5227,7 @@ static int tcp_dma_try_early_copy(struct sock *sk, struct sk_buff *skb,
if (tp->ucopy.wakeup)
return 0;

- if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list)
- tp->ucopy.dma_chan = net_dma_find_channel();
-
- if (tp->ucopy.dma_chan && skb_csum_unnecessary(skb)) {
+ if (net_dma_get_channel(tp) && skb_csum_unnecessary(skb)) {

dma_cookie = dma_skb_copy_datagram_iovec(tp->ucopy.dma_chan,
skb, hlen,
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 0cb86ce..90ea1c0 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1729,9 +1729,7 @@ process:
if (!sock_owned_by_user(sk)) {
#ifdef CONFIG_NET_DMA
struct tcp_sock *tp = tcp_sk(sk);
- if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list)
- tp->ucopy.dma_chan = net_dma_find_channel();
- if (tp->ucopy.dma_chan)
+ if (net_dma_get_channel(tp))
ret = tcp_v4_do_rcv(sk, skb);
else
#endif
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 86cfe60..fb81bbd 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1644,9 +1644,7 @@ process:
if (!sock_owned_by_user(sk)) {
#ifdef CONFIG_NET_DMA
struct tcp_sock *tp = tcp_sk(sk);
- if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list)
- tp->ucopy.dma_chan = net_dma_find_channel();
- if (tp->ucopy.dma_chan)
+ if (net_dma_get_channel(tp))
ret = tcp_v6_do_rcv(sk, skb);
else
#endif
--
1.7.5.4


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